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.

Long-term postoperative opioid use in orthopaedic patients.

BACKGROUND: The prevalence of long-term opioid use after orthopaedic surgery varies from 1.4% to 24% and has mostly been studied with prescription data, making it difficult to estimate the size and impact of the problem. This study aims to assess the prevalence and predictors of long-term postoperative opioid use in a high volume and tertiary orthopaedic centre by using online patient reported measures. METHODS: This Dutch prospective cohort study was conducted among adult patients who underwent any type of orthopaedic surgery from June to August 2021. Six months after surgery patients were invited to complete an online survey on current opioid use and patients' willingness to taper opioids. The demographics, clinical factors and preoperative opioid use were extracted from the patient file. RESULTS: In total, 607 patients (mean age 61.2 years, 63.4% female) completed the survey. Seventy-six patients (12.5%) used opioids 6 months after surgery of which 20 (3.3%) did not use opioids before surgery. The median (Q1-Q3) postoperative daily dose after 6 months was 29.9 mg (10.0-76.1) morphine equivalents. Most of them (88.2%) wanted to taper opioids. Affected body region (OR's: 6.84-12.75) and pre-operative opioid use (OR = 35.33) were significant predictors of long-term opioid use. CONCLUSION: The prevalence of long-term postoperative opioid use was 12.5%; one in thirty patients became a new long-term opioid user. Pre-operative opioid use and affected body region were predictive for long-term opioid use. These findings, together with the observation that long-term opioid users want to taper opioids, emphasize the relevance of prevention, recognition and tapering support in the perioperative setting. LEVEL OF EVIDENCE: Level II. SIGNIFICANCE: Short-term opioid use can unintentionally progress to long-term opioid use. The prevalence of long-term opioid use after orthopaedic surgery varies widely and is mostly prescription-based, making it difficult to estimate the magnitude of the problem. This study assessed long-term postoperative opioid use in a full breadth orthopaedic population using patient reported measures, making conclusions much more robust. The prevalence of long-term postoperative opioid use in this study was 12.5%.

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.

A mapping review on preoperative prognostic factors and outcome measures of revision total knee arthroplasty.

To map literature on prognostic factors related to outcomes of revision total knee arthroplasty (rTKA), to identify extensively studied factors and to guide future research into what domains need further exploration. We performed a systematic literature search in MEDLINE, Embase, and Web of Science. The search string included multiple synonyms of the following keywords: "revision TKA", "outcome" and "prognostic factor". We searched for studies assessing the association between at least one prognostic factor and at least one outcome measure after rTKA surgery. Data on sample size, study design, prognostic factors, outcomes, and the direction of the association was extracted and included in an evidence map. After screening of 5,660 articles, we included 166 studies reporting prognostic factors for outcomes after rTKA, with a median sample size of 319 patients (30 to 303,867). Overall, 50% of the studies reported prospectively collected data, and 61% of the studies were performed in a single centre. In some studies, multiple associations were reported; 180 different prognostic factors were reported in these studies. The three most frequently studied prognostic factors were reason for revision (213 times), sex (125 times), and BMI (117 times). Studies focusing on functional scores and patient-reported outcome measures as prognostic factor for the outcome after surgery were limited (n = 42). The studies reported 154 different outcomes. The most commonly reported outcomes after rTKA were: re-revision (155 times), readmission (88 times), and reinfection (85 times). Only five studies included costs as outcome. Outcomes and prognostic factors that are routinely registered as part of clinical practice (e.g. BMI, sex, complications) or in (inter)national registries are studied frequently. Studies on prognostic factors, such as functional and sociodemographic status, and outcomes as healthcare costs, cognitive and mental function, and psychosocial impact are scarce, while they have been shown to be important for patients with osteoarthritis.

Objective monitoring of functional recovery after total knee and hip arthroplasty using sensor-derived gait measures.

