Can Radiographs Predict the Use of Modular Stems in Developmental Dysplasia of the Hip?

Abstract

Background Abnormal anatomy frequently results in the use of a modular stem in patients undergoing primary total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH). However, because these stems are not always available in the operating room, it would be helpful if standard radiographic views could be analyzed in such a way that patients whose femoral anatomy might call for stem modularity could be anticipated before surgery. To our knowledge, no such parameters have been defined. Questions/purposes In the senior author's practice, we used femoral neck anteversion of more than 25°as a determinant for use of a modular stem. Given this criterion, we asked if we could reliably identify plain film radiographic parameters of the femur that predict the use of modular stems. We looked at the following: (1) the neckshaft angle based on the anteroposterior (AP) radiograph (alpha); (2) the neck-shaft angle from the crosstable lateral radiograph (beta); and (3) the calculated femoral anteversion angle. Methods We reviewed preoperative radiographs from 50 of 67 patients (79 hips) who had a primary diagnosis of DDH and underwent primary THA from January 1999 to February 2007 inclusive. Hips with prior femoral-sided surgery (n = 2) or without preoperative films (n = 19) were excluded. Furthermore, patients with bilateral hips had the second hip excluded (n = 8). Twenty-one of 50 received a modular femoral stem based on the criterion of intraoperative neck-shaft anteversion of greater than 25°as measured by the senior surgeon (CLP), whereas the remainder received tapered nonmodular stems. There were no differences in age, sex, height, or weight between the modular stem group and tapered stem group. Radiographs were evaluated to record the parameters listed. Results Patients in whom modular femoral stems were used had a greater mean AP (alpha) neck-shaft angle compared with patients who received tapered nonmodular stem (152°; 95% confidence interval [CI], 146°-157°ver-sus 137°; 95% CI, 134°-141°; p \ 0.001) with an optimal cutoff point for determining the use of modular stems of C 142°(receiver operating characteristic [ROC] area = 73%). Hips in which modular femoral stems were chosen had a smaller mean lateral (beta) neck-shaft angle (152°; 95% CI, 148°-157°versus 161°; 95% CI, 158°-164°; p = 0.003) with an optimal cutoff point of B 153°(ROC area = 65%). Hips in which modular femoral stems were used had a higher femoral anteversion angle (mean 45°; 95% CI, 37°-54°versus 21°; interquartile range, 17°-25°; p \ 0.001) with an optimal cutoff of C 32°(ROC area = 80%).

Total hip arthroplasty with modular stem for Crowe I and II developmental dysplasia of the hip

“…The modular stems have proved to have excellent clinical outcome and satisfaction rate in severe DDH [14, 21]. The most important finding of this study was that the modular stem could provide more accurate hip reconstruction and better FJS for the patients with Crowe I and II DDH in postoperative 2 years.…”

“…Additionally, morphological parameters were found not to be statistically correlated with the severity of hip dislocation [13]. Because of time-consuming, high-cost, and substantial radiation, computerized tomography (CT) was not always available though it allows for accurate assessments of anteversion [14]. These hidden abnormalities in DDH pose big challenges to THA.…”

Is a short stem suitable for patients with hip dysplasia? A report on technical problems encountered during femoral reconstruction

“…In order to define strict parameters to predict the use of modular stems in DDH, Peters et al (8) carried out a retrospective analysis of 79 patients' preoperative radiographs. Based on the primary surgeon's criteria of selecting modular components when an intraoperative femoral neck anteversion of at least 25° is found, they established that hips in which modular stems were chosen had: a higher femoral anteversion angle (≥32°); a higher neck-shaft angle (≥142°) and a smaller lateral neck-shaft angle (≤153°).…”

Preoperative Planning for Total Hip Arthroplasty for Neglected Developmental Dysplasia of the Hip

“…With a modular stem, the stem anteversion can be set freely and precisely according to the angle we need. Peters et al . predicted the utility of the modular stem with plain films, and concluded that a modular stem should be used during surgery if the neck‐shaft angle in anteroposterior radiographs is >142°, the lateral neck‐shaft angle is <153°, and the calculated femoral anteversion is >32°.…”