The iliocapsularis muscle: an important stabilizer in the dysplastic hip.
BACKGROUND
The iliocapsularis muscle is a little known muscle overlying the anterior hip capsule postulated to function as a stabilizer of dysplastic hips. Theoretically, this muscle would be hypertrophied in dysplastic hips and, conversely, atrophied in stable and well-constrained hips. However, these observations have not been confirmed and the true function of this muscle remains unknown.


OBJECTIVE
We quantified the anatomic dimensions and degree of fatty infiltration of the iliocapsularis muscle and compared the results for 45 hips with deficient acetabular coverage (Group I) with 40 hips with excessive acetabular coverage (Group II).


METHODS
We used MR arthrography to evaluate anatomic dimensions (thickness, width, circumference, cross-sectional area [CSA], and partial volume) and the amount of fatty infiltration.


RESULTS
We observed increased thickness, width, circumference, CSA, and partial volume of the iliocapsularis muscle in Group I when compared with Group II. Additionally, hips in Group I had a lower prevalence of fatty infiltration compared with those in Group II. The iliocapsularis muscle typically was hypertrophied, and there was less fatty infiltration in dysplastic hips compared with hips with excessive acetabular coverage.


CONCLUSIONS
These observations suggest the iliocapsularis muscle is important for stabilizing the femoral head in a deficient acetabulum. This muscle serves as an anatomic landmark when performing a periacetabular osteotomy. Additionally, preoperative evaluation of morphologic features of the muscle can be used as an adjunct for decision making when treating patients with borderline hip dysplasia or femoroacetabular impingement.
Department of Orthopaedic Surgery, Inselspital, University of Bern, Murtenstrasse, 3010 Bern, Switzerland.
D
D
Babst
S D
SD
Steppacher
R
R
Ganz
K A
KA
Siebenrock
M
M
Tannast
D000293:Adolescent; D000328:Adult; D001175:Arthrography / Q000379:methods; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D005260:Female; D006618:Hip Dislocation, Congenital / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology* / Q000601:surgery; D011474:Prosthesis Design; D016896:Treatment Outcome; D055815:Young Adult