Total Hip Arthroplasty (THA) and Hip Hemiarthroplasties (HA) are successful, cost-effective procedures that improve quality of life. Dislocation is a well recognised complication with a significant health and economic burden. We aim to establish the current management practices across the United Kingdom (UK) for Prosthetic Hip Dislocations (PHD). Our definition of a PHD includes; THA, HA and revision THA.

This national study builds on our regional pilot study and records one of the largest datasets of Prosthetic Hip Dislocation management within the UK.

A trainee-led collaborative; the North West Orthopaedic Research Collaborative (NWORC). Conducted a retrospective audit, registered as Quality Improvement (QI) projects, collected data from 38 hospital trusts across the UK.

Data was collected on patient-related factors, inpatient management, and outpatient follow up of each PHD episode between January and July 2019. Primary outcome measured definitive management, in the form of revision surgery or the consideration for this through a referral pathway.

A total of 673 (THA 504, Revision THA 141, HA 28) patients were included with a total of 740 dislocation episodes. Mean age was 75.6 years with female to male ratio 2:1. The majority of PHDs were a result of a low energy mechanism (98.7%) and presented over 6 months post index procedure (80.5%). Over half (53.8%) attended with a first or second time dislocation. Only 29.9% patients received onward revision referral; whereas 70.1% followed diverse management patterns, including local non-arthroplasty and primary arthroplasty surgeon follow-ups. Revision THAs had higher rates of referral for revision (p<0.001) compared to primary THA and HA dislocations.

A high number of PHDs present across the UK, with under a third receiving definitive management plans. This variation increases the economical burden to the National Health Service, highlighting the need for national guidance to manage these complex patients.

The purpose of this modified Delphi study was to obtain consensus on wound closure (including best practices for each tissue layer of closure) and dressing management in total hip arthroplasty (THA), using an evidence-based approach.

The Delphi panel included 20 orthopedic surgeons from Europe and North America. Eighteen statements were identified (14 specific to THA and 4 relating to both THA and total knee arthroplasty) using a targeted literature review. Consensus was developed on the statements with up to three rounds of anonymous voting per topic. Panelists ranked their agreement with each statement on a five-point Likert scale. An a priori threshold of 75% was required for consensus.

In Round 1, 15 of 18 statements achieved consensus via a structured electronic questionnaire. In Round 2, the 3 statements that did not achieve consensus were revised during a virtual face to face meeting. An additional 2 statements were edited for clarity. In Round 3, the 5 revised statements achieved consensus via a structured electronic questionnaire. Wound closure related interventions that were recommended for use in THA included: 1) barbed sutures over non-barbed sutures (shorter closing times and overall cost savings); 2) subcuticular sutures over skin staples (lower risk of infections and higher patient preference); 3) mesh-adhesives over silver-impregnated dressings (lower rate of wound complications); 4) negative pressure wound therapy over other dressings (lower wound complications and reoperations and fewer dressing changes); 5) triclosan coated sutures (lower risk of surgical site infection).

Using a modified Delphi approach, a panel of 20 orthopedic surgeons achieved consensus on 18 statements pertaining to multi-layer wound closure and dressing management in THA. This study forms the basis for identifying critical evidence gaps within wound management to help reduce variability in outcomes during THA.

Dual Mobility (DM) Total Hip Replacements (THRs), are becoming widely used but function in-vivo is not fully understood.

The aim of this study was to compare the incidence of impingement of a modular dual mobility with that of a standard cup.

A geometrical model of one subject's bony anatomy \[1\] was developed, a THR was implanted with the cup at a range of inclination and anteversion positions (Corail® stem, Pinnacle® cup (DePuy Synthes)). Two DM variants and one STD acetabular cup were modelled. Joint motions were taken from kinematic data of activities of daily living associated with dislocation \[2\] and walking. The occurrence of impingement was assessed for each component combination, orientation and activity. Implant-implant impingement can occur between the femoral neck and the metal or PE liner (DM or STD constructs respectively) or neck-PE mobile liner (DM only).

The results comprise a colour coded matrix which sums the number of impingement events for each cup position and activity and for each implant variant.

Neck-PE mobile liner impingement, occurred for both DM sizes, for all activities, and most cup placement positions indicating that the PE mobile liner is likely to move at the start of all activities including walking.

For all constructs no placement positions avoided neck-metal (DM) or neck-PE liner (STD) impingementevents in all activities. The least number of events occurred at higher inclination and anteversion component positions. In addition to implant-implant impingement, some instances of bone-bone and implant-bone impingement were also observed.

Consistent with DM philosophy, neck-PE mobile liner impingement and liner motion occurred for all activities including walking. Neck-liner impingement frequency was comparable between both DM sizes (metal liner) and a standard cup (PE liner).

This study evaluates the association between consultant and hospital volume and the risk of re-revision and 90-day mortality following first-time revision of primary hip replacement for aseptic loosening.

We conducted a cohort study of first-time, single-stage revision hip replacements (RHR) performed for aseptic loosening and recorded in the National Joint Registry (NJR) data for England, Wales, Northern Ireland, and the Isle of Man between 2003 and 2019. Patient identifiers were used to link records to national mortality data, and to NJR data to identify subsequent re-revision procedures. Multivariable Cox proportional hazard models with restricted cubic splines were used to define associations between volume and outcome.

Among 12,676 RHR there were 513 re-revisions within two years, and 95 deaths within 90 days of surgery. The risk of re-revision was highest for a consultant's first RHR (Hazard Ratio (HR) 1·58 (95%CI 1·16 to 2·15)) and remained significantly elevated for their first 26 cases (HR 1·26 (95%CI 1·00 to 1·58)). Annual consultant volumes of five/year were associated with an almost 30% greater risk of re-revision (HR 1·28 (95%CI 1·00 to 1·64)) and 80% greater risk of 90-day mortality (HR 1·81 (95%CI 1·02 to 3·21)) compared to volumes of 20/year. RHR performed at hospitals which had cumulatively undertaken fewer than 168 RHR were at up to 70% greater risk of re-revision (HR 1·70 (95% CI 1·12 to 2·60)), and those having undertaken fewer than 309 RHR were at up to three times greater risk of 90-day mortality (HR 3·06 (95% CI 1·19 to 7·86)).

This study found a significantly higher risk of re-revision and early postoperative mortality following first-time single-stage RHR for aseptic loosening when performed by lower-volume consultants and at lower-volume institutions, supporting the move towards the centralisation of such cases towards higher-volume units and surgeons.

Abstract

Aims

This study describes the variation in the annual volumes of revision hip arthroplasty (RHA) undertaken by consultant surgeons nationally, and the rate of accrual of RHA and corresponding primary hip arthroplasty (PHA) volume for new consultants entering practice.

Dual Mobility (DM) Total Hip Replacements (THRs) were introduced to reduce dislocation risk, which is the most common cause of early revision. The in-vivo mechanics of these implants is not well understood, despite their increased use in both elective and trauma settings. Therefore, the aim of this study was to comprehensively assess retrieved DM polyethylene liners for signs of damage using visual inspection and semi-quantitative geometric assessment techniques.

Retrieved DM liners (n=20) were visually inspected for the presence of seven established modes of polyethylene damage. If embedded debris was identified on the external surface, its material composition was characterised using energy-dispersive x-ray analysis (EDX). Additionally, each liner was geometrically assessed for signs of wear/deformation using a validated methodology.

