Early migration in unicompartmental knee arthroplasty: a radiostereometric study of 26 patients with 24 months of follow-up.

BACKGROUND AND PURPOSE: Aseptic loosening, mainly caused by migration, is one of the most common indications for revisions in unicompartmental knee arthroplasty (UKA). In this study, we investigated the early migration of the Persona Partial Knee (PPK, Zimmer Biomet, Warsaw, IN), a cemented medial fixed-bearing unicompartmental knee prosthesis, and evaluated the clinical results. PATIENTS AND METHODS: 26 primary PPKs were implanted. Radiographs were obtained direct postoperatively, at 6 weeks, 6, 12 and 24 months postoperatively. Migration of the femoral and tibial component was calculated using model-based radiostereophotogrammetric analysis (mRSA) in terms of translations and rotations. Patient-reported outcome measures (PROMs) were also registered. RESULTS: At 24 months postoperatively, we found low migration of both the femoral and tibial component in the first 6 months, after which both components stabilized. Only the rotation of the tibial component about the z-axis did not stabilize. All PROMs improved after 24 months compared with preoperative PROMs. CONCLUSION: The Persona Partial Knee shows low migration of both the femoral and tibial component and PROMs were improved at 24 months follow-up. Long-term follow-up is needed to investigate the performance of the prosthesis compared with other prostheses.

No effect of fixation type on early and late mortality after total knee arthroplasty: a Dutch arthroplasty register study.

PURPOSE: Postoperative mortality is commonly reported as outcome measurement after total knee arthroplasty (TKA). Mortality might be influenced by multiple factors including cementation of the prosthesis. Until now, the influence of cementation on early and late mortality after TKA is unknown. The aim of the present study was to determine the effect of fixation on early and late mortality after primary TKA. METHODS: All patients in the Dutch Arthroplasty Register (LROI) with a primary TKA for osteoarthritis were eligible for inclusion. Data collected from 2007 to 2014 with follow-up until January 2020 were used. Survival analysis was performed by using Kaplan-Meier and Cox survival analysis to determine the mortality rate according to fixation. Adjustments were made for age at time of surgery, gender, American Society of Anaesthesiologists class, and year of surgery. RESULTS: In total 108,687 TKA were included for analysis, which comprised 95,857 cemented, 6,140 cementless and 6,690 hybrid TKA. The early and late mortality rate in cemented TKA was statistically not different compared to cementless or hybrid TKA at 30 days, 31-90 days, 91 days-1 year and 1-5 years. The hazard ratio at 30 days was 1.05 (CI 0.49-2.25) for hybrid fixation, and 1.46 (CI 0.74-2.90) for cementless fixation compared to cemented fixation. The 1-5 years hazard ratio was 1.06 (CI 0.96-1.17) and 0.97 (CI 0.87-1.08), respectively. CONCLUSION: Based on register data, method of fixation does not influence early mortality after primary TKA. This suggests that there is no preferred fixation technique for primary TKA based on the mortality rates. LEVEL OF EVIDENCE: IV.

Short-term functional outcome after fast-track primary total knee arthroplasty: analysis of 623 patients.

Background and purpose - Early functional outcome after total knee arthroplasty (TKA) has been described before, but without focus on the presence of certain functional recovery patterns. We investigated patterns of functional recovery during the first 3 months after TKA and determined characteristics for non-responders in functional outcome.Patients and methods - All primary TKA in a fast-track setting with complete patient-reported outcome measures (PROMs) preoperatively, at 6 weeks, and 3 months postoperatively were included. Included PROMs were Oxford Knee Score (OKS), Knee disability and Osteoarthritis Outcome Score Physical Function Short-Form (KOOS-PS), and EuroQol 5 dimensions (EQ-5D) including the self-rated health Visual Analogue Scale (VAS). Patients with improvement on OKS less than the minimal clinically important difference (MCID) were determined as non-responders at that time point. Characteristics between groups of responders and non-responders in functional recovery were tested for differences: we defined 4 groups a priori, based on the responder status at each time point.Results - 623 patients were included. At 6 weeks OKS, KOOS-PS, and EQ-5D self-rated health VAS were statistically significant improved compared with preoperative scores. The mean improvement was clinically relevant at 6 weeks for KOOS-PS and at 3 months for OKS. Patient characteristics in non-responders were higher BMI and worse scores on EQ-5D items: mobility, self-care, usual activities, and anxiety/depression.Interpretation - Both statistically significant and clinically relevant functional improvement were found in most patients during the first 3 months after primary TKA. Presumed modifiable patient characteristics in non-responders on early functional outcome were BMI and anxiety/depression.

