The recombinant Link module of human TSG-6 suppresses cartilage damage in models of osteoarthritis: A potential disease-modifying OA drug.

OBJECTIVE: To investigate the role of endogenous TSG-6 in human osteoarthritis (OA) and assess the disease-modifying potential of a TSG-6-based biological treatment in cell, explant and animal models of OA. DESIGN: Knee articular cartilages from OA patients were analyzed for TSG-6 protein and mRNA expression using immunohistochemistry and RNAscope, respectively. The inhibitory activities of TSG-6 and its isolated Link module (Link_TSG6) on cytokine-induced degradation of OA cartilage explants were compared. Human mesenchymal stem/stromal cell-derived chondrocyte pellet cultures were used to determine the effects of Link_TSG6 and full-length TSG-6 on IL-1α-, IL-1ß-, or TNF-stimulated ADAMTS4, ADAMTS5, and MMP13 mRNA expression. Link_TSG6 was administered i.a. to the rat ACLTpMMx model; cartilage damage and tactile allodynia were assessed. RESULTS: TSG-6 is predominantly associated with chondrocytes in regions of cartilage damage where high TSG-6 expression aligns with low MMP13, the major collagenase implicated in OA progression. Link_TSG6 is more potent than full-length TSG-6 at inhibiting cytokine-mediated matrix breakdown in human OA cartilage explants;>50% of donor cartilages, from 59 tested, were responsive to Link_TSG6 treatment. Link_TSG6 also displayed more potent effects in 3D pellet cultures, suppressing ADAMTS4, ADAMTS5, and MMP13 gene expression, which was consistent with reduced aggrecanase and collagenase activities in explant cultures. Link_TSG6 treatment reduced touch-evoked pain behavior and dose-dependently inhibited cartilage damage in a rodent model of surgically-induced OA. CONCLUSIONS: Link_TSG6 has enhanced chondroprotective activity compared to the full-length TSG-6 protein and shows potential as a disease modifying OA drug via its inhibition of aggrecanase and collagenase activity.

Re-revision Knee Arthroplasty in a Tertiary Center: Infection and Multiple Previous Surgeries Were Associated With Poor Early Clinical and Functional Outcomes.

BACKGROUND: The incidence of re-revision knee arthroplasty (re-revision KA) is increasing and associated with high complication and failure rates. The aim of this study was to investigate re-revision rates, complications, and patient-reported outcomes following re-revision KA and factors associated with poor outcome. METHODS: This was a retrospective cohort study of 206 patients (250 knees) undergoing re-revision KA at a major revision center from 2015 to 2018. The mean follow-up was 26 months (range, 0 to 61) and mean age at re-revision KA was 69 years (range, 31 to 91 years). The main indications for surgery were prosthetic joint infection (PJI) (n = 171/250, 68.4%) and aseptic loosening (n = 25/250, 10.0%). We compared re-revision rates, joint function, and complications for aseptic and infective indications. Logistic regressions were performed to identify risk factors for further reoperation. RESULTS: The estimated re-revision rates at 2 years were 28.7% (95% confidence interval [CI]: 22.7-35.9) and at 4 years were 42.0% (95% CI: 32.8-52.6). Mean Oxford Knee Score was 26 points (range, 1 to 48). Mean EuroQoL-5D-5L utility was 0.539 (range, -0.511 to 1.000). Multivariable analyses demonstrated that PJI (Odds Ratio [OR] 2.39, 95% CI 1.06-5.40, P = .036), greater number of previous surgeries (OR 1.18, 95% CI 1.04-1.33, P = .008), and higher Elixhauser score (OR 1.06, 95% CI 1.01-1.13, P = .045) were independently associated to further surgery. CONCLUSION: Re-revision KA carried a high risk of early failure. Multiple revised joints and patients with more comorbidities had worse function. Patients undergoing re-revision KA for PJI should be counseled to expect higher failure rates and complications than patients who have aseptic indications.

Indications and techniques for non-articulating spacers in massive bone loss following prosthetic knee joint infection: a scoping review.

INTRODUCTION: Prosthetic joint infection (PJI) is a destructive complication of knee replacement surgery (KR). In two-stage revision a spacer is required to maintain limb length and alignment and provide a stable limb on which to mobilise. Spacers may be articulating or static with the gold standard spacer yet to be defined. The aims of this scoping review were to summarise the types of static spacer used to treat PJI after KR, their indications for use and early complication rates. METHODS: We conducted a scoping review based on the Joanna Briggs Institute's "JBI Manual for Evidence Synthesis" Scoping review reported following Preferred Reporting Items for Systematic Review and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) checklist. MEDLINE, EMBASE and CINAHL were searched from 2005 to 2022 for studies on the use of static spacers for PJI after KR. RESULTS: 41 studies (1230 patients/knees) were identified describing 42 static spacer constructs. Twenty-three (23/42 [54.2%]) incorporated cement augmented with metalwork, while nineteen (19/42, [45.9%]) were made of cement alone. Spacers were most frequently anchored in the diaphysis (22/42, [53.3%]), particularly in the setting of extensive bone loss (mean AORI Type = F3/T3; 11/15 studies 78.3% diaphyseal anchoring). 7.1% (79 of 1117 knees) of static spacers had a complication requiring further surgery prior to planned second stage with the most common complication being infection (86.1%). CONCLUSIONS: This study has summarised the large variety in static spacer constructs used for staged revision KR for PJI. Static spacers were associated with a high risk of complications and further work in this area is required to improve the quality of care in this vulnerable group.

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.

Preoperative Severe Acute Respiratory Syndrome Coronavirus 2 Polymerase Chain Reaction Test at Between 48 and 72 Hours Preoperatively is Safe for Patients Undergoing Primary and Revision Hip and Knee Arthroplasty: A Multicentre International Study.