Visual inspection of the liners revealed that scratching and pitting were the most common damage modes on either surface. Burnishing was observed on 50% and 15% of the internal and external surfaces, respectively. In addition, embedded debris was identified on 25% of the internal and 65% of the external surfaces. EDX analysis of the debris identified several materials including iron, titanium, cobalt-chrome, and tantalum. Geometric analysis demonstrated highly variable damage patterns across the liners.

The results of this study provide insight into the in-vivo mechanics of DM bearings. For example, the results suggest that the internal bearing (i.e., between the head and liner) acts as the primary articulation site for DM-THRs as evidenced by a higher incidence of burnishing and larger, more concentrated regions of penetration across the liners’ internal surfaces. Furthermore, circumferential, and crescent-shaped damage patterns were identified on the articulating surfaces of the liners thus providing evidence that these components can rotate within the acetabular shell with varying degrees of mobility. The mechanics of DM bearings are complex and may be influenced by several factors (e.g., soft tissue fibrosis, patient activities) and thus further investigation is warranted.

Finally, the results of this study suggest that DM liners may be susceptible to ex-vivo surface damage and thus caution is advised when handling and/or assessing these types of components.

It is unclear whether patients with early radiographic osteoarthritis (OA) but severe hip symptoms benefit from total hip replacement (THR). We aimed to assess which factors were associated with successful THR in this patient group.

From a consecutive series of 1,935 patients undergoing THR we identified 70 (3.6%) patients with early OA (Kellgren and Lawrence (KL) grades 0-2). These were compared with 200 patients with advanced OA (KL grades 3–4). Outcomes were Oxford Hip Scores (OHS), EQ5D and EQ-VAS scores; compared pre-operatively with one year post-operatively. We investigated which clinical and radiographic (plain x-ray, CT, MRI) features predicted successful THR in the early OA group. Success was defined as reaching a postoperative OHS≥42.

The early OA group were significantly younger (61 vs 66 years; P=0.0035). There were no significant differences in body mass index, ASA grade or gender. After adjusting for confounders, the advanced OA group had a significantly greater percentage of possible change (PoPC) in OHS (75.8% versus 50.4%; P<0.0001) and improvement in EQ5D (0.151 versus 0.002; P<0.0001). There were no significant differences in complication, revision or readmission rates. In the early OA group, we identified 16/70 (22.9%) patients who had a ‘successful’ THR. Of those with early OA, 38 patients had pre-operative CT or MRI scans. Patients who had a ‘successful’ THR were significantly more likely to have subchondral cysts on CT/MRI (91.7% versus 57.7%; P=0.0362). The presence of cysts on CT/MRI was associated with a significantly greater PoPC in OHS (61.6% versus 38.2%; P=0.0353). The combination of cysts and joint space width (JSW) <1mm was associated with a PoPC of 68%. Plain radiographs were found to significantly underestimate the narrowest JSW compared to CT/MRI (2.4mm versus 1.0mm; P<0.0001).

We advise caution in performing THRs in patients with early OA (KL grades 0-2) on plain radiographs. We advocate pre-operative cross-sectional imaging (CT or MRI) in these patients. In the absence of cysts on cross-sectional imaging, a THR seems unlikely to provide a satisfactory outcome.

Mortality following revision hip surgery for periprosthetic fracture (PPF) has been reported to be as high as 60% at 5 years. The aim of this study was to determine the mortality rate for PPF revisions, compared to revision for aseptic loosening or infection at our tertiary referral centre.

Revision arthroplasty procedures performed for PPF, aseptic loosening or infection between January 2014 and December 2015 at our institution were identified using a prospectively collected PPF referral database and locally collected NJR data. Comparisons were made between the 3 groups for baseline demographics, admission to higher-level care, length of stay, complications, and Kaplan-Meier failure (mortality) at 1 & 5 years post-operative (with log-rank test for equality).

There were 37 PPF, 71 infected and 221 aseptic revisions. PPF had a higher proportion of females (65% vs. 39% in infection and 53% in aseptic; p = 0.031) and grade 3 and 4 ASA patients (p = 0.006). Median time to surgery from injury for PPF was 8 days (95% CI, 6–16). Single-stage procedures were performed in 84% of PPF, 42% of infection and 99% of aseptic revisions (p < 0.001). 19% of PPF revisions required HDU admission, 1% in the aseptic group and none in the infection group (p<0.001). Median length of stay was significantly different (PPF 10; infection 14; aseptic 8 days (p < 0.001). The Kaplan-Meier estimate of 1-year mortality were: PPF = 0%; infection = 2.8% (0.7–11.1%); aseptic = 0.9% (0.2–3.5%). 5-year mortality estimates were: PPF = 17.1% (8–34%), infection = 8.7% (4–18.3%), aseptic = 12% (8.4–17%). Log-rank test of equality was not significant, p=0.833.

Despite the PPF group having an average delay to surgery of 8 days, higher ASA grades and more admissions to HDU there was no significant difference in mortality rates between the groups at 1 and 5 years postoperatively. Using a coherent MDT approach with dedicated healthcare professionals this service demonstrates a low post operative mortality rate which merits further investment and development.

Studies have shown that 10–30% patients do not achieve optimal function outcomes after total hip replacement (THR). High quality randomised controlled trials (RCTs) evaluating the clinical and cost-effectiveness of techniques to improve functional outcomes after THR are lacking. We performed this study to evaluate the feasibility of a RCT comparing patient-reported functional outcomes after hybrid or fully cemented THR (ISRCTN11097021).

Patients were recruited from two centres and randomised to receive either a fully cemented or hybrid THR. Data collection included Patient Reported Outcome Measures (PROMs), non-serious adverse events of special interest (AESI), serious adverse device effects (SADE) and NHS resource use. Qualitative interviews were undertaken to understand a) patient experiences of study processes and their reasons for taking part or not, and b) to understand surgeons’ perceptions of the study, factors affecting willingness to participate, and barriers to implementation of the future RCT findings.

The target of 40 patients were successfully recruited for the feasibility RCT; the ratio of successful recruitment to eligible patients was 0.61 across both sites. Treatment crossovers occurred in four patients, all related to bone quality. Four patients were withdrawn due to not undergoing surgery within the study window because of the pandemic. Follow-up was 100% and PROMs were completed by all patients at all time points. The feasibility of conducting a within-trial cost-utility analysis was demonstrated. Interviews were conducted with 27 patients and 16 surgeons. Patients and surgeons generally found the study procedures acceptable and workable. Some declined participation because they did not want treatment allocated at random, or because blinding was off-putting. Surgeons’ perceptions of equipoise varied, and implementation of findings from the future RCT would need to recognise the ‘craft’ nature of surgery and the issue of training.

We conclude that a full RCT with economic analysis will be both feasible and practicable, although mechanisms to safely implement potential changes to practice because of RCT findings may need consideration by the wider arthroplasty community.

Musculoskeletal disorders have been recognised as common occupational risks for all orthopaedic surgeons. The nature of tasks performed by hip surgeons often requires both forceful and repetitive manoeuvres, potentially putting them at higher risk of musculoskeletal injuries compared to other orthopaedic sub-specialities. This study aimed to investigate the prevalence of musculoskeletal conditions among hip surgeons and evaluate the association between their workplace and lifestyle factors and musculoskeletal health.

An online questionnaire consisting of 22 questions was distributed to UK-based consultant hip surgeons via email and social media platforms. This survey was completed by 105 hip surgeons.

