Which acetabular measurements most accurately differentiate between patients and controls? A comparative study

Abstract: Background Acetabular morphology is an important determinant of hip biomechanics. To identify features of acetabular morphology that may be associated with the development of hip symptoms while accounting for spinopelvic characteristics, one needs to determine acetabular characteristics in a group of individuals older than 45 years without symptoms or signs of osteoarthritis. Previous studied have used patients with unknown physical status to define morphological thresholds to guide management. Questions/purposes (1) To determine acetabular morphological characteristics in males and females between 45 and 60 years old with a high Oxford hip score (OHS) and no signs of osteoarthritis; (2) to compare these characteristics with those of symptomatic hip patients treated with hip arthroscopy or periacetabular osteotomy (PAO) for various kinds of hip pathology (dysplasia, retroversion, and cam femoroacetabular impingement); and (3) to assess which radiographic or CT parameters most accurately differentiate between patients who had symptomatic hips and those who did not, and thus, define thresholds that can guide management. Methods Between January 2018 and December 2018, 1358 patients underwent an abdominopelvic CT scan in our institution for nonorthopaedic conditions. Of those, we considered 5% (73) of patients as potentially eligible as controls based on the absence of major hip osteoarthritis, trauma, or deformity. Patients were excluded if their OHS was 43 or less (2% [28]), if they had a PROMIS less than 50 (1% [18]), or their T\uf6nnis score was higher than 1 (0.4% [6]). Another eight patients were excluded because of insufficient datasets. After randomly selecting one side for each control, 40 hips were left for analysis (age 55 \ub1 5 years; 48% [19 of 40] were in females). In this comparative study, this asymptomatic group was compared with a group of patients treated with hip arthroscopy or PAO. Between January 2013 and December 2020, 221 hips underwent hip preservation surgery. Of those, eight were excluded because of previous pelvic surgery, and 102 because of insufficient CT scans. One side was randomly selected in patients who underwent bilateral procedure, leaving 48% (107 of 221) of hips for analysis (age 31 \ub1 8 years; 54% [58 of 107] were in females). Detailed radiographic and CT assessments (including segmentation) were performed to determine acetabular (depth, cartilage coverage, subtended angles, anteversion, and inclination) and spinopelvic (pelvic tilt and incidence) parameters. Receiver operating characteristics (ROC) analysis was used to assess diagnostic accuracy and determine which morphological parameters (and their threshold) differentiate most accurately between symptomatic patients and asymptomatic controls. Results Acetabular morphology in asymptomatic hips was characterized by a mean depth of 22 \ub1 2 mm, with an articular cartilage surface of 2619 \ub1 415 mm2, covering 70% \ub1 6% of the articular surface, a mean acetabular inclination of 48\ub0 \ub1 6\ub0, and