The primary treatment goal for patients with femoroacetabular impingement syndrome, a common hip condition in athletes, is to improve pain and function. In selected patients, in the short term following intervention, arthroscopic hip surgery is superior to a pragmatic NHS- type physiotherapy programme. Here, we report the three-year follow-up results from the FemoroAcetabular Impingement Trial (FAIT), comparing arthroscopic hip surgery with physiotherapy in the management of patients with femoroacetabular impingement (FAI) syndrome.

Two-group parallel, assessor-blinded, pragmatic randomised controlled study across seven NHS England sites. 222 participants aged 18 to 60 years with FAI syndrome confirmed clinically and radiologically were randomised (1:1) to receive arthroscopic hip surgery (n = 112) or physiotherapy and activity modification (n = 110). We previously reported on the hip outcome score at eight months. The primary outcome measure of this study was minimum Joint Space Width (mJSW) on Anteroposterior Radiograph at 38 months post randomisation. Secondary outcome measures included the Hip Outcome Score and Scoring Hip Osteoarthritis with MRI (SHOMRI) score.

Minimum Joint Space Width data were available for 101 participants (45%) at 38 months post randomisation. Hip outcome score and MRI data were available for 77% and 62% of participants respectively. mJSW was higher in the arthroscopy group (mean (SD) 3.34mm (1.01)) compared to the physiotherapy group (2.99mm (1.33)) at 38 months, p=0.017, however this did not exceed the minimally clinically important difference of 0.48mm. SHOMRI score was significantly lower in the arthroscopy group (mean (SD) 9.22 (11.43)) compared to the physiotherapy group (22.76 (15.26)), p-value <0.001. Hip outcome score was higher in the arthroscopy group (mean (SD) 84.2 (17.4)) compared with the physiotherapy group (74.2 (21.9)), p-value < 0.001).

Patients with FAI syndrome treated surgically may experience slowing of osteoarthritisprogression and superior pain and function compared with patients treated non- operatively.

There is a paucity of data available for the use of Total Femoral Arthroplasty (TFA) for joint reconstruction in the non-oncological setting. The aim of this study was to evaluate TFA outcomes with minimum 5-year follow-up.

This was a retrospective database study of TFAs performed at a UK tertiary referral revision arthroplasty unit. Inclusion criteria were patients undergoing TFA for non-oncological indications. We report demographics, indications for TFA, implant survivorship, clinical outcomes, and indications for re-operation.

A total of 39 TFAs were performed in 38 patients between 2015–2018 (median age 68 years, IQR 17, range 46–86), with 5.3 years’ (IQR 1.2, 4.1–18.8) follow-up; 3 patients had died. The most common indication (30/39, 77%) for TFA was periprosthetic joint infection (PJI) or fracture-related infection (FRI); and 23/39 (59%) had a prior periprosthetic fracture (PPF). TFA was performed with dual-mobility or constrained cups in 31/39 (79%) patients. Within the cohort, 12 TFAs (31%) required subsequent revision surgery: infection (7 TFAs, 18%) and instability (5 TFAs, 13%) were the most common indications. 90% of patients were ambulatory post-TFA; 2 patients required disarticulation due to recurrent PJI. While 31/39 (79%) were infection free at last follow-up, the remainder required long-term suppressive antibiotics.

This is the largest series of TFA for non-oncological indications. Though TFA has inherent risks of instability and infection, most patients are ambulant after surgery. Patients should be counselled on the risk of life-long antibiotics, or disarticulation when TFA fails.

Anterior approach total hip arthroplasty (AA-THA) has a steep learning curve, with higher complication rates in initial cases. Proper surgical case selection during the learning curve can reduce early risk. This study aims to identify patient and radiographic factors associated with AA-THA difficulty using Machine Learning (ML).

Consecutive primary AA-THA patients from two centres, operated by two expert surgeons, were enrolled (excluding patients with prior hip surgery and first 100 cases per surgeon). K- means prototype clustering – an unsupervised ML algorithm – was used with two variables - operative duration and surgical complications within 6 weeks - to cluster operations into difficult or standard groups.