BACKGROUND: Patients undergoing lower limb arthroplasty who are severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) positive at the time of surgery have a high risk of mortality. The National Institute for Health and Clinical Care Excellence and the British Orthopaedic Association advise self-isolation for 14 days preoperatively in patients at a high risk of adverse outcomes due to COVID-19. The aim of the study is to assess whether preoperative polymerase chain reaction (PCR) for SARS-CoV-2 could be performed at between 48 and 72 hours preoperatively with specific advice about minimizing the risk of SARS-CoV-2 restricted to between PCR and admission. METHODS: A multicentre, international, observational cohort study of 1,000 lower limb arthroplasty cases was performed. The dual primary outcomes were 30-day conversion to SARS-CoV-2 positive and 30-day SARS-CoV-2 mortality. Secondary outcomes included 30-day SARS-CoV-2 morbidity. RESULTS: Of the 1,000 cases, 935 (94%) had a PCR between 48 and 72 hours preoperatively. All cases were admitted to and had surgery through a COVID-free pathway. Primary knee arthroplasty was performed in 41% of cases, primary hip arthroplasty in 40%, revision knee arthroplasty in 11%, and revision hip arthroplasty in 9%. Six percent of operations were emergency operations. No cases of SARS-CoV-2 were identified within the first 30 days. CONCLUSION: Preoperative SARS-CoV-2 PCR test between 48 and 72 hours preoperatively with advice about minimizing the risk of SARS-CoV-2 restricted to between PCR and admission in conjunction with a COVID-free pathway is safe for patients undergoing primary and revision hip and knee arthroplasty. Preoperative SARS-CoV-2 PCR test alone may be safe but further adequately powered studies are required. This information is important for shared decision making with patients during the current pandemic.

Patient-Reported Function and Quality of Life After Revision Total Knee Arthroplasty: An Analysis of 10,727 Patients from the NHS PROMs Program.

BACKGROUND: The aim of the study was to investigate changes in patient-reported outcome measures (PROMs) after revision total knee arthroplasty (rTKA). METHODS: A total of 10,727 patients undergoing elective rTKA were recruited from the UK National Health Service PROMs data set from 2013 to 2019. PROMs were collected at baseline and six months to assess joint function (Oxford Knee Score, OKS) and quality of life (EQ-5D). Associations with a change in the OKS (COKS) were investigated through multiple linear regression. RESULTS: The mean COKS was 12.4 (standard deviation 10.7) points. A total of 6776 of 10,329 (65.6%) patients demonstrated increase in the OKS above the minimal important change of 7.5 points. The median change in the EQ-5D utility was 0.227 (interquartile range 0.000 to 0.554). A total of 4917 of 9279 (53.0%) patients achieved a composite endpoint of improvement greater than the minimal important change for joint function and 'better' QoL as per the Paretian analysis. A total of 7477 of 10,727 (69.7%) patients reported satisfaction with rTKA. A total of 7947 of 10,727 (74.1%) patients felt surgery was a success. A total of 4888 of 10,632 (46.0%) patients reported one or more adverse events. A higher preoperative OKS was associated with a lower COKS (coefficient -0.63 [95% confidence interval -0.67 to -0.60]). Other factors associated with a lower COKS were postoperative complication(s), age under 60 years, longer duration of knee problems, patients who identified as disabled, problems in EQ-5D dimensions of anxiety/depression and self-care, comorbid conditions (circulatory problems, diabetes, and depression), and earlier year of procedure in the data set. CONCLUSION: Two-thirds of patients experienced a meaningful improvement in joint function after rTKA. However, there was a high frequency of patient-reported complications. These findings may enable better informed discussion of the risks and benefits of discretionary rTKA.

Tourniquet use for knee replacement surgery.

BACKGROUND: Many surgeons prefer to perform total knee replacement surgery with the aid of a tourniquet. A tourniquet is an occlusive device that restricts distal blood flow to help create a bloodless field during the procedure. A tourniquet may be associated with increased risk of pain and complications. OBJECTIVES: To determine the benefits and harms of tourniquet use in knee replacement surgery. SEARCH METHODS: We searched MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) up to 26 March 2020. We searched clinicaltrials.gov, the World Health Organization trials portal, and several international registries and joint registries up to March 2020. SELECTION CRITERIA: We included randomised controlled trials (RCTs) comparing knee replacement with use of a tourniquet versus without use of a tourniquet and non-randomised studies with more than 1000 participants. Major outcomes included pain, function, global assessment of success, health-related quality of life, serious adverse events (including venous thromboembolism, infection, re-operation, and mortality), cognitive function, and survival of the implant. Minor outcomes included blood loss, economic outcomes, implant stability, and adverse events. DATA COLLECTION AND ANALYSIS: Two review authors screened abstracts and full texts, extracted data, performed risk of bias assessments, and assessed the certainty of the evidence using the GRADE approach. MAIN RESULTS: We included 41 RCTs with 2819 participants. Trials included from 20 to 199 participants. Mean age ranged between 58 and 84 years. More than half of the RCTs had unclear risk of selection bias and unclear risk of performance and detection bias due to absence of blinding of participants and surgeons. Major outcomes Pain: at postoperative day 1, pain (on a scale from zero to 10, with higher scores indicating worse pain) was ranked at 4.56 points after surgery without a tourniquet and at 1.25 points (MD) higher (95% CI 0.32 higher to 2.19 higher) with a tourniquet (8 studies; 577 participants), for an absolute difference of 12.5% higher pain scores (95% CI 3.2% higher to 21.9% higher) and a relative difference of 19% higher pain scores (95% CI 3.4% higher to 49% higher) with a tourniquet. Evidence for these findings was of moderate certainty, downgraded due to risk of bias. Knee replacement with a tourniquet probably led to higher postoperative pain scores at day 1, although this difference may or may not be noticeable to patients (based on a minimal clinically important difference (MCID) of 1.0). Function: at 12 months, tourniquet use probably makes little or no difference to function, based on an MCID of 5.3 for Knee Society Score (KSS) and 5.0 for Oxford Knee Score (OKS). Mean function (on a scale from 0 to 100, with higher scores indicating better outcomes) was 90.03 points after surgery without a tourniquet and was 0.29 points worse (95% CI 1.06 worse to 0.48 better) on a 0 to 100 scale, absolute difference was 0.29% worse (1.06% worse to 0.48% better), with a tourniquet (5 studies; 611 participants). This evidence was downgraded to moderate certainty due to risk of bias. Global assessment of success: low-certainty evidence (downgraded due to bias and imprecision) indicates that tourniquet use may have little or no effect on success. At six months, 47 of 50 (or 940 per 1000) reported overall successful treatment after surgery without a tourniquet and 47 of 50 (or 940 per 1000) with a tourniquet (risk ratio (RR) 1.0, 95% CI 0.91 to 1.10) based on one study with 100 participants. Health-related quality of life: at six months, tourniquet may have little or no effect on quality of life. The 12-Item Short Form Survey (SF-12) score (mental component from zero to 100 (100 is best)) was 54.64 after surgery without a tourniquet and 1.53 (MD) better (95% CI 0.85 worse to 3.91 better) with a tourniquet (1 study; 199 participants); absolute difference was 1.53% better (0.85% worse to 3.91% better). Evidence was of low certainty, downgraded due to risk of bias and small number of participants. Serious adverse events: the risk of serious adverse events was probably higher with tourniquet; 26 of 898 (29 per 1000) reported events following surgery without a tourniquet compared to 53 of 901 (59 per 1000) with a tourniquet (RR 1.73, 95% CI 1.10 to 2.73) in 21 studies (1799 participants). Twenty-nine more per 1000 patients (95% CI 3 to 50 more per 1000 patients) had a serious adverse event with a tourniquet. Forty-eight (95% CI 20 to 345) participants would need to have surgery without a tourniquet to avoid one serious adverse event. This evidence was downgraded to moderate certainty due to risk of bias. Cognitive function: one study reported cognitive function as an outcome; however the data were incompletely reported and could not be extracted for analysis. Survival of implant: it is uncertain if tourniquet has an effect on implant survival due to very low certainty evidence (downgraded for bias, and twice due to very low event rates); 2 of 107 (19 per 1000) required revision surgery in the surgery with a tourniquet group compared to 1 of 107 (9 per 1000) without a tourniquet group at up to two years' follow-up (RR 1.44, 95% CI 0.23 to 8.92). This equates to a 0.4% (0.7% lower to 7% more) increased absolute risk in surgery with a tourniquet. AUTHORS' CONCLUSIONS: Moderate certainty evidence shows that knee replacement surgery with a tourniquet is probably associated with an increased risk of serious adverse events. Surgery with a tourniquet is also probably associated with higher postoperative pain, although this difference may or may not be noticeable to patients. Surgery with a tourniquet does not appear to confer any clinically meaningful benefit on function, treatment success or quality of life. Further research is required to explore the effects of tourniquet use on cognitive function and implant survival, to identify any additional harms or benefits. If a tourniquet continues to be used in knee replacement surgery, patients should be informed about the potential increased risk of serious adverse events and postoperative pain.

