Development of a Small Animal Ankle Arthrodesis Model.

BACKGROUND: Our understanding of the biology of ankle arthrodesis is based largely on work in spine and long bone animal models. However, the local soft tissue and vascular anatomy of the foot and ankle is different from that of the spine. Accordingly, the objective of this study was to develop a small animal ankle arthrodesis model. METHODS: A total of 12 Lewis rats successfully underwent ankle arthrodesis with stabilization consisting of a single Kirschner wire across the prepared tibiotalar joint. Based on high nonunion rates with this initial procedure, a modification was made consisting of a second pin crossing the joint. A total of 6 rats underwent the second procedure. Radiographs were taken postoperatively and in 2-week intervals up to 10 weeks. Micro computed tomography (µCT) and histological analysis was conducted at 10 weeks to assess the fusion mass. Osseous bridging of greater than 50% across the tibiotalar joint was deemed a successful fusion. RESULTS: µCT analysis determined that 11 of the 12 rats in the single-pin cohort developed nonunions (8.3% fusion rate). In the dual-pin cohort, all 6 animals successfully fused (100% fusion rate). Histological analysis supported the radiographic imaging conclusions. CONCLUSION: While the initial procedure had a high nonunion rate, enhancing the stability of the fixation greatly increased the union rate. CLINICAL RELEVANCE: The present work demonstrates the first reliable small animal ankle arthrodesis model. We believe that this model can be used in the development of novel therapies aimed at decreasing complications and increasing fusion rates.

Impact of Vancomycin Treatment on Human Mesenchymal Stromal Cells During Osteogenic Differentiation.

BACKGROUND: Vancomycin is frequently applied locally to the operative site during foot and ankle procedures to help prevent infection. Although the efficacy of locally applied vancomycin has been demonstrated in spine surgery, there is no consensus on dosing and indication within foot and ankle surgery. Osteogenic differentiation of human mesenchymal stromal cells (hMSCs) is key to healing of both fractures and arthrodesis. The purpose of this research was to determine the impact of vancomycin on human hMSCs during the process of osteogenic differentiation. METHODS: hMSCs were cultured in osteogenic differentiation media to promote osteogenic differentiation. Cells were treated with vancomycin at differing concentrations of 0, 50, 500, and 5000 µg/mL. Viability and cell growth were assessed via LIVE/DEAD viability/cytotoxicity kit (Invitrogen, Waltham, MA) after 1, 3, and 7 days of vancomycin treatment. Differentiation and mineralization was assessed via alizarin red staining after 21 days of treatment. Mean cell viability, cell number, and mineralization were compared between treatment groups using 1-way analysis of variance and the Tukey-Kramer method for post hoc pairwise comparisons. RESULTS: At the highest concentrations of vancomycin, there was a significant reduction in cell viability and proliferation after 3 days compared with all other treatment groups. Mineralization was also significantly decreased with higher doses of vancomycin. CONCLUSION: At high concentrations, vancomycin may impair hMSC viability and osteogenic differentiation. CLINICAL RELEVANCE: Surgeons should exercise caution and consider the limited soft tissue envelope when applying vancomycin locally during foot and ankle surgery, especially during arthrodesis procedures.

Exercise-Induced Acute Bilateral Upper-Arm Compartment Syndrome.

We present a rare case of acute exercise-induced bilateral upper-arm compartment syndrome in a patient who, after a year-long hiatus from exercise, subjected his upper-extremities to the stress of over 100 pushups. The patient presented with severe pain of the bilateral biceps and triceps and complaints of dark urine. Decompressive fasciotomy was performed followed by an intensive care unit (ICU) stay for associated myoglobinuria secondary to rhabdomyolysis. The patient suffered no long-term sequelae as a result of his conditions and recovered full function of the bilateral upper-extremities. Albeit rare, acute exercise-induced compartment syndrome should be considered as a diagnosis following unaccustomed bouts of exercise.