gms | German Medical Science

Objectives: The aims of this study were to assess and quantify abductor muscle strength deficits after total hip arthroplasty (THA) and to determine associations with external factors.

Methods: Studies reporting on abductor muscle strength before and/or after THA performed for OA or osteonecrosis of the hip were considered for inclusion. Studies reporting on hip abductor strength measured manually were excluded. Data sources were Embase, Medline ALL, and the Cochrane Central Register of Controlled Trials. Strength deficits were compared to the healthy contralateral side (torque ratio; for unilateral THA) and to control subjects. Meta-analysis was performed in six groups according to the time of the measurements, namely preoperatively, 1-3 months, 4-6 months, 9-12 months, 18-24 months, and > 24 months postoperatively. Meta-analysis was based on a random effects model using the method of DerSimonian & Laird.

Results: Out of 6035 studies initially screened, 19 including a total of 875 subjects met the inclusion criteria. Patients scheduled for a THA had a mean summary strength deficit of 18.6% compared to control subjects (CI [-43.6, 1.0%]). There was no strength difference between preoperative and 1-3 months postoperative measurements. At later postoperative times, however, abductor muscle strength was consistently improved compared to the preoperative measurements with a mean percentage increase of 20.2 % (CI [5.6, 34.8%]) at 4-6 months, 29.6% (CI [4.7, 54.4%]) at 9-12 months, and 49.8% (CI [-31.0, 130.6%]) at 18-24 months postoperatively (Figure 1 [Fig. 1]). For unilateral THA, the mean torque ratio was 86.3% (CI [75.4, 97.2%]) and 93.4% (CI [75.1, 111.6%]) before and >24 months after THA, respectively. Study quality was low to moderate. None of a series of study-specific parameters clearly influenced abductor muscle strength deficit.

Conclusion: This systematic review shows the lack of qualitative evidence for abductor muscle strength deficits in patients undergoing THA. Nonetheless, strength deficits are expected to gradually decrease over the first 2 years postoperatively. However, in most cases, muscle strength of the operated side does not reach the level of the healthy side. Systematic documentation of the strength before and after THA is necessary in the single patient in order to adapt the rehabilitation management and at the population level to identify surgical and rehabilitation parameters influencing the strength deficit.