Radiographic measurements (neck shaft angle, offset, LCEA, inter-teardrop distance, Tonnis grade) were measured by two independent observers. These factors, alongside patient factors (BMI, age, sex, laterality) were employed in a multivariate logistic regression analysis and used for k-means clustering. Significant continuous variables were investigated for predictive accuracy using Receiver Operator Characteristics (ROC).

Out of 328 THAs analyzed, 130 (40%) were classified as difficult and 198 (60%) as standard. Difficult group had a mean operative time of 106mins (range 99–116) with 2 complications, while standard group had a mean operative time of 77mins (range 69–86) with 0 complications. Decreasing inter-teardrop distance (odds ratio [OR] 0.97, 95% confidence interval [CI] 0.95–0.99, p = 0.03) and right-sided operations (OR 1.73, 95% CI 1.10–2.72, p = 0.02) were associated with operative difficulty. However, ROC analysis showed poor predictive accuracy for these factors alone, with area under the curve of 0.56. Inter-observer reliability was reported as excellent (ICC >0.7).

Right-sided hips (for right-hand dominant surgeons) and decreasing inter-teardrop distance were associated with case difficulty in AA-THA. These data could guide case selection during the learning phase. A larger dataset with more complications may reveal further factors.

Aims

Metal-on-metal hip resurfacing (MoM-HR) has seen decreased usage due to safety and longevity concerns. Joint registries have highlighted the risks in females, smaller hips, and hip dysplasia. This study aimed to identify if reported risk factors are linked to revision in a long-term follow-up of MoM-HR performed by a non-designer surgeon.

Acetabular retroversion (ARV) is a cause of femoroacetabular impingement leading to hip pain and reduced range of motion. We aimed to describe the radiological criteria used for diagnosing ARV in the literature and report on the outcomes of periacetabular osteotomy (PAO) and hip arthroscopy (HA) in its management.

A systematic review using PRISMA guidelines was conducted on the MEDLINE, CINAHL, EMBASE, COCHRANE database in December 2022. English-language studies reporting outcomes of PAO, or open or arthroscopic interventions for ARV were included.

From an initial 4203 studies, 21 non-randomised studies met the inclusion criteria.

Eleven studies evaluated HA for ARV, with average follow-up ranging from 1 to 5 years, for a cumulative number of 996 patients. Only 3/11 studies identified ARV using AP standardized pelvic radiographs. The most frequent signs describing ARV identified were: Ischial Spine Sign (98% of patients), Posterior Wall Sign (PWS, 94%) and Crossover Sign (COS, 64%); with mean Acetabular Retroversion Index (ARI) ranging from 33% to 35%. 39% of HA patients had all three radiographic signs. Clinically significant outcomes were reached by 33–78% of patients.

Eight studies evaluated PAO for ARV, with a follow-up ranging from 2 to 10 years, for a cumulative number of 379 patients. Five of the eight studies identified ARV using standardized radiographs. ISS, COS and PWS were positive in 54%, 97% and 81% of patients, respectively with 52% of PAO patients having all three radiographic signs. Mean ARI ranged from 36–41%. Clinically significant results were reported in 71%–78% of patients.

The diagnostic criteria for ARV is poorly defined in the literature, and the quality of evidence is low. Studies on HA are more likely to have used lenient diagnostic criteria. It remains difficult to recommend which cases maybe more suitable for treatment by HA rather than PAO.

Superior teamwork in the operating theatre is associated with improved technical performance and clinical outcomes. Yet modern rota patterns, workforce shortages, and increasing complexity of surgery, means that there is less familiarity between staff and the required choreography. Immersive Virtual Reality (iVR) can successfully train surgical staff individually, however iVR team training has yet to be investigated. We aimed to design a multiplayer iVR platform for anterior approach total hip arthroplasty (AA-THA) and assess if multiplayer iVR training was superior to single player training for acquisition of both technical and non-technical skills.

