Purpose:To prospectively quantify the accuracy of hip cartilage thickness estimated from three-dimensional (3D) surfaces, generated by segmenting multidetector computed tomographic (CT) arthrograms by using direct physical measurements of cartilage thickness as the reference standard. Materials and Methods:Four fresh-frozen cadaver hip joints from two male donors, ages 43 and 46 years, were obtained; institutional review board approval for cadaver research was also obtained. Sixteen holes were drilled perpendicular to the cartilage of four cadaveric acetabula (two specimens). Hip capsules were surgically closed, injected with contrast material, and scanned by using multidetector CT. After scanning, 5.3-mm cores were harvested concentrically at each drill hole and cartilage thickness was measured with a microscope. Cartilage was reconstructed in 3D by using commercial software. Segmentations were repeated by two authors. Reconstructed cartilage thickness was determined by using a published algorithm. Bland-Altman plots and linear regression were used to assess accuracy. Repeatability was quantifi ed by using the coeffi cient of variation, intraclass correlation coeffi cient (ICC), repeatability coeffi cient, and percentage variability. Results:Cartilage was reconstructed to a bias of 2 0.13 mm and a repeatability coeffi cient of 6 0.46 mm. Regression of the scatterplots indicated a tendency for multidetector CT to overestimate thickness. Intra-and interobserver repeatability were very good. For intraobserver correlation, the coeffi cient of variation was 14.80%, the ICC was 0.88, the repeatability coeffi cient was 0.55 mm, and the percentage variability was 11.77%. For interobserver correlation, the coeffi cient of variation was 13.47%, the ICC was 0.90, the repeatability coeffi cient was 0.52 mm, and the percentage variability was 11.63%. Conclusion:Assuming that an accuracy of approximately 6 0.5 mm is suffi cient, reconstructions of cartilage geometry from multidetector CT arthrographic data could be used as a preoperative surgical planning tool.q RSNA, 2010

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Background: Defining the distribution of subcutaneous fat around the hip in relation to different approaches for total hip arthroplasty (THA) may lead to a better understanding of the relationship between obesity and complications. The purpose of this study was to: (1) describe the intraoperative thickness of subcutaneous fat at the incision site for direct anterior (DAA) and posterior approaches (PA) for THA; and (2) examine the relationship between fat thickness and 90-day postoperative complications. Methods: Intraoperative fat measurements were obtained at the anterior incision site (AT-IS) of the DAA ( n = 60) and the lateral incision site (LT-IS) of the PA ( n = 64). Lateral hip fat thickness was measured from preoperative anteroposterior pelvis radiographs (LT-XR). Body mass index (BMI), sex, age, and 90-day complications were collected retrospectively. Results: Patients within the same demographic groupings had significantly more fat laterally than anteriorly, between 9.6 mm and 17.96 mm. Return to the OR was significantly associated with BMI, AT-IS, and LT-IS. Wound complications were significantly associated with AT-IS. Periprosthetic joint infection (PJI) was significantly associated with BMI and LT-IS. No outcome variables were associated with LT-XR, approach, sex, or age. LT-XR was strongly correlated with AT-IS and LT-IS. Conclusions: Regardless of BMI, sex, or age more soft tissue was encountered with a PA compared to a DAA. General adiposity was associated with return to the OR. Excess incisional fat was associated with wound complications following a DAA and PJI after a PA. LT-XR and clinical examination near the proposed incision, may provide helpful data in making preoperative risk assessments.