Increased hip flexion angle and protrusion of the anterior acetabular component can predict symptomatic iliopsoas impingement after total hip arthroplasty: a retrospective study

Abstract

Background: Iliopsoas impingement (IPI) is a known complication of total hip arthroplasty (THA). The aim of this study was to identify risk factors and the cut-off cup protrusion length for symptomatic IPI. Methods: We retrospectively reviewed 218 hips (46 men, 172 women) of 190 consecutive Japanese patients who underwent primary THA at our institution. Hips with IPI ( n = 24) and control hips ( n = 194) were compared according to age, body mass index, and clinical scores. We evaluated leg-length discrepancy, global offset, implant alignment angles, pelvic inclination, and anterior cup protrusion on plain radiographs and computed tomography scans. Results: Symptomatic IPI had an incidence of 11.0% and a predilection for hips with osteonecrosis. Pre- and postoperative hip flexion angles were significantly greater in hips with symptomatic IPI ( p = 0.013 and p = 0.006, respectively). Cup protrusion length was significantly greater in hips with IPI (4.7 mm vs. 1.4 mm; p = 0.001). Receiver-operating characteristic curve analysis identified a threshold cup protrusion length of 3.9 mm (sensitivity 0.89, specificity 0.63) for symptomatic IPI. The incidence of symptomatic IPI tended to be lower in patients with greater posterior pelvic sagittal inclination despite the cup protrusion length being greater. Conclusions: An increased hip flexion angle and protrusion of the anterior acetabular component predicted symptomatic IPI. The threshold cup protrusion length suggesting mild IPI might be about 3.9 mm and could be useful for identifying candidates for conservative treatment.

Satisfactory mid‐term clinical outcomes of endoscopic tenotomy for iliopsoas tendinopathy following total hip arthroplasty

“…There are numerous possible causes for iliopsoas tendinopathy following THA, including iliopsoas impingement against a bulging screw or protruding cement. However, the most commonly reported risk factor is cup overhang [4,10,19,34,37,40], with some studies reporting cup overhang, regardless of the amount, to be a risk factor for iliopsoas tendinopathy [4,34,37], while others reported specific thresholds, such as axial cup overhang >12 mm [10,40] and/or sagittal cup overhang >4 mm [40]. This study assessed if cup position influenced posttenotomy clinical scores and found that the improvement in mHHS decreased with increasing sagittal cup overhang at a follow-up ≥ 5 years, with cup overhang measurements having excellent interobserver agreement.…”

“…Iliopsoas impingement against an overhanging cup [13,40], a bulging screw or protruding cement [36] could cause iliopsoas tendinopathy, which is often underdiagnosed when investigating the cause of groin pain [9,11,20]. Recent studies have reported an incidence of symptomatic iliopsoas tendinopathy between 2% and 11% following primary THA [4,23,34,37,40,44].…”