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Muscle strength and range of movement deficits 1 year after hip resurfacing surgery using posterior approach

Purpose. The aim was to evaluate the effect of the posterior surgical approach on hip muscle strength and range of movement (ROM). Methods. Maximal isometric external and internal rotator strength of the hip muscles and bilateral leg extension strength were measured by dynamometers. Active (AROM) and passive (PROM) range of motion of the hip were measured by goniometers in 30 patients before and 3, 6 and 12 months after hip resurfacing. Postoperatively the patients were advised to return to their usual physical activities. Results. Prior to the surgery internal rotation strength was on the same level on both sides, whereas external rotation strength of the operated hip was 26% (p < 0.001) lower compared with the unoperated side. External rotation strength remained at the lowered level, but internal rotation strength of the operated hip increased over the level of the contralateral side (both p < 0.001) at 12-month follow-up leading to the imbalance in external/internal rotation strength ratio (p < 0.001). Preoperatively, all active and passive ROMs of the operated side were statistically lower than on the unoperated side (p < 0.001). ROMs of the operated hip improved significantly with the exceptions that active external rotation decreased after the operation (p < 0.001). Conclusions. The patients reported remarkable decrease in pain postoperatively. However, the surgical procedure, particularly the division of the external hip rotator muscles led to specific external rotation strength and ROM deficits. Because typical spontaneous physical activity could not restore hip function, there is a need for specific postoperative rehabilitative programs.