Inadequate Classification of Poor Response After Total Knee Arthroplasty: A Comparative Analysis of 15 Definitions Using Data from the Dutch Arthroplasty Register and the Osteoarthritis Initiative Database.

BACKGROUND: Variations in defining poor response to total knee arthroplasty (TKA) impede comparisons of response after TKA over time and across hospitals. This study aimed to compare the prevalence, overlap, and discriminative accuracy of 15 definitions of poor response after TKA using two databases. METHODS: Data of patients one year after primary TKA from the Dutch Arthroplasty Register (LROI) (n = 12,275) and the Osteoarthritis Initiative (OAI) database (n = 204) were used to examine the prevalence, overlap (estimated by Cohen's kappa), and discriminative accuracy (sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and Youden index) of 15 different definitions of poor response after TKA. In the absence of a gold standard for measuring poor response to TKA, the numeric rating scale (NRS) satisfaction (≤ 6 'poor responder') and the global assessment of knee impact (dichotomized: ≥ 4 'poor responder') were used as anchors for assessing discriminative accuracy for the LROI and OAI dataset, respectively. These anchors were chosen based on a prior qualitative study that identified (dis)satisfaction as a central theme of poor responses to TKA by patients and knee specialists. RESULTS: The median (25th to 75th percentile) prevalence of poor responders in the examined definitions was 18.5% (14.0 to 25.5%), and the median Cohen's kappa for the overlap between pairs of definitions was 0.41 (0.32 to 0.59). Median (25th to 75th percentile) sensitivity was 0.45 (0.39 to 0.54), specificity was 0.86 (0.82 to 0.94), PPV was 0.45 (0.34 to 0.62), NPV was 0.89 (0.87 to 0.89), and the Youden index was 0.36 (0.20 to 0.43). CONCLUSION: This found a lack of overlap between different definitions of poor response to TKA. None of the examined definitions adequately classified poor responders to TKA. In contrast, the absence of a poor response could be classified with confidence.

Multiplex PCR test as an intra-operative diagnostic tool for periprosthetic joint infection in presumed aseptic revision hip and knee arthroplasty: a 1-year follow-up study of 200 cases.

Automated custom-made multiplex PCR techniques (mPCR) have become commercially available and are designed for intra-operative screening of concurrent periprosthetic joint infections (PJIs). The purpose of this study was to evaluate the value of a positive mPCR test in presumed aseptic revision total hip (THA) and knee (TKA) arthroplasties after a 1-year follow-up. In an earlier study, such an automated mPCR technique (Unyvero ITI G2; Curetis, Holzgerlingen, Germany) was tested on intra-operatively obtained synovial fluid in 200 patients with a presumed aseptic TKA or THA revision. At the time of revision, no therapeutic consequences were attached to a positive test result since treating personnel were blinded for the test results. We retrospectively reviewed the outcome of cases with respect to the occurrence of PJIs using the European Bone and Joint Infection Society (EBJIS) criteria during a 1-year follow-up postoperatively. A total of 10 out of 200 patients had a positive mPCR test result at the time of revision. Of these 10 cases, none encountered outcome parameters fulfilling the criteria to diagnose PJIs in the first year after surgery, and one required re-revision surgery for reasons other than infection. Of the other 190 negative mPCR cases, none developed a PJI. A positive mPCR test at the time of presumed aseptic revision surgery did not correspond with intra-operatively obtained tissue cultures, and none of the encountered positive mPCR tests had developed a PJI at the 1-year follow-up. We recommend careful evaluation and monitoring of modern diagnostic tests before widespread use.

Improvement in functional outcome 1 year after nonsurgical multidisciplinary treatment for chronic pain after total knee arthroplasty: A prospective cohort study.

