Femoral offset is underestimated on anteroposterior radiographs of the pelvis but accurately assessed on anteroposterior radiographs of the hip. J Bone Joint Surg (Br)
Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Nuffield Orthopaedic Centre, University of Oxford, Windmill Road, Oxford OX3 7LD, UK.The Bone & Joint Journal (Impact Factor: 3.31). 04/2012; 94(4):477-82. DOI: 10.1302/0301-620X.94B4.28067
The aim of this retrospective cohort study was to identify any difference in femoral offset as measured on pre-operative anteroposterior (AP) radiographs of the pelvis, AP radiographs of the hip and corresponding CT scans in a consecutive series of 100 patients with primary end-stage osteoarthritis of the hip (43 men and 57 women with a mean age of 61 years (45 to 74) and a mean body mass index of 28 kg/m(2) (20 to 45)). Patients were positioned according to a standardised protocol to achieve reproducible projection and all images were calibrated. Inter- and intra-observer reliability was evaluated and agreement between methods was assessed using Bland-Altman plots. In the entire cohort, the mean femoral offset was 39.0 mm (95% confidence interval (CI) 37.4 to 40.6) on radiographs of the pelvis, 44.0 mm (95% CI 42.4 to 45.6) on radiographs of the hip and 44.7 mm (95% CI 43.5 to 45.9) on CT scans. AP radiographs of the pelvis underestimated femoral offset by 13% when compared with CT (p < 0.001). No difference in mean femoral offset was seen between AP radiographs of the hip and CT (p = 0.191). Our results suggest that femoral offset is significantly underestimated on AP radiographs of the pelvis but can be reliably and accurately assessed on AP radiographs of the hip in patients with primary end-stage hip osteoarthritis. We, therefore, recommend that additional AP radiographs of the hip are obtained routinely for the pre-operative assessment of femoral offset when templating before total hip replacement.
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ABSTRACT: Background: In pre-operative planning for total hip arthroplasty (THA), femoral offset (FO) is frequently underestimated on AP pelvis radiographs as a result of inaccurate patient positioning, imprecise magnification, and radiographic beam divergence. The aim of the present study was to evaluate the accuracy and reliability of predicting three-dimensional (3-D) FO from standardised AP pelvis radiographs. Methods: In a retrospective cohort study, pre-operative AP pelvis radiographs, AP hip radiographs and CT scans of a consecutive series of 345 patients (345 hips, 146 males, 199 females, mean age 60 (range: 40-79) years, mean body-mass-index 27 (range: 19-57)kg/m(2)) with primary end-stage hip OA were reviewed. Patients were positioned according to a standardised protocol and all images were calibrated. Using validated custom programmes, FO was measured on corresponding radiographs and CT scans. Measurement reliability was evaluated using intra-class-correlation-coefficients. To predict 3-D FO from AP pelvis measurements and to assess the accuracy compared to CT, the entire cohort was randomly split into subgroups A and B. Gender specific regression equations were derived from group A (245 patients) and the accuracy of prediction was evaluated in group B (100 patients) using Bland-Altman plots. Results: In the entire cohort, mean FO was 39.2mm (95%CI: 38.5-40.0mm) on AP pelvis radiographs, 44.1mm (95%CI: 43.4-44.9mm) on AP hip radiographs and 44.6mm (95%CI: 44.0-45.2mm) on CT scans. In group B, we observed no significant difference between gender specific predicted FO (males: 48.0mm, 95%CI: 47.1-48.8mm; females: 42.0mm, 95%CI: 41.1-42.8mm) and FO as measured on CT (males: 47.7mm, 95%CI: 46.1-49.4mm, p=0.689; females: 41.6mm, 95%CI: 40.3-43.0mm, p=0.607). Conclusions: The present study suggests that FO can be accurately and reliably predicted from AP pelvis radiographs in patients with primary end-stage hip osteoarthritis. Our findings support the surgeon in pre-operative templating on AP-pelvis radiographs and may improve offset and limb length restoration in THA without the routine performance of additional radiographs or CT.
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ABSTRACT: The objectives of the present study were to determine ( 1 ) whether differences in the radiographic appearance of the of the proximal femoral canal exist on corresponding AP pelvis and AP hip radiographs, and ( 2 ) whether radiographic assessment of canal shape is accurate with reference to computed tomography (CT).In a retrospective study, corresponding radiographs and CT scans of 100 consecutive patients with primary hip OA were evaluated. Active shape modelling (ASM) was performed to assess the variation in proximal femoral canal shape and to identify differences between AP hip and AP pelvis views. Differences in the medial cortical flare between radiographs and CT were quantified using least squares curve fitting.ASM identified significant differences in the assessment of canal shape on corresponding AP hip and AP pelvis views. Curve fitting demonstrated a good agreement between AP hip radiographs and CT. Agreement between AP pelvis radiographs and CT was less good.In contrast to AP pelvis radiographs, AP hip radiographs allow a more accurate and reliable assessment of proximal femoral canal shape in the frontal plane in primary hip OA. Our findings may improve stem fit in total hip arthroplasty without the routine use of CT.
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ABSTRACT: High tibial osteotomy and unicompartmental knee arthroplasty are surgical treatment options for unicompartmental knee arthritis; these procedures are indicated for patients who do not have severe arthritis in the lateral compartment. Valgus stress radiographs sometimes are used to make this evaluation, but this test has not been critically evaluated. We sought to determine (1) whether valgus stress radiographs help to evaluate the integrity of the cartilage in the lateral compartment in patients undergoing TKA for noninflammatory arthritis, and (2) whether valgus stress radiographs can identify patients whose varus deformity is correctable. We reviewed preoperative hip-to-ankle standing radiographs, AP standing radiographs, and valgus stress radiographs of 84 patients (91 knees) who underwent TKA for varus knee arthritis between July 2010 and January 2012. Valgus stress radiographs were obtained with the patient supine with the knee 20° flexed and a firm manual valgus force was applied through the knee. On valgus stress radiographs, the lateral compartment joint space width and the corrected mechanical alignment were measured. Intraoperative cartilage assessment (Outerbridge grade) was compared with lateral compartment joint space width. Knees with mechanical leg alignment of 3° varus to 3° valgus on valgus stress radiographs were considered correctable deformities. The lateral compartment joint space width on valgus stress radiographs did not correlate with the intraoperative Outerbridge grading of the lateral compartment cartilage (rs = -0.154; p = 0.146). The majority of knees (93%; 55 of 59) with 10° or less mechanical varus on hip-to-ankle standing radiographs were correctable within the range of 3° varus to 3° valgus. Valgus stress radiographs provided no added benefit to the radiographic assessment of the lateral compartment cartilage and regarding the correctability of the varus deformity. Level III, diagnostic study. See the Instructions for Authors for a complete description of levels of evidence.
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