Radiographic Outcomes, Union Rates, and Complications Associated with Implants Positioned on the Plantar Bone Surface for Midfoot Arthrodesis

CATEGORY: Midfoot/Forefoot; Trauma INTRODUCTION/PURPOSE: Midfoot fusions have long been used to treat a variety of procedures in the foot. Indications may include hallux valgus correction, first ray instability, midfoot arthritis, pes planovalgus, trauma, and Charcot reconstruction. One of the drawbacks of this procedure is nonunion, which has been consistently reported between 5-10%. Placing implants and obtaining fixation along the plantar surface of the bone may create a tension band implant construct during physiologic loading that helps to compress the arthrodesis site and thereby may further optimize the healing potential. This study reports on the radiographic and clinical outcomes of plantar plating and arthrodesis of midfoot joints for a variety of procedures. METHODS: A retrospective review was undertaken of consecutive patients between 2012-2019 that underwent a midfoot fusion with plantar positioned implants by a fellowship-trained foot and ankle orthopedic surgeon at a single institution. 62 patients underwent arthrodesis of the midfoot as part of a correction for hallux valgus, flatfoot deformity, midfoot arthritis, Lisfranc injury, Charcot correction or a combination these diagnoses. Average follow-up was 36.2 months (range, 16-66 months). For those treated for a flatfoot deformity, the lateral talus-first metatarsal (Meary’s) angle and medial arch sag angle (MASA) were compared on preoperative and postoperative imaging to obtain the magnitude of radiographic correction achieved. For those treated for hallux valgus deformity, the inter-metatarsal angle (IMA) was utilized to establish the magnitude of deformity correction. Serial weight-bearing radiographs were independently evaluated for malunion, nonunion, or hardware migration to be logged as complications at the arthrodesis site. RESULTS: The 1st TMT joint was fused in 43 patients, and the NC joint was fused in 23 patients. Five patients had simultaneous fusion of the 1st TMT and NC joints. Two patients underwent arthrodesis of the talonavicular (TN) joint with one patient having simultaneous arthrodesis of the TN and NC joints. We found statistically significant improvement in the lateral talus-first metatarsal-angle (Meary’s) and medial arch sag angle (MASA) for those treated for flatfoot corrections. For those treated for hallux valgus, there was significant reduction in the Intermetatarsal angle (IMA) from 15.4 to 6.8 degrees. The overall nonunion rate was 6.45% in all patients. The nonunion rate was reduced to 3.3%when excluding the Charcot neuroarthropathy patients. There was one symptomatic nonunion requiring revision surgery (1.7%). CONCLUSION: Deformity correction was successfully maintained in those treated for hallux valgus and flatfoot deformities. There were significant improvements in the IMA, the MASA, and Meary’s angle Plates implanted on the plantar bone surface for midfoot arthrodesis provided and maintained deformity correction without hardware irritation for a variety of orthopedic conditions. A clinical and radiographic union rate of94% (97% when excluding Charcot neuroarthropathy patients) was achieved. The risk of nonunion appeared to be higher in diabetic patients, in smokers, with the utilization of claw plates, and when fusion constructs included the NC joint.