Traditional radiographic criteria might underestimate or fail to detect subtle types of acetabular dysplasia. Acetabular sector angles (ASA) can measure the degree of anterior and posterior coverage of the femoral head on computed tomography (CT). This study aims to determine ASA values at different axial levels in a cohort of (1) asymptomatic, high-functioning hips without underlying hip pathology (controls); and (2) symptomatic, dysplastic hips that underwent periacetabular osteotomy (PAO). Thereby, we aimed to define CT-based thresholds for hip dysplasia and its subtypes.

This is an IRB approved cross-sectional study of 51 high functioning, asymptomatic patients (102 hips) (Oxford Hip Score >43), without signs of osteoarthritis (Tönnis grade≤1), who underwent a CT scan of the pelvis (mean age: 52.1±5.5 years; 52.9% females); and 66 patients (72 hips) with symptomatic hip dysplasia treated with peri-acetabular osteotomy (PAO) (mean age: 29.3±7.3 years; 85.9% females). Anterior and posterior acetabular sector angles (AASA & PASA) were measured by two observers at three CT axial levels to determine equatorial, intermediate, and proximal ASA. Inter- and intra-observer reliability coefficient was high (between 0.882–0.992). Cut-off values for acetabular deficiency were determined based on Receiver Operating Characteristic (ROC) curve analysis, area under the curve (AUC) was calculated.

The dysplastic group had significantly smaller ASAs compared to the Control Group, AUC was the highest at the proximal and intermediate PASA. Controls had a mean proximal PASA of 162°±17°, with a cut-off value for dysplasia of 137° (AUC: 0.908). At the intermediate level, the mean PASA of controls was 117°±11°, with a cut-off value of 107° (AUC 0.904). Cut-off for anterior dysplasia was 133° for proximal AASA (AUC 0.859) and 57° for equatorial AASA (AUC 0.868). Cut-off for posterior dysplasia was 102° for intermediate PASA (AUC 0.933).

Measurement of ASA on CT is a reliable tool to identify dysplastic hips with high diagnostic accuracy. Posterior ASA less than 137° at the proximal level, and 107° at the intermediate level should alert clinicians of the presence of dysplasia.

The gold standard treatment of hip dysplasia is a peri-acetabular osteotomy (PAO). Labral tears are seen in the majority of patients presenting with hip dysplasia and diagnosed using Magnetic Resonance Imaging (MRI). The goal was to (1) evaluate utility/value of MRI in patients undergoing hip arthroscopy at time of PAO, and (2) determine whether MRI findings of labral pathology can predict outcome.

A prospective randomized controlled trial was conducted at tertiary institutions, comparing patients with hip dysplasia treated with isolated PAO versus PAO with adjunct hip arthroscopy. This study was a subgroup analysis on 74 patients allocated to PAO and adjunct hip arthroscopy (age 26±8 years; 89.2% females). All patients underwent radiographic and MRI assessment using a 1.5-Tesla with or 3-Tesla MRI without arthrography to detect labral or cartilage pathology. Clinical outcome was assessed using international Hip Outcome Tool-33 (iHOT).

74% of patients (55/74) were pre-operatively diagnosed with a labral tear on MRI. Among these, 41 underwent labral treatment (74%); whilst among those without a labral tear on MRI, 42% underwent labral treatment (8/19). MRI had a high sensitivity (84%), but a low specificity (56%) for labral pathology (p=0.053). There was no difference in pre-operative (31.3±16.0 vs. 37.3±14.9; p=0.123) and post-operative iHOT (77.7±22.2 vs. 75.2±23.5; p=0.676) between patients with and without labral pathology on MRI.

Value of MRI in the diagnostic work-up of a patient with hip dysplasia is limited. MRI had a high sensitivity (84%), but low specificity (44%) to identify labral pathology in patients with hip dysplasia. Consequently, standard clinical MRI had little value as a predictor of outcome with no differences in PROM scores between patients with and without a labral tear on MRI. Treatment of labral pathology in patients with hip dysplasia remains controversial. The results of this subgroup analysis of a prospective, multi-centre RCT do not show improved outcome among patients with dysplasia treated with labral repair.

