Iliopsoas impingement occurs in between 5-30% of patients after hip arthroplasty and has been thought to only be caused by an oversized cup, cup malpositioning, or the depth of the psoas valley. However, no study has associated the relationship between preoperative measurements with the risk of impingement. This study sought to assess impingement between the iliopsoas and acetabular cup using a novel validated model to determine the risk factors for iliopsoas impingement.

413 patients received lower limb CT scans and lateral x-rays that were segmented, landmarked, and measured using a validated preoperative planning protocol. Implants were positioned according to the preference of ten experienced surgeons. The segmented bones were transformed to the standing reference frame and simulated with a novel computational model that detects impingement between the iliopsoas and acetabular cup. Definitions of patients at-risk and not at-risk of impingement were defined from a previous validation study of the simulation. At-risk patients were propensity score matched to not at-risk patients.

21% of patients were assessed as being at-risk of iliopsoas impingement. Significant differences between at-risk patients and not at-risk patients were observed in standing pelvic tilt (p << 0.01), standing femoral internal rotation (p << 0.01), medio-lateral centre-of-rotation (COR) change (p << 0.01), supine cup anteversion (p << 0.01), pre- to postoperative cup offset change (p << 0.001), postoperative gross offset (p = 0.009), and supero-inferior COR change (p = 0.02).

Impingement between the iliopsoas and acetabular cup is under-studied and may be more common than is published in the literature. Previously it has been thought to only be related to cup size or positioning. However, we have observed significant differences between at-risk and not at-risk patients in additional measurements. This indicates that its occurrence is more complex than simply being related to cup position.

Aims

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.

Aims

Slipped upper femoral epiphysis (SUFE) has well documented biochemical and mechanical risk factors. Femoral and acetabular morphologies seem to be equally important. Acetabular retroversion has a low prevalence in asymptomatic adults. Hips with dysplasia, osteoarthritis, and Perthes’ disease, however, have higher rates, ranging from 18% to 48%. The aim of our study was to assess the prevalence of acetabular retroversion in patients presenting with SUFE using both validated radiological signs and tomographical measurements.

Abstract

Introduction Pelvic ring disruptions have well established biomechanical forces that correlate with fracture pattern. These patterns have considerable soft tissue and ligamentous disruptions associated with high velocity vectors which result in unstable injuries. This study critically evaluates the functional outcome of anatomically and or haemodynamically unstable pelvic ring disruptions treated with operative management and presents a retrospective analysis of injury pattern, surgical therapy and complications in surgically treated Tile B and Tile C disruptions.

Methods This study is a retrospective review of results of the operative management of pelvic fractures at the Alfred Hospital, Melbourne over the period of May 1997 to May 2001 (one to four years) using the Iowa Pelvic Score (Martin-American Academy Meeting 1999) to assess functional outcome. Initial screening resulted in 204 patients with pelvic disruptions via DRG coding. Of this 65 patients were managed operatively and only 34 patients were subquently included in the study. Exclusion criteria were; residual cognitive defect, hip or ace-tabular injury, spinal injury with neurological deficit, repeat trauma or ongoing litigation. The inital data gathered included; age, sex, type of accident, Tile classification, neurological injury, urogential injury, type of treatment, adequacy of treatment, post-operative complications, length of hospital and stay in rehabilitation. A follow-up survey was performed for each of these patients by telephone to obtain a post-operative functional outcome score. Thirty two of the 34 patient were able to complete the survey.

Results Thirty-four patients were included in the study with 29 (85%) males and five (14%) females. The modes of injury were as follows: five motor car occupants, 13 motorbike riders, three pedestrians struck by motorcar, three falls, three occupational and seven other. Twenty-seven were classified as Tile B and seven Tile C. These fractures were treated with the following; external fixation alone was used in four patients, external fixation followed by anterior plating was used for 18 patients, anterior plating and posterior ilio-sacral screws were used for nine patients, three patients received both anterior and posteior plate fixation. The mean number of operations to stabilize the disruptions was two. The major complication incurred by most of the patients was pin site infection. The mean length of hospital stay was 25 days and the mean length of rehabilitation stay was 35 days. Of the 32 patients interviewed all had function outcome scores greater than 70 (good). Most (n=13) of them returned to full time work. All reported cosmetic changes in their pelvis.

Conclusions We feel that this study provided good quality retrospective data for the demographics and surgical therapy used to stabilize pelvic ring disruptions that are unstable. These results were consistent with current belief that internal fixation of pelvic fractures produced good functional outcome.