An iVR platform with choreographed roles for the surgeon and scrub nurse was developed using Cognitive Task Analysis. Forty participants were randomised to individual or team iVR training. Individually- trained participants practiced alongside virtual avatar counterparts, whilst teams trained live in pairs. Both groups underwent five iVR training sessions over 6-weeks. Subsequently, they underwent a real-life assessment in which they performed AA-THA on a high-fidelity model with real equipment in a simulated theatre. Teams performed together and individually trained participants were randomly paired up. Videos were marked by two blinded assessors recording the NOTSS, NOTECHS II and SPLINTS scores - validated technical and non-technical scores assessing surgeon and scrub nurse skills. Secondary outcomes were procedure time and number of technical errors.

Teams outperformed individually trained participants for non-technical skills in the real-world assessment (NOTSS 13.1 ± 1.5 vs 10.6 ± 1.6, p =0.002, NOTECHS-II score 51.7 ± 5.5 vs 42.3 ± 5.6, p=0.001 and SPLINTS 10 ± 1.2 vs 7.9 ± 1.6, p = 0.004). They completed the assessment 28.1% faster (27.2 minutes ± 5.5 vs 41.8 ±8.9, p<0.001), and made fewer than half the number of technical errors (10.4 ± 6.1 vs 22.6 ± 5.4, p<0.001).

Multiplayer training leads to faster surgery with fewer technical errors and the development of superior non-technical skills for anterior approach total hip arthroplasty. The convention of surgeons and nurses training separately, but undertaking real complex surgery together, can be supplanted by team training, delivered through immersive virtual reality.

Superior team performance in surgery leads to fewer technical errors, reduced mortality, and improved patient outcomes. Scrub nurses are a pivotal part of this team, however they have very little structured training, leading to high levels of stress, low confidence, inefficiency, and potential for harm. Immersive virtual reality (iVR) simulation has demonstrated excellent efficacy in training surgeons. We tested the efficacy of an iVR curriculum for training scrub nurses in performing their role in an anterior approach total hip arthroplasty (AA-THA).

Sixty nursing students were included in this study and randomised in a 1:1 ratio to learning the scrub nurse role for an AA-THA using either conventional training or iVR. The training was derived through expert consensus with senior surgeons, scrub nurses and industry reps. Conventional training consisted of a 1-hour seminar and 2 hours of e-learning where participants were taught the equipment and sequence of steps. The iVR training involved 3 separate hour-long sessions where participants performed the scrub nurse role with an avatar surgeon in a virtual operation. The primary outcome was their performance in a physical world practical objective assessment with real equipment. Data were confirmed parametric using the Shapiro-Wilk test and means compared using the independent samples student's t-test.

53 participants successfully completed the study (26 iVR, 27 conventional) with a mean age of 31±9 years. There were no significant differences in baseline characteristics or baseline knowledge test scores between the two groups (p>0.05). The iVR group significantly outperformed the conventionally trained group in the real-world assessment, scoring 66.9±17.9% vs 41.3±16.7%, p<0.0001.

iVR is an easily accessible, low cost training modality which could be integrated into scrub nursing curricula to address the current shortfall in training. Prolonged operating times are strongly associated with an increased risk of developing serious complications. By upskilling scrub nurses, operations may proceed more efficiently which in turn may improve patient safety.

Current evidence suggests that superior surgical team performance is linked to fewer intra-operative errors, reductions in mortality and even improved patient outcomes. Virtual reality has demonstrated excellent efficacy in training surgeons and scrub nurses individually, however its impact on training teams is currently unknown. This study aimed to assess if training together (scrub nurse and surgeon) in an innovative multiplayer virtual reality program was superior to single player training for novices learning anterior approach total hip arthroplasty (AA-THA).

