Comparison of Cup Alignment, Jump Distance, and Complications in Consecutive Series of Anterior Approach and Posterior Approach Total Hip Arthroplasty.

The purpose of this study was to compare cup position, jump distance, and rate of dislocations in 100 total hip arthroplasty (THA) cases performed with the direct anterior approach (DAA) and 100 cases performed with the posterior approach (PA). Abduction and anteversion angles were measured using Martell Hip Analysis software. The average cup anteversion in the DAA group (17.6°) was significantly different than the PA average (22.6°), P<.001. The average cup abduction angle was similar between groups (DAA 44.2° vs. PA 44.3°, P=.87), but the variance was significantly reduced with the direct anterior approach, P=.02. The use of intraoperative fluoroscopy with the DAA allowed for more accurate cup placement and eliminated severely vertical cups (>55°) seen with the PA.

A prospective, randomized study of cross-linked and non-cross-linked polyethylene for total hip arthroplasty at 10-year follow-up.

In 1999, our institution initiated a prospective study to compare the outcome of total hip arthroplasty patients randomized to either non-cross-linked liners or polyethylene liners that were cross-linked with 5.0 Mrad of gamma-irradiation and heat treated to eliminate free radicals. Among 230 randomized THAs, 13 have had reoperations, and 31 patients with 32 THAs died with less than 9-year follow-up. Follow-up for the remaining 185 THAs averaged 10.0 ± 1.8 years. There have been 9 wear-related liner exchanges among the non-cross-linked group and none among the cross-linked group. Using revision for wear-related complications as an endpoint, survivorship at 10-years was 94.7 ± 4.6% for non-cross-linked and 100% for cross-linked (P = .003). Among unrevised hips, the mean linear wear rate was 0.22 mm/yr for non-cross-linked and 0.04 mm/yr for cross-linked (P < .001). The incidence of clinically important osteolysis with an area of at least 1.5 square centimeters among unrevised hips was 22% for non-cross-linked and 0% for cross-linked (P < .001).

Osteolysis propensity among bilateral total hip arthroplasty patients.

Because some patients with high wear rates demonstrate extensive osteolysis whereas other patients with similarly high wear rates show little or no evidence of osteolysis, we hypothesized that both polyethylene wear and a patient-specific propensity mediate the development of osteolysis. We evaluated wear and osteolysis using computed tomography and radiographs among 46 patients who had undergone bilateral total hip arthroplasties (THAs). A radiographic patient-specific propensity for osteolysis associated with each THA was quantified by dividing the amount of osteolysis by the volumetric wear. Using a multivariate regression analysis to simultaneously consider the influence of polyethylene wear and patient propensity, we found that both factors are associated with the amount of osteolysis around a THA and that they appear to be of similar importance.

A three-dimensional method for evaluating changes in acetabular osteolytic lesions in response to treatment.

UNLABELLED: The treatment of asymptomatic osteolysis among well-fixed cementless cups remains controversial. To compare the effectiveness of different treatment strategies, an objective technique for evaluating bone remodeling would be useful. By matching and comparing serial CT images with the aid of a computer-assisted imaging program, we developed a method to evaluate three-dimensional mineralization changes within osteolytic defects. Preoperative, immediate postoperative, and followup CT images were normalized based on a phantom with known densities and matched using image registration so that the same region could be analyzed on each image. New bone mineralization within the preoperative osteolytic lesion volume was quantified based on a patient-specific trabecular bone density threshold. As a pilot study, we applied this technique in 10 patients treated by polyethylene liner exchange with débridement and grafting of periacetabular osteolytic lesions using a calcium sulfate bone graft substitute. Relative to the preoperative osteolytic lesion volume, an average of 43% (range, 8%-72%) of each defect was filled with graft at revision. After resorption of the graft, an average of 24% (range, 9%-44%) of the original defect volume demonstrated evidence of new mineralization at 1-year followup. The amount of new mineralization was directly proportional (r(2) = 0.70) to the defect filling achieved at revision. CT-based image analysis offers an objective method for quantifying three-dimensional bone remodeling and can be used to evaluate the effectiveness of osteolysis treatment strategies. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

A comparison of a second- and a third-generation modular cup design: is new improved?

The highly cross-linked polyethylene liners currently used with modular uncemented cups have substantially decreased wear and osteolysis at early follow-up. However, retroacetabular osteolysis has still been reported in some cases with DePuy Orthopaedic's (Warsaw, IN) second-generation Duraloc acetabular shell. DePuy's third-generation Pinnacle cup incorporates a different shell-liner locking mechanism. We compared the clinical outcome among a matched series of 42 Duraloc and 42 Pinnacle cups at a mean follow-up of 5.9 years. Although the Harris Hip Scores and wear rates were not statistically different between the 2 cup designs, retroacetabular osteolysis behind the central hole was absent among the Pinnacle cups but noted among 19% of the Duraloc cups.