Bone Jt Open. 2023 Jan; 4(1): 3–12.

Interpositional Arthroplasty Using Mammary Capsule for Finger Joints: A Novel Technique

Max Hardwick-Morris, BEng (Hons I), Research Manager, PhD Candidate,corresponding author 1 , 2 Joshua Twiggs, PhD, Head of Research & Development, 1 Brad Miles, PhD, Chief Technical Officer, 1 Rami M. A. Al-Dirini, PhD, Lecturer in Biomedical Engineering, 2 Mark Taylor, PhD, Professor, 2 Jitendra Balakumar, MBBS, FRACS, Consultant Orthopaedic Surgeon, 3 and William L. Walter, MBBS, FRACS, FAOrthA, PhD, Professor Orthopaedic Surgery 4 , 5


Iliopsoas impingement occurs in 4% to 30% of patients after undergoing total hip arthroplasty (THA). Despite a relatively high incidence, there are few attempts at modelling impingement between the iliopsoas and acetabular component, and no attempts at modelling this in a representative cohort of subjects. The purpose of this study was to develop a novel computational model for quantifying the impingement between the iliopsoas and acetabular component and validate its utility in a case-controlled investigation.


This was a retrospective cohort study of patients who underwent THA surgery that included 23 symptomatic patients diagnosed with iliopsoas tendonitis, and 23 patients not diagnosed with iliopsoas tendonitis. All patients received postoperative CT imaging, postoperative standing radiography, and had minimum six months’ follow-up. 3D models of each patient’s prosthetic and bony anatomy were generated, landmarked, and simulated in a novel iliopsoas impingement detection model in supine and standing pelvic positions. Logistic regression models were implemented to determine if the probability of pain could be significantly predicted. Receiver operating characteristic curves were generated to determine the model’s sensitivity, specificity, and area under the curve (AUC).


Highly significant differences between the symptomatic and asymptomatic cohorts were observed for iliopsoas impingement. Logistic regression models determined that the impingement values significantly predicted the probability of groin pain. The simulation had a sensitivity of 74%, specificity of 100%, and an AUC of 0.86.


We developed a computational model that can quantify iliopsoas impingement and verified its accuracy in a case-controlled investigation. This tool has the potential to be used preoperatively, to guide decisions about optimal cup placement, and postoperatively, to assist in the diagnosis of iliopsoas tendonitis.

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