| Objective To evaluate the effect of medial protrusion technique on abductor strength recovery after THA in patients with developmental dysplasia of the hip (DDH).Methods A total of 116 patients who underwent unilateral hip replacement for DDH, femoral neck fracture, femoral head necrosis and hip osteoarthritis in People's Hospital of Wuhan University from January 2012 to December 2021 were retrospectively analyzed, and the patients were divided into DDH group (52 cases) and non-DDH group (64 cases).Clinical data were collected before surgery and at 1, 4, 24 and 48 weeks after surgery, including Harris score, VAS pain score and bilateral hip abductor muscle moment ratio (HAMMR).The distance of hip joint rotation center was measured by pelvis anteroposteric plain film, and the difference of abductor muscle moment between the two groups was compared.Results The patients were followed up for 12 to 18 months, with an average follow-up time of 14.3 months. The Harris score of 52 patients in DDH group improved from (39.6±7.9) scores before surgery to (85.1±6.2) scores at 12 months after surgery, with statistical significance (P<0.05). In 52 patients with DDH group, the mean inward movement distance of hip rotation center was (15.5±6.0) mm, the minimum inward movement distance was 8mm, and the maximum inward movement distance was 24.4mm, including 24 patients with Crowe type Ⅰ, 19 patients with Crowe type Ⅱ, and 9 patients with Crowe type Ⅲ. In the DDH group, HAMMR was (85.3±7.4)% and (93.9±3.6)% at 6 and 12 months after operation, respectively, which was significantly improved compared with that before operation (P<0.05), indicating that the recovery of abductor muscle strength on the affected side was close to the contralateral level (100%). According to Pearson correlation analysis, there was no significant correlation between the rotation center inward shift distance and HAMMR (r=-0.061, P=0.665>0.05). Independent sample t test for HAMMR between DDH group and non-DDH group showed no significant difference in HAMMR at 1, 5 and 12 months after operation (P>0.05).Conclusion In DDH patients with THA, the medial protrusion technique is used to move the center of rotation within a limited range (no more than 24.4 mm), which has no significant effect on the recovery of hip abductor muscle strength 6 months after surgery, and the hip function and abductor muscle strength are significantly improved after surgery. |
