|Year : 2022 | Volume
| Issue : 1 | Page : 12-16
Use and safety of the precice antegrade femoral nail in pediatric patients
Adam D Geffner, Taylor J Reif, Austin T Fragomen, S Robert Rozbruch
Limb Lengthening and Complex Reconstruction Service, Hospital for Special Surgery, New York, NY, USA
|Date of Submission||27-Apr-2022|
|Date of Decision||18-May-2022|
|Date of Acceptance||19-May-2022|
|Date of Web Publication||30-Jun-2022|
Adam D Geffner
49 Westmount Drive Livingston, New Jersey 07039
Source of Support: None, Conflict of Interest: None
Context: The Precice internal magnetic lengthening nail is used commonly for adult femur lengthening given its accuracy, precise control of lengthening, and patient comfort throughout the process. The nail is not currently approved by the Food and Drug Administration (FDA) for use in children, although many practices continue to use it off label. Aims: We aim to support the notion that the implant is efficient, reliable, and safe for femur lengthening in skeletally immature pediatric patients. Subjects and Methods: We performed a retrospective chart review of all skeletally immature patients who underwent treatment with a precice antegrade femoral nail to help establish the nail's safety and efficiency in this population. Results: We implanted 30 precice antegrade femoral nails (all trochanteric entry) in 25 patients (11 males, 14 females). The average lengthening goal for all surgeries was 47.62 mm (15 mm to 80 mm), and the average length achieved was 47.63 mm (15 mm to 80 mm). Twenty-four out of 25 patients (96%) achieved their lengthening goal within 5 mm. Average distraction rate was 0.97 mm/day (0.75 mm/day to 1 mm/day), and average bone healing index (time to consolidation/cm lengthened) was 19.69 days/cm (13.77 days/cm to 35.33 days/cm). Three patients experienced complications that required additional surgery, including a hip and knee flexor tendon lengthening, guided growth to correct a knee flexion contracture, and bilateral exchange nailing for implant fracture and delayed union. No patients experienced avascular necrosis of the hip, and all complications were ultimately resolved without permanent deficits. Conclusions: The precice antegrade femoral nail can safely and efficiently manage large lower extremity lengthening in skeletally immature children. Concurrent angular or rotational deformity correction was also possible, and postoperative complications were infrequent and manageable.
Keywords: Femur lengthening, limb lengthening, precice internal lengthening nail, skeletally immature
|How to cite this article:|
Geffner AD, Reif TJ, Fragomen AT, Rozbruch S R. Use and safety of the precice antegrade femoral nail in pediatric patients. J Limb Lengthen Reconstr 2022;8:12-6
| Introduction|| |
Since the principles of distraction osteogenesis were first pioneered by Ilizarov in the 1950s, limb lengthening techniques have been continuously refined and improved to optimize safety, efficiency, feasibility, and patient satisfaction. While external fixators have long served as the benchmark for limb lengthening, recent advances have given rise to the motorized internal lengthening nail, which avoids many of the drawbacks associated with external fixation. Among modern internal lengthening nails, the telescopic, magnetically-controlled precice intramedullary (IM) nail has become an extremely popular limb lengthening tool given its accuracy, precise control of lengthening, and patient comfort throughout the lengthening process.,
While the success of the Precice nail in adult populations has been well documented, literature reporting its use in children is scarce, and there is skepticism regarding the nail's safety in younger patients. Potential risks to the proximal femoral blood supply and growth plate of the greater trochanter have contributed to this sentiment and are part of the reason why the nail is not currently Food and Drug Administration (FDA) approved for use in children. Despite these concerns, many practices continue to use the Precice nail in children off label. We aim to support the notion that the implant is efficient, reliable, and safe for femur lengthening in skeletally immature pediatric patients.
| Subjects and Methods|| |
After institutional review board approval was obtained, we included patients in our surgical database who:
- Were skeletally immature at the date of surgery (defined as males 16 years and younger, females 14 years and younger)
- Underwent femur lengthening using an antegrade precice nail
- Had follow-up after the date of consolidation.
Our surgical database and electronic medical record system were used to review and document patient demographics, etiology of a discrepancy, preoperative radiographic measurements, implant dimensions, lengthening goal, distraction rate, length achieved, bone healing index (BHI), postoperative radiographic measurements, and postoperative complications.
