Medical Policy

Policy Num:      07.001.175
Policy Name:  Intramedullary Limb-Lengthening System
Policy ID        [07.001.175][Ac /L /M+ /P+][0.00.00]

Last Review:    October 24, 2024
Next Review:    October 20, 2025
 

Related Policies:

07.001.017 - Ilizarov Bone-Lengthening Procedure

Intramedullary Limb-Lengthening System

Summary

Intramedullary limb-lengthening systems (ILLS) have been introduced as an alternative to the circular external fixation to reduce complications and improve patient comfort. ILLS was designed to control the lengthening process using remote control technology. The electrical (FITBONE) and the magnetic (PRECICE) driven motorized intramedullary bone-lengthening nails were introduced. With these, conflicts with the first mechanically driven intramedullary bone-lengthening nail, which had challenges controlling the lengthening rate, and a relevant point of the treatment, were expected to be resolved.

Summary of Evidence

For individuals with have comminuted fractures, nonunion fractures, congenital or aquired deformities of the lower extremity, the evidence includes systematic reviews, retrospective case reviews and cohort studies. Relevant outcomes are morbid events, quality of life, and functional outcomes. The FDA has approved intramedullary limb lengthening devices for limb lengthening, in open and closed fracture fixation, pseudarthrosis, malunions, nonunions, or bone transport of long bones in patients aged 12 and older (following the manufacturers guidelines). The evidence concludes that the application of intramedullary nail lengthening techniques provide faster results with low incidence on complications. Following initial excellent outcomes published, the use of the lengthening intramedullary nail has become accepted by many as the implant of choice in limb lengthening. The literature supports the use of ILLS as a surgical technique for the efficacy of the treatment and its cost effectiveness, even reaching the status of goldstandard for cases of femoral lenghtening²⁴. The evidence is sufficient to determine that the technology results in an improvement in the net health outcome.

Objective

The objective of this evidence review is to determine whether the use of intramedullary limb-lengthening systems improves the net health outcome for people presenting with long bone length discrepancies.

Policy Statement

Intramedullary limb-lengthening systems with the purpose of bone-lengthening are considered medically necessary for the correction of congenital, or post-traumatic limb length discrepancies, and/or aquired deformities of the long bones in patients 12 years and older.

Specific cases include:

• demonstrable non-union or mal union of long bone, with or without bone loss or infection.
• lengthening of an amputation stump for proper fitting of a prosthesis.
• leg lengthening needed to equalize or correct leg length discrepancy greater than 6 cm (60mm)
• congenital or post-traumatic angular/rotational deformations of the long bones.
• bone defects with or without deformities.

The PRECICE Intra-medullary Limb Lengthening System is considered medically necessary: 

• In patients 18 years and older for limb lengthening, open and closed fracture fixation, pseudarthrosis, malunions, nonunions, or bone transport of long bones use and,
• In patients greater than 12 years old for limb lengthening of the femur and tibia.

The FITBONE Intra-medullary Limb Lengthening System is considered medically necessary: 

• In patients greater than 12 years through 21 years for limb lengthening of the femur and tibia.

Use of an intramedullary bone-lengthening device for the sole purpose of altering short stature is considered investigational

Policy Guidelines

OrthoNext™ Fitbone™ Contraindications

• Patients with any open wounds or areas with poor soft tissue coverage near the operative site
• Patients with anatomic deformities that prevent the device from fitting
• Patients with poor bone quality that would prevent adequate fixation of the device
• Patients with compromised capacity for healing
• Patients with metal allergies and sensitivities
• Patients in which the implant would cross open, healthy epiphyseal growth plates
• Blood supply limitations, peripheral vascular disease or evidence of inadequate vascularity
• Insufficient intramedullary space that would lead to cortical weakening or vascular damage during an implantation
• Patients with extreme body weight (<110lbs, 220 lbs <) 
• Differences in leg length of less than 20 mm
• No free access for proximal insertion of the intramedullary lengthening nail (e.g. coxa valga)
• No reliable exclusion of bone infection
• Expected non-compliance, mentally ill patient or patient with clouded consciousness
• Pregnancy

PRECICE Intramedullary Limb Lengthening System contraindications include: 

