Multi-center experience with outpatient total hip arthroplasty via a standard posterolateral approach.

BACKGROUND: This study sought to evaluate the safety, efficacy, and resource utilization of a pilot outpatient surgery program for total hip arthroplasty compared to traditional inpatient total hip arthroplasty performed via the posterolateral approach. METHODS: A cohort of 68 patients from two sites were enrolled in a regional pilot project for outpatient total hip arthroplasty (THA) and matched 1:1 against a cohort of patients undergoing routine inpatient THA. Data was extracted retrospectively from patient and hospital charts including adverse events (AE), readmission within 90 days, emergency room (ER) visits, patient calls, patient-reported outcome measures, length of stay, and multiple surgical variables. RESULTS: The outpatient group had a mean hospital stay of 13 hours, whereas the inpatient group had a mean of 58 hours (p<0.001). Three outpatients and four inpatients experienced post-op complications. Three inpatients and one outpatient visited the ER within 8 weeks of surgery. No difference in pre-operative hemoglobin (p = 0.210), or surgical blood loss (p = 0.550) was found between study groups. There was no difference found between groups regarding Oxford-12 Hip Score improvement, nor satisfaction at six months, one and two years (p>0.125). CONCLUSION: This study demonstrates that outpatient THA using the posterolateral approach is as safe and effective as inpatient THA for overall healthy and carefully screened patients, based on the low rate of AEs observed and similar patient outcomes reported. Significantly reduced time in hospital demonstrates the reduced healthcare resources associated with outpatient THA.

Randomized controlled trial comparing traditional versus enhanced-fixation designs of a novel cemented total knee arthroplasty tibial component.

Aims: A novel enhanced cement fixation (EF) tibial implant with deeper cement pockets and a more roughened bonding surface was released to market for an existing total knee arthroplasty (TKA) system.This randomized controlled trial assessed fixation of the both the EF (ATTUNE S+) and standard (Std; ATTUNE S) using radiostereometric analysis. Methods: Overall, 50 subjects were randomized (21 EF-TKA and 23 Std-TKA in the final analysis), and had follow-up visits at six weeks, and six, 12, and 24 months to assess migration of the tibial component. Low viscosity bone cement with tobramycin was used in a standardized fashion for all subjects. Patient-reported outcome measure data was captured at preoperative and all postoperative visits. Results: The patient cohort mean age was 66 years (SD seven years), 59% were female, and the mean BMI was 32 kg/m2 (SD 6 kg/m2). Mean two-year subsidence of the EF-TKA was 0.056 mm (95% confidence interval (CI) 0.025 to 0.086) versus 0.006 mm (95% CI -0.029 to 0.040) for the Std-TKA, and the two-year maximum total point motion (MTPM) was 0.285 mm (95% upper confidence limit (UCL) ≤ 0.363) versus 0.346 mm (95% UCL ≤ 0.432), respectively, for a mean difference of -0.061 mm (95% CI -0.196 to 0.074). Inducible displacement also did not differ between groups. The MTPMs between 12 and 24 months for each group was below the published threshold of 0.2 mm for predicting early aseptic loosening (p < 0.001 and p = 0.001, respectively). Conclusion: Both the enhanced fixation and the standard tibial implant design showed fixation with a predicted low risk of long-term aseptic loosening.

Comparison of two hydroxyapatite-coated femoral components: a randomized clinical trial using radiostereometric analysis.

Aims: The primary aim of this trial was to compare the subsidence of two similar hydroxyapatite-coated titanium femoral components from different manufacturers. Secondary aims were to compare rotational migration (anteversion/retroversion and varus/valgus tilt) and patient-reported outcome measures between both femoral components. Methods: Patients were randomized to receive one of the two femoral components (Avenir or Corail) during their primary total hip arthroplasty between August 2018 and September 2020. Radiostereometric analysis examinations at six, 12, and 24 months were used to assess the migration of each implanted femoral component compared to a baseline assessment. Patient-reported outcome measures were also recorded for these same timepoints. Overall, 50 patients were enrolled (62% male (n = 31), with a mean age of 65.7 years (SD 7.3), and mean BMI of 30.2 kg/m2 (SD 5.2)). Results: The two-year subsidence was similar for Avenir (-0.018 mm (95% confidence interval (CI) -0.053 to 0.018) and Corail (0.000 mm (95% CI -0.027 to 0.026; p = 0.428). Both anteversion/retroversion (Avenir 0.139° (95% CI -0.204 to 0.481°); Corail -0.196° (95% CI -0.445 to 0.053°; p = 0.110) and varus/valgus tilt (Avenir -0.024° (95% CI -0.077 to 0.028); Corail -0.049° (95% CI -0.098 to 0.000°; p = 0.473) were not statistically significantly different. After two years, patients reported similar improvements in EuroQol five-dimension five-level health questionnaire (Avenir 0.22 (SD 0.2); Corail 0.22 (SD 0.18); p = 0.965) and other outcomes scores. Patient satisfaction on a five-point Likert scale was also similar between both groups after two years (Avenir 1.38 (SD 0.88); Corail 1.33 (SD 0.57); p = 0.846). Conclusion: The performance of both femoral components was similar in terms of stability and patient outcomes.