The mean age of the respondents was 49 years (range 35–69), with an average of 12 years (range 1–33) in service. 94% were full-time and 6% worked part-time. 49% worked at a district general hospital, 49% at a tertiary centre and 4% at a private institution. 80% were on the on-call rota and 69% had additional trauma commitments. 91% reported having one or more, 50% with three or more and 13% with five or more musculoskeletal conditions. 64% attributed their musculoskeletal condition to their profession. The most common musculoskeletal conditions were base of thumb arthritis (22%), subacromial impingement (20%), degenerative lumbar spine (18%) and medial or lateral epicondylitis (18%). 60% stated that they experienced lower back pain. Statistical analysis showed that being on the on-call rota was significantly (P<0.001) associated with a higher musculoskeletal burden. Regular resistance and/or endurance training and BMI<30 were statistically significant protective factors (P<0.001).

Over the last few decades, most of the hip-related literature has focused on improving outcomes in patients, yet very little is known about the impact of hip surgery on the musculoskeletal health of hip surgeons. This study highlights a high prevalence of musculoskeletal conditions among UK-based hip surgeons. Hip surgeons have a pivotal role to play in the ongoing recovery of elective orthopaedics services. There is a pressing need for the identification of preventative measures and improvement in the surgical environment of our hip surgeons.

Cite this article: Bone Joint Res 2023;12(5):309–310.

Cite this article: Bone Joint Res 2023;12(5):306–308.

Hip joint biomechanics can be altered by abnormal morphology of the acetabulum and/or femur. This may affect load distribution and contact stresses on the articular surfaces, hence, leading to damage and degradation of the tissue. Experimental hip joint simulators have been used to assess tribology of total hip replacements and recently methods further developed to assess the natural hip joint mechanics. The aim of this study was to evaluate articular surfaces of human cadaveric joints following prolonged experimental simulation under a standard gait cycle.

Four cadaveric male right hips (mean age = 62 years) were dissected, the joint disarticulated and capsule removed. The acetabulum and femoral head were mounted in an anatomical hip simulator (Simulation Solutions, UK). A simplified twin peak gait cycle (peak load of 3kN) was applied. Hips were submerged in Ringers solution (0.04% sodium azide) and testing conducted at 1 Hertz for 32 hours (115,200 cycles). Soft tissue degradation was recorded using photogrammetry at intervals throughout testing.

All four hips were successfully tested. Prior to simulation, two samples exhibited articular surface degradation and one had a minor scalpel cut and a small area of cartilage delamination. The pre-simulation damage got slightly worse as the simulation continued but no new areas of damage were detected upon inspection. The samples without surface degradation, showed no damage during testing and the labral sealing effect was more obvious in these samples.

The fact that no new areas of damage were detected after long simulations, indicates that the loading conditions and positioning of the sample were appropriate, so the simulation can be used as a control to compare mechanical degradation of the natural hip when provoked abnormal conditions or labral tissue repairs are simulated.

Dual mobility (DM) total hip replacements (THRs) were introduced to reduce dislocation risk, which is the most common cause of early revision. Although DM THRs have shown good overall survivorship and low dislocation rates, the mechanisms which describe how these bearings function in-vivo are not fully understood. Therefore, the study aim was to comprehensively assess retrieved DM polyethylene liners for signs of damage using visual inspection and semi-quantitative geometric assessment methods.

Retrieved DM liners (n=18) were visually inspected for the presence of surface damage, whereby the internal and external surfaces were independently assigned a score of one (present) or zero (not present) for seven damage modes. The severity of damage was not assessed. The material composition of embedded debris was characterised using energy-dispersive x-ray analysis (EDX). Additionally, each liner was geometrically assessed for signs of wear/deformation [1].

Scratching and pitting were the most common damage modes on either surface. Additionally, burnishing was observed on 50% of the internal surfaces and embedded debris was identified on 67% of the external surfaces. EDX analysis of the debris identified several materials including titanium, cobalt-chrome, iron, and tantalum. Geometric analysis demonstrated highly variable damage patterns across the liners.

The incidence of burnishing was three times greater for the internal surfaces, suggesting that this acts as the primary articulation site. The external surfaces sustained more observable damage as evidenced by a higher incidence of embedded debris, abrasion, delamination, and deformation. In conjunction with the highly variable damage patterns observed, these results suggest that DM kinematics are complex and may be influenced by several factors (e.g., soft tissue fibrosis, patient activities) and thus further investigation is warranted.

The 10 year survivorship of THR is generally over 95%. However, the incidence of revision is usually higher in year one. The most common reason being dislocation which at least in part is driven by inadequate range of motion (ROM) leading to impingement, subluxation and ultimately dislocation which is more frequently posterior. ROM is affected by patient activity, bone and component geometry, and component placement. To reduce the incidence of dislocation, supported by registry data, there has been an increase in the use of so-called ‘lipped’ liners. Whilst this increases joint stability, the theoretical ROM is reduced. The aim of this study was to investigate the effect of lip placement on impingement.

A rigid body geometric model was incorporated into a CT scan hemi-pelvis and femur, with a clinically available THR virtually implanted. Kinematic activity data associated with dislocation was applied, comprising of five posterior and two anterior dislocation risk activities, resulting from anterior and posterior impingement respectively. Cup inclination and anteversion was varied (30°-70°, 0°-50° respectively) to simulate extremes of clinical outcomes. The apex position of a ‘lipped’ liner was rotated from the superior position, anteriorly and posteriorly in steps of 45°. Incidence and location of implant and bone impingement was recorded in 5346 cases generated.

A liner with the lip placed superior increased the occurrence of implant-implant impingement compared with a neutral liner. Rotation of the lip from superior reduced this incidence. This effect was more marked with posterior rotation which after 90° reduced anterior impingement to levels similar to a neutral liner. Complete inversion of the lipped liner reduced impingement, but this and anterior rotation both negate its function – additional stability.

This study comprises one bone geometry and component design and one set of activity profiles. Nevertheless, it indicates that appropriate lip placement can minimise the likelihood of impingement for a range of daily activities whilst still providing additional joint stability.

We determined the impact of deprivation and frailty at the time of diagnosis of hip osteoarthritis (OA) on the likelihood of receiving total hip arthroplasty (THA).

We used routinely collected primary care data (Clinical Practice Research Datalink) linked to Hospital Episode Statistics. Frailty was assessed at the time of hip OA diagnosis using a validated frailty index based on coded data in the primary care record and categorised as fit, mild, moderate, and severe frailty. The association between quintile of index of multiple deprivation (IMD), frailty category and likelihood of receiving THA was assessed in separate Cox regression models, adjusted for year of OA diagnosis, age, and sex.

104,672 individuals with hip OA contributed. Compared to those in the first quintile of IMD (least deprived), those in the fourth and fifth quintile of IMD (most deprived), respectively, were less likely to receive THA, hazard ratio (HR) (95% CI), 0.92 (0.89, 0.95) and 0.80 (0.77, 0.83).

Increasing frailty at OA diagnosis was associated with reduced likelihood of receiving THA. Compared to fit individuals, the HR (95% CI) for receiving THA among those with: mild frailty was 0.80 (0.78, 0.82); moderate frailty was 0.60 (0.58, 0.62); and severe frailty was 0.42 (0.39, 0.45).

Increasing deprivation was associated with increasing frailty at the time of hip OA diagnosis, independent of age, sex, and year of OA diagnosis. However, those in the two most deprived quintiles were still less likely to receive THA after additionally adjusting for frailty category.