Femoroacetabular impingement (FAI) results from a morphological deformity of the hip and is associated with osteoarthritis (OA). Increased bone mineral density (BMD) is observed in the antero-superior acetabulum rim where impingement occurs. It is hypothesized that the repeated abnormal contact leads to damage of the cartilage layer, but could also cause a bone remodelling response according to Wolff's Law. Thus the goal of this study was to assess the relationship between bone metabolic activity measured by PET and BMD measured in CT scans.

Five participants with asymptomatic cam deformity, three patients with uni-lateral symptomatic cam FAI and three healthy controls were scanned in a 3T PET-MRI scanner following injection with [18F]NaF. Bone remodelling activity was quantified with Standard Uptake Values (SUVs). SUVmax was analyzed in the antero-superior acetabular rim, femoral head and head-neck junction. In these same regions, BMD was calculated from CT scans using the calibration phantom included in the scan. The relationship between SUVmax and BMD from corresponding regions was assessed using the coefficient of determination (R²) from linear regression.

High bone activity was seen in the cam deformity and acetabular rim. SUVmax was negatively correlated with BMD in the antero-superior region of the acetabulum (R²=0.30, p=0.08). SUVmax was positively correlated with BMD in the antero-superior head-neck junction of the femur (R²=0.359, p=0.067). Correlations were weak in other regions.

Elevated bone turnover was seen in patients with a cam deformity but the relationship to BMD was moderate. This study demonstrates a pathomechanism of hip degeneration associated with FAI deformities, consistent with Wolff's law and the proposed mechanical cause of hip degeneration in FAI. [18F]-NaF PET SUV may be a biomarker of degeneration, especially in early stages of degeneration, when joint preservation surgery is likely to be the most successful.

Femoro-acetabular impingement involves a deformity of the hip joint and is associated with hip osteoarthritis. Although 15% of the asymptomatic population exhibits a deformity, it is not clear who will develop symptoms. Current diagnostic imaging measures have either low specificity or low sensitivity and do not consider the dynamic nature of impingement during daily activities. The goal of this study is to determine stresses in the cartilage, subchondral bone and labrum of normal and impinging hips during activities such as walking and sitting down.

Quantitative CT scans were obtained of a healthy Control and a participant with a symptomatic femoral cam deformity (‘Bump’). 3D models of the hip were created from automatic segmentation of CT scans. Cartilage layers were added so the articular surface was the mid-line of the joint. Finite element meshes were generated in each region. Bone elastic modulus was assigned element-by-element, calculated from CT intensity converted to bone mineral density using a calibration phantom. Cartilage was modelled as poroelastic, E=0.467 MPa, v=0.167, and permeability 3×10^-16 m⁴/N s. The pelvis was fixed while rotations and contact forces from Bergmann et al. (2001) were applied to the femur over one load cycle for walking and sitting in a chair. All analyses were performed in FEBio.

High shear stresses were seen near the acetabular cartilage-labrum junction in the Bump model, up to 0.12 MPa for walking and were much higher than in the Control.

Patient-specific modelling can be used to assess contact and tissue stresses during different activities to better understand the risk of degeneration in individuals, especially for activities that involve high hip flexion. The high stresses at the cartilage labrum interface could explain so-called bucket-handle tears of the labrum.

Introduction

Interactions between hip, pelvis and spine, as abnormal spinopelvic movements, have been associated with inferior outcomes following total hip arthroplasty (THA). Changes in pelvis position lead to a mutual change in functional cup orientation, with both pelvic tilt and rotation having a significant effect on version. Hip osteoarthritis (OA) patients have shown reduced hip kinematics which may place increased demands on the pelvis and the spine.

Sagittal and coronal planes assessments are commonly done as these can be adequately studied with anteroposterior and lateral radiographs. However, abnormal pelvis rotation is likely to compromise the outcome as they have a detrimental effect on cup orientation and increased impingement risk. This study aims to determine the association between dynamic motion and radiographic sagittal assessments; and examine the association between axial and sagittal spinal and pelvic kinematics between hip OA patients and healthy controls (CTRL).

Purpose

Spinopelvic parameters are associated with the development of symptomatic femoroacetabular impingement and subsequent osteoarthritis. Pelvic incidence (PI) characterizes the sagittal profile of the pelvis and is important in the regulation of both lumbar lordosis and pelvic orientation (i.e. tilt). The purpose of this imaging-based study was to test the association between PI and acetabular morphology.

