Abstract
Tannast has recently shown that safe hip dislocation (SHD) for femoroacetabular impingement treatment does not result in atrophy and degeneration of periarticular hip muscles. In more complex procedures, such as relative neck lengthening for Perthes disease (PD) or modified Dunn procedure for slipped capital epiphysis (SCFE), minimus gluteus femoral insertion is detached to achieve enough mobility of osteotomized trochanter and to fix the latter more distally. Aim of this study was to evaluate MRI appearance of minimus and medius gluteus after relative neck lengthening.
Patients treated with SHD and relative neck lengthening eventually associated to epiphyseal realignment for PD or SCFE treatment underwent magnetic resonance imaging (MRI) to study gluteus minimus (MI) and medius (ME) muscles. In the axial T1-weighted sequences, cross sectional area (CSA) and signal intensity were evaluated at acetabular roof level. Statistical comparison was made with the opposite healthy side.
Fifteen patients underwent an MRI at an average of 59 months (SD=27.3) after surgery.
Average ratio between gluteus minimus CSA (treated/healthy side) was 0.90 (SD=0.2): this reduction in volume was statistically significant (p=0.04) as well as the signal intensity (p=0.04). CSA and signal intensity of gluteus medius did not differ between two sides (respectively p=0.78 and p=0.30).
In conclusion, gluteus medius appearance was not influenced by distal fixation of the trochanter. The minimus gluteus was reduced in volume as much as 10% in respect to healty side; increased signal intensity in MRI T1-weighted (fatty infiltration) was found in the minimus gluteus.