Comparable mid-term revision rates of primary cemented and cementless total knee arthroplasties in 201,211 cases in the Dutch Arthroplasty Register (2007-2017).

PURPOSE: Long-term failure of total knee arthroplasty (TKA) is mostly due to loosening of the prosthesis. In this study, the short- and mid-term revision rates of cemented vs cementless TKAs were investigated. Comparable short- and mid-term survival rates of both fixation methods were expected. METHODS: Data on all cemented and cementless TKAs performed between 2007 and 2017 were retrieved from the Dutch Arthroplasty Register. The cumulative crude incidence of revision of cemented and cementless TKA was calculated. Death was considered a competing risk. Revision rates were compared using multivariable Cox proportional hazard regression analysis. The associations between fixation method and type of revision or reason for revision were tested using logistic regression analyses. RESULTS: In total, 190,651 (94.8%) cemented and 10,560 (5.3%) cementless TKAs were evaluated. Both groups had comparable case characteristics. Cemented TKAs were inserted more often in cases with previous knee surgery compared to cementless TKAs (32% vs 27%). The cumulative incidence of revision after 9 years was 5.5% (CI 5.3-5.6%) for cemented and 5.8% (CI 5.2-6.4%) for cementless TKAs (p = 0.2). Cementless TKAs were more often revised due to loosening of the tibial (27% vs 18%; p < 0.001) or the femoral component (7% vs 5%; p = 0.005) than cemented TKAs. Cemented TKAs were more often revised due to infection (17% vs 9%; p = 0.004) than cementless TKAs. CONCLUSION: In conclusion, cemented and cementless TKAs have comparable short- and mid-term revision rates based on a nationwide register study. LEVEL OF EVIDENCE: III.

Rationale and design of the PaTIO study: PhysiotherApeutic Treat-to-target Intervention after Orthopaedic surgery.

BACKGROUND: Physiotherapy is a proven effective treatment strategy after total knee and hip arthroplasty (TKA/THA), however there is considerable practice variation regarding its timing, content and duration. This study aims to compare the (cost-) effectiveness of a standardized, treat-to-target postoperative physiotherapy strategy with usual postoperative care. METHODS: Using a cluster randomized study design, consecutive patients scheduled for a primary TKA/THA in 18 hospitals in the Netherlands will be assigned to the treat-to-target physio therapy strategy or usual postoperative care. With the treat-to-target strategy a standardized, individually tailored, exercise program is aimed at the attainment of specific functional milestones. Assessments are done at baseline, 6 weeks and 3, 6, 9 and 12 months follow up. The primary outcome will be the Knee injury / Hip disability and Osteoarthritis Outcome Score - Physical Function Short Form (KOOS-PS / HOOS-PS) at 3 months follow up. Secondary outcomes are the numeric rating scale for pain, the Oxford Knee and Hip Scores, performance-based test and the EuroQol 5D-5L for quality of life. Healthcare use, productivity and satisfaction with postoperative care are measured by means of questionnaires. In total, 624 patients will be needed of which 312 TKA and 312 THA patients. DISCUSSION: The study will provide evidence concerning the (cost-) effectiveness of the treat-to-target postoperative physiotherapy treatment compared to usual postoperative care. The results of this study will address an important evidence gap and will have a significant impact in daily practice of the physio therapist. TRIAL REGISTRATION: Registered in the Dutch Trial Registry on April 15, 2018. Registration number: NTR7129 .

Reliability of two different measuring techniques with computer tomography for penetration and distribution of cement in the proximal tibia after total knee arthroplasty.