ANTECEDENTES: Muchos cirujanos prefieren realizar una cirugía de reemplazo total de rodilla con la ayuda de un torniquete. Un torniquete es un dispositivo oclusivo que restringe el flujo sanguíneo distal para ayudar a crear un campo sin sangre durante el procedimiento. El torniquete se puede asociar con un mayor riesgo de dolor y complicaciones. OBJETIVOS: Determinar los efectos beneficiosos y perjudiciales del uso de torniquetes en la cirugía de reemplazo de rodilla. MÉTODOS DE BÚSQUEDA: Se hicieron búsquedas en MEDLINE, Embase y en el Registro Cochrane central de ensayos controlados (CENTRAL) hasta el 26 de marzo de 2020. Se realizaron búsquedas en clinicaltrials.gov, el portal de ensayos de la Organización Mundial de la Salud, y en varios registros internacionales y registros conjuntos hasta marzo de 2020. CRITERIOS DE SELECCIÓN: Se incluyeron los ensayos controlados aleatorizados (ECA) que compararon el reemplazo de rodilla con el uso de un torniquete versus sin el uso de un torniquete y los estudios no aleatorizados con más de 1000 participantes. Los desenlaces principales fueron el dolor, la funcionalidad, la evaluación general del éxito, la calidad de vida relacionada con la salud, los eventos adversos graves (incluido el tromboembolismo venoso, la infección, la reintervención y la mortalidad), la función cognitiva y la supervivencia del implante. Los desenlaces secundarios incluyeron la pérdida de sangre, los desenlaces económicos, la estabilidad del implante y los eventos adversos. OBTENCIÓN Y ANÁLISIS DE LOS DATOS: Dos autores de la revisión examinaron los resúmenes y los textos completos, extrajeron los datos, realizaron las evaluaciones del riesgo de sesgo y evaluaron la certeza de la evidencia utilizando el enfoque GRADE. RESULTADOS PRINCIPALES: Se incluyeron 41 ECA con 2819 participantes. Los ensayos incluyeron de 20 a 199 participantes. La media de edad varió entre 58 y 84 años. Más de la mitad de los ECA tenían riesgo incierto de sesgo de selección y riesgo incierto de sesgo de realización y detección debido a la falta de cegamiento de los participantes y los cirujanos. Desenlaces principales Dolor: en el primer día después de la cirugía, el dolor (en una escala de 0 a 10, con puntuaciones mayores que indican un peor dolor) se clasificó en 4,56 puntos después de la cirugía sin torniquete y en 1,25 puntos (DM) mayor (IC del 95%: 0,32 mayor a 2,19 mayor) con un torniquete (ocho estudios; 577 participantes), para una diferencia absoluta de 12,5% de puntuaciones mayores de dolor (IC del 95%: 3,2% mayor a 21,9% mayor) y una diferencia relativa de 19% de puntuaciones mayores de dolor (IC del 95%: 3,4% mayor a 49% mayor) con un torniquete. La evidencia de estos hallazgos fue de certeza moderada, disminuida debido al riesgo de sesgo. El reemplazo de rodilla con un torniquete probablemente dio lugar a mayores puntuaciones de dolor en el primer día después de la cirugía, aunque esta diferencia puede o no ser perceptible para los pacientes (sobre la base de una diferencia mínima clínicamente importante [DMCI] de 1,0). Funcionalidad: a los 12 meses el uso de torniquetes probablemente da lugar a poca o ninguna diferencia en la funcionalidad, según una DMCI de 5,3 en la Knee Society Score (KSS) y de 5,0 en la Oxford Knee Score (OKS). La funcionalidad media (en una escala de 0 a 100, con puntuaciones más altas que indican mejores desenlaces) fue de 90,03 puntos después de la cirugía sin torniquete y fue 0,29 puntos peor (IC del 95%: 1,06 peor a 0,48 mejor) en una escala de 0 a 100, la diferencia absoluta fue 0,29% peor (1,06% peor a 0,48% mejor), con un torniquete (cinco estudios; 611 participantes). Esta evidencia se disminuyó a certeza moderada debido al riesgo de sesgo. Evaluación general del éxito: evidencia de certeza baja (disminuida debido al sesgo y la imprecisión) indica que el uso de torniquetes puede tener poco o ningún efecto en el éxito. A los seis meses, 47 de 50 (o 940 por 1000) informaron de un tratamiento general exitoso después de la cirugía sin torniquete y 47 de 50 (o 940 por 1000) con torniquete (razón de riesgos [RR] 1,0; IC del 95%: 0,91 a 1,10), según un estudio con 100 participantes. Calidad de vida relacionada con la salud: a los seis meses, el torniquete puede tener poco o ningún efecto en la calidad de vida. La puntuación de la 12­Item Short Form Survey (SF­12) (componente mental de 0 a 100 [100 es mejor]) fue de 54,64 después de la cirugía sin torniquete y 1,53 (DM) mejor (IC del 95%: 0,85 peor a 3,91 mejor) con torniquete (un estudio; 199 participantes); la diferencia absoluta fue 1,53% mejor (0,85% peor a 3,91% mejor). La evidencia fue de certeza baja, y se disminuyó debido al riesgo de sesgo y al escaso número de participantes. Eventos adversos graves: el riesgo de eventos adversos graves probablemente fue mayor con el uso de un torniquete; 26 de 898 (29 por 1000) notificaron eventos después de la cirugía sin torniquete en comparación con 53 de 901 (59 por 1000) con un torniquete (RR 1,73; IC del 95%: 1,10 a 2,73) en 21 estudios (1799 participantes). Veintinueve más por cada 1000 pacientes (95% CI 3 a 50 más por 1000 pacientes) presentaron un evento adverso grave con un torniquete. Cuarenta y ocho (IC del 95%: 20 a 345) participantes tendrían que ser operados sin torniquete para evitar un evento adverso grave. Esta evidencia se disminuyó a certeza moderada debido al riesgo de sesgo. Función cognitiva: un estudio informó de la función cognitiva como un desenlace; sin embargo, los datos se informaron de manera incompleta y no se pudieron extraer para el análisis. Supervivencia del implante: no está claro si el torniquete tiene un efecto sobre la supervivencia del implante debido a evidencia de certeza muy baja (disminuida por el sesgo, y dos veces debido a las tasas de eventos muy bajas); dos de 107 (19 por 1000) requirieron cirugía de revisión en el grupo de cirugía con torniquete en comparación con uno de 107 (nueve por 1000) en el grupo sin torniquete hasta los dos años de seguimiento (RR 1,44; IC del 95%: 0,23 a 8,92). Esto equivale a un 0,4% (0,7% menos a 7% más) de aumento del riesgo absoluto en la cirugía con torniquete. CONCLUSIONES DE LOS AUTORES: Evidencia de certeza moderada muestra que la cirugía de reemplazo de rodilla con torniquete probablemente se asocia con un mayor riesgo de eventos adversos graves. La cirugía con torniquete también se asocia probablemente con un mayor dolor posoperatorio, aunque esta diferencia puede o no ser perceptible para los pacientes. La cirugía con torniquete no parece conferir efectos beneficiosos clínicamente significativos en la funcionalidad, el éxito del tratamiento o la calidad de vida. Se necesitan estudios de investigación adicionales para explorar los efectos del uso de torniquetes en la función cognitiva y la supervivencia del implante, para identificar cualquier efecto perjudicial o beneficioso adicional. Si se sigue utilizando un torniquete en la cirugía de reemplazo de rodilla, se debe informar a los pacientes sobre el posible aumento del riesgo de que se produzcan efectos adversos graves y dolor posoperatorio.

