Lateral versus conventional fasciotomy for prevention of lateral femoral cutaneous nerve injury in total hip arthroplasty with direct anterior approach: a study protocol for dual-center, single-blind, randomized controlled trial

Abstract

Background; An incision for total hip arthroplasty (THA) via the direct anterior approach (DAA) is generally made outside of the space between sartorius and tensor fasciae lataea muscles to prevent lateral femoral cutaneous nerve (LFCN) injury. Recent anatomical studies have revealed that the LFCN not only courses between the sartorius and tensor fasciae latae muscles, but it also branches radially while distributing in the transverse direction from the sartorius muscle to the tensor fasciae latae muscle. The latter is called the fan type, and studies suggest that damage to the fan type LFCN is unavoidable by conventional fasciotomy. We previously demonstrated that injury to non-fan type LFCN occurred in 28.6% of patients who underwent THA by fasciotomy performed 2 cm away from the intermuscular space. This suggests that the conventional approach also poses a risk of LFCN injury for non-fan type LFCN. LFCN injury is rarely reported in the anterolateral approach (ALA), which involves incision of fascia further away than DAA. The purpose of this study is to investigate how the position of fasciotomy in DAA affects the risk of LFCN injury. Methods; This is a prospective, randomized, controlled study. All patients are divided into the fan type and non-fan type using ultrasonography before surgery. Patients with the non-fan type LFCN will be performed by the conventional fasciotomy and the lateral fasciotomy in the order specified in the allocation table created in advance by our clinical trial center. The primary endpoint is the presence of LFCN injury. The secondary endpoints will be assessed based on patient-reported outcomes (PROs) at 3 months after surgery in an outpatient setting using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Japanese Orthopaedic Association Hip-Disease Evaluation Questionnaire (JHEQ), and the Forgotten-Joint Score-12 (FJS-12). Discussion; We hypothesize that the incidence of LFCN injury due to DAA-THA can be reduced by making the incision further away from where it is typically made in conventional fasciotomy. If our hypothesis is confirmed, it will reduce the disadvantages of DAA, improve patient satisfaction. Trial registration; UMIN Clinical Trials Registry, UMIN000035945.Registered on 20 Feburary 2019.