Outcomes and Complications of 1st Tarsometatarsal Plantarflexion Bone Block Arthrodesis with a Pre-contoured Allograft Wedge: 2-year Follow-up

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Instability and collapse of the medial longitudinal arch and structural incompetence of the first ray have been linked to various conditions. These include, but are not limited to, progressive collapsing foot deformity (PCFD), hallux valgus (HV), and midfoot osteoarthritis (OA). More recently, an innovative approach combing the biomechanical advantages of the Lapidus procedure and Cotton osteotomy were described in the literature.1 Early follow up results showed promise. However, with published longer term follow up limited the aim of this study was to determine the mid-term outcomes including complications and patient reported outcomes following 1st Tarsometatarsal Plantarflexion Bone Block Arthrodesis with a pre-contoured allograft wedge (1st TMT PFBB arthrodesis) for the treatment of medial column instability. Methods: A retrospective review was performed of consecutive patients who underwent this procedure between 2020-2023 with a minimum 12-month follow-up. This procedure involves a distraction dorsal opening plantarflexion wedge allograft first tarsometatarsal arthrodesis in the treatment of instability or collapse of the medial column. Demographic information, surgical data and WBCT were assessed at 9-12 month follow up. Patients were assessed for radiographic union/nonunion based on WBCT by 3 independent fellowship trained orthopaedic foot and ankle surgeons. Union was defined on WBCT by >50% osseous incorporation at the plantarflexion wedge and bone interface. Patient report outcomes (PRO) including PROMIS and FAAM ADL were collected pre and post operatively. Patients were excluded if diagnosed with Charcot arthropathy/neuropathy or underwent an extended medial column arthrodesis. Results: A total of 65 patients underwent a 1st TMT PFBB arthrodesis procedure. 51 feet (48 patients); 39 females/9 males with a mean age of 52.8 ±12.3 years and average BMI of 30.2±6.9 kg/m2 met inclusion criteria. An average follow-up of 25 months (range 12-49 months). The average allograft wedge was 9mm (range 5-14mm). 13/51 (25.5%) underwent at least one revision. Overall return to OR was 20/51 (39%) excluding hardware removal (17/51; 33%). 21/51 (41%) developed a nonunion. Secondary minor complications include HV recurrence, wound dehiscence, chronic regional pain syndrome, per-implant fracture, and 1st MTP/sesamoid overload. 8 patients (16%) complained of new onset plantar 1st MTP/sesamoid overload pain. The minimum PROMIS and FAAM ADL capture rapture rate was 80% (table 1). Conclusion: We report mid-term follow up data in 48 patients (51 feet) treated for medial column instability through a 1st Tarsometatarsal Plantarflexion Bone Block Arthrodesis with a pre-contoured allograft wedge with average 2-year follow-up. Our cohort had a 25% revision and 41% nonunion rate. We believe patient selection and counseling regarding potential postoperative complications including high reoperation and nonunion rates as well as the potential to overlengthen or overcorrect 1st ray positioning resulting in sesamoid overload symptoms are important to consider before proceeding with 1st TMT plantarflexion allograft bone block arthrodesis.