Radiostereometric analysis and clinical outcomes of a novel reverse total hip system at two years.

Aims: Instability is a common cause of failure after total hip arthroplasty. A novel reverse total hip has been developed, with a femoral cup and acetabular ball, creating enhanced mechanical stability. The purpose of this study was to assess the implant fixation using radiostereometric analysis (RSA), and the clinical safety and efficacy of this novel design. Methods: Patients with end-stage osteoarthritis were enrolled in a prospective cohort at a single centre. The cohort consisted of 11 females and 11 males with mean age of 70.6 years (SD 3.5) and BMI of 31.0 kg/m2 (SD 5.7). Implant fixation was evaluated using RSA as well as Western Ontario and McMaster Universities Osteoarthritis Index, Harris Hip Score, Oxford Hip Score, Hip disability and Osteoarthritis Outcome Score, 38-item Short Form survey, and EuroQol five-dimension health questionnaire scores at two-year follow-up. At least one acetabular screw was used in all cases. RSA markers were inserted into the innominate bone and proximal femur with imaging at six weeks (baseline) and six, 12, and 24 months. Independent-samples t-tests were used to compare to published thresholds. Results: Mean acetabular subsidence from baseline to 24 months was 0.087 mm (SD 0.152), below the critical threshold of 0.2 mm (p = 0.005). Mean femoral subsidence from baseline to 24 months was -0.002 mm (SD 0.194), below the published reference of 0.5 mm (p < 0.001). There was significant improvement in patient-reported outcome measures at 24 months with good to excellent results. Conclusion: RSA analysis demonstrates excellent fixation with a predicted low risk of revision at ten years of this novel reverse total hip system. Clinical outcomes were consistent with safe and effective hip replacement prostheses.

Modes of failure of hip hemiarthroplasty for femoral neck fracture.

BACKGROUND: Hemiarthroplasty is a common treatment for displaced femoral neck fractures, but limited Canadian data are available about hemiarthroplasty failure. We evaluated the frequency and predictors of hemiarthroplasty failure in Manitoba. METHODS: In this retrospective multicentre province-wide study, billing and joint registry databases showed 4693 patients who had hemiarthroplasty for treatment of femoral neck fracture in Manitoba over an 11-year period (2005-2015), including 155 hips with subsequent reoperations (open or closed) for treatment of hemiarthroplasty failure. Hospital records were reviewed to identify modes of hemiarthroplasty failure, comorbidities and reoperations. Data were analyzed using χ2 test and Poisson and γ regression models. RESULTS: During our study period, 155 hips (154 patients [3%]) underwent 230 reoperations. Of these, 131 hips (85%) initially had an uncemented unipolar modular implant. Indications for first-time reoperation included periprosthetic femur fracture (49 hips [32%]), dislocation (45 hips [29%]), acetabular wear (28 hips [18%]) and infection (26 hips [17%]). There were 46 hips (30%) that had 2 or more reoperations. Reoperation for dislocation was associated with presence of dementia; acetabular wear was associated with absence of dementia. Time from hemiarthroplasty to reoperation was associated inversely with age at hemiarthroplasty, dislocation and dementia and was directly associated with acetabular wear. The risk of having 2 or more reoperations was associated independently with dislocation, infection, and alcohol abuse. CONCLUSION: Hemiarthroplasty for femoral neck fracture in Manitoba had a low frequency of failure. Risk factors for multiple reoperations included dislocation, infection and alcohol abuse.

Prospective randomized trial of continuous femoral nerve block with posterior capsular injection versus periarticular injection for analgesia in primary total knee arthroplasty.

