Personalised 3D Printed high tibial osteotomy achieves a high level of accuracy: 'IDEAL' preclinical stage evaluation of a novel patient specific system.

High tibial osteotomy (HTO) is an effective surgical treatment for isolated medial compartment knee osteoarthritis; however, widespread adoption is limited due to difficulty in achieving the planned correction, and patient dissatisfaction due to soft tissue irritation. The aim of this study was to assess the accuracy of a novel HTO system with 3D printed patient specific implants and surgical guides using cadaveric specimens. Local ethics committee approval was obtained. The novel opening wedge HTO procedure was performed on eight cadaver leg specimens. Whole lower limb CT scans pre- and post-operatively provided geometrical assessment quantifying the discrepancy between pre-planned and post-operative measurements for key variables: the gap opening angle and the patient specific surgical instrumentation positioning. The average discrepancy between the pre-operative plan and the post-operative osteotomy correction angle was: 0.0 ±â€ˆ0.2° The R2 value for the regression correlation was 0.95. The average error in implant positioning was -0.4 ±â€ˆ4.3 mm, -2.6 ±â€ˆ3.4 mm and 3.1 ±â€ˆ1.7° vertically, horizontally, and rotationally respectively. This novel HTO surgery has greater accuracy in correction angle achieved compared to that reported for conventional or other patient specific methods with published data available. This system could potentially improve the accuracy of osteotomy correction angles achieved surgically.

Regional economic burden of revision total knee replacement: A cost-complexity analysis.

BACKGROUND: GIRFT tasked regional networks with addressing case-load, complexity-spread and cost of revision knee replacement (KR), but the regional cost burden is not clear. The tariff for revision KR is currently not dependent on surgical complexity. 2 years of revision KR complexity data using the validated Revision Knee Complexity Classification (RKCC) checklist as a demonstration of complexity spread in the region has previously been published. The aims of this study were to estimate the annual regional cost of revision TKR using existing data, and estimate the cost/saving of complexity-clustering using existing data from 8 revision centres. METHODS: Financial data from the regional high-volume centre for one year (2019) of RKCC data collection was obtained. Mean cost, tariff and balance was calculated for R1, R2 and R3 (RKCC), and applied to data from each revision centre to provide local estimates. Complexity clustering was considered using 3 hypothetical scenarios of high-volume centre absorbing R2s and/or R3s in place of R1s. RESULTS: Mean net loss was £2,290.08 for R1s, £6,471.42 for R2s and £6,454.26 for R3s. The estimated total annual loss for the region was £1,005,025. Complexity-clustering was associated with greater losses; £162,918 for high-volume centre taking R2s and R3s, £37,477.60 for taking just R3s and £125,440 for taking just R2s. CONCLUSION: Revision TKR surgery is expensive and insufficiently remunerated with current measures. Restructuring of regional workload would create additional financial burden on specialist centres with current tariff awards structure. Managing reimbursement at a regional or central level may help to incentivise compliance with GIRFT ideals.

Revision total knee replacement: A two-year review of complexity data and regional workload in South West England.

BACKGROUND: The GIRFT report (2012) sought to address the need for sustainable orthopaedic treatment delivered through regional "networks"; the aim being improved care, decreased cost and reduced revision rate. The aims of this study were to record the number and complexity of revision total knee replacements within a regional network using a validated classification over a two-year period and audit this against National Joint Registry (NJR) records. METHODS: A region-wide network model where revision TKR cases are assessed locally using the Revision Knee Complexity Classification (RKCC) and local multi-disciplinary team (MDT) was introduced. Data was collected from 8 revision centres over a two-year period using the RKCC. The case volume was audited against the NJR records. RESULTS: In year 1 (01/01/2018-31/12/2018) 237 RKCC forms were collected from eight centres. 46% of R2s and 63% of R3s were carried out at the higher volume centre. 211 K2 forms were received by the NJR. In year 2 (01/01/2019-31/12/2019) 252 RKCC forms were collected. 46% of R2s and 64% of R3s were carried out at the higher volume centre. 267 K2 forms were received by the NJR. CONCLUSION: This is the first published set of revision knee data showing complexity percentages across a region. The RKCC has been successfully introduced into the region and this has been sustained. The findings show that a successful network has been established and majority of complex revision knee surgery is occurring in the high-volume centre. NJR data suggests that the RKCC is capturing the complexity and volume of our work accurately.