• Infection or Pathologic conditions of bone such as osteopenia which would impair the ability to securely fix the device.
• Patients with Gustilo open fracture Classification Grade IIIB or IIIC fractures
• Patients with pre-existing nerve palsies
• Metal allergies and sensitivities.
• Patients with an irregular bone diameter that would prevent insertion of the PRECICE Intramedullary Limb Lengthening nail.
• Patients in which the PRECICE Intramedullary Limb Lengthening nail would cross joint spaces or open epiphyseal growth plates.
• Patients in which there is an obliterated medullary canal or other conditions that tend to retard healing such as blood supply limitations, peripheral vascular disease or evidence of inadequate vascularity.
• Patients unwilling or incapable of following postoperative care instructions.
• Patients who are pregnant.

Benefit Application

BlueCard/National Account Issues

State or federal mandates (eg, Federal Employee Program) may dictate that certain U.S. Food and Drug Administration-approved devices, drugs, or biologics may not be considered investigational, and thus these devices may be assessed only by their medical necessity.

Benefits are determined by the group contract, member benefit booklet, and/or individual subscriber certificate in effect at the time services were rendered. Benefit products or negotiated coverages may have all or some of the services discussed in this medical policy excluded from their coverage.

Background

In 1954, the first successful treatment by distraction osteogenesis was recorded by Gavriil Abramovich Illizarov using the circular external fixation. Distraction osteogenesis or callus distraction is the process of surgically cutting bone and slowly separating its two sections. The space created by the separation of the two ends allows for new bone to regenerate inside the gap. The new bone allows for up to 6 inches (15cm) of length to a leg. 

The process of acute or rapid incremental distraction had been in use for more than half a century, and since Illizarov recognized the process and benefits of biological periosteum - preserving osteotomies, and at incremental lengthening at slow (1mm/day) at a 4 × 0.25-mm daily rhythm and described as Callostasis. 

Leg length discrepancies

Anisomelia or short leg syndrome, is a condition that affects the pediatric and adult population. It is diagnosed when one leg is shorter than the other, mostly caused by congenital conditions, also by trauma, infection of the bone growth plates, poorly healed bone fractures, or bone tumors. 

Some causes of Congenital leg discrepancies are: 

• Fibular hemimelia - short or missing fibula or any other lower leg bone.
• Congenital short femur, considered as a severe shortening or complete absence of the femur bone. 
• Hemiatrophy - atrophy that affects one half of an organ or part or one side of the whole body.
• Hemihypertrophy (also called hemihyperplasia) a condition in which one side of the body or a part of one side of the body (such as a hand or leg) grows significantly more than the other due to an over-production of bone or soft tissue.

Damage to growth plates (physes), especially in children, can cause a bone to stop growing prematurely, leading to leg length discrepancy and deformity. Acquired conditions for short leg syndrome is often a result of:

• Severe traumas– Fractures occurring from car accidents, falls, other extreme-force impact injuries, or competitive sport.
• Osteomyelitis - infections in the bloodstream that form a deep infection in a joint or bone growth plate, where significant blood flows. 
• Benign bone tumors such as enchondromas, osteochondromas, or fibrous dysplasia.
• Degenerative disorders as in Legg-Calvé- Perthes Disease
• Bone fractures healed in abnormal positions (malunion).
• Neurofibromatosis.
• Ollier disease - cysts or tumors called enchondromas.
• Neurologic conditions like polio, a nerve injury from an early age, or spina bifida.
• Bone loss from tumors, trauma or infection.
• Surgical disorders such as joint replacement

Effects of Leg Length Discrepancies

Even if approximately 70% to 90% of the population can present with a degree of LLD (0.5 - 1.5cm), most of the population can compensate for a difference of 2cm (20mm) or less. As the discrepancies increase, structural changes can be observed and additional muscular compensation occurs, resulting in distinct signs and symptoms. When any of the legs are uncompensated, the anterior and posterior iliac spine on the side of the short leg can be lower which may result in an uneven sacral base and/or scoliosis, with increased muscle activity in several muscle groups.

