Motorized Intramedullary Lengthening Nails: Outcomes and Complications

Chronic knee pain following infrapatellar/suprapatellar magnetic intramedullary lengthening nails versus external fixators in limb length discrepancy: A retrospective review

Aims & objectives

Prior to the popularization of magnetic intramedullary nails (MILNs), gradual deformity correction using external fixation was the norm in limb lengthening. Trauma literature has shown MILN via a suprapatellar approach (SP) to be associated with less knee pain than either an infrapatellar entry (IP) or external fixation. Yet, no research has investigated chronic knee pain and MILNs. We assessed differences in chronic knee pain following lengthening via an IP or SP approach with an MILN versus external fixation.

Materials & methods

We reviewed 147 limbs (55 MILN/IP, 22 MILN/SP, 71 external fixator) in 124 patients who underwent tibial lengthening with ≥12 months follow-up between February 2012 and July 2020. Knee pain was assessed pre- and postoperatively at 6 and 12 months, with the Lysholm Knee Scoring Scale (LKSS) and numeric pain scale (0-10). Differences in knee pain outcomes were compared across methods, with subgroup analysis of MILN/SP and MILN/IP.

Results

Mean LKSS was 96.3 for external fixation and 88.5 for MILN (P = .011). In the MILN subgroups, mean LKSS was 91.7 for IP and 85.3 for SP. The IP group reported a lesser mean pain score (0.6 versus 2.1) at 12 months. Bilateral nail recipients demonstrated no knee pain differences versus unilateral. At 12 months postoperative, external fixation had better knee outcomes.

Conclusion

Tibial lengthening with external fixation was associated with less chronic anterior knee pain and better functional outcomes than MILN overall. In terms of MILN approach, IP surpassed SP on subjective pain scores. Larger tibial lengthening and knee pain studies are warranted.

Fluoroscopy-free distal screw locking in intramedullary nailing: A retrospective study

Intramedullary nailing is a common orthopedic procedure, but current methods for distal screw locking have several limitations. This study introduces and evaluates a novel technique that aims to overcome these challenges. The findings were statistically significant, with P-values set at .05. Compared to the traditional method, the novel technique demonstrated several advantages. Mean operation times were reduced to 1.2 hours for the new method, in contrast to 1.5 hours for the control group. Hospital stays also favored the new technique, with a mean duration of 2 days, while the control group averaged 3 days. A significant benefit was the marked decrease in radiation exposure, with the new technique eliminating radiation entirely, recording 0.0 mSv compared to the control group's 2.5 mSv. The procedure's success, gauged by the accurate positioning of screws, was higher for the new technique at 92% versus the control's 78%. Furthermore, complication rates were notably lower in the new method, with a 6% incidence compared to 16% in the traditional approach. While the data suggest that the new technique holds promising advantages, such as reduced operation times, decreased radiation exposure, and fewer complications, it is essential to conduct more extensive research for comprehensive validation. Despite the optimistic results, the study acknowledges the need for larger-scale trials to solidify these findings.

An update on the intramedullary implant in limb lengthening: A quinquennial review Part 1: The further influence of the intramedullary nail in limb lengthening