Background: Inertial sensors hold the promise to objectively measure functional recovery after total knee (TKA) and hip arthroplasty (THA), but their value in addition to patient-reported outcome measures (PROMs) has yet to be demonstrated. This study investigated recovery of gait after TKA and THA using inertial sensors, and compared results to recovery of self-reported scores of pain and function. Methods: PROMs and gait parameters were assessed before and at two and fifteen months after TKA (n = 24) and THA (n = 24). Gait parameters were compared with healthy individuals (n = 27) of similar age. Gait data were collected using inertial sensors on the feet, lower back, and trunk. Participants walked for two minutes back and forth over a 6m walkway with 180° turns. PROMs were obtained using the Knee Injury and Osteoarthritis Outcome Scores and Hip Disability and Osteoarthritis Outcome Score. Results: Gait parameters recovered to the level of healthy controls after both TKA and THA. Early improvements were found in gait-related trunk kinematics, while spatiotemporal gait parameters mainly improved between two and fifteen months after TKA and THA. Compared to the large and early improvements found in of PROMs, these gait parameters showed a different trajectory, with a marked discordance between the outcome of both methods at two months post-operatively. Conclusion: Sensor-derived gait parameters were responsive to TKA and THA, showing different recovery trajectories for spatiotemporal gait parameters and gait-related trunk kinematics. Fifteen months after TKA and THA, there were no remaining gait differences with respect to healthy controls. Given the discordance in recovery trajectories between gait parameters and PROMs, sensor-derived gait parameters seem to carry relevant information for evaluation of physical function that is not captured by self-reported scores.

Reasons for revision are associated with rerevised total knee arthroplasties: an analysis of 8,978 index revisions in the Dutch Arthroplasty Register.

Background and purpose - From previous studies, we know that clinical outcomes of revision total knee arthroplasty (rTKA) differ among reasons for revision. Whether the prevalence of repeat rTKAs is different depending on the reason for index rTKA is unclear. Therefore, we (1) compared the repeat revision rates between the different reasons for index rTKA, and (2) evaluated whether the reason for repeat rTKA was the same as the reason for the index revision.Patients and methods - Patients (n = 8,978) who underwent an index rTKA between 2010 and 2018 as registered in the Dutch Arthroplasty Register were included. Reasons for revision, as reported by the surgeon, were categorized as: infection, loosening, malposition, instability, stiffness, patellar problems, and other. Competing risk analyses were performed to determine the cumulative repeat revision rates after an index rTKA for each reason for revision.Results - Overall, the cumulative repeat revision rate was 19% within 8 years after index rTKA. Patients revised for infection had the highest cumulative repeat revision rate (28%, 95% CI 25-32) within 8 years after index rTKA. The recurrence of the reason was more common than other reasons after index rTKA for infection (18%), instability (8%), stiffness (7%), and loosening (5%).Interpretation - Poorest outcomes were found for rTKA for infection: over 1 out of 4 infection rTKAs required another surgical intervention, mostly due to infection. Recurrence of other reasons for revision (instability, stiffness, and loosening) was also considerable. Our findings also emphasize the importance of a clear diagnosis before doing rTKA to avert second revision surgeries.

Independent and sensitive gait parameters for objective evaluation in knee and hip osteoarthritis using wearable sensors.

BACKGROUND: Although it is well-established that osteoarthritis (OA) impairs daily-life gait, objective gait assessments are not part of routine clinical evaluation. Wearable inertial sensors provide an easily accessible and fast way to routinely evaluate gait quality in clinical settings. However, during these assessments, more complex and meaningful aspects of daily-life gait, including turning, dual-task performance, and upper body motion, are often overlooked. The aim of this study was therefore to investigate turning, dual-task performance, and upper body motion in individuals with knee or hip OA in addition to more commonly assessed spatiotemporal gait parameters using wearable sensors. METHODS: Gait was compared between individuals with unilateral knee (n = 25) or hip OA (n = 26) scheduled for joint replacement, and healthy controls (n = 27). For 2 min, participants walked back and forth along a 6-m trajectory making 180° turns, with and without a secondary cognitive task. Gait parameters were collected using 4 inertial measurement units on the feet and trunk. To test if dual-task gait, turning, and upper body motion had added value above spatiotemporal parameters, a factor analysis was conducted. Effect sizes were computed as standardized mean difference between OA groups and healthy controls to identify parameters from these gait domains that were sensitive to knee or hip OA. RESULTS: Four independent domains of gait were obtained: speed-spatial, speed-temporal, dual-task cost, and upper body motion. Turning parameters constituted a gait domain together with cadence. From the domains that were obtained, stride length (speed-spatial) and cadence (speed-temporal) had the strongest effect sizes for both knee and hip OA. Upper body motion (lumbar sagittal range of motion), showed a strong effect size when comparing hip OA with healthy controls. Parameters reflecting dual-task cost were not sensitive to knee or hip OA. CONCLUSIONS: Besides more commonly reported spatiotemporal parameters, only upper body motion provided non-redundant and sensitive parameters representing gait adaptations in individuals with hip OA. Turning parameters were sensitive to knee and hip OA, but were not independent from speed-related gait parameters. Dual-task parameters had limited additional value for evaluating gait in knee and hip OA, although dual-task cost constituted a separate gait domain. Future steps should include testing responsiveness of these gait domains to interventions aiming to improve mobility.