Greater deprivation and greater frailty were associated with lower likelihood of receiving THA among people with hip osteoarthritis. Greater frailty among those most deprived did not explain the reduced likelihood of receiving THA among those most deprived.

We determined the association between frailty and 30-day mortality following total hip arthroplasty (THA) and the impact of THA on 30-day mortality compared to a control population.

We used primary care data (Clinical Practice Research Datalink), linked secondary care data (Hospital Episode Statistics) and Office for National Statistics mortality data. Frailty was assessed using a validated frailty index based on coded data in the primary care record and categorised as fit, mild, moderate, and severe frailty. The association between frailty and 30-day mortality following THA due to osteoarthritis was assessed using Cox regression, adjusted for year of birth, sex, quintile of index of multiple deprivation and year of surgery. Mortality following THA was also compared to a control population who had osteoarthritis but no previous THA, matched on year of birth, sex, and quintile of index of multiple deprivation.

103,563 cases who had a THA and their matched controls contributed data. Among those who had THA, compared to fit participants, 30-day mortality increased with increasing frailty; adjusted hazard ratio (HR) (95% CI) among mild frailty, 0.87 (0.66, 1.15); moderate frailty 1.73 (1.26, 2.38); and severe frailty, 2.85 (1.84, 4.39).

Compared to fit controls who did not have surgery, 30-day mortality was higher among fit people who had THA, adjusted HR 1.60 (1.15, 2.21). There was, however, no statistically significant difference in 30-day mortality among cases with mild, moderate and severe frailty compared to controls in the same frailty category.

Among people who had THA, 30-day mortality increased with increasing frailty. While 30-day mortality was increased among fit individuals who had THA compared to fit controls who did not have surgery, there did not appear to be increased mortality among individuals with mild, moderate or severe frailty compared to controls in the same frailty category. A healthy surgery (selection) effect may have impacted on the comparison of mortality among cases and controls.

Total Hip Replacements (THR) and Hip Hemiarthroplasties (HA) are both successful and common orthopaedic procedures. Dislocation is a well-recognised complication carrying significant morbidity and, in some cases, increased mortality risks. We define prosthetic hip dislocations (PHDs) to include both THRs and HAs. Prosthetic Hip Dislocations (PHDs) are a common acute admission yet there are no published guidelines or consensus on management following reduction.

A retrospective audit was undertaken by the North West Orthopaedic Research Collaborative (NWORC) between January 2019 and July 2019. A questionnaire was used to capture the management of each dislocation episode presenting to 11 Hospital trusts. The study was registered as a Quality Improvement (QI) project at each site. Data regarding the surgical management physiotherapy input, ongoing care and further management plans were recorded.

A total of 183 patients with 229 dislocations were submitted for initial analysis (171 THRs, 10 HAs, 2 PFRs). Female to male ratio was 2:1 with mean age of 76.7 years. Average time to first dislocation was 8.1 years. 61.1% were first or second time dislocators and 38.9% presented with 3 or more dislocations. Initial reductions were predominantly attempted in theatre (96.5%, n=221) with only 3.5% (n=8) attempted in the emergency department. In theatre 89% (n=201) were reduced closed. There was no plan for revision surgery in 70.6% cases with no difference seen between patients with >=3 dislocations and <=2 dislocations. Of the patients with a revision plan, 71% of these were performed or planned locally.

The high number of patients with 3 or more dislocations and the lack of plans for definitive interventions in the majority of cases highlights the significant variation in the management of this complex group of patients. This variation in the quality of care increases the burden on the National Health Service through repeat hospital episodes. We aim to roll out this study nationally to assess regional variations and ultimately make the case for national guidance on the management of prosthetic hip dislocations.

The decision to undertake total hip replacement (THA) in a child is complex and daunting. This is augmented by the paucity of data on potential quality of life (QoL) improvement and functional outcomes. Therefore, the aim of this study was to ascertain whether outcomes after surgery are influenced by the nature of the primary diagnosis.

This was a prospective, consecutive cohort study of patients under the age of 18 years undergoing THA by a single arthroplasty surgeon in collaboration with colleagues at a regional paediatric hospital. Patient electronic notes, radiographs and PROMS (EQ5D-Y, Oxford Hip Score (OHS) and modified Harris Hip Score(mHHS)) were reviewed.

Twenty-two THAs were performed in patients less than 18 years (median 15 (range 10.7–17.9), with 7 patients undergoing bilateral surgery. Mean follow-up was 2 years. Thirteen of the THAs were undertaken for systemic conditions effecting multiple joints (Mucopolysaccharidoses, Mucolipidosis and Scwachman-Diamond syndrome) with the hip the worst affected joint and 9 for single joint disease (AVN, Perthes, dysplasia and idiopathic chondrolysis). PROMS scores showed reliable improvements with no differences between the two groups. Health related QoL was calculated from EQ5D-Y and indicated an overall improvement of 1.06(0.879–1.25). 6 patients were wheelchair users preop. All patients were independent walkers at follow-up. One patient underwent successful revision surgery for aseptic acetabular loosening. There were no other complications.

THA in children leads to a significant positive impact on QoL as measured with validated PROMS scores. Patients with systemic conditions can benefit just as much as those with single joint disease. Further follow-up is required to understand the long-term outcomes.

Aims

Hip arthroplasty aims to accurately recreate joint biomechanics. Considerable attention has been paid to vertical and horizontal offset, but femoral head centre in the anteroposterior (AP) plane has received little attention. This study investigates the accuracy of restoration of joint centre of rotation in the AP plane.

Abstract

Abstract

To estimate the clinical and economic burden of primary total hip arthroplasty (THA) dislocation in England.

Retrospective propensity score-matched evaluation of patients with and without dislocation following primary THA using the UK Clinical Practice Research Datalink linked and Hospital Episode Statistics datasets with a 2-year follow-up.

13,044 patients with total hip replacements met the inclusion criteria (mean age 69.2, 60.9% female) of which 154 (1.18%) suffered at least one postoperative hip dislocation. The mean number of dislocations per patient was 1.44 with a maximum of 4. Approximately one-third of the patients with dislocation (32.5%) had more than one dislocation. Among patients with a hip dislocation 148 patients (96.7%) had at least one closed reduction and 20 patients (13.1%) had revision surgery. Two-year median direct medical costs were £14,748 (95% confidence interval [CI] £12,028 to £20,638) higher with vs. without dislocation (+227%). On average, patients with a dislocation had significantly greater healthcare resource utilization and significantly less improvement in EuroQol-5D (EQ-5D) index (0.24 vs. 0.45; p<0.001) and Visual Analogue Scale (VAS) (1.58 vs. 11.23; p=0.010) scores and Oxford Hip Scores (13.02 vs. 21.98; p<0.001).

This is the first study to estimate the economic burden of dislocation in the UK throughout the entire patient pathway. Dislocation following total hip replacement is a costly complication, both in terms of economic costs and to the functional quality of life of the patient. Efforts to reduce the risks of dislocation should remain at the forefront of hip research.

The influence of the surgical process on implant loosening and periprosthetic fractures (PPF) as major complications in uncemented total hip arthroplasty (THA) have rarely been studied due to the difficult quantification. Meanwhile registry analyses have clearly shown a decrease in complications with increasing experience. The goal of this study was to determine the extent of variability in THA stem implantation between highly experienced surgeons with respect to implant-size, -position, press-fit, contact area, primary stability and the effect of using a powered impaction tool.