The Effect of Leg Lenght Discrepancies (LLD) in Walking vs Running

Walking	Running
Gait asymmetries throughout the kinetic chain.	Stress on the lower extremity that is three times that of walking
Increased vertical displacement of the center of mass resulting in increased energy consumption. Compensatory mechanisms for this include-calcaneal eversion: knee extension: toe walking: circumduction: hip or knee flexion (steppage gait).
Decreased stance time and stride length in the shorter leg.
Decreased walking velocity, increased walking cadence.

Leg Length Discrepancy. (2016). Physiopedia 

Musculoskeletal Disorders related to LLD

• Low back pain
• Scoliosis
• Hip Pain
• Stress Fractures 
• Osteoarthritis
• Bursitis 
• Patellar Tendinopathy or other joint incongruences

Medical Management

Patient criteria for lengthening (Callostasis) applies when a person has a significant difference of more than 4 -5 cm (40-50mm). More than 2 cm (20 mm) is regarded as an indication for therapeutic measures, 2–4 cm and enough growth in an individual above the 50th percentile for height an indication for growth modulation (epiphysiodesis). The most accurate method to identify leg length discrepancy is through radiography. The magnitude of the discrepancy can be classified as mild (0-30 mm), moderate (30-60mm), and severe (>60mm), and whether the patient is symptomatic. Surgical intervention must be dealt in a case-by-case basis, considering severe cases to always be corrected surgically. Due to the significant risk of secondary malalignment, indications for lengthening by unilateral fixation have shrunken to moderate amounts of length disparity and uni- to bi-planar deformities in patients with still open physis. ^2,3

Non-Surgical Interventions

Shoe lifts - used when LLD is mild to moderate and with functional signs. It's the most common treatment for leg length discrepancy. It can be a costly treatment, requiring the lift to be applied to every shoe option, fitted to the inside or outside, and sometimes requiring a custom shoe to be made. There's a limitation to the type of shoe that can be worn and increases the risks for ankles sprains and fractures. 

Surgical Intervention

Surgical treatment involves slowing growth by blocking the epiphyseal plate around the knee joint or lengthening the leg with an osteotomy followed by distraction of the callus with a fully implanted or external device.

·       By stopping bone growth (in the longest leg) in pediatric patients.

·       Limb shortening in mature patients, by bone resection.

·       For limb lengthening with an LLD greater than 60 mm, a cortical osteotomy is performed first, followed by the placement of an internal or external fixator on the limb with continuous longitudinal traction of the osteotomy site.

Leg shortening - reserved for patients who have reached their full height, with a mild to moderate difference of length. It consists of cutting a section of the longer leg and joining the two ends. Metal rods and screws are used to keep the bone in place during healing. There's a risk of weakening the muscle with the removal of the bone, which is a permanent side effect of the surgery. 

Epiphysiodesis or Growth Arrest - this procedure applies to the pediatric patient who is still growing. It consists of temporarily or permanently, surgically inserting screws or plates in selective locations of the growth plates of the healthy lower limb (femur, tibia, fibula), to allow the other leg to "catch up” or reach the other leg length. It can also be used after limb lengthening to achieve length equality in both legs. Risks include a faulty height prediction, as is the surgeon's guess the growth potential of the patient. Also, the other methods can be used complementary for the patient's benefit. 

Limb Lengthening 

Internal and External Fixation - The average amount of lengthening ranges between 2.5 and 5 cm (min. 2 cm to max. 17.4 cm) for Illizarov ring fixators (IRF), and intramedullary nails. Though callostasis and complex deformity correction is predominantly a pediatric orthopedic field, the age of patients ranges from as young as 2 years up to 70 years. Patients treated with ring fixators and unilateral external fixators have an average age of around 12–16 years, whereas intramedullary or by solid nails constitute young adults around the age of 18–25 years.3  The treatment is limited by the size of the available nails, the residual growth and extent of the deformity.4 

The recommended latency time between surgery and the start of distraction is 3–10 days. After detailed oral and written instructions are given to the patient, distraction is usually effected with classic 1 mm/day (rate) divided into 4 increments/day (rhythm). 