Background: Femoral nerve block (NB) and periarticular injection (PI) are 2 common options for pain control after total knee arthroplasty (TKA). We performed a prospective triple-blinded randomized trial comparing continuous femoral NB to PI, with follow-up to 1 year. Methods: Patients younger than 70 years of age who were scheduled to undergo elective primary TKA under spinal anesthesia between 2009 and 2010 were randomly allocated to receive either continuous femoral NB or PI. Patients in the NB group received ropivacaine through an NB catheter and a sham saline PI. The PI group received a PI of ropivacaine, morphine, ketorolac and epinephrine, and a sham saline infusion via an NB catheter. Both groups had standardized oral analgesia preoperatively, spinal anesthesia and sedation, and postoperative analgesia. Surgeons, anesthesiologists, patients and assessors were blinded to group assignment. Pain was measured twice daily on postoperative days 1 and 2, at rest and with motion, with a numeric rating scale. Patient satisfaction, pain (Oxford Knee Score) and range of motion were assessed at 1 year. Results: There were 39 participants in the NB group and 35 participants in the PI group. There were no statistically significant differences between the groups at baseline. Statistically but nonclinically significant reductions in pain scores on postoperative day 2 and in narcotic need on the day of surgery were found in the PI group. Patient-reported satisfaction did not differ at any time point. At 1 year, knee flexion was significantly greater in the NB group than in the PI group (mean range of motion 120° v. 110°, p = 0.03). Conclusion: There was no demonstrated improvement in pain control with the use of an NB versus PI when used with multimodal analgesia. Clinicians should opt for the modality that has the best efficiency for their surgical environment. ClinicalTrials.gov # NCT00869037

Contexte: Le bloc nerveux (BN) fémoral et l'infiltration périarticulaire (IP) sont 2 options d'usage courant pour maîtriser la douleur après l'arthroplastie totale du genou (ATG). Nous avons procédé à un essai prospectif randomisé à triple insu afin de comparer le BN fémoral et l'IP, avec un suivi allant jusqu'à 1 an. Méthodes: Les patients de moins de 70 ans qui devaient subir une ATG élective sous épidurale entre 2009 et 2010 ont été assignés aléatoirement à un BN fémoral continu ou à une IP. Les patients du groupe soumis au BN recevaient de la ropivacaïne par un cathéter de BN et une IF simulée (solution saline). Le groupe soumis à l'IP recevait de la ropivacaïne, de la morphine, du kétorolac et de l'épinéphrine et une perfusion simulée (solution saline) par un cathéter de BN. Les 2 groupes avaient reçu une analgésie orale standard avant l'intervention, une anesthésie rachidienne avec sédatifs et une analgésie postopératoire. Les chirurgiens, les anesthésiologistes, les patients et les évaluateurs ne connaissaient pas l'assignation des agents aux différents groupes. La douleur a été mesurée 2 fois par jour aux jours 1 et 2 postopératoires, au repos et à la mobilisation, au moyen d'une échelle numérique. La satisfaction des patients, la douleur (questionnaire d'Oxford pour le genou) et l'amplitude de mouvement ont toutes été évaluées après 1 an. Résultats: Le groupe soumis au BN comptait 39 participants et le groupe soumis à l'IP en comptait 35. Il n'y avait aucune différence statistiquement significative entre les groupes au départ. Des réductions statistiquement (et non cliniquement) significatives des scores de douleur au deuxième jour postopératoire et du recours aux narcotiques le jour de la chirurgie ont été notées dans le groupe soumis à l'IP. La satisfaction autodéclarée des patients n'a différé à aucun moment. Au bout de 1 an, la flexion du genou était significativement plus marquée dans le groupe soumis au BN que dans le groupe soumis à l'IP (amplitude de mouvement moyenne 120° c. 110°, p = 0,03) Conclusion: On n'a démontré aucune amélioration de la maîtrise de la douleur avec l'utilisation du BN c. IP avec analgésie multimodale. Les médecins devraient opter pour la modalité qui offre le meilleur degré d'efficience en fonction de leur environnement chirurgical. ClinicalTrials.gov # NCT00869037

Survivorship of constrained polyethylene inserts in primary total knee replacements.

BACKGROUND: Varus-valgus constrained (VVC) inserts are used in primary total knee arthroplasty (TKA) when stability cannot be achieved with a traditional insert. Concern has been raised regarding premature loosening and failure of these primary TKAs due to the increased load transfer through the prosthesis. This study seeks to assess the survival, clinical outcomes and radiographic assessment of VVC total knee inserts used in a single primary TKA system without diaphyseal stem extensions. METHODS: A consecutive cohort of 74 primary TKAs with VVC inserts was identified from an institutional database. A two-to-one matched group of 136 posterior-stabilized (PS) primary TKAs was generated from the same database. Survival analysis was assessed for all-cause revision surgery. Patient outcome measures were the Oxford Knee Score (OKS) and patient reported satisfaction. Radiographs were assessed in accordance with the Knee Society radiographic scoring system for radiolucency. RESULTS: Survival rates at three and five years were 98.1% and 95.1% for the VVC liner group and 98.1% and 98.1% for the PS liner group, respectively. OKS improved from pre-op to post-op for both groups (p < .001). OKS was reduced in the VVC liner group compared to the PS liner group at latest available follow-up (p = .012). However, clinical satisfaction rates did not differ between the two groups. Small, non-progressive radiolucent lines existed on several radiographs; however, no components in either group were deemed radiographically loose. CONCLUSION: The survivorship, clinical, and radiographic outcomes of VVC knees were similar to the PS comparison group at short- to mid-term follow-up.