Primary hip stems were implanted in 16 cadaveric femur pairs by three experienced surgeons using manual and powered impaction. Quantitative CTs were taken before and after each process step and stem tilt, canal-fill-ratio, pressfit and contact area between bone and implant determined. 11 femur pairs were additionally tested for primary stability under cyclic loading conditions.

Higher variations in press-fit and contact area between the surgeons for manual impactions compared to powered were observed. Stem tilt and implant sizing varied between surgeons but not between impaction methods. Larger stems exhibited less micromotion compared to smaller stems.

Larger implants may increase PPF risk, while smaller implants reduce primary stability. The reduced variation for powered impactions indicates that appropriate measures may promote a more standardized process. The observed variations between the experienced surgeons may represent the acceptable range for this specific stem design. Variability in the implantation process warrants further investigations since certain deviations e.g. a stem tilt towards varus, might increase bone stresses and PPF risk.

The protective effect of lipped polyethylene uncemented acetabular liners against revision THA for instability has been reported. However, the effect of lip size has not been explored, nor has the effect on revision THA for loosening. We aimed to determine if uncemented acetabular liner geometry, and lip size, influences the risk of revision THA for instability or loosening.

202511 primary THAs with uncemented polyethylene acetabular components were identified from the NJR dataset (2003 – 2017). The effect of acetabular liner geometry and lip size on the risk of revision THA for instability or loosening was investigated using binomial regression and competing risks survival analyses (competing risks were revision for other causes or death) adjusting for age, gender, ASA grade, diagnosis, side, institution type, surgeon grade, surgical approach, head size and polyethylene crosslinking.

The distribution of acetabular liners was: neutral – 39.4%, offset neutral – 0.9%, 10-degree – 34.5%, 15-degree – 21.6%, 20-degree – 0.8%, offset reorientating – 2.82%. There were 690 (0.34%) revision THAs for instability and 604 (0.3%) for loosening. Significant subhazard risk ratios were found in revision THA for instability with 10-degree (0.63), 15-degree (0.48) and offset reorientating (1.6) liners, compared to neutral liners. There was no association found between liner geometry and risk of revision THA for loosening.

This Registry based study confirms a significantly lower risk of revision THA for instability when a lipped liner is used, compared to neutral liners, and a higher risk with the use of offset reorientating liners. Furthermore, 15degree liners seem to have a lower risk than 10degree liners. We did not find an association between acetabular liner geometry and revision THA for loosening.

10- and 15-degree lipped polyethylene liners seem to offer a lower revision risk over neutral liners, at least at medium term followup. Further studies are required to confirm if this benefit continues into the long-term.

Cemented total hip replacement (THR) provides excellent outcomes and is cost-effective. Polished taper-slip (PTS) stems demonstrate successful results and have overtaken traditional composite-beam (CB) stems. Recent reports indicate they are associated with a higher risk of postoperative periprosthetic femoral fracture (PFF) compared to CB stems. This study evaluates risk factors influencing fracture characteristics around PTS and CB cemented stems.

Data were collected for 584 PFF patients admitted to eight UK centres from 25/05/2006-01/03/2020. Radiographs were assessed for Unified Classification System (UCS) grade and Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association (AO/OTA) type. Statistical comparisons investigated relationships by age, gender, and stem fixation philosophy (PTS versus CB). The effect of multiple variables was estimated using multinomial logistic regression to estimate odds ratios (OR) with 95% confidence intervals (CI).

Median (IQR) age was 79.1 (72.0–86.0) years, 312 (53.6%) patients were female, and 495 (85.1%) stems were PTS. The commonest UCS grade was type B1 (278, 47.6%). The commonest AO/OTA type was spiral (352, 60.3%). Metaphyseal-split fractures occurred only with PTS stems with an incidence of 10.1%. Male gender was associated with a five-fold reduction in odds of a type C fracture (OR 0.22, 95% CI 0.12 to 0.41, p<0.001) compared to a type B fracture. CB stems were associated with significantly increased odds of transverse fracture (OR 9.51, 95% CI 3.72 to 24.34, p <0.001) and wedge fracture (OR 3.72, 95% CI 1.16 to 11.95, p <0.05) compared to PTS stems.

This is the largest study investigating PFF characteristics around cemented stems. The commonest fracture types are B1 and spiral fractures. PTS stems are exclusively associated with metaphyseal-split fractures, but their incidence is low. Males have lower odds of UCS grade C fractures compared to females. CB stems had higher odds of bending type fractures (transverse and wedge) compared to PTS stems. Biomechanical testing is needed for validation and investigation of modifiable factors which may reduce the risk of unstable fracture patterns requiring complex revision surgery over internal fixation.

Orthopaedic surgical hoods rely on an intrinsic fan to force clean external air over the wearer and allow potentially contaminated and expired air to flow down and away from the surgical field. Carbon dioxide (CO₂) is produced through aerobic metabolism and can potentially accumulate inside the hood. Levels above 2500ppm have been shown to affect cognitive and practical function in flight simulator studies. Maximum Health and Safety Executive (HSE) 8-hour exposure limit is 5000ppm There is a paucity of data on real-world CO₂ levels experienced during arthroplasty surgery whilst wearing a hood.

CO₂ levels were continuously recorded during 31 elective arthroplasties, both primary and revision. Data was collected for surgeon and assistant. Data was recorded at 0.5Hz throughout the procedure utilising a Bluetooth CO₂ detector, worn inside a Stryker Flyte^™ surgical helmet worn with a toga gown. Four surgeons contributed real time data to the study. This data was augmented with experimental data, investigating varying fan speeds and activity levels.

Median operative duration was 82 minutes (range 36–207).

The average CO₂ level across all procedures was 2952ppm, with 22 of the cases having a mean above 2500ppm, but none having a mean above 5000ppm.

For each procedure, the time spent above 2500 and 5000 ppm was calculated, with the average being 68.4 % and 5.6% respectively.

The experimental data demonstrated higher CO₂ levels with lower fan speed, and at higher activity levels, and levels exceeding 15000 ppm during gentle exercise. During operative cases, low fan speed cases did have a marginally higher mean CO₂ value than high fan speed (3033.02 and 2903.56 respectively) but the small numbers of cases (n=10) where this data was captured limit the relevance of this difference.

The use of surgical helmets for elective orthopaedic surgery, can results in CO₂ levels regularly rising to a point which may affect cognitive function. This study recommends the use of a higher fan speed where possible to minimise the risk of such CO₂ levels, and recommends further research in this area.

Principles of bone preservation and restoration of biomechanical alignment should be followed during revision total hip arthroplasty (THA). Where possible, conservative femoral revision techniques and even reconstructive de-escalation involving using primary stems should be considered. This study aims to investigate the outcome of patients who have undergone conservative femoral revision THA in our Institution.

We retrospectively identified patients from our Institution's revision arthroplasty database who had cemented, or un-cemented primary stems implanted during revision THA of a previous stemmed femoral implant. Our primary outcome measure was all-cause re-revision THA with a secondary outcome measure of improvement in Oxford hip score (OHS). Radiographic evidence of stem loosening and post-op complications were recorded.

Between 02/12/2014 to 12/12/2019, there were 226 patients identified with a mean follow up of 2 years (1–5 years). The majority of cases were represented by Paprosky type 1 (63%) and type 2 (25%) femoral defects. There were 45 patients (20%) who underwent impaction bone grafting (IBG) and 43 patients (19%) who had a cement in cement (CinC) femoral revision and cemented primary stem in 137 (60%), 1 uncemented stem with no IBG or CinC revision. Kaplan Meier survival for all-cause re-revision THA was 93.7% (95% CI: 88.3 – 100) at 3 years. The reasons for re-revision included 4 periprosthetic fractures, 4 dislocations, 1 deep infection, 1 loosening of femoral component and 1 loosening of acetabular component. Pre- and post-operative OHS scores were available in 137 hips (60%) with a mean improvement of 13. Radiographic review revealed 7% of cases with evidence of loosening in 1 or more Gruen zones.