Anterior cruciate ligament (ACL) reconstruction and meniscal repair rates have both increased in the past 20 years in England: hospital statistics from 1997 to 2017.

OBJECTIVES: We investigated the temporal trend and the geographical variation in the rate of an anterior cruciate ligament (ACL) reconstruction and meniscal repair (MR) performed in England during a 20-year window. METHODS: All hospital episodes for patients undergoing ACL reconstruction or MR between 1 April 1997 and 31 March 2017 were extracted by procedure code from the national hospital episode statistics. Age-standardised and sex-standardised rates of surgery were calculated using Office for National Statistics population data as the denominator and analysed over time both nationally and regionally by National Health Service clinical commissioning group (CCG). RESULTS: Between 1997-1998 and 2016-2017, there were 133 270 cases of ACL reconstruction (124 489 patients) and 42 651 cases of MR (41 120 patients) (isolated or simultaneous). Nationally, the rate of ACL reconstruction increased 12-fold from 2.0/100K population (95% CI 1.9 to 2.1) in 1997-1998 to 24.2/100K (95% CI 23.8 to 24.6) in 2016-2017. The rate of MR increased more than twofold from 3.0/100K (95% CI 2.8 to 3.1) in 1997-1998 to 7.3/100K (95% CI 7.1 to 7.5) in 2016-2017. Of these cases, the rate of simultaneous ACL reconstruction and MR was 2.6/100K (95% CI 2.5 to 2.8) in 2016/2017. In 2016-2017, for patients aged 20-29, the sex-standardised rate of ACL reconstruction was 76.9/100K (95% CI 74.9 to 78.9) and for MR was 19.8/100K (95% CI 18.8 to 20.9). Practice varied by region-in 2016-2017, 14.5% (30/207) of the CCGs performed more than twice the national average rate of ACL reconstruction and 15.0% (31/207) performed more than twice the national average rate of MR. CONCLUSIONS: The rate of ACL reconstruction (12-fold) and MR (2.4-fold) has increased in England over the last two decades. There is variation in these rates across geographical regions and further work is required to deliver standardised treatment guidance for appropriate use.

Arthroscopic partial meniscectomy for meniscal tears of the knee: a systematic review and meta-analysis.