BACKGROUND: To evaluate the reliability of two different techniques for measuring penetration and distribution of the cement mantle in the proximal tibia after total knee arthroplasty (TKA) with Computer Tomography (CT) in vivo. METHODS: Standardized CT scans of the proximal tibia were taken 1 to 2 years after total knee arthroplasties implanted with a surface cementing technique. These prospectively acquired transversal CT images of the surface of the proximal tibia were divided into four quadrants and were assessed once manually and once with a numerical computing program (MATLAB® Update 2, The MathWorks, Inc.) based on Hounsfield Units by one of the researchers. The assessments were repeated by the same and a second researcher. The ratio cement/trabecular bone was calculated 1, 3 and 5 mm distal of the tibia tray per quadrant. Kruskall-Wallis tests with multiple pairwise comparisons (Dunn's test) were used to determine differences between the quadrants. Intra- and inter-rater reliability as well as the inter method reliability were assessed with the Intraclass Correlation Coefficient (ICC) per level of depth and with Bland-Altman plots. RESULTS: A total of 92 CT scans were included. The intra- and inter-rater reliability of the manual method ranged from 0.22 and 0.52. The intra- and inter-rater reliability of the matlab method varied between 0.98 to 0.99. The median percentage cement measured with the matlab method 1 mm underneath the tibial tray varied between 82 and 88%; at 3 mm depth between 38 and 54% and at 5 mm between 15 and 25%. There was significantly (p < 0.05) less cement in the antero-medial quadrant compared to the antero-lateral and postero-lateral quadrant at 3 mm and 5 mm depth. CONCLUSIONS: Distribution and penetration of cement in the proximal tibia in a total knee arthroplasty can be measured reliably with CT in combination with the matlab method presented in this manuscript. This method can be used for clinical purposes as well as for scientific research. TRIAL REGISTRATION: METC-nr: 06-104 Dossier NL14807.098.06/versie 06.

The Correlation of Shoe Size and Component Size of Primary Total Knee Arthroplasty.

Preoperative planning is an important phase of total joint arthroplasty. Current template programs and methods only provide moderate accuracy for implant size prediction. Recently, a relationship between shoe size and implant size was found. We hypothesized that shoe size shows a high percentage of agreement for implant size of both femoral and tibial component size in primary total knee arthroplasty (TKA). The aim of this study was to investigate the correlation and agreement between shoe size and TKA implant size. We performed a retrospective cohort study. Of all patients, who underwent primary TKA between September 2013 and March 2016, shoe size and knee implant sizes were collected. Cross-tabulation was used to determine the correlation and agreement between shoe size and implant size. A total of 489 patients (498 TKA) were included. The correlation coefficient for femoral and tibial component with shoe size was 0.751 and 0.759, respectively. When a deviation of ± 1 component size was allowed, shoe size gave at least 94% agreement score for femoral component and at least 86% agreement score in tibial component. We conclude that both femoral and tibial component size have a good correlation with shoe size. Therefore, shoe size may be used as a valuable predictor in preoperative implant size planning for primary TKA. The level of evidence for this study was Level IV.

Gait quality assessed by trunk accelerometry after total knee arthroplasty and its association with patient related outcome measures.

BACKGROUND: With an increasingly younger population and more active patients, assessment of functional outcome is more important than ever in patients undergoing total knee arthroplasty. Accelerometers have been used successfully to objectively evaluate gait quality in other fields. The aim of this study was to assess gait quality with accelerometers before and after surgery, and to assess added value of resulting parameters to patient reported outcome measures scores. METHODS: Sixty-five patients (mean age 65 years (range 41-75)) who underwent primary total knee arthroplasty were evaluated using a tri-axial trunk accelerometer preoperatively and 1 year after surgery. Gait quality parameters derived from the accelerometry data were evaluated in three dimensions at both time points. Factor analysis was performed on all outcome variables and changes from before to 1 year after surgery in the most representative variable for each factor were studied. FINDINGS: Factor analysis identified three separate gait quality factors, with questionnaire and gait quality parameters loading on different factors. Both gait quality factor scores and questionnaire factor scores improved significantly 1 year after surgery. As expected based on the factor analysis, only weak to moderate associations were found between patient reported outcome measures and gait quality before surgery, after surgery and in change scores. INTERPRETATION: The independence of patient reported outcome measures and gait quality parameters measured with trunk accelerometry indicates that gait quality parameters provide additional information on functional outcome after total knee arthroplasty. Providing caretakers with objectively measurable targets using accelerometry could help improve outcome of these patients.