Definitions of poor outcome after total knee arthroplasty: an inventory review.

BACKGROUND: A significant proportion of patients experiences poor response (i.e. no or little improvement) after total knee arthroplasty (TKA) because of osteoarthritis. It is difficult to quantify the proportion of patients who experiences poor response to TKA, as different definitions of, and perspectives (clinician's and patient's) on poor response are being used. The aim of this study was therefore to review the literature and summarize definitions of poor response to TKA. METHODS: A systematic search was performed to identify and review studies that included dichotomous definitions of poor outcome after primary TKA. The type, amount and combination of domains (e.g. functioning), outcome measures, type of thresholds (absolute/relative, change/cut-off), values and moments of follow-up used in definitions were summarized. RESULTS: A total of 47 different dichotomous definitions of poor response to TKA were extracted from 2163 initially identified studies. Thirty-six definitions incorporated one domain, seven definitions comprised two domains and four definitions comprised three domains. Eight different domains were used in identified definitions: pain, function, physical functioning, quality of life (QoL), patient satisfaction, anxiety, depression and patient global assessment. The absolute cut-off value was the most common type of threshold, with large variety in value and timing of follow-up. CONCLUSIONS: Our inventory review shows that definitions of poor response to TKA are heterogeneous. Our findings stresses the need for an unambiguous definition of poor response to draw conclusions about the prevalence of poor-responders to TKA across hospitals and countries, and to identify patients at risk.

Changes in periacetabular bone mineral density five years after resurfacing hip arthroplasty versus conventional total hip arthroplasty.

INTRODUCTION:: We studied whether acetabular bone mineral density (BMD) is better preserved after resurfacing hip arthroplasty (RHA) versus small diameter metal-on-metal total hip arthroplasty (THA). METHODS:: This randomised controlled trial included 82 patients. BMD was measured in 5 periprosthetic regions of interest (ROI) with dual-energy absorptiometry (DEXA) preoperatively, at 3 and 6 months, 1, 2, 3 and 5 years postoperative. 34 RHA and 26 THA had a complete 5 years follow-up. 1 RHA and 1 THA were revised due to pseudotumour formation, 2 THA were revised because of recurrent dislocations and 1 RHA for avascular necrosis. RESULTS:: Overall an initial decrease in BMD was observed for both implants, stabilising after 2 years. 5 years after RHA a BMD change of +1% in upper cranial, -4% ( p < 0.01) in cranial, -8% ( p < 0.01) in craniomedial, -7% ( p < 0.01) in medial and +4% in caudal ROI compared to baseline values was seen. 5 years after THA a BMD change of -3% ( p = 0.01), -13% ( p < 0.01), -21% ( p < 0.01), -11% ( p < 0.01) and -2% for each respective ROI. The observed BMD decrease in different regions was structurally favouring the RHA-cup, with significantly higher levels in the cranial and craniomedial ROI. CONCLUSION:: Acetabular BMD is better preserved behind a rigid press-fit convex cup in RHA compared to a titanium threaded cup in conventional THA in the cranial and craniomedial ROI. Despite of a theoretical higher stress-shielding behind the stiff acetabular component in RHA, compared to the more elastic threaded titanium THA-cup, bone depletion behind the RHA component does not seem to be of major concern. REGISTRATION:: EudraCT (2006-005610-12).

Higher patient activity level and subchondral stiffening in asymptomatic cam femoroacetabular impingement subjects.

