Early radiological outcomes of a fully porous bridging collar in lower-limb endoprosthetic reconstructions: a case-matched retrospective series to assess osseointegration.

BACKGROUND: Limb-salvage surgery involving the utilization of endoprosthetic replacements is commonly employed following segmental bone resection for primary and secondary bone tumors. This study aimed to evaluate whether a fully porous bridging collar promotes early osseous integration in endoprosthetic replacements. METHODS: We undertook a retrospective review of all lower-limb endoprostheses utilizing a fully porous endosteal bridging collar design. We matched this cohort with a conventional extra-osteal non-porous fully hydroxyapatite-coated grooved collar cohort according to surgical indication, implant type, resection length, age, and follow-up time. At 6, 12, and 24 months post-implantation, radiographs were assessed for the number of cortices with or without osseointegration on orthogonal radiographs. Each radiograph was scored on a scale of -4 to + 4 for the number of cortices bridging the ongrowth between the bone and the collar of the prosthesis. Implant survival was estimated using the Kaplan-Meier method, and the mean number of osseointegrated cortices at each time point between the collar designs was compared using a paired t-test. RESULTS: Ninety patients were retrospectively identified and analyzed. After exclusion, 40 patients with porous bridging collars matched with 40 patients with conventional extra-osteal non-porous collars were included in the study (n = 80). The mean age was 63.4 years (range 16-91 years); there were 37 males and 43 females. The groups showed no difference in implant survival (P = 0.54). The mean number of cortices with radiographic ongrowth for the porous bridging collar and non-porous collar groups was 2.1 and 0.3, respectively, at 6-month (P < 0.0001), 2.4 and 0.5, respectively, at 12-month (P = 0.044), and 3.2 and -0.2, respectively, at 24-month (P = 0.18) radiological follow-up. CONCLUSION: These findings indicate that fully porous bridging collars increased the number of cortices, with evidence of bone ongrowth between 6 and 24 months post-implantation. By contrast, extra-osteal collars exhibited reduced evidence of ongrowth between 6 and 24 months post-implantation. In the medium term, the use of a fully porous bridging collar may translate to a reduced incidence of aseptic loosening.

Does a novel bridging collar in endoprosthetic replacement optimise the mechanical environment for osseointegration? A finite element study.

Introduction: Limb-salvage surgery using endoprosthetic replacements (EPRs) is frequently used to reconstruct segmental bone defects, but the reconstruction longevity is still a major concern. In EPRs, the stem-collar junction is the most critical region for bone resorption. We hypothesised that an in-lay collar would be more likely to promote bone ongrowth in Proximal Femur Reconstruction (PFR), and we tested this hypothesis through validated Finite Element (FE) analyses simulating the maximum load during walking. Methods: We simulated three different femur reconstruction lengths (proximal, mid-diaphyseal, and distal). For each reconstruction length one in-lay and one traditional on-lay collar model was built and compared. All reconstructions were virtually implanted in a population-average femur. Personalised Finite Element models were built from Computed Tomography for the intact case and for all reconstruction cases, including contact interfaces where appropriate. We compared the mechanical environment in the in-lay and on-lay collar configurations, through metrics of reconstruction safety, osseointegration potential, and risk of long-term bone resorption due to stress-shielding. Results: In all models, differences with respect to intact conditions were localized at the inner bone-implant interface, being more marked in the collar-bone interface. In proximal and mid-diaphyseal reconstructions, the in-lay configuration doubled the area in contact at the bone-collar interface with respect to the on-lay configuration, showed less critical values and trends of contact micromotions, and consistently showed higher (roughly double) volume percentages of predicted bone apposition and reduced (up to one-third) percentages of predicted bone resorption. In the most distal reconstruction, results for the in-lay and on-lay configurations were generally similar and showed overall less favourable maps of the bone remodelling tendency. Discussion: In summary, the models corroborate the hypothesis that an in-lay collar, by realising a more uniform load transfer into the bone with a more physiological pattern, creates an advantageous mechanical environment at the bone-collar interface, compared to an on-lay design. Therefore, it could significantly increase the survivorship of endo-prosthetic replacements.