Optimal dose of intrathecal isobaric bupivacaine in total knee arthroplasty.

PURPOSE: Early mobilization is an important aspect of fast-track protocols and intrathecal bupivacaine is often used in primary total knee arthroplasty (TKA). Although the optimal dose is not known, conventional doses leave patients unable to mobilize for two to four hours. The dose of an intrathecally administered local anesthetic should therefore be optimized to achieve immediate postoperative mobilization. This study determined the median effective dose (ED) of intrathecal bupivacaine for primary unilateral TKA. METHODS: Between April 2016 and February 2017 all patients who qualified for unilateral primary TKA were eligible for inclusion. In this dose-finding study, the up-and-down method by Dixon and Massey was used, which is a sequential allocation model. Patients received a dose of isobaric bupivacaine according to the outcome of the preceding patient with an initial starting dose of 5 mg. The dose was increased or decreased by steps of 0.5 mg, depending on the outcome of the preceding patient. During surgery, patients were closely monitored for indications of pain. Time points of regaining motor and sensory functions were determined. RESULTS: Twenty-five patients were included. Mean (SD) age was 70.1 (8.8) yr old, median [IQR] body mass index was 29.5 [27.3-30.9 kg·m-2], and 48% were female. In 11 patients the dose was inadequate; of these, nine patients needed additional anesthesia during surgery, and in four of these nine patients a conversion to general anesthesia was required. The median ED was 3.5 (95% confidence interval [CI], 3.1 to 4.0) mg of intrathecal bupivacaine. The calculated ED50 was 3.4 (95% CI, 2.7 to 4.0) mg; the calculated ED95 was 5 (95% CI, 3.7 to 8.0) mg. CONCLUSION: In this small study with tight control over operative duration, the median effective dosage of intrathecal isobaric bupivacaine for primary unilateral TKA was 3.5 mg and the ED95 was 5 mg. Reduction of conventional dosages of intrathecal bupivacaine is feasible at centres using fast-track arthroplasty protocols.

The open-modified Bankart procedure: long-term follow-up 'a 16-26-year follow-up study'.

INTRODUCTION: A Bankart procedure is a surgical technique for the repair of recurrent shoulder joint dislocations. This study reports the long-term results of the 'open'-modified Bankart procedure. METHODS: We performed a retrospective cohort study in which patients are studied who had open-modified Bankart surgery for instability problems in the absence of a substantial osseous glenoid defect after a traumatic shoulder dislocation, 16-26 years ago, in a large regional hospital. Instability was measured with the Rowe and Oxford shoulder instability score. Furthermore, we measured physical functioning with the Constant-Murley score and the Dutch simple shoulder test. Pain was measured with the NRS for pain. Osteoarthritis was scored according the Samilson-Prieto score. Quality of life was measured with the SF-12 score. The operated shoulder was compared to the non-operated contralateral shoulder regarding instability and osteoarthritis. RESULTS: 39 patients were included with an average follow-up of 21 years (range 16-26 years). The number of patients with redislocations of their shoulder after surgery was 4 (10%). 23% of the study group described moments of subluxation or positive apprehension. Radiological signs of osteoarthritis were present in 20 shoulders (51%), of which 75% had grade 1 arthropathy according to the Samilson Prieto score. The incidence of osteoarthritis of the operated shoulder was significantly greater compared to the non-operated shoulder. The mean Rowe score was 85 points (25-100) and the Constant score 92 points (70-100). CONCLUSION: We conclude that the open-modified Bankart procedure is a reliable surgical procedure with good long-term results, 16-26 years after surgery. However, it does not prevent the development of shoulder osteoarthritis, since a high number of patients had (mainly mild) radiological osteoarthritis.