Guided-motion hinged knee replacement prosthesis: early survival rate and postoperative patient function and satisfaction.

Background: Literature on the survival rates and function of hinged total knee replacement (HTKR) prostheses is scarce, and to our knowledge there is not yet any published literature on the Legion HK Hinge Knee Replacement prosthesis (Smith & Nephew) with guided-motion articulation. The objective of this study was to establish the early survival rate of this modern HTKR at a single institution and to investigate postoperative patient function and satisfaction. Methods: This retrospective study included patients who received the Legion HTKR prosthesis with guided-motion inserts as a primary or revision implant between October 11 and March 2016 at a tertiary care centre in Manitoba, Canada. Preoperative and postoperative functional scores on the 12-item Oxford Knee Score and postoperative patient satisfaction were assessed. Results: Thirty-nine HTKR implantations (38 patients) were included in this study: 12 primary cases and 27 revision cases. Three revision surgeries and 4 perioperative complications were noted at a mean follow-up of 29.1 months. The 2-year survivorship of the HTKR system was 90.7%. Postoperative functional scores improved significantly and the majority of patients were satisfied or very satisfied at all follow-up time points. Conclusion: The early survival rate of a modern guided-motion HTKR prosthesis is similar to the survival rates of other hinged knee prostheses published in the literature. The prosthesis demonstrated substantial postoperative functional improvement when used in the setting of complex primary or revision total knee replacement.

Contexte: Il existe peu d'études sur le taux de survie et la fonction des prothèses totales de genou (PTG) à charnière, et, à notre connaissance, il n'y a pas encore d'étude publiée sur la prothèse Legion HK Hinge Knee (Smith & Nephew), qui guide le mouvement de l'articulation. Cette étude visait à déterminer le taux de survie à 2 ans de cette PTG à charnière moderne dans un seul établissement et à évaluer la fonction du genou et la satisfaction des patients après l'opération. Méthodes: Cette étude rétrospective portait sur des patients qui avaient reçu la PTG Legion HK guidant le mouvement lors d'une première opération ou d'une chirurgie de révision entre octobre 2011 et mars 2016 dans un centre de soins tertiaires du Manitoba, au Canada. On a évalué la fonction préopératoire et postopératoire du genou à l'aide du score Oxford d'évaluation du genou à 12 questions ainsi que la satisfaction des patients après l'opération. Résultats: Trente-neuf arthroplasties totales du genou (38 patients) ont été retenues pour l'étude : 12 cas de première opération et 27 chirurgies de révision. En tout, 3 chirurgies de révision et 4 complications périopératoires ont été notées lors d'une consultation de suivi se déroulant en moyenne à 29,1 mois. Le taux de survie à 2 ans de la PTG à charnière Legion HK était de 90,7 %. Les scores de fonction du genou se sont grandement améliorés après l'opération, et la majorité des patients se sont dit satisfaits ou très satisfaits lors de tous les suivis. Conclusion: Le taux de survie d'une PTG à charnière moderne guidant le mouvement est similaire à celui des autres prothèses à charnière étudiées dans la littérature. La prothèse a permis une amélioration fonctionnelle importante après l'opération lorsqu'elle était utilisée dans le cadre d'une première arthroplastie totale du genou complexe ou d'une chirurgie de révision.

Midterm Results of a Contemporary, Porous-Coated Acetabular System in Patients Undergoing Primary Total Hip Replacement for Degenerative Hip Disease: A Prospective, Multicenter Study.

