Stable polyethylene inlay fixation and low polyethylene wear rate in fixed-bearing total knee arthroplasty at five to six years' follow-up.

Aims: Micromotion of the polyethylene (PE) inlay may contribute to backside PE wear in addition to articulate wear of total knee arthroplasty (TKA). Using radiostereometric analysis (RSA) with tantalum beads in the PE inlay, we evaluated PE micromotion and its relationship to PE wear. Methods: A total of 23 patients with a mean age of 83 years (77 to 91), were available from a RSA study on cemented TKA with Maxim tibial components (Zimmer Biomet). PE inlay migration, PE wear, tibial component migration, and the anatomical knee axis were evaluated on weightbearing stereoradiographs. PE inlay wear was measured as the deepest penetration of the femoral component into the PE inlay. Results: At mean six years' follow-up, the PE wear rate was 0.08 mm/year (95% confidence interval 0.06 to 0.09 mm/year). PE inlay external rotation was below the precision limit and did not influence PE wear. Varus knee alignment did not influence PE wear (p = 0.874), but increased tibial component total translation (p = 0.041). Conclusion: The PE inlay was well fixed and there was no relationship between PE stability and PE wear. The PE wear rate was low and similar in the medial and lateral compartments. Varus knee alignment did not influence PE wear.

Preoperative proximal tibial bone density, bone microarchitecture, and bone turnover are not associated with postoperative tibial component migration in cemented and cementless medial unicompartmental knee replacements: secondary analyses from a randomized controlled trial.

BACKGROUND AND PURPOSE: Cementless arthroplasty fixation relies on early bone ingrowth and may be poor in patients with low proximal tibial bone density or abnormal bone turnover. We aimed first to describe the baseline bone properties in patients undergoing medial unicompartmental knee replacement (UKR), and second to investigate its association with cemented and cementless tibial component migration until 2 years. METHODS: A subset investigation of 2 patient groups from a 3-armed randomized controlled trial was conducted. There were 26 cemented and 25 cementless medial UKRs with twin-pegged femoral components. Volumetric bone mineral density (vBMD) and microstructure of the excised medial tibial plateau were ascertained with µCT. Bone turnover was estimated using dynamic histomorphometry (eroded surface/bone surface = ES/BS, osteoid surface/bone surface = OS/BS, mineralizing surface/bone surface = MS/BS). Tibial component migration in 4 feature points was followed for 2 years with radiostereometry. RESULTS: At the 2-year follow-up, the cementless tibial components migrated 0.38 mm (95% confidence interval [CI] 0.14-0.62) total translation more than the cemented components at the posterior feature point. The greatest migration in the cementless group was subsidence at the posterior feature point of 0.66 mm (CI 0.48-0.84) until 6 weeks, and from 3 months the components were stable. Cemented tibial components subsided very little. Between 1- and 2-year follow-ups, no cementless but 4 cemented tibial components revealed continuous migration. OS/BS was half of the ES/BS. No µCT or histomorphometric parameters showed any clinically relevant correlation with tibial component migration at the posterior feature point for either cemented or cementless UKR at 6 weeks' or 2 years' follow-up after adjustment for age, BMI, and sex. CONCLUSION: Preoperative vBMD, bone turnover, and microstructure were not associated with postoperative tibial component migration of cemented and cementless medial UKR.

Machine-learning vs. logistic regression for preoperative prediction of medical morbidity after fast-track hip and knee arthroplasty-a comparative study.

BACKGROUND: Machine-learning models may improve prediction of length of stay (LOS) and morbidity after surgery. However, few studies include fast-track programs, and most rely on administrative coding with limited follow-up and information on perioperative care. This study investigates potential benefits of a machine-learning model for prediction of postoperative morbidity in fast-track total hip (THA) and knee arthroplasty (TKA). METHODS: Cohort study in consecutive unselected primary THA/TKA between 2014-2017 from seven Danish centers with established fast-track protocols. Preoperative comorbidity and prescribed medication were recorded prospectively and information on length of stay and readmissions was obtained through the Danish National Patient Registry and medical records. We used a machine-learning model (Boosted Decision Trees) based on boosted decision trees with 33 preoperative variables for predicting "medical" morbidity leading to LOS > 4 days or 90-days readmissions and compared to a logistical regression model based on the same variables. We also evaluated two parsimonious models, using the ten most important variables in the full machine-learning and logistic regression models. Data collected between 2014-2016 (n:18,013) was used for model training and data from 2017 (n:3913) was used for testing. Model performances were analyzed using precision, area under receiver operating (AUROC) and precision recall curves (AUPRC), as well as the Mathews Correlation Coefficient. Variable importance was analyzed using Shapley Additive Explanations values. RESULTS: Using a threshold of 20% "risk-patients" (n:782), precision, AUROC and AUPRC were 13.6%, 76.3% and 15.5% vs. 12.4%, 74.7% and 15.6% for the machine-learning and logistic regression model, respectively. The parsimonious machine-learning model performed better than the full logistic regression model. Of the top ten variables, eight were shared between the machine-learning and logistic regression models, but with a considerable age-related variation in importance of specific types of medication. CONCLUSION: A machine-learning model using preoperative characteristics and prescriptions slightly improved identification of patients in high-risk of "medical" complications after fast-track THA and TKA compared to a logistic regression model. Such algorithms could help find a manageable population of patients who may benefit most from intensified perioperative care.

Comparison of cementless twin-peg, cemented twin-peg and cemented single-peg femoral component migration after medial unicompartmental knee replacement: a 5-year randomized RSA study.