Our early results support the use of conservative femoral revision THA techniques where appropriate, with low complication and re-revision rates. Revisions using primary femoral components, where appropriate, should be considered in surgical planning to avoid unnecessary reconstructive escalation.

Chondral hip injuries are common secondary to femoroacetabular impingement (FAI). Treatment with arthroscopic procedures including chondroplasty and microfracture is becoming increasingly common but literature is limited to case series at specialist centres. The aim of this study is to compare outcomes of arthroscopic acetabular chondral procedures using the NAHR dataset (UK) which represents the largest series to date.

All adult Arthroscopies recorded in the NAHR from Jan 2012 were available for inclusion. Exclusions included significant arthritis and femoral, complex or revision chondral procedures. Patients completed iHOT-12 & EQ-5D Index pre-operatively, 6 and 12 months. Data was analysed using T-test/ANOVA for between group/within group for continuous variables, chi square test for categorical variables and linear regression model for multivariable analysis.

5,752 patients, 60% female. 27% Chondroplasty, 5% Microfracture, 68% no Chondral Procedure. Maximum acetabular Outerbridge classification 14% Grade 1, 15% Grade 2, 17% Grade 3, 8% Grade 4, 9% no damage, not recorded in 37%. Higher proportion of Cam impingement in association with chondral treatments and a larger proportion of patients with no impingement recorded in group with no chondral procedures. There was a significant improvement versus baseline for all groups in iHOT-12 and EQ-5D Index (p<0.0001) including Grade four Outerbridge. There was significantly greater improvement in pre-operative scores in the chondroplasty group compared to the microfracture group at 6 and 12 months (p<0.05).

Following hip arthroscopy, patients with chondral procedures experienced improved outcome scores despite Outerbridge 4 chondral damage. Presence of cam lesions are more commonly associated with chondral treatments. Good outcomes were maintained up to 12 months for chondral procedures, regardless of age or impingement pathology however pincers improved less and patients over 40 years took longer to see improvement.

The decision to undertake THA in a child is complex and surgery challenging. Pre-operatively patients' typically have significant pain and mobility restriction. Little is published on the functional gains after THA in this group.

The aim of this study was therefore to measure the impact THA had on the PROMS in our young patients undergoing THA, to determine QoL improvement.

This was a prospective, consecutive cohort study of patients under the age of 17 years undergoing THA by a single surgeon in a tertiary referral centre. Patient electronic notes, radiographs, and PROMS (EQ5D-Y, Oxford Hip Score (OHS) and modified Harris Hip Score (mHHS)) were reviewed.

12 children (8 females and 4 males) underwent THA before their 17th birthday, with 5 undergoing bilateral operations (17 THA total). The mean age was 14.6 years (10.75–16.9) and mean follow-up 1.5 years. Nine of the THA were undertaken for congenital syndromes, 4 for AVN, 2 for Perthe's disease and 1 for dysplasia and idiopathic chondrolysis. The mean pre-operative OHS was 15 (1–33) improving to 31 (19–39) at 6-weeks, 44 (42–46) at a year and 48 (47–48) at 3 years. mHHS improved from a pre-operative mean of 25 (0–56) to 60 (37–92) at 6-weeks, 65 (38–84) at a year and 91 (91) at 3 years. The EQ-VAS mean score pre-operatively was 35 (8–100) improving at 6-weeks to 73 (55–96), 84 (76–96) at a year and 92 (76–100) at 3 years. All patients achieved MCID or higher for OHS. 6 patients were wheelchair users preop. All patients were independent walkers at follow-up. There were no complications.

THA in children is safe and leads to a significant positive impact on QoL as measured with validated PROMS scores. Wheelchair users can reliably gain independent walking. Further follow-up is required understand the long-term outcomes.

FAI may cause pain or functional impairment for an individual, as well as potentially resulting in arthritis and degeneration of the hip joint. Results from recent randomised control trials demonstrate the superiority of surgery over physiotherapy in patients with FAI. However, there is paucity of evidence regarding which factors influence outcomes for FAI surgery, most notably on patient reported outcomes measures (PROMs).

Our study looks to explore factors influencing the outcomes for patients undergoing surgery for FAI utilising data from the Non-Arthroplasty Hip Registry.

This study is a retrospective analysis of data collected prospectively via the NAHR database. Patients meeting the inclusion criteria, who underwent surgery between January 2011 and September 2019 were identified and included in the study. Follow-up data was captured in September 2020 to allow a minimum of 12 months follow-up.

Patients consenting to data collection received questionnaires to determine EQ-5D Index and iHOT-12 scores preoperatively and at 6 months, 1, 2- and 5-year follow-up.

Changes in outcome scores were analysed for all patients and sub-analysis was performed looking at the influence of; FAI morphological subtype, age, and sex, on outcome scores.

Our cohort included 4,963 patients who underwent arthroscopic treatment for FAI. There was significant improvement from pre-operative PROMs when compared with those at 6 and 12 months.

Pre-operatively, and at 12-month follow-up, iHOT-12 scores were significantly better for the cam / mixed groups compared to the pincer group (p<0.01).

In multivariable regression analysis, pincer pathology and a high-grade chondral lesion were associated significantly poorer iHOT-12 improvement at 6 and 12 months (p<0.05)

Age (<40 vs >40) demonstrated no statistical significance when considering 12 months outcome scores.

This study demonstrates that hip arthroscopy is an effective treatment for patients with symptomatic FAI and shows statistically significant improvements at 12 months.

The findings of this study are relevant to orthopaedic surgeons who manage young adults with hip pathology. This will help them to; predict which patients may benefit from operative intervention, and better inform patients, when undertaking shared decision making.

Considerable debate exists regarding which agent(s) should be preferred for venous thromboembolism (VTE) chemical prophylaxis following joint replacement. We assessed the practice of surgeons regarding VTE chemical prophylaxis for primary THR and TKR, pre and post issuing of updated NICE guidance in 2018.

A survey, circulated through the British Hip Society and regional trainee networks/collaboratives, was completed by 306 UK surgeons at 187 units. VTE chemical prophylaxis prescribing patterns for surgeons carrying out primary THR (n=258) and TKR (n=253) in low-risk patients were assessed post publication of 2018 NICE recommendations. Prescribing patterns before and after the NICE publication were subsequently explored. Questions were also asked about surgeon equipoise for participation in future RCTs.

Following the new guidance, 34% (n=87) used low-molecular weight heparin (LMWH) alone, 33% (n=85) aspirin (commonly preceded by LMWH), and 31% (n=81) direct oral anticoagulants (DOACs: with/without preceding LMWH) for THR. For TKR, 42% (n=105) used aspirin (usually monotherapy), 31% (n=78) LMWH alone, and 27% (n=68) DOAC (with/without preceding LMWH). NICE guidance changed the practice of 34% of hip and 41% of knee surgeons, with significantly increased use of aspirin preceded by LMWH for THR (before=25% vs. after=73%;p<0.001), and aspirin for TKR (before=18% vs. after=84%;p<0.001). Significantly more regimens were NICE guidance compliant after the 2018 update for THR (before=85.7% vs. after=92.6%;p=0.011) and TKR (before=87.0% vs. after=98.8%;p<0.001). Support from surgeons for future RCTs was dependent on the clinical question, ranging from 48% participation in trials (effectiveness of aspirin vs. a DOAC) to 79% (effectiveness of 14 days LMWH vs. 28 days LMWH).

