Aims. Femoral periprosthetic fractures are rising in incidence. Their management is complex and carries a high associated mortality. Unlike native hip fractures, there are no guidelines advising on time to theatre in this group. We aim to determine whether delaying surgical intervention influences morbidity or mortality in femoral periprosthetic fractures. Methods. We identified all periprosthetic fractures around a hip or knee arthroplasty from our prospectively collated database between 2012 and 2021. Patients were categorized into early or delayed intervention based on time from admission to surgery (early = ≤ 36 hours, delayed > 36 hours). Patient demographics, existing implants, Unified Classification System fracture subtype, acute medical issues on admission, preoperative haemoglobin, blood transfusion requirement, and length of hospital stay were identified for all patients. Complication and mortality rates were compared between groups. Results. A total of 365 patients were identified: 140 in the early and 225 in the delayed intervention group. Mortality rate was 4.1% at 30 days and 19.2% at one year. There was some indication that those who had surgery within 36 hours had a higher mortality rate, but this did not reach statistical significance at 30 days (p = 0.078) or one year (p = 0.051). Univariate analysis demonstrated that age, preoperative haemoglobin, acute medical issue on admission, and the presence of postoperative complications influenced 30-day and one-year mortality. Using a multivariate model, age and preoperative haemoglobin were independently predictive factors for one-year mortality (odds ratio (OR) 1.071; p < 0.001 and OR 0.980; p = 0.020). There was no association between timing of surgery and postoperative complications. Postoperative complications were more likely with increasing age (OR 1.032; p = 0.001) and revision arthroplasty compared to internal fixation (OR 0.481; p = 0.001). Conclusion. While early intervention may be preferable to reduce prolonged immobilization, there is no evidence that delaying surgery beyond 36 hours increases mortality or complications in patients with a femoral periprosthetic fracture. Cite this article: Bone Jt Open 2024;5(6):452–456

Accurate evaluation of lower limb coronal alignment is essential for effective pre-operative planning of knee arthroplasty. Weightbearing hip-knee-ankle (HKA) radiographs are considered the gold standard. Mako SmartRobotics uses CT-based navigation to provide intra-operative data on lower limb coronal alignment during robotic assisted knee arthroplasty. This study aimed to compare the correlation between the two methods in assessing coronal plane alignment. Patients undergoing Mako partial (PKA) or total knee arthroplasty (TKA) were identified from our hospital database. The hospital PACS system was used to measure pre-operative coronal plane alignment on HKA radiographs. This data was correlated to the intraoperative deformity assessment during Mako PKA and TKA surgery. 443 consecutive Mako knee arthroplasties were performed between November 2019 and December 2021. Weightbearing HKA radiographs were done in 56% of cases. Data for intraoperative coronal plane alignment was available for 414 patients. 378 knees were aligned in varus, and 36 in valgus. Mean varus deformity was 7.46° (SD 3.89) on HKA vs 7.13° (SD 3.56) on Mako intraoperative assessment, with a moderate correlation (R= 0.50, p<0.0001). Intraoperative varus deformity of 0-4° correlated to HKA measured varus (within 3°) in 60% of cases, compared to 28% for 5-9°, 17% for 10-14°, and in no cases with >15° deformity. Mean valgus deformity was 6.44° (SD 4.68) on HKA vs 4.75° (SD 3.79) for Mako, with poor correlation (R=0.18, p=0.38). In this series, the correlation between weightbearing HKA radiographs and intraoperative alignment assessment using Mako SmartRobotics appears to be poor, with greater deformities having poorer correlation