Preoperative evaluation included a complete lower extremity physical exam and a standing bilateral hip-to-ankle radiograph with leg lengths equalized by blocks. AP and lateral X-rays of the short femur were obtained as well for preoperative planning of the implant. The radiographs were measured and analyzed by the treating surgeon to document the limb and segment length discrepancies, joint orientation angles, and mechanical axis deviation (MAD). If significant rotational deformity was suspected on clinical exam, the patient received a computerized tomography (CT) scan to further assess the malalignment. Surgical details, major risks, and postoperative routines were reviewed with the parents and patient before surgery.
All surgeries were performed at a single institution by fellowship-trained orthopedic surgeons. Nail dimensions and osteotomy location were determined based on preoperative radiographic measurements of bone length and IM canal diameter. The multiple drill hole technique was used to prepare for the osteotomy in the mid-diaphyseal segment of the femur. Trochanteric entry nails were used in all patients to reduce the risk of avascular necrosis (AVN) of the femoral head. The nail entry point was templated on preoperative radiographs and was usually at the tip of the greater trochanter. Flexible reamers were used to widen the IM canal 2 mm greater than the planned diameter of the nail. Rotational markers were placed proximal and distal to the osteotomy site either parallel or divergent at the planned correction angle using a goniometer. The transverse osteotomy was completed using osteotomes to connect the drill holes. The nail was locked with attention paid to the rotational markers. All patients underwent a transverse iliotibial band release at the distal femur metaphyseal level to help prevent knee contracture during lengthening. The location of the nail's internal magnet was identified using fluoroscopy and marked on the skin.
During the postoperative hospital stay, patients were monitored for any immediate complications. Physical therapists taught patients the weight-bearing restrictions using an analog scale and provided instructions for joint range of motion exercises to perform daily. Patients and parents were taught how to use the at-home external magnet controller. Distraction began on a postoperative day 5 at a rate of 1 mm per day in four increments for most patients. During the distraction, patients followed up every 2 to 3 weeks. During consolidation the follow-up interval was 3 to 4 weeks. At each follow-up visit, the attending surgeon performed clinical and radiographic examinations to monitor compliance with the treatment plan, distraction length, regenerate quality, implant integrity, joint range of motion, pain, and any other postoperative complications. All relevant updates to the plan and radiographic measurements were documented. Consolidation of the regenerate was achieved when three of four cortices had bridging bone at least 2 mm thick. [Figure 1] demonstrates the preoperative deformity, lengthening process, and radiographic outcome of a patient in our study group [Figure 1]. [Figure 2] demonstrates the clinical improvement of another study patient [Figure 2].
|Figure 1: Preoperative (a), 2-month postoperative (b), and 13-month postoperative (c) AP radiographs showing correction of a 28 mm direct limb length discrepancy with a precice antegrade femoral nail. Valgus deformity was concurrently corrected with distal femoral hemiepiphysiodesis. A sleeper plate was used in anticipation of potential valgus rebound|
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|Figure 2: Preoperative (a) and 6-month postoperative (b) clinical photographs of a different patient showing correction of a 26 mm direct limb length discrepancy with a precice antegrade femoral nail|
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| Results|| |
We implanted 30 precice antegrade femoral nails in 25 patients (11 males, 14 females), with an average follow-up of 18.24 months. The average age at surgery was 13.55 years for males (8 years to 15 years), and 11.93 years for females (8 years to 14 years). Seven patients had closed greater trochanteric physes and distal femoral physes at the date of surgery. One patient had open distal femoral physes, and a closed greater trochanteric physis. These patients met our age cutoffs and posed very similar challenges to skeletally immature patients. Therefore, they were included in our analysis. Two patients presented with trauma-induced limb length discrepancies, eight presented with limb length discrepancies related to Russell–Silver syndrome (RSS), 10 presented with non-RSS congenital limb length discrepancies, and five presented with congenital short stature (CSS). Seven patients (all with RSS) had undergone growth hormone treatment immediately before surgery. All seven of these patients had open growth plates at the date of surgery. Three patients (three limbs) underwent hemiepiphysiodesis to correct coronal plane deformity at the time of nail implantation. Two patients (four limbs) underwent acute rotational deformity correction at the time of nail implantation. This data, along with nail dimensions, are summarized in [Table 1]. All 30 nails were trochanteric entry [Table 1].