External Fixation - There are several fixator types including uniplanar, multiplanar, unilateral, bilateral, and circular fixators. Circular fixators (The Illizarov technique) are especially effective for lengthening procedures, allowing the patient to bear weight and maintain some joint motion during treatment (Figure 1). It's based on the principle of osteogenesis or bone regeneration. In the surgical technique called Distraction Osteogenesis, a transverse bone section is performed and by gradually separating (distracting) the bone segments, new bone tissue (callus) is created and mechanically strained during healing. It takes a long time for the new bone tissue to mineralize and consolidate, which is considered a limitation of the technique. Muscles, skin, and soft tissues will slowly adapt as the extremity lengthens. Bone length will increase approximately 1mm per day, or 1 inch per month in a healthy bone.  External fixation of the upper extremities are challenging, given the intimate neurovascular relationship of neurovascular structures. The procedure also requires meticulous and strict cleaning of the area around pins and wires; and adjustment of the frame pins multiuple times a day. General contraindications include obesity, smoking, a non-compliant patient, peri-prosthetic fractures that can limit the bone stock available to place the pins, or the inability to withstand the procedure physiologically.^{5, 6} There are multiple risks and complications associated with this technique (i.e.Infection at the site of wires and pins, direct damage to neurovascular structures, Soft tissue contracture, subluxation, contraction of the joint (serious)). 

Internal Fixation with intramedullary lenghtening devices

It refers to an extending rod inserted in the bone, where the bone marrow is found, and that can be controlled externally by magnetic (Precice) or electrical (Fitbone) means.  This telescopic rod or nail contains a small motor, and it receives signals from the exterior of the skin, accurately extending the lenght as required. Distraction over an intramedullary nail allows removal of the external fixator at the end of distraction before callus consolidation (monorail method). The intramedullary nail protects newly formed callus tissue and reduces the risk of axial deviation and refractures. Recently developed, fully intramedullary lengthening devices eliminate fixator-associated complications and accelerate return to normal daily activities.7

‌Contraindications:

Contraindications as stated on the policy guidelines.

Risks and Complications:

Common complications like hematomas, infection, implant displacement, fracture malunion or non union, periprosthetic fracture, pseudarthrosis, malrotation, compartment syndrome, disorders of the arterial and venous system, neurological deficts and fat embolism--as well as into specific complications--like malreduction of the fracture, malpositioning of the guide wire, hardware failure, implant malposition, soft tissue irritation at the entry point, splitting fragments and problems with nail insertion and with the locking bolts. Also, complications are inversely related to the surgeon expertise on the procedure, and most of the cases were recorded post operatively.  ^8, 9

Systematic Review

Frost (2021) conducted a systematic review of complications with externally controlled motorized intramedullary bone lengthening nails comparing FITBONE and PRECICE. Complications were graded on severity and origin. Of 116 full text screened articles, 41 were included in the final analysis. In total, 983 segments were lengthened in 782 patients (age 8–74 years). The distribution of nails was: 214 FITBONE, 747 PRECICE, 22 either FITBONE or PRECICE. Indications for lengthening were: 208 congenital shortening, 305 acquired limb shortening, 111 short stature, 158 with unidentified etiology. He identified 332 complications (34% of segments): Type I (minimal intervention) in 11% of segments; Type II (substantial change in treatment plan) in 15% of segments; Type IIIA (failure to achieve goal) in 5% of segments; and Type IIIB (new pathology or permanent sequelae) in 3% of segments. Device and bone complications were the most frequent. 

Table 1. Classification of severity of complications in accordance with Black et al. and Paley

Flow diagram of selection of studies.

The overall risk of complications was 1 for every 3 segments lengthened. In 1 of every 4 segments, complications had a major impact leading to substantial change in treatment, failure to achieve lengthening goal, introduction of a new pathology, or permanent sequelae. Frost stated that as no standardized reporting method for complications exists, the true complication rates might be different. ⁵

Regulatory Status

The PRECICE Intramedullary Limb Lengthening System is indicated for limb lengthening, open and closed fracture fixation, pseudarthrosis, malunions, nonunions, or bone transport of long bones in patients age 18 years and older and indicated for limb lengthening of the femur and tibia in pediatric patients (greater than 12 years old).

