Changes in acetabular component alignment due to screw fixation in patients with hip dysplasia

Abstract

Introduction: Adequate initial stability of the acetabular cup is essential for total hip arthroplasty (THA). However, changes in the alignment of the acetabular component caused by screw fixation are concerning in patients with inadequate bone stock. This study aimed to investigate the effects of screw fixation on the alignment of the acetabular component in THA patients with hip dysplasia. Methods: We retrospectively examined 256 hips (range 28–87 years) that underwent THA using a navigation system. Patients were divided into 2 groups based on the presence or absence of changes in the alignment of the intraoperative acetabular cup, and univariate and multivariate analyses were performed to identify factors that were predictive of changes in acetabular component alignment after screw fixation in 2 dimensions: inclination and anteversion. Results: Screw fixation led to a mean change in inclination of 1.6° (range 0–10°) and a mean change in anteversion of 1.4° (range 0–14°). The Crowe classification, the presence of bone cysts, and the use of an inferior quadrant screw were identified as factors that correlated with acetabular cup alignment changes in inclination (odds ratios, 6.01, 5.94 and 0.03, respectively). Only the Crowe classification was identified as a factor that correlated with intraoperative alignment changes in anteversion (odds ratio, 2.08). Conclusions: Screw fixation altered the acetabular cup alignment. The inclination changes were related to the extent of the dysplasia, and the risk was reduced when the inferior quadrant screw was used. Surgeons should use caution during screw fixation in THAs performed on severely dysplastic hips.

The press-fit technique without screws and bone graft can be used as an alternative method in Crowe type II and III hip dysplasia

“…The initial stability of the cementless acetabular component is crucial because insufficient primary cup fixation may lead to early loosening [ 17 , 18 ]. In a recent study, Du et al suggested that more than 75.5% cup coverage values with or without screws can provide sufficient stability in patients with Crowe II and III DDH [ 8 ].…”

“…The initial stability of a cementless acetabular component is crucial because insufficient primary cup fixation may lead to early loosening [ 17 , 18 ]. Various reconstruction methods to obtain initial stability of the acetabular cup in patients with DDH have been described, including the press-fit technique without screws, using screws, a structural bone graft, and a small cup placed in an anatomical location or a superior position [ 19 – 21 ].…”

A Change in the Classical Order of Setting of Porous Metal Augments with Locked Cups in Hip Revision Surgery: Technical Note and Case Report

“…The locking mechanism of the screws may also avoid the change of the position of the cup that has been demonstrated with nonlocked screw cups [ 19 , 20 ], allowing more accuracy on the final version and the center of rotation. This statement is not applicable, of course, to cavitary defects in which foundation augments (“footing”) are employed like in Case 1 that must be set first.…”

Proposal of accurate cup placement procedure during total hip arthroplasty based on pelvic tilt discrepancies in the lateral position

“…The study participants signed appropriate written consent forms after the content was explained and discussed (n = 80) and underwent primary THA using HipAlign New Lateral. Since the cup orientation may change with screw use 8 , 9 , cases with additional screws during THAs were excluded from analysis (n = 14). In addition, cases in which the target radiographic anteversion (RA) was 20° were also excluded (n = 2).…”