Key performance and training parameters in primary total hip arthroplasty - an expert consensus using the Delphi technique.

AIMS: Primary total hip arthroplasty (THA) is a commonly performed and successful operation which orthopaedic trainees must demonstrate competence in prior to completion of surgical training. An assessment of agreement between surgical trainers regarding the critical steps of a primary THA has never been undertaken. The aim of this study was to define and rank the key steps of a primary THA regards ease of teaching and their importance in achieving the best patient outcome. MATERIALS AND METHODS: The Delphi technique with 3 iterative rounds was used to establish expert group consensus. The benchmark for consensus was set at an 80% agreement in any category for each step of a THR. The intra-class correlation coefficient (ICC) was used to report on the inter- and intra-rater reliabilities between and within participants responses respectively in rounds 2 and 3. RESULTS: 50 consultant orthopaedic hip surgeons completed round 2, and 28 completed round 3. Overall, 27 steps (54 parameters) were identified, with 16 parameters achieving consensus agreement for their impact on patient outcome, and 17 for ease of teaching. The inter-rater ICC for patient outcome parameters was 0.89 and 0.92 in rounds 2 and 3 respectively while for teaching parameters it was 0.82 and 0.73. 50% of surgeons agreed that acetabular reaming, assessing and accurately restoring leg length, and acetabular cup anteversion were the 3 most difficult steps to teach trainees, while 90% agreed these 3 steps were substantially important to patient outcome. Another 5 steps achieved consensus for their substantial impact on patient outcome but failed to achieve consensus for ease of teaching. CONCLUSIONS: The results of this expert consensus have produced a rank-order list of the key steps in primary THA, which may be used for orthopaedic curriculum development and guiding focused improvements for surgical training in primary THR including simulation.

Validating the accuracy of a novel virtual reality platform for determining implant orientation in simulated primary total hip replacement.

Introduction: Accurate acetabular cup and femoral stem component orientation are critical for optimising patient outcomes, reducing complications and increasing component longevity following total hip replacement (THR). This study aimed to determine the accuracy of a novel virtual reality (VR) platform in assessing component orientation in a simulated THR model. Methods: The VR platform (HTC Vive Pro® system hardware) was compared against the validated Vicon® optical motion capture (MoCap) system. An acetabular cup and femoral stem were manually implanted across a range of orientations into pelvic and femur sawbones, respectively. Simultaneous readings of the acetabular cup operative anteversion (OA) and inclination (OI) and femoral stem alignment (FSA) and neck anteversion (FNA) were obtained from the VR and MoCap systems. Statistical analysis was performed using Pearson product-moment correlation coefficient (PPMCC) (Pearson's r) and linear regression (R2). Results: A total of 55 readings were obtained for the acetabular cup and 68 for the femoral stem model. The mean average differences in OA, OI, FSA and FNA between the systems were 3.44°, -0.01°, 0.01° and -0.04°, respectively. Strong positive correlations were demonstrated between both systems in OA, OI, FSA and FNA, with Pearson's r = 0.92, 0.94, 0.99 and 0.99, and adjusted R2 = 0.82, 0.9, 0.98 and 0.98, respectively. Conclusion: The novel VR platform is highly accurate and reliable in determining both acetabular cup and femoral stem component orientations in simulated THR models. This adaptable and cost-effective digital tracking platform may be modified for use in a range of simulated surgical training and educational purposes, particularly in orthopaedic surgery.

Utility of pre-operative haemoglobin concentration to guide peri-operative blood tests for hip and knee arthroplasty: A decision curve analysis.

