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PRECICE intramedullary limb

lengthening system

Expert Rev. Med. Devices Early online, 1–19 (2015)

Dror Paley

The Paley Advanced Limb Lengthening

Institute at St. Mary’s Medical Center,

901 45th Street, Kimmel Building,

West Palm Beach, FL 33407, USA

Tel.: +1 561 844 5244

Fax: +1 561 844 5245

drorpaley@gmail.com

The PRECICE



Intramedullary Limb Lengthening System (Ellipse Technologies Inc., CA, USA) is

a remotely controlled, magnetically driven, implantable limb lengthening intramedullary nail

system. It has both CE mark and US FDA clearance for its first- (2011) and second-generation

(2013) implants. It is indicated for the treatment of limb length discrepancy and short stature.

It has been used worldwide in over 1000 cases. Its reported and published results in over

250 cases has been excellent with less pain and lower complication rates than with external

fixation methods or previous implantable nail systems.

KEYWORDS:congenital femoral deficiency .distraction osteogenesis .fibular hemimelia .intramedullary nails .leg

length discrepancy .limb length discrepancy .magnet .noninvasive .PRECICE



Ellipse Technologies (Irvine, CA, USA) devel-

oped the PRECICE nail with a team of sur-

geons (including myself) headed by Dr. Stuart

Green. They used the same mechanism that

they had developed for their spinal growing

rod called ‘the MAGEC System’[1]. There is a

magnetic metal spindle that is connected to a

series of gears (FIGURE 1). The gears are con-

nected to a coupling, which is connected to a

threaded drive shaft. The mechanism is acti-

vated by an external remote control (ERC)

device (FIGURE 2A). The ERC employs two

motor-driven rotating magnets to magnetically

couple to and rotate the magnetic metal

spindle (FIGURE 2B). Facing the ERC in one

direction causes the nail to lengthen, while fac-

ing it the other direction would go in the

reverse (shortening) direction. PRECICE is the

second FDA-cleared implantable lengthening

nail device (July 2011) and the first one to

have bidirectional control (lengthening and

shortening). I had the privilege of implanting

the first PRECICE nail in the USA on

1 December 2011.

The Ilizarov procedure remained the best

option for limb lengthening until the intro-

duction of these new nails in the 1990s. It

was thought that with this new technology

the complications related to limb lengthening

would be greatly diminished. Intramedullary

nail techniques are not without complica-

tions, which may include nonunions, nerve

injuries, nail fractures, joint contractures and

other serious complications [2–10]. External

fixation approaches to limb lengthening

remain the gold standard. Experience with

implantable limb lengthening have made evi-

dent that the complications of limb lengthen-

ing can be divided into two categories, device

related and distraction related. The device-

related complications are very different for

external versus internal lengthening devices.

The high complication rates related to pin

tract infections, joint stiffness and contrac-

tures due to tethering of the muscles by the

pins, and large pin tract scars, do not occur

with implantable devices. The complications

related to distraction are similar between

external and internal lengthening methods.

These complications include premature con-

solidation, delayed and failed bone formation,

nerve stretch injury, muscle contractures and

joint subluxation. The reduced device compli-

cations and even some reduced distraction

complications (e.g., axial deviation) have

made the switch to implantable devices very

attractive and have created a market for these

technologically advanced devices.

Body of review

Overview of the market

The indications for limb lengthening are for

the treatment of limb length discrepancy of

the lower or upper limb and for stature

lengthening. The indications for leg lengthen-

ing are for the treatment of leg length dis-

crepancy or short stature. Unilateral limb

lengthening is used to equalize limb length in

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Device Profile

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the treatment of limb length discrepancy. Bilateral limb length-

ening is used for increasing height and restoring body propor-

tions in patients with dysplasias (e.g., achondroplasia and

hypochondroplasia) and other genetic conditions (e.g., Turner’s

syndrome), for the treatment of height dysphoria in patients

with short stature and for increasing height for cosmetic

reasons.

Leg length discrepancy can be due to congenital, develop-

mental or posttraumatic causes.

Developmental or posttraumatic causes may include growth

plate arrest, malunion, nonunion, bone loss from open frac-

tures, osteomyelitis or tumor. Minor leg length discrepancy is

prevalent, with 23% of the general population possessing a dis-

crepancy of at least 1 cm. The prevalence of leg length discrep-

ancy where a corrective device is required is approximately 1 in

1000. More severe discrepancies such as congenital femoral

deficiency and fibular hemimelia are rare and complex congeni-

tal disorders of the lower limb with an incidence of approxi-

mately one in 50,000 live births for congenital femoral

deficiency [11–13] and between 7.4 and 20 per million live births

for fibular hemimelia [14–16].

Short stature is a common feature of most dysplasias and

musculoskeletal syndromes. Achondroplasia is the most com-

mon dysplasia and occurs in 1:40,000 births. Constitutional

short stature is defined as under the 5th percentile for height

(5% of the population). Height dysphoria is a well-known con-

dition also referred to as height neurosis. It is a very common

condition although no accurate statistics exist as to its preva-

lence. Most patients with height dysphoria are over the 5th

percentile in height. Height dysphoria represents a body image

anxiety disorder, which is generally unresponsive to psychother-

apy. Lengthening for height dysphoria is considered cosmetic

or aesthetic lengthening.

Limb lengthening for limb length discrepancy is a well-

accepted indication for treatment. Nevertheless, its market is

relatively small. Similarly, stature lengthening for the treatment

of dysplasias, although more controversial, is also a well-

accepted indication for treatment, again with a relatively small

market.

Stature lengthening for cosmetic reasons is a very controver-

sial indication for treatment. Nevertheless, there is a growing

demand for such treatment by the population. There are

numerous social network websites that serve to voice the inter-

est and demand for such treatment. As such it is a huge

Figure 1. Photograph of tibial nails: PRECICE 1 (P1, left)

and PRECICE 2 (P2, right). Note the three welds in P1 and no

welds in P2.

A

Flux lines

Rotation

S

N

N

S

SN

B

Figure 2. External remote control. (A) Photograph of external remote control device being applied to the thigh for femur lengthening.

(B) Illustration of how rotation of the 2 external remote control magnets (big circles) cause the nail magnet (small circle) to rotate

through their magnetic fields.

Device Profile Paley

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untapped market. A small but growing number of cosmetic

stature lengthening centers have sprung up around the world

to service this demand.

The concept of cosmetic stature lengthening is foreign to

most orthopedic surgeons. Unlike our plastic surgery col-

leagues, we have no tradition of cosmetic or aesthetic surgery.

Orthopedic surgery is founded on the principles of treatment

of pain, disability and deformity. We use our surgery to treat

or prevent pain and disability. Our surgery is funded by reim-

bursement by third-party payers since it is not considered

cosmetic.

With the decreasing reimbursement for surgery, the allure of

a cash-paying cosmetic surgery practice will attract many ortho-

pedic surgeons in the near future. The cosmetic market may

become the largest indication for implantable limb lengthening.

Until now the external fixator has been the gold standard for

limb lengthening. Most orthopedic surgeons shy away from

external fixation and as such it has become the realm of a small

group of orthopedic specialists. The external fixator has also

kept patients away from this treatment. Now that the surgery is

both simpler for the surgeon and less complicated for the

patients, we can anticipate an increase in the number of sur-

geons who take up limb lengthening and patients who are keen

to have it done. The number of implants used for the treatment

of leg length discrepancy and dysplasias will, in the future, be

far outnumbered by the number used for cosmetic stature

lengthening. Needless to say each cosmetic case represents two

implants compared to one for each leg length difference. While

limb length discrepancy (LLD) patients often have staged

lengthening over the course of their childhood, stature patients

often have a second pair of lengthening for their other segments

(e.g., two femurs and then two tibias) still outnumbering the

LLD indications. Unfortunately, the ease of application of the

device is misleading. While the surgery is relatively easy and can

be carried out by most orthopedic surgeons, the postoperative

follow-up and the learning curve for the treatment of

distraction-related problems and complications is quite steep.

