Hip stability after total hip arthroplasty predicted by intraoperative stability test and range of motion: a cross-sectional study

Abstract

BackgroundDislocation continues to be a common complication following total hip arthroplasty (THA). A larger intraoperative range of motion (ROM) is believed to minimize dislocation risk, and intraoperative stability tests have been used to assess the ROM. However, it is not clear whether or not intraoperative stability tests can predict hip stability after THA. It is also unclear which angles are required in intraoperative stability tests. We investigated the usefulness of intraoperative stability tests, and other risk factors to predict hip stability after THA.MethodsPatients operated by single surgeon at one hospital from June 2009 to December 2013 were evaluated. This study included 185 hips with 32 mm metal femoral head. The range of internal rotation with 90° hip flexion (IR angle) was measured as an intraoperative stability test. The variables studied as risk factors included age, height, weight, gender, cerebral dysfunction, preoperative diagnosis, history of previous hip surgery, and IR angle.ResultsMean IR angle was statistically different between patients with dislocation and patients without dislocation (59.5° vs 69.6°: p = 0.006). Cerebral dysfunction and a history of previous hip surgery were statistically related with prevalence of dislocation (p = 0.021, and p = 0.011). The receiver-operating characteristic curve analysis suggested that the cutoff points for IR angle were 51° and 67°. Dislocation rate in larger IR angle group was significantly lower than the rate in smaller IR angle group when patients were divided by 51° (p = 0.002). Logistic regression analyses showed that significant risk factors were cerebral dysfunction (OR: 5.3 (95%CI 1.1–25.9); p = 0.037), history of previous hip surgery (OR: 8.6 (95%CI 1.2–63.0); p = 0.035), and IR angle (OR: 10.4 (95%CI 1.9–57.1); p = 0.007).ConclusionsThe results showed that intraoperative stability test, especially the IR angle, was a useful method to predict hip stability after THA, and a larger intraoperative ROM reduced the likelihood of dislocation. 51° and 67° were indicated as cutoff points for IR angle. Cerebral dysfunction and a history of previous hip surgery are also risk factors for the incidence of dislocation after THA.Trial registrationThis is a retrospective study, not a clinical trial defined by the World Health Organization (WHO).

Causes of and treatment options for dislocation following total hip arthroplasty (Review)

“…The majority of the proponents of the posterior approach carry out dynamic testing for hip stability and soft tissue tension across the hip (i.e., push-pull test). Tanino et al , from the study of 185 hips, noted that with a 32 mm metal femoral head, that an intraoperative stability test, particularly the IR angle, was a useful method to predict hip stability following THA (41). If a trochanteric osteotomy is performed, the risk of dislocation is increased, particularly if a nonunion develops (24).…”

A simple angle-measuring instrument for measuring cemented stem anteversion during total hip arthroplasty

“…As the present study included many cases of developmental dysplasia of the hip, in which the degree of femoral anteversion was significantly large, we employed larger target angles [28]. Recently, the concept of the IR angle was reported to be a useful method for predicting hip stability after THA, and an IR angle of 51°was suggested to be an appropriate cut-off point for such predictions [21]. Because a recent study reported that stem anteversion had the strongest effect on the IR angle [29], we fine-tuned stem anteversion prior to the final implantation to achieve an appropriate IR angle.…”

“…A recent study reported that the intraoperative stability test, especially measuring the IR angle (the range of internal rotation under 90°hip flexion and 0°a bduction/adduction), is a useful method for predicting hip stability after THA. An IR angle of 51°was set as the cut-off point for such predictions [21]. After removing the acetabular osteophytes and femoral neck remnants, the target angle was decided by fine-tuning the femoral broach and neck length to acquire an IR angle of > 51°w ithout causing anterior instability.…”

A simple angle-measuring instrument for measuring cemented stem anteversion during total hip arthroplasty

“…As the present study included many cases of developmental dysplasia of the hip, in which the degree of femoral anteversion was significantly large, we employed larger target angles [28]. Recently, the concept of the IR angle was reported to be a useful method for predicting hip stability after THA, and an IR angle of 51° was suggested to be an appropriate cut-off point for such predictions [21]. A recent study reported that stem anteversion had the strongest effect on the IR angle [29].…”