Background

Over 35% of surgeons in the United States, and 10% in Canada use the direct anterior approach for primary total hip arthroplasty (THA). Some of the key barriers in its wider adoption are the learning curve and associated increased risk of adverse events. The purpose of this study was to determine the adoption rate as well as 90-day re-admission and adverse event of the anterior approach in a community-based hospital.

Background

For total hip arthroplasty (THA), cognitive training prior to performing real surgery may be an effective adjunct alongside simulation to shorten the learning curve. This study sought to create a cognitive training tool to perform direct anterior approach THA, validated by expert surgeons; and test its use as a training tool compared to conventional material.

Background

Virtual Reality (VR) uses headsets and motion-tracked controllers so surgeons can perform simulated total hip arthroplasty (THA) in a fully-immersive, interactive 3D operating theatre. The aim of this study was to investigate the effect of laboratory-based VR training on the ability of surgical trainees to perform direct anterior approach THA on cadavers.

Introduction

Acetabular retroversion (AR) can cause pain and early osteoarthritis. The sagittal pelvic position or pelvic tilt (PT)has a direct relationship with acetabular orientation. As the pelvis tilts anteriorly, PT reduces and AR increases. Therefore, AR may be a deformity secondary to abnormal PT (functional retroversion) or an anatomical deformity of the acetabulum and/or pelvic ring.

This study aims to:

Define PT at presentation is in AR patients and whether this is different to controls (volunteers without pain).

Introduction

This study aims to determine how the acetabular version changes during the key developmental stage of adolescence, and what contributes to this change. In addition, we examined whether patient factors (BMI, activity levels) or the femoral-sided anatomy contribute to any observed changes.

Introduction

Acetabular dysplasia is associated with an increased risk of hip pain and early development of osteoarthritis (OA). The Bernese peri-acetabular osteotomy (PAO) is the most well-established technique in the Western world for the treatment of symptomatic acetabular dysplasia. This case-control study aims to assess whether the severity of acetabular dysplasia has an effect on outcome following Peri-Acetabular Osteotomy (PAO) and/or the ability to achieve desired acetabular correction.

The anterior/Hueter approach to the hip was first described in 1883. It was then popularised in the 1940s by Judet in France using an orthopaedic positioning table which at the time was also used to treat a variety of orthopaedic injuries. In North America its use for joint replacements was limited to a few surgeons such as Kris Keggi in Connecticut using a regular surgical table as well as a select few surgeons (Joel Matta) who had trained with Emile Letournel, a student of Judet. It is fair to say that this anatomical approach to the hip was never forgotten but rather put aside as industry and clinicians focused on critical issues of implant breakage and failure as well as the larger problem of wear-related osteolysis. As we have made significant improvements in implant durability and fixation, the focus has now shifted on optimizing patient recovery and minimizing length of stay while providing the same quality of care. In these regards, the anterior approach provides a valid alternative to standard approaches to the hip due to its low risk of dislocation and minimal disruption to the musculature. In addition, the capacity of intra-operative imaging with the patient in the supine position provides assessment of component orientation as well as leg lengths. More importantly, like the advent of better instrumentation for the anterior approach, the use and optimization of the positioning table facilitates the execution of the anterior approach i.e. one assistant and no soft tissue release.

Summary

The cartilage layer from cam-type femoroacetabular impingement deformities had lower stiffness and increased permeability compared to normal cartilage. This is consistent with osteoarthritis and supports the hypothesis of abnormal contact stresses.

Summary Statement

This study quantifies compositional differences in cartilage between CAM deformities of symptomatic FAI patients and normal cadaver controls. It shows a resemblance of CAM-FAI cartilage with those of osteoarthritic hips, objectively supporting previous hypothesis of abnormal contact stresses in CAM-FAI.

Hip resurfacing arthroplasty has become a popular treatment option for younger active patients. The early published results from designing surgeons/centers have been favourable. We undertook a prospective multi-center trial to determine the outcome of hip resurfacing arthroplasty at independent centers. The clinical, radiographic and functional results were assessed.