Most orthopedic surgeons are not knowledgeable in the postoper-

ative management of the limb lengthening patient. As such we

may anticipate a large number of complications created by sur-

geons knowledgeable in the insertion of nails but unprepared for

the management of the limb lengthening process. Since the use

for stature is so potentially lucrative, this sector of the market may

grow precipitously but may also be subject to significant abuse.

External fixation defines the existing market for limb lengthen-

ing. Implantable lengthening nails are indicated for the same

market currently occupied by limb lengthening external fixators.

The indications for their use are the same: limb length discrep-

ancy and short stature. Implantable nails are currently limited by

anatomy, length, diameter and limited ability to correct defor-

mity especially in children and the short bones of dysplastic

patients. In the USA, the only FDA-approved device was intra-

medullary skeletal distractor (ISKD) (Orthofix Inc, Lewisville,

TX, USA). It was introduced to the market in 2001 and was

finally withdrawn from the US market in 2011. In Europe,

Fitbone, Phenix and Albizzia all on very limited releases were the

only other alternatives. Phenix is now off the market due to the

untimely death of Arnaud Soubieran its inventor. It is due to

resurface (perhaps in 2015) as a product called Novus from

Smith and Nephew Orthopedics (Memphis, TN, USA). Fitbone

(Wittenstein, Igersheim, Germany) is distributed to a small num-

ber of surgeons under the direct approval by Dr. Rainer Baum-

gart. The rationale for approval is supposedly based on

experience and limited by number of centers per country. This

decision seems very arbitrary and as a case in point, I was unable

to receive approval by Dr. Baumgart for its use. Fitbone also has

the distinction of being the most expensive implantable nail. The

modified Albizzia, referred to as the Betz Bone, and the Guichet

nail are only used by these two namesake surgeons and are not

available for commercial distribution. Thus, PRECICE intro-

duced both in the USA and internationally in 2011 has become

the only commercially available remote controlled implantable

limb lengthening device.

Introduction to the device

Device description

PRECICE is a telescopic intramedullary locking nail. The

mechanism has a rare earth magnetic metal spindle that is con-

nected to a series of three planetary gear clusters (FIGURE 3). Each

gear cluster produces a reduction of 1/4 for a total reduction of

1/64 between the magnet and the drive screw. There is a cou-

pling between the gears and the drive screw with a safeguard

Magnet

Gear box

Lead screw

Figure 3. Radiograph of the actuator of PRECICE showing

its different parts. The magnet is connected to a series of three

gears (gear box) that are connected to a coupling which links to

the lead screw. The threaded drive shaft (lead screw) lengthens

or shortens the smaller diameter tube of the nail relative to the

bigger diameter tube.

PRECICE intramedullary limb lengthening system Device Profile

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(like a clutch) built in to avoid breakage in the face of extreme

torque resistance. The mechanism (actuator) is activated by an

ERC device (FIGURE 2A). The ERC employs two motor-driven

rotating magnets to magnetically couple to and rotate the mag-

netic metal spindle (FIGURE 2B). The ERC performs 30 revolutions

per minute. It takes 7 min and 210 revolutions to achieve

1 mm of lengthening. Facing the ERC in one direction causes

the nail to lengthen, while facing it the other direction would

go in the reverse (shortening) direction.

PRECICE nail & locking screws

The first generation of the Ellipse PRECICE Limb Lengthen-

ing System is composed of the PRECICE intramedullary nail,

locking screws, implantation tools and accessories, and an

ERC. The implantable nail is supplied sterile by gradiation

and is available in tibia and femur models with diameters of

10.7 and 12.5 mm, stroke length of 65 mm, overall starting

lengths of 230–355 mm, and distal screw hole patterns to

accommodate a variety of patient anatomies. Likewise, the

locking screws are available in two different diameters and a

variety of lengths from 20 to 75 mm in 5 mm increments.

The first-generation PRECICE (PRECICE 1) is modular

such that the intramedullary limb lengthening actuator compo-

nent had to be assembled in surgery to an extension rod of dif-

ferent length and anatomical shape. The length of the

intramedullary limb lengthening actuator is fixed, while the

extension rods varied in length. The intramedullary limb

lengthening actuator including its rare earth magnet, telescop-

ing lead screw/nut assembly and gearing were housed in a rod

segment that was welded above and below to the rest of the

nail housing. In total, there were three welds in this unit and

one connection to the extension rod via set screw. Extension

rods, locking screws and reusable accessories are supplied non-

sterile and must be sterilized prior to use. The second-

generation Ellipse PRECICE 2 Limb Lengthening System

released in November 2013 is composed of the PRECICE

intramedullary nail, locking screws, implantation tools and

accessories, and an ERC. The modified implantable nail is

supplied sterile by gradiation and is available in tibia and

femur models with diameters of 8.5, 10.7 and 12.5 mm, stroke

lengths of 50 and 80 mm, overall starting lengths of

195–365 mm, and distal screw hole patterns to accommodate

a variety of patient anatomies. Likewise, the PRECICE locking

screws are available in different diameters and a variety of

lengths ranging from 20 to 75 mm. The PRECICE locking

screws and implantation instruments and accessories are sup-

plied nonsterile and must be sterilized prior to use. The PRE-

CICE nail is surgically placed in the intramedullary canal of

the femur or tibia. The femur models offer piriformis, trochan-

teric and retrograde entry models. The metal in contact with

the patient’s body fluids and bone is composed of medical

grade titanium alloy (Ti-6Al-4V). The rare earth magnet and

gears are sealed from body fluid contact.

External remote control

The ERC provides a noninvasive method for precisely distract-

ing the nail at defined intervals. The ERC includes two perma-

nent magnets that are rotated by a motor which is

electronically powered. When the ERC magnets are rotated in

proximity (less than 5.5 cm) to the PRECICE nail, the rare

earth magnet in the nail turns and the distracting rod either

lengthens or shortens the intramedullary nail depending on the

direction of rotation of the ERC magnets. The first use of the

ERC is in the operating room to test the functionality of the

nail mechanism. A 1-mm test distraction is performed and con-

firmed radiographically. Postoperatively after a latency period

ranging from 0 to 7 days, the nail is lengthened daily by the

patient (or their caregivers) according to the daily prescription

set by the treating physician (FIGURE 4).

Implant technique (PRECICE 2)

Surgical technique femur

Step 1: The patient is positioned supine on a radiolucent oper-

ating table. A radiolucent bump (usually a folded towel or

sheet) is placed underneath the ischium on the operative side.

This allows good visualization of the hip on both antero-poste-

rior (AP) and cross table lateral views.

Step 2: Using the image intensifier (fluoroscopy), the tip of

the level of the greater trochanter is marked on the skin. Know-

ing the length of the nail to be used for the surgery, a ruler is

used to mark the distal end of the nail. For retrograde nailing,

measure from 1 cm proximal to the intercondylar notch.

Step 3: The level of the osteotomy is determined by know-

ing the amount of distraction planned. One must plan to end

up with the larger diameter of the nail always engaged on both

sides of the distraction gap at the end of lengthening. Assuming

one wants to have 2 cm of the larger diameter of the nail

engaged, then add 2 cm plus 3 cm of the smaller diameter

nail, which is exposed plus the distraction amount. This total

measured from the distal end of the nail represents the level of

the desired osteotomy that will leave at least 2 cm of the larger

diameter of the nail always engaged in cortical bone on the

opposite side of the distraction gap.

0 mm 1 mm 2 mm

Figure 4. Radiograph before distraction (0 mm) and after

distraction of 1 and 2 mm.

Device Profile Paley

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Step 4: Make a 1-cm incision laterally at the level of the

osteotomy. Drill holes using a 4.8-mm drill bit. I prefer one

entrance and three exit holes, anteromedial, posteromedial and

medial. Then make two more drill holes anterolateral and pos-

terolateral at the level of the other holes. These six holes will serve

to vent the canal from fat emboli and to allow the reamings that

extrude through the holes to auto-bonegraft the osteotomy site.

