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BACKGROUND: Different surgical methods for epiphysiodesis of limb length discrepancy (LLD) have been described. Although these methods are variably effective, they are associated with morbidity (pain and limp) and potential complications. Microwave ablation is a less-invasive opportunity to halt growth by selectively destroying the growth plate via thermal energy to treat LLD in children. QUESTIONS/PURPOSES: In this proof-of-concept study using an in vivo pig model, we asked: (1) What is the durability of response 2 to 4 months after microwave ablation of the tibial growth plate as measured by length and angulation of the tibia via a CT scan? (2) Was articular cartilage maintained as measured by standard histologic staining for articular cartilage viability? METHODS: To develop an in vivo protocol for microwave ablation, we placed microwave antennas adjacent to the proximal tibia growth plate in the cadaveric hindlimbs of 18 3-month-old pigs. To determine the suitable time, we varied ablation from 90 to 270 seconds at 65-W power settings. After sectioning the tibia, we visually assessed for discoloration (implying growth plate destruction) that included the central growth plate but did not encroach into the epiphysis in a manner that could disrupt the articular surface. Using this information, we then performed microwave ablation on three live female pigs (3.5 to 4 months old) to evaluate physiologic changes and durability of response. A postprocedure MRI was performed to ensure the intervention led to spatial growth plate alterations similar to that seen in cadavers. This was followed by serial CT, which was used to assess the potential effect on local bone and growth until the animals were euthanized 2 to 4 months after the procedure. We analyzed LLD, angular deformity, and bony deformity using CT scans of both tibias. The visibility of articular cartilage was compared with that of the contralateral tibia via standard histologic staining, and growth rates of the proximal tibial growth plate were compared via fluorochrome labeling. RESULTS: Eighteen cadaveric specimens showed ablation zones across the growth plate without visual damage to the articular surface. The three live pigs did not exhibit changes in gait or require notable pain medication after the procedure. Each animal demonstrated growth plate destruction, expected limb shortening (0.8, 1.2, and 1.5 cm), and bony cavitation around the growth plate. Slight valgus bone angulation (4º, 5º, and 12º) compared with the control tibia was noted. No qualitatively observable articular cartilage damage was encountered from the histologic comparison with the contralateral tibia for articular cartilage thickness and cellular morphology. CONCLUSION: A microwave antenna placed into a pig's proximal tibia growth plate can slow the growth of the tibia without apparent pain and alteration of gait and function. CLINICAL RELEVANCE: Further investigation and refinement of our animal model is ongoing and includes shorter ablation times and comparison of dynamic ablation (moving the antennae during the ablation) as well as static ablation of the tibia from a medial and lateral portal. These refinements and planned comparison with standard mechanical growth arrest in our pig model may lead to a similar approach to ablate growth plates in children with LLD.
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INTRODUCTION: This study investigates how previous simulation training and clinical experience affects trainee performance when manipulating a foot, applying a Ponseti clubfoot cast, and performing an Achilles tenotomy on a clubfoot simulator. METHODS: Sixty-four Accreditation Council for Graduate Medical Education orthopaedic trainees participated in the 2017 to 2018 Top Gun (TG) skills competition at the International Pediatric Orthopaedic Symposium. Trainees were judged by expert pediatric orthopaedic surgeons on how they manipulated a clubfoot model, applied a cast, and performed a simulated tendoachilles tenotomy (TAT). An analysis was done to correlate the test variables with a contestant's TG Ponseti score. RESULTS: Twenty-one contestants with previous residency training using synthetic clubfoot models scored higher (P = 0.007) than those trainees without training. Trainees who had applied >10 clubfoot casts and who participated in >10 TATs in training also scored higher (P = 0.038 and P = 0.01, respectively). Thirteen contestants who had previously attended an International Pediatric Orthopaedic Symposium meeting and seven contestants who attended a American Academy of Orthopaedic Surgery clubfoot workshop scored higher (P = 0.012 and P = 0.017 respectively). DISCUSSION: Clinical and previous simulation experience related to the Ponseti method correlated with improved performance on our Ponseti simulation. Trainees who had previous experience with >10 clubfoot casts and >10 TATs scored higher during TG than less experienced trainees.