Revision knee replacement surgery in the NHS: A BASK surgical practice guideline.

BACKGROUND: Revision knee replacement (KR) is both challenging for the surgical team and expensive for the healthcare provider. Limited high quality evidence is available to guide decision-making. AIM: To provide guidelines for surgeons and units delivering revision KR services. METHODS: A formal consensus process was followed by BASK's Revision Knee Working Group, which included surgeons from England, Wales, Scotland and Northern Ireland. This was supported by analysis of National Joint Registry data. RESULTS: There are a large number of surgeons operating at NHS sites who undertake a small number of revision KR procedures. To optimise patient outcomes and deliver cost-effective care high-volume revision knee surgeons working at high volume centres should undertake revision KR. This document outlines practice guidelines for units providing a revision KR service and sets out: The current landscape of revision KR in England, Wales and Northern Ireland. Service organisation within a network model. The necessary infrastructure required to provide a sustainable revision service. Outcome metrics and auditable standards. Financial mechanisms to support this service model. CONCLUSIONS: Revision KR patients being treated in the NHS should be provided with the best care available. This report sets out a framework to both guide and support revision KR surgeons and centres to achieve this aim.

Clinical prioritisation of revision knee surgical procedures: BASK working group consensus document.

BACKGROUND: Elective orthopaedic surgery during the Covid-19 pandemic requires careful case prioritisation. We aimed to produce consensus-based guidelines on the prioritisation of revision total knee arthroplasty (TKA) procedures. METHOD: Twenty-three revision TKA scenarios were assigned priority (NHS England/Royal College of Surgeons scale) by the British Association for Surgery of the Knee (BASK) Revision Knee Working Group (n = 24). Consensus agreement was defined as ≥70% respondents (18/24) giving the same prioritisation. Two voting rounds were undertaken; procedures achieving <70% agreement were given their most commonly assigned priority. RESULTS: 18/23 procedures achieved ≥70% agreement. Three were P1a (surgery within <24 h); DAIR for sepsis, peri-prosthetic fracture (PPF) fixation and PPF-revision TKA. Three were P1b (<72 h); debridement, antibiotics and implant retention (DAIR) for a stable patient, flap coverage for an open knee, and acute extensor mechanism rupture. Eight were P2 (<4 weeks), including aseptic loosening at risk of collapse, inter-stage patients with poor functioning spacers. Five were P3 (<3 months), including second stage revision for infection, revision for instability with limited mobility. Four were P4 (can wait >3 months) e.g. aseptic loosening. CONCLUSION: Sepsis and PPF surgery are the most urgent procedures. Although most procedures should be undertaken within one to three months (P2/3), these cases represent a small revision practice volume; P4 cases (e.g. aseptic loosening without risk of collapse) make up most surgeons' caseload. These recommendations are a guideline; patient co-morbidities, Covid-19 pathways, availability of support services and multi-disciplinary team discussion within the regional revision network will dictate prioritisation.

Investigation and management of prosthetic joint infection in knee replacement: A BASK Surgical Practice Guideline.

BACKGROUND: The burden of knee replacement prosthetic joint infection (KR PJI) is increasing. KR PJI is difficult to treat, outcomes can be poor and it is financially expensive and limited evidence is available to guide treatment decisions. AIM: To provide guidelines for surgeons and units treating KR PJI. METHODS: Guideline formation by consensus process undertaken by BASK's Revision Knee Working Group, supported by outputs from UK-PJI meetings. RESULTS: Improved outcomes should be achieved through provision of care by revision centres in a network model. Treatment of KR PJI should only be undertaken at specialist units with the required infrastructure and a regular infection MDT. This document outlines practice guidelines for units providing a KR PJI service and sets out: CONCLUSIONS: KR PJI patients treated within the NHS should be provided the best care possible. This report sets out guidance and support for surgeons and units to achieve this.

Provision of revision knee surgery and calculation of the effect of a network service reconfiguration: An analysis from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man.