PURPOSE: The purpose of this study was to evaluate a multidisciplinary intervention developed for patients with debilitating chronic pain after total knee arthroplasty (TKA) unresponsive to existing treatment options. METHODS: A treatment-based prospective cohort study was caried out in 30 TKA patients with debilitating chronic pain at least 1 year after TKA. The treatment was a multidisciplinary intervention. Main inclusion criteria: no indication for surgery. Primary outcome was function measured by KOOS-PS, OKS, OKS-APQ and WORQ. Secondary outcome measures were pain, fear of movement, self-efficacy, quality of life (QoL), health care and pain medication use, work rehabilitation and patient satisfaction. The assessments took place pre- and directly posttreatment, at 1, 3 and 12 months follow-up. The clinical relevance was assessed by predefined minimal important clinical change (MCIC). RESULTS: At baseline patients were on average 64.7 (±7.9) years old, 67% were female, and they had knee pain for 42 (10-360) months. The results at 12-month follow-up: first, a significant improvement was shown in function, pain, fear of movement, self-efficacy and QoL. Second, in 38.5%-69.2% of patients clinical relevant improvement was shown for functional outcome, 31% for pain, and 50% for self-efficacy. Third, 42% of patients reported 'no healthcare use in the past three months'. CONCLUSION: One year after a multidisciplinary treatment a clinically relevant improvement was shown in terms of function, pain, self-efficacy and QoL. It seems to be a promising treatment option in this difficult-to-treat patient group with debilitating chronic pain after TKA. Future research should examine the effect of the treatment in a larger study population, considering a control group, and focusing on the working population and evaluating cost-efficacy. LEVEL OF EVIDENCE: Level II.

Prioritization of Adverse Consequences After Total Knee Arthroplasty Contributing to a Poor Response: A Best-Worst Scaling Exercise Among Total Knee Arthroplasty Patients and Knee Specialists.

BACKGROUND: Total knee arthroplasty (TKA) can have a number of adverse consequences for patients that might contribute to a poor outcome. This study aimed to prioritize these consequences, from the perspective of patients and knee specialists. METHODS: There were 95 TKA patients and 63 knee specialists who prioritized a set of 29 adverse consequences, based on a previous qualitative study, using a Maximum Difference Scaling method. A hierarchical Bayesian analysis was used to calculate relative importance scores. Differences and agreements between patients versus knee specialists and satisfied versus dissatisfied patients were analyzed using Mann-Whitney-U tests and Kendall's coefficients of concordance. RESULTS: There were 4 out of 5 items in the top-5 of both patients and knee specialists that were similar, however, the ranking was different. The highest-ranked consequence for patients was: "Inability to do normal activities such as walking, cycling, swimming and heavy household chores", while knee specialists ranked: "No improvement in pain during the day" as the highest. "No improvement in walking" was in the patients' top-5, but was not ranked in the top-5 of knee specialists. For satisfied and dissatisfied patients, the top-5 of consequences was similar. CONCLUSION: Comparable perspectives were found for patients versus knee specialists and satisfied versus dissatisfied patients on the importance of adverse consequences after TKA. However, when looking in more detail, differences in ranking of specific subitems suggest that patients place slightly more importance on the inability to perform valued activities, while knee specialists prioritize lack of pain relief to a higher degree.

Exploration of adverse consequences of total knee arthroplasty by patients and knee specialists: a qualitative study.

Objectives: A successful outcome according to the knee specialist is not a guarantee for treatment success as perceived by patients. In this study, we aimed to explore outcome expectations and experiences of patients with OA before and after total knee arthroplasty (TKA) surgery and knee specialists that might contribute to the negative appraisal of its effect, and differences in views between patients and knee specialists. Methods: Semi-structured interviews were held in Belgium and the Netherlands. Twenty-five patients (2 without indications for TKA, 11 on the waiting list for TKA and 12 postoperative TKA) and 15 knee specialists (9 orthopaedic surgeons, 1 physician assistant, 1 nurse practitioner and 4 physiotherapists) were interviewed. Conversations were audio recorded, transcribed verbatim, and analysed using thematic analysis following the grounded theory approach. Separate analyses were conducted for patients and knee specialists. Results: Patients were focused on the arduous process of getting used to the prosthesis, lingering pain, awareness of the artificial knee and limitations they experience during valued and daily activities, whereas knee specialists put emphasis on surgical failure, unexplained pain, limited walking ability and impairments that limit the physical functioning of patients. Conclusion: This study provides a comprehensive overview of potential adverse consequences from the perspective of both patients and knee specialists. Improving patients' awareness and expectations of adaptation to the knee prosthesis needs to be considered.

Prolonged use of linezolid in bone and joint infections: a retrospective analysis of adverse effects.