BACKGROUND: The component design and fixation method of joint arthroplasty may affect component migration and survival. The aim of this study was to compare fixation of cementless twin-peg (CLTP), cemented twin-peg (CTP) and cemented single-peg (CSP) femoral components of medial unicompartmental knee replacement (UKR). METHODS: Eighty patients (mean age = 63 years, 48 males) with medial knee osteoarthritis were randomized in three ways to CLTP (n = 25), CTP (n = 26) or CSP (n = 29) femoral UKR components. The patients were followed 5 years postoperatively with RSA, bone mineral density (BMD), PROMs and radiological evaluation of radiolucent lines (RLL), femoral component flexion angle and complications. RESULTS: At the 5-year follow-up, femoral component total translation was comparable between the three groups (p = 0.60). Femoral component internal rotation was 0.50° (95% CI 0.3; 0.69) for the CLTP group, 0.58° (95% CI 0.38; 0.77) for the CTP group and 0.25° (95% CI 0.07; 0.43) for the CSP group (p = 0.01). BMD decreased peri-prosthetically (range - 11.5%; - 14.0%) until 6-month follow-up and increased toward the 5-year follow-up (range - 3.6%; - 5.8%). BMD change did not correlate with component migration. Lower flexion angle was correlated with higher 5-year subsidence, total translation, varus rotation and maximum total point motion (p = 0.01). Two patients (1 CLTP, 1 CTP) had RLL in the posterior zone. There were two revisions. CONCLUSION: At 5-year follow-up, fixation of UKA femoral components with twin-peg was not superior to the single-peg design. Cementless and cemented twin-peg femoral components had similar fixation. A lower flexion angle was correlated with higher component migration.

Patients in high- and low-revision hospitals have similar outcomes after primary knee arthroplasty: 1-year postoperative results from the Danish prospective multicenter cohort study, SPARK.

PURPOSE: It is well-known that revision rates after primary knee arthroplasty vary widely. However, it is uncertain whether hospital revision rates are reliable indicators of general surgical quality as defined by patients. The SPARK study compared primary knee arthroplasty surgery at three high-volume hospitals whose revision rates differed for unknown reasons. METHODS: This prospective observational study included primary knee arthroplasty patients (total, medial/lateral unicompartmental and patellofemoral) in two low-revision hospitals (Aarhus University Hospital and Aalborg University Hospital Farsø) and one high-revision hospital (Copenhagen University Hospital Herlev-Gentofte). Patients were followed from preoperatively (2016-17) to 1-year postoperatively with patient-reported outcome measures including Oxford Knee Score (OKS), EQ-5D-5L and Copenhagen Knee ROM (range of motion) Scale. The surgical outcomes were compared across hospitals for patients with comparable grades of radiographic knee osteoarthritis and preoperative OKS. Statistical comparisons (parametric and non-parametric) included all three hospitals. RESULTS: 97% of the 1452 patients who provided baseline data (89% of those included and 56% of those operated) responded postoperatively (90% at 1 year). Hospitals' utilization of unicompartmental knee arthroplasties differed (Aarhus 49%, Aalborg 14%, and Copenhagen 22%, p < 0.001). 28 patients had revision surgery during the first year (hospital independent, p = 0.1) and were subsequently excluded. 1-year OKS (39 ± 7) was independent of hospital (p = 0.1), even when adjusted for age, sex, Body Mass Index, baseline OKS and osteoarthritis grading. 15% of patients improved less than Minimal Important Change (8 OKS) (Aarhus 19%, Aalborg 13% and Copenhagen 14%, p = 0.051 unadjusted). Patients with comparable preoperative OKS or osteoarthritis grading had similar 1-year results across hospitals (OKS and willingness to repeat surgery, p ≥ 0.087) except for the 64 patients with Kellgren-Lawrence grade-4 (Aarhus 4-6 OKS points lower). 86% of patients were satisfied, and 92% were "willing to repeat surgery", independent of hospital (p ≥ 0.1). Hospital revision rates differences diminished during the study period. CONCLUSIONS: Patients in hospitals with a history of differing revision rates had comparable patient-reported outcomes 1 year after primary knee arthroplasty, supporting that surgical quality should not be evaluated by revision rates alone. Future studies should explore if revision rate variations may depend as much on revision thresholds and indications as on outcomes of primary surgery. LEVEL OF EVIDENCE: Level II (Prospective cohort study).

Hospital variation in revision rates after primary knee arthroplasty was not explained by patient selection: baseline data from 1452 patients in the Danish prospective multicenter cohort study, SPARK.