BACKGROUND: Revision knee replacement (KR) is technically challenging, expensive, and outcomes can be poor. It is well established that increasing surgeon and unit volumes results in improved outcomes and cost-effectiveness for complex procedures. The aim of this study was to 1) describe the current provision of revision KR in England, Wales and Northern Ireland at the individual surgeon and unit level and 2) investigate the effect on workload of case distribution in a network model. METHODS: Current practice was mapped using NJR summary statistics containing all revision KR procedures performed over a three-year period (2016-2018). Units were identified as revision centres based on threshold volumes. Units undertaking <20 revisions per year were classified as Primary Arthroplasty Units (PAUs) in calculations on the effect of workload centralisation. RESULTS: Revision KR was performed by 1353 surgeons at 232 NHS sites. The majority of surgeons and units were low-volume; >1000 surgeons performed <7 and 125 sites performed <20 procedures per year. Reallocation of work from these 125 PAUs (1235 cases, 21% of total workload) to a network model with even redistribution of cases between centres undertaking revision surgery would result in an additional average annual case increase of 11 per unit per year (range six to 14). CONCLUSIONS: Revision KR workload re-allocation would lift all revision centres above a 30 per year threshold and would appear to be a manageable increase in workload for specialist revision KR centres. Case complexity and local referral agreements will significantly affect the real increase in workload; these factors were not incorporated here.

The first knee prosthesis to go through beyond compliance: A new standard for the safe introduction of orthopaedic implants.

INTRODUCTION: Beyond Compliance (BC) was introduced in 2012 to improve the monitoring and regulation of new medical devices and techniques, ensuring patient safety whilst promoting innovation through an evidence based appraisal of devices during their introduction. This study reports the 2 year outcomes of the first Total Knee Replacement (TKR) implant to be assessed through the BC process. METHODS: 100 consecutive patients undergoing primary knee arthroplasty were enrolled. All patients received a single radius cruciate retaining TKA (Unity, Corin), and the patella was resurfaced in all cases. Patients were followed up at 6 weeks, 3, 6, 12 and 24 months post operatively. Pre-and post-operative range of movement (ROM) as well as outcome scores including OKS, KOOS, EQ5D index and EQ5D VAS were recorded. RESULTS: 100 patients with a mean age 73.6 (SD = 8.7) were included. 2 patients died during the follow-up period due to unrelated reasons. Overall satisfaction rates were 96%. Complications included ongoing pain (5 patients), and a periprosthetic fracture (1 patient) nine months post-surgery (traumatic). No knees were revised during the follow-up period. Significant improvements were observed in all outcomes measures (OKS, KOOS, EQ5D, and EQ5D VAS). The mean added ROM was 13.2°. DISCUSSION: This knee prosthesis has been demonstrated to be safe and effective with excellent early outcomes. The careful regulated introduction of this device through BC has ensured patients safety while supporting innovation in knee arthroplasty. The success of BC requires surgeons to insist industry fully engage with the process for all new devices or techniques.

Revision knee complexity classification-RKCC: a common-sense guide for surgeons to support regional clinical networking in revision knee surgery.

PURPOSE: There is considerable variation in practice throughout Europe in both the services provided and in the outcomes of Revision Knee Surgery. In the UK, a recent report published called get it right first time (GIRFT) aims to improve patient outcomes through providing high quality, cost-effective care, and reducing complications. This has led to the development of a classification system that attempts to classify the complexity of revision knee surgery, aiming to encourage and support regional clinical networking. METHODS: The revision knee classification system (RKCC) incorporates not only complexity, but also patient factors, the presence of infection, the integrity of the extensor mechanism, and the soft tissues. It then provides guidance for clinical network discussion. Reliability and reproducibility testing have been performed to establish the inter- and intra-observer variabilities using this classification. RESULTS: Good correlation between first attempt non-expert and experts, good intra-observer variability of non-expert, and an excellent correlation between second attempt non-expert and experts has been achieved. This supports the use of RKCC by both inexperienced and experienced surgeons. CONCLUSIONS: The revision knee complexity classification has been proposed that offers a common-sense approach to recognize the increasing complexity in revision TKR cases. It provides a methodological assessment of revision knee cases and support regional clinical networking and triage of appropriate cases to revision units or specialist centres. LEVEL OF EVIDENCE: Expert opinion, Level V.

Outcome of kinematic alignment using patient-specific instrumentation versus mechanical alignment in TKA: a meta-analysis and subgroup analysis of randomised trials.

