Minimally Invasive Surgery for Correction of Adult Acquired Flat Foot Deformity: An Anatomic Study

CATEGORY: Midfoot/Forefoot; Hindfoot INTRODUCTION/PURPOSE: Adult acquired flatfoot deformity (AAFD) is a complex and chronic debilitating condition characterized by a decrease in the medial arch height and, in advanced stages, a decrease in the talonavicular coverage angle as the forefoot drifts into pronation and abduction. Operative treatment of stage II deformity has changed significantly over the past few decades. Joint sparing procedures which aim to realign the hindfoot and augment the diseased tibialis posterior tendon with the flexor digitorum longus transfer are commonly performed. The introduction of minimally invasive surgery (MIS) has been associated with smaller incisions, less blood loss, and quicker recovery times. The purpose of this study was to qualitatively and quantitatively observe the tendinous and neurovascular structures at risk with MIS AAFD osteotomy procedures in cadaveric feet. METHODS: MIS technique was used to perform medial displacement calcaneal, Evans, and Cotton osteotomies on nine cadaveric feet under fluoroscopic guidance. The sural nerve, superficial peroneal nerve and its branches, deep peroneal nerve, dorsalis pedis artery, saphenous vein, and peroneal and extensor hallucis longus tendons were carefully dissected from each cadaveric foot and evaluated for injuries following the MIS osteotomy cuts. The distance from the osteotomy cuts and these anatomic structures were measured and recorded. RESULTS: On average, the sural nerve was 8.4 mm and 9 mm from the calcaneal and Evans osteotomy sites, respectively. The intermediate dorsal cutaneous nerve was on average 68.3 mm and 41.1 mm from the calcaneal and Evans osteotomy sites, respectively. The peroneal tendons were on average 16.7 mm and 0 mm from the calcaneal and Evans osteotomy sites, respectively. The extensor hallucis was an average of 1 mm from the Cotton osteotomy site. There was a partial tear injury to the peroneus brevis in four of the cadaveric specimens at the Evans osteotomy site without complete laceration. There was no injury to the sural nerve, superficial peroneal nerve and its branches, saphenous vein, deep peroneal nerve, dorsalis pedis artery, or extensor hallucis longus tendon. CONCLUSION: Tendinous and neurovascular structures are at risk with MIS AAFD osteotomy procedures. Care should be taken with soft tissue handling and blunt dissection to decrease iatrogenic injuries to these structures. Specifically, extra care and recognition of the peroneal tendons during the Evans osteotomy may prevent damage, as this structure was at greatest risk among the three osteotomy cuts. Future research studies evaluating this technique and the functional outcomes in patients in a clinical setting is warranted. Surgical technique studies are underway to implement smaller, yet appropriate bone grafts through mini incisions.