High preoperative range of motion is a significant risk factor for dislocation in primary total hip arthroplasty.

Dislocation after total hip arthroplasty (THA) is multifactorial and is dependent on surgical, implant, and patient factors. We hypothesized that high preoperative hip range of motion is an important variable contributing to instability after THA. We retrospectively reviewed 3379 THAs performed during a 21-year period. Average follow-up was 6.6 years. We examined the effect of surgical approach, femoral head size, and preoperative range of motion on dislocation rates. Patients with a posterior approach and 115 degrees or greater of combined preoperative flexion, adduction, and internal rotation dislocated at a significantly higher frequency than those with less than 115 degrees of combined motion (odds ratio, 1.9; P = .007). High preoperative motion in conjunction with a posterior approach and femoral head size less than 32 mm had the highest dislocation rate in our sample (5.9%). Preoperative range of motion is an important variable that should be taken into consideration during operative planning to help reduce the risk of dislocation.

Posterior capsular injections of ropivacaine during total knee arthroplasty: a randomized, double-blind, placebo-controlled study.

We investigated the hypothesis that a posterior capsular injection of ropivacaine would improve pain and accelerate functional recovery after total knee arthroplasty in a randomized, double-blind, placebo-controlled study design. Sixty-six patients received a standardized multimodal anesthesia protocol that included a femoral nerve block. Twenty milliliters of either saline (control) or ropivacaine (study group) was injected into the posterior capsule. Pain and function outcomes were recorded prospectively at 4, 8, 12, and 24 hours postinjection. Significantly more patients in the study group were able to perform a straight-leg raise at 8 and 12 hours. In addition, significantly more patients in the control group had a numeric pain score higher than 7/10 (severe pain) at the 12-hour evaluation. Other parameters of pain or functional recovery were not significantly different between the 2 groups. Posterior capsular injection did not improve the pain or accelerate the functional recovery after 12 hours in patients also receiving a femoral nerve block for pain control after total knee arthroplasty.