PURPOSE: Revision rates following primary knee arthroplasty vary by country, region and hospital. The SPARK study was initiated to compare primary surgery across three Danish regions with consistently different revision rates. The present study investigated whether the variations were associated with differences in the primary patient selection. METHODS: A prospective observational cohort study included patients scheduled Sep 2016 Dec 2017 for primary knee arthroplasty (total, medial/lateral unicompartmental or patellofemoral) at three high-volume hospitals, representing regions with 2-year cumulative revision rates of 1, 2 and 5%, respectively. Hospitals were compared with respects to patient demographics, preoperative patient-reported outcome measures, motivations for surgery, implant selection, radiological osteoarthritis and the regional incidence of primary surgery. Statistical tests (parametric and non-parametric) comprised all three hospitals. RESULTS: Baseline data was provided by 1452 patients (89% of included patients, 56% of available patients). Patients in Copenhagen (Herlev-Gentofte Hospital, high-revision) were older (68.6 ± 9 years) than those in low-revision hospitals (Aarhus 66.6 ± 10 y. and Aalborg (Farsø) 67.3 ± 9 y., p = 0.002). In Aalborg, patients who had higher Body Mass Index (mean 30.2 kg/m2 versus 28.2 (Aarhus) and 28.7 kg/m2 (Copenhagen), p < 0.001), were more likely to be male (56% versus 45 and 43%, respectively, p = 0.002), and exhibited fewer anxiety and depression symptoms (EQ-5D-5L) (24% versus 34 and 38%, p = 0.01). The preoperative Oxford Knee Score (23.3 ± 7), UCLA Activity Scale (4.7 ± 2), range of motion (Copenhagen Knee ROM Scale) and patient motivations were comparable across hospitals but varied with implant type. Radiological classification ≥ 2 was observed in 94% (Kellgren-Lawrence) and 67% (Ahlbäck) and was more frequent in Aarhus (low-revision) (p ≤ 0.02), where unicompartmental implants were utilized most (49% versus 14 (Aalborg) and 23% (Copenhagen), p < 0.001). In the Capital Region (Copenhagen), the incidence of surgery was 15-28% higher (p < 0.001). CONCLUSION: Patient-reported outcome measures prior to primary knee arthroplasty were comparable across hospitals with differing revision rates. While radiographic classifications and surgical incidence indicated higher thresholds for primary surgery in one low-revision hospital, most variations in patient and implant selection were contrary to well-known revision risk factors, suggesting that patient selection differences alone were unlikely to be responsible for the observed variation in revision rates across Danish hospitals. LEVEL OF EVIDENCE: II, Prospective cohort study.

Patellofemoral Arthroplasty Results in Better Time-weighted Patient-reported Outcomes After 6 Years than TKA: A Randomized Controlled Trial.

BACKGROUND: In a previous study, we reported the 2-year outcomes of a parallel-group, equivalence, randomized controlled trial (RCT; blinded for the first year) comparing patellofemoral arthroplasty (PFA) and TKA for isolated patellofemoral osteoarthritis (PF-OA). We found advantages of PFA over TKA for ROM and various aspects of knee-related quality of life (QOL) as assessed by patient-reported outcomes (PROs). Register data show increases in PFA revision rates from 2 to 6 years after surgery at a time when annual TKA revision rates are decreasing, which suggests rapidly deteriorating knee function in patients who have undergone PFA. We intended to examine whether the early advantages of PFA over TKA have deteriorated in our RCT and whether revision rates differ between the implant types in our study after 6 years of follow-up. QUESTIONS/PURPOSES: (1) Does PRO improvement during the first 6 postoperative years differ between patients who have undergone PFA and TKA? (2) Does the PRO improvement at 3, 4, 5, and 6 years differ between patients who have undergone PFA and TKA? (3) Do patients who have undergone PFA have a better ROM after 5 years than patients who have had TKA? (4) Does PFA result in more revisions or reoperations than TKA during the first 6 postoperative years? METHODS: We considered patients who had debilitating symptoms and PF-OA as eligible for this randomized trial. Screening initially identified 204 patients as potentially eligible; 7% (15) were found not to have sufficient symptoms, 21% (43) did not have isolated PF-OA, 21% (43) declined participation, and 1% (3) were not included after the target number of 100 patients had been reached. The included 100 patients were randomized 1:1 to PFA or TKA between 2007 and 2014. Of these, 9% (9 of 100) were lost before the 6-year follow-up; there were 12% (6 of 50) and 0% (0 of 50) deaths (p = 0.02) in the PFA and TKA groups, respectively, but no deaths could be attributed to the knee condition. There were no differences in baseline parameters for patients who had PFA and TKA, such as the proportion of women in each group (78% [39 of 50] versus 76% [38 of 50]; p > 0.99), mean age (64 ± 9 years versus 65 ± 9 years; p = 0.81) or BMI (28.0 ± 4.7 kg/m 2 versus 27.8 ± 4.1 kg/m 2 ; p = 0.83). Patients were seen for five clinical follow-up visits (the latest at 5 years) and completed 10 sets of questionnaires during the first 6 postoperative years. The primary outcome was SF-36 bodily pain. Other outcomes were reoperations, revisions, ROM, and PROs (SF-36 [eight dimensions, range 0 to 100 best, minimum clinically important difference {MCID} 6 to 7], Oxford Knee Score [OKS; one dimension, range 0 to 48 best, MCID 5], and Knee Injury and Osteoarthritis Outcome Score [KOOS; five dimensions, range 0 to 100 best, MCID 8 to 10]). Average PRO improvements over the 6 years were determined by calculating the area under the curve and dividing by the observation time, thereby obtaining a time-weighted average over the entire postoperative period. PRO improvements at individual postoperative times were compared for the patients who had PFA and TKA using paired t-tests. Range of movement changes from baseline were compared using paired t-tests. Reoperation and revision rates were compared for the two randomization groups using competing risk analysis. RESULTS: Patients who underwent PFA had a larger improvement in the SF-36 bodily pain score during the first 6 years than those who underwent TKA (35 ± 19 vs. 23 ± 17; mean difference 12 [95% CI 4 to 20]; p = 0.004), and the same was true for SF-36 physical functioning (mean difference 11 [95% CI 3 to 18]; p = 0.008), KOOS Symptoms (mean difference 12 [95% CI 5 to 20]; p = 0.002), KOOS Sport/recreation (mean difference 8 [95% CI 0 to 17]; p = 0.048), and OKS (mean difference 5 [95% CI 2 to 8]; p = 0.002). No PRO dimension had an improvement in favor of TKA. At the 6-year time point, only the SF-36 vitality score differed between the groups being in favor of PFA (17 ± 19 versus 8 ± 21; mean difference 9 [95% CI 0 to 18]; p = 0.04), whereas other PRO measures did not differ between the groups. At 5 years, ROM had decreased less from baseline for patients who underwent PFA than those who had TKA (-4° ± 14° versus -11° ± 13°; mean difference 7° [95% CI 1° to 13°]; p = 0.02), but the clinical importance of this is unknown. Revision rates did not differ between patients who had PFA and TKA at 6 years with competing risk estimates of 0.10 (95% CI 0.04 to 0.20) and 0.04 (95% CI 0.01 to 0.12; p = 0.24), respectively, and also reoperation rates were no different at 0.10 (95% CI 0.04 to 0.20) and 0.12 (95% CI 0.05 to 0.23; p = 0.71), respectively. CONCLUSION: Our RCT results show that the 2-year outcomes did not deteriorate during the subsequent 4 years. Patients who underwent PFA had a better QOL throughout the postoperative years based on several of the knee-specific outcome instruments. When evaluated by the 6-year observations alone and without considering earlier observations, we found no consistent difference for any outcome instruments, although SF-36 vitality was better for patients who underwent PFA. These combined findings show that the early advantages of PFA determined the results by 6 years. Our findings cannot explain the rapid deterioration of results implied by the high revision rates observed in implant registers, and it is necessary to question indications for the primary procedure and subsequent revision when PFA is in general use. Our data do not suggest that there is an inherent problem with the PFA implant type as otherwise suggested by registries. The long-term balance of advantages will be determined by the long-term QOL, but based on the first 6 postoperative years and ROM, PFA is still the preferable option for severe isolated PF-OA. A possible high revision rate in the PFA group beyond 6 years may outweigh the early advantage of PFA, but only detailed analyses of long-term studies can confirm this. LEVEL OF EVIDENCE: Level I, therapeutic study.