This study aims to determine satisfaction rates after hip and knee arthroplasty in patients who did not initially respond to PROMs, characteristics of non-responders, and contact preferences to maximise response rates. We performed a prospective cohort study of 709 patients undergoing THA and 737 patients undergoing TKA in a single centre in 2018. EQ-5D health related quality of life score and Oxford Hip/knee scores (OHS/OKS) were completed preoperatively and at 1year postoperatively via post when satisfaction was also assessed. Univariate, multivariate and receiver operator curve analysis were performed. 151/709 (21.2%) hip patients were non-responders, 83 (55.0%) of whom were contactable. 108/737 (14.6%) knee patients were non-responders, 91 (84.3%) of whom were contactable. There was no difference in satisfaction after arthroplasty between initial non-responders and responders for hips (74/81 vs 476/516, p=0.847) or knees (81/93 vs 470/561, p=0.480). Initial and persistent non-response was associated with younger age, higher BMIs and significantly worse preoperative PROMS for both hip and knee patients (p=0.05). Multivariate analysis demonstrated that younger age, higher BMI and poorer pre-operative OHS were independently associated with persistent non-response to hip PROMs (p<0.05). For the entire cohort (n=1352) patients <67 years were less likely to respond to postal PROMs with OR 0.63 (0.558 to 0.711). Using a threshold of >66.4 years predicted a preference for contact by post with 65.4% sensitivity and 68.1% specificity (AUC 0.723 (0.647-0.799 95%CI, p<0.001)). Most initial non-responders were ultimately contactable with effort. Satisfaction rates were not inferior in patients who did not initially respond to PROMs

One potential approach to addressing the current hip and knee arthroplasty backlog is via adoption of surgical prioritisation methods, such as use of pre-operative health related quality of life (HRQOL) assessment. We set out to determine whether dichotomization using a previously identified bimodal EuroQol Five-Dimension (EQ-5D) distribution could be used to triage waiting lists. 516 patients had data collected regarding demographics, perioperative variables and patient reported outcome measures (pre-operative & 1-year post-operative EQ-5D-3L and Oxford Hip and Knee Scores (OHS/OKS). Patients were split into two equal groups based on pre-operative EQ-5D Time Trade-Off (TTO) scores and compared (Group1 [worse HRQOL] = −0.239 to 0.487; Group2 [better HRQOL] = 0.516 to 1 (best)). The EQ5D TTO is a widely used and validated HRQOL measure that generates single values for different combinations of health-states based upon how individuals compare x years of healthy living to x years of illness. We identified that those in Group1 had significantly greater improvement in post-operative EQ-5D TTO scores compared to Group2 (Median 0.67vs.0.19; p<0.0001 respectively), as well as greater improvement in OHS/OKS (Mean 22.4vs16.4; p<0.0001 respectively). Those in Group2 were significantly less likely to achieve EQ-5D MCID attainment (OR 0.13, 95%CI 0.07–0.23; p<0.0001) with a trend towards lower OHS/OKS MCID attainment (OR 0.66, 95%CI 0.37–1.19; p=0.168). There was no statistically significant difference in adverse events. These finding suggest that a pre-operative EQ-5D cut-off of ≤0.487 for hip and knee arthroplasty prioritisation may help to maximise clinical utility and cost-effectiveness in a limited resource setting post COVID-19

Introduction. In contrast to knee arthroplasty, there is no national register on high tibial osteotomy (HTO) in Sweden. The knowledge of the outcome of HTO as a treatment alternative for knee osteoarthritis (OA) is insufficient. The rate of revision to knee arthroplasty after HTO at 10 years has been reported to vary between 8 and 49%. The aim of the study was to evaluate the outcome of HTO performed in Sweden 1998–2007, expressed by rate of revision to knee arthroplasty. Patienter och Material: 3 196 HTO (69% men) 30 years or older operated on for knee OA in Sweden 1998–2007 were identified through the in- and out-patient care registers from the Swedish National Board of Health and Welfare. Side, left/right, that was operated, diagnosis and indication for surgery were verified through surgical records. Conversions of HTO to knee arthroplasty before 2010 were identified through the Swedish Knee Arthroplasty Register (SKAR). In about 10% of the cases it was unknown what side the HTO had been performed on and thus if the arthroplasty had been on the same knee. In these cases we assumed a worst case scenario of all having been on the same side as the HTO. A 10-year survival analysis was performed using revision to an arthroplasty as the end point. Result. The mean age was 52 years (range 30- 80) with 97% of the patients younger than 65 years. The cumulative revision rate (CRR) at 10 year was 29.4% (95% CI 27.2–32.9) after adjusting for age and gender. The risk of revision increased by increasing age and the risk of revision after adjusting for age was significantly higher in women than men RR 1.30 (95% CI 1.11–4.54). Most of the HTO's were performed by open wedge osteotomy using external fixation. The risk of revision was higher for closed wedge osteotomies when comparing the closed and open wedge methods RR1.29 (95% CI 1.08–1.55). Conclusion. 70% of the high tibial osteotomies performed in Sweden 1998–2007 had not been converted to a knee replacement, using the 10 year cumulative revision rate. If it is considering beneficial to have no implant in the knee, high tibial osteotomy may be considered as an alternative to TKA in the younger and physically active patients