FDA 501(k) Number K2202234, Product Code HSB

Be aware that Precice Intra-medullary Limb Lengthening system (including Precice Short) is intended for use: 

• in patients 18 years and older: for limb lengthening, open and closed fracture fixation, pseudarthrosis, malunions, nonunions, or bone transport of long bones use and 
• in patients greater than 12 years old: for limb lengthening of the femur and tibia.

Be aware that Precice Freedom and Unyte devices are intended for use only in patients 18 years and older.

Do not implant these Precice devices in patients under 50 pounds or over the maximum patient weight described in the instructions for use. 

Do not implant more than two Precice devices in a patient at once. 

The device should be removed after one year.

For care of patients who currently have one of these devices and weigh less than 50 pounds or have more than two devices implanted, the health care team should assess treatment progression and consider removal of nails promptly at the end of treatment. This can minimize the potential for biocompatibility risks while also minimizing the risks associated with repetitive surgical interventions and suboptimal conversion to alternative therapies mid-treatment.

Note: Stainless steel-based Precice devices (Bone Transport, Plate, Stryde) remain recalled from the U.S. market due to adverse events related to potential biocompatibility concerns, and should not be implanted. Please continue to follow the actions in NuVasive’s recall notification.

The FITBONE intramedullary lengthening system is indicated for adult and pediatric (greater than 12 through 21 years of age) patients. It is intended for limb lengthening of the femur and tibia.

Fitbone™ Reverse Planning Method module for lengthening nails — This system requires pre-operative planning assessment, through simulation of osteotomy positioning and blocking screw placement. It requires that the implanting surgeon to be familiar with the technique for callus distraction and corrective treatments of the lower extremities and has mastered all procedures from analysis of the deformity and planning through to surgery and aftercare. It is also required of the surgeon to be familiar with the techniques for intramedullary nailing to treat bone fractures and recognized osteotomy techniques. 

FDA 501(k) Number K203399, Product Code HSB

Rationale

This evidence review was created in June 2024 with searches of the PubMed database. The most recent literature update was performed through September 30, 2024.

Evidence reviews assess the clinical evidence to determine whether the use of a technology improves the net health outcome. Broadly defined, health outcomes are length of life, quality of life, and ability to function-including benefits and harms. Every clinical condition has specific outcomes that are important to patients and to managing the course of that condition. Validated outcome measures are necessary to ascertain whether a condition improves or worsens; and whether the magnitude of that change is clinically significant. The net health outcome is a balance of benefits and harms.

To assess whether the evidence is sufficient to draw conclusions about the net health outcome of a technology, 2 domains are examined: the relevance and the quality and credibility. To be relevant, studies must represent one or more intended clinical use of the technology in the intended population and compare an effective and appropriate alternative at a comparable intensity. For some conditions, the alternative will be supportive care or surveillance. The quality and credibility of the evidence depend on study design and conduct, minimizing bias and confounding that can generate incorrect findings. The randomized controlled trial (RCT) is preferred to assess efficacy; however, in some circumstances, nonrandomized studies may be adequate. RCTs are rarely large enough or long enough to capture less common adverse events and long-term effects. Other types of studies can be used for these purposes and to assess generalizability to broader clinical populations and settings of clinical practice.

Promotion of greater diversity and inclusion in clinical research of historically marginalized groups (e.g., People of Color [African-American, Asian, Black, Latino and Native American]; LGBTQIA (Lesbian, Gay, Bisexual, Transgender, Queer, Intersex, Asexual); Women; and People with Disabilities [Physical and Invisible]) allows policy populations to be more reflective of and findings more applicable to our diverse members. While we also strive to use inclusive language related to these groups in our policies, use of gender-specific nouns (e.g., women, men, sisters, etc.) will continue when reflective of language used in publications describing study populations.

Population Reference No. 1

Intramedullary Limb lengthening System

Clinical Context and Therapy Purpose

The purpose of Intramedullary limb lenghtening devices is to provide a treatment option that is an alternative to or an improvement on existing therapies for individuals who have unequal limb lenghts. 

The question addressed in this evidence review is: Does the use of intramedulary lenghtening devices improve the net health outcome in individuals with uneven lower extremities limb lenghts?