OBJECTIVE: To assess the benefit of arthroscopic partial meniscectomy (APM) in adults with a meniscal tear and knee pain in three defined populations (taking account of the comparison intervention): (A) all patients (any type of meniscal tear with or without radiographic osteoarthritis); (B) patients with any type of meniscal tear in a non-osteoarthritic knee; and (C) patients with an unstable meniscal tear in a non-osteoarthritic knee. DESIGN: Systematic review and meta-analysis. DATASOURCES: A search of MEDLINE, Embase, CENTRAL, Scopus, Web of Science, Clinicaltrials.gov and ISRCTN was performed, unlimited by language or publication date (inception to 18 October 2018). ELIGIBILITYCRITERIA: Randomised controlled trials performed in adults with meniscal tears, comparing APM versus (1) non-surgical intervention; (2) pharmacological intervention; (3) surgical intervention; and (4) no intervention. RESULTS: Ten trials were identified: seven compared with non-surgery, one pharmacological and two surgical. Findings were limited by small sample size, small number of trials and cross-over of participants to APM from comparator interventions. In group A (all patients) receiving APM versus non-surgical intervention (physiotherapy), at 6-12 months, there was a small mean improvement in knee pain (standardised mean difference [SMD] 0.22 [95% CI 0.03 to 0.40]; five trials, 943 patients; I2 48%; Grading of Recommendations Assessment, Development and Evaluation [GRADE]: low), knee-specific quality of life (SMD 0.43 [95% CI 0.10 to 0.75]; three trials, 350 patients; I2 56%; GRADE: low) and knee function (SMD 0.18 [95% CI 0.04 to 0.33]; six trials, 1050 patients; I2 27%; GRADE: low). When the analysis was restricted to people without osteoarthritis (group B), there was a small to moderate improvement in knee pain (SMD 0.35 [95% CI 0.04 to 0.66]; three trials, 402 patients; I2 58%; GRADE: very low), knee-specific quality of life (SMD 0.59 [95% CI 0.11 to 1.07]; two trials, 244 patients; I2 71%; GRADE: low) and knee function (SMD 0.30 [95% CI 0.06 to 0.53]; four trials, 507 patients; I2 44%; GRADE: very low). There was no improvement in knee pain, function or quality of life in patients receiving APM compared with placebo surgery at 6-12 months in group A or B (pain: SMD 0.08 [95% CI -0.24 to 0.41]; one trial, 146 patients; GRADE: low; function: SMD -0.08 [95% CI -0.41 to 0.24]; one trial, 146 patients; GRADE: high; quality of life: SMD 0.05 [95% CI -0.27 to 0.38]; one trial; 146 patients; GRADE: high). No trials were identified for people in group C. CONCLUSION: Performing APM in all patients with knee pain and a meniscal tear is not appropriate, and surgical treatment should not be considered the first-line intervention. There may, however, be a small-to-moderate benefit from APM compared with physiotherapy for patients without osteoarthritis. No trial has been limited to patients failing non-operative treatment or patients with an unstable meniscal tear in a non-arthritic joint; research is needed to establish the value of APM in this population. PROTOCOL REGISTRATION NUMBER: PROSPERO CRD42017056844.

Varus alignment of the proximal tibia is associated with structural progression in early to moderate varus osteoarthritis of the knee.

PURPOSE: Lower limb malalignment is a strong predictor of progression in knee osteoarthritis. The purpose of this study is to identify the individual alignment variables that predict progression in early to moderate osteoarthritis of the knee. METHOD: A longitudinal cohort study using data from the Osteoarthritis Initiative. In total, 955 individuals (1329 knees) with early to moderate osteoarthritis (Kellgren-Lawrence grade 1, 2 or 3) were identified. All subjects had full-limb radiographs analysed using the Osteotomy module within Medicad® Classic (Hectec GMBH) to give a series of individual alignment variables relevant to the coronal alignment of the lower limb. Logistic regression models, with generalised estimating equations were used to identify which of these individual alignment variables predict symptom worsening (WOMAC score > 9 points) and or structural progression (joint space narrowing progression in the medial compartment > 0.7mm) over 24 months. RESULTS: Individual alignment variable were associated with both valgus and varus alignment (mechanical Lateral Distal Femoral Angle, Medial Proximal Tibial Angle and mechanical Lateral Distal Tibial Angle). Only the Medial Proximal Tibial Angle was significantly associated with structural progression and none of the variables was associated with symptom progression. The odds of joint space narrowing progression in the medial compartment occurring at 24 months increased by 21% for every one degree decrease (more varus) in Medial Proximal Tibial Angle (p < 0.001) CONCLUSIONS: Our results suggest that the risk of structural progression in the medial compartment is associated with greater varus alignment of the proximal tibia. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

Manipulation Under Anesthetic After Primary Knee Arthroplasty Is Associated With a Higher Rate of Subsequent Revision Surgery.

AIM: To determine the association between manipulation under anesthetic (MUA) after primary knee arthroplasty and subsequent revision surgery. METHODS: Patients undergoing primary knee arthroplasty from April 2011 to April 2016 with minimum 1-year follow-up to April 2017 were identified from the national hospital episode statistics for England. The first arthroplasty per patient, per side, was included; cases with a record of subsequent infection or periprosthetic fracture were excluded. Patients undergoing MUA within 1 year to the same knee were identified, defining the populations for the MUA and non-MUA cohorts. Mortality-adjusted Kaplan-Meier survival analysis (revision arthroplasty) was performed to a maximum of 6 years. A Cox proportional hazards model was used to determine the hazard for revision, adjusting for type of primary arthroplasty, gender, age group, year, comorbidity index, obesity, regional deprivation, rurality, and ethnicity. RESULTS: A total of 309,650 primary arthroplasty cases (309,650 patients) were included. MUA within 1 year was recorded in 6882 patients (2.22%; 95% confidence interval [95% CI], 2.17-2.28) defining the MUA cohort; all others were included in the parallel non-MUA cohort. At 6 years, the mortality-adjusted estimated implant survival rate in the MUA cohort was 91.2% (95% CI, 90.0-92.2) in comparison to 98.1% (95% CI, 98.0-98.2) in the non-MUA cohort. In the fully adjusted model, this corresponded to an adjusted hazard for revision of 5.03 (hazard ratio; 95% CI, 4.55-5.57). CONCLUSION: Patients who underwent MUA within 1 year of primary arthroplasty were at a 5-fold increased risk of subsequent revision even after excluding cases of infection or fracture. Further investigation of the etiology of stiffness after primary knee arthroplasty and the optimal treatment options to improve outcomes is justified.

Adverse outcomes after arthroscopic partial meniscectomy: a study of 700 000 procedures in the national Hospital Episode Statistics database for England.