40 participants (20 novice surgeons (CT1-ST3 level) and 20 novice scrub nurses) were enrolled in this study and randomised to individual or team virtual reality training. Individually-trained participants played with virtual avatar counterparts, whilst teams trained live in pairs (surgeon and scrub nurse). Both groups underwent 5 VR training sessions over 6 weeks. Subsequently, they underwent a real-life assessment in which they performed AA-THA on a high-fidelity model with real equipment in a simulated operating theatre. Teams performed together and individually-trained participants were randomly paired up with a solo player of the opposite role. Videos of the assessment were marked by two blinded expert assessors. The primary outcome was team performance as graded by the validated NOTECHs II score. Secondary outcomes were procedure time and number of technical errors from an expert pre-defined protocol.

Teams outperformed individually-trained participants for non-technical skills in the real-world assessment (NOTECHS-II score 50.3 ± 6.04 vs 43.90 ± 5.90, p=0.0275). They completed the assessment 28.1% faster (31.22 minutes ±2.02 vs 43.43 ±2.71, p=0.01), and made close to half the number of technical errors when compared to the individual group (12.9 ± 8.3 vs 25.6 ± 6.1, p=0.001).

Multiplayer, team training appears to lead to faster surgery with fewer technical errors and the development of superior non-technical skills.

Evidence supporting the use of virtual reality (VR) training in orthopaedic procedures is rapidly growing. However, the impact of the timing of delivery of this training is yet to be tested. We aimed to investigate whether spaced VR training is more effective than massed VR training.

24 medical students with no hip arthroplasty experience were randomised to learning the direct anterior approach total hip arthroplasty using the same VR simulation, training either once-weekly or once-daily for four sessions. Participants underwent a baseline physical world assessment on a saw bone pelvis. The VR program recorded procedural errors, time, assistive prompts required and hand path length across four sessions. The VR and physical world assessments were repeated at one-week, one-month, and 3 months after the last training session.

Baseline characteristics between the groups were comparable (p > 0.05). The daily group demonstrated faster skills acquisition, reducing the median ± IQR number of procedural errors from 68 ± 67.05 (session one) to 7 ± 9.75 (session four), compared to the weekly group's improvement from 63 ± 27 (session one) to 13 ± 15.75 (session four), p < 0.001. The weekly group error count plateaued remaining at 14 ± 6.75 at one-week, 16.50 ± 16.25 at one-month and 26.45 ± 22 at 3-months, p < 0.05. However, the daily group showed poorer retention with error counts rising to 16 ± 12.25 at one-week, 17.50 ± 23 at one-month and 41.45 ± 26 at 3-months, p<0.01. A similar effect was noted for the number of assistive prompts required, procedural time and hand path length. In the real-world assessment, both groups significantly improved their acetabular component positioning accuracy, and these improvements were equally maintained (p<0.01).

Daily VR training facilitates faster skills acquisition; however weekly practice has superior skills retention.

Aims

This study investigates the use of the metabolic equivalent of task (MET) score in a young hip arthroplasty population, and its ability to capture additional benefit beyond the ceiling effect of conventional patient-reported outcome measures.

Abstract

Abstract

This study investigates the use of the Metabolic Equivalent of Task (MET) score in a hip arthroplasty population and its ability to capture additional benefit beyond the maximum Oxford Hip Score (OHS).

OHS, EuroQol-5D index (EQ-5D), and the MET were prospectively recorded in 221 primary hip arthroplasty procedures pre-operatively and at 1-year. The distribution was examined reporting the presence of ceiling & floor effects. Validity was assessed correlating the MET with the other scores using Spearman's rank and determining responsiveness using the standardised response mean (SRM). A subgroup of 93 patients scoring 48/48 on the OHS were analysed by age group, sex, BMI and pre-operative MET using the other two metrics to determine if differences could be established despite all scoring identically on the OHS.

