Z-cut Osteotomy for Correction of Adult Acquired Pes Planovalgus Deformity

Abstract

Category: Ankle Introduction/Purpose: Medial displacement calcaneus tuberosity osteotomy and anterior process lengthening calcaneus osteotomy are traditional single-plane osteotomy techniques used in adult acquired flatfoot deformity reconstruction. More recently, three plane step-cut osteotomies were described for each of these and offer improved rotational stability via the horizontal limb. However, a major technical challenge is achieving a sufficiently long horizontal limb to correct deformity through lengthening without losing bony apposition. Combining the anterior process and tuberosity step-cuts using an elongated horizontal limb (“Z-cut”, Figure 1) alleviates this technical challenge, creates a very large surface area for bony healing, and utilizes a single incision. We hypothesized that the Z-cut osteotomy achieves clinical and radiographic flatfoot deformity correction with a high union rate. Methods: This was an IRB-approved retrospective study of 17 patients who underwent Z-cut osteotomy for treatment of moderate to severe symptomatic adult acquired flatfoot deformity, Stage IIB. Mean follow up was 8.3 months. Radiographic correction was assessed via weight bearing radiographs taken pre-operatively and at a mean of 26 +/- 2 weeks post operatively. Measurements included Meary’s angle (talo-1st metatarsal angle), talonavicular joint (TN) uncoverage percentage, TN incongruency angle, medial cuneiform to fifth metatarsal height, and calcaneal pitch. Union rates, calcaneocuboid joint arthritic changes and clinical outcomes via Foot Function Index (FFI) score were assessed preoperatively and at a mean of 29 months following surgery. Paired t-test was used to compare both clinical and radiographic outcomes with statistical significance set at p<0.05. Results: Nine patients returned an FFI questionnaire with a mean improvement of 52.1 to 10.3 (p = .002). Calcaneal pitch improved from 13.2 to 15.3 (p = .004), medial cuneiform/5th metatarsal distance improved from 13.3 to 18.5 (p = .004), TN coverage angle improved from 22.4 to 9.7 (p < .001), TN uncoverage % improved from 34.3 to 21.2 (p <.001), TN incongruency angle improved from 39 to 20.1 (p < .001). Deformity correction was well maintained in 14 of 17 patients at final follow up. Union rate of the osteotomy was 100%. Three patients had symptomatic hardware initially, one patient required removal of hardware. One patient developed a superficial infection that cleared. Another patient developed peroneal tendonitis, which resolved with corticosteroid injection. Conclusion: The Z-cut osteotomy is a novel, technically simplified, single incision, single osteotomy alternative to previously described double calcaneus osteotomy techniques for reconstructing flexible moderate to severe adult acquired flatfoot deformity which offers comparable short term clinical and radiographic outcomes with acceptably low complications.