BACKGROUND: A contemporary, porous-coated acetabular implant designed for uncemented insertion was introduced in Europe and Australia in 2007. A similar previous acetabular system was found in several studies at 10 to 15-year follow-up to demonstrate accelerated polyethylene wear, osteolysis, and early failure. The current study was conducted to determine the midterm safety and effectiveness of this contemporary acetabular system using highly crosslinked polyethylene and ceramic liners at 5-year follow-up. METHODS: A prospective, nonrandomized study was conducted at 8 sites in Canada and the United States. All 148 study participants received a contemporary acetabular shell with proprietary porous coating. The primary outcome was the requirement for revision surgery at 5 years postoperatively. Secondary outcomes included a survival analysis, patient-reported outcome measures, radiographic failure, and postoperative adverse events. RESULTS: At 5-year follow-up there was 1 cup revised for deep infection. No cups were revised for loosening and none were found to be radiographically loose. The overall survival rate with reoperation for any reason was 97.1%. The success rate was 96.8% for polyethylene and 100% for ceramic with no difference in the success rate between either bearing surface (P = 1.0). The mean patient-reported outcome measures all improved significantly between preoperative and 5-year postoperative scores (P < .001). CONCLUSION: Results from this 5-year, multicenter, prospective study indicate excellent survivorship for this acetabular system when used with crosslinked polyethylene or ceramic bearing surfaces.

A double-blind randomized controlled trial of total knee replacement using patient-specific cutting block instrumentation versus standard instrumentation

Background: Patient-specific cutting blocks in total knee arthroplasty have been promoted to improve mechanical alignment, reduce alignment outliers and improve patient outcomes. The aim of this study was to compare the efficacy of patient-specific instrumentation (PSI) and conventional instrumentation (CI) in achieving neutral alignment and accurate component positioning in total knee arthroplasty. Methods: We conducted a double-blinded randomized controlled trial in which patients were randomly assigned to treatment with either PSI or CI. Results: Fifty-four patients were included in the study. No relevant improvement in coronal alignment was found between the PSI and CI groups with post-hoc power of 0.91. Tibial slope was found to be more accurately reproduced to the preoperative target of 3° with PSI than with CI (3.8°± 3.1° v. 7.7°± 3.6°, respectively, p < 0.001). There were no differences found in patient-reported outcome measures, surgical time or length of hospital stay. Conclusion: Given the added cost of the PSI technique, its use is difficult to justify given the small improvement in only a single alignment parameter. Clinical trial registration: Clinicaltrials.gov, no. NCT03416946

Contexte: L'utilisation de guides de coupe sur mesure dans l'arthroplastie totale du genou a été recommandée pour améliorer l'alignement mécanique, réduire les alignements extrêmes et améliorer les résultats des patients. Cette étude cherchait à comparer la capacité des instruments sur mesure et des instruments classiques à engendrer un alignement neutre et un bon positionnement des composants dans le cadre d'une arthroplastie totale du genou. Méthodes: Nous avons mené un essai clinique randomisé à double insu. Les patients étaient répartis aléatoirement entre le groupe de traitement avec instruments sur mesure et le groupe de traitement avec instruments classiques. Résultats: Cinquante-quatre patients ont participé à l'étude. Aucune différence notable de l'alignement coronal entre les groupes n'a été relevée, pour une puissance observée de 0,91. La pente tibiale correspondait plus exactement à la cible préopératoire de 3° avec les instruments sur mesure qu'avec les instruments classiques (3,8° ± 3,1° contre 7,7° ± 3,6°, respectivement; p < 0,001). Il n'y avait aucune différence dans les mesures déclarées par les patients, la durée de l'intervention et la durée d'hospitalisation. Conclusion: Étant donné l'amélioration minime d'un seul paramètre d'alignement et le coût supérieur de la technique sur mesure, son utilisation est difficile à justifier. Enregistrement de l'essai: Clinicaltrials.gov, no NCT03416946.

In vivo wear measurement in a modern total knee arthroplasty with model-based radiostereometric analysis.

AIMS: A retrospective study was conducted to measure short-term in vivo linear and volumetric wear of polyethylene (PE) inserts in 101 total knee arthroplasty (TKA) patients using model-based radiostereometric analysis (MBRSA). PATIENTS AND METHODS: Nonweightbearing supine RSA exams were performed postoperatively and at six, 12, and 24 months. Weightbearing standing RSA exams were performed on select patients at 12 and 24 months. Wear was measured both linearly (joint space) and volumetrically (digital model overlap) at each available follow-up. Precision of both methods was assessed by comparing double RSA exams. Patient age, sex, body mass index, and Oxford Knee Scores were analyzed for any association with PE wear. RESULTS: Linear wear occurred at 0.015 mm/year (supine) and 0.220 mm/year (standing). Volumetric wear occurred at 10.3 mm3/year (supine) and 39.3 mm3/year (standing). Wear occurred primarily on the medial side of the joint. Weightbearing imaging greatly improved the reliability of measurement. Clinical precision of volumetric wear was 34 mm3. No significant associations were found between patient demographics or function scores and measured wear. CONCLUSION: In vivo volumetric wear of TKAs can be assessed at short-term follow-up using MBRSA. Cite this article: Bone Joint J 2019;101-B:1348-1355.

