A systematic review and meta-analysis of iliocapsularis muscle: an important landmark in orthopedic surgery.

Purpose: Iliocapsularis (IC) is a small muscle overlying the capsule of the hip joint. Although recent attention is being given to this muscle by orthopedic surgeons who encounter it during the anterior approach to total hip arthroplasty, little is known about its anatomical features. The aim of this study was to review the anatomy of IC, and describe its' origin, insertion, blood supply, innervation, muscle fiber characteristics and size. The function, clinical relevance and comparative anatomy of IC were also appraised.

Methods: Using Evidence-Based Anatomy methodology, electronic databases were searched with the terms "iliocapsularis", "iliacus minor", "iliotrochantericus", and "ilioinfratrochantericus" to identify eligible studies.

Results: Six studies (n = 287 lower limbs) examining the anatomy of IC were included. The pooled prevalence (PP) of the IC was 98.7% (95% CI 96.5-100.0). It arises from the inferior facet of the anterior inferior iliac spine (AIIS) and attaches inferior to the lesser trochanter. Attached to the anteromedial capsule along its entire length, IC has the largest capsular contribution of any of the hip muscles (73.8 ± 27.3 × 16.1 ± 4.4 mm). Thus, it is an important landmark in anterior surgical approaches to the hip joint.

Conclusion: The anatomy of IC is becoming more relevant with the increasing use of anterior approaches to hip surgery. With attachments to the AIIS, the lesser trochanter as well as the length of the capsule, this muscle is an important landmark in total hip arthroplasty.

Level Of Evidence: Level V.