Optimizing the dose of local infiltration analgesia and gabapentin for total knee arthroplasty, a randomized single blind trial in 128 patients.

BACKGROUND AND PURPOSE: Effective analgesia is essential for postoperative recovery and rehabilitation in TKA. The challenge of analgesic regimes is to obtain adequate pain relief and maximum muscle control to mobilize and rehabilitate patients early. However, the optimal dose and best composition are not known. We hypothesized that there would be no differences in reported postoperative pain on the day of the TKA surgery as well as the first day after surgery when different combinations of ropivacain for LIA and gabapentin are given. METHODS: This prospective randomized trial examined 128 TKA patients treated with LIA and gabapentin in four groups. Group A: 300-mg ropivacain/600-300-300-mg gabapentin. Group B: 150-mg ropivacain/600-300-300-mg gabapentin. Group C: 300-mg ropivacain/300-100-100-mg gabapentin. Group D: 150-mg ropivacain/300-100-100-mg gabapentin. Primary endpoint was pain (NRS) at multiple moments. Secondary endpoints were number of adverse effects, length of hospital stay (LOS), the amount of consumption of pain medication, and wound leakage. Generalized estimating equation (GEE) was used to detect differences between the four groups regarding the course of pain. RESULTS: No differences regarding adverse effects, LOS, and wound leakage were found. GEE revealed a significant difference in course of pain between group A and B, with group B experiencing higher NRS scores postoperatively than group A (p=0.021). No differences between the other groups were found. INTERPRETATION: The results of the current study suggest that LIA with 300-mg (150ml) ropivacain might be more effective than 150-mg (75ml) ropivacain. Alteration in dose of gabapentin appears not to have influence on the course of pain.

Cost-Utility Analysis of High Molecular Weight Hyaluronic Acid for Knee Osteoarthritis in Everyday Clinical Care in Patients at a Working Age: An Economic Evaluation of a Randomized Clinical Trial.

OBJECTIVE: Knee osteoarthritis (OA) is associated with high medical costs and especially with high productivity costs, in particular in patients in their working years. High molecular weight (HMW) hyaluronic acid (HA) is an alternative treatment for nonsteroidal antiinflammatory drugs, which are known for their serious side-effects. The cost-utility of intraarticular HMW-HA treatment in these patients is unknown, however, and was assessed in this study. METHODS: Secondary care patients ages 18-65 years with knee OA were randomized to usual care plus HMW-HA (intervention group) or to usual care only (control group). A cost-utility analysis over 52 weeks from the societal and health care perspective was performed. Uncertainty for costs, effects, and cost-utility ratio was analyzed by nonparametric bootstrapping. Baseline imbalance adjustment was done by inverse probability of treatment weighting. RESULTS: In total, 156 subjects were included (intervention group n = 77, control group n = 79). The total of productivity and medical costs was €475 higher in the intervention group at €7,754 (95% confidence interval [95% CI] 5,426, 10,436) versus €7,270 (95% CI 5,453, 9,262). The amount of quality-adjusted life years (QALYs) gained during followup was also higher in the intervention group (0.779 versus 0.727). This variation resulted in an incremental cost-effectiveness ratio of €9,100/QALY from a societal perspective and €8,700/QALY from a health care perspective. When the maximum willingness to pay for conditions similar to knee OA is considered, the probability on cost-effectiveness is 64% and 86%, respectively. CONCLUSION: Intraarticular HMW-HA added to usual care for knee OA is probably cost-effective in the treatment of knee OA.

Comparison of Mini-Midvastus and Conventional Total Knee Arthroplasty with Clinical and Radiographic Evaluation: A Prospective Randomized Clinical Trial with 5-Year Follow-up.