Mid-term progressive loosening of hydroxyapatite-coated femoral stems paired with a metal-on-metal bearing.

BACKGROUND: Several hydroxyapatite (HA)-coated femoral stems from a single manufacturer were identified to have aseptically loosened at mid-term follow-up despite prior radiographic appearance of osseointegration. Possible causes and associated risk factors for stem loosening were explored through radiographic review and implant retrieval analysis. METHODS: Forty-six retrieved hip stems (Corail, DePuy-Synthes) were identified and grouped by bearing type: metal-on-metal (MoM), metal-on-polyethylene, and ceramic-on-ceramic. Stem lucency was graded on post-operative radiographs up to the time of revision. Stems were examined for stripping of the HA coating, taper corrosion, and bearing wear in metal-on-metal cases. Patient demographics, implant design features, and perioperative data were collected from electronic databases and patient charts. RESULTS: Aseptic loosening occurred in 37% of cases examined. MoM bearings were associated with 7.25 times greater risk of loosening compared to other bearing types. Stem radiolucency was more prevalent for MoM cases and, although not statistically significant, demonstrated progressive lucency. Taper corrosion appeared more severe for MoM cases and correlated with proximal stem radiolucency. Removal of the HA coating from the stems was associated with both taper corrosion and MoM bearing wear. Length of implantation was a confounding factor for the MoM cases. CONCLUSION: This study has demonstrated a high risk of mid-term loosening of previously osseointegrated HA-coated femoral stems when paired with a MoM bearing. The mechanism of loosening appears progressive in nature and related to the MoM bearing, possibly interacting with the HA coating. If such loosening is recognized early, rapid revision may allow for retention of the femoral stem.

Does oxidized zirconium make a difference? Midterm cohort survivorship of symmetric posterior condyle posterior-stabilized total knee arthroplasty

Background: A novel symmetric posterior condylar design and option of a femoral component with an outer zirconium oxide layer were introduced to a successful asymmetric condylar total knee arthroplasty system in 2005. Given the paucity of information on this modified design, we performed a study to determine its early to midterm survivorship and performance. Methods: Patients who received the Genesis II Symmetric Posterior Condyle or Legion Primary total knee (cobalt­chromium [CoCr] or oxidized zirconium­niobium [OxZr]) (Smith & Nephew) implanted at the study centre between March 2007 and December 2013 were enrolled into a prospective database. We retrospectively reviewed the database and performed survival analysis using Kaplan­Meier techniques. Results: There were 2178 patients (1359 women [62.4%]; mean age 64.6 yr; mean body mass index 35.0) with 2815 knee replacements available for analysis. Survival rates were 98.2% (95% confidence interval [CI] 97.6%­98.7%) for failure for any reason at 2 years and 96.8% (95% CI 96.0%­97.7%) at 5 years. Age (hazard ratio [HR] 0.97, 95% CI 0.94­0.997) and female sex (HR 0.45, 95% CI 0.27­0.75) were protective, whereas body mass index (HR 1.02, 95% CI 0.99­1.05) and OxZr implant (HR 1.11, 95% CI 0.57­2.18) did not influence survivorship. Oxford Knee Score values improved from a mean of 40.2 to 21.8 by 2 years (p < 0.001), with no difference between the CoCr and OxZr groups. Conclusion: The symmetric posterior condylar posterior-stabilized knee offers excellent midterm survivorship. Implant bearing surface did not have an influence on survivorship to 5 years, and, thus, use of OxZr implants may not be justified.