The following PICO was used to select literature to inform this review.

Populations

The relevant population of interest are individuals who are undergoing limb lenghtening.

Interventions

The therapy being considered is Intramedullary limb lenghtening devices with intramedullary nails. 

Comparators

The following practice is currently being used for individuals who are undergoing limb lengthening: lIlizarov External Fixation Devices, Bone Shorthening, Epiphysiodesis, or Shoe Lifts.

Outcomes

The general outcomes of interest include functional outcomes, quality of life, resource utilization, and treatment-related morbidity.

Study Selection Criteria

Methodologically credible studies were selected using the following principles:

• To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs;

• In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.

• To assess long-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.

• Studies with duplicative or overlapping populations were excluded.

Review of Evidence

Systematic Review

Intramedullary Nail Versus Conventional Ilizarov Method for Lower Limb Lengthening

A systematic review and meta-analysis of the comparison of intramedullary nail versus conventional Ilizarov method for lower limb lengthening by Xu (2017) resulted in a total of 4 studies eventually satisfying the eligibility criteria, consisting of one randomized controlled trial (RCT), two clinical controlled trials and one retrospective cohort study. A total of 354 limbs were included in the study, among which 183 were lengthened over an intramedullary nail, and 171 limbs were lengthened conventionally. The mean difference (MD) was −50.21 for the external fixation index between the two groups (95% CI, −51.83 to −48.59; P < 0.00001) with high heterogeneity (I 2 = 99%); no significant difference in length was gained (MD = −0.30, 95% CI = −0.72 to 0.12; P = 0.16) with high heterogeneity (I 2 = 80%); and there was high significant difference for the consolidation index (MD = −19.97; 95% CI, −21.59 to −18.35; P < 0.00001) with high heterogeneity (I 2 = 100%). The overall rate of complications was relatively low, and differed significantly between the two groups. It was concluded that the intramedullary nail technique is superior to the conventional method in regards to the external fixation index and the consolidation index, which means that intramedullary nail is an effective technique that can decrease the time needed in external fixation.

Sheridan et al (2020) completed a systematic review and meta-analysis of the literature that compared motorized internal limb lenghtening techniques (MILL) to the alternatives. They included in their search terms as "PRECICE", "STYDE", "FITBONE" and "Ilizarov". In this study, a total of 143 limbs were lengthened using MILL techniques. These were compared with 98 limbs that were lengthened with the use of alternative techniques. The MILL cohort was found to have significantly fewer problems (p < 0.001; relative risk [RR] = 0.31; 95% confidence interval [CI], 0.19 to 0.52) and sequelae (p = 0.002; RR = 0.57; 95% CI, 0.40 to 0.81) on random-effects meta-analysis. Both deep and superficial infectious complications were fewer for MILL procedures across all of the studies. It was concluded that the MILL technique  results in less complications than the alternative methods of lengthening. ²³

Cohort Studies

Horn (2019) followed a total of  50 lengthenings (34 Precice and 16 Fitbone devices) in 47 patients (mean age 23 years [11-61]) with ≥12 months follow-up were included in this study comparing lengthening nails for limb lengthening and deformity correction in the femur and the tibia for reliability. A total of 30 lengthenings were done due to congenital and 20 because of posttraumatic deformity (21 antegrade femora, 23 retrograde femora, 6 tibiae). Initial deformities included a mean shortening of 42 mm (25-90). In 15 patients, simultaneous axial correction was done using the retrograde nailing technique. The planned amount of lengthening was achieved in all but 2 patients.There were 5 patients who underwent simultaneous axial correction showed minor residual deformity; unintentionally induced minor deformities were found in the frontal and sagittal plane. The consolidation index was 1.2 months/cm (0.6-2.5) in the femur and 2.5 months/cm (1.6-4.0) in the tibia. Two femoral fractures occurred in retrograde femoral lengthenings after consolidation due to substantial trauma. There were 8 complications, all of which were correctable by surgery, with no permanent sequela. They concluded that a controlled acute axial correction of angular deformities and limb lengthening can be achieved by a motorized intramedullary nail. ¹³