BACKGROUND: The main objective of this prospective randomized study was to compare the clinical and radiographic outcomes of the mini-midvastus (MMV) approach with the conventional approach for total knee arthroplasty at the 5-year follow-up. METHODS: Ninety-seven patients (100 knees) with osteoarthritis were assigned to the MMV group or to a group receiving conventional total knee arthroplasty. Intraoperative and postoperative clinical data were collected. At 6 weeks and at 1, 2, and 5 years postoperatively, the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Oxford Knee Score (OKS), the Knee Society Score (KSS), and the Short Form (SF)-12 were completed. Radiographs of the knee were made preoperatively and at 1 day and 1 and 5 years postoperatively. Computed tomography (CT) scans were performed 2 years postoperatively. RESULTS: In the MMV group, the mean skin incision was 2.5 cm shorter (p < 0.001) and the mean duration of the operation was 6 minutes longer than in the conventional total knee arthroplasty group (p < 0.05). Eight patients in the conventional group had a lateral parapatellar retinacular release compared with 1 in the MMV group; the difference was significant (p = 0.01). Three intraoperative complications, including 2 small lateral femoral condylar fractures and 1 partial patellar tendon laceration, occurred in the MMV group. Seven patients in the MMV group had postoperative blisters; all of them had a relatively large femoral component and 4 of them were large men. The radiographs and CT scans of the prostheses showed no significant differences between the MMV and conventional groups except for the posterior slope of the tibial component. In addition, no significance differences were detected between the groups with respect to the KOOS, OKS, KSS, and SF-12 scores determined at the 6-week and the 1, 2, and 5-year follow-up evaluations. CONCLUSIONS: In the rehabilitation period and at the short and mid-term follow-up, no relevant clinical and radiographic differences were found between the MMV and the conventional approach for total knee arthroplasty, making the advantage of MMV total knee arthroplasty cosmetic. We discourage the use of the MMV approach in large male patients because of the increased number of intraoperative complications and skin blisters postoperatively. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Factors influencing length of hospital stay after primary total knee arthroplasty in a fast-track setting.

PURPOSE: The goal of this study was to identify factors prior to surgery that are associated with an increased length of hospital stay after TKA using a fast-track protocol. MATERIALS AND METHODS: In total, 879 consecutive patients who underwent primary TKA were included in this retrospective cohort study. A length of stay greater than or equal to three nights was considered an increased length of hospital stay. Univariable and multivariable generalized linear mixed models were used to identify potential factors associated with increased length of hospital stay. RESULTS: Length of hospital stay was significantly associated with age [OR 1.01 (95 % CI 1.01-1.02); p < 0.001], gender [female vs. male, OR 1.07 (95 % CI 1.00-1.15); p = 0.04], ASA [ASA III/IV vs. ASA I, OR 1.22 (95 % CI 1.06-1.39); p = 0.005], living situation (alone vs. together, OR 1.08 (95 % CI 1.00-1.16); p = 0.04], neurological comorbidities [OR 1.14 (95 % CI 1.06-1.23); p < 0.001], musculoskeletal comorbidities [OR 0.91 (95 % CI 0.85-0.97); p = 0.005], anaesthesia [spinal vs. general, OR 0.86 (95 % CI 0.76-0.97); p = 0.02], and weekday of surgery [Thursday vs. Monday, OR 1.12 (95 % CI 1.02-1.23); p = 0.02]. CONCLUSIONS: Older age, female gender, ASA III/IV, people living alone, the presence of neurological comorbidities, general anaesthesia and surgery on Thursday were associated with an increased length of hospital stay. In clinical practice, the knowledge of factors associated with an increased length of hospital stay can be used to further optimize peri-operative protocols for patients at risk for an increased length of hospital stay after TKA. LEVEL OF EVIDENCE: II.

The first 6 weeks of recovery after total knee arthroplasty with fast track.

BACKGROUND AND PURPOSE: During the last decade, many hospitals have implemented fast-track protocols for total knee arthroplasty (TKA). These protocols reduce the length of hospital stay, but there is no literature on the first period after hospital discharge. We determined how patients experienced the first 6 weeks after hospital discharge after fast-track TKA surgery. PATIENTS AND METHODS: 34 consecutive patients who had TKA surgery with fast track received a diary for 6 weeks, which contained various international validated questionnaires. In addition, general questions regarding pain, the wound, physiotherapy, and thrombosis prophylaxis injections were posed. RESULTS: 4 of the 34 patients were excluded during the study. Of the remaining 30 patients, 28 were positive regarding the short length of hospital stay. Pain gradually decreased and quality of life and function gradually improved during the 6 weeks. Mean hours of weekly physiotherapy were 0.6 for the first week and 0.9 during the sixth week, with high variance of treatment modalities due to the lack of standardized treatment protocols. Additional clinical consultations were needed in 9 patients during the 6-week period. INTERPRETATION: 28 of 30 patients were satisfied with the short length of hospital stay. The intensity of physiotherapy was surprisingly low. The quality of life 6 weeks after discharge was similar to that before the surgery.