117 total hip and 104 hip resurfacing arthroplasty operations were included. Mean age was 59.4 ± 11.3. Post-operatively the OHS and EQ-5D demonstrate significant negatively skewed distributions with ceiling effects of 41% and 53%, respectively. The MET was normally distributed post-operatively with no ceiling effect. Weak-moderate but statistically significant correlations were found between the MET and the other two metrics both pre & post-operatively. Responsiveness was excellent, SRM for OHS: 2.01, EQ-5D: 1.06 and MET: 1.17. In the 48/48 scoring subgroup, no differences were found comparing groups with the EQ-5D, however significantly higher MET scores were demonstrated for patients aged <60 (12.7 vs 10.6, p=0.008), male patients (12.5 vs 10.8, p=0.024) and those with pre-operative MET scores >6 (12.6 vs 11.0, p=0.040).

The MET is normally distributed in patients following hip arthroplasty, recording levels of activity which are undetectable using the OHS. As a simple, valid activity metric, it should be considered in addition to conventional PROMs in order to capture the entire benefit experienced following hip arthroplasty.

Patients undergoing hip resurfacing arthroplasty (HRA) is typically reserved for highly active patients. Patient Reported Outcome Measures (PROMs) such as the Oxford Hip Score (OHS) are reported to have ceiling effects, which may limit physicians' ability to measure health gain in these patients. The Metabolic Equivalent of Task (MET) index is a validated compendium assigning energy expenditure to a wide range of activities; for example, a slow walk expends 2.9 kcal/kg/hour, golf expends 4.0 kcal/kg/hour, while moderate lacrosse typically expends 8.1 kcal/kg/hour. We hypothesized that for patients with high OHS (47–48) after HRA, the MET index could better discriminate between high-performing individuals.

We evaluated 97 consecutive HRA patients performed by a single surgeon. They prospectively completed an online Oxford Hip Score. They also listed three activities which they had performed independently in the preceding 2 weeks with a Likert-scale slider denoting intensity of effort. Matched data-sets were obtained from 51 patients, from which 23 had OHS of 47–48 at 6-months. Their activity with the highest MET index was selected for analysis. The 23 patients' OHS improved from 29.3 ± 7.0 preoperatively to 47.6 ± 0.5 after 6-months, while their MET indices improved from 8.5 ± 3.7 to 12.9 ± 3.5 kcal/kg/hr. The activities performed by these high-performance individuals ranged from the lowest, pilates (8.05 kcal/kg/hour), to highest, running at 22km/hr (23 kcal/kg/hour). 45% of patients undergoing HRA in this cohort had OHS of 47 and 48 at 6-months after surgery.

Unlike the OHS, the MET index described variation in physical activity in these high-performance individuals, and did so on an objective measurable scale.

Aims

Restarting planned surgery during the COVID-19 pandemic is a clinical and societal priority, but it is unknown whether it can be done safely and include high-risk or complex cases. We developed a Surgical Prioritization and Allocation Guide (SPAG). Here, we validate its effectiveness and safety in COVID-free sites.

Background

In the United Kingdom, over 1 million elective surgeries were cancelled due to COVID-19, resulting in over 1.9 million people now waiting more than 4 months for their procedure – 3x the number last year. To address this backlog, the healthcare service has been asked to develop locally-designed ‘COVID-light’ facilities. In our local system, 822 patients awaited orthopaedic surgery when elective surgery was permitted to resume. The phased return of service required a careful and pragmatic prioritisation of patients, to protect resources, patients, and healthcare workers.

Background

Revision total knee arthroplasty (rTKA) is a high stakes procedure with complex equipment and multiple steps. For rTKA using the ATTUNE system revising femoral and tibial components with sleeves and stems, there are over 240 pieces of equipment that require correct assembly at the appropriate time. Due to changing teams, work rotas, and the infrequency of rTKR, scrub nurses may encounter these operations infrequently and often rely heavily on company representatives to guide them. In turn, this delays and interrupts surgical efficiency and can result in error. This study investigates the impact of a fully immersive virtual reality (VR) curriculum on training scrub nurses in technical skills and knowledge of performing a complex rTKA, to improve efficiency and reduce error.