Contexte: Un nouveau modèle à condyles postérieurs symétriques et l'option d'un élément fémoral pourvu d'une couche d'oxyde de zirconium ont été introduits avec succès dans un système de prothèse totale du genou à condyles asymétriques en 2005. Compte tenu du manque de renseignements concernant ce modèle modifié, nous avons procédé à une étude pour en déterminer la survie et le rendement à court et à moyen terme. Méthodes: Les patients ayant reçu la prothèse à condyles postérieurs symétriques Genesis II ou une prothèse totale primaire Legion (au cobalt­chrome [CoCr] ou au zirconium­niobium oxydé [OxZr]) (Smith & Nephew) au centre de recherche entre mars 2007 et décembre 2013 ont été inscrits dans une base de données prospective. Nous avons procédé à une revue rétrospective de la base de données et effectué une analyse de survie à l'aide de techniques de Kaplan­Meier. Résultats: On a dénombré 2178 patients (dont 1359 femmes [62,4 %]; âge moyen 64,6 ans; indice de masse corporelle moyen 35,0) totalisant 2815 arthroplasties du genou pour analyse. Les taux de survie ont été de 98,2 % (intervalle de confiance [IC] à 95 % 97,6 %­98,7 %) pour le paramètre défaillance de toutes causes à 2 ans et de 96,8 % (IC à 95 % 96,0 %­97,7 %) à 5 ans. L'âge (risque relatif [RR] 0,97, IC à 95 % 0,94­0,997) et le fait d'être de sexe féminin (RR 0,45, IC à 95 % 0,27­0,75) ont conféré un effet protecteur, tandis que l'indice de masse corporelle (RR 1,02, IC à 95 % 0,99­1,05) et l'implant OxZr (RR 1,11, IC à 95 % 0,57­2,18) n'ont eu aucune influence sur la survie. Les scores Oxford d'évaluation du genou se sont améliorés, passant d'une moyenne de 40,2 à 21,8 en l'espace de 2 ans (p < 0,001), sans différence entre les groupes CoCr et OxZr. Conclusion: La prothèse du genou à condyles postérieurs symétriques postéro-stabilisée possède une excellente survie à moyen terme. La surface portant l'implant n'a pas eu d'influence sur la survie à 5 ans et, donc, l'utilisation d'implants OxZr ne sera peutêtre pas justifiée.

Clinical and radiographic outcomes of a hybrid fixation revision total knee arthroplasty system at short to mid-term follow-up.

BACKGROUND: Despite the extensive study of primary arthroplasty, revision surgery is rarely discussed due to the reduced frequency and variability between patients. A new revision knee system was introduced to build off the geometry of a successful knee replacement system. This study seeks to assess the survival, clinical outcomes and radiographic assessment of this revision system at the early to mid-term. METHODS: A consecutive cohort of 234 rTKAs was identified from an institutional database. Survival analysis was assessed for aseptic loosening and any-cause failure. Patient outcome measures were the Oxford Knee Score (OKS) and patient reported satisfaction. Radiographs were assessed in accordance with the Knee Society radiographic scoring system. Mechanical alignment was assessed on three-foot standing radiographs. RESULTS: Aseptic survivorship at one year, two years, and five years was 100%, 100%, and 99.1%, respectively. Any-cause survival at one, two, and five years was 99.6%, 98.7%, and 92.3%, respectively. OKS improved from pre-op (average 18.8) to one year (average 31.7), two years (average 30.7), and mid-term (average 30.6) follow-up (p < 0.001 for all). At all intervals, patient satisfaction exceeded 70%. One component (0.4%) failed radiographically and was later revised. Neutral mechanical alignment was achieved in 83% of cases. In the remaining cases, alignment was in varus (10%) or valgus (seven percent). No consistent relationship between radiographs or mechanical alignment and clinical outcomes was noted. CONCLUSION: The survivorship, clinical, and radiographic outcomes of the single rTKA system studied are equivalent or superior to other hybrid fixation rTKA systems reviewed in the literature at similar follow-up intervals.

Retrieval Analysis of Large-Head Modular Metal-on-Metal Hip Replacements of a Single Design.

BACKGROUND: There are limited publications examining modular metal-on-metal (MoM) total hip implants in which a comprehensive analysis of retrieved components is performed. This study examines 24 retrieved modular MoM implants from a single manufacturer and compares retrieval analytics; bearing surface damage, wear, and modular taper corrosion against patient, surgical and implant characteristics to elucidate significant associations. METHODS: Clinical, patient, and surgical data were collected including age, body mass index, blood metal ion levels, and cup inclination. Damage assessment was performed visually in addition to surface profilometry. Acetabular liners and femoral heads were measured for volumetric wear. Femoral head taper bores were similarly measured for material removal due to corrosion and fretting. RESULTS: Patients with MoM-related reasons for revision showed significantly higher levels of blood metal ion levels. Bearing wear was strongly associated with blood metal ion levels and was significantly increased in cups placed more vertically. Younger patients tended to have higher body mass indices as well as poorer cup placement. CONCLUSION: This work details a broad range of analyses on a series of modular MoM total hip implants from a single manufacturer of which there are few published studies. Acetabular cup inclination angle was deemed a primary cause of revision surgery through increased MoM wear, high metal ion levels in the blood, and subsequent adverse local tissue reactions. Heavy patients can increase the surgical difficulty which was shown to be related to poor cup placement in this cohort.

Factors influencing the reporting of adverse medical device events: qualitative interviews with physicians about higher risk implantable devices.