OBJECTIVE: Assess the prognostic value of pre-operative haemoglobin concentration (Hb) for identifying patients who develop severe post-operative anaemia or require blood transfusion following primary total hip or knee, or unicompartmental knee arthroplasty (THA, TKA, UKA). BACKGROUND: Pre-operative group and save (G&S), and post-operative Hb measurement may be unnecessary for many patients undergoing hip and knee arthroplasty provided individuals at greatest risk of severe post-operative anaemia can be identified. METHODS AND MATERIALS: Patients undergoing THA, TKA, or UKA between 2011 and 2018 were included. Outcomes were post-operative Hb below 70 and 80 g/L, and peri-operative blood transfusion. Logistic regression assessed the association between pre-operative Hb and each outcome. Decision curve analysis compared strategies for selecting patients for G&S and post-operative Hb measurement. RESULTS: 10 015 THA, TKA and UKA procedures were performed in 8582 patients. The incidence of blood transfusion (4.5%) decreased during the study. Using procedure specific Hb thresholds to select patients for pre-operative G&S and post-operative Hb testing had a greater net benefit than selecting all patients, no patients, or patients with pre-operative anaemia. CONCLUSIONS: Pre-operative G&S and post-operative Hb measurement may not be indicated for UKA or TKA when adopting restrictive transfusion thresholds, provided clinicians accept a 0.1% risk of patients developing severe undiagnosed post-operative anaemia (Hb < 70 g/L). The decision to perform these blood tests for THA patients should be based on local institutional data and selection of acceptable risk thresholds.

A guide to debridement, antibiotics, and implant retention.

Debridement, antibiotics, and implant retention (DAIR) is an alternative management strategy for the treatment of periprosthetic joint infection (PJI). While infection eradication rates are lower with DAIR, the benefits including decreased morbidity, improved functional outcomes, and decreased cost may justify the risks when considering this form of treatment compared to traditional one or two stage exchange arthroplasty. Implant longevity in the setting of a successful DAIR is similar to matched patients who have not experienced a PJI. An experienced arthroplasty surgeon well versed in extensile exposure should perform the DAIR. This procedure should not be viewed as a simple "washout." While PJI may be considered a surgical urgency, DAIR can be performed on a planned list if it allows for appropriate staffing and implants for the procedure. Arthroscopic irrigation may be performed for a patient in extremis but it should not be viewed as a definitive procedure to address PJI. Keys to a successful DAIR include accurate tissue sampling to determine the infective organism, meticulous, radical debridement, and exchange of modular components if possible. A multidisciplinary team (MDT) including an infectious disease specialist should be involved prior to surgery in order to guide appropriate antimicrobial therapy throughout the patient's course of treatment. In the article below we present our indications, considerations, and technique for performing a DAIR for PJI for hip and knee arthroplasty.

The Joint-Specific BACH classification: A predictor of outcome in prosthetic joint infection.

BACKGROUND: There is currently no commonly accepted method of stratifying complexity of prosthetic joint infection (PJI). This study assesses a new classification, the Joint-Specific, Bone involvement, Anti-microbial options, Coverage of the soft tissues, Host status (JS-BACH) classification, for predicting clinical and patient reported outcomes in PJI. METHODS: Patients who received surgery for PJI at two centres in the UK between 2010 and 2015 were classified using JS-BACH as 'uncomplicated', 'complex' or 'limited treatment options'. Patient reported outcomes were recorded at 365-days following the index operation and included the EuroQol EQ-5D-3L index score and the EQ-visual analogue score (VAS). Clinical outcome data were obtained from the most recent follow-up appointment. FINDINGS: 220 patients met the inclusion criteria. At 365-days following the index operation, patients with 'uncomplicated' PJI reported similar EQ-index scores (0.730, SD:0.326) and EQ-VAS (79.4, SD:20.9) compared to the age-matched population. Scores for 'uncomplicated' PJI were significantly higher than patients classified as having 'complex' (EQ-index:0.515 SD:0.323, p = 0.012; EQ-VAS:68.4 SD:19.4, p = 0.042) and 'limited treatment options' PJI (EQ-index:0.333 SD:0.383, p < 0.001; EQ-VAS:60.2, SD:23.1, p = 0.005). The median time to final follow-up was 4.7 years (inter-quartile range 2.7-6.7 years) where there were 74 cases (33.6%) of confirmed recurrence. Using death as a competing risk, the Cox proportional-hazards ratio of recurrence for 'complex' versus 'uncomplicated' PJI was 23.7 (95% CI:3.23-174.0, p = 0.002) and having 'limited options' verses 'uncomplicated' PJI was 57.7 (95% CI:7.66-433.9, p < 0.001). INTERPRETATION: The JS-BACH classification can help predict likelihood of recurrence and quality of life following surgery for PJI. This will aid clinicians in sharing prognostic information with patients and help guide referral for specialist management of PJI.

