Background: Magnetic intramedullary lengthening nails (MILNs) have gained popularity in recent years for the treatment of limb-lengthening discrepancies. We sought to catalog mechanical failures and their prevention and management in a large, single-institution series. We specifically assessed the rate of mechanical failures, the types of failures observed, and management strategies. Methods: We retrospectively reviewed 377 patients (420 limbs) who underwent limb lengthening with early (P1) or later (P2) MILN iterations with ≥12-month follow-up. Mechanical failure was defined as mechanical breakage of the instrumentation or nail and/or failure of the internal lengthening mechanism. Failure assessment was arranged by lengthening phases and was sorted with a complication classification system. All lengthening and alignment parameters were assessed radiographically. Results: Mechanical failure was observed in 40 nails (9.5%), most of which (63%) were corrected with an additional surgical procedure. The mechanical failure rate was 11.3% in P1 nails and 9% in P2 nails. Two nails failed the intraoperative distraction test, and 1 nail was found to have a broken washer during the insertion phase. Sixteen nails had mechanical failures in the lengthening phase. Some nails (8 of 16) required nail replacement surgery. Thirteen nails failed during the consolidation phase; 7 of these cases were managed by replacement with either a functional MILN or a conventional intramedullary nail. Eight failures happened during the extraction phase and were managed intraoperatively. Conclusions: A 9.5% overall rate of mechanical failure of MILNs was observed in this large series. Resolution was achieved with an additional surgery in most cases. Nail distraction and weight-bearing compliance should be closely monitored during the lengthening and consolidation phases. Nail removal can be difficult and requires a careful study of radiographs for locking-screw bone overgrowth and backup removal equipment. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Segmental bone defects of the tibia are amenable to multiple treatment options including classic bone transport, shortening and then lengthening, induced membrane technique, transport over a nail, free fibular grafting, and medial transport of the ipsilateral fibula. These treatment options have relative advantages and disadvantages, depending on defect size, soft-tissue characteristics, the presence or absence of infection, and associated morbidity. Relatively, few large comparative studies exist, and surgeons are left to their own experience and the opinion of experts within the field to guide surgical decision-making.

Previous studies on lengthening for achondroplasia have reported bilateral extensive femoral lengthening followed by bilateral extensive tibial lengthening. To decrease trauma on soft tissues and joints, we propose bilateral simultaneous moderate femoral lengthening and moderate tibial lengthening followed by a similar repeat lengthening a few years later. Fifty patients with achondroplasia underwent 65 simultaneous bilateral femoral and tibial lengthening procedures. Segment lengthening amount and adverse events were obtained from medical records. Mean follow-up after bone healing was 35.6 months. Mean tibial lengthening was 52 mm; mean femoral lengthening was 72 mm. Average healing index was 1.4 months/cm for the tibia and 1 month/cm for the femur. Mean duration of treatment with external fixation was 6.7 months (range, 4.4–10.5 months). Thirty-eight (76%) of 50 patients experienced one or more adverse events during lengthening. We observed 78 adverse events, 35 (45%) of which required additional surgical procedures. All resolved by the end of treatment. Mechanical axis deviation improved from a mean of 15 mm medially to 8 mm medially. Simultaneous lengthening of four segments in patients with achondroplasia is a feasible strategy. Compared with isolated femoral or tibial lengthening, distributing the lengthening between the femur and tibia decreases total external fixator time.

Background: Magnetic, telescoping intramedullary lengthening devices are widely used for treatment of limb length discrepancies. However, a routine radiographic review of a stainless-steel device demonstrated soft tissue and bony changes suggestive of osteolysis. Therefore, we sought to examine all patients implanted with a stainless-steel limb-lengthening nail. We specifically asked: (1) what is the incidence of periosteal reaction osteolysis? (2) Is a new biologic reaction classification system valid and reliable? and (3) Are there predictive factors for the development of osteolysis? We hypothesized that higher patient weight and femoral insertion would be risk factors for lysis, due to increased bending moments on the implants. Materials and Methods: A retrospective review of all patients implanted with a stainless-steel limb-lengthening nail between December 2018 and December 2020 was conducted at a single institution. A total of 57 nails in 44 patients were radiographically examined with an average follow-up of 6.2 months (range: 1–21 months). The incidence of osteolysis was calculated through review of patient radiographs. These were then classified according to a novel system by five fellowship-trained orthopedic surgeons with agreement assessed using an intraclass correlation coefficient (ICC). Logistic regression measured predictive factors for this phenomenon. A separate histologic analysis of two bone/soft-tissue biopsies at the time of routine explantation was conducted by an independent pathologist. Results: The incidence of periosteal reaction and osteolysis was 36.8% and 17.5%, respectively. Nails with progression to osteolysis increased to 34.6% (9/26) when examining nails with at least a 6-month follow-up. ICC testing yielded good inter-rater agreement for the novel classification system (average measure: 0.860, 95% confidence interval 0.828–0.888). Age >16 years (P = 0.024) and body weight >150 pounds (P = 0.038) were predictors of osteolysis. Histologic analysis of the biopsies demonstrated an abundance of particulate debris suggestive of chromium reaction. Conclusions: The modular junction of a stainless-steel lengthening device is susceptible to osteolytic changes, and this appears to be associated with increased age and weight. This phenomenon has an apparent time dependence: osteolysis increases with greater follow-up.

In situ stabilization is a widely accepted treatment for slipped capital femoral epiphysis (SCFE) despite risks of avascular necrosis (AVN) and femoroacetabular impingement (FAI). The modified Dunn procedure with surgical hip dislocation attempts to maintain epiphyseal perfusion and allows anatomic epiphyseal repositioning, theoretically reducing AVN and FAI risks. We systematically evaluated the literature, elucidating overall and stability-stratified rates of AVN following the modified Dunn procedure, and revision rates in non-AVN patients. Using Ovid and MEDLINE (PubMed), studies involving the modified Dunn procedure were evaluated for age, stability, preoperative slip (Southwick) angle, ROM at follow-up, outcome metrics, and revisions. Utilizing a random effect model of proportions, we determined overall and stability-stratified AVN rates, and revision rates in patients without AVN.673 patients (688 SCFEs) who underwent modified Dunn procedure were included. Overall AVN rate was 14.3% with a 95% Confidence Interval (CI) of 9.3 to 20.2%. AVN rate in stable slips was 10.9% (95% CI: 6.0 to 17.1%) and 19.9% (95% CI: 12.8% to 28.1%) in unstable slips. Revision rate in non-AVN patients was 13.3% (95% CI: 8.3% to 19.2%). Fixation failures occurred following K-wire or small-caliber (90 points). Mean HHS was 98.9 points (range of means: 86 to 99 points) in stable cases, and 90.5 points (range of means: 73 to 98 points) in unstable cases. Patients undergoing modified Dunn procedure had excellent clinical outcomes and low incidences of AVN. Further studies are needed to determine if modified Dunn osteotomy with surgical hip dislocation is a viable alternative to in situ pinning for treatment of severe SCFE.

Summary: The challenging problem of long bone infection and limb length difference cannot be addressed using only an antibiotic-coated nonmagnetic static nail. The combined use of resorbable calcium sulfate and magnetic lengthening nails offers a possible solution to this dilemma, as well as for infected nonunions that require compression. We present a combined technique to treat or prevent infection using femoral or tibial intramedullary antibiotic delivery with an absorbable calcium sulfate depot and concomitant internal lengthening or compression using a nail. Adequate débridement is required in cases of established infection and is a prerequisite for this technique.