INTRODUCTION: Kinematic alignment (KA) in total knee arthroplasty (TKA) matches component position to the pre-arthritic anatomy of an individual patient, with the aim of improving functional outcomes. Recent randomised controlled trials (RCTs) comparing KA to traditional neutral mechanical alignment (MA) have been mixed. This collaborative study combined raw data from RCTs, aiming to compare functional outcomes between KA using patient-specific instrumentation (PSI) and MA, and whether any patient subgroups may benefit more from KA technique. MATERIALS AND METHODS: A literature search in PubMed, EMBASE and Cochrane databases identified four randomised controlled trials comparing patients undergoing TKA using PSI-KA and MA. Unpublished data including Western Ontario McMaster Universities Arthritis Index (WOMAC) and Knee Society Score (KSS) were obtained from study authors. Meta-analysis compared MA to KA change (post-op minus pre-op) scores. Subgroup-analysis on KA patients looked for subgroups more likely to benefit from KA and the impact of PSI accuracy. RESULTS: Meta-analyses of change scores in 229 KA patients versus 229 MA patients were no different from WOMAC (mean difference 3.4; 95% confidence interval - 0.5 to 7.3), KSS function (1.3, - 3.9 to 6.4) or KSS combined (7.2, - 0.8 to 15.2). A small advantage was seen for KSS pain in the KA group (3.6, 95% CI 0.2-7.1). Subgroup-analysis showed no difference between varus, valgus and neutral pre-operative alignment groups, and those who did and did not achieve KA plans. Pain-free patients at 1-year were more likely to achieve KA plans. CONCLUSION: Patient-reported outcome scores following TKA using PSI-KA are similar to MA. No identifiable subgroups benefited more from KA, and long-term results remain unknown. Inaccuracy of the PSI system used in KA patients could potentially affect outcome.

The largest survivorship and clinical outcomes study of the fixed bearing Stryker Triathlon Partial Knee Replacement - A multi-surgeon, single centre cohort study with a minimum of two years of follow-up.

BACKGROUND: The surgical management of isolated medial compartment degenerative disease of the knee causes debate. Unicompartmental arthroplasty options include fixed and mobile bearing implant designs with fixed bearing becoming increasingly popular. We present the largest cohort of a fixed bearing single radius design, Stryker Triathlon Partial Knee Replacement (PKR). METHODS: We prospectively collected demographic data and patient reported outcome measures (PROMs) on our cohort of PKR implants since its adoption in our unit, 2009 until March 2015. RESULTS: A total of 129 implants in 115 patients with a mean follow-up of 5.5 years (2.5 to 8.5 years) were included. There were 11 revisions at an average of 1.7 years (0.6-4.1 years), two for infection, two for mal-alignment, five for progression of disease and two for loosening. The survivorship of the implants at five years is 90%. CONCLUSION: The PKR provides good survivorship at five years and PROM scores that are equal to the largest and most popular comparable implants. There is an associated learning curve with this implant, as there is with all systems and this is reflected in our results.

Disuse osteopenia following leg fracture in postmenopausal women: Implications for HIP fracture risk and fracture liaison services.

INTRODUCTION: Disuse osteopenia is a known consequence of reduced weight-bearing and has been demonstrated at the hip following leg injury but has not been specifically studied in postmenopausal women. METHOD: Bilateral DXA (GE Lunar Prodigy) bone mineral density (BMD) measurements were taken at the neck of femur (NOF), total hip region (TH) and lumbar spine in postmenopausal female groups comprising controls (N = 43), new leg fractures (#<3wks) (N = 9), and participants who had sustained a leg fracture more than one year previously (#>1yr) (N = 24). #>1yr were assessed at a single visit and the remaining groups at intervals over twelve months. Weight-bearing, function, 3-day pedometer readings, and pain levels were also recorded. RESULTS: The #<3wks demonstrated significant (p < 0.05) losses in ipsilateral TH BMD at 6 weeks from baseline 0.927 ± 0.137 g/cm2, to 0.916 ± 0.151 g/cm2 improving to 0.946 ± 0.135 g/cm2 (n.s) at 12 months following gradual return to normal function and weight-bearing activity. The #>1yr scored significantly below controls in almost all key physical and functional outcomes demonstrating a long-term deficit in hip bone density on the ipsilateral side. CONCLUSION: The clinical significance of post-fracture reduction in hip BMD is a potential increased risk of hip fracture for a variable period that may be mitigated after return to normal function and weight-bearing. Improvement at 12 months in #<3wks is not consistent with #>1yr results indicating that long-term impairment in function and bone health may persist for some leg fracture patients. Unilateral bone loss could have implications for Fracture Liaison Services when assessing the requirement for medication post fracture.