Risk factors influencing fracture characteristics in postoperative periprosthetic femoral fractures around cemented stems in total hip arthroplasty : a multicentre observational cohort study on 584 fractures.

AIMS: This study evaluates risk factors influencing fracture characteristics for postoperative periprosthetic femoral fractures (PFFs) around cemented stems in total hip arthroplasty. METHODS: Data were collected for PFF patients admitted to eight UK centres between 25 May 2006 and 1 March 2020. Radiographs were assessed for Unified Classification System (UCS) grade and AO/OTA type. Statistical comparisons investigated relationships by age, gender, and stem fixation philosophy (polished taper-slip (PTS) vs composite beam (CB)). The effect of multiple variables was estimated using multinomial logistic regression to estimate odds ratios (ORs) with 95% confidence intervals (CIs). Surgical treatment (revision vs fixation) was compared by UCS grade and AO/OTA type. RESULTS: A total of 584 cases were included. Median age was 79.1 years (interquartile range 72.0 to 86.0), 312 (53.6%) patients were female, and 495 (85.1%) stems were PTS. The commonest UCS grade was type B1 (278, 47.6%). The most common AO/OTA type was spiral (352, 60.3%). Metaphyseal split fractures occurred only with PTS stems with an incidence of 10.1%. Male sex 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 = 0.027) compared to PTS stems. Both UCS grade and AO/OTA type differed significantly (p < 0.001 and p = 0.001, respectively) between the revision and fixation groups but a similar proportion of B1 fractures underwent revision compared to fixation (45.3% vs 50.6%). CONCLUSION: 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 have higher odds of bending type fractures (transverse and wedge) compared to PTS stems. There is considerable variation in practice when treating B1 fractures around cemented stems. Cite this article: Bone Jt Open 2021;2(7):466-475.

Primary stability of a proximally coated and tapered stem.

AIMS: The aim of this prospective cohort study was to evaluate the early migration of the TriFit cementless proximally coated tapered femoral stem using radiostereometric analysis (RSA). METHODS: A total of 21 patients (eight men and 13 women) undergoing primary total hip arthroplasty (THA) for osteoarthritis of the hip were recruited in this study and followed up for two years. Two patients were lost to follow-up. All patients received a TriFit stem and Trinity Cup with a vitamin E-infused highly cross-linked ultra-high molecular weight polyethylene liner. Radiographs for RSA were taken postoperatively and then at three, 12, and 24 months. Oxford Hip Score (OHS), EuroQol five-dimension questionnaire (EQ-5D), and adverse events were reported. RESULTS: At two years, the mean subsidence of the head and tip for the TriFit stem was 0.38 mm (SD 0.32) and 0.52 mm (SD 0.36), respectively. The total migration of the head and tip was 0.55 mm (SD 0.32) and 0.71 mm (SD 0.38), respectively. There were no statistically significant differences between the three to 12 months' migration (p = 0.105) and 12 to 24 months' migration (p = 0.694). The OHS and EQ-5D showed significant improvements at two years. CONCLUSION: The results of this study suggest that the TriFit femoral stem achieves initial stability and is likely to be stable in the mid and long term. A long-term outcome study is required to assess late mechanisms of failure and the effects of bone mineral density (BMD) related changes. Cite this article: Bone Joint J 2021;103-B(4):644-649.

30-day outcome after orthopaedic surgery in patients assessed as negative for COVID-19 at the time of surgery during the peak of the pandemic.