Aims

Arthroplasty skills need to be acquired safely during training, yet operative experience is increasingly hard to acquire by trainees. Virtual reality (VR) training using headsets and motion-tracked controllers can simulate complex open procedures in a fully immersive operating theatre. The present study aimed to determine if trainees trained using VR perform better than those using conventional preparation for performing total hip arthroplasty (THA).

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.

Aims

The hip’s capsular ligaments passively restrain extreme range of movement (ROM) by wrapping around the native femoral head/neck. We determined the effect of hip resurfacing arthroplasty (HRA), dual-mobility total hip arthroplasty (DM-THA), conventional THA, and surgical approach on ligament function.

The hip's capsular ligaments (CL) passively restrain extreme range of motion (ROM) by wrapping around the native femoral head/neck, and protect against impingement and instability. We compared how CL function was affected by device (hip resurfacing arthroplasty, HRA; dual mobility total hip arthroplasty, DM-THA; and conventional THA, C-THA), and surgical approach (anterior and posterior), with and without CL surgical-repair. We hypothesized that CL function would only be preserved when native head-size (HRA/DM-THA) was restored.

CL function was quantified on sixteen cadaveric hips, by measuring ROM by internally (IR) and externally rotating (ER) the hip in six functional positions, ranging from full extension with abduction to full flexion with adduction (squatting). Native ROM was compared to ROM after posterior capsulotomy (right hips) or anterior capsulotomy (left hips), and HRA, and C-THA and DM-THA, before and after CL repair.

Independent of approach, ROM increased most following C-THA (max 62°), then DM-THA (max 40°), then HRA (max 19°), indicating later CL engagement and reduced biomechanical function with smaller head-size. Dislocations also occurred in squatting after C-THA and DM-THA. CL-repair following HRA restored ROM to the native hip (max 8°). CL-repair following DM-THA reduced ROM hypermobility in flexed positions only and prevented dislocation (max 36°). CL-repair following C-THA did not reduce ROM or prevent dislocation.

For HRA and repair, native anatomy was preserved and ligament function was restored. For DM-THA with repair, ligament function depended on the movement of the mobile-bearing, with increased ROM in positions when ligaments could not wrap around head/neck. For C-THA, the reduced head-size resulted in inferior capsular mechanics in all positions as the ligaments remained slack, irrespective of repair.

Choosing devices with anatomic head-sizes (HRA/DM-THA) with capsular repair may have greater effect than surgical approach to protect against instability in the early postoperative period.

We aimed to demonstrate the clinical safety of a novel anatomic cementless ceramic hip resurfacing device. Concerns around the safety of metal on metal arthroplasty have made resurfacing less attractive, while long term function continues to make the concept appealing. Biolox Delta ceramic is now used in more than 50% of all hip arthroplasties, suggesting that it's safety profile is acceptable. We wondered if a combination of these concepts might work?

The preclinical testing of anatomic hip resurfacing device developed by our group was presented last year. A twenty patient safety study was designed. Patients had to be between the ages of 18 and 70. The initial size range was restricted to femoral heads between 46 and 54, representing the common sizes of hip resurfacing. The primary outcomes were clinical safety, PROMs and radiological control. Secondary outcomes include CTRSA and metal ion levels.

20 patients were recruited, aged 30–69. 7 were women and 13 were men. There were no operative adverse events in their operations undertaken between September 2017 and February 2018. One patient had a short episode of atrial fibrillation on the second postoperative day, and no other complications. At three months the median oxford hip score had risen from 27 (range 14–38) to 46 (31–48). Cobalt and chromium levels were almost undetectable at 3 months. Fixation appeared satisfactory in all patients, with no migration detected in either component. CTRSA is in process.

The initial safety of a novel cementless ceramic resurfacing device is demonstrated by this data. The 10 year, 250 case efficacy study will continue in 5 other European centres.

The hip joint capsular ligaments (CL) passively restrain extreme range of motion (ROM) by wrapping around the native femoral head, and protect against impingement, edge loading wear and dislocation. This study compared how ligament function was affected by device (hip resurfacing arthroplasty, HRA; dual mobility total hip arthroplasty, DM-THA; and conventional THA, C-THA), with and without CL repair. It was hypothesized that ligament function would only be preserved when native anatomy was preserved: with restoration of head-size (HRA or DM-THA) and repair.