BACKGROUND: Arthroscopic partial meniscectomy is one of the most common orthopaedic procedures worldwide. Clinical trial evidence published in the past 6 years, however, has raised questions about the effectiveness of the procedure in some patient groups. In view of concerns about potential overuse, we aimed to establish the true risk of serious complications after arthroscopic partial meniscectomy. METHODS: We analysed national Hospital Episode Statistics data for all arthroscopic partial meniscectomies done in England between April 1, 1997, and March 31, 2017. Simultaneous or staged (within 6 months) bilateral cases were excluded. We identified complications occurring in the 90 days after the index procedure. The primary outcome was the occurrence of at least one serious complication within 90 days, which was defined as either myocardial infarction, stroke, pulmonary embolism, infection requiring surgery, fasciotomy, neurovascular injury, or death. Logistic regression modelling was used to identify factors associated with complications and, when possible, risk was compared with general population data. FINDINGS: During the study period 1 088 782 arthroscopic partial meniscectomies were done, 699 965 of which were eligible for analysis. Within 90 days, serious complications occurred in 2218 (0·317% [95% CI 0·304-0·330]) cases, including 546 pulmonary embolisms (0·078% [95% CI 0·072-0·085]) and 944 infections necessitating further surgery (0·135% [95% CI 0·126-0·144]). Increasing age (adjusted odds ratio [OR] 1·247 per decade [95% CI 1·208-1·288) and modified Charlson comorbidity index (adjusted OR 1·860 per 10 units [95% CI 1·708-2·042]) were associated with an increased risk of serious complications. Female sex was associated with a reduced risk of serious complications (adjusted OR 0·640 [95% CI 0·580-0·705). The risk of mortality fell over time (adjusted OR 0·965 per year [95% CI 0·937-0·994]). Mortality, myocardial infarction, and stroke occurred less frequently in the study cohort than in the general population. The risks of infection and pulmonary embolism did not change during the study, and were significantly higher in the study cohort than in the general population. For every 1390 (95% CI 1272-1532) fewer knee arthroscopies done, one pulmonary embolism could be prevented. For every 749 (95% CI 704-801) fewer procedures done, one native knee joint infection could be prevented. INTERPRETATION: Overall, the risk associated with undergoing arthroscopic partial meniscectomy was low. However, some rare but serious complications (including pulmonary embolism and infection) are associated with the procedure, and the risks have not fallen with time. In view of uncertainty about the effectiveness of arthroscopic partial meniscectomy, an appreciation of relative risks is crucial for patients and clinicians. Our data provide a basis for decision making and consent. FUNDING: UK National Institute for Health Research.

Knee replacement.

Knee replacement surgery is one of the most commonly done and cost-effective musculoskeletal surgical procedures. The numbers of cases done continue to grow worldwide, with substantial variation in utilisation rates across regions and countries. The main indication for surgery remains painful knee osteoarthritis with reduced function and quality of life. The threshold for intervention is not well defined, and is influenced by many factors including patient and surgeon preference. Most patients have a very good clinical outcome after knee replacement, but multiple studies have reported that 20% or more of patients do not. So despite excellent long-term survivorship, more work is required to enhance this procedure and development is rightly focused on increasing the proportion of patients who have successful pain relief after surgery. Changing implant design has historically been a target for improving outcome, but there is greater recognition that improvements can be achieved by better implantation methods, avoiding complications, and improving perioperative care for patients, such as enhanced recovery programmes. New technologies are likely to advance future knee replacement care further, but their introduction must be regulated and monitored with greater rigour to ensure patient safety.

Surgical interventions for symptomatic mild to moderate knee osteoarthritis.

BACKGROUND: Osteoarthritis affecting the knee is common and represents a continuum of disease from early cartilage thinning to full-thickness cartilage loss, bony erosion, and deformity. Many studies do not stratify their results based on the severity of the disease at baseline or recruitment. OBJECTIVES: To assess the benefits and harms of surgical intervention for the management of symptomatic mild to moderate knee osteoarthritis defined as knee pain and radiographic evidence of non-end stage osteoarthritis (Kellgren-Lawrence grade 1, 2, 3 or equivalent on MRI/arthroscopy). Outcomes of interest included pain, function, radiographic progression, quality of life, short-term serious adverse events, re-operation rates and withdrawals due to adverse events. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Embase up to May 2018. We also conducted searches of ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform for ongoing trials. Authors of trials were contacted if some but not all their participants appeared to fit our inclusion criteria. SELECTION CRITERIA: We included randomised controlled trials that compared surgery to non-surgical interventions (including sham and placebo control groups, exercise or physiotherapy, and analgesic or other medication), injectable therapies, and trials that compared one type of surgical intervention to another surgical intervention in people with symptomatic mild to moderate knee osteoarthritis. DATA COLLECTION AND ANALYSIS: Two review authors independently selected trials and extracted data using standardised forms. We analysed the quality of evidence using the GRADE (Grades of Recommendation, Assessment, Development and Evaluation) approach. MAIN RESULTS: A total of five studies involving 566 participants were identified as eligible for this review. Single studies compared arthroscopic partial meniscectomy to physical therapy (320 participants), arthroscopic surgery (debridement ± synovectomy ± chondroplasty) to closed needle joint lavage with saline (32 participants) and high tibial osteotomy surgery to knee joint distraction surgery (62 participants). Two studies (152 participants) compared arthroscopic surgery (washout ± debridement; debridement) to a hyaluronic acid injection. Only one study was at low risk of selection bias, and due to the difficulty of blinding participants to their treatment, all studies were at risk of performance and detection bias.Reporting of results in this summary has been restricted to the primary comparison: surgical intervention versus non-surgical intervention.A single study, included 320 participants with symptoms consistent with meniscal tear. All subjects had the meniscal tear confirmed on knee MRI and radiographic evidence of mild to moderate osteoarthritis (osteophytes, cartilage defect or joint space narrowing). Patients with severe osteoarthritis (KL grade 4) were excluded. The study compared arthroscopic partial meniscectomy and physical therapy to physical therapy alone (a six-week individualised progressive home exercise program). This study was at low risk of selection bias and outcome reporting biases, but was susceptible to performance and detection biases. A high rate of cross-over (30.2%) occurred from the physical therapy group to the arthroscopic group.Low-quality evidence suggests there may be little difference in pain and function at 12 months follow-up in people who have arthroscopic partial meniscectomy and those who have physical therapy. Evidence was downgraded to low quality due to risk of bias and imprecision.Mean pain was 19.3 points on a 0 to 100 point KOOS pain scale with physical therapy at 12 months follow-up and was 0.2 points better with surgery (95% confidence interval (CI) 4.05 better to 3.65 points worse with surgery, an absolute improvement of 0.2% (95% CI 4% better to 4% worse) and relative improvement 0.4% (95% CI 9% better to 8% worse) (low quality evidence). Mean function was 14.5 on a 0 to 100 point KOOS function scale with physical therapy at 12 months follow-up and 0.8 points better with surgery (95% CI 4.3 better to 2.7 worse); 0.8% absolute improvement (95% CI 4% better to 3% worse) and 2.1% relative improvement (95% CI 11% better to 7% worse) (low quality evidence).Radiographic structural osteoarthritis progression and quality of life outcomes were not reported.Due to very low quality evidence, we are uncertain if surgery is associated with an increased risk of serious adverse events, incidence of total knee replacement or withdrawal rates. Evidence was downgraded twice due to very low event rates, and once for risk of bias.At 12 months, the surgery group had a total of three serious adverse events including fatal pulmonary embolism, myocardial infarction and hypoxaemia. The physical therapy alone group had two serious adverse events including sudden death and stroke (Peto OR 1.58, 95% CI 0.27 to 9.21); 1% more events with surgery (95% CI 2% less to 3% more) and 58% relative change (95% CI 73% less to 821% more). One participant in each group withdrew due to adverse events.Two of 164 participants (1.2%) in the physical therapy group and three of 156 in the surgery group underwent conversion to total knee replacement within 12 months (Peto OR 1.76, 95% CI 0.43 to 7.13); 1% more events with surgery (95% CI 2% less to 5% more); 76% relative change (95% CI 57% less to 613% more). AUTHORS' CONCLUSIONS: The review found no placebo-or sham-controlled trials of surgery in participants with symptomatic mild to moderate knee osteoarthritis. There was low quality evidence that there may be no evidence of a difference between arthroscopic partial meniscectomy surgery and a home exercise program for the treatment of this condition. Similarly, low-quality evidence from a few small trials indicates there may not be any benefit of arthroscopic surgery over other non-surgical treatments including saline irrigation and hyaluronic acid injection, or one type of surgery over another. We are uncertain of the risk of adverse events or of progressing to total knee replacement due to very small event rates. Thus, there is uncertainty around the current evidence to support or oppose the use of surgery in mild to moderate knee osteoarthritis. As no benefit has been demonstrated from the low quality trials included in this review, it is possible that future higher quality trials for these surgical interventions may not contradict these results.