Farsetti et.al (2019) performed femoral or tibial lengthening over an intramedullary nail, according to Paley's technique, in 28 patients, followed up after a mean period of 8 years. Patients treated for lower limb discrepancy by limb lengthening over an intramedullary nail were reviewed from 5 to 11 years after healing of regenerated bone. There were 20 femurs and 8 tibiae, with average age at surgery of 14.2 years and average length inequality of 6.1 cm for femurs and 5.3 cm for tibiae. The mean lengthening was 5.8 cm for femurs and 4.8 cm for tibiae. The mean period of radiographic consolidation of the regenerated bone was 6 months for femoral lengthening and 4.5 months for tibial lengthening. At follow-up, it was observed 8 excellent results, 15 good results, 4 fair results, and 1 poor result, based on Paley's evaluation criteria. The main complications were one deep infection, one nonunion of the distracted segment, one breakage of the distal fiche of the external fixator, and one breakage of both distal locking screws of the intramedullary nail. They concluded that limb lengthening over an intramedullary nail still represents a good method to treat limb length discrepancy because it reduces the time of external fixation, prevents axial deformities and fractures of regenerated bone, and allows early rehabilitation. ²

Retrospective Case Reviews

Frommer et.al (2022) retrospectively analyzed the longitudinally maintained database of a single orthopaedic teaching hospital to identify all patients who underwent surgery for leg length discrepancy (LLD) between October 2014 and April 2019. In total, they surgically treated 323 patients for LLD of 2 cm or more. Of those 55% (177 of 323) were treated with distraction osteogenesis with magnetically driven intramedullary lengthening nails, 18% (59 of 323) with external fixation, and 27% (87 of 323) with epiphysiodesis around the knee. Based on that, 29% (93 of 323) of patients underwent unilateral femoral distraction osteogenesis with magnetically driven antegrade femoral lengthening nails and were eligible for analysis. No patient was excluded, and 3% (3 of 93) were lost before the minimum study follow-up of 2 years, leaving 97% (90 of 93) for analysis. Patients with a distal femoral deformity were treated via a retrograde femoral approach (10% [33 of 323]) or with external fixators (3% [10 of 323]) and were not included in this study. Distraction osteogenesis with magnetically driven intramedullary lengthening nails was not considered for patients with deep tissue infection, those with bone dimensions considered to be too small in relation to the available implants, and for patients younger than 8 years. This study included 90 patients (44 females, 43 left femora) treated for a median (interquartile range) preoperative LLD of 39 mm (32 to 52) at a median age of 15 years (14 to 17). The same limb lengthening system was applied in all patients. The median (IQR) follow-up was 35 months (24 to 78). Data were acquired through a chart review performed by someone not involved in the surgical care of the included patients. Data acquisition was supervised and curated by two of the involved surgeons. Accuracy was calculated as 100 – [(achieved distraction in mm – planned distraction in mm) / (planned distraction in mm) x 100] and precision as 100 – (relative standard deviation of accuracy). Treatment-associated complications were summarized descriptively and characterized as complications resulting in unplanned additional surgery or those not resulting in unplanned surgery. To analyze the risk of unplanned additional surgery by entity, they calculated odds ratios (ORs) comparing the incidence of unplanned additional surgery in the different entity cohorts with the idiopathic LLD cohort as a reference. By calculating ORs, they analyzed the risk for unplanned additional surgery depending on sex, age, surgery time, and previous lengthening. Due to the lack of long-term evidence about motorized lengthening nails remaining in situ and concerns about potential implant-related adverse effects, removal was routinely scheduled 1 year after consolidation. For implant removal, 92% (83 of 90) of patients underwent planned additional surgery, which was not recorded as an adverse event of the treatment. Ninety-seven percent (87 of 90) of patients completed lengthening with the implant remaining in situ until the end of distraction. The median (IQR) distraction length was 37 mm (30 to 45) with a median distraction index of 0.9 mm/day (0.7 to 1.0) and median consolidation index of 31 days/cm (25 to 42). The calculated accuracy and precision were 94% and 90%, respectively. In total, 76% (68 of 90) of the patients experienced complications, which resulted in 20% (18 of 90) of patients undergoing unplanned additional surgery. The most common complication overall was adjustment of the distraction rate in 27% (24 of 90) of patients (faster: 16% [14 of 90]; slower: 11% [10 of 90]) and temporary restriction of knee motion, which occurred in 20% (18 of 90) of patients and resolved in all patients who experienced it. The most serious complications were bacterial osteomyelitis and knee subluxation, which occurred in 3% (3 of 90) and 1% (1 of 90) of patients, respectively. With the numbers available, we found only one factor associated with an increased likelihood of unplanned additional surgery: Patients with postinfectious LLD had higher odds of unplanned additional surgery than patients with idiopathic LLD (7% [1 of 15] versus 50% [3 of 6], OR 14.0 [95% CI 1.06 to 185.49]; p = 0.02). The author cautioned readers this finding is fragile, and that the confidence interval suggests that the effect size estimate is likely to be imprecise, concluding that femoral distraction osteogenesis with magnetically driven antegrade intramedullary lengthening nails appears to be an accurate and reliable treatment for femoral lengthening.⁴

