Functional outcome and complication following THA through modified direct anterior approach correlated to cadaveric study: are there any differences in Asian hip?

BACKGROUND: Direct anterior approach (DAA) has several advantages including shorter length of hospital stay, faster recovery, and better functional outcome while this approach may cause damage to the lateral femoral cutaneous nerve (LFCN) as high as 81% in the works of literature. Not much data has identified the LFCN pattern in the Asian population. Therefore, the purpose of our study was to identify characteristics of the LFCN patterns representing an Asian hip, which would aid to provide the most appropriate incision of modified direct anterior approach (MDAA) for total hip arthroplasty (THA), and to identify the clinical outcome and complications following THA through MDAA correlated with cadaveric hip in the Asian population. METHODS: After IRB approval, a cadaveric study was done to identify pattern and course of the LFCN in Asian population. The MDAA defined as the incision 2 fingerbreadths posteriorly to anterior superior iliac spine to avoid injury to the LFCN. The clinical phase identified 32 patients who underwent THA because of late-stage osteoarthritis of the hip. The anterolateral skin numbness was measured along tensor fascia lata between 2 weeks until 2 years. The functional outcome assessed by Harris Hip Score (HHS) and complications were evaluated in all patients. RESULTS: The characteristics of the LFCN from cadaveric study (phase 1) was predominantly in sartorius type (60.0%) followed by posterior type (26.6%), fan type (6.7%), and variant type (6.7%). The clinical phase demonstrated that 23 patients (71.9%) had no numbness while 9 patients (28.1%) came with numbness after undergoing THA through the MDAA. Finally, a small area of skin numbness remained in only 3 patients (9.4%) at 2 years follow-up. Additionally, there was no significant difference in functional score at 2 years follow-up (89.0 vs 91.2, p = 0.422) between those with LFCN injury and those without LFCN injury. CONCLUSIONS: The LFCNs were divided into four types. Modified direct anterior approach, which is an alternative approach for THA, allowing for a lower rate of skin numbness and faster recovery without hip dislocation, abductor weakness, and serious nerve complication. Functional outcome was comparable with and without LFCN injury. LEVEL OF EVIDENCE: Level II, prospective observation study