Step 5: Insert a Steinmann pin into the piriformis fossa for

adults or adolescents with closed growth plates. For patients

with an open proximal femoral growth plate, insert the Stein-

mann pin into the tip of the greater trochanter. For retrograde

nailing, insert the Steinmann pin at the center of the intercon-

dylar notch on the AP and at the distal end of Blumensaat’s

line on the lateral.

Step 6: Expand the starting point with a 10-mm anterior

cruciate ligament reamer.

Step 7: Insert a beaded guide rod down the femur.

Step 8: Ream in 1-mm increments until there is chatter and

then in 0.5-mm increments. Ream to 10.5 mm for the

8.5-mm nail, 12.5 mm for the 10.7-mm nail and to 14.5 mm

for the 12.5-mm nail. For the 8.5-mm nail, ream the upper

part of the bone to 11 mm. For trochanteric entry, it may be

helpful to ream an extra millimeter in the upper part of the

bone to allow lower resistance passage of the nail as it goes

around the bend.

Step 9: Prepare the nail for insertion. With PRECICE 1,

choose and assemble the insertion end type (trochanteric, piri-

formis, retrograde, tibial) and lengths. The mechanism comes

in one length, while the final nail length depends on the length

of the insertion end chosen. With the new PRECICE 2, the

nail is not modular and one must choose the length of the

entire nail in advance.

Step 10: Apply the proximal targeting device and test its

alignment to the screw holes by inserting the drill guides and

drill bits.

Step 11: Place the nail under the beam of the image intensi-

fier to confirm that the mechanism is not predistracted. Save

this image for reference.

Step 12: Remove the beaded guide wire used for reaming as

the nail is not cannulated. Insert the nail into the canal up to

the level of the planned osteotomy (drill holes).

Step 13: Have one assistant lift the foot off the table. Have

the other assistant lift the proximal end of the nail using the

insertion guide. The two assistants are applying an extension

moment to the femur to prevent displacement of the femur

during the osteotomy.

Step 14: Use a sharp 6–8 mm osteotome to osteotomize the

femur through the 1-cm lateral incision. The femur will easily

break through the six drill holes. Listen for the break and once

it occurs withdraw the osteotome. Test that the femur is frac-

tured by moving the femur gently into varus and valgus and

watching it move using live fluoroscopy. Maintain the exten-

sion moment throughout this test.

Step 15: Once the break is confirmed to be complete,

advance the nail by gently hammering on the impactor until

the nail crosses the osteotomy line into the distal (antegrade

nailing) or proximal (retrograde nailing) segment of the femur.

The extension moment is no longer needed to stabilize the

femur. Advance the nail until the upper end is at the level of

the base of the piriformis fossa or just inside the greater tro-

chanter for piriformis and trochanteric nails, respectively. For

retrograde nails, make sure that the end of the nail is inside the

femur at the intercondylar notch.

Step 16: Lock the nail proximally (antegrade) and distally

(retrograde) with two screws using the locking guide. For distal

locking screws (antegrade) and proximal locking screws (retro-

grade), my personal technique preference is to insert a long

1.8-mm wire into the locking hole, followed by a 3.5-mm can-

nulated drill for the 8.5-mm nail, 3.8-mm cannulated drill for

10.7-mm nails and a 4.8-mm cannulated drill for the 12.5-mm

nail. In the 12.5-mm nail, overdrill with a solid 5-mm drill bit

and in the 10.7-mm nail overdrill with a solid 4-mm drill bit.

Step 17: Lock the nail distally with two lateral-medial

screws. Do not use anteroposterior middle screw because it can

act as a stress riser for fracture of the femur.

Step 18: Insert the end cap into the proximal part of the

nail for antegrade nails only.

Step 20: Close all the incisions.

Step 21: Insert the ERC device into a sterile sleeve. Mark

out the level of the magnet on the skin using fluoroscopy.

Apply the ERC directly over the magnetic spindle using the

image intensifier to mark out the magnet. Face the ERC dis-

tally for antegrade nails and proximally for retrograde nails. It

takes 7 min to lengthen the femur 1 mm.

Step 22: Check if the distraction gap is seen radiographically

and compare it to the predistraction space (FIGURE 4). If an objec-

tive increase in space is seen the procedure is completed. If not,

do a second millimeter of distraction to confirm. In the rare

case where the bone does not separate, the nail must be

extracted and tested on the bench and if it does not distract

then replaced with another nail. An incomplete osteotomy can

cause a failure of distraction.

Surgical technique tibia

Step 1: Mark the proximal and distal end of the nail as before.

Step 2: Mark the level of the osteotomy as before. In the

tibia, err on the side of a more proximal osteotomy for better

bone formation.

Step 3: Make a single unicortical drill hole anteriorly at the

level of the tibial osteotomy. A second unicortical drill hole can

be made on the medial surface. Avoid getting into the anterior

and deep posterior compartments. Multiple drill holes are not

made prior to reaming to avoid extrusion of reamings into the

deep posterior and anterior compartments, this minimizing the

risk of a compartment syndrome.

Step 4: Insert a guide wire from the distal fibula to the tibia.

This wire should be inclined from distal on the fibula to proxi-

mal on the tibia. Incise the skin on the tibial side and drill

over the wire with a 3.2-mm drill bit across both bones. Insert

a solid 4.5-mm screw from the tibia to the fibula such that the

PRECICE intramedullary limb lengthening system Device Profile

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head of the screw is on the tibial side. The screw should always

be oriented so that the tibial side is more proximal than the

fibular side.

Step 5: Perform a mid-diaphyseal fibular osteotomy through

a small posterolateral incision between the superficial posterior

and lateral muscle compartments.

Step 6: To get the starting point, insert a Steinmann pin

into the proximal tibia at the level of the joint in line with the

medial tibial spine on the AP and at the joint line on the lat-

eral view. The starting point is usually medial to the

patellar tendon.

Step 7: Ream the tibia in 1-mm increments until there is

chatter and then in 0.5-mm increments as for the femur.

Step 8: After reaming, add multiple drill holes to the

planned osteotomy level in the tibia. Using a sharp osteotome,

complete the osteotomy through the anterior incision in a

percutaneous fashion.

Step 9: Once the osteotomy is confirmed to be complete,

insert and advance the PRECICE tibial nail until the upper

end is below the level of the bone.

Step 10: Drill the first proximal locking screw from antero-

medial to posterolateral aiming for the head of the fibula:

upper locking screw hole on the left and lower locking screw

hole on the right. Measure a locking screw long enough to fix-

ate the tibia to the proximal fibula. Lock the second proximal

locking screw from the anterolateral side into the tibia only. If

the first drill hole and screw misses the fibula, then lock the

fibula with a separate 4.5-mm screw using a wire followed by a

cannulated drill from the tibia to the fibula.

Step 11: Free hand lock two of the three distal screws leav-

ing either the middle or distal one empty.

Step 12: Perform a distraction test of 1 mm using the

ERC (FIGURE 4).

Postoperative procedures

The ERC is placed firmly but comfortably over the area where

the magnet of the PRECICE implant is located. The implant

is distracted to the desired amount as viewed on the ERC dis-

play screen. Radiographs should be obtained every 2 weeks to

monitor the progress of the lengthening and to confirm that

the amount of lengthening performed has been achieved. The

radiographs also monitor the quality of the regenerate. While

1 mm/day is generally recommended, clinical and radiographic

examination may show that lengthening should progress at a

faster or slower pace (FIGURE 4). Unilateral lengthening patients

are instructed on partial weight-bearing restrictions using a

walker and then progressing to crutches. They are taught to

judge weight-bearing using a bathroom scale. Weight-bearing is

restricted to 22 kg (50 lbs) for the 8.5- and 10.7-mm nails and

34 kg (75 lbs) for the 12.5-mm PRECICE 2 nail (P2). For the

original PRECICE (now referred to as P1), the restriction was

always 22 kg (50 lbs). Bilateral lengthening cases, with

12.5-mm P2 devices are taught to walk using a walker and to

place up to 68 kg (150 lbs) when standing on both legs and

34 kg (75 lbs) on each leg during single leg stance of walking.