Iliadis et.al. (2021) completed a retrospective review of all pediatric and adolescent patients treated on a single center with intramedullary lengthening for lower limb length discrepancy using the PRECICE and STRYDE intramedullary lengthening nails between 2013 and 2019. All patients were operated by a single surgeon. Data was prospectively recorded. They reviewed nail accuracy and reliability, consolidation index, time to full weight-bearing from completion of lengthening, joint range of movement, ASAMI bone and functional scores, presence of problems, obstacles and complications, and patient reported outcome measures (PROMS). Fifty cases (43 femoral and 7 tibial nails) were performed in 42 patients (20 males, 48% and 22 females, 52%). Six patients had bilateral lengthening and 2 patients had sequential lengthening. There were 28 antegrade femoral, 13 retrograde femoral and 5 tibia PRECICE nails, 2 tibial and 2 femoral PRECICE STRYDE nails. Mean age at surgery was 15 years old (12 to 17). Mean preoperative length discrepancy was 49 mm (20 to 90). Mean achieved lengthening was 46.5 mm (20 to 80). Mean percentage lengthening was 12.6% (5% to 25%). Nail accuracy was 96% and reliability 90%. Average distraction rate was 0.92 mm/d for femur and 0.64 mm/d for tibias. Consolidation index was 28 d/cm (18 to 43) and 39 d/cm (20 to 47), respectively. Time from completion of lengthening to independent full weight-bearing as observed in clinic was 45 days (21 to 70) and 34.2 days (23 to 50), respectively. ASAMI bone and functional scores were favorable and PROMS demonstrated high patient satisfaction levels. No significant complications were observed. As per their clinical results, they obtained high patient satisfaction with intramedullary lengthening in a pediatric/adolescent population. It was highly recommended thorough preoperative preparation, patient education, and a multidisciplinary approach.¹⁴

Summary of evidence

For individuals with have comminuted fractures, nonunion fractures, congenital or aquired deformities of the lower extremity, the evidence includes systematic reviews, retrospective case reviews and cohort studies. Relevant outcomes are morbid events, quality of life, and functional outcomes. The FDA has approved intramedullary limb lengthening devices for limb lengthening, in open and closed fracture fixation, pseudarthrosis, malunions, nonunions, or bone transport of long bones in patients aged 12 and older (following the manufacturers guidelines). The evidence concludes that the application of intramedullary nail lengthening techniques provide faster results with low incidence on complications. Following initial excellent outcomes published, the use of the lengthening intramedullary nail has become accepted by many as the implant of choice in limb lengthening. The literature supports the use of ILLS as a surgical technique for the efficacy of the treatment and its cost effectiveness, even reaching the status of goldstandard for cases of femoral lenghtening²⁴. The evidence is sufficient to determine that the technology results in an improvement in the net health outcome.

Suplemental Information

National Institute for Health and Care Excellence (NICE, 2022) :

3.5 The committee noted that:

• the technology used for limb lengthening is evolving and external fixator use has become less common
• there are several devices available for use in this procedure, and they may have different efficacy and safety profiles
• assessing and managing the soft tissues is key to successful outcomes.

References

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Codes

Policy History