The goal of limb lengthening is to restore length to bone, safely stretch soft tissues and improve quality of life with minimal complications. Traditionally this was achieved with the use of external fixators, associated with complications related to pin site tethering and infections, joint stiffness and regenerate deformity and fracture following frame removal. The duration of treatment also impacts on patient mental health and well-being. In order to reduce external fixator time, intramedullary nails have been introduced as an adjunct, either at the initial surgery or after completion of lengthening. Complications related to the external fixator still remained and innovation has led to the popularisation of the intramedullary lengthening nail. The lengthening mechanism of the nail can be divided into those with ratchet systems and those driven by motors. In the ratchet group, patients are required to manually rotate their limb, with movement at the osteotomy site, in order to create forward movement. This was often associated with pain, and in some cases led to the requirement of general anaesthesia to enable rotation and continuation of lengthening. Further issues were reported related to lengthening rate control. Once the nail had lengthened sufficiently for the osteotomy to disengage, rapid lengthening termed a 'runaway' nail could occur. The nails were limited to forward movement, and once length was gained it could not be retracted, leading to poor regenerate formation and soft tissue contractures. The introduction of the Fitbone implant utilised a transcutaneous electrical conduit, powered by a high frequency electrical signal, enabling more control over the lengthening. The Precice intramedullary lengthening system is controlled by the use of an external device with two rotating neodymium magnets, which produce rotation of a third magnet in the nail. By altering the direction of the magnet rotation, the lengthening can be controlled both forwards and backwards with sub-millimetre precision. 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 aim of this article comes in two parts. The first to highlight the latest research and clinical results in the last five years using an intramedullary implant during limb lengthening, and the second to report the outcome in extended surgical indications and further implant innovation.

An Update on the Intramedullary Implant in Limb Lengthening: A Quinquennial Review Part 2: Extending Surgical Indications and Further Innovation

The use of the intramedullary lengthening nail has gained in popularity over the last decade. The reduction in complications associated with the use of external fixators and excellent patient outcomes has resulted in the largest change in management of limb length discrepancy since the concept of distraction osteogenesis was accepted by the Western world in the 1980s. Success following "simple" limb lengthening has led to surgeons extending the indications for the lengthening nail, including different bone segments, lengthening associated with potential joint instability and lengthening combined with acute deformity correction. There has been a drive for further implant modification to reduce complications, and enable full weight bearing during the lengthening process. This would offer the opportunity to consider simultaneous limb lengthening. The aim of this review is to evaluate the literature published over the last five years and highlight important learning points and technical tips for these expanding indications.

Use of the Pixel Value Ratio Following Intramedullary Limb Lengthening: Uncomplicated Full Weight-bearing at Lower Threshold Values

Aims

The pixel value ratio (PVR) can be used to assess regenerate consolidation after lengthening and guide advice for full weight-bearing (FWB). This study aimed to analyse the PVR in adults having femoral lengthening, the time to FWB and compare findings with the reported values in the literature.

Materials and methods

A retrospective database review identified 100 eligible patients who underwent lengthening using the PRECICE nail (68 antegrade and 32 retrograde). The PVR was calculated in each cortex on plain radiographs at every visit. The ratio between the regenerate and an average from the adjacent normal bone was calculated and plotted against the clinical decision to allow FWB.

Results

Eighty-seven patients (58 men and 29 women) were assessed; eleven had bilateral lengthening and two patients underwent lengthening twice. The median age was 30.5 years. The underlying cause of shortening was post-traumatic in 46%, with the remaining due to a wide variety of causes, including congenital 16%, syndromic 12% and other causes. The median lengthening achieved was 45 mm, at a median of 57.5 days. The PVR increased with each visit (p <0.0001). FWB was allowed at a median of 42 days after the last day of lengthening, with PVR values of 0.83, 0.84, 0.93 and 0.84 for the anterior, posterior, medial and lateral cortex noted, respectively (average 0.85). There were no implant failures, shortening or regenerate fractures. No differences were detected between antegrade and retrograde nails or with lengthening greater or less than 45 mm. One surgeon allowed earlier FWB at median 31 days with no nail failures.

Conclusion

PVR is a valuable tool that quantifies regenerate maturity and provides objectivity in deciding when to allow FWB after intramedullary lengthening with the PRECICE nail. FWB was permitted at an earlier time point, corresponding with lower PVR values than have been reported in the literature and with no mechanical failure or regenerate deformation.

How to cite this article

Elsheikh AA, Wright J, Stoddart MT, et al. Use of the Pixel Value Ratio Following Intramedullary Limb Lengthening: Uncomplicated Full Weight-bearing at Lower Threshold Values. Strategies Trauma Limb Reconstr 2022;17(1):14–18.