Temporal trends and regional variation in the rate of arthroscopic knee surgery in England: analysis of over 1.7 million procedures between 1997 and 2017. Has practice changed in response to new evidence?

OBJECTIVES: We investigated trends and regional variation in the rate of arthroscopic knee surgery performed in England from 1997-1998 to 2016-2017. DESIGN: Cross-sectional study of the national hospital episode statistics (HES) for England. METHODS: All hospital episodes for patients undergoing a knee arthroscopy between 1 April 1997 and 31 March 2017 were extracted from HES by procedure code. Age and sex-standardised rates of surgery were calculated using Office for National Statistic population data as the denominator. Trends in the rate of surgery were analysed by procedure both nationally and by Clinical Commissioning Group (CCG). RESULTS: A total of 1 088 872 arthroscopic partial meniscectomies (APMs), 326 600 diagnostic arthroscopies, 308 618 knee washouts and 252 885 chondroplasties were identified (1 759 467 hospital admissions; 1 447 142 patients). The rate of APM increased from a low of 51/100 000 population (95% CI 51 to 52) in 1997-1998 to a peak at 149/100 000 (95% CI 148 to 150) in 2013-2014; then, after 2014-2015, rates declined to 120/100 000 (95% CI 119 to 121) in 2016-2017. Rates of arthroscopic knee washout and diagnostic arthroscopy declined steadily from 50/100 000 (95% CI 49 to 50) and 47/100 000 (95% CI 46 to 47) respectively in 1997-1998, to 4.8/100 000 (95% CI 4.6 to 5.0) and 8.1/100 000 (95% CI 7.9 to 8.3) in 2016-2017. Rates of chondroplasty have increased from a low of 3.2/100 000 (95% CI 3.0 to 3.3) in 1997-1998 to 51/100 000 (95% CI 50.6 to 51.7) in 2016-2017. Substantial regional and age-group variation in practice was detected. In 2016-2017, between 11% (22/207) and 16% (34/207) of CCGs performed at least double the national average rate of each procedure. CONCLUSIONS: Over the last 20 years, and likely in response to new evidence, rates of arthroscopic knee washout and diagnostic arthroscopy have declined by up to 90%. APM rates increased about 130% overall but have declined recently. Rates of chondroplasty increased about 15-fold. There is significant variation in practice, but the appropriate population intervention rate for these procedures remains unknown.

Accuracy of a New Robotically Assisted Technique for Total Knee Arthroplasty: A Cadaveric Study.

BACKGROUND: Although the utility of robotic surgery has already been proven in cadaveric studies, it is our hypothesis that this newly designed robotically assisted system will achieve a high level of accuracy for bone resection. Therefore, we aimed to analyze in a cadaveric study the accuracy to achieve targeted angles and resection thickness. METHODS: For this study, 15 frozen cadaveric specimens (30 knees) were used. In this study, Zimmer Biomet (Warsaw, IN) knees, navigation system, and robot (ROSA Knee System; Zimmer Biomet) were used. Eight trained, board-certified orthopedic surgeons performed robotically assisted total knee arthroplasty implantation using the same robotic protocol with 3 different implant designs. The target angles obtained from the intraoperative planning were then compared to the angles of the bone cuts performed using the robotic system and measured with the computer-assisted system considered to be the gold standard. For each bone cut the resection thickness was measured 3 times by 2 different observers and compared to the values for the planned resections. RESULTS: All angle mean differences were below 1° and standard deviations below 1°. For all 6 angles, the mean differences between the target angle and the measured values were not significantly different from 0 except for the femoral flexion angle which had a mean difference of 0.95°. The mean hip-knee-ankle axis difference was -0.03° ± 0.87°. All resection mean differences were below 0.7 mm and standard deviations below 1.1mm. CONCLUSION: Despite the fact that this study was funded by Zimmer Biomet and only used Zimmer Biomet implants, robot, and navigation tools, the results of our in vitro study demonstrated that surgeons using this new surgical robot in total knee arthroplasty can perform highly accurate bone cuts to achieve the planned angles and resection thickness as measured using conventional navigation.

Rates of knee arthroplasty in anterior cruciate ligament reconstructed patients: a longitudinal cohort study of 111,212 procedures over 20 years.