NICE guidelines state that patients undergoing hip or knee arthroplasty should start as an in-patient and then continue pharmacological VTE prophylaxis for 28–35 days. Retrospective review of all elective hip and knee arthroplasties during one calendar month gave a baseline measurement of how many patients had VTE prophylaxis prescribed on their discharge summary. A new, electronically completed, bespoke Trauma and Orthopaedic discharge summary was created with a discreet area clearly marked for VTE prophylaxis, to serve as a reminder to prescribe it. In March 2012, 93 patients underwent hip/knee arthroplasty. 76% (71/93) were prescribed VTE prophylaxis to take home, there was no clinical reason explaining the failure to prescribe prophylaxis in the remaining 24%. In July 2013, after implementation of the change, 117 patients underwent hip/knee arthroplasty. 99% (116/117) were prescribed VTE prophylaxis to take home. Repeat audit in October 2013 showed that 103 patients underwent hip/knee arthroplasty and 100% were prescribed VTE prophylaxis. A simple but clear change to paperwork, brought about a rapid and seemingly lasting change in the prescription of out-patient VTE prophylaxis. The improvement was seen before and after a change of the Junior Doctor workforce suggesting the change in documentation was the main influencing factor

Clostridium difficile is associated with a range of gastrointestinal disorders ranging from diarrhoea to toxic megacolon. Alteration of the normal gut flora by antibiotics is a key predisposing factor. Although antibiotic prophylaxis is routinely administered during joint replacement surgery, there has been controversy about both type and duration of prophylaxis. The primary aim of this study was to determine the incidence of C. diff associated disease (CDAD) following hip and knee replacement and to investigate potential risk factors. A laboratory database was interrogated to identify patients developing CDAD after hip or knee replacement from January 2006 to December 2008. A database of arthroplasty patients was used to identify a control group of patients without CDAD to compare the effects of prescription of antibiotics for reasons other prophylaxis of deep infection, comorbidity and the use of gastroprotective agents. Eight patients developed CDAD. There were 1.7 cases of CDAD per 1000 joint replacements. Patients developing CDAD were more likely to have been prescribed additional antibiotics (p=0.047). There were no differences in the use of gastroprotective agents (p=0.703). A trial of a new prophylaxis regime would require 43,198 patients in each arm to show a reduction to 1 case per 1000 procedures. Cefuroxime based antibiotic prophylaxis is safe in patients undergoing elective joint replacement. Extremely large studies would be required to show marginal clinical benefits of new regimes. One prophylaxis policy will not suit all orthopaedic patient groups or procedures

Many psychological factors have been associated with function after joint replacement. Personality is a stable pattern of responses to external conditions and stimuli. The aim of this study was to investigate the relationship between personality, joint function, and general physical in patients undergoing total hip (THR) and knee replacement (TKR). We undertook a prospective cohort study of 184 patients undergoing THA and 205 undergoing TKA. Personality was assesed using the Eysneck Personality Questionaire, brief version (EPQ-BV). Physical health was measured using the EuroQol (EQ-5D). Joint function was measured using the relevant Oxford Score. Outcomes were assessed at six months. Multivariable models were constructed. The stable introvert personality was most common. Unstable introverts had poorer pre-operative function with hip arthrosis, but not knee arthrosis. Personality was not directly associated with post-operative function – the only independent predictors were pre-operative function (p=0.002) and comorbidity (p<0.001). While satisfaction after TKR was associated with personality (p=0.026), there was no association after THR (p=0.453). The poorest satisfaction was in those with the unstable introvert personality type. Personality was a predictor of preoperative status. It did not have a direct association with postoperative status, but may have as preoperative function was the main predictor of postoperative function, personality may have had an indirect effect. Personality was also a predictor of satisfaction after TKR. This suggests that predicting satisfaction after knee replacement is more complex. Therefore certain patient may benefit from a tailored preoperative education to explore and manage expectations