A cam deformity is proposed as a cause of idiopathic osteoarthritis. Increased subchondral bone mineral density (BMD) is associated with this degenerative process of osteoarthritis, and the patient's activity level may contribute to it. Therefore, the correlation between activity level and subchondral BMD in subjects with cam deformity FAI was studied. In this study, 26 asymptomatic cam deformity subjects (Bump) were compared with 18 subjects with a normal alpha angle (Control). Anterosuperior subchondral femoral neck and acetabular rim BMD were measured using quantitative computed tomography. Activity level was determined using the UCLA activity score. The correlation between BMD and UCLA activity were analysed. The result was a significantly higher BMD for Bump subjects in almost all measured sections. The UCLA score of the Bump versus Control subjects were comparable (8.96 versus 8.77, P = 0.740). While the controls showed no correlation between UCLA and BMD, a positive correlation was found for the Bump subjects on several femoral and acetabular impingement locations. These results support the conclusion that mechanical loading causes subchondral stiffening at the anterosuperior head-neck junction of the femur and anterosuperior acetabular rim. The absence of a correlation between BMD versus UCLA in the Controls supports the hypothesis that activity level may serve as a predictor for higher subchondral BMD in a cam deformity hip joint.

Changes in bone mineral density and femoral neck narrowing in the proximal femur three to five years after hip resurfacing versus conventional total hip arthroplasty.

We studied whether bone mineral density (BMD) is preserved without significant femoral neck narrowing (FNN) after hip resurfacing (RHA) (n=42) versus small diameter metal-on-metal total hip arthroplasty (MoM THA) (n=40). In this three to five year randomized trial BMD was measured in the calcar with dual energy absorptiometry (DXA) preoperatively, at three and six months, one, two, three and five years postoperatively. Four additional BMD regions of interest (ROIs) and femoral neck narrowing (FNN) were measured after RHA. BMD in the calcar increased to 107% (P<0.001) at one year and remained stable. Additional ROIs in the femoral neck and trochanter-area BMD changes fluctuated between 99.9% and 104.1%. FNN was minimal with a mean of 1.3% at three years. After THA BMD decreased in the calcar to 80% at one year (P<0.001) and stabilized. This bone stock preserving nature of RHA must be weighed against potential disadvantages caused by specific metal-on-metal bearing problems.

Metal ion levels and functional results following resurfacing hip arthroplasty versus conventional small-diameter metal-on-metal total hip arthroplasty; a 3 to 5year follow-up of a randomized controlled trial.

We present an update of a randomized controlled trial on 71 patients (<65 years) who received either a resurfacing hip arthroplasty (RHA) (n=38) or cementless 28-mm metal-on-metal (MoM) total hip arthroplasty (THA) (n=33). Metal ion levels and functional outcome scores were analyzed with a mean follow-up of 58 months (SD 8.1). No clear shifts in relatively good outcome was encountered between RHA and THA. Metal ion levels appear to equalize between groups after 3 years. Median cobalt and chromium remained below 1.3 µg/L throughout follow-up in both groups. Six revisions were performed, of which three for pseudotumor formation (one THA, two RHA). In conclusion there were no clinical differences between the two groups and metal ion levels were lower than other series remained low, however, pseudotumor formation was not eliminated.

Metal ion trend may be more predictive for malfunctioning metal-on-metal implants than a single measurement.

Forty-eight unilateral hip resurfacing arthroplasty patients were evaluated for cobalt and chromium levels. The metal ion trend of 42 well-functioning patients was compared with six sub-optimal functioning patients. Median metal ion levels were significantly higher for the sub-optimal group. For the well-functioning implants, the percentage of patients with increasing cobalt/chromium levels between two consecutive time-intervals ('risers') gradually decreased from 90/86% (0-3 months) to 22/22% (24-36 months). The percentage of patients with increasing metal ion levels was higher in the sub-optimal group. The median absolute increase of this 'risers' subgroup was significantly lower for the well-functioning group at 12-24 months. Sub-optimal functioning MoM implants have a different metal ion trend than well-functioning implants, a higher chance of 'risers' and a larger absolute increase in time.

High incidence of pseudotumours after hip resurfacing even in low risk patients; results from an intensified MRI screening protocol.