Background and purpose - Long-term rates of knee arthroplasty in patients with anterior cruciate ligament (ACL) injury who undergo ligament reconstruction (ACLr) are unclear. We determined this risk of arthroplasty through comparison with the general population.Patients and methods - All patients undergoing an ACLr in England, 1997-2017, were identified from national hospital statistics. Patients subsequently undergoing a knee arthroplasty were identified and survival analysis was performed (survival without undergoing knee arthroplasty). A Cox proportional hazards model was used to identify factors associated with knee arthroplasty. Relative risk of knee arthroplasty (total or partial) in comparison with the general population was determined.Results - 111,212 ACLr patients were eligible for analysis (mean age 29; 77% male). Overall, 0.46% (95% confidence interval [CI] 0.40-0.52) ACLr patients underwent knee arthroplasty within 5 years, 0.97% (CI 0.82-1.2) within 10 years, and 1.8% (CI 1.4-2.3) within 15 years. Knee arthroplasty risk was greater in older age groups and women. In comparison with the general population, the relative risk of undergoing arthroplasty at a younger age (at time of arthroplasty) was elevated: at 30-39 years (risk ratio [RR] 20; CI 11-35), 40-49 years (RR 7.5; CI 5.5-10), and 50-59 years (RR 2.5; CI 1.8-3.5), but not 60-69 years (RR 1.7; CI 0.93-3.2).Interpretation - Patients sustaining an ACL injury who undergo ACLr are at elevated risk of subsequent knee arthroplasty in comparison with the general population. Although the absolute rate of arthroplasty is low, the risk of arthroplasty at a younger age is particularly elevated. When the outcome of shared decision-making is ACLr, this data will help inform patients and clinicians about the long-term risk of requiring knee arthroplasty.

The effect of patient age at intervention on risk of implant revision after total replacement of the hip or knee: a population-based cohort study.

BACKGROUND: Total joint replacements for end-stage osteoarthritis of the hip and knee are cost-effective and demonstrate significant clinical improvement. However, robust population based lifetime-risk data for implant revision are not available to aid patient decision making, which is a particular problem in young patient groups deciding on best-timing for surgery. METHODS: We did implant survival analysis on all patients within the Clinical Practice Research Datalink who had undergone total hip replacement or total knee replacement. These data were adjusted for all-cause mortality with data from the Office for National Statistics and used to generate lifetime risks of revision surgery based on increasing age at the time of primary surgery. FINDINGS: We identified 63 158 patients who had undergone total hip replacement and 54 276 who had total knee replacement between Jan 1, 1991, and Aug 10, 2011, and followed up these patients to a maximum of 20 years. For total hip replacement, 10-year implant survival rate was 95·6% (95% CI 95·3-95·9) and 20-year rate was 85·0% (83·2-86·6). For total knee replacement, 10-year implant survival rate was 96·1% (95·8-96·4), and 20-year implant survival rate was 89·7% (87·5-91·5). The lifetime risk of requiring revision surgery in patients who had total hip replacement or total knee replacement over the age of 70 years was about 5% with no difference between sexes. For those who had surgery younger than 70 years, however, the lifetime risk of revision increased for younger patients, up to 35% (95% CI 30·9-39·1) for men in their early 50s, with large differences seen between male and female patients (15% lower for women in same age group). The median time to revision for patients who had surgery younger than age 60 was 4·4 years. INTERPRETATION: Our study used novel methodology to investigate and offer new insight into the importance of young age and risk of revision after total hip or knee replacement. Our evidence challenges the increasing trend for more total hip replacements and total knee replacements to be done in the younger patient group, and these data should be offered to patients as part of the shared decision making process. FUNDING: Oxford Musculoskeletal Biomedical Research Unit, National Institute for Health Research.

Medial meniscal extrusion: a validation study comparing different methods of assessment.

PURPOSE: Longitudinal cohort studies of knee OA aetiology use MRI to assess meniscal extrusion within the same knee at sequential time points. A validated method of assessment is required to ensure that extrusion is measured at the same location within the knee at each time point. Absolute perpendicular extrusion from the tibial edge can be assessed using the reference standard of segmentation of the tibia and medial meniscus. This is labour intensive and unsuitable for large cohorts. Two methods are commonly used as proxy measurements. Firstly, the apex of the medial tibial spine is used to identify a reproducible MRI coronal slice, from which extrusion is measured. Secondly, the coronal MRI slice of the knee demonstrating the greatest extrusion is used. The purpose of this study was to validate these two methods against the reference standard and to determine the most appropriate method to use in longitudinal cohort studies. We hypothesised that there is no difference in absolute meniscal extrusion measurements between methods. METHODS: Twenty high-resolution knee MRI scans were obtained in asymptomatic subjects. The tibia and medial meniscus were manually segmented. A custom MATLAB program was used to determine the difference in medial meniscal extrusion of the knee using the reference standard compared to the two other methods. RESULTS: Assessing extrusion using the single coronal MRI slice demonstrating the greatest extrusion overestimates the true extrusion of the medial meniscus. It incorrectly places the greatest meniscal extrusion at the anterior part of the tibia. Assessing extrusion using a consistent anatomical landmark, such as the medial tibial spine, most reliably corresponds to the reference of segmentation and measurement of true perpendicular extrusion from the tibial edge. Clinicians and researchers should consider this when assessing meniscal extrusion in the knee, and how it changes over time. CONCLUSION: This study suggests measuring meniscal extrusion on the coronal MRI slice corresponding to the apex of the medial tibial spine as this correlates most closely with the true perpendicular extrusion measurements obtained from manually segmented models. LEVEL OF EVIDENCE: Diagnostic, Level I.

The impact of patient-specific instrumentation on unicompartmental knee arthroplasty: a prospective randomised controlled study.

PURPOSE: Patient-specific instrumentation (PSI) has been proposed as a means of improving surgical accuracy and ease of implantation during technically challenging procedures such as unicompartmental knee arthroplasty (UKA). The purpose of this prospective randomised controlled trial was to compare the accuracy of implantation and functional outcome of mobile-bearing medial UKAs implanted with and without PSI by experienced UKA surgeons. METHODS: Mobile-bearing medial UKAs were implanted in 43 patients using either PSI guides or conventional instrumentation. Intra-operative measurements, meniscal bearing size implanted, and post-operative radiographic analyses were performed to assess component positioning. Functional outcome was determined using the Oxford Knee Score (OKS). RESULTS: PSI guides could not be used in three cases due to concerns regarding accuracy and registration onto native anatomy, particularly on the tibial side. In general, similar component alignment and positioning was achieved using the two systems (n.s. for coronal/sagittal alignment and tibial coverage). The PSI group had greater tibial slope (p = 0.029). The control group had a higher number of optimum size meniscal bearing inserted (95 vs 52%; p = 0.001). There were no differences in OKS improvements (n.s). CONCLUSION: Component positioning for the two groups was similar for the femur but less accurate on the tibial side using PSI, often with some unnecessarily deep resections of the tibial plateau. Although PSI was comparable to conventional instrumentation based on OKS improvements at 12 months, we continue to use conventional instrumentation for UKA at our institution until further improvements to the PSI guides can be demonstrated. LEVEL OF EVIDENCE: Therapeutic, Level I.