Revision Total Knee Arthroplasty (rTKA) is predicted to increase by more than 600% between 2005 and 2030. The survivorship of primary TKA has been extensively investigated, however more granular information on the risks of rTKA is needed. The aim of the study was to investigate the incidence of re-revision TKA, with explanatory variables of time from primary to revision, and indication (aseptic vs septic). Secondary aim was to investigate mortality.

This is an analysis of the Scottish Arthroplasty Project data set, a national audit prospectively recording data on all joint replacements performed in Scotland. The period from 2000 to 2019 was studied.

4723 patients underwent revision TKA. The relationship between time from primary to revision TKA and 2nd revision was significant (p<0.001), with increasing time lowering probability of re-revision (OR 0.99 95% CI 0.987 to 0.993). There was no significant association in time to first revision on time from 1st revision to re-revision (p>0.05). Overall mortality for all patients was 32% at 10 years (95% CI 31-34), Time from primary TKA to revision TKA had a significant effect on mortality: p=0.004 OR 1.03 (1.01-1.05). Septic revisions had a reduced mortality compared to aseptic, OR 0.95 (0.71-1.25) however this was not significant (p=0.69).

This is the first study to demonstrate time from primary TKA to revision TKA having a significant effect on probability of re-revision TKA. Furthermore the study suggests mortality is increased with increasing time from primary procedure to revision, however decreased if the indication is septic rather than aseptic.

The objective of this study was to compare differences in alignment following robotic arm-assisted bi-unicompartmental knee arthroplasty (Bi-UKA) and conventional total knee arthroplasty (TKA). This was a prospective, randomised controlled trial of 70 patients. 39 TKAs were implanted manually, as per standard protocol at our institution, and 31 Bi-UKA patients simultaneously received fixed-bearing medial and lateral UKAs, implanted using robotic arm-assistance. Preoperative and 3-month postoperative CT scans were analysed to determine hip knee ankle angle (HKAA), medial distal femoral angle (MDFA), and medial proximal tibial angle (MPTA). Analysis was repeated for 10 patients by a second rater to validate measurement reliability by calculating the intra-class correlation coefficient (ICC). Mean change in HKAA towards neutral was 2.7° in TKA patients and 2.3° in Bi-UKA patients (P=0.6). Mean change in MDFA was 2.5° for TKA and 1.0° for Bi-UKA (P<0.01). Mean change in MPTA was 3.7° for TKA and 0.8° for Bi-UKA (P<0.01). Mean postoperative MDFA and MPTA for TKAs were 89.8° and 89.6° respectively, indicating orientation of femoral and tibial components perpendicular to the mechanical axis. Mean postoperative MDFA and MPTA for Bi-UKAs were 91.0° and 86.9° respectively, indicating a more oblique joint line orientation. Inter-rater agreement was excellent (ICC>0.99). Early functional activities, according to the new Knee Society Scoring System, favoured Bi-UKAs (P<0.05). Robotic arm-assisted, cruciate-sparing Bi-UKA better maintains the natural anatomy of the knee in the coronal plane and may therefore preserve normal joint kinematics, compared to a mechanically aligned TKA. This has been achieved without significantly altering overall HKAA