OBJECTIVES: Antibiotic treatment for bone and joint infections generally lasts for 6 weeks or longer. Linezolid may be a good option for treating bone and joint infections, but there is an increased risk of potential serious adverse drug events (ADEs) when used for more than 28 days. The aim of this study was to obtain detailed information on the type and time to occurrence of the patient-reported ADEs, the dynamics of haematopoiesis over time, and the reasons for early discontinuation of linezolid when used for an intended maximum duration of 12 weeks. METHODS: This single-centre retrospective study was conducted at the Sint Maartenskliniek in The Netherlands. Patients were included if they were planned to use linezolid for more than 28 days. The main reason for discontinuation of linezolid, the ADE according to the Naranjo score, and the time to occurrence of ADEs were analysed. RESULTS: Among 78 patients, drug toxicity led to early discontinuation of linezolid in 11 (14%) patients before and nine (12%) after 28 days of therapy. The median treatment duration was 42 days. Gastrointestinal intolerance (42%) and malaise (32%) were the most common ADEs. In 75% of the cases the ADE occurred within 28 days of therapy. Sixty-seven patients were able to continue linezolid beyond 28 days, 87% of whom completed therapy as scheduled. Severe cytopenia, according to the Common Terminology Criteria for Adverse events (CTCA), was observed in four patients and was reversible after discontinuation of linezolid. One patient suffered optic neuropathy related to linezolid use. CONCLUSIONS: Linezolid could be considered an alternative option to the current standard of IV glycopeptides for the treatment of bone and joint infection for up to 12 weeks. If patients pass the first 28 days of therapy, the likelihood of successful completion of therapy is high with a low risk of serious ADEs.

No Association Between Hospital Volume and Early Second Revision Rate in Revision Total Knee Arthroplasty in the Dutch Orthopaedic Register.

BACKGROUND: Revision knee arthroplasty (R-KA) is rising globally. Technical difficulty of R-KA varies from liner exchange to full revision. Centralization has been shown to reduce mortality and morbidity rates. The present study aimed to evaluate the association between hospital R-KA volume and overall second revision rate, as well as revision rate for different types of revision. METHODS: The R -KAs between 2010 and 2020 with available data on the primary KA in the Dutch Orthopaedic Arthroplasty Register were included. Minor revisions were excluded. Implant data and anonymous patient characteristics were obtained from the Dutch Orthopaedic Arthroplasty Register. Survival analyses and competing risk analysis were performed per volume category (≤12, 13 to 24, or ≥25 cases/year) at 1, 3, and 5 years following R-KA. There were 8,072 R-KA cases available. Median follow-up was 3.7 years (range 0 to 13.7 years). There were a total of 1,460 second revisions (18.1%) at the end of follow-up. RESULTS: There were no statistically significant differences between second revision rates of the three volume groups. Adjusted hazard ratio for second revision were 0.97 (Confidence Interval (CI) 0.86 to 1.11) for hospitals with 13 to 24 cases/year and 0.94 (CI 0.83 to 1.07) with ≥25 cases/year compared to low volume (≤12 cases/year). Type of revision did not influence second revision rate. CONCLUSION: Second revision rate of R-KA does not seem to be dependent on hospital volume or type of revision in the Netherlands. LEVEL OF EVIDENCE: Level IV, Observational registry study.

Acceptable migration of a fully cemented rotating hinge-type knee revision system measured in 20 patients with model-based RSA with a 2-year follow-up.

BACKGROUND AND PURPOSE: Rotating hinged knee implants are highly constrained prostheses used in cases in which adequate stability is mandatory. Due to their constraint nature, multidirectional stresses are directed through the bone-cement-implant interface, which might affect fixation and survival. The goal of this study was to assess micromotion of a fully cemented rotating hinged implant using radiostereometric analysis (RSA). PATIENTS AND METHODS: 20 patients requiring a fully cemented rotating hinge-type implant were included. RSA images were taken at baseline, 6 weeks, and 3, 6, 12, and 24 months postoperatively. Micromotion of femoral and tibial components referenced to markers in the bone was assessed with model-based RSA software, using implant CAD models. Total translation (TT), total rotation (TR), and maximal total point motion (MTPM) were calculated (median and range). RESULTS: At 2 years, TTfemur was 0.38 mm (0.15-1.5), TRfemur was 0.71° (0.37-2.2), TTtibia was 0.40 mm (0.08-0.66), TRtibia was 0.53° (0.30-2.4), MTPMfemur was 0.87 mm (0.54-2.8), and MTPMtibia was 0.66 mm (0.29-1.6). Femoral components showed more outliers (> 1 mm, > 1°) compared with tibial components. CONCLUSION: Fixation of this fully cemented rotating hinge-type revision implant seems adequate in the first 2 years after surgery. Femoral components showed more outliers, in contrast to previous RSA studies on condylar revision total knee implants.