Similarly, bilateral 8.5- or 10.7-mm P2 cases are taught to

walk with a walker and place up to 45 kg (100 lbs) when

standing on both legs and 22 kg (50 lbs) during single leg

stance of walking. Bilateral cases are also transitioned to

crutches from a walker. All patients are given a wheelchair to

use for longer distances.

Cost–effectiveness

No studies have been performed on the cost–effectiveness of

PRECICE. The PRECICE implant is priced competitively and

comparably with other limb lengthening external fixation devi-

ces such as the Taylor Spatial Frame (Smith and Nephew

Orthopedics, Memphis, TN, USA). The PRECICE device may

even be cheaper than the combination of implants used in

techniques such as Lengthening over Nail, Lengthening and

then Nailing, etc. [17]. Reduction in device- and pin-related

complications should lead to a greater cost–effectiveness of this

device compared to external fixation. For example, external fix-

ation lengthening has a significant rate of unplanned secondary

procedure to treat device-related complications such as deep

pin infections and loosening, axial deviation, muscle contrac-

tures related to transfixation by wires or pins, etc. [18].

Therefore, reduction in unplanned secondary surgery will sig-

nificantly increase the cost–effectiveness of the PRECICE

method.

Clinical profile & postmarketing findings

Lengthening in children & adults for leg length discrepancy &

stature

Paley et al. (2013) conducted a retrospective, single-center study

to report the early results of the PRECICE system, based on

the experience of three surgeons at a single center [19].Institu-

tional Review Board approval was obtained for this study. The

results were first presented at the EPOS Annual Meeting on

April 2013 in Athens, Greece, and then at POSNA in Toronto,

Canada. This study was recently published [20]. The authors

reviewed the results of 48 consecutive patients (65 PRECICE

nails) implanted between 12/1/2011 and 12/4/2012 (all PRE-

CICE 1). The mean age of the patients in this series was

25.6 years (10.3–58.4 years). Lengthening for congenital

discrepancy (FIGURE 5) was performed in 23 patients; mean age

was 18.5 years (10.3–43.7 years) and mean pre-operative

lengthening goal was 4.91 cm (1.5–6.5 cm), while the preopera-

tive mean LLD was 6.27 cm (1.5–18.2 cm). The lengthening

rate was 0.8 mm/day. The goals of lengthening were met in all

except five patients in this group; mean lengthening was 4.5 cm

(0.5–6.5 cm) (FIGURES 6& 7). Lengthening for developmental dis-

crepancy was performed in four patients; mean age was

17.8 years (13–27 years) and mean preoperative lengthening

goal was 3.68 cm (1.5–6.5 cm). The lengthening rate was

1 mm/day. The mean lengthening was 3.68 cm (1.5–6.5 cm).

All patients achieved the preoperative lengthening goal without

any complication. Lengthening for posttraumatic limb length

discrepancies (FIGURE 8) was carried out in six patients; mean pre-

operative goal was 3.48 cm (1.7–5.0 cm) and mean age was

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49.0 years (30–58 years). The lengthening rate was 0.93 mm/

day. The mean lengthening was 3.48 cm (1.7–5.0 cm). All

patients achieved the preoperative lengthening goal without any

complication. In addition to this, 15 patients underwent stature

lengthening either for achondroplasia (FIGURE 9) or for cosmetic

reasons (FIGURE 10). Their mean age was 29.7 years (15–48 years),

baseline height was 166.2 cm (150–177 cm) and the preopera-

tive goal of lengthening was 5.64 cm (3.0–6.5 cm). The length-

ening rate was 1 mm/day. The mean lengthening was 4.63 cm

(2.7–6.5 cm). Eight patients electively stopped lengthening

before reaching their preoperative goal due to personal reasons

and not due to medical reasons.

The mean length gained was 4.41 cm (range, 0.5–6.5 cm),

with a mean distraction rate for all nail segments of 0.83 mm/

day (range, 0.50–1.11 mm/day). Three patients required a

bone grafting procedure for failed regenerate (all congenital).

Three nails broke in two patients during the consolidation

phase. All three had ignored the weight-bearing restrictions and

had stopped using crutches. Each was exchanged for a locked

standard intramedullary nail and length was preserved in each

case. Each nail that broke fractured at the proximal (2) or mid-

dle (1) weld of the first-generation PRECICE nail.

Seven nails in six patients ceased to lengthen during the dis-

traction phase. Two of these were due to operator error in

applying the ERC device in the wrong direction, leading to

breakage of the mechanism. These two were replaced and

lengthened uneventfully. In the other five, mechanism breakage

is thought to have occurred due to lengthening against a dense

regenerate or premature consolidation. All nails that ceased to

lengthen were in males with large muscular thighs. The nails

were replaced in four. The mean length achieved was 4.73 cm

(4.1–5.5 cm) in these four nails.

Mean healing time and return to full weight-bearing was

125.3 days (range, 52–262 days). In total, there were

18 unplanned surgeries in 16 patients. The remaining patients

successfully completed treatment without any complication.

The authors concluded that PRECICE demonstrated excellent

rate control and accuracy. The bidirectional feature proved use-

ful in one subject who was acutely shortened 2 cm in conjunc-

tion with treatment of a seroma, followed by resumption of

gradual lengthening 2 weeks later.

Limb lengthening in children with a new, controllable, internal

device

Herzenberg et al. (2013) conducted a retrospective, single-

center study to report preliminary results of the PRECICE sys-

tem in children [21,22]. The results were presented at the EPOS

Annual Meeting on April 2013 in Athens, Greece. The authors

A B C

8 CM

5 CM

Figure 5. Eight year old girl with congenital femoral deficiency. (A) Preoperative AP and lateral radiographs. She had been

previously treated by a superhip-superknee surgery and has also successfully undergone one external fixator lengthening at age 4. Her

leg length discrepancy was 7 cms. (B) AP radiograph after 5cms of lengthening by Precice2 8.5mms x 245mms, trochanteric entry femo-

ral nail. Her genu valgum was treated at the same time by a hemi-epiphysiodesis plate. (C) This AP radiograph during the consolidation

phase shows the distraction gap filling in with bone one month after stopping distraction.

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ABC

DE

Figure 6. Sixteen year old boy with a leg length discrepancy and valgus deformity secondary to a partial growth arrest of

the distal femur (developmental etiology). (A) Preoperative AP and lateral radiographs (B) AP and lateral radiographs after 6.5cms

lengthening using a 10.7mms trochanteric entry Precice1 tibial nail (we used a tibial nail since at the time the trochanteric entry femoral

nail was unavailable; the current P2 tibial nail has a shorter magnet and would not be a good choice to use but the P1 tibial nail had the

regular length magnet and could be used in the femur). This was our very first Precice case in December 2011. (C) AP radiograph show-

ing the worsened valgus deformity after 6.5cms of lengthening. (D) AP and lateral radiographs after acute correction of the valgus defor-

mity by a medial closing wedge osteotomy with internal fixaton using a locking plate. A peroneal nerve decompression was also done to

minimize the risk of nerve stretch injury. (E) The final AP and lateral radiographs after removal of all of the hardware a year later.

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reviewed 20 children of various etiologies who underwent

implant between January 2012 and March 2013. Mean subject

age was 13.5 years (range, 7–16 years). Mean target lengthen-

ing was 5.2 cm (range, 2.5–6.5 cm). Subjects who underwent

lengthening with external fixation as well as with the PRECICE

system were sent questionnaires and asked to compare

their experience.