We intensified our screening protocol for the presence of pseudotumours in a consecutive series of patients with a hip resurfacing arthroplasty (HRA), to establish whether we should be alert to the presence of 'silent' pseudotumours. Patients categorised with high risk (11 hips) and low risk (10 hips) for pseudotumour development and a control group (23 hips) were screened with metal artefact reduction sequence (MARS) magnetic resonance imaging (MRI). The Anderson classification to grade any metal-on-metal (MoM) disease present on MARS-MRI images was used. In 15 out of 44 MRI scans pseudotumours were observed (34.1%), of which six were graded with mild (13.6%), eight with moderate (18.2%) and one with severe MoM disease (2.3%). Twelve pseudotumours were present in asymptomatic patients (27.3%). Metal ion levels were normal in 80% of the MARS-MRI screened patients. As a consequence of our intensified screening protocol, one patient was revised for pseudotumour formation and another patient was scheduled for revision. Silent pseudotumours were observed in all three groups. Before our intensified screening protocol was initiated, no pseudotumours were encountered in our cohort of 289 HRAs. We concluded that clinical outcomes and plain radiographs for screening MoM patients underestimates the presence of pseudotumours in MoM patients. The true clinical relevance of these pseudotumours is still unclear.

Periacetabular bone mineral density changes after resurfacing hip arthroplasty versus conventional total hip arthroplasty. A randomized controlled DEXA study.

A randomized controlled trial was performed to evaluate acetabular bone mineral density (BMD) changes after hip resurfacing (RHA) versus an established conventional total hip arthroplasty (THA). A total of 71 patients were allocated randomly to receive either an RHA press-fit cobalt-chromium cup (n=38) or a THA with a threaded titanium cup and polyethylene-metal-inlay insert (n=33). The BMD in five separate periacetabular regions of interest (ROI) was prospectively quantified preoperative until 24 months. We conclude that, in contrast to our hypothesis, periacetabular BMD was better preserved after RHA than after placement of a conventional THA. Long term follow-up studies are necessary to see whether this benefit in bone preservation sustains over longer time periods and whether it is turned into clinical benefits at future revision surgery.

Metal ion levels and functional results after either resurfacing hip arthroplasty or conventional metal-on-metal hip arthroplasty.

BACKGROUND: Modern metal-on-metal hip resurfacing was introduced as a bone-preserving method of joint reconstruction for young and active patients; however, the large diameter of the bearing surfaces is of concern for potentially increased metal ion release. PATIENTS AND METHODS: 71 patients (< 65 years old) were randomly assigned to receive either a resurfacing (R) hip arthroplasty (n = 38) or a conventional metal-on-metal (C) hip arthroplasty (n = 33). Functional outcomes were assessed preoperatively and at 6, 12, and 24 months. Cobalt and chromium blood levels were analyzed preoperatively and at 3, 6, 12, and 24 months. RESULTS: All functional outcome scores improved for both groups. At 12 and 24 months, the median UCLA activity score was 8 in the R patients and 7 in the C patients (p < 0.05). At 24 months, OHS was median 16 in C patients and 13 in R patients (p < 0.05). However, in spite of randomization, UCLA scores also appeared to be higher in R patients at baseline. Satisfaction was similar in both groups at 24 months. Cobalt concentrations were statistically significantly higher for R patients only at 3 and 6 months. Chromium levels remained significantly higher for R patients until 24 months. No pseudotumors were encountered in either group. One R patient was revised for early aseptic loosening and in 2 C patients a cup insert was exchanged for recurrent dislocation. INTERPRETATION: R patients scored higher on UCLA, OHS, and satisfaction at some time points; however, as for the UCLA, preoperative levels were already in favor of R. The differences, although statistically significant, were of minor clinical importance. Chromium blood levels were statistically significantly higher for R patients at all follow-up measurements, whereas for cobalt this was only observed up to 6 months. The true value of resurfacing hip arthroplasty over conventional metal-on-metal hip arthroplasty will be determined by longer follow-up and a possible shift of balance between their respective (dis)advantages.

Metal ion interpretation in resurfacing versus conventional hip arthroplasty and in whole blood versus serum. How should we interpret metal ion data.