BACKGROUND: Postmarket surveillance of medical devices is reliant on physician reporting of adverse medical device events (AMDEs). Little is known about factors that influence whether and how physicians report AMDEs, an essential step in developing behaviour change interventions. This study explored factors that influence AMDE reporting. METHODS: Qualitative interviews were conducted with physicians who differed by specialties that implant cardiovascular and orthopaedic devices prone to AMDEs, geography and years in practice. Participants were asked if and how they reported AMDEs, and the influencing factors. Themes were identified inductively using constant comparative technique, and reviewed and discussed by the research team on four occasions. RESULTS: Twenty-two physicians of varying specialty, region, organisation and career stage perceived AMDE reporting as unnecessary, not possible or futile due to multiple factors. Physicians viewed AMDEs as an expected part of practice that they could manage by switching to different devices or developing work-around strategies for problematic devices. Physician beliefs and behaviour were reinforced by limited healthcare system capacity and industry responsiveness. The healthcare system lacked processes and infrastructure to detect, capture, share and act on information about AMDEs, and constrained device choice through purchasing contracts. The device industry did not respond to reports of AMDEs from physicians or improve their products based on such reports. As a result, participants said they used devices that were less than ideal for a given patient, leading to suboptimal patient outcomes. CONCLUSIONS: There may be little point in solely educating or incentivising individual physicians to report AMDEs unless environmental conditions are conducive to doing so. Future research should explore policies that govern AMDEs and investigate how to design and implement postmarket surveillance systems.

Damage Assessment of Retrieved Birmingham Monoblock Cups: Is Conversion to Dual-Mobility Head a Viable Revision Option?

BACKGROUND: A novel revision technique for failed hip resurfacings involves retention of the acetabular cup, if well-fixed, which is mated to dual-mobility (DM) prosthesis in a traditional hip replacement configuration. It is unknown whether existing damage on the retained cup will result in unacceptable wear of the DM prosthesis. METHODS: Thirty retrieved Birmingham (Smith & Nephew) monoblock cups were visually scored for damage features and area of coverage. Surface roughness measurements were obtained within each damage feature as well as reference points on each cup. Analysis of prior metal-on-metal wear was also performed to determine the maximum change in diameter of the cup. RESULTS: Scratching and grooving (deep, singular scratches) were the most common damage features. Overall bearing surface roughness was estimated as 0.059 µm (±0.030 µm) based on percent area coverage of each damage feature. Dimensional change of the bearing surface was negligible for most cups (18 of 30) but ranged from 0.20 to 0.38 mm for the most severely worn samples (5 of 30). CONCLUSION: Average surface roughness of the retrieved Birmingham cups was low, suggesting an expected 10%-20% increase in DM prosthesis wear. Similarly, dimensional change of the cup due to prior wear is not believed to significantly affect wear. Our findings support the use of a DM head in appropriate scenarios but suggest caution when applied to younger, more active patients whom may be adversely affected by increased prosthesis wear in the long term.

Multiple constraints compromise decision-making about implantable medical devices for individual patients: qualitative interviews with physicians.

BACKGROUND: Little research has examined how physicians choose medical devices for treating individual patients to reveal if interventions are needed to support decision-making and reduce device-associated morbidity and mortality. This study explored factors that influence choice of implantable device from among available options. METHODS: A descriptive qualitative approach was used. Physicians who implant orthopedic and cardiovascular devices were identified in publicly available directories and web sites. They were asked how they decided what device to use in a given patient, sources of information they consulted, and how patients were engaged in decision-making. Sampling was concurrent with data collection and analysis to achieve thematic saturation. Data were analyzed using constant comparative technique by all members of the research team. RESULTS: Twenty-two physicians from five Canadian provinces (10 cardiovascular, 12 orthopedic; 8, 10 and 4 early, mid and late career, respectively) were interviewed. Responses did not differ by specialty, geographic region or career stage. Five major categories of themes emerged that all influence decision-making about a range of devices, and often compromise choice of the most suitable device for a given patient, potentially leading to sub-optimal clinical outcomes: lack of evidence on device performance, patient factors, physician factors, organizational and health system factors, and device and device market factors. In the absence of evidence from research or device registries, tacit knowledge from trusted colleagues and less-trusted industry representatives informed device choice. Patients were rarely engaged in decision-making. Physician preference for particular devices was a barrier to acquiring competency in devices potentially more suitable for patients. Access to suitable devices was further limited to the number of comparable devices on the market, local inventory and purchasing contract specifications. CONCLUSIONS: This study revealed that decision-making about devices is complex, cognitively challenging and constrained by several factors limiting access to and use of devices that could optimize patient outcomes. Further research is needed to assess the impact of these constraints on clinical outcomes, and develop interventions that optimize decision-making about device choice for treating given patients.