Fluoroscopic and radiostereometric analysis of a bicruciate-retaining versus a posterior cruciate-retaining total knee arthroplasty: a randomized controlled trial.

AIMS: The aim of this study was to compare a bicruciate-retaining (BCR) total knee arthroplasty (TKA) with a posterior cruciate-retaining (CR) TKA design in terms of kinematics, measured using fluoroscopy and stability as micromotion using radiostereometric analysis (RSA). METHODS: A total of 40 patients with end-stage osteoarthritis were included in this randomized controlled trial. All patients performed a step-up and lunge task in front of a monoplane fluoroscope one year postoperatively. Femorotibial contact point (CP) locations were determined at every flexion angle and compared between the groups. RSA images were taken at baseline, six weeks, three, six, 12, and 24 months postoperatively. Clinical and functional outcomes were compared postoperatively for two years. RESULTS: The BCR-TKA demonstrated a kinematic pattern comparable to the natural knee's screw-home mechanism in the step-up task. In the lunge task, the medial CP of the BCR-TKA was more anterior in the early flexion phase, while laterally the CP was more posterior during the entire movement cycle. The BCR-TKA group showed higher tibial migration. No differences were found for the clinical and functional outcomes. CONCLUSION: The BCR-TKA shows a different kinematic pattern in early flexion/late extension compared to the CR-TKA. The difference between both implants is mostly visible in the flexion phase in which the anterior cruciate ligament is effective; however, both designs fail to fully replicate the motion of a natural knee. The higher migration of the BCR-TKA was concerning and highlights the importance of longer follow-up.Cite this article: Bone Joint J 2023;105-B(1):35-46.

Novel metaphyseal porous titanium cones allow favorable outcomes in revision total knee arthroplasty.

INTRODUCTION: Loosening and migration are common modes of aseptic failure following complex revision total knee arthroplasty (rTKA). Metaphyseal cones allow surgeons to negotiate the loss of femoral and tibial bone stock while obtaining stable bony fixation. This study examines the mid-term functional and radiographic outcomes in patients undergoing rTKA utilizing a novel metaphyseal cone system with stems of variable length and fixation methods. METHODS: This two-center retrospective study examined all patients who underwent rTKA with a novel porous, titanium tibial or femoral cone in combination with a stem of variable length and fixation who had a minimum follow-up of 2-years. Outcome analysis was separated into tibial and femoral cones as well as the stem fixation method (hybrid vs. fully cemented). RESULTS: Overall, 123 patients who received 156 cone implants were included (74 [60.2%] tibial only, 16 [13.0%] femoral only, and 33 [26.8%] simultaneous tibial and femoral) with a mean follow-up of 2.76 ± 0.66 years. At 2-years of follow-up the total cohort demonstrated 94.3% freedom from all-cause re-revisions, 97.6% freedom from aseptic re-revisions, and 99.4% of radiographic cone osteointegration. All-cause revision rates did not differ between stem fixation techniques in both the tibial and femoral cone groups. CONCLUSION: The use of a novel porous titanium femoral and tibial metaphyseal cones combined with stems in patients with moderate to severe bone defects undergoing complex revision total knee arthroplasty confers excellent results independent of stem fixation technique. LEVEL OF EVIDENCE: IV, case series.

Higher 1-year risk of implant removal for culture-positive than for culture-negative DAIR patients following 359 primary hip or knee arthroplasties.

