Does nerve injury following minimally invasive calcaneal osteotomy clinically correlate to Talusan’s Zone?

Abstract

Category: Hindfoot Introduction/Purpose: Talusan et al (FAI, 2005) described a safe zone for neural structures in medial displacement calcaneal osteotomy following a cadaveric and radiographic investigation. The safe zone was determined to be within the area 11.2 ± 2.7 mm anterior to the landmark line which is from the plantar fascia origin through the center of the posterosuperior aspect of the calcaneal tuberosity. Minimally invasive calcaneal osteotomies been gaining in popularity as it minimises soft tissue disruption and surgical morbidity. However, neural structures are at risk on both the medial and lateral side of the foot during this procedure. We aim to correlate our clinical results with Talusan’s Radiographic Zone (TRZ) following minimally invasive calcaneal osteotomies. Methods: Sixty-three calcaneal osteotomies were performed in our unit from 2010 and 2016. The type of osteotomies was as follows: Medialising, n = 34; Lateralising n =15; Zadek (Dorsal closing wedge), n =13; and Dwyer (lateral closing wedge), n = 1. Clinical data were recorded with any nerve injury noted. The calcaneal osteotomies were graded into whether they fell into TRZ. We also evaluated Talusan’s alternative method which he described and is based on alternative line 60% of the distance from the angle of Gissane to the tip of most posterior aspect of the calcaneal tuberosity where the safe zone is a window 5.6 mm anterior to this. Results: Five (8%) patients (Medialising, n = 2; Lateralising n =2; Zadek, n =1) reported sural nerve paraesthesia following surgery in our series. However, this was transient and they recovered fully. In total, seven patients (Medialising, n = 4; Lateralising n =1; Zadek, n =1; Dwyer, n=1) fell outside TRZ in our series, of which 2 reported transient sural nerve paraesthesia. Based on our results, TRZ clinically correlated with nerve injury (Chi square test, p=0.032). The other three patients who reported sural nerve paraesthesia but fell inside TRZ measured on average 10.4 mm from the landmark line (10.2, 10.4, 10.7 mm). However when we used the alternative method, they all fell outside the safe zone of this alternative line. Conclusion: Our results suggest that TRZ clinically correlated with nerve injury. However, the alternative line (where the safe zone is a window 5.6 mm anterior to this line) might be more accurate than the landmark line (where the safe zone is 11.2 ± 2.7 mm anterior to this line). More clinical studies with larger numbers might be required to confirm this.