Mid-term survivorship and clinical outcomes of the Avon patellofemoral joint replacement.

BACKGROUND: We present the largest series of Avon patellofemoral joint (PFJ) replacements outside of the design centre. There is discussion over its efficacy and usefulness. We report an independent opinion of its indications, survivorship and outcomes. METHODS: We prospectively collected demographic data and patient reported outcome measures (PROM's) on our cohort of Avon Patellofemoral replacements since its adoption in our unit in 2003 until 2014. We performed a retrospective review of radiographs. RESULTS: We performed 103 PFJ replacements in 85 patients, 36 were male (mean age 61 - range 34 to 78) and 67 female (mean age 60 - range 38 to 82), mean follow up time was 5.6years (range 2.9 to 14.2years) with 93 implants still in situ. Their mean post-operative Oxford Knee Score was 36 (range seven to 48). There were nine conversions to TKR for disease progression and one revision of a femoral component for trochlear malpositioning. Mean time to revision was 2.9years (1.0 to 6.0years). Radiographic evidence of progression on Kellgren and Lawrence score in the un-replaced compartments was demonstrated in 23% of cases with imaging available. The Avon PFJ replacement delivers reproducible and effective pain relief and function to patients with isolated patellofemoral osteoarthritis. We believe PFJ replacement has an important role to play, and we will continue to perform this procedure for a carefully selected group of patients. Conversion to TKR does not and should not be regarded as failure of the index operation.

The effect of plate design, bridging span, and fracture healing on the performance of high tibial osteotomy plates: An experimental and finite element study.

OBJECTIVES: Opening wedge high tibial osteotomy (HTO) is an established surgical procedure for the treatment of early-stage knee arthritis. Other than infection, the majority of complications are related to mechanical factors - in particular, stimulation of healing at the osteotomy site. This study used finite element (FE) analysis to investigate the effect of plate design and bridging span on interfragmentary movement (IFM) and the influence of fracture healing on plate stress and potential failure. MATERIALS AND METHODS: A 10° opening wedge HTO was created in a composite tibia. Imaging and strain gauge data were used to create and validate FE models. Models of an intact tibia and a tibia implanted with a custom HTO plate using two different bridging spans were validated against experimental data. Physiological muscle forces and different stages of osteotomy gap healing simulating up to six weeks postoperatively were then incorporated. Predictions of plate stress and IFM for the custom plate were compared against predictions for an industry standard plate (TomoFix). RESULTS: For both plate types, long spans increased IFM but did not substantially alter peak plate stress. The custom plate increased axial and shear IFM values by up to 24% and 47%, respectively, compared with the TomoFix. In all cases, a callus stiffness of 528 MPa was required to reduce plate stress below the fatigue strength of titanium alloy. CONCLUSION: We demonstrate that larger bridging spans in opening wedge HTO increase IFM without substantially increasing plate stress. The results indicate, however, that callus healing is required to prevent fatigue failure.Cite this article: A. R. MacLeod, G. Serrancoli, B. J. Fregly, A. D. Toms, H. S. Gill. The effect of plate design, bridging span, and fracture healing on the performance of high tibial osteotomy plates: An experimental and finite element study. Bone Joint Res 2018;7:639-649. DOI: 10.1302/2046-3758.712.BJR-2018-0035.R1.

The early outcome of kinematic versus mechanical alignment in total knee arthroplasty: a prospective randomised control trial.