Eight normal male cadaveric hips were skeletonised, retaining the hip capsule. CL function was quantified by measuring ROM by internally (IR) and externally rotating (ER) the hip in six functional positions, ranging from full extension with abduction to full flexion with adduction (squatting). Native ROM was compared to ROM after posterior capsulotomy and HRA, and C-THA and DM-THA, before and after surgical CL repair.

ROM increased most following C-THA (max 62°), then DM-THA (max 40°), then HRA (max 19°), indicating later engagement of the capsule and reduced biomechanical function with smaller head-size. Dislocations also occurred in squatting after C-THA and DM-THA. CL-repair following HRA restored ROM to the native hip (max 8°). CL-repair following DM-THA reduced ROM hypermobility in flexed positions only and prevented dislocation (max 36°). CL-repair following C-THA did not reduce ROM or prevent dislocation.

When HRA was combined with repair, native anatomy was preserved and ligament function was restored. For DM-THA with repair, ligament function depended on the movement of the mobile bearing resulting in near-native function in some positions, but increased ROM when ligaments were unable to wrap around the head/neck. Following C-THA, the reduced head-size resulted in inferior capsular mechanics in all positions as the ligaments remained slack, irrespective of repair.

Choosing devices with anatomic head-sizes (resurfacing or dual-mobility) and repairing the capsular ligaments may protect against instability in the early postoperative period.

Background

Accurate implant orientation is associated with improved outcomes after artificial joint replacement. We investigated if a novel augmented-reality (AR) platform (with live feedback) could train novice surgeons to orientate an acetabular implant as effectively as conventional training (CT).

Background

Complications such as dislocations, impingement and early wear following total hip arthroplasty (THA) increase with acetabular cup implant malorientation. These errors are more common with low-volume centres or in novice hands. Currently, this skill is most commonly taught during real surgery with an expert trainer, but simulated training may offer a safer and more accessible solution. This study investigated if a novel MicronTracker® enhanced Microsoft HoloLens® augmented reality (EAR) headset was as effective as one-on-one expert surgeon (ES) training for teaching novice surgeons hip cup orientation skill.

Background

Trust in the validity of a measurement tool is critical to its function in both clinical and educational settings. Acetabular cup malposition within total hip arthroplasty (THA) can lead to increased dislocation rates, impingement and increased wear as a result of edge loading. We have developed a THA simulator incorporating a foam/Sawbone pelvis model with a modified Microsoft HoloLens® augmented reality (AR) headset. We aimed to measure the trueness, precision, reliability and reproducibility of this platform for translating spatial measurements of acetabular cup orientation to angular values before developing it as a training tool.

Introduction

Current work-hour restrictions and cost pressures have highlighted the limitations of apprenticeship-based learning, and led to the development of alternative methods to improve the skills of orthopaedic trainees outside of the clinical environment. These methods include using synthetic bones and simulators in the laboratory setting. Educational theory highlights the importance of context for effective learning, yet full-immersion simulation facilities are prohibitively expensive. This study explored the concept of contextualised training day in trauma & orthopaedics.

Cam femoroacetabular impingement (FAI) is currently treated by resecting the femoral cam lesion. Some surgeons advocate additional anterosuperior acetabular rim resection. However, the exact acetabular contribution to cam-FAI has yet to be described. Using 3D-CT analysis, we set out to quantify the acetabular rim shape and orientation in this condition, and to determine the roles of these factors in cam-FAI.

The acetabula of twenty consecutive cam hips (defined by α-angle of Notzli greater than 55° on plain radiographs) undergoing image based navigated surgery. These were compared with twenty normal hips (defined as disease free sockets with a normal femoral head-neck junction) obtained from a CT colonoscopy database.

