Plantar Fascia Strain and Medial Calcaneal Tuberosity Pressure After Zadek Osteotomy: A Cadaveric Study.

Abstract

Insertional Achilles tendinopathy (IAT) is a frequent cause of posterior heel pain and functional impairment. Traditional surgical treatment involves debridement and reattachment of the Achilles tendon with excision of the posterosuperior calcaneal prominence. The Zadek osteotomy (ZO), a dorsal closing wedge osteotomy of the calcaneus, has regained popularity, particularly with the advent of minimally invasive surgical (MIS) techniques. ZO has been shown to improve Achilles tendon biomechanics and decrease pressure within the retrocalcaneal bursa. However, its biomechanical effects on plantar fascia strain and medial calcaneal tuberosity pressure are unknown, and small series have reported postoperative plantar heel pain with uncertain incidence. This study aims to quantify plantar fascia strain and the medial calcaneal tuberosity pressure following ZO. Twelve fresh frozen foot and ankle cadaveric specimens, amputated at the mid-tibia/fibula level, were used for biomechanical testing. Point pressure sensor catheters and differential variable reluctance transducers (DVRTs) were used to measure pressure between the plantar fascia and the inferior surface of the medial calcaneal tuberosity (medial calcaneal tuberosity pressure) as well as plantar fascia strain, respectively, in both the intact state and after ZO. The ZO was performed using a standardized 1-cm dorsal closing wedge osteotomy, secured with a 6.5-mm cannulated screw. Paired <i>t</i> tests were used to compare measurements between the intact and post-osteotomy states (<i>P</i> < .05). When compared to the intact state, medial calcaneal tuberosity pressure increased by 43% following ZO (from 67 to 96 mm Hg; mean difference 29 mm Hg (95% CI 20.1-37.9, <i>P</i> = .0016). Plantar fascia strain increased in both bands, but neither change reached statistical significance. In a cadaveric model, ZO significantly increased medial calcaneal tuberosity pressure. Although plantar fascia strain also increased, the change was not statistically significant. These biomechanical alterations plausibly contribute to postoperative plantar fascia discomfort and help explain the heel pain reported by some patients following ZO. However, further clinical studies are necessary to determine the true clinical significance of these findings.