The average preoperative direct limb length discrepancy (each limb length was measured from the top of the femoral head to the distal tip of the tibia) for unilateral lengthening patients was 32.1 mm (15 mm to 91 mm), and the average postoperative direct limb length discrepancy for these patients was 8.33 mm (0 mm to 32 mm). One patient was intentionally overlengthened by 10 mm. The average lengthening goal for all surgeries was 47.62 mm (15 mm to 80 mm), and the average length achieved was 47.63 mm (15 mm to 80 mm). Twenty-four out of 25 patients (96%) achieved their lengthening goal within 5 mm. One patient electively stopped lengthening 7 mm short of his goal due to developing knee stiffness. Average distraction rate was 0.97 mm/day (0.75 mm/day to 1 mm/day), and average BHI (days from surgery to consolidation/cm lengthened) was 19.69 days/cm (12.83 days/cm to 32.67 days/cm). The average BHI for patients receiving growth hormone treatment was 21.44 days/cm (16.67 days/cm to 35.33 days/cm), and the average BHI for non-growth hormone patients was 19.15 days/cm (13.77 days/cm to 32.78 days/cm). There is no significant difference between these two means (P = 0.40). Among the three patients who underwent concurrent angular deformity correction, the average MAD improved from 15.67 mm (14 mm to 18 mm, lateral to the midline) preoperatively to 3.67 mm (0 mm to 11 mm, lateral to the midline) postoperatively [Table 2].
One patient rebounded into valgus (18 mm MAD) after hardware removal, raising the average postoperative MAD to 9.67 mm lateral to the midline. Among the two patients who underwent concurrent rotational deformity correction, the average intraoperative correction was 12°. Although postoperative CT scans were not performed on these patients, neither patient reported any issues or complications relating to the rotational correction. As a result of the correction, one patient's prone external rotation improved from 20° to 30° bilaterally with a concurrent improvement in foot progression angles from negative 5° to 0° bilaterally. The other patient's foot progression angles improved from negative 10° to 0° bilaterally. Twenty-three out of 30 nails were removed at the time this study was conducted, with an average time to removal of 11.15 months. There were no complications associated with hardware removal.
Three patients (12%) experienced complications requiring additional surgery. One patient had bilateral hip and knee flexion contractures of 10°–20° refractory to physical therapy that required hip flexor and hamstring lengthening along with the removal of symptomatic distal locking screws. One patient experienced a knee flexion contracture and quad weakness that prompted anterior distal femur-guided growth. One CSS patient experienced a delayed union and broken nail on the left side, and subsequently delayed union on the right side. Both precice nails were exchanged for static nails and the bones went on to unite. This patient also developed a Clostridium difficile infection after the initial nail placement (following a prolonged course of doxycycline for acne preoperatively) and then a Staphylococcus epidermidis infection following the second exchange to a static nail. He also developed a left-sided deep vein thrombosis (DVT) during distraction after an international flight. All complications in two out of these three patients were ultimately resolved. The patient who underwent anterior distal femur-guided growth only followed up once shortly after the additional surgery, so we cannot determine if her knee flexion contracture and quad weakness were fully corrected. Nonoperative problems included five instances of soft-tissue tightness and one dysfunctional magnet that led to consolidation during a planned over-distraction to account for future growth. Soft-tissue tightness improved with home exercises, formal physical therapy, or slowed lengthening. No patients experienced AVN of the femoral head, and no significant proximal femoral deformity was introduced as a result of lengthening. The average absolute value of change in neck-shaft angle was 1.7° (0° to 5°).
| Discussion|| |
The goal of limb lengthening is to achieve the desired amount of length while minimizing complications and maximizing patient satisfaction, especially in the pediatric population. The results of this study demonstrate that 96% of patients achieved their lengthening goal within 5 mm and that patients healed with an excellent BHI of 19.69 days/cm. This illustrates that the precice antegrade femoral nail is an effective lengthening tool in skeletally immature populations. The average residual limb length discrepancy of 8.33 mm seems significant, but instead exemplifies one patient who was over lengthened ten mm to account for future contralateral growth, and one patient who finished with the nail side 32 mm short after 70 mm of lengthening. This patient was also planned to undergo lengthening of the ipsilateral tibia.