INTRODUCTION: The aim of this study is to report the 30 day COVID-19 related morbidity and mortality of patients assessed as SARS-CoV-2 negative who underwent emergency or urgent orthopaedic surgery in the NHS during the peak of the COVID-19 pandemic. METHOD: A retrospective, single centre, observational cohort study of all patients undergoing surgery between 17 March 2020 and 3May 2020 was performed. Outcomes were stratified by British Orthopaedic Association COVID-19 Patient Risk Assessment Tool. Patients who were SARS-CoV-2 positive at the time of surgery were excluded. RESULTS: Overall, 96 patients assessed as negative for SARS-CoV-2 at the time of surgery underwent 100 emergency or urgent orthopaedic procedures during the study period. Within 30 days of surgery 9.4% of patients (n = 9) were found to be SARS-CoV-2 positive by nasopharyngeal swab. The overall 30 day mortality rate across the whole cohort of patients during this period was 3% (n = 3). Of those testing positive for SARS-CoV-2 66% (n = 6) developed significant COVID-19 related complications and there was a 33% 30-day mortality rate (n = 3). Overall, the 30-day mortality in patients classified as BOA low or medium risk (n = 69) was 0%, whereas in those classified as high or very high risk (n = 27) it was 11.1%. CONCLUSION: Orthopaedic surgery in SARS-CoV-2 negative patients who transition to positive within 30 days of surgery carries a significant risk of morbidity and mortality. In lower risk groups, the overall risk of becoming SARS-CoV-2 positive, and subsequently developing a significant postoperative related complication, was low even during the peak of the pandemic. In addition to ensuring patients are SARS-CoV-2 negative at the time of surgery it is important that the risk of acquiring SARS-CoV-2 is minimized through their recovery.Cite this article: Bone Joint Open 2020;1-8:474-480.

Debridement, antibiotics and implant retention (DAIR) for the management of knee prosthetic joint infection.

BACKGROUND: While two-stage revision arthroplasty is viewed as the gold standard for the treatment of knee periprosthetic joint infection (PJI) in terms of infection eradication, it is associated with significant cost along with patient morbidity and mortality. Debridement, antibiotics, and implant retention (DAIR) is an attractive option as it has demonstrated better patient outcomes, comparable implant longevity to primary arthroplasty, and significantly reduced cost when successful. Given the heterogeneity of what is defined as a DAIR the literature is highly variable in terms of its efficacy from the perspective of infection eradication. METHODS: In the setting of a previously well-functioning, well-fixed arthroplasty with an acceptable soft tissue envelope and a treatable organism we report our methods for proceeding with a DAIR procedure, both unicompartmental and total knee. RESULTS: With the above methods we have demonstrated improved patient outcomes when compared to one- or two-stage arthroplasty with lower patient morbidity. Implant longevity in the setting of a successful DAIR is equivalent to those of a primary arthroplasty. CONCLUSIONS: With appropriate indications and good surgical technique as described we believe DAIR is an excellent option in the treatment of periprosthetic joint infection. We hope that with a well-defined protocol as outlined we can gain a better understanding of the efficacy of DAIR procedure with more homogeneity to the procedure to better define when they are most successful while improving patient outcomes and reducing cost.

Modifiable risk factors for mortality in revision total hip arthroplasty for periprosthetic fracture.

AIMS: The aim of this study was to identify modifiable risk factors associated with mortality in patients requiring revision total hip arthroplasty (THA) for periprosthetic hip fracture. METHODS: The electronic records of consecutive patients undergoing revision THA for periprosthetic hip fracture between December 2011 and October 2018 were reviewed. The data which were collected included age, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) classification, the preoperative serum level of haemoglobin, time to surgery, operating time, blood transfusion, length of hospital stay, and postoperative surgical and medical complications. Univariate and multivariate logistic regression analyses were used to determine independent modifiable factors associated with mortality at 90 days and one year postoperatively. RESULTS: A total of 203 patients were identified. Their mean age was 78 years (44 to 100), and 108 (53%) were female. The median time to surgery was three days (interquartile range (IQR) 2 to 5). The mortality rate at one year was 13.8% (n = 28). The commonest surgical complication was dislocation (n = 22, 10.8%) and the commonest medical complication within 90 days of surgery was hospital-acquired pneumonia (n = 25, 12%). Multivariate analysis showed that the rate of mortality one year postoperatively was five-fold higher in patients who sustained a dislocation (odds ratio (OR) 5.03 (95% confidence interval (CI) 1.60 to 15.83); p = 0.006). The rate of mortality was also four-fold higher in patients who developed hospital-acquired pneumonia within 90 days postoperatively (OR 4.43 (95% CI 1.55 to 12.67); p = 0.005). There was no evidence that the time to surgery was a risk factor for death at one year. CONCLUSION: Dislocation and hospital-acquired pneumonia following revision THA for a periprosthetic fracture are potentially modifiable risk factors for mortality. This study suggests that surgeons should consider increasing constraint to reduce the risk of dislocation, and the early involvement of a multidisciplinary team to reduce the risk of hospital-acquired pneumonia. We found no evidence that the time to surgery affected mortality, which may allow time for medical optimization, surgical planning, and resource allocation. Cite this article: Bone Joint J 2020;102-B(5):580-585.