Early follow-up after primary total knee and total hip arthroplasty with rapid recovery : Focus groups.

Rapid recovery protocols reduce the length of hospital stay after Total Knee Arthroplasty (TKA) and Total Hip Arthroplasty (THA). However, little is known about the early postoperative phase. The purpose of this study was to examine which problems patients encountered during the first six weeks after primary TKA or THA surgery with rapid recovery. We invited twenty patients for a focus group meeting which discussed various subjects regarding the first six weeks after hospital discharge. The focus group meetings were analysed qualitatively. Patients were mostly satisfied by the short length of hospital stay. Patients who lived alone needs more care and would like to stay longer in the hospital. After THA surgery all patients complained of inability to sleep. More patients experienced pain after TKA surgery compared to THA surgery. All patients had various experiences regarding physical therapy therefore an evidence based rehabilitation protocol might be needed.

Obesity does not influence the outcome after unicompartmental knee arthroplasty.

We retrospectively reviewed all 147 medial UKA's placed between 2001 and 2011 with a minimum follow-up of two years. The VAS for pain and satisfaction, the New Knee Society Score (KSS) for satisfaction and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were used as patient reported outcomes (PROs). Pre-operative and follow-up radiographs of the knee were assessed. The survival rate with a median follow-up of 5.0 years is 87%. No significant difference in survival, PROs or radiographical results were seen between the obese and non-obese group. Mid-term survival, radiographical results and PROs of a UKA are not influenced by obesity. Obesity in patients with medial compartment knee osteoarthritis should not form a contra-indication when selecting patients for a UKA.

Validation of a measuring technique with computed tomography for cement penetration into trabecular bone underneath the tibial tray in total knee arthroplasty on a cadaver model.

BACKGROUND: In total knee arthroplasty (TKA), cement penetration between 3 and 5 mm beneath the tibial tray is required to prevent loosening of the tibia component. The objective of this study was to develop and validate a reliable in vivo measuring technique using CT imaging to assess cement distribution and penetration depth in the total area underneath a tibia prosthesis. METHODS: We defined the radiodensity ranges for trabecular tibia bone, polymethylmethacrylate (PMMA) cement and cement-penetrated trabecular bone and measured the percentages of cement penetration at various depths after cementing two tibia prostheses onto redundant femoral heads. One prosthesis was subsequently removed to examine the influence of the metal tibia prostheses on the quality of the CT images. The percentages of cement penetration in the CT slices were compared with percentages measured with photographs of the corresponding transversal slices. RESULTS: Trabecular bone and cement-penetrated trabecular bone had no overlap in quantitative scale of radio-density. There was no significant difference in mean HU values when measuring with or without the tibia prosthesis. The percentages of measured cement-penetrated trabecular bone in the CT slices of the specimen were within the range of percentages that could be expected based on the measurements with the photographs (p = 0.04). CONCLUSIONS: CT scan images provide valid results in measuring the penetration and distribution of cement into trabecular bone underneath the tibia component of a TKA. Since the proposed method does not turn metal elements into artefacts, it enables clinicians to assess the width and density of the cement mantle in vivo and to compare the results of different cementing methods in TKA.

[A young, obese woman with a painful knee]. / Een jonge, obese vrouw met een pijnlijke knie.

A 23-year-old morbidly obese woman (BMI: 62,5 kg/m2) came to the ER because of a painful right knee. When walking the knee had collapsed spontaneously. Physical examination of the right leg was not possible due to pain. Examination of the unaffected left leg revealed multi-directional instability. A radiograph showed anterior luxation of the tibia.