Component migration, bone mineral density changes, and bone turnover markers in cementless and cemented total knee arthroplasty: a prospective randomized RSA study in 53 patients with 2-year follow-up.

PURPOSE: Cementless tibial components migrate initially until osseointegration and preserve periprosthetic bone. Cemented tibial components are fixed from surgery but loose periprosthetic bone. Little is known about bone formation and resorption biomarkers in relation to component fixation and bone mineral density (BMD) changes of cementless and cemented total knee arthroplasty. We hypothesize a similar migration of cemented and cementless tibial components between 1- and 2-year follow-up indicating a stable long-term fixation. METHODS: In a prospective patient-blinded randomized study, we compared cementless (n = 27) and cemented (n = 26) tibial components with radiostereometry measured migration (MTPM = Maximum Total Point Motion: point of component that migrates the most) and changes in BMD and biochemical bone turnover markers (BTMs) until 24 months after surgery. RESULTS: The mean MTPM between 12 and 24 months were similar between groups with - 0.06 mm (95% CI - 0.23; 0.11) in the cementless group compared to 0.02 mm (95% CI - 0.07; 0.11) in the cemented group. However, there was a higher proportion of cementless components (16/25) than cemented components (7/24) with continuous migration (MTPM > 0.2 mm) (p = 0.02). In the medial and anterior region below the tibial components, the BMD increased by mean 1.8% and 7.4% for cementless components and decreased by mean 8.6% and 4.2% for cemented components until 24-month follow-up. In both groups, BTMs initially showed increased bone resorption (CTx) and bone formation (P1NP) followed by normalization to pre-operative levels at 6 months post-surgery. CONCLUSION: More cementless components than cemented components showed continues migration which suggest a higher risk of early revision. Bone turnover increased post-surgery in both groups, but did not explain the difference in change in periprosthetic BMD. LEVEL OF EVIDENCE: I.

Fast-track revision knee arthroplasty.

BACKGROUND: Limited data exist on fast-track protocols in relation to revision knee arthroplasty. Hence, the aim of this study was to report length of stay (LOS), risk of LOS > 5 days and readmission ≤ 90 days after revision knee arthroplasty in centers with a well-established fast-track protocol in both primary and revision surgery. METHODS: An observational cohort study from the Centre for Fast-track Hip and Knee Replacement and the Danish Knee Arthroplasty Register. We included elective aseptic major component revision knee arthroplasties consecutively from 6 dedicated fast-track centers from 2010 to 2018. RESULTS: 1439 revision knee arthroplasties were analyzed, including 900 total revisions, 171 large partial revisions (revision of either femoral or tibia component) and 368 revisions of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA). Mean age was 65 years (SD 10.9) and 66% were females. Mean LOS was 3.7 days (SD 3.9) in the study period, but decreased to 2.4 days (SD 1.3) in 2018. Risk factors for LOS > 5 days was ≥ 1 previous revision, use of walking aid, BMI > 35, ages < 50, 70-79 and ≥ 80 years, whereas revision of UKA to TKA and large partial revision were negatively associated. The 90-day readmission and mortality risk was 9.1% and 0.5%. Cardiac disease and use of walking aid were associated with increased risk of readmission ≤ 90 days. CONCLUSION: Elective aseptic major component revision knee arthroplasty using similar fast-track protocols as in primary TKA is safe with short and decreasing LOS.

Two-year fixation and ten-year clinical outcomes of total knee arthroplasty inserted with normal-curing bone cement and slow-curing bone cement: A randomized controlled trial in 54 patients.