a minimal difference between anatomical (24\ub0 \ub1 7\ub0) and functional (22\ub0 \ub1 6\ub0) anteversion. Patients with symptomatic hips generally had less acetabular depth (20 \ub1 4 mm versus 22 \ub1 2 mm, mean difference 3 mm [95% CI 1 to 4]; p < 0.001). Hips with dysplasia (67% \ub1 5% versus 70% \ub1 6%, mean difference 6% [95% CI 0% to 12%]; p = 0.03) or retroversion (67% \ub1 5% versus 70% \ub1 6%, mean difference 6% [95% CI 1% to 12%]; p = 0.04) had a slightly lower relative cartilage area compared with asymptomatic hips. There was no difference in acetabular inclination (48\ub0 \ub1 6\ub0 versus 47\ub0 \ub1 7\ub0, mean difference 0.5\ub0 [95% CI -2\ub0 to 3\ub0]; p = 0.35), but asymptomatic hips had higher anatomic anteversion (24\ub0 \ub1 7\ub0 versus 19\ub0 \ub1 8\ub0, mean difference 6\ub0 [95% CI 3\ub0 to 9\ub0]; p < 0.001) and functional anteversion (22\ub0 \ub1 6\ub0 versus 13\ub0\ub1 9\ub0, mean difference 9\ub0 [95% CI 6\ub0 to 12\ub0]; p < 0.001). Subtended angles were higher in asymptomatic at 105\ub0 (124\ub0 \ub1 7\ub0 versus 114\ub0 \ub1 12\ub0, mean difference 11\ub0 [95% CI 3\ub0 to 17\ub0]; p < 0.001), 135\ub0 (122\ub0 \ub1 9\ub0 versus 111\ub0 \ub1 12\ub0, mean difference 10\ub0 [95% CI 2\ub0 to 15\ub0]; p < 0.001), and 165\ub0 (112\ub0 \ub1 9\ub0 versus 102\ub0 \ub1 11\ub0, mean difference 10\ub0 [95% CI 2\ub0 to 14\ub0]; p < 0.001) around the acetabular clockface. Symptomatic hips had a lower pelvic tilt (8\ub0 \ub1 8\ub0 versus 11\ub0 \ub1 5\ub0, mean difference 3\ub0 [95% CI 1\ub0 to 5\ub0]; p = 0.007). The posterior wall index had the highest discriminatory ability of all measured parameters, with a cutoff value of less than 0.9 (area under the curve [AUC] 0.84 [95% CI 0.76 to 0.91]) for a symptomatic acetabulum (sensitivity 72%, specificity 78%). Diagnostically useful parameters on CT scan to differentiate between symptomatic and asymptomatic hips were acetabular depth less than 22 mm (AUC 0.74 [95% CI 0.66 to 0.83]) and functional anteversion less than 19\ub0 (AUC 0.79 [95% CI 0.72 to 0.87]). Subtended angles with the highest accuracy to differentiate between symptomatic and asymptomatic hips were those at 105\ub0 (AUC 0.76 [95% CI 0.65 to 0.88]), 135\ub0 (AUC 0.78 [95% CI 0.70 to 0.86]), and 165\ub0 (AUC 0.77 [95% CI 0.69 to 0.85]) of the acetabular clockface. Conclusion An anatomical and functional acetabular anteversion of 24\ub0 and 22\ub0, with a pelvic tilt of 10\ub0, increases the acetabular opening and allows for more impingement-free flexion while providing sufficient posterosuperior coverage for loading. Hips with lower anteversion or a larger difference between anatomic and functional anteversion were more likely to be symptomatic. The importance of sufficient posterior coverage was also illustrated by the posterior wall indices and subtended angles at 105\ub0, 135\ub0, and 165\ub0 of the acetabular clockface having a high discriminatory ability to differentiate between symptomatic and asymptomatic hips. Future research should confirm whether integrating these parameters when selecting patients for hip preservation procedures can improve postoperative outcomes