A prospective IRB approved study was initiated in July 2003 to assess the outcome of hip resurfacing arthroplasty using a contemporary design implant. (Conserve Plus - Wright Medical Technology) Disease specific (Harris Hip Score/WOMAC) and global (Rand self assessment index) outcome measures were used. Radiographs were reviewed for component position and migration as well as any signs of lysis or loosening. Complications and re-operations were recorded.

A total of one hundred and eighty-eight patients have been enrolled in the study to date. One hundred and four patients have a minimum one year follow-up and forty-six patients have a minimum two year follow-up. Mean Harris Hip Scores (pre-op, one year, two years) were fifty-five, eighty-nine and ninety-one. Mean WOMAC pain scores were forty-seven, ninety and ninety. Mean WOMAC stiffness scores were forty, seventy-eight and eighty-two. Mean WOMAC function scores were forty-six, eighty-seven and eighty. RAND physical function mean scores were thirty-three, seventy-six and seventy-six and the RAND physical limitations mean scores were nineteen, sixty-seven and seventy-five. Radiographic analysis showed average cup abduction to be forty-six degrees (range twenty-six to sixty-three). Average femoral stem position was one hundred and thiry-eight degrees (range one hundred and eighteen to one hundred and fifty-seven). Nine patients have been revised to date (4.8%). Four for acetabular loosening, two for neck fracture, one for femoral loosening, one for impingement and one for persistent pain. There have been eight other patients requiring re-operation without revision. Medical complications occurred in fifteen patients.

Early results have demonstrated a good return of function in patients with hip resurfacing arthroplasty. A high early revision rate (4.8%) was seen in our study. Technical factors appear to be the main contributor to the high early complication rate. Hip resurfacing is associated with a steep learning curve. We continue to utilise hip resurfacing in select patients but recommend caution for those who are new to the technique.

Cementless femoral fixation is the gold standard in revision hip arthroplasty. Distal fixation is achieved using either a cobalt chrome or titanium stem. The purpose of this study is to report the long-term survivorship and clinical outcome of a titanium, long-stemmed, load-bearing calcar-replacement femoral component from an independent centre.

Eighty-one patients (average seventy-four years, range thirty-five to ninety-one) underwent hip arthroplasty with the Mallory-Head calcar-replacement femoral component, by a single surgeon. There were thirty-eight males and forty-three females with fifty-four hips initially revised for aseptic loosening, thirteen for peri-prosthetic fracture, and five for infection as a two-stage procedure. The implant was used as a primary device in eight patients with deformed proximal femurs. At most-recent follow-up, radiographic analysis was conducted and clinical outcome scoring was assessed using the SF-12, Harris Hip Score, and WOMAC questionnaire for surviving patients. Complications were also reviewed.

At a mean follow-up of 7.4 years (range four to fifteen), eight patients have died. There was one deep infection, three DVT’s, and two dislocations in the perioperative period. Six femoral stems have ultimately required another revision surgery for aseptic loosening, two for infection, and 1 for implant fracture at a mean of 5.6 years after initial revision. Four patients required removal of the proximal trochanteric bolt due to breakage or loosening. Overall survival of the implant at five years is 95% (CI 0.87–0.98) and 87% (CI 0.72–0.94) at ten years.

The clinical outcome of the Mallory-Head calcar-replacement femoral revision stem is reported from an independent centre. Although the results are encouraging, it would appear that proximal load-bearing fixation with the calcar-replacement stem is not as reliable as distal fixation. The use of a trochanteric bolt was associated with fracture of the greater trochanter or need for a separate surgical procedure for removal. For this series, there was an overall 11% failure rate at a mean follow-up of 7.4 years. The mechanical failure rate is 7.4%. Our overall and mechanical failure rates are somewhat higher than those of the implant developers, who reported 94% overall survival, and a 1.9% mechanical failure rate at a mean follow-up of eleven years.

Introduction and Aims: The importance in assessing clinical outcome is critical in evaluation of total hip replacement. There is now a sufficient body of evidence that activity level is correlated to wear of total hip replacement and wear to the longevity of that implant. The purpose of this study was, using the UCLA activity scale, to evaluate how activity relates to both health-related and disease-specific questionnaires.