BACKGROUND: The normal-curing Refobacin® Bone Cement R (RR) and slow-curing Refobacin® Plus Bone Cement (RP) were introduced after discontinuation of the historically most used bone cement, Refobacin®-Palacos® R, in 2005. The aim of this study was to compare total knee arthroplasty component fixation with the two bone cements. METHODS: 54 patients with primary knee osteoarthritis were randomized to either RR (N = 27) or RP (N = 27) bone cement and followed for two years with radiostereometric analysis of tibial and femoral component migration and dual-energy x-ray absorptiometry measured periprosthetic bone mineral density (BMD). Further, patients were followed up at ten years with clinical outcome scores (OKS and KOOS). RESULTS: At two-years follow-up, tibial total translation was 0.31 mm (95% CI: 0.19 - 0.42) for the RP group and 0.56 mm (95% CI: 0.45 - 0.67) (p < 0.01) for the RR group. There was continuous tibial component migration from one to two years follow-up (MTPM > 0.2 mm) in 13/27 patients from the RR and in 12/26 patients from the RP group. There was no difference between groups in BMD baseline values or changes during follow-up, as well as no correlation between change in BMD and tibial component migration. At ten-years follow-up, the improvement in the clinical outcome scores was similar between groups. There were no prosthesis related complications during the 10-year follow-up. CONCLUSION: At two years, tibial total translation was lower in the RP compared with the RR cement group, but BMD changes were similar. At ten years, no components were revised and clinical outcome scores were similar between groups.

Less polyethylene wear in monobloc compared to modular ultra-high-molecular-weight-polyethylene inlays in hybrid total knee arthroplasty: A 5-year randomized radiostereometry study.

BACKGROUND: A modular polyethylene (PE) inlay in total knee arthroplasty (TKA) may wear on both sides. PE particles may induce osteolysis, which can lead to implant loosening. The aim of this study was to determine if PE wear in monobloc TKA differs from that ofmodular TKA at 60-month follow-up. PATIENTS AND METHODS: In a prospective, patient-blinded trial, 50 patients were randomized to hybrid TKA surgery with either acementless high-porosity trabecular-metal tibial component with a monobloc UHMWPE inlay (MONO-TM) or a cementless low-porosity screw-augmented titanium fiber-mesh tibial component with a modular UHMWPE inlay (MODULAR-FM). Radiostereometry was used to measure PE wear and tibial component migration. RESULTS: At 60-monthfollow-up, mean PE wear of the medial compartment was 0.24 mm and 0.61 mm and mean PE wear of the lateral compartment was 0.31 mm and 0.82 mm for the MONO-TM and the MODULAR-FM groups, respectively (p < 0.01). The PE wear-rate was 0.05 mm (95% CI 0.03-0.08) in the MONO-TM group and 0.14 mm (95% CI 0.12-0.17) in the MODULAR-FM group (p < 0.01). Total translation at 60 months was mean 0.30 mm (95% CI 0.10-0.51) less (p < 0.01) for MONO-TM compared with MODULAR-FM tibial components. The majority of tibial components were stable (<0.2 mm MTPM) from 12 to 24-month and 24 to 60-month follow-up. CONCLUSION: At mid-term follow-up, monobloc PE inlay wear was approximately 40% of that of the modular PE inlay wear, which suggest that back-side wear of modular PE inlays is a significant contributor of PE wear in hybrid TKA.

Does an Antimicrobial Incision Drape Prevent Intraoperative Contamination? A Randomized Controlled Trial of 1187 Patients.

BACKGROUND: The risk of periprosthetic joint infection (PJI), a serious complication after arthroplasty, has not changed for years. Interventions such as eradication of Staphylococcus aureus and antibiotic bone cement are used to diminish infection risk but despite these efforts, the percentage of infection in TKA remains constant. Antimicrobial drapes have a dual action, acting both as a physical and antimicrobial barrier to counter bacterial contamination of the surgical wound. To study the effect of antimicrobial drapes, we used intraoperative contamination as a proxy for infection in our investigation. QUESTIONS/PURPOSES: (1) Do antimicrobial surgical drapes reduce the risk of intraoperative microbial contamination in patients undergoing primary knee arthroplasty? (2) Are other factors such as sex, season, age, type of arthroplasty and duration of surgery associated with an increased risk of contamination in patients undergoing primary knee arthroplasty? (3) Does loosening of the antimicrobial drape increase contamination risk? METHODS: An investigator-initiated, two-arm, non-blinded, multicenter, randomized, controlled trial was performed at five different hospitals in the capital and central regions of Denmark. Twenty-four surgeons participated in the study. Participants were patients older than 18 years undergoing primary knee arthroplasty. We excluded patients with an iodine allergy, previous open knee surgery, previous septic arthritis, any antibiotics taken 4 weeks before surgery, and if they were unable to understand the implications of study participation. Patients were randomly assigned to operation with an antimicrobial drape (intervention group) or operation without (control group). We screened 1769 patients, of which 100 were ineligible and 10 declined to participate. In all, 94% (1659 of 1769) of patients consented and were randomized to the intervention group (51%, 838 of 1659) and control group (49%, 821 of 1659), respectively. In all, 36% (603 of 1659) of patients in the intervention group and 35% (584 of 1659) patients in the control group were available for final analysis. No crossover was performed, and analysis was done per-protocol. Patients were excluded due to logistic failures like lack of utensils, samples disappearing en route to the laboratory mainly caused by implementation of a new electronic patient chart (EPIC, Verona, WI, USA), and forgetful surgeons. Intraoperatively, we swabbed for bacteria at the surgical site and in a rinse from the surgeons' gloves. All samples were sent for cultivation, and colony forming units (CFUs) counts ≥ 1 were deemed contaminated. The primary outcome measure was the difference in the proportion of contaminated patients between the two randomized groups. Secondary outcome measures were the affiliation of sex, season, age, type of implant used, and duration of surgery on contamination risk. To investigate whether other factors were affiliated with contamination risk, we did a logistic regression to control for confounding variables, including sex, age, season, type of implant and duration of surgery. RESULTS: Use of iodinated drapes reduced contamination, with contamination detected in 10% (60 of 603) procedures where iodinated drapes were used compared with 15% (90 of 584) when they were not (odds ratio 0.61 [95% CI 0.43 to 0.87]; p = 0.005), with a relative risk reduction of 35% (95% CI 12.3 to 52.5) and a number needed to treat of 18 patients. After controlling for confounding variables such as sex, age, type of implant, and duration of surgery, we found that not using an antimicrobial drape increased contamination risk by a factor of 1.6 (95% CI 1.08 to 2.35; p = 0.02). Female sex and undergoing surgery in the central region were associated with lower odds of contamination (OR 0.55 [95% CI 0.39 to 0.8]; p = 0.002 and OR 0.45 [95% CI 0.25 to 0.8]; p = 0.006, respectively). Patients with more than a 10-mm separation of the drape from the skin had higher odds of contamination (OR 3.54 [95% CI 1.64 to 11.05]; p = 0.0013). CONCLUSIONS: The use of an antimicrobial drape resulted in lower contamination risk than operating without an antimicrobial drape. Our findings suggest that antimicrobial drapes are useful in infection prevention, but further studies are needed to investigate the effect of antimicrobial drapes on infection. LEVEL OF EVIDENCE: Level I, therapeutic study.

