Accuracy of iliac crest reference pin placement in total hip arthroplasty: a CT-based analysis of risk factors for cortical perforation

Abstract

Introduction

Accurate iliac crest reference pin placement is essential for safe navigation-assisted total hip arthroplasty (THA). Although complications are uncommon, inaccurate placement may cause neurovascular injury. This study aimed to evaluate pin insertion accuracy using postoperative computed tomography (CT), identify risk factors for cortical perforation, and determine whether CT-detected cortical perforation was associated with postoperative acetabular cup positioning accuracy.

Materials and methods

We retrospectively analyzed 200 primary THAs performed using portable or CT-based navigation between December 2022 and July 2025. Pin position was assessed on CT 1 week postoperatively and classified as complete intraosseous insertion or cortical perforation. Risk factors were examined using univariable and multivariable logistic regression analyses. Perforation direction was evaluated using Firth’s penalized logistic regression. Postoperative cup positioning accuracy was assessed using CT-based radiographic inclination (RI), radiographic anteversion (RA), and absolute errors from target angles of 40° for RI and 15° for RA.

Results

Cortical perforation occurred in 70 of 200 hips (35.0%): 32 medial and 38 lateral. On a pin-by-pin basis, 113 of 400 pins (28.3%) demonstrated perforation. In multivariable analysis, smaller ASIS width, lateral decubitus positioning, and 4-mm pin use independently predicted cortical perforation. Medial perforation was independently associated with lateral decubitus positioning, 4-mm pin use, and smaller iliac wing angle in Firth’s model. RI, RA, absolute RI error, and absolute RA error did not differ significantly between the intraosseous and cortical perforation groups. All hips in both groups were within 10° of the target angles for both RI and RA. No dislocation or revision surgery occurred in either group.

Conclusions

CT-detected cortical perforation of iliac crest reference pins was common but was rarely accompanied by clinically apparent complications and was not associated with inferior postoperative cup positioning accuracy. Perforation risk was influenced by insertion position, platform-associated instrumentation, and pelvic morphology. These findings should be interpreted primarily as a technical accuracy endpoint rather than as evidence of clinically proven harm. The clinical significance of CT-detected cortical perforation remains uncertain, and particular attention should be paid to minimizing medial cortical breach.