The low average BHI is likely attributed to the increased healing potential of the pediatric population as well as the antegrade femur approach to lengthening, which has been shown to have a lower BHI when compared to the tibia and retrograde femur lengthening.,, It was important to separately evaluate the effect of growth hormone on the seven patients (seven limbs) who had undergone growth hormone therapy before surgery. Growth hormone has been shown to have positive effects on fracture healing and bone metabolism, and could conceivably have reduced time to consolidation in these seven patients. However, the average BHI for growth hormone patients was not statistically different than the average for non-growth hormone patients. The growth hormone may have counteracted the congenital nature of these patients' condition, which has been shown to slightly increase BHI when compared to noncongenital conditions. Other studies have reported on these differences, although their results are not statistically significant.,
The BHI in this study is in line with other studies of the precice internal lengthening nail in children. Iliadis et al. reported an average BHI of 28 days/cm across 43 femoral precice lengthenings in children younger than 18 years. BHI and consolidation were defined exactly as we define them. Tillotson et al. reported an average BHI of 24.1 days/cm across 15 femoral precice lengthenings in children 18 years and younger, although a definition of consolidation was not provided. Both studies include antegrade and retrograde nails, which may be the reason for their increased BHI when compared to our results. These bone healing indices are lower than the BHI (65 days/cm) reported in a similar adult study that included antegrade and retrograde lengthening.
The rate of postoperative complications requiring additional surgery was low, but the number of patients who experienced soft-tissue tightness or contractures cannot be discounted. Joint contracture and stiffness are well-known, relatively common risks of limb lengthening surgery with potentially disastrous effects. Prophylactic release of the iliotibial band during nail implantation is a crucial first step in the prevention of knee flexion contractures and was carried out in every study patient. Joint range of motion should be closely monitored throughout treatment so that physical therapy regiment and distraction rate can be adjusted if needed. If significant contractures do develop, additional surgery may be required, as was the case in two of our study patients. The third patient with complications experienced multiple rare complications of lengthening and orthopedic surgery in general, including C. difficile infection, DVT in a pediatric patient, and infection of a lengthening site. None of these are likely related to the precice nail itself, and risk factors for C. difficile (prolonged antibiotics) and DVT (international flight) did exist. The infected lengthening site during the exchange nail procedure was detected on routine cultures without the presence of purulence. It was the only infection of the series, and other series of lengthening nails show similarly low infection rates. This case was an outlier and had no permanent impairment, but highlights the need for vigilant assessment of complications postoperatively.
Other pediatric precice studies have also reported favorable rates of complications and soft-tissue tightness. Iliadis et al. noted seven instances of joint stiffness that resolved without surgical intervention across 50 cases (they do not specify whether these were associated with tibial or femoral lengthening). They also reported one removal of locking screws due to discomfort, one bilateral knee flexion deformity correction, and one hardware exchange due to periprosthetic fracture across 43 femoral lengthenings. Across 13 precice lengthenings, Hammouda et al. reported one patient who experienced hip subluxation and delayed union, one patient who experienced delayed union, and one who experienced premature consolidation and shutdown of the nail mechanism. Tillotson et al. reported only one instance of soft-tissue contracture that resolved with physical therapy. Although this lengthening was stopped 15 mm short of the preoperative goal, it was the only adverse event reported across 15 femur lengthenings.
Another significant takeaway from our results is that we encountered no episodes of AVN of the femoral head, a known complication of pediatric IM nailing. Other studies have shown that if a trochanteric nail is used for skeletally immature femoral lengthening, blood supply to the femoral head is at little to no risk. The trochanteric entry approach avoids branches of the medial femoral circumflex artery and reduces the likelihood of AVN. Our results further support this notion and help establish the safety of the precice nail in children. Similarly, there was no indication that the femoral neck-shaft angle changed significantly as a result of crossing the greater trochanter apophysis, contributing to the idea that nail insertion through the lateral aspect of the greater trochanter does not pose a risk to proximal femoral angulation. Although a paired t-test of means indicated a statistically significant change in neck-shaft angle (P < 0.001), we do not believe this change is clinically significant, as it follows the trend of decreasing neck-shaft angle with increasing age when approaching skeletal maturity. We would not expect the neck-shaft angles to change in the seven patients with closed growth plates and one patient with a closed greater trochanteric growth plate, but their femoral heads may have still been vulnerable due to incomplete maturation of the proximal femoral vasculature.
Overall, the results of this study illustrate that the precice antegrade femoral nail is a safe and effective tool for managing large lower extremity lengthening in skeletally immature children. Postoperative complications were infrequent and manageable, and concurrent deformity correction was possible. Future studies should continue to investigate the safety of the precice nail in children so that it may be FDA approved for this population.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]