Patellofemoral Arthroplasty.

BACKGROUND: The first report of patellofemoral arthroplasty (PFA) was published in 19791. Reviews in 2005 and 20072,3 called for studies comparing PFA with total knee arthroplasty (TKA) for isolated patellofemoral osteoarthritis. A blinded randomized controlled trial (RCT) was initiated in 2007 for this purpose, and the first report with 2-year results was awarded the Mark Coventry Award of the Knee Society in 20174. It was found that (1) patients recover more quickly from PFA than from TKA; (2) during the first 2 years after surgery, PFA-treated patients have better average knee function than TKA-treated patients; and (3) PFA-treated patients regain their preoperative range of movement within the first postoperative year whereas TKA-treated patients do not regain it within the first 2 years4. DESCRIPTION: There are general principles that are common to all brands of PFA implants. These include (1) an indication based on bone-on-bone contact in the patellofemoral joint with a preserved tibiofemoral joint; (2) replacing all surfaces of the patellofemoral joint, with metal on the femoral side and polyethylene on the patellar side; (3) ensuring a smooth transition from normal articular cartilage to the trochlear component; and (4) creating normal patellofemoral tracking. ALTERNATIVES: The primary treatment of any degenerative condition should be nonoperative, but when such measures are insufficient surgical treatment may be indicated. Many procedures have been suggested for relieving patellofemoral pain, but if there is bone-on-bone contact in the patellofemoral joint, the only current surgical option (except for experimental treatments) is joint replacement-i.e., either PFA or TKA. RATIONALE: Our general principle for joint replacement of the knee is to replace only the affected compartment if unicompartmental changes are found. If ≥2 compartments are affected, we perform TKA. This principle is challenged both by proponents of performing TKA in all cases of knee osteoarthritis and by proponents of bicompartmental knee replacement for 2-compartment disease. The 2-year results of our blinded RCT comparing PFA and TKA4 support our current practice of PFA. In our practice, we have found PFA to be a rewarding procedure when the correct indications are used. PFA is likely to remain a fairly rare procedure, but any knee arthroplasty center should be able to offer it.

Implant fracture of the Regenerex® modular metal tibial component: A report of three cases.

BACKGROUND: Implant fractures are a very rare complication in primary total knee replacement (TKR) surgery and with modern implant designs and improved metals these events have nearly been eliminated. In this case series we report three cases of tibial metal baseplate fractures in uncemented Regenerex® TKR. METHODS: Cases originated from a prospective case series of 80 patients operated between 2013 and 2016. Five patients were pilot cases and 75 were participants in a prospective randomized double-blinded clinical trial that evaluated different adjuvant bone anti-resorptive medical therapies. All patients were treated with an uncemented press-fit Regenerex® Porous Titanium Construct tibial tray and matching cemented (Refobacin Bone Cement R) patella and femoral components (hybrid implant). RESULTS: We report three cases of medial side metal baseplate fractures of a modular finned tibial stem. All three baseplate fractures were in male patients. Confirmed failure of the implant occurred after 10, 12 and 23 months, in situ, with a mean follow-up of 15 months (range 10-23). CONCLUSIONS: Based on the current case series we cannot make any causal inferences. Failures may represent a multifactorial process with a cascade of events with implant failure as the result. However, like in most other case reports of metal failures in the literature, the implant fractures in this report were located on the medial side of the tibial component in male patients.

Preoperative Systemic Bone Quality Does Not Affect Tibial Component Migration in Knee Arthroplasty: A 2-Year Radiostereometric Analysis of a Hundred Consecutive Patients.