Using 3D reconstruction software, the pelvis was aligned to the anterior pelvic plane (APP). Starting at the most anterior rim point, successive markers were placed along the rim. A best-fit acetabular rim plane (ARP) was derived, and the subtended angle (SA) between each rim marker and a normal vector from the acetabular centre was calculated. Values above 90° indicated a peak, with less than 90° representing a trough. Inclination and version were measured from the APP.

Our results showed that the rim profile of both cam-type and normal acetabular is an asymmetric succession of three peaks and three troughs. However, the cam-type acetabulum is significantly shallower overall than normal (Mean SA: 84±5° versus 87±4°, p< 0.0001). In particular, at anatomical points in the impingement zone between 12 and 3 o’clock, the subtended angle of cam hips were never higher than normal, and, in fact, at certain points were lower (iliac eminence: 90±5° vs. 93±4° p=0.0094, iliopubic trough: 79±5° vs. 83±4° p=0.0169, pubic eminence 83±7° vs. 84±4° p=0.4445). The orientation of cam and normal hips were almost identical (Inclination: 53±4°vs. 51±3° p=0.2609 and Anteversion: 23±7° vs. 24±6° p=0.3917).

We concluded that cam-type acetabula are significantly shallower than normal. The subtended angles at all points around the hip were lower, and in particular, in the impingement zone between 12 and 3 o’clock not one cam had a subtended angle over 90°. We have therefore been unable to support the hypothesis of mixed-type FAI in cam-type hips.

Bony rim resection in cam hips therefore runs the risk of rendering the acetabulum more morphologically abnormal and even functionally dysplastic. We do not recommend acetabular rim resection in patients with pure cam-type impingement, and await the longer-term results of this practice with apprehension.

Pincer femoroacetabular impingement (FAI) is cited as being the result of a socket that is either too deep or retroverted, or both. Using 3D-CT analysis, we set out to quantify the acetabular rim shape and orientation to determine the roles of these two factors in FAI.

Twenty pincer acetabulae were selected from patients undergoing image based navigated surgery, where the lateral centre edge angle was greater than 40° on plain radiographs. The normal group of disease free sockets were obtained from a CT colonography database.

Using 3D reconstruction of their CT scans, a novel method of mapping the acetabular rim profile was created. The pelvis was aligned to the anterior pelvic plane. Starting at the most anterior rim point, successive markers were placed along the rim. A best fit plane (ARP) through the acetabulum was derived, and the subtended angle (SA) between each rim marker and a normal vector from the acetabular centre was calculated. Values above 90° indicated a peak, with less than 90° representing a trough. Inclination and version were measured from a horizontal plane and the ARP, in the coronal and axial view respectively.

The results showed that asymmetric acetabular rim profiles in normal and pincer hips were very similar. However, pincer hips are significantly deeper overall (Mean SA 96±5° vs. 87±4° p< 0.00001) and at each anatomical point of the three eminences (pubic [SA: Normal 84±4° vs. Pincer 94±7° p< 0.00001], iliac [SA: 93±4° vs. 100±6° p=0.00021] and ischial [SA: 92±3° vs. 102±8° p=0.00005]) and two troughs (ilio-pubic [SA: Normal 83±4° vs. Pincer 94±8° p=0.00001] and ilio-ischial [SA: 92±3° vs. 102±8° p=0.00002]).

The orientation of normal and pincer were almost identical (Inclination: 51±3° vs. 51±6° p=0.54 and Version: 24±6° vs. 25°±7° p=0.67).

We conclude that the rim shape of pincer hips follows the same contour as normal hips. In agreement with current radiographic diagnosis, pincer-type hips are characterised by a deeper acetabulum. This ‘overcoverage’ of the femoral head confirms the biomechanical model of pincer-type impingement.

Both inclination and version in these two groups were almost identical, with no truly retroverted acetabulum seen. Pincer impingement resulting from ‘acetabular retroversion’ is a concept currently based upon radiographic signs that we have been unable to confirm in this small 3D study using the subtended angle as the key descriptor of acetabular morphology.