At the time of the meeting, 20 of 27 limbs completed

lengthening. Target lengths programmed into the ERC closely

matched radiographic measurements (average of 5.2 vs 5.6 cm,

respectively). Range of motion (ROM) was well maintained

throughout the lengthening and consolidation phases. Of the

16 patients who were completely healed, the average distraction

index was 2.4 cm/month (range, 1.2–3.25 cm/month) and the

average healing index was 1.12 months/cm (range, 0.46–2.0

months/cm). Three complications were observed and resolved:

one prominent screw treated with revision, one peroneal nerve

entrapment treated with decompression and one rotary subluxa-

tion treated with ligament reconstruction. Nine of the 13 chil-

dren who had prior lengthening with external fixation

completed a questionnaire comparing their experience with

internal and external fixation. All reported that PRECICE

allowed for easier physical therapy, better cosmetic results and

a higher rate of overall satisfaction. When asked which device

they would choose if another surgery was needed, all nine

patients said that they would choose the PRECICE system.

The authors concluded that the device is accurate, allows for

good ROM, results in few complications and is an attractive

alternative to external fixation. More patients and long-term

follow-up are still needed.

Precision of the new remote controlled internal lengthening nail

Kirane et al. (2013) conducted a retrospective, single-center

study to evaluate the clinical efficacy of the PRECICE system.

The results were presented at the Hospital for Special Surgery

Research Symposium in June 2013 in New York, NY [23]. The

authors reviewed 10 femur and seven tibia lengthening cases

using the PRECICE system. Medical records were reviewed for

etiology, patient characteristics, surgery details, distraction pro-

cess, bone alignment, adjacent joint ROM and any

A B

CD

Figure 7. Arm shortening (6.5 cms) due to growth arrest from a unicameral bone cyst. (A) Preoperative AP and Lateral

radiographs of left humerus (B) AP radiograph at the end of 6.5cms distraction using a 10.7mms Precice1 femoral piriformis entry nail.

(C) AP and lateral radiographs after three months of consolidation. There is excellent bony bridging. (D) The nail was removed one year

later. The bone and previous cyst are well consolidated.

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complications. Distraction distance measurements were done at

every follow-up visit using a calibrated digital radiology system

(PACS, OnePacs LLC, New York, NY, USA).

The results indicated that at 13.5 weeks follow-up (range,

4–30 weeks), the lengthening was 33.65 mm (range,

14–61 mm) with an accuracy of 100.7 ±0.23%. All femur

AB

C D

Figure 8. Forty-eight year old man with a symptomatic post-traumatic 5 cms LLD of the femur. (A) Preoperative AP and lateral

radiographs of the femur. (B) Using fixator assistance, the osteotomy was made prior to reaming in order to realign the medullary canals

of the previously bayonet deformity. (C) AP and lateral radiographs after insertion of Precice1 12.5 mms nail. The bayonet deformity is

reduced. (D) AP and lateral radiographs after 5cms of lengthening. Good bone healing is seen. He proceeded to heal completely.

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cases had excellent bone healing, while two tibia cases required

insertion of bone marrow concentrate for delayed bone healing.

There were no implant failures or major complications. The

authors concluded that the new PRECICE internal lengthening

nails have an accuracy of distraction close to 100%. The use of

an external magnetic controller was straightforward and easy to

explain to patients. Notably, there were no implant failures in

this initial series. In several patients, realignment of the preex-

isting deformity was possible through an osteotomy at the apex

of the deformity. Furthermore, the hip, knee and ankle ROM

were well maintained. Iliotibial band release and gastrocnemius

recession were helpful in maintaining knee and ankle ROM,

respectively, during lengthening. Tibia lengthening was associ-

ated with more difficulties than femur lengthening. Addition-

ally, a tendency of varus-procurvatum deformity of the femur

and valgus-procurvatum deformity of the tibia was successfully

prevented by inserting blocking screws into the concavity of

the potential deformity. Lastly, consideration must be given to

the length of the thicker nail segment beyond the osteotomy to

ensure adequate stability and to prevent iatrogenic deformities.

Internal lengthening device for congenital femoral deficiency &

fibular hemimelia

Shabtai et al. (2014) reported a prospective, nonrandomized,

single-center study to evaluate the PRECICE system in terms

of healing index, complications, accuracy of the device’s exter-

nal controller and adjacent-joint ROM [24]. Institutional Review

Board approval was obtained prior to performing any study-

related procedures. Sixty six subjects were enrolled and treated

for congenital limb shortening between January 2012 and May

2013. Of these, 21 were treated using the PRECICE system

and 18 met the eligibility criteria for analysis of the PRECICE

system. Ten females and eight males were enrolled with a

mean age of 19 years. Sixteen femurs and five tibias were

lengthened with a mean of 4.4 cm (range, 2.1–6.5 cm). Mean

distraction index was 1.0 mm/day (range, 0.5–1.8 mm/day).

Healing index complications, device accuracy and ROM

were recorded.

At the time of the publication, 10 of the 21 devices had

been removed. This was typically done 12–24 months after

insertion when the bone was solidly healed on all four cortices.

Mean healing index was 0.91 months/cm (range, 0.2–2.0

months/cm). There were seven complications requiring an

additional unplanned surgery, including one hip flexion con-

tracture, three femurs with delayed healing, one tibia with

delayed healing, one hip subluxation/dislocation and one knee

subluxation. The external controller was accurate as pro-

grammed and actual lengthening amounts were consistent.

ROMs of the hip, knee and ankle were essentially maintained.

The authors concluded that the intramedullary implant of the

A B C D

Figure 9. Sixteen year old girl with achondroplasia who had undergone 2 previous lower limb (combined femur and tibia 4

segment lengthening) and one bilateral humeral lengthening. (A) Preoperative standing EOS scan radiographs. (B) Bilateral tibial

lengthening was carried out using Precice1 10.7mms tibial nails. (C) Two weeks later she underwent removal of the previous femoral

nails and insertion of bilateral 10.7 mms Precice1 trochanteric entry nails. Both femurs were lengthened 6.5 cms and tibias 5 cms simul-

taneously. The staggered nail insertion was to avoid reaming all four bones at the same time because of the risk of fat embolism. (D)

The patient is now 62 inches (158 cms) tall.

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device allows for satisfactory joint motion during treatment in

most patients. Lengthening was achieved in an accurate, con-

trolled manner and all patients reached their goal length. Com-

plications remain a concern as is the case with all approaches

in this complex patient population.

Precision of the PRECICE internal bone lengthening nail

Kirane et al. (2014) reported a retrospective, single-center

study to evaluate the PRECICE system in terms of accuracy

and precision of distraction, effects on bone alignment,

effects on adjacent-joint ROM, and frequency of implant-

related and non-implant-related complications [25].Twenty

four patients were reviewed whounderwentfemoraland/or

tibial lengthening procedures using the PRECICE nail from

August 2012 to July 2013 for conditions of varied etiology.

At each postoperative visit, the accuracy and precision of dis-

traction, bone alignment, joint ROM and any complications

were recorded. Accuracy reflected how close the measured

lengthening was to the prescribed distraction at each postop-

erative visit, while precision reflected how close the repeated

measurements were to each other over the course of the total

lengthening period. No patients were lost to follow-up.

Minimum follow-up from surgery was 3 weeks (mean

14 weeks; range, 3–29 weeks).

The results indicated that mean total lengthening was

35 mm (range, 14–65 mm), with an accuracy of 96% and a

precision of 86%. All patients achieved target lengthening with

minimal unintentional side effects on bone alignment. The

knee and ankle ROMs were minimally affected. Of the compli-

cations requiring return to the operating room for an addi-

tional surgical procedure, there was one (4%) implant failure

caused by a nonfunctional distraction mechanism and six

(24%) non-implant-related complications, including premature

consolidation in one patient (4%), delayed bone healing in two

(8%), delayed equinius contracture in two (8%) and toe claw-

ing in one (4%). The authors concluded that the PRECICE

system is a valid option to achieve accurate and precise limb

lengthening to treat a variety of conditions with limb shorten-

ing or length discrepancy.

How precise is PRECICE compared to ISKD in intramedullary limb

lengthening?

