Abstract
BackgroundThe deformity of the proximal femur and acetabular in patients with developmental dysplasia of the hip (DDH) renders an intraoperative decision for ideal component placement challenging. We hypothesized that the altered morphology of calcar femorale (CF) in DDH patients changed the fixation mechanism of the cementless metaphyseal-filling stem and aimed to predict stem anteversion using proximal femoral anatomical parameters from preoperative CT.MethodsPreoperative and postoperative CT scans of 34 DDHs with a metaphyseal-filling stem in THA were retrospectively analyzed. Proximal femoral anatomical parameters, including the femoral anteversion (FA) and the CF angles at the low femoral neck (LFN) and the center of the lesser trochanter (CLT) levels (FA-LFN, FA-CLT, CF-LFN, and CF-CLT) were measured. The dysplastic hips were divided into the CF group (n = 21) and the non-CF group (n = 13) according to the presence of the CF-LFN. The association between the anatomical parameters and the postoperative stem anteversion was statistically analyzed, and the predicted stem anteversion was compared with postoperative stem anteversion.ResultsIn the CF group, the combination of the CF-LFN and FA-CLT exhibited a strong positive correlation (R = 0.870, p < 0.001) with the postoperative stem anteversion. In the non-CF group, only the FA-LFN had a strong positive correlation (R = 0.864, p < 0.001). Average prediction errors were 5.9° and 6.4° in the CF and non-CF groups.ConclusionsThe presence of CF-LFN is related to the press-fit mechanism of the metaphyseal-filling stem, and the preoperative measurements from CT images can be employed as a tool to predict postoperative stem anteversion in DDH patients.
Highlights
Dislocation has been reported as the main reason for revision after total hip arthroplasty (THA) [1] and is considered to be a more common postoperative complication in patients with developmental dysplasia of the hip (DDH)
In the preoperative computed tomography (CT) images, five proximal femoral anatomical parameters were measured: the femoral anteversion (FA) at middlefemoral neck (MFN), low femoral neck (LFN), and center of the lesser trochanter (CLT) levels and calcar femorale (CF) angles at LFN and CLT levels (i.e., Femoral anteversion at MFN level (FA-MFN), FA-LFN, Femoral anteversion at CLT level (FA-CLT), CF-LFN, and Results Thirty-three out of 34 hips (97.1%) had Calcar femorale angle at CLT level (CF-CLT), while 21 hips (61.8%) had CF-LFN, which divided the hips into the CF and non-CF groups (Table 1)
The FA-MFN was significantly higher in the non-CF group than the CF group (p = 0.001, 33.5° ± 13.1° and 18.5° ± 9.5°)
Summary
Dislocation has been reported as the main reason for revision after total hip arthroplasty (THA) [1] and is considered to be a more common postoperative complication in patients with developmental dysplasia of the hip (DDH). The reported dislocation rate after THA in DDH patients varies from 2.9% [2] to 9.5% [3]. Patients with DDH are in a unique situation because of the increased anteversion in both proximal femur and acetabulum as a result of under-development [7, 8]. The deformity of the proximal femur and acetabular in patients with developmental dysplasia of the hip (DDH) renders an intraoperative decision for ideal component placement challenging. We hypothesized that the altered morphology of calcar femorale (CF) in DDH patients changed the fixation mechanism of the cementless metaphyseal-filling stem and aimed to predict stem anteversion using proximal femoral anatomical parameters from preoperative CT
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