Method: One hundred and fifty-two patients who underwent primary hip arthroplasty filled out the health-related questionnaire – SF-12 survey, which has a mental and physical component – with an average score of 50 in the general population for each category. The same day they were clinically evaluated, using the UCLA and Harris hip scoring systems. All patients were evaluated by the same surgeon; at least two years post-surgery, with an average follow-up of 5.2 years. Patient average age at surgery was 52.4, with 66% male. To assess the strength of the relationship between SF-12, UCLA and Harris scores, linear regression analysis was used.

Results: All individual UCLA scores were significantly correlated (p< 0.05) to SF-12 physical component, except for walking. When the single item UCLA activity score was added to Harris hip score, R squared raised from 0.43 to 0.53 in predicting quality of life. The single item Activity from the UCLA scoring system explained 38% of the variability in SF-12 physical component. With the linear regression analysis, all individual UCLA scores were independently significantly correlated (p< 0.05) to SF-12 physical component, except for walking. When the single item UCLA activity score was added to Harris hip score, R squared raised from 0.43 to 0.53 in predicting quality of life represented by the physical component of the SF-12.

Conclusion: Our study has shown that the UCLA activity scale is not only important to assess wear of the bearing surface, but also provides additional information in assessing the clinical outcome of total hip replacement. The single item Activity from the UCLA scoring system explained 38% of the variability in SF-12 physical component and demonstrates the need to integrate activity in outcome measurements after hip arthroplasty.

Purpose: Treatment of Ficat stage III and IV femoral head necrosis is a major problem and a subject of debate because of the young age of the patients and the disappointing results obtained with total hip arthroplasty (THA). We present our experience with hybrid twin cups cemented on the femoral side and not cemented on the acetabular side using a metal-on-metal bearing to determine the mechanisms leading to revision and to assess mid-term outcomes.

Material and methods: Fifty-four hips with osteonecrosis were treated with the twin cup and studied at minimum two years follow-up. Mean patient age was 40.4 years (16–56), 13% of the patients were women and 87% men. The Ficat score (13% stage III, and 87% stage IV) was used. A prior operation had been performed in 33% of the hips.

Results: Mean follow-up was 4.4 years (2.1–6.8). Four hips required revision, three for femoral loosening after mean 46.3 months, and one for fracture of the acetabular wall immediately after the operation. The mean UCLA scores showed improvement: 3.3 to 9.3 for pain, 5.5 to 9.7 for walking, 5.0 to 9.4 for physical functioning, and 4.2 to 7.2 for activity. Physical and mental items on the SF-12 showed that normal quality-of-life was restored (compared with the general population in the United States).

Discussion: Although it is too early to speculate concerning the long-term outcome of these twin cups implanted in young patients with hip osteonecrosis, the clinical results have been encouraging. This prosthesis is an interesting alternative to the adjusted cup in the event of acetabular cartilage damage. If necessary, the acetabular component can be saved during conversion to THA without any deleterious clinical effects.

Purpose: The purpose of this work was to evaluate clinical and radiographic factors affecting early outcome of resurfaced hip prostheses in young adults.

Material and methods: Among 119 hybrid resurfaced prostheses with a metal-on-metal bearing implanted in patients aged 40 years or less, 94 were retained for analysis at minimum two years follow-up or failure. Mean age was 34.2 years (15–40), 71% of the patients were men and 14% had had a prior hip operation. A risk index (SARI) was developed from the Chandler index.

Results: Mean follow-up was three years (2–5). Items of the UCLA score improved: pain 3.1 versus 9.2, walking 5.8 versus 9.4 (p=0.00). Three hips required revision total hip arthroplasty at mean 27 months (2–50) and ten patients had radiographically significant modifications. Comparing these 17 hips with the 47 others, indexes showed 4.7 versus 2.6 for the SARI (p=0.000) and 2.6 versus 2.8 for the Chandler score (p=0.358). There was no correlation with reconstruction mechanics, function, walking or scoring. Valgus implantation of the femoral piece and the lateral lever arm were significantly correlated (r=0.39, p< 0.001).

Discussion: If the SARI was > 3, the relative risk of early complications was 12-fold higher than if the SARI was 3. Because of the distinct fixation of the femoral implant, a SARI=2 was attributed when there was a cyst in the femoral head and weight was < 82 kg (lower weight correlated with smaller implant, r=0.60). This index can be used to improve patient selection in order to define the role of arthroplasty resurfacing in the treatment of hip degeneration.