Schiedel et al. (2014) reported a prospective, nonrandomized,

single-center study to evaluate the reliability and safety of the

A

B

Figure 10. Cosmetic stature lengthening. (A) Three EOS scan AP radiographs (left), after bilateral femoral lengthening (6.5 cms) using

Precice1 12.5 mms piriformis entry nails (middle), and after bilateral tibial lengthening (4.5cms) using Precice1 10.7 mms tibial nails (left).

The total height increase was 11cms. (B) Long lateral radiographs of both femurs and tibias show that there is a deficiency in the ante-

rior bone formation of the left tibia compensated by hypertrophic regenerate bone formation posteriorly. On the right there is a break in

the Precice 1 nail through one of the welds. This break occurred due to delay in regenerate bone formation and resumption of weight-

bearing. Fortunately, the bone healed with minimal procurvatum deformation of the tibia.

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first generation of the PRECICE system [26]. Institutional

Review Board approval was obtained prior to performing any

study-related procedures. Twenty four patients with 26 PRE-

CICE nails were enrolled and implanted between June

2012 and March 2013. Anteroposterior radiographs of the leg

while the patient was standing were obtained before surgery,

every 14 days during lengthening and during or after consoli-

dation. The occurrence of any problems, obstacles and compli-

cations was recorded after lengthening was completed. The

Paley classification was used for comparison with other length-

ening procedures and external lengthening procedures. Prelimi-

nary results were compared with the known difficulties in the

use of mechanical lengthening devices such as ISKD.

The results showed that two nails did not function properly,

yielding 24 of the 26 nails implanted that lengthened over the

desired distance. Lengthening desired was 38 mm and length-

ening obtained was 37 mm. There were two nail breakages,

one occurring in the welding seam and one due to an acciden-

tal fall by the patient during consolidation. In total, 15 prob-

lems, five obstacles and four complications were observed

throughout treatment of the study cohort. The authors con-

cluded that the mean accuracy of lengthening with PRECICE,

97%, is similar to that in the comparable ISKD study

(96%) [26], and that continuing improvements to the system by

the manufacturer, including the recent release of the second-

generation system, will address the issues observed in this

study.

Alternative devices

The use of limb lengthening instruments is a well-known tech-

nique in the treatment of lower limb discrepancies. TABLE 1lists

other implantable limb lengthening devices described in the lit-

erature. The indication/intended use statements are gathered

from the literature and other publically available sources of

information, such as company web sites.

Published reports on Albizzia, ISKD and Fitbone report a

wide variety of problems and complications. Simpson et al.

reported that seven of their 33 (21.2%) ISKD nails were classi-

fied as runaway implants [8]. This meant that the rate of dis-

traction could not be controlled in 21.2% of patients and

exceeded the desired lengthening rate. A total of 15/33

(45.4%) of their nails experienced rate control complications,

with seven lengthening too quickly and another seven being

overly difficult to lengthen. Elsewhere in the literature, we can

find reports of ISKD nails that lengthened at rates much

greater than 1 mm/day or were classified as runaway nails rang-

ing from 9% (1/11, Kubiak) to 18.9% (7/37, Kenawey) to

83.3% (10/12) in the series by Mahboubian et al. (Hankeme-

ier) [27–30]. Wang et al. reports that five of their 16 nails length-

ened uncontrollably, forcing them to ask these patients to

modify their weight-bearing and activity level from week to

week based on the rate of distraction of the nail. If it were dis-

tracting too slowly, they would be asked to increase their

weight-bearing and to become more active, and vice versa

(Wang, Simpson) [31,32]. At best, this was a very imperfect way

of controlling the rate of distraction of ISKD. There are addi-

tional series that further detail runaway nail rates that range

from 9% (Kubiak) to 20% (Paley) [27,33]. The article by the

ISKD’s designer (Cole) reviewed his initial series of 20 nails in

18 patients [34]. They reported lengthening rates of up to

1.7 mm/day, but no mention is made as to how many patients

lengthened at such a rapid rate. In an unpublished study by

Paley, of 350 ISKD lengthenings, distraction rates of up to

5 mm/day were documented.

A large majority of patients with runaway nails went on to

develop poor regenerate or nonunion at the distraction site.

While the article by Cole et al. observed zero nonunions or

patients who required a later bone graft procedure, other

articles document rates of runaway nails requiring additional

surgery in the form of either bone grafting or exchange nailing

that range from 20% (Wang 1/5, Kenawey 5/7 to Simpson

6/7) to 86% [8,28,31].

Certainly, poor regenerate formation/nonunion is not exclu-

sive to intramedullary nails that fail to maintain safe rate con-

trol, but rather this remains a well-known complication for all

limb lengthening procedures. While only 1/5 of the runaway

nails in the article by Wang et al. required later bone grafting,

a total of six out of their 16 ISKDs (37.5%) required an addi-

tional surgery to treat poor regenerate or nonunion [31]. Simp-

son needed to treat only 6/8 (75%) of his runaway nails with

additional surgery, although, a total of 8/33 (24.2%) nails ulti-

mately required this approach [8]. Five of the seven (71.4%)

runaway nails in Kenawey’s series required bone graft and/or

exchange nailing, along with an additional three nails that simi-

larly developed deficient bone healing, for a total of

8/37 (21.6%) [28]. Singh et al. reported that 3/24 (12.5%) of

Table 1. Alternative devices and intended use.

Device Manufacturer Intended use Distraction mechanism Materials Device status

Albizzia/Guichet DePuy

Orthopedics

For limb lengthening of

the tibia and femur

Mechanical telescoping,

gear actuation

Stainless

steel

CE Mark, not approved

in the USA

Fitbone Wittenstein

GmbH

For limb lengthening of

the tibia and femur

Motorized, radiofrequency

powered telescoping, gear

actuation

Titanium

alloy

CE Mark, not approved

in the USA

ISKD Orthofix Inc. For limb lengthening of

the tibia and femur

Mechanical telescoping,

gear actuation

Titanium

alloy

CE Mark, recalled in the

USA

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their Fitbone nail segments required later bone grafting, and

Baumgart et al. saw that 1/12 (8.3%) Fitbone segments need

additional surgery to achieve adequate healing [3,34].

Kenawey et al. found a significant association between poor

regenerate and age of patients greater than 30, total lengthening

greater than 4 cm, smoking and a distraction rate greater than

1.5 mm/day [28].

One risk that has been reported to be a predisposing factor

to poor regenerate is a distraction rate greater than 1.5 mm/

day (Kenawey) [28]. This is entirely avoided with the PRECICE

nail. In comparison to the results listed above, Paley et al.

reported that only three of 65 implant segments went on to

develop poor regenerate of nonunion that necessitated an addi-

tional bone grafting surgery.

Another well-reported problem with implantable lengthen-

ing nails is difficulty with distraction. Kubiak et al. attributed

this to impingement and friction secondary to a straight nail

attempting to lengthen a curved femur as well as compressive

forces caused by the soft tissues that are substantial enough to

limit lengthening. This complication is still the most frequent

one with the Albizzia nail. Failure to distract can be related to

wear of the teeth of the internal ratchet gear or due to the

inability of the patient to turn the limb the full 20 degrees

due to pain. Similarly with ISKD, some patients have too

much pain to rotate the femur the 3–9 degrees needed.

Manipulation by the surgeon in the office to manipulation

under epidural or other anesthesia has been used to treat this

problem. Botox injection into the quadriceps to reduce muscle

spasm is also useful. Incidence of failure to distract with

ISKD varies from 0% (Cole) to 64% (Kubiak), of whom 6/

7 of the patients in that series required a return to the operat-

ing room [27,33]. Similarly, the Simpson series had a rate of

24.2% (8/33) of ISKD nails that were difficult to distract,

and 75% (6/8) of those needed a return to the operating

room [8].

Paley et al. reported seven cases of PRECICE with failure to

distract. One bilateral case occurred due to user error. The

others occurred due to resistance from abundant callus and

large thigh musculature. It is likely that the failure of the mech-

anism occurred after repeated lengthening attempts against the

force of a nearly prematurely consolidated bone. Since the

mechanism was changed in PRECICE 1 (May 2013) and since

the introduction of PRECICE 2 which contains the new mech-

anism, there have been no further failures of distraction in over

150 cases [PALEY D, PERS.COMM.].

