Aims. Unicompartmental knee arthroplasty (UKA) has higher revision rates than total knee arthroplasty (TKA). As revision of UKA may be less technically demanding than revision TKA, UKA patients with poor functional outcomes may be more likely to be offered revision than TKA patients with similar outcomes. The aim of this study was to compare clinical thresholds for revisions between TKA and UKA using revision incidence and patient-reported outcomes, in a large, matched cohort at early, mid-, and late-term follow-up. Methods. Analyses were performed on propensity score-matched patient cohorts of TKAs and UKAs (2:1) registered in the New Zealand Joint Registry between 1 January 1999 and 31 December 2019 with an Oxford Knee Score (OKS) response at six months (n, TKA: 16,774; UKA: 8,387), five years (TKA: 6,718; UKA: 3,359), or ten years (TKA: 3,486; UKA: 1,743). Associations between OKS and revision within two years following the score were examined. Thresholds were compared using receiver operating characteristic analysis. Reasons for aseptic revision were compared using cumulative incidence with competing risk. Results. Fewer TKA patients with ‘poor’ outcomes (≤ 25) subsequently underwent revision compared with UKA at six months (5.1% vs 19.6%; p < 0.001), five years (4.3% vs 12.5%; p < 0.001), and ten years (6.4% vs 15.0%; p = 0.024). Compared with TKA, the relative risk for UKA was 2.5-times higher for ‘unknown’ reasons, bearing dislocations, and disease progression. Conclusion. Compared with TKA, more UKA patients with poor outcomes underwent revision from early to long-term follow-up, and were more likely to undergo revision for ‘unknown’ reasons, which suggest a lower clinical threshold for UKA. For UKA, revision risk was higher for bearing dislocations and disease progression. There is supporting evidence that the higher revision UKA rates are associated with lower clinical thresholds for revision and additional modes of failure. Cite this article: Bone Joint J 2023;105-B(3):269–276

Aims. The aim of this study was to identify the origin and development of the threshold for surgical intervention, highlight the consequences of residual displacement, and justify the importance of accurate measurement. Methods. A systematic review of three databases was performed to establish the origin and adaptations of the threshold, with papers screened and relevant citations reviewed. This search identified papers investigating functional outcome, including presence of arthritis, following injury. Orthopaedic textbooks were reviewed to ensure no earlier mention of the threshold was present. Results. Knirk and Jupiter (1986) were the first to quantify a threshold, with all their patients developing arthritis with > 2 mm displacement. Some papers have discussed using 1 mm, although 2 mm is most widely reported. Current guidance from the British Society for Surgery of the Hand and a Delphi panel support 2 mm as an appropriate value. Although this paper is still widely cited, the authors published a re-examination of the data showing methodological flaws which is not as widely reported. They claim their conclusions are still relevant today; however, radiological arthritis does not correlate with the clinical presentation. Function following injury has been shown to be equivalent to an uninjured population, with arthritis progressing slowly or not at all. Joint space narrowing has also been shown to often be benign. Conclusion. Knirk and Jupiter originated the threshold value of 2 mm. The lack of correlation between the radiological and clinical presentations warrants further modern investigation. Measurement often varies between observers, calling a threshold concept into question and showing the need for further development in this area. The principle of treatment remains restoration of normal anatomical position. Cite this article: Bone Joint J 2021;103-B(9):1457–1461

Aims. Mechanical impingement of the iliopsoas (IP) tendon accounts for 2% to 6% of persistent postoperative pain after total hip arthroplasty (THA). The most common initiator is anterior acetabular component protrusion, where the anterior margin is not covered by anterior acetabular wall. A CT scan can be used to identify and measure this overhang; however, no threshold exists for determining symptomatic anterior IP impingement due to overhang. A case-control study was conducted in which CT scan measurements were used to define a threshold that differentiates patients with IP impingement from asymptomatic patients after THA. Methods. We analyzed the CT scans of 622 patients (758 THAs) between May 2011 and May 2020. From this population, we identified 136 patients with symptoms suggestive of IP impingement. Among them, six were subsequently excluded: three because the diagnosis was refuted intraoperatively, and three because they had another obvious cause of impingement, leaving 130 hips (130 patients) in the study (impingement) group. They were matched to a control group of 138 asymptomatic hips (138 patients) after THA. The anterior acetabular component overhang was measured on an axial CT slice based on anatomical landmarks (orthogonal to the pelvic axis). Results. The impingement group had a median overhang of 8 mm (interquartile range (IQR) 5 to 11) versus 0 mm (IQR 0 to 4) for the control group (p < 0.001). Using receiver operating characteristic curves, an overhang threshold of 4 mm was best correlated with a diagnosis of impingement (sensitivity 79%, specificity 85%; positive predictive value 75%, negative predictive value 85%). Conclusion. Pain after THA related to IP impingement can be reasonably linked to acetabular overhang if it exceeds 4 mm on a CT scan. Below this threshold, it seems logical to look for another cause of IP irritation or another reason for the pain after THA before concluding that impingement is present. Cite this article: Bone Joint J 2024;106-B(3 Supple A):97–103