Over one-third of surveyed surgeons changed their VTE chemical prophylaxis in response to 2018 NICE recommendations, with more THR and TKR surgeons now compliant with latest NICE guidance. The major change in practice was an increased use of aspirin for VTE chemical prophylaxis. Furthermore, there is an appetite amongst UK surgeons for participating in future RCTs, with a trial comparing standard versus extended duration LMWH likely feasible in current practice.

Trabecular metal (TM) augments are designed to support an uncemented socket in revision surgery when adequate rim fit is not possible. We have used TM augments in an alternative arrangement, to contain segmental defects to facilitate impaction bone grafting (IBG) and cementation of a cemented socket. However, there is a paucity of literature supporting the use of this technique. We present one of the largest studies to date, reporting early outcomes of patients from a tertiary centre.

A single-centre retrospective analytical study of prospectively collected data was performed on patients who had undergone complex acetabular reconstruction using TM augments, IBG and a cemented cup. All patients operated between 2015 and 2019 were included. We identified 105 patients with a mean age of 74yrs. The mean follow-up was 2.3 years(1–5.5yrs). Our primary outcome measure was all-cause revision of the construct. The secondary outcome measures were, Oxford hip score (OHS), radiographic evidence of cup migration/loosening and post-op complications.

Eighty-four out of 105 patients belonged to Paprosky grade IIb, IIc or IIIa. Kaplan-Meier survivorship for all-cause revision was 96.36% (CI, 90.58–100.00) at 2 years with 3 failures. Two were due to early infection which required two-stage re-revision. The third was due to post-operative acetabular fracture which was then re-revised with TM augment, bone graft and large uncemented cup. Pre-op and post-op matched OHS scores were available for 60 hips(57%) with a mean improvement of 13 points. Radiographic analysis showed graft incorporation in all cases with no evidence of cup loosening. The mean vertical cup migration was 0.5mm (Range −5 to 7mm). No other complications were recorded.

This study shows that reconstruction of large acetabular defects during revision THA using a combination of TM augments to contain the acetabulum along with IBG to preserve the bone stock and a cemented socket is a reliable and safe technique with low revision rates and satisfactory clinical and radiographic results. Long term studies are needed to assess the possibility of preservation and regeneration of bone stock.

Cemented acetabular components commonly have a long posterior wall (LPW). Alternative components have a hooded or offset reorientating geometry, theoretically to reduce the risk of THR instability. We aimed to determine if cemented acetabular component geometry influences the risk of revision surgery for instability or loosening.

The National Joint Registry for England, Wales and Northern Ireland (NJR) dataset was analysed for primary THAs performed between 2003 – 2017. A cohort of 224,874 cemented acetabular components were identified. The effect of acetabular component geometry on the risk of revision for instability or for loosening was investigated using binomial regression adjusting for age, gender, ASA grade, diagnosis, side, institution type, operating surgeon grade, surgical approach, polyethylene crosslinking and head size. A competing risk survival analysis was performed with the competing risks being revision for other indications or death.

Among the cohort of subjects included, the distribution of acetabular component geometries was: LPW – 81.2%, hooded – 18.7% and offset reorientating – 0.1%. There were 3,313 (1.47%) revision THAs performed, of which 815 (0.36%) were for instability and 838 (0.37%) were for loosening. Compared to the LPW group, the adjusted subhazard ratio of revision for instability in the hooded group was 2.29 (p<0.001) and 4.12 (p=0.047) in the offset reorientating group. Likewise, the subhazard ratio of revision for loosening was 2.43 (p<0.001) in the hooded group and 11.47 (p<0.001) in the offset reorientating group. A time-varying subhazard ratio of revision for instability (hooded vs LPW) was found, being greatest within the first 6 months.

This Registry based study confirms a significantly higher risk of revision THA for instability and for loosening when a cemented hooded or offset reorientating acetabular component is used, compared to an LPW component. Further research is required to clarify if certain patients benefit from the use of hooded or offset reorientating components, but we recommend caution when using such components in routine clinical practice.

Pelvic re-orientation osteotomy is a well-recognised treatment of young adults with developmental dysplasia of the hip (DDH).

The most commonly used technique is the periacetabular osteotomy (PAO), however, some surgeons favour a triple osteotomy. These techniques can also be utilised for acetabular retroversion leading to FAI.

Despite the published literature on these techniques, the authors note a scarcity of evidence looking at patient reported outcome measures (PROMs) for these procedures.

This was a retrospective analysis of prospectively collected data utilising the UK NAHR. All patients who underwent pelvic osteotomy from January 2012 to November 2019 were identified from the NAHR database. Patients who consented to data collection received EQ-5D index and iHOT-12 questionnaires, with scores being collected pre-operatively and at 6, 12 and 24 months post-operatively.

Nine hundred and eleven (911) patients were identified with twenty-seven (27) undergoing a triple osteotomy, the remaining patients underwent PAO. Mean age was 30.6 (15–56) years and 90% of patients were female. Seventy-nine (79) (8.7%) of patients had the procedure for acetabular retroversion leading to FAI

Statistical analysis, of all patients, showed significant improvement (p<0.001) for; iHOT-12 scores (+28 at 6-months, +33.8 at 12-months and +29.9 at 24-months)

Similarly there was significant improvement (p<0.001) in EQ-5D index (+0.172 at 6-months, +0.187 at 12-months and +0.166 at 24-months)

Pre-operatively, and at each follow-up time-period, raw scores were significantly better in the DDH group compared to the FAI group (p<0.05); however, the improvement in scores was similar for both groups.

For both scoring measures, univariable and multivariable linear regression showed poorer pre-operative scores to be strongly significant predictors of greater post-operative improvement at 6 and 12 months (p<0.0001).

Aims

This study evaluates risk factors influencing fracture characteristics for postoperative periprosthetic femoral fractures (PFFs) around cemented stems in total hip arthroplasty.

Abstract

Abstract

Abstract

Abstract

Impingement of total hip replacements (THRs) can cause rim damage of polyethylene liners, and lead to dislocation and/or mechanical failure of liner locking mechanisms[1]. Previous work has focussed on the influence of femoral neck profile on impingement without consideration of neck-shaft angle. This study assessed the occurrence of impingement with two different stem designs (Corail standard [135°] and coxa vara [125°]) under different activities with varying acetabular cup orientation (30° to 70° inclination; 0° to 50° anteversion) using a geometric modelling tool.

The tool was created in a computer aided design software programme, and incorporated an individual's hemi-pelvis and femur geometry[3] with a THR (DePuy Synthes Pinnacle^® shell and neutral liner; size 12 Corail^® standard or coxa vara and 32mm head). Kinematic data of activities associated with dislocation[2], such as stooping to pick an object from the floor was applied and incidences of impingement were recorded.

Predicted implant impingement was influenced by stem design. The coxa vara stem was predicted to cause implant impingement less frequently across the range of activities and cup orientations investigated, compared to the standard stem [Fig. 1]. The cup orientations predicted to cause impingement the least frequently were at lower inclination and anteversion angles, relative to the standard stem [Fig. 1]. The coxa vara stem included a collar, while the standard stem was collarless; additional analysis indicated that differences were due to neck angle and not the presence of a collar.