Mechanical failure of other implantable nails can be

divided into two groups: mechanical failure of the distraction

mechanism and breakage of the integrity of the nail itself. In

the Baumgart et al. series of 12 cases, two patients required

reoperation for failure of mechanism [34]. There were no nail

breakages in this series. In a Fitbone series of 24 nails, two

patients had to have exchange nails to larger diameter Fit-

bone nails as the gears were too weak for distraction. Both

these patients had congenital deformities (Singh et al.)[3].

Another Fitbone cohort of eight patients reported one

mechanism failure and one nail breakage; both were also

congenital etiologies (Krieg et al.)[35]. The ISKD initial series

(20 nails) reported two hardware failures; both nails broke

with patients fully weight-bearing and at the junction of the

proximal and distal components. Design changes were made

in the nail and authors claimed no further breakages. This

further stresses the importance of in vivo analysis of these

devices and appropriate engineering adjustments to improve

product design. No mention of mechanism failure was noted

in this series (Cole et al.)[33]. Another review of 57 ISKD

nails revealed no nail breakages; however, three failures of

the lengthening mechanism occurred. One required an

exchange nail with an examination of the failed nail showing

a jammed ratchet mechanism. The other two nails required

manipulation another anesthesia, One nail acutely lengthened

3 cm instead of 3 mm despite external monitoring, again

illustrating the unpredictability of the ISKD (Kenawey

et al.)[28]. In the largest ISKD series of 242 devices,

15 (6.2%) experienced mechanical failure. Ten of these fail-

ures were nail fractures, two of which were in the same

patient undergoing stature lengthening. Most fractures were

in the male component; however, other areas of nail were

prone to failure as well. The remaining five nails failed at

the lengthening mechanism, two of which failed due to

assembly error (Burghardt et al.)[34]. Ensuring the functional-

ity of the nail during surgery, as in our surgical protocol,

would circumvent these types of complications. In 41 Albizzia

nail insertions, three failures were related to the distraction

mechanism and one to nail fracture, all requiring reoperation

(Guichet et al.)[35].

Among 10 patients (24 nails) with the Fitbone device, two

patients (20%) did not reach the anticipated length due to

restricted knee movement. Both these patients were undergoing

stature lengthening and had femoral and tibial lengthening

(Singh et al.)[3]. In a smaller series (eight patients) using the

same device, they achieved 93% (83–100%) planned length.

However, two of the eight patients were eliminated from this

analysis due to nail failure (Krieg et al.)[35].

Using the ISKD nail lengthening of 33 limbs resulted in

32 achieving desired goals. However, eight patients (eight

limbs) required additional procedures (manipulation, fixator-

assisted) to achieve this due to slow or no progression of dis-

traction (Simpson et al. 2009) [8]. Baumgart’s cohort of

12 patients attained complete length objectives in all patients [2].

Interestingly, all these patients received unilateral lengthening,

which eliminates many factors that may cause premature termi-

nation. Similar to our series most of these terminations were in

the bilateral group. Nevertheless, internal devices in previous

and in our current series seem to have a good track record for

obtaining desired lengths.

Pain is an important consideration with every lengthening

method. Pain is an expected part of lengthening. The degree

of pain does vary between external and internal fixation meth-

ods. Pin sites and pin infections as well as tethering of

muscles and other soft tissues are believed to be a major cause

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of pain during lengthening with external fixation. Since all of

these are absent with implantable devices, the pain is related

to stability, rate of distraction, physical therapy and stretch of

soft tissues. While it is not possible to eliminate stretch, con-

trol of rate and stability of fixation is device dependent. Fric-

tion may also play a part and can be limited by the type of

reamers used (straight vs flexible), amount of overreaming as

well as by the level of osteotomy (at apex of curvature of

femur; leaving as short an amount of nail to drag on the

moving segment).

Pain is a major factor with Albizzia and ISKD. Both of these

devices rotate through the callus. Such rotation leads to friction

and muscle spasm pain. This type of pain has been notably

absent from reports on Fitbone and from the experience

with PRECICE.

Using devices that require no rotation such as the motor-

ized Fitbone, there was minimumtonopainondistraction

(Singh et al.)[3].However,ofthe10patients,whohad

24 implants, only two achieved 60 mm. The rest were

between 27 and 50 mm, with a mean of 40 mm/nail. In

contrast, of the 31 patients using the Albizzia nail, all experi-

enced discomfort or pain during lengthening. Twelve

patients (39%) required readmission to perform racheting

under a general anesthetic (Guichet et al.)[36]. PRECICE

patients seem to have minimal to no pain during

lengthening.

A B C

D E

Figure 11. Fifty five year old man with ankle arthritis and pain. (A) Preoperative AP and lateral radiographs of the tibia, ankle and

foot. (B) Intra-operative fluroscopic picture of a lateral of the foot showing the ankle fusion and retrograde insertion of the first Precice2

in the US November 2013. (C) The distal tibia was lengthened 2.5 cm. (D) The ankle was fused and LLD equalized intentionally leaving a

1 cm discrepancy. (E) AP and lateral radiographs showing union of the ankle fusion and the distraction gap.

PRECICE intramedullary limb lengthening system Device Profile

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Status of the device

The first generation of the PRECICE system was granted

CE Mark in September 2010 and FDA 510(k) clearance in

July 2011 for limb lengthening of the femur or tibia. The

PRECICE 2 system received CE Mark in May 2013 and

FDA 510(k) clearance in October 2013. Commercial use

of the PRECICE system began internationally and in the

USA in 2011. The PRECICE 2 received FDA clearance in

October 2013. Its clinical use in the USA began in November

2013 (FIGURE 11).

PRECICE 2

In 2012, in response to preliminary results of breakage through

the welds and failure to distract in some cases (Paley et al.,

EPOS, POSNA) [20], Ellipse Technologies together with Paley

began a redesign of the nail housing to eliminate the welds as

well as a redesign of the nail mechanism to increase its ability

to distract against resistance (FIGURES 5 & 11). The mechanism

problem was solved first but modifying the coupling between

the drive shaft and the gears. Previously, the powerful torque

strength of the rotating magnet could break this connection if

it met too much resistance. The new mechanism is protected

against this and is now three-times stronger in distraction

strength. The tibial models have been loaded with a smaller

magnet to prevent from overtorquing the magnet due to the

closer proximity of the ERC to the magnet in the tibia. Conse-

quently, PRECICE 2 tibial nails should not be used in the

femur since there would not be enough strength to turn the

smaller magnet with the ERC at larger distances from the mag-

net. The new mechanism had its debut in May 2013 with a

retrofit of all PRECICE 1. The newer mechanism has per-

formed perfectly with no documented cases of failure to dis-

tract to date. At our center alone, over 150 nails with the new

mechanism have been implanted and lengthened successfully

to date.

The elimination of the welds has also greatly strengthened

the nail. Laboratory testing has shown that the weld-less

PRECICE 2 nail is four-times stronger for bending strength

and three-times stronger for axial loading than the original

nail. To date, with over 250 of these PRECICE 2 nails

implanted there have been only two reports of nail breakage.

One was my own patient who was undergoing a congenital

femoral lengthening after a previous knee fusion. This

18-year-old young man chose to ignore all weight-bearing

restrictions after a unilateral 8-cm lengthening. His nail

broke the external shell at the distal telescopic junction.