BACKGROUND: Bone quality and other preoperative predictive factors may affect implant migration and the survival of knee arthroplasty. METHODS: In a prospective cohort of 100 consecutive patients (65 women) at a mean age of 67.7 years (range 39-87 years), we investigated preoperative predictors of postoperative tibial component migration in cemented and cementless total knee arthroplasties or cemented unicompartmental knee arthroplasty. Predictors consisted of Knee Injury and Osteoarthritis Outcome Score (KOOS) and Oxford Knee Score, questionnaires, bone turnover markers of CTX and P1NP, systemic bone mineral density (BMD), and knee osteoarthritis (OA) grade. Tibial component migration was measured with radiostereometry postoperative, at 1 and 2 years of follow-up. RESULTS: Between 1 and 2 years, 19 tibial components migrated continuously (maximum total point motion [MTPM] > 0.2 mm). In general, there was no difference in age, body mass index, BMD, KOOSs, or OA grade between patients with continuous tibial migration compared to patients without continuous migration (P > .11). However, cementless tibial components with continuous migration had a lower KOOS pain score (more pain), lower vitamin D, and a higher bone turnover (CTX) value than patients without continuous migration. There was no association between the BMD and MTPM at 1-year follow-up regardless of prothesis type (P > .17). Patients with osteoporosis and normal BMD had similar mean tibial component MTPM at 2 years (3 prostheses combined; P = .34). CONCLUSION: Migration of tibial components inserted with or without bone cement was not affected by the preoperative bone quality in terms of systemic BMD, bone turnover markers, and OA grade in the knee.

Randomized clinical trial of medial unicompartmentel versus total knee arthroplasty for anteromedial tibio-femoral osteoarthritis. The study-protocol.

BACKGROUND: In treatment of isolated medial unicondylar osteoarthritis of the knee, it is possible to choose between medial unicondylar knee arthroplasty (mUKA), or a total knee prosthesis (TKA). The demand for a blinded multicenter RCT with the comparison of mUKA and TKA has been increasing in recent years, to determine which prosthesis is better. Supporters of TKA suggest this treatment gives a more predictable and better result, whereas supporters of UKA suggest it is unnecessary to remove functional cartilage in other compartments. If the mUKA is worn or loosens, revision surgery will be relatively easy, whereas revision-surgery after a TKA can be more problematic. METHODS: A double-blinded multicenter Randomized Clinical Trial setup is the aim of the study. 6 hospitals throughout all 5 municipal regions of Denmark will be participating in the study. 350 patients will be included prospectively. Follow-up will be with PROM-questionnaires and clinical controls up to 20 years. DISCUSSION: Results will be assessed in terms of 1) PROM-questionnaires, 2) Clinical assessment of knee condition, 3) cost analysis. To avoid bias, all participants except the theatre-staff will be blinded. PROMS: OKS, KOOS, SF36, Forgotten Joint Score, EQ5D, UCLA activity scale, Copenhagen Knee ROM scale, and Anchor questions. Publications are planned at 2, 5 and 10 years after inclusion of the last patient. The development of variables over time will be analyzed by calculating the area under the curve (AUC) for the variable relative to the initial value, and comparisons of the between-group differences will be based on parametric statistics. In this study, we feel that we have designed a study that will address these concerns with a well-designed double-blinded multicentre RCT. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT03396640 . Initial Release: 09/19/2017. Date of enrolment of first participant: 10/11/17.

Superior fixation and less periprosthetic stress-shielding of tibial components with a finned stem versus an I-beam block stem: a randomized RSA and DXA study with minimum 5 years' follow-up.

Background and purpose - The stem on the tibial component of total knee arthroplasty provides mechanical resistance to lift-off, shear forces, and torque. We compared tibial components with finned stems (FS) and I-beam block stems (IS) to assess differences in implant migration. Patients and methods - In a patient-blinded RCT, 54 patients/knees (15 men) with knee osteoarthritis at a mean age of 77 years (70-90) were randomly allocated to receive tibial components with either a FS (n = 27) or an IS (n = 27). Through 5 to 7 years' follow-up, implant migration was measured with RSA, periprosthetic bone mineral density (BMD) was measured with DXA, and surgeons reported American Knee Society Score (AKSS). Results - At minimum 5 years' follow-up, maximum total point motion (MTPM) was higher (p = 0.04) for IS (1.48 mm, 95% CI 0.81-2.16) than for FS (0.85 mm, CI 0.38-1.32) tibial components. Likewise, total rotation (TR) was higher (p = 0.03) for IS (1.51˚, CI 0.78-2.24) than for FS (0.81˚, CI 0.36-1.27). Tibial components with IS externally rotated 0.50° (CI -0.06 to 1.06) while FS internally rotated 0.09° (CI -0.20 to 0.38) (p = 0.03). Periprosthetic bone stress-shielding was higher (p < 0.01) up to 2 years' follow-up for IS compared with FS in the regions medial to the stem (-13% vs. -2%) and posterior to the stem (-13% vs. -2%). Below the stem bone loss was also higher (p = 0.01) for IS compared with FS (-6% vs. +1%) up to 1-year follow-up. Knee score improved similarly in both groups up to 5 years' follow-up. Interpretation - Periprosthetic bone stress-shielding medial and posterior to the stem until 2 years, and tibial component migration at 5 years, was less for a finned compared with an I-shaped block stem design.

Similar polyethylene wear between cemented and cementless Oxford medial UKA: a 5-year follow-up randomized controlled trial on 79 patients using radiostereometry.

