Risk Factors for Nonunion in Pediatric Lateral Column Lengthening (Mosca) Procedures

Abstract

Category: Hindfoot Introduction/Purpose: The Evans/Mosca procedure remains the most utilized extra-articular osteotomies for correction of pes planus. This desired lengthening is created by inserting a graft in the anterior aspect of the calcaneus through a complete transverse osteotomy. Failure of conservative methods, particularly for rigid pes planus, is a primary consideration for surgical management. Complications of the Evans procedure include delayed union, nonunion, malunion, subluxation of the calcaneocuboid joint, and persistent lateral column pain. Our study analyzes risk factors for development of non-union. Methods: After IRB approval 120 patients charts and 157 feet were analyzed for incidence of non-union which was defined by clinical and radiographic evidence of absence of union >6 months. Delayed union was diagnosed if there was clinical evidence of healing without complete union at >6 months. Exclusion criteria included age >18 and revision lateral column lengthening. Patients' medical records were reviewed for basic demographics, complications, and surgical technique. Results: The cohort consisted of 75 females (47.8%) and 82 males (52.2%). The median age was 12 with an interquartile range (IQR) of 3. A total of 6 patients (3.7%) had wound complications or nerve injury. Nonunion occurred in 7 of 157 feet (4.5%) with 2 of 157 feet (1.3%) experiencing delayed union. The median age for patients with nonunion was significantly higher than those who achieved union (13.2 (IQR 2.75) vs. 11.2 (IQR 3) respectively). The fixation construct used was associated with increased risk of nonunion. Patients with screw fixation had the highest rate of nonunion at 50% (2/2) compared to pin and/or staple fixation at 6.8% (5/73), no fixation at 4% (3/75), and plate fixation at 0% (0/2). Both delayed union patients were treated with ultrasound bone stimulation, both patients were able to achieve complete union. Revision was attempted in 5/7 nonunions with all operative patients achieving union. Conclusion: Our study analyzed risk factors for developing non-union in patients undergoing calcaneal lengthening osteotomy for pediatric pes planus. We found age at time of surgery and graft fixation method to be significant risk factors for development of non-union. Our study highlighted that those patients who had non-union was on average >2yrs older at time of surgery. Overall, lateral column lengthening is a well-tolerated procedure with a complication rate, including non-and delayed union, of 10.8%. Surgeons should be aware, in the largest cohort of pediatric Evans/Mosca procedures to date, patient age and type of fixation were associated with nonunion.