Background and purpose: To date, the value of culture results after debridement, antibiotics, and implant retention (DAIR) for early (suspected) prosthetic joint infection (PJI) as risk indicators in terms of prosthesis retention is not clear. At the 1-year follow-up, the relative risk of prosthesis removal was determined for culture-positive and culture-negative DAIR patients after primary total hip or knee arthroplasty. The secondary aim of this work was to explore differences in patient characteristics, infection characteristics, and outcomes between these two groups. Methods: A retrospective regional registry study was performed in a group of 359 patients (positive cultures: n = 299 ; negative cultures: n = 60 ) undergoing DAIR for high suspicion of early PJI in the period from 2014 to 2019. Differences in patient characteristics, the number of deceased patients, and the number of subsequent DAIR treatments between the culture-positive and culture-negative DAIR groups were analysed using independent t  tests, Mann-Whitney U  tests, Pearson's chi-square tests, and Fisher's exact tests. Results: The overall implant survival rate following DAIR was 89 %. The relative risk of prosthesis removal was 7.4 times higher (95 % confidence interval (CI) 1.0-53.1) in the culture-positive DAIR group (37 of 299, 12.4 %) compared with the culture-negative DAIR group (1 of 60, 1.7 %). The culture-positive group had a higher body mass index ( p = 0.034 ), a rate of wound leakage of > 10  d ( p = 0.016 ), and more subsequent DAIR treatments ( p = 0.006 ). Interpretation: As implant survival results after DAIR are favourable, the threshold to perform a DAIR procedure for early (suspected) PJI should be low in order to retain the prosthesis. A DAIR procedure in the case of negative cultures does not seem to have unfavourable results in terms of prosthesis retention.

No difference in long-term micromotion between fully cemented and hybrid fixation in revision total knee arthroplasty: a randomized controlled trial.

AIMS: Both the femoral and tibial component are usually cemented at revision total knee arthroplasty (rTKA), while stems can be added with either cemented or press-fit (hybrid) fixation. The aim of this study was to compare the long-term stability of rTKA with cemented and press-fitted stems, using radiostereometric analysis (RSA). METHODS: This is a follow-up of a randomized controlled trial, initially involving 32 patients, of whom 19 (nine cemented, ten hybrid) were available for follow-up ten years postoperatively, when further RSA measurements were made. Micromotion of the femoral and tibial components was assessed using model-based RSA software (RSAcore). The clinical outcome was evaluated using the Knee Society Score (KSS), the Knee injury and Osteoarthritis Outcome Score (KOOS), and visual analogue scale (pain and satisfaction). RESULTS: The median total femoral translation and rotation at ten years were 0.39 mm (interquartile range (IQR) 0.20 to 0.54) and 0.59° (IQR 0.46° to 0.73°) for the cemented group and 0.70 mm (IQR 0.15 to 0.77) and 0.78° (IQR 0.47° to 1.43°) for the hybrid group. For the tibial components this was 0.38 mm (IQR 0.33 to 0.85) and 0.98° (IQR 0.38° to 1.34°) for the cemented group and 0.42 mm (IQR 0.30 to 0.52) and 0.72° (IQR 0.62° to 0.82°) for the hybrid group. None of these values were significantly different between the two groups and there were no significant differences between the clinical scores in the two groups at this time. There was only one re-revision, in the hybrid group, for infection and not for aseptic loosening. CONCLUSION: These results show good long-term fixation with no difference in micromotion and clinical outcome between fully cemented and hybrid fixation in rTKA, which builds on earlier short- to mid-term results. The patients all had type I or II osseous defects, which may in part explain the good results. Cite this article: Bone Joint J 2022;104-B(7):875-883.

Limited effect of anatomical insert geometry on in vitro laxity in balanced anatomic posterior cruciate ligament retaining total knee arthroplasty.