Background and purpose - Hydroxyapatite (HA)-coated implants have been associated with high polyethylene wear in hip arthroplasties. HA coating as a promoter of wear in knee arthroplasties has not been investigated. We compared the wear-rate of the polyethylene bearing for cemented and cementless HA-coated Oxford medial unicondylar knee arthroplasties (UKA). Secondarily, we investigated whether wear-rates were influenced by overhang or impingement of the bearing. Patients and methods - 80 patients (mean age 64 years), treatment-blinded, were randomized to 1 of 3 Oxford medial UKA versions: cemented with double-pegged or single-pegged femoral component or cementless HA-coated with double-pegged femoral component (ratios 1:1:1). We compared wear between the cemented (n = 55) and cementless group (n = 25) (ratio 2:1). Wear, impingement, and overhang were quantified between surgery and 5-year follow-up using radiostereometry. Clinical outcome was evaluated with the Oxford Knee Score. Results - The mean wear-rate for patients without bearing overhang was 0.04 mm/year (95% CI 0.02-0.07) for the cemented group and 0.05 mm/year (CI 0.02-0.08) for the cementless group. The mean difference in wear was 0.008 mm/year (CI -0.04 to 0.03). No impingement was identified. Half of the patients had medial bearing overhang, mean 2.5 mm (1-5). Wear increased by 0.014 mm/year for each mm increment in overhang. The mean Oxford Knee Score was 39 for the cementless group and 38 for the cemented group at the 5-year follow-up. Interpretation - The wear-rates were similar for the 2 fixation methods, which supports further use of the cementless Oxford medial UKA. However, a caveat is a relatively large 95% CI of the mean difference in wear-rate. Component size and position is important as half of the patients presented with an additional increase in wear-rate due to medial bearing overhang.

The Mark Coventry Award: Patellofemoral Arthroplasty Results in Better Range of Movement and Early Patient-reported Outcomes Than TKA.

BACKGROUND: Controversy exists over the surgical treatment for severe patellofemoral osteoarthritis. We therefore wished to compare the outcome of patellofemoral arthroplasty (PFA) with TKA in a blinded randomized controlled trial. QUESTIONS/PURPOSES: In the first 2 years after surgery: (1) Does the overall gain in quality of life differ between the implants based on the area under the curve of patient-reported outcomes (PROs) versus time? (2) Do patients obtain a better quality of life at specific points in time after PFA than after TKA? (3) Do patients get a better range of movement after PFA than after TKA? (4) Does PFA result in more complications than TKA? METHODS: Patients were eligible if they had debilitating symptoms and isolated patellofemoral disease. One hundred patients were included from 2007 to 2014 and were randomized to PFA or TKA (blinded for the first year; blinded to patient, therapists, primary care physicians, etc; quasiblinded to assessor). Patients were seen for four clinical followups and completed six sets of questionnaires during the first 2 postoperative years. SF-36 bodily pain was the primary outcome. Other outcomes were range of movement, PROs (SF-36, Oxford Knee Score [OKS], Knee injury and Osteoarthritis Outcome Score [KOOS]) as well as complications and revisions. Four percent (two of 50) of patients died within the first 2 years in the PFA group (none in the TKA group), and 2% (one of 50) became ill and declined further participation after 1 year in the PFA group (none in the TKA group). The mean age at inclusion was 64 years (SD 8.9), and 77% (77 of 100) were women. RESULTS: The area under the curve (AUC) up to 2 years for SF-36 bodily pain of patients undergoing PFA and those undergoing TKA was 9.2 (SD 4.3) and 6.5 (SD 4.5) months, respectively (p = 0.008). The SF-36 physical functioning, KOOS symptoms, and OKS also showed a better AUC up to 2 years for PFA compared with TKA (6.6 [SD 4.8] versus 4.2 [SD 4.3] months, p = 0.028; 5.6 [SD 4.1] versus 2.8 [SD 4.5] months, p = 0.006; 7.5 [SD 2.7] versus 5.0 [SD 3.6] months, p = 0.001; respectively). The SF-36 bodily pain improvement at 6 months for patients undergoing PFA and those undergoing TKA was 38 (SD 24) and 27 (SD 23), respectively (p = 0.041), and at 2 years, the improvement was 39 (SD 24) and 33 (SD 22), respectively (p = 0.199). The KOOS symptoms improvement at 6 months for patients undergoing PFA and those undergoing TKA was 24 (SD 20) and 7 (SD 21), respectively (p < 0.001), and at 2 years, the improvement was 27 (SD 19) and 17 (SD 21), respectively (p = 0.023). Improvements from baseline for KOOS pain, SF-36 physical functioning, and OKS also differed in favor of PFA at 6 months, whereas only KOOS symptoms showed a difference between the groups at 2 years. No PRO dimension showed a difference in favor of TKA. At 4 months, 1 year, and 2 years, the ROM change from baseline for patients undergoing PFA and those undergoing TKA was (-7° [SD 13°] versus -18° [SD 14°], p < 0.001; -4° [SD 15°] versus -11° [SD 12°], p = 0.011; and -3° [SD 12°] versus -10° [SD 12°], p = 0.010). There was no difference in the number of complications. During the first 2 postoperative years, there were two revisions in patients undergoing PFA (one to a new PFA and one to a TKA). CONCLUSIONS: Patients undergoing PFA obtain a better overall knee-specific quality of life than patients undergoing TKA throughout the first 2 years after operation for isolated patellofemoral osteoarthritis. At 2 years, only KOOS function differs between patients undergoing PFA and those undergoing TKA, whereas other PRO dimensions do not show a difference between groups. The observations can be explained by patients undergoing PFA recovering faster than patients undergoing TKA and the functional outcome being better for patients undergoing PFA up to 9 months. Patients undergoing PFA regain their preoperative ROM, whereas patients undergoing TKA at 2 years have lost 10° of ROM. We found no differences in complications. LEVEL OF EVIDENCE: Level I, therapeutic study.