The aim was to perform a cost-utility analysis of total joint replacement in the current environment. Arthritis is a disabling condition that leads to long-term deterioration in quality of life. Total joint replacement, despite being one of the greatest advances in medicine in the modern era, has come under recent scrutiny. The National Health Service (NHS) has competing demands and resource allocation is challenging in times of economic restraint. Patients undergoing total hip (n=348) and knee arthroplasty (n=323), from January to July 2010, were entered into a prospective arthroplasty database. A health utility score was derived from the Euroqol (EQ-5D) score preoperatively, and at one year, and was combined with individual life expectancy to derive the Quality-Adujusted-Life-Years (QALYs) gained. Predicted need for revision surgery was Incorporated in the model. The 2011–12 Scottish Tariff was used. Two-way analysis of variance was used to compare QALYs gained between procedures, while controlling for baseline differences. The number of QALYs gained was higher in THR versus TKR (6.53 vs 4.04 years, p<0.001). The cost per QALY for THR was £1371 (95% CI £1194 to £1614) compared with £2101 (£1762 to £2620) for TKR. Predictors of an increase in QALYs gained were poorer health prior to surgery (p<0.001) and younger age (p<0.001). General health (EQ-5D VAS) showed greater improvement in THR versus TKR (p<0.001). This study provides up to date cost-effectiveness data for total joint replacement. THR and TKR are both extremely clinically and cost-effective interventions, with costs that compare favourably with other medical interventions (e.g. laparoscopic hernia repair vs open: £55,548 per QALY; CHD primary prevention with statins: £21,000)

Paget's disease of bone (PDB) is the second most common metabolic bone disease. Osteoarthritis (OA) affects one-third of patients with PDB. The incidence of THR (total hip replacement) and TKR (total knee replacement) is 3.1- and 1.7-fold higher in PDB patients compared to non-affected age-matched controls. No large studies or joint registry reports exist describing the outcomes following THR or TKR in patients with PDB. The objectives of this study were to investigate the outcomes following THR and TKR in patients with PDB using national joint registry data. 144 THR and 43 TKR were identified using the Scottish Arthroplasty Project from 1996–2013. For THR, the most common early post-operative surgical complications were haematoma formation (1.4%), and surgical site infection (1.4%). The absolute incidence during follow-up of dislocation was 2.8%, and revision hip arthroplasty was performed in 2.8% of cases. Implant survival of the primary prosthesis was 96.3% (CI: 92.8 – 99.8) at 10-years, and patient survival was 50.0% (39.6 – 60.4) at 10-years. For TKR, the most common early post-operative surgical complication was surgical site infection (2.3%). The absolute incidence during follow-up of revision knee arthroplasty was 4.7%. On survival analysis, implant survival of the primary prosthesis was 94.5% (CI: 87.1 – 100) at 10-years, and patient survival was 38.3% (16.7 – 59.9) at 10-years. This is the largest reported series of outcomes following primary THR and TKR in patients with PDB. PDB patients are not at increased risk of surgical complications following primary THR or TKR compared to non-PDB patients

The primary aim was to assess whether patients waiting 6-months or more for a total hip (THA) or knee (KA) arthroplasty had a deterioration in their health-related quality of life (HRQoL). Secondary aims were to assess change in level of frailty and the number living in a state worse than death (WTD).

Eight-six patients waiting for a primary TKA or KA for more than 6-months were selected at random from waiting lists in three centres. Patient demographics, waiting time, EuroQol 5-dimension (EQ-5D) and visual analogue scores (EQ-VAS), Rockwood clinical frailty score (CFS) and SF-36 subjective change in HRQoL were recorded at the time of and for a timepoint 6-months prior to assessment. The study was powered to the EQ-5D (primary measure of HRQoL).

There were 40 male and 46 female patients with a mean age of 68 (33 to 91) years; 65 patients were awaiting a THA and 21 a TKA. The mean waiting time was 372 (226 to 749) days. The EQ-5D index deteriorated by 0.222 (95%CI 0.164 to 0.280, p<0.001). The EQ-VAS also deteriorated by 10.8 (95%CI 7.5 to 14.0, p<0.001). CFS progressed from a median of 3 to 4 (p<0.001). The number of patients WTD increased from seven to 22 (p<0.001). Thirty-one(36%) patients felt their HRQoL was much worse and 28 (33%) felt it was somewhat worse.