PURPOSE: The present study assessed the effect of insert articular surface geometry (anatomical versus conventional insert design) on anteroposterior (AP) translation and varus-valgus (VV) laxity in balanced posterior cruciate ligament (PCL) retaining total knee arthroplasty (TKA). Secondly, we evaluated if the AP translation and VV laxity in the reconstructed knee resembled the stability of the native knee. METHODS: Nine fresh-frozen full-leg cadaver specimens were used in this study. After testing the native knee, anatomical components of a PCL-retaining implant were implanted. The knee joints were subjected to anteriorly and posteriorly directed forces (at 20° and 90° flexion) and varus-valgus stresses (at 20°, 45° and 90° flexion) in both non-weightbearing and weightbearing situations in a knee kinematics simulator. Measurements were performed in the native knee, TKA with anatomical insert geometry (3° built-in varus, medial concave, lateral convex), and TKA with symmetrical insert geometry. RESULTS: In weightbearing conditions, anterior translations ranged between 2.6 and 3.9 mm at 20° flexion and were < 1 mm at 90° flexion. Posterior translation at 20° flexion was 2.7 mm for the native knee versus 4.0 mm (p = 0.047) and 7.0 mm (p = 0.02) for the symmetrical insert and the anatomical insert, respectively. Posterior translation at 90° flexion was < 1.1 mm and not significantly different between the native knee and insert types. In non-weightbearing conditions, the anterior translation at 20° flexion was 5.9 mm for the symmetrical and 4.6 mm for the anatomical insert (n.s.), compared with 3.0 mm for the native knee (p = 0.02). The anterior translation at 90° flexion was significantly higher for the reconstructed knees (anatomical insert 7.0 mm; symmetrical insert 9.2 mm), compared with 1.6 mm for the native knee (both p = 0.02). Varus-valgus laxity at different flexion angles was independent of insert geometry. A valgus force in weightbearing conditions led to significantly more medial laxity (1°-3° opening) in the native knee at 45° and 90° flexion compared with the reconstructed knee for all flexion angles. CONCLUSIONS: Insert geometry seems to have a limited effect with respect to AP translation and VV laxity, in the well-balanced PCL-retaining TKA with an anatomical femoral component. Secondly, AP translation and VV laxity in the reconstructed knee approximated the laxity of the native knee.

Short- to Midterm Outcomes of a Novel Guided-Motion Rotational Hinged Total Knee Arthroplasty.

Hinged prostheses have been increasingly utilized in complex and revision total knee arthroplasty (TKA) cases requiring additional mechanical support and global stability. However, there is limited data detailing the outcomes of modern hinge designs in these procedures. The aim of this study is to report a minimum 2-year functional outcomes and survivorship of a novel-guided motion-hinged knee TKA system. A multicenter, retrospective cohort study was conducted on consecutive TKA patients between March 2013 and August 2017 with a novel-guided motion-hinged knee system. Demographics, change in range of motion (ΔROM), quality metrics, and implant survivorship were collected with a minimum of 2-year follow-up. Implant survival was analyzed by using the Kaplan-Meier method. Overall, 147 hinged knee cases (18 complex primaries and 129 revisions) were identified with an average follow-up duration of 3.8 ± 1.2 years. Patients presented with an average of 2.4 ± 1.6 prior knee surgeries, and 51 (34.7%) had a history of knee infections. The ROM improved postoperatively: Δ extension = 2 ± 1 degrees, Δflexion = 7 ± 3 degrees, Δtotal ROM = 9 ± 4 degrees. Kaplan-Meier survivorship analysis for implant revision at 2- and 5-year follow-up showed a survival rate of 100 and 98.5% (95% confidence interval: 94.3-99.6%), respectively, with one patient undergoing two-stage revision for infection and another undergoing femoral revision for aseptic loosening. Survivorship for aseptic all-cause reoperation at 2- and 5-year follow-up was 93.2% (87.7-96.3%) and 88.2% (80.0-93.2%), respectively. Fourteen patients underwent aseptic reoperation (patellar complications: n = 7 [4.8%]; instability: n = 5 [3.4%]; tuberosity fixation: n = 1 [0.7%]; extensor mechanism failure: n = 1 [1.1%]). Survivorship for all-cause reoperation at 2- and 5-year follow-up were 85% (78.2-90.0%) and 77.7% (68.8-84.3%), respectively. Fifteen patients underwent reoperation for infection (DAIR: n = 14 (9.5%); two-stage revision: n = 1 [0.7%]). Despite some reoperations, this guided-motion hinged-knee TKA system demonstrates excellent survivorship for component revision compared to other modern hinged knee implants reported in the literature. Patients also displayed an improvement in knee ROM at their latest follow-up.