Metal ions generated from joint replacements are a cause for concern. There is no consensus on the best surrogate measure of metal ion exposure, and both serum and whole blood measurements are used in clinical practice. This study provides a guideline for interpretation of metal ion analysis in clinical practice. In a prospective trial comparing hip resurfacing (HR) with a conventional metal-on-metal (MoM) total hip arthroplasty (THA) cobalt and chromium levels were determined for whole blood and serum in 343 paired samples at regular intervals up to 24 months postoperatively. Cobalt whole blood and serum levels increased significantly after both procedures. Cobalt concentrations were significantly higher for the HR group compared to the THA group, at 3, 6 and 12 months, for whole blood and serum. At 24 months cobalt levels decreased and differences between HR and THA were no longer significant. In contrast, chromium whole blood levels remained significantly higher for HR until 24 months. Whole blood and serum levels could not be used interchangeably. The mean differences for cobalt and chromium between blood and serum values were +0.13 µg/L and -0.91 µg/L respectively. Regression analysis provided a formula for conversion from serum to blood of 0.34+[0.88*Co serum] for cobalt and 0.14 + [0.58*Cr serum] for chromium, with an acceptable prediction error below ±1.0 µg/L. Cobalt and chromium levels were significantly higher for HR versus THA, especially during the run-in phase of one year. Overall, the metal ion levels were well below 5 µg/L. We cannot recommend the use of whole blood over serum measurements or vice versa. The provided conversion formula between whole blood and serum in combination with the presented practical guidelines may be useful for clinical practice.

No clear influence of preference bias on satisfaction and early functional outcome in resurfacing hip arthroplasty.

BACKGROUND AND PURPOSE: Hip resurfacing arthroplasty (RHA) is done in patients who often have a high preference for the method. This preference can influence the clinical outcome and satisfaction. We evaluated the potential influence of this preference bias. PATIENTS AND METHODS: From an ongoing randomized trial comparing RHA with total hip arthroplasty, 28 consecutive patients (28 hips) who had been allocated to an RHA were characterized as the "randomized" group. 22 other patients (24 hips) who had refused participation and had especially requested an RHA were characterized as the "preference" group. Harris hip score (HHS), Oxford hip score (OHS), University of California at Los Angeles activity scale (UCLA), Short Form 12 (SF-12), and visual analog scale satisfaction score (VAS) were assessed in both groups. RESULTS: Both groups had a high implant satisfaction score (97/100 for the "preference" group and 93/100 for the "randomized" group) at 12 months. The HHS, OHS, and UCLA were similar at baseline and also revealed a similar improvement up to 12 months (p < 0.001). Regarding the SF-12, the "preference" group scored lower on the mental subscale preoperatively (p = 0.03), and there was a greater increase after 12 months (p = 0.03). INTERPRETATION: We could not show that there was any influence of preference on satisfaction with the implant and early clinical outcome in patients who underwent RHA. The difference in mental subscale scores between groups may still indicate a difference in psychological profile.

Osteochondral autograft transplantation for osteochondritis dissecans of the knee. Preliminary results of a prospective case series.

To evaluate the short-term outcome of osteochondritis dissecans (OCD) treated with mosaic osteochondral autograft transplantation (OAT), 7 male patients (mean age 33.4) with 8 OCD lesions on the lateral border of the medial femoral condyle were prospectively followed. Patients were evaluated by the International Knee Documention Committee (IKDC) score and the Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaires preoperatively, at 6 months and 1 year after surgery. MRI evaluation using the modified Sanders score was performed at 1-year follow-up. The IKDC subjective score and all subscales of the KOOS improved significantly. MRI evaluation showed good surface congruency, no oedema or protuberance of the osteocartilaginous cylinders, good similarity of cartilage thickness and a non-complete osseous integration. With the small numbers of patients available, no correlation could be found between MRI findings, percentage of defect coverage and patient satisfaction. Mosaic OAT appeared in this study as a valid treatment option in selected cartilage defects. OCD lesions improved significantly following osteochondral transplantation. The limitations of this technique are the number and size of the plugs needed to repair the defect. Future research should focus on identifying the appropriate choice of operative treatment for well defined subtypes of articular cartilage lesions, rather than searching for one superior technique for all.