Patients waiting more than 6-months had a clinically significant deterioration in their HRQoL and demonstrated increasing level of frailty with more than a quarter living in a health state WTD.

SIGN guidelines advise the use of flucloxacillin and gentamicin instead of cefuroxime as antibiotic prophylaxis for elective hip and knee arthroplasty. It is our impression that this change in practice has been associated with an increased risk of acute kidney injury (AKI). During a twelve month period we examined the incidence of AKI sequentially in four groups of patients: cefuroxime prophylaxis (n = 46); high dose flucloxacillin (5-8g) with single shot gentamicin (n = 50); low dose flucloxacillin (1-4 g) with single shot gentamicin (n = 45); and finally cefuroxime again (n = 52). There were no statistically significant differences by chi-square tests for age, gender, operation (hip or knee), ASA, anaesthesia, baseline serum creatinine, hypertension, diabetes or pre-operative medication. The proportion of patients in each antibiotic group with any form of AKI by RIFLE criteria was: cefuroxime group 1 (9%), high dose flucloxacillin (52%), low dose flucloxacillin (22%), cefuroxime 2 (14%) (p < 0.0001 by chi-square test). Odds ratios (OR) for AKI derived from a multivariate logistic regression model and assigning an OR of 1 to cefuroxime group 1 was: high dose flucloxacillin 14.5 (95% CI, 4.2, 50.2); low dose flucloxacillin 3.0 (0.8-10.9) and cefuroxime group 2 1.9 (0.5, 7.4). Three patients in the high dose flucloxacillin group required temporary haemodialysis. We have shown a strong association between high dose prophylactic flucloxacillin and subsequent development of AKI. We have no reason to believe that this was confounded by any of the co-variates we measured

Tibial plateau fractures are common intraarticular fractures. The principal long-term complication is post-traumatic osteoarthritis (PTOA) with the usual salvage procedure being total knee arthroplasty (TKA). Our aim was to define the incidence of PTOA requiring TKA following tibial plateau fractures and identify the risk factors.

We looked at all tibial plateau fractures between 1995 and 2008. There were 888 tibial plateau fractures. 23% were Schatzker I, 25% II, 14% III, 22% IV, 8% V and 8% VI. To date 25 have undergone TKA (2.8%). The mean age of patients at time of fracture was 56 in the overall cohort and 65 in those requiring TKA; this was statistically significant (p=0.04). 4% of females with tibial plateau fractures required TKA in comparison to 2% of males. The Schatzker I fractures were the least likely to require TKA at 1% with the most likely requiring arthroplasty surgery being type III at 6%. Only 1% of the patients treated non-operatively later underwent TKA

The overall incidence of TKA after tibial plateau fractures was 3%. For displaced fractures requiring internal fixation this rose to 4%. Risk factors were increasing age, split depression fractures and female gender. Although tibial plateau fractures are commonly associated with degenerative radiographic changes, we concluded that the incidence of symptomatic OA severe enough to require TKA is low.

Nerve damage is a complication of THA and TKA procedures. The incidence of subclinical nerve injury following arthroplasty is unknown. The aim was to determine the prevalence of asymptomatic nerve deficits in an arthroplasty population group, and the incidence of post-operative changes in nerve function. A Secondary aim was to identify the nature of any deficits. And the association between nerve deficits and history of backache.

A non-randomised prospective series of patients undergoing lower limb arthroplasty for osteoarthritis were studied at a single hospital. The peroneal nerve was investigated using nerve conduction in forty patients. Twenty patients had upper limb testing to differentiate between a polyneuropathy or isolated lower limb neuropathy.

Nerve function deficits were detected in the peroneal nerve in fifteen patients pre-operatively and fifteen post-operatively, of those twelve had A waves detected suggestive of a generalised neuropathy. Ten patients who had upper limb testing had a conduction defect (five had asymptomatic Carpal tunnel). There was a positive correlation between presence of post-operative deficit and age(r=0.389, p=0.013). A negative correlation was found for presence of post-operative A waves and BMI(r=−0.370, p=0.019).