Supine Traction Versus Prone Bending Radiographs for Assessing the Curve Flexibility in Spinal Deformity.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: No consensus exists among surgeons on which radiologic method to prefer for the assessment of curve flexibility in spinal deformity. The objective of this study was to evaluate the difference in curve correction on supine traction radiographs versus prone side bending radiographs. METHODS: A retrospective analysis of idiopathic scoliosis (IS), degenerative idiopathic scoliosis (DIS) and de novo degenerative lumbar scoliosis (DNDLS) patients was performed on supine traction as well as prone bending films (when available). Age, weight, traction force, diagnosis and Cobb angles of the primary and secondary curves were extracted. Differences in curve correction (percentages) on traction versus prone bending radiographs were analyzed for the primary and secondary curve. Subgroup analyses were performed for the 3 different diagnoses. RESULTS: In total, 170 patients were eligible for inclusion. 43 were diagnosed with IS, 58 with DIS and 69 with DNDLS. For the primary curve, greater curve correction was obtained with bending in the DNDLS group (P < 0.001). In the DIS group, there was a trend toward more correction on bending (P = 0.054). In de IS group no difference was found. For the secondary curve, bending showed more curve correction in the IS and DIS group (P = 0.002 and P <0.001). No difference was found in the DNDLS group. CONCLUSION: Compared to traction radiographs, bending radiographs better serve the purpose of curve flexibility assessment of IS, DIS and DNDLS spinal deformity, despite the fact that patients are exposed to more radiation.

Superior Survival of Fully Cemented Fixation Compared to Hybrid Fixation in a Single Design Rotating Hinge Knee Implant.

BACKGROUND: Clinical observations revealed higher rates of aseptic loosening for hybrid fixated rotating hinge knee implants compared to fully cemented ones. We hypothesize that the use of a fully cemented fixation technique had a higher survival rate for aseptic loosening compared to a hybrid fixation technique in a rotating hinge knee implant. METHODS: All procedures of patients who were treated with the RT-PLUS rotating hinge knee implant (Smith & Nephew, Memphis, TN) between 2010 and 2018 were included. Primary outcome was revision for aseptic loosening. Kaplan-Meier survivorship and Cox proportional hazard regression analysis were performed to calculate survival rates and hazard ratios. RESULTS: A total of 275 hinge knee implants were placed in 269 patients (60 primary procedures, 215 revisions). Median follow-up was 7.3 ± 3.9 years. In total, 24 components (16 hybrid femur, 2 fully cemented femur, 6 hybrid tibia; all revision procedures) in 19 patients were revised for aseptic loosening. Kaplan-Meier survivorship analysis showed superior survival rates of fully cemented components (femur 97.1%; tibia 100%) compared to hybrid fixated components (femur 89.5%; tibia 95.9%) at the 10-year follow-up. Multivariate Cox hazard analysis showed a significantly higher risk of aseptic loosening for hybrid fixated components, a prior stemmed component and the femoral component. CONCLUSION: Fully cemented fixation showed superior survival rates for aseptic loosening compared to hybrid fixation in a single design rotating hinge knee implant. A prior stemmed component appears to be a risk factor for aseptic loosening and the femoral component seems to be more prone to loosening.

Translation, cross-cultural adaptation, reliability and construct validity of the Dutch Oxford Knee Score - Activity and Participation Questionnaire.

BACKGROUND: Patients undergoing total knee arthroplasty (TKA) tend to be younger and tend to receive TKA at an earlier stage compared to 20 years ago. The Oxford Knee Score - Activity and Participation (OKS-APQ) questionnaire evaluates higher levels of activity and participation, reflecting activity patterns of younger or more active people. The purpose of this study was to translate the OKS-APQ questionnaire into Dutch, and to evaluate its measurement properties in pre- and postoperative TKA patients. METHODS: The OKS-APQ was translated and adapted according to the forward-backward translation multi step approach and tested for clinimetric quality. Floor and ceiling effects, structural validity, construct validity, internal consistency and test-retest reliability were evaluated using COSMIN quality criteria. The OKS-APQ, the Oxford Knee Score (OKS), the Short Form-36 (SF-36), a Visual Analogue Scale (VAS) for pain and the Forgotten Joint Score (FJS) were assessed in 131 patients (72 preoperative and 59 postoperative TKA patients), and the OKS-APQ was administered twice in 50 patients (12 preoperative and 38 postoperative TKA patients), after an interval of minimal 2 weeks. RESULTS: Floor effects were observed in preoperative patients. Confirmatory factor analyses (CFA) indicated a good fit of a 1-factor model by the following indices: (Comparative Fit Index (CFI): 0.97, Tucker-Lewis Index (TLI): 0.96 and Standardized Root Mean Square Residual (SRMR): 0.03). Construct validity was supported as > 75% of the hypotheses were confirmed. Internal consistency (Cronbach α's from 0.81 to 0.95) was good in the pooled and separate pre- and postoperative samples and test-retest reliability (Intraclass Correlation Coefficients (ICCs) from 0.63 - 0.85) were good in postoperative patients and moderate in preoperative patients. The standard Error of Measurements (SEMs) ranged from 8.5 - 12.2 and the Smallest Detectable Changes in individuals (SDCind) ranged from 23.5 - 34.0 (on a scale from 0 to 100). CONCLUSIONS: Preliminary findings suggest that the Dutch version of the OKS-APQ is reliable and valid for a Dutch postoperative TKA patient sample. However, in a preoperative TKA sample, the OKS-APQ seems less suitable, because of floor effects and lower test-retest reliability. The Dutch version of the OKS-APQ can be used alongside the OKS to discriminate among levels of activity and participation in postoperative patients.