This study demonstrated that stem neck-shaft angle is an important variable in prosthetic impingement in THR and surgeons should be aware of this when choosing implants. Future work will consider further implant design and bone geometry variables. This tool has the potential for use in optimising stem design and position and could assist with patient specific stem selection based on an individual's activity profile.

For any figures or tables, please contact the authors directly.

Background

Antibiotic loaded bone cement (ALBC) is commonly used in cemented total hip arthroplasty (THA) in an attempt to reduce the risk of prosthetic joint infection (PJI). However, its role versus plain cement remains controversial due to the potential risk of developing resistant organisms and potential excess costs incurred from its usage. We investigated the relationship of ALBC and plain cement in affecting outcome of revision surgery after primary THA.

Introduction

Impingement of total hip arthroplasties (THAs) has been reported to cause rim damage of polyethylene liners, and in some instances has led to dislocation and/or mechanical failure of liner locking mechanisms in modular designs. Elevated rim liners are used to improve stability and reduce the risk of dislocation, however they restrict the possible range of motion of the joint, and retrieval studies have found impingement related damage on lipped liners.

The aim of this study was to develop a tool for assessing the occurrence of impingement under different activities, and use it to evaluate the effects a lipped liner and position of the lip has on the impingement-free range of motion.

In order to reduce the risk of dislocation larger femoral heads in total hip arthroplasty (THA) are being used by surgeons in recent years. The standard head size of 28 mm used in 73% of all hip procedures in 2003 was used in only 29% in 2016; whereas head sizes of 32 mm and 36 mm combined, were used in 70%. The increase of head size effectively reduces the thickness of the acetabular cup, altering the load transfer. Herein, this research work investigates the effect of increasing the femoral head size on the stresses of the periacetabular bone at two selected regions: A1 (superior) and A2 (anterior). Three Finite Element models were developed from CT scan data of a hemipelvis implanted with a cemented all-polyethylene acetabular cup with a 50 mm outer diameter and inner diameter to accommodate three head sizes: 28 mm, 32 mm and 36 mm. The peak reaction force at the hip joint during one leg stand for an overweight patient with a body weight of 100 Kg was simulated for head sizes investigated. We found that highest average von Mises stress was 5.7 MPa and occurred in the cortical bone of region A1 which is located within Zone 1 boundaries (Charnley &DeLee); whereas a lower stress of 4.0 MPa occurred at region A2. In the two regions the stresses were the same for the three head sizes. Periacetabular bone was found to be insensitive to the increase of femoral head diameter in cemented THA.

Introduction

The use of larger femoral heads in Total Hip Arthroplasty has increased in order to reduce the risk of dislocation and to improve the range of motion of the joint. In 2003, within the UK, the “standard” head size of 28mm was used in 73% of all hip procedures, whereas by 2012, this figure dropped to 36%. Concerns regarding the impact of this increment in head size on the cement and bone stresses have arisen; however, this has yet to be clearly determined.

Prosthetic joint infection continues to remain a diagnostic challenge for unhappy primary arthroplasty of hip and knees. There is increasing dependence upon alpha-defensin test to make key decisions like whether to revise or not & to decide between one-stage versus two-stage.

Background

One of the major concerns of hinge knees have been reported in literature is mechanical failure. Failure in the form of component fracture (2–10%) and hinge dislocation/ failure are worrisome. In addition, higher risk of aseptic loosening with hinge knee prosthesis has been attributed to stress transfer at bone cement interface.

Occlusion of the femoral canal is an important step in cemented hip arthroplasty. The goal of occlusion is to allow cement pressurisation and prevent cement egress into the femoral diaphysis. There are numerous designs of cement plugs made out of different materials but there is no consensus or clinical guideline for the choice of cement restrictors. At our centre two types of plugs are used – autologous bone block from femoral canal and the gelatine C-plug (Depuy International). We conducted this study to evaluate the stability of these two plugs and their effect on quality of cementation.

The purpose of our study was to assess retrospectively both the length of the “cement tail” i.e. the length of the cement column distal to the stem tip and the cement mantle quality in both groups.

A retrospective comparative review was designed after approval from the local R & D department. Power analysis indicated that a minimum of 74 patients per group would be needed. A total of 203 consecutive patients were analysed, 89 received an autologous bone block and 114 had C-plugs. Apart from the plugs both the groups were treated similarly with regards to surgical approach, cementing and operative technique. Surgical technique was to achieve adequate pressurisation and a minimum length of cement tail.

Immediate post-operative radiographs were used for analysis. The primary outcome measure was the length of the cement tail, i.e. the length of the cement column from the tip of the stem. The secondary outcome measure was the quality of cementing which was quantified using Barrack's grading.

The data was tested for normality using the Shapiro-Wilk test. The means of cement tail lengths in between the two groups were compared using the Wilcoxon ranked sum test. The cementation grades were compared using ANOVA. The correlation between the length of cement tail and the quality of cementation was calculated using ordinal regression.

Both the groups were similar in terms of age, sex and primary diagnosis. The mean cement tail length was 6.42 (SE 0.71 mms; range-0–31) in the bone block group and 17.11 (SE-1.34 mms; range 0–65.7 mms) in the C-plug group. This difference was statistically significant (p< 0.0001). The proportion of patients with good quality of cementation (grade A) was significantly higher in the bone block group (80.6%) as compared to the C-plug group (56%) (p < 0.0001). There was a negative correlation between the length of the cement tail and the Barrack grade (rho=0.398), indicating that a short cement tail is associated with better quality cementation.

Quality of cementation is of paramount importance in cemented hip arthroplasty. Revision surgery can be more difficult and higher risk in the presence of a long cement tail. We have shown that better quality cementation and shorter cement tails can be achieved with the cheapest of all options for canal occlusion, an autologous bone block and recommend its use.

Synovasure has been designed and validated for use in the diagnosis of periprosthetic joint infection (PJI). It has a reported sensitivity of 97.4% (CI 86.1–99.6%) and specificity of 95.8% (CI 90.5–98.6%), higher than the variable results reported for aspiration by most units. At a cost of £500 per test, we aimed to establish cost-effectiveness and diagnostic accuracy, to determine its role in routine practice.

We developed a protocol for pre-operative aspiration or intra-operative use. Prerequisites for entry were a high index of clinical suspicion for PJI and equivocal standard investigations. All cases were discussed at the lower limb arthroplasty MDT and approved only if use would change clinical management.

Over 15 months, 36 tests were approved for 22 aspirations (5 hip, 17 knee) and 14 intra-operative cases (7 hip, 7 knee). 10/36 had undergone previous revision surgery. 35/36 cases complied with the protocol. All 22 Synovasure aspirations were negative, corresponding to the microbiology in all but one case; thought to be a contaminant. In the intra-operative group there was one true positive and 12 true negative tests, giving a sensitivity of 100% (95% CI 2.5–100%) and a specificity of 100% (95% CI 73.5–100%). Synovasure influenced decision making in 34/36 procedures. One test failed and in another there was evidence of frank infection. In 11 cases no surgery was performed versus a potential two-stage revision and in 21 cases a single rather than two-stage revision was performed. Resulting in estimated savings of £686,690, offset against a cost of £18,000.

The Synovasure test was found to be sensitive and specific and can aid decision-making particularly in complex cases with an equivocal diagnosis of PJI. The use of this test through a robust protocol driven peer review MDT process not only reduces patient morbidity but drives significant efficiency savings.