The prevalence of pre-operative subclinical peroneal neuropathy is much higher than expected in this group (37.5%) of arthroplasty patients. There is a strong correlation between presence of post-operative conduction abnormalities and age. There is no relationship between peripheral neuropathy and history of backache or residual post-operative deficit.

Introduction

We compared standard NexGen Cruciate substituting-flex prosthesis with gender-specific NexGen Cruciate substituting flex prosthesis in patients undergoing bilateral total knee arthroplasty with regard to Coverage of the bone by femoral component, Clinical outcome, Radiographic outcome, Survival and complication rates, with special emphasis on patellofemoral complications.

Methicillin Resistant Staphylococcus Aureus (MRSA) screening has reduced rates of MRSA infection in primary total hip (THR) and total knee (TKR) replacements. There are reports of increasing methicillin resistance (MR) in Coagulase Negative Staphylococci (CNS) causing arthroplasty infections. We examined microbiological results of all 2-stage THR/TKR revisions in Tayside from 2001–2010.

72 revisions in 67 patients were included; 30 THRs and 42 TKRs. Mean ages at revision were 89 and 72 years respectively. Male: female ratio 1.4:1.2-year survivorship for all endpoints: 96% in THRs and 88% in TKRs. 5-year survival: 83% and 84% respectively.

The most common organisms were SA (30%) and CNS (29%). Antibiotic resistance was more common amongst CNS. 72% of CNS were resistant to Methicillin versus 20% of SA. 80% of CNS were resistant to Gentamicin OR Methicillin versus 20% of SA. 32% (8/72 cases or 11% overall) of CNS were resistant to BOTH Gentamicin AND Methicillin, the primary arthroplasty antibiotic prophylaxis in our region, versus 4% of SA.

Harris Hip Scores and Knee Society Scores were lower post primary, prior to symptoms of infection in patients who had MR organisms cultured compared with those who had methicillin sensitive organisms. One-year post revision both groups recovered to similar scores.

Our data suggest MR-CNS cause significantly more arthroplasty infections than MRSA. Patients developing MR infections tend to have poorer post-primary knee and hip scores before symptoms of infection fully develop. 32% of CNS causing arthroplasty infections in our region are resistant to current routine primary antibiotic prophylaxis.

Two stage revision for infection is considered the gold standard with a success rate of 80–90%. Overall functional outcomes of these patients are commonly overlooked. There is a trend towards single stage revision to improve functional outcomes.

We examined the functional scores of 2 stage revision for total hip arthroplasty (THR) and total knee arthroplasty (TKR). 72 revisions were identified over 9 years: 30 THR and 42 TKR. Two year survivorship was 96% in THR revision and 88% TKR revision. Five year survival was 83% and 84% respectively. 50 patients (without recurrence of infection) had recorded functional scores at a minimum of 1 year.

The mean Harris-hip score (HHS) of THR was 75 (21 patients) prior to developing symptoms of infection. Once infected, the mean score fell to 46. At 1 year post revision it returned to 77. At 3 years HHS of 78 (12 patients) and at 5 yrs 62 (3 patients).

The mean knee society score (KSS) of TKR was 66 (29 patients) prior to developing symptoms of infection. Once infected, the mean score fell to 34. At 1 year post revision it returned to 73. At 3 years KSS of 76 (16 patients) and at 5 years 62 (10 patients).

We conclude that functional scores of staged revisions of infected THR and TKR return to pre-morbid levels within a year of completing the second stage. Although single stage revision may have a quicker return to function, by 1 year, staged revision has comparable results.

Introduction

Minimally invasive implanted unicompartmental knee arthroplasty (UKA) leads to excellent functional results. Due to the reduced intraoperative visibility it is difficult to remove extruded bone cement particles, as well as bone particles generated through the sawing. These loose third body particles are frequently found in minimally invasive implanted UKA.

The aim of this study was to analyse the influence of bone and cement particles on the wear rate of unicompartmental knee prostheses in vitro.