Sonication versus Tissue Sampling for Diagnosis of Prosthetic Joint and Other Orthopedic Device-Related Infections.

Current guidelines recommend collection of multiple tissue samples for diagnosis of prosthetic joint infections (PJI). Sonication of explanted devices has been proposed as a potentially simpler alternative; however, reported microbiological yield varies. We evaluated sonication for diagnosis of PJI and other orthopedic device-related infections (DRI) at the Oxford Bone Infection Unit between October 2012 and August 2016. We compared the performance of paired tissue and sonication cultures against a "gold standard" of published clinical and composite clinical and microbiological definitions of infection. We analyzed explanted devices and a median of five tissue specimens from 505 procedures. Among clinically infected cases the sensitivity of tissue and sonication culture was 69% (95% confidence interval, 63 to 75) and 57% (50 to 63), respectively (P < 0.0001). Tissue culture was more sensitive than sonication for both PJI and other DRI, irrespective of the infection definition used. Tissue culture yield was higher for all subgroups except less virulent infections, among which tissue and sonication culture yield were similar. The combined sensitivity of tissue and sonication culture was 76% (70 to 81) and increased with the number of tissue specimens obtained. Tissue culture specificity was 97% (94 to 99), compared with 94% (90 to 97) for sonication (P = 0.052) and 93% (89 to 96) for the two methods combined. Tissue culture is more sensitive and may be more specific than sonication for diagnosis of orthopedic DRI in our setting. Variable methodology and case mix may explain reported differences between centers in the relative yield of tissue and sonication culture. Culture yield was highest for both methods combined.

Clinical Outcome of Massive Endoprostheses Used for Managing Periprosthetic Joint Infections of the Hip and Knee.

BACKGROUND: Endoprosthetic replacement (EPR) is an option for management of massive bone loss resulting from infection around failed lower limb implants. The aim of this study is to determine the mid-term outcome of EPRs performed in the treatment of periprosthetic joint infection (PJI) and infected failed osteosyntheses around the hip and knee joint and identify factors that influence it. METHODS: We retrospectively reviewed all hip and knee EPRs performed between 2007 and 2014 for the management of chronic infection following complex arthroplasty or fracture fixation. Data recorded included indication for EPR, number of previous surgeries, comorbidities, and organism identified. Outcome measures included PJI eradication rate, complications, implant survival, mortality, and functional outcome (Oxford Hip or Knee Score). RESULTS: Sixty-nine EPRs (29 knees and 40 hips) were performed with a mean age of 68 years (43-92). Polymicrobial growth was detected in 36% of cases, followed by coagulase-negative staphylococci (28%) and Staphylococcus aureus (10%). Recurrence of infection occurred in 19 patients (28%): 5 were treated with irrigation and debridement, 5 with revision, 1 with above-knee amputation, and 8 remain on long-term antibiotics. PJI eradication was achieved in 50 patients (72%); the chance of PJI eradication was greater in hips (83%) than in knees (59%) (P = .038). The 5-year implant survivorship was 81% (95% confidence interval 74-88). The mean Oxford Hip Score and Oxford Knee Score were 22 (4-39) and 21 (6-43), respectively. CONCLUSION: This study supports the use of EPRs for eradication of PJI in complex, multiply revised cases. We describe PJI eradication rate of 72% with acceptable functional outcome.