Neuropathic first metatarsophalangeal arthrodesis: Deforming force of flexor hallucis longus tendon

Abstract

Background Deformity of the Hallux interphalangeal joint (HIPJ) is a common complication following neuropathic 1st MPJ arthrodesis. Although largely asymptomatic, there have been no such studies evaluating the incidence of deformity and degeneration following 1st MPJ arthrodesis, in the neuropathic patient population. The aim of this paper was to highlight the incidence of deformity and degenerative changes at the HIPJ following 1st MPJ arthrodesis in neuropathic patients. Methodology/Procedures Retrospective radiographic review of 324 patients who underwent 1st MPJ arthrodesis, of these patients, 42 patients met inclusion criteria with a diagnosis of peripheral neuropathy due to all causes (diabetic, idiopathic, alcoholic). Preoperative, 12 weeks postoperative and long term (average of 48 weeks) weight bearing radiographs were evaluated for degenerative changes and angular deformity of the hallux interphalangeal joint. The evaluated angles include the hallux interphalangeal joint angle (HIA), the plantar distal hallux angle (PDHA), and the hallux to ground angle (H-G angle). Results Deformity and/or degenerative changes of the HIPJ were seen in 80.9% of patients at long term follow up as evaluated from the HIPJ angle and the PDHA angle. The mean percentage change of the HIPJ angle from preoperative to final postoperative follow up was 19.8% and from preoperative to long term follow up was 37.4%. The percentage change of the PDHA angle was 1.39% from preoperative to final follow up and 13.87% from preoperative to long term follow up. A paired t test was performed to showcase statistical significance and was found to be significant for the HIPJ angle preoperatively to final postoperative (p-value < 0.0076) and the preoperative to long term follow up for the HIPJ angle (P-value <0.001). The PDHA angle was statistically significant at long term follow up (p <0.0001). These results demonstrate the degree of deformity and subsequent degeneration that is present in the HIPJ following first MPJ arthrodesis in neuropathic patients. Discussion The senior surgeons have identified a higher incidence of HIPJ deformity in neuropathic patients after 1st MPJ arthrodesis compared to historic literature incidence. These findings at the HIPJ that, if not addressed, could result in eventual breakdown of the joint with significant deformity. The results of this analysis suggest that a prophylactic flexor hallucis longus (FHL) tenotomy should be performed simultaneously with 1st MPJ arthrodesis to prevent progression of deformity and degeneration in this joint in the neuropathic population. This finding would be best explored in future studies as a prospective review.