Angulation occurred without any loss of length. The nail

was successfully exchanged for a trauma locking nail 3 days

after the failure. One European tibial nail broke through the

proximal locking screw hole. After review of that case, it

was evident to me that the nail was inserted too anteriorly

leading to poor support from the surrounding bone. Fur-

thermore, there was a blocking screw inserted at the level of

the break. Since titanium is very notch sensitive, slight

notching of the nail by the blocking screw at the level of

the locking hole with a very proximaltibialosteotomyset

up the nail for failure. Surgeon error is more at fault in this

case. Weight-bearing restrictions are essential to the use of

this nail. They have been increased to 75 lbs during the dis-

traction phase for the 12.5-mm PRECICE 2 from only

50 lbs for the 12.5-mm PRECICE 1. These should be

adjusted downwards when additional factors add to the load

on the nail as is illustrated in the two failure cases. PRE-

CICE 2 seems to have eliminated the two main device fail-

ure mechanisms that were identified with PRECICE 1. The

company has been very responsive and implemented these

changes in record time. One observation made by Paley is

that some nails showed a varus bowing of the nail in some

femoral lengthenings (FIGURE 12). This has not led to any fail-

uretodistractortoanysignificantdeformityorbreakage.

It may be related to the nail being made of titanium. This

is especially in bilateral application where patients may be

weight-bearing more than allowed. One solution would be

changing the material of the nail to a stiffer alloy such as

cobalt-chrome. In 2014 some fragmentation of the end of

the outer tube of the nail has been noted. The end of the

larger diameter of the nail is slotted at four places and

mated and welded to a crown that has 4 ridges to provide

anti-rotation stability to the telescopic nail. The fins

between the slots are the sight of fragmentation of the end

Figure 12. AP radiograph of bilateral femoral lengthening

seen during an 8-cm cosmetic stature lengthening. This

went on to heal uneventfully. The mild varus neutralizes the

valgus deviation that is associated with lengthening along the

anatomic axis. The concern is mostly regarding the risks of

nail breakage. Strict weight-bearing precautions should accom-

pany any bilateral lengthening and especially if bowing is seen.

Device Profile Paley

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of the nail tube. Breakages of this crown and fins have been

identified in some cases including this patient (FIGURE 13).In

two cases it has been linked to breakage of the nail. It is

also contributing to the bowing of the nail. To strengthen

the nail and avoid crown failures, in December 2014,

Ellipse Technologies releasedtheP2.1whichhasamodified

keying feature without ‘thru-slots’or tack welds (FIGURE 13).

Conclusion

PRECICE is the newest generation implantable limb length-

ening device and the first CE-marked and FDA-cleared device

to have both forward and reverse length adjustment capability.

It had demonstrated excellent rate control. This is the most

important factor for achieving good results with any limb

lengthening. The reverse mechanism although not often used

is very helpful when it is needed. It can be used to close

down a distraction gap when there is failed bone formation,

or nerve irritation or palsy. It can also be used to dynamize

the regenerate bone (compression-distraction) when there is

delayed consolidation (accordion maneuver). The reduction in

size of the implant down to 8.5-mm diameter as well as the

reduction in length of the device down to 195 mm makes

PRECICE applicable to pediatric femurs as young as 7 years

of age. The improvement in strength of the nail and the

mechanism have also made it more reliable, allowing for

weight-bearing.

Expert commentary

Implantable limb lengthening is the natural progression for

limb lengthening technology. Since I got involved with limb

lengthening in 1985, we have witnessed an evolution of tech-

niques related directly and indirectly to limb lengthen-

ing [37–39]. The gold standard external fixation device has

advanced with circular fixators being computer controlled

and automated [39], monolateral fixators having hinges and

spanning joints. Meanwhile, the implantable lengthening

devices have struggled to get FDA approval. Early devices

such as Bliskunov, Albizzia and Fitbone developed in Europe

asearlyasthe80sand90shavenevergotFDAclearance.

Therefore, the FDA clearance (510k) of the Orthofix ISKD

in 2001 was a landmark event. Unfortunately, the lack of

rate control and pain issues dampened the initial enthusiasm

with this device. The FDA clearance of PRECICE in

2011 represented the next major milestone for implantable

devices.Theappearanceofthisdeviceonthemarketwill

probably soon be followed by other such devices. PRECICE

A B

C

Figure 13. Photographs of two nails removed from a patient who underwent bilateral femoral lengthening. There is a crown

breakage on the right femur nail with propagation of cracks up from the nail slots (left side of figure) while the crown and slots remain

intact on the nail from the left femur (right side of figure) (A). The P2 nail anti-rotation mechanism uses four female ‘thru-slots’in the

distal end of the proximal nail tube mating with the crown’s four male ridges, and secured with tacking welds after assembly (B). The

new P 2.1 anti-rotation feature is machined into the inner diameter of the distal end of the proximal nail tube without breaking through

to the surface and without requiring welds (C).

PRECICE intramedullary limb lengthening system Device Profile

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however has raised the bar. To compete, a device will have to

demonstrate excellent rate control, forward and reverse capa-

bility, sufficient strength of the mechanism to resist the large

forces of the regenerate bone and musculature, and sufficient

strength to allow partial weight-bearing without breakage of

the implant.

Five-year view

Bliskunov first introduced implantable limb lengthening in

1983 (over 30 years ago). Therefore, the use of implantable

lengthening devices is still initsinfancy.AsPRECICEisthe

first limb lengthening nail to have forward and reverse capa-

bility,itisfairtocallitthefirstsecond-generationimplant-

able limb lengthening device. The first-generation devices

were ones that can only lengthen and distract but not

shorten and compress. Thus far, the indications for implant-

able lengthening have only been for lengthening of long

bones and for distraction of the spine for the treatment of

scoliosis [35]. The gold standard of distraction is the external

fixator. The external fixator is able to apply distraction for

many other indications. These include treatment of bone

defectsbybonetransport,treatmentofdeformitybyasym-

metric distraction, treatment of nonunions by compression-

distraction, etc. The next 5 years will see a plethora of new

remote controlled implantable devices and a wide variety of

drive mechanisms. We anticipate a bone transport nail, a

bone lengthening plate, an angular deformity plate, a trauma

nail that can correct mal-rotation and length, a nonunion

device that can compress-distract, implantable articulated dis-

traction of joints and joint contractures,etc.Currently,size

is a major limiting factor. External fixators or external cable-

driven implants are the only way to apply distraction tech-

nology to smaller bones such as in small children, forearm,

hand and foot, and cranio-maxillo-facial bones. The next

5 years will see miniaturization of remote control implant

technology.

Acknowledgements

The author wishes to thank C Hafner from Ellipse Technologies for his

help in the research and preparation of this manuscript.

Financial & competing interests disclosure

D Paley is a paid consultant for Ellipse Technologies and also receive royalties

on this device. The author has no relevant affiliations or financial involve-

ment with any organization or entity with a financial interest in or financial

conflict with the subject matter or materials discussed in the manuscript.

This includes employment, consultancies, honoraria, stock ownership or

options, expert testimony, grants or patents received or pending, or royalties.

Key issues

.Implantable distraction technology is reliable in producing distraction osteogenesis of bone and distraction histogenesis of soft

tissues.

.PRECICE is the first forward and reverse remote controlled implant for bone lengthening.

.PRECICE has excellent efficacy and rate control and reduces the pain of limb lengthening compared to external fixation.

.PRECICE reduces device-related complications seen with external fixation.

.Miniaturization of diameter and length has made it useable in smaller long bones such as the humerus, small patients such as children

and dwarfism.

.PRECICE is the first second-generation implantable lengthening device.

.Many new applications and devices are expected over the next 5 years.

References

Papers of special note have been highlighted as:

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.This is the first study to classify and

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PRECICE intramedullary limb lengthening system Device Profile

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This article may include discussion of both on and off-label uses of our products. Please note that this study may have limitations

whether it be the study-size, endpoints, lack of randomization, period of follow-up, etc. Discussion in this article may also provide

only anecdotal information. This article may be the result of company-sponsored research or grants provided to physicians who

conducted the research on their own. Some authors may be consultants to Ellipse-Tech, others are not. The reader should

understand these limitations before reading them and critically review all these sources of information.

The FDA-cleared intended use for PRECICE is as follows:

The Ellipse Technologies PRECICE Intramedullary Limb Lengthening System is indicated for limb lengthening of the tibia or femur.

Please see the full prescribing information (IFU) for the contraindications, side effects, warnings and precautions.