Ruling out underlying infection in 200 presumed aseptic knee and hip revision arthroplasties using a multiplex PCR system.

Ruling out an infection in one-stage knee and hip revisions for presumed aseptic failure by conventional tissue cultures takes up to 14 days. Multiplex polymerase chain reaction (mPCR) is a quick test (4-5 h) for detecting pathogens. The purpose of this study was to evaluate the diagnostic accuracy of an automated mPCR of synovial fluid obtained intraoperatively in unsuspected knee and hip revisions. A prospective study was conducted with 200 patients undergoing a one-stage knee or hip revision. Synovial fluid was analyzed with the mPCR Unyvero implant and tissue infection G2 cartridge (U-ITI G2) system and compared to intraoperative tissue cultures. The primary outcome measure was the diagnostic accuracy, including sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), of the mPCR U-ITI G2 system compared to conventional cultures. In the knee revision group, there were no patients with a positive mPCR in combination with positive cultures. This resulted in a non-calculable sensitivity and PPV. The specificity and NPV in the knee revision group of the mPCR compared to tissue cultures was 96.8% and 96.8%, respectively. In the hip revision group, the sensitivity, specificity, PPV, and NPV of the mPCR compared to tissue cultures was 36.4%, 96.6%, 57.1%, and 92.5%, respectively. Sixteen mismatches occurred between the mPCR and tissue cultures. The mPCR U-ITI G2 system is a quick and reliable synovium fluid test for ruling out infection in presumed aseptic knee and hip revisions with a high NPV compared with tissue cultures, although some mismatches were observed. Periprosthetic tissue cultures are still advised as back-up for false negative and positive mPCR test results.

Instability, an unforeseen diagnosis of the Legion™ hinge knee system.

BACKGROUND: Instability is an infrequently encountered diagnosis in rotating hinge knee (rHK) implants. With the introduction of a new rHK implant, we encountered multiple patients who complained of instability. This article presents its prevalence while describing our diagnostic and treatment algorithms. METHODS: A retrospective analysis of a cohort of all consecutive patients treated with the Legion™ Hinge Knee System (Smith&Nephew, Memphis, Tennessee) as primary or revision procedure between July 2014 and December 2018 was performed. All patients reporting a sense of instability or having recurrent joint effusion after activity were suspected of experiencing instability. Stress X-rays were performed and brace treatment was started. In patients with insufficient effect of brace treatment, a liner exchange to a thicker liner was performed. Prevalence of instability and the effect of treatment was analysed descriptively. RESULTS: In total, six patients were categorized as patients having instability problems (prevalence 3.5%; male:female ratio 5:1; median age 69.5 years; all revision procedures). Indication for revision to the Legion rHK implant was infection (three), instability (two) and aseptic loosening (one). In two patients, a prior rHK implant was revised. All patients showed tilting beyond the tolerance on stress X-ray examination. Brace treatment was adequate in three patients; in the other three patients a liner exchange was performed, two of which were satisfied. CONCLUSION: Instability is an infrequently encountered diagnosis in rHK implants. The design of the Legion rHK implant seems prone to this problem with a prevalence of 3.5%. If brace treatment is insufficient a liner exchange might be considered.