AIMS: Our aim was to compare kinematic with mechanical alignment in total knee arthroplasty (TKA). PATIENTS AND METHODS: We performed a prospective blinded randomised controlled trial to compare the functional outcome of patients undergoing TKA in mechanical alignment (MA) with those in kinematic alignment (KA). A total of 71 patients undergoing TKA were randomised to either kinematic (n = 36) or mechanical alignment (n = 35). Pre- and post-operative hip-knee-ankle radiographs were analysed. The knee injury and osteoarthritis outcome score (KOOS), American Knee Society Score, Short Form-36, Euro-Qol (EQ-5D), range of movement (ROM), two minute walk, and timed up and go tests were assessed pre-operatively and at six weeks, three and six months and one year post-operatively. RESULTS: A total of 78% of the kinematically aligned group (28 patients) and 77% of the mechanically aligned group (27 patients) were within 3° of their pre-operative plan. There were no statistically significant differences in the mean KOOS (difference 1.3, 95% confidence interval (CI) -9.4 to 12.1, p = 0.80), EQ-5D (difference 0.8, 95% CI -7.9 to 9.6, p = 0.84), ROM (difference 0.1, 95% CI -6.0 to 6.1, p = 0.99), two minute distance tolerance (difference 20.0, 95% CI -52.8 to 92.8, p = 0.58), or timed up and go (difference 0.78, 95% CI -2.3 to 3.9, p = 0.62) between the groups at one year. CONCLUSION: Kinematically aligned TKAs appear to have comparable short-term results to mechanically aligned TKAs with no significant differences in function one year post-operatively. Further research is required to see if any theoretical long-term functional benefits of kinematic alignment are realised or if there are any potential effects on implant survival. Cite this article: Bone Joint J 2016;98-B:1360-8.

A study investigating short- and medium-term effects on function, bone mineral density and lean tissue mass post-total knee replacement in a Caucasian female post-menopausal population: implications for hip fracture risk.

UNLABELLED: Significant increased hip fracture incidence has been reported in the year following total knee replacement. This study demonstrates that bone and muscle loss is a post-surgical consequence of total knee replacement, alongside poor outcomes in function and activity potentially contributing to reduced quality of life and increased hip fracture risk. INTRODUCTION: A significant increase in hip fracture incidence in the year following total knee replacement (TKR) surgery has been reported. This study investigated function and activity following TKR and the effects of limited mobility on bone and muscle loss and their potential contribution to hip fracture risk. METHODS: Changes in dual-energy X-ray absorptiometry (DXA) (GE Lunar Prodigy, Bedford MA), bone mineral density (BMD) at the neck of femur (NOF), total hip region (TH) and lumbar spine were measured alongside leg lean tissue mass (LLTM) in post-menopausal Caucasian females following TKR (N = 19) compared to controls (N = 43). Lumbar spine trabecular bone scores (TBSs) were calculated. Ipsilateral/contralateral weight bearing, lower limb function, 3-day pedometer readings, pain levels and falls were also recorded. Measurements were obtained at pre-surgery baseline and at 6 weeks, 6 months and 12 months post-surgery. RESULTS: No statistically significant differences were demonstrated between groups at baseline bilaterally in LLTM or BMD at the NOF and TH. Losses in ipsilateral NOF and TH BMD and contralateral LLTM were significantly higher in the TKR group at 6 months. Impairment in function and weight bearing persisted in the TKR group 12 months post-operatively alongside deficits in bilateral muscle mass and ipsilateral NOF and TH BMD. Falls incidence was not significantly higher in the TKR group. CONCLUSIONS: Bone loss at the hip with associated muscle loss is a consequence of TKR that, in addition to poor patient outcomes in function and activity, potentially contributes to increased hip fracture risk in the year following surgery.

The epidemiology of revision total knee and hip arthroplasty in England and Wales: a comparative analysis with projections for the United States. A study using the National Joint Registry dataset.

Total knee arthroplasty (TKA) and total hip arthroplasty (THA) are recognised and proven interventions for patients with advanced arthritis. Studies to date have demonstrated a steady increase in the requirement for primary and revision procedures. Projected estimates made for the United States show that by 2030 the demand for primary TKA will grow by 673% and for revision TKA by 601% from the level in 2005. For THA the projected estimates are 174% and 137% for primary and revision surgery, respectively. The purpose of this study was to see if those predictions were similar for England and Wales using data from the National Joint Registry and the Office of National Statistics. Analysis of data for England and Wales suggest that by 2030, the volume of primary and revision TKAs will have increased by 117% and 332%, respectively between 2012 and 2030. The data for the United States translates to a 306% cumulative rate of increase between 2012 and 2030 for revision surgery, which is similar to our predictions for England and Wales. The predictions from the United States for primary TKA were similar to our upper limit projections. For THA, we predicted an increase of 134% and 31% for primary and revision hip surgery, respectively. Our model has limitations, however, it highlights the economic burden of arthroplasty in the future in England and Wales as a real and unaddressed problem. This will have significant implications for the provision of health care and the management of orthopaedic services in the future.