Aim: Complete tenotomy was performed on the most important flexor hip muscle; namely the iliopsoas during open reduction in patients with developmental dysplasia of the hip (DDH). The iliopsoas and other flexor-extensor muscles in operated and contralateral hips were evaluated comparatively by magnetic resonance imaging (MRI).

Methods: A total of 22 patients with unilateral DDH after the walking age and treated with one-stage combined surgery were analyzed. All patients were operated by the same surgeon with complete tenotomy of iliopsoas muscle hindering open reduction. All patients had functionally excellent results in accordance with the Barrett’s Modified McKay Criteria in their last follow-up visits and according to Severin’s classification all cases were type 1. The imaging was performed by 1,5 T GE Excite MRI device at the supine position, without contrast material and sedation. The sagittal sections for iliopsoas muscle and T2-W FSE axial images for flexor and extensor muscle groups were used. The operated and contralateral sides were compared. Student’s t test, paired t test, and Spearman’s Rank correlation analysis were used for statistical assessment.

Results: The mean age was 12,8±2,9 (9–18) years old. The mean postoperative follow-up period was 112,6 ± 32,0 (68–159) months. The reattachment of the iliopsoas to trochanter minor was observed in 7 patients, with no significance in terms of age, postoperative follow-up period, and the duration of postoperative period (p> 0,05). The atrophy in the operated side was significant in the length of iliopsoas muscle section area (p=0,0001); and the section areas of rectus femoris (p=0,002), tensor fascia lata (p=0,0001), and gluteus maximus (p=0,0001). No significance was detected in sartorius muscle section area (p=0,886). However, unlike other muscles; the ratio of operated versus contralateral side mean muscle section areas was above 1 (1,1± 0,3) for the sartorius muscle. Iliopsoas muscle reattachment was not significant for ratios of the other muscles’ operated versus contralateral side muscle section areas (p> 0,05). The atrophy was significant for the second (p=0,03) and the third (p=0,022) section’s diameter ratios in the non-reattachment versus reattachment group for the iliopsoas muscle.

Conclusion: The reattachment of the iliopsoas muscle to trochanter minor after complete tenotomy was observed in 32% of patients. Following complete iliopsoas tenotomy, the expected compensatory hypertrophy in other flexor hip muscles was not detected. At the operated side, all evaluated muscles were atrophic except for the sartorius muscle. The atrophy of iliopsoas muscle was significant for the operated hip with non-reattachment to insertion site versus reattachment group.