2008 Otto Aufranc Award: Component Design and Technique Affect Cement Penetration in Hip Resurfacing

Either excessive or insufficient cement penetration within the femoral head after hip resurfacing influences the risk of femoral failures. However, the factors controlling cement penetration are not yet fully understood. We determined the effect of femoral component design and cementation technique on cement penetration. Six retrieved femoral heads were resurfaced for each implant (BHR®, ASR®, Conserve Plus®, DuROM®, ReCAP®) using the manufacturers’ recommendations for implantation. In addition, the BHR was implanted using the Conserve Plus® high-viscosity cementation technique, “BHR/hvt,” and vice versa for the Conserve, “Conserve/lvt.” The average cement penetration was highest with BHR (65.62% ± 15.16%) compared with ASR® (12.25% ± 5.12%), Conserve Plus® (19.43% ± 5.28%), DuROM® (17.73% ± 3.96%), and ReCAP® (26.09% ± 5.20%). Cement penetration in BHR/hvt remained higher than all other implants equaling 36.7% ± 6.6%. Greater femoral component design clearance correlated with cement mantle thickness. Femoral component design in hip resurfacing plays a major role in cement penetration

Cup orientation following posterior approach THA : the effect of different visual aids and pelvic supports

INTRODUCTION: This study aims to compare cup inclination achieved (1) Using two orientation guides, whilst using the same 3-point pelvic positioner and (2) Using two types of pelvic positioners, whilst measuring intra-operative cup inclination with an inclinometer. MATERIALS AND METHODS: This is a prospective, diagnostic cohort study of a consecutive series of 150 THAs performed through a posterior approach. Two types of 3-point pelvic positioners were used (Stulberg and modified Capello Hip Positioners) and the cup was positioned freehand using one of two orientation guides (mechanical guide or digital inclinometer). Intra-operative inclination was recorded, radiographic cup inclination and anteversion were measured from radiographs. The differences in inclination due to pelvic position (ΔPelvicPosition) and orientation definitions (ΔDefinition) were calculated. Target radiographic inclination and anteversion was 40/20° ± 10°. RESULTS: There was no difference in radiographic cup inclination/ (p = 0.63) using a mechanical guide or digital inclinometer. However, differences were seen in ΔPelvicPosition between the positioners ((Stulberg: 0° ± 5 vs. Capello: 3° ± 6); p = 0.011). Intra-operative inclination at implantation was different between positioners and this led to equivalent cases within inclination/anteversion targets (Stulberg:84%, Capello:80%; p = 0.48). CONCLUSIONS: With the pelvis securely positioned with 3-point supports, optimum cup orientation can be achieved with both alignment guides and inclinometer. Non-optimal cup inclinations were seen when intra-operative inclinations were above 40° and below 32°, or the ΔPelvicPosition was excessive (> 15°; n = 2). We would thus recommend that the intra-operative cup inclination should be centered strictly between 30° and 35° relative to the floor. Small differences exist between different type of pelvic positioners that surgeons need to be aware off and account for

Acetabular sector angles in asymptomatic and dysplastic hips

Abstract: Background: Radiographic evaluation plays an important role in detecting and grading hip dysplasia. Acetabular sector angles (ASAs) measure the degree of femoral head coverage provided by the acetabulum on computed tomographic (CT) scans. In this study, we aimed to determine ASA values at different axial levels in a control cohort with asymptomatic, high functioning hips without underlying hip pathology and a study group with symptomatic, dysplastic hips that underwent periacetabular osteotomy (PAO), thereby defining the ASA thresholds for hip dysplasia.Methods: This was a cross-sectional study evaluating a control group of 51 patients (102 hips) and a study group of 66 patients (72 hips). The control group was high-functioning and asymptomatic, with an Oxford Hip Score of >43, did not have osteoarthritis (Tonnis grade <= 1), underwent a pelvic CT scan, had a mean age (and standard deviation) of 52.1 +/- 5.5 years, and was 52.9% female. The study group had symptomatic hip dysplasia treated with PAO, had a mean age of 29.5 +/- 7.3 years, and 83.3% was female. Anterior ASA (AASA) and posterior ASA (PASA) were measured at 3 axial CT levels to determine equatorial, intermediate, and proximal ASA. The thresholds for dysplasia were determined using receiver operating characteristic (ROC) curve analysis, including the area under the curve (AUC).Results: Patients with dysplasia had significantly smaller ASAs compared with the control group; the differences were most pronounced for proximal AASAs and proximal and intermediate PASAs. The control group had a mean proximal PASA of 162 degrees +/- 17 degrees, yielding a threshold for dysplasia of 137 degrees (AUC, 0.908). The mean intermediate PASA for the control group was 117 degrees +/- 11 degrees, yielding a threshold of 107 degrees (AUC, 0.904). The threshold for anterior dysplasia was 133 degrees for proximal AASA (AUC, 0.859) and 57 degrees for equatorial AASA (AUC, 0.868). The threshold for posterior dysplasia was 102 degrees for intermediate PASA (AUC, 0.933). Conclusions: Measurement of ASA is a reliable tool to identify focal acetabular deficiency with high accuracy, aiding diagnosis and management. A proximal PASA of <137 degrees or an intermediate PASA of <107 degrees should alert clinicians to the presence of dysplasia