Aims. The aim of this study was to assess medium-term improvements following total hip arthroplasty (THA), and to evaluate what effect different preoperative Oxford Hip Score (OHS) thresholds for treatment may have on patients’ access to THA and outcomes. Methods. Patients undergoing primary THA at our institution with an OHS both preoperatively and at least four years postoperatively were included. Rationing thresholds were explored to identify possible deprivation of OHS improvement. Results. Overall, 2,341 patients were included. Mean OHS was 19.7 (SD 8.2) preoperatively and 39.7 (SD 9.8) at latest follow-up. An improvement of at least eight-points, the minimally important change (MIC), was seen in 2,072 patients (88.5%). The mean improvement was 20.0 points (SD 10.5). If a rationing threshold of OHS of 20 points had been enforced, 90.8% of those treated would have achieved the MIC, but only 54.3% of our cohort would have had access to surgery; increasing this threshold to 32 would have enabled 89.5% of those treated to achieve the MIC while only depriving 6.5% of our cohort. The ‘rationed’ group of OHS > 20 had significantly better OHS at latest follow-up (42.6 vs 37.3; p < 0.001), while extending the rationing threshold above 32 showed postoperative scores were more significantly affected by the ceiling effect of the OHS. Conclusion. The OHS was not designed as a tool to ration healthcare, but if it had been used at our institution for this cohort, applying an OHS threshold of 20 to routine THA access would have excluded nearly half of patients from having a THA; a group in which over 85% had a significant improvement in OHS. Where its use for rationing is deemed necessary, use of a higher threshold may be more appropriate to ensure a better balance between patient access to treatment and chances of achieving good to excellent outcomes. Cite this article: Bone Jt Open 2022;3(3):196–204

Aims. The aim of this study was to identify the minimal clinically important difference (MCID), minimal important change (MIC), minimal detectable change (MDC), and patient-acceptable symptom state (PASS) in the Forgotten Joint Score (FJS) according to patient satisfaction six months following total hip arthroplasty (THA) in a UK population. Methods. During a one-year period, 461 patients underwent a primary THA and completed preoperative and six-month FJS, with a mean age of 67.2 years (22 to 93). At six months, patient satisfaction was recorded as very satisfied, satisfied, neutral, dissatisfied, or very dissatisfied. The difference between patients recording neutral (n = 31) and satisfied (n = 101) was used to define the MCID. MIC for a cohort was defined as the change in the FJS for those patients declaring their outcome as satisfied, whereas receiver operating characteristic curve analysis was used to determine the MIC for an individual and the PASS. Distribution-based methodology was used to calculate the MDC. Results. Using satisfaction as the anchor, the MCID for the FJS was 8.1 (95% confidence interval (CI) 3.7 to 15.9; p = 0.040), which was affirmed when adjusting for confounding. The MIC for the FJS for a cohort of patients was 17.7 (95% CI 13.7 to 21.7) and for an individual patient was 18. The MDC90 for the FJS was eight, meaning that 90% of patients scoring more than this will have experienced a real change that is beyond measurement error. The PASS threshold for the FJS was defined as 29. Conclusion. The MCID and MIC can be used respectively to assess whether there is a clinical difference between two groups, or whether a cohort or patient has had a meaningful change in their FJS. Both values were greater than measurement error (MDC90), suggesting a real change. The PASS threshold for the postoperative FJS can be used as a marker of achieving patient satisfaction following THA. Cite this article: Bone Joint J 2021;103-B(12):1759–1765

Mechanical irritation or impingement of the iliopsoas tendon accounts for 2–6% of persistent postoperative pain cases after total hip arthroplasty (THA). The most common trigger is anterior cup overhang. CT-scan can be used to identify and measure this overhang; however, no threshold exists for symptomatic anterior iliopsoas impingement. We conducted a case–control study in which CT-scan was used to define a threshold that differentiates patients with iliopsoas impingement from asymptomatic patients after THA. We analyzed the CT-scans of 622 patients (758 CT-scans) between 2011 and 2020. Out of this population we identified 136 patients with symptoms suggestive of iliopsoas impingement. Among them, 6 were subsequently excluded: three because the diagnosis was reestablished intra-operatively (one metallosis, two anterior instability related to posterior prosthetic impingement) and three because they had another obvious cause of impingement (one protruding screw, one protruding cement plug, one stem collar), leaving 130 patients in the study (impingement) group. They were matched to a control group of 138 patients who were asymptomatic after THA. The anterior cup overhang (anterior margin of cup not covered by anterior wall) was measured by an observer (without knowledge of the clinical status) on an axial CT slice based on anatomical landmarks (orthogonal to pelvic axis). The impingement group had a median overhang of 8 mm [IQR: 5 to 11] versus 0 mm [IQR: 0 to 4] for the control group (p<.001). Using ROC curves, an overhang threshold of 4 mm was best correlated with a diagnosis of impingement (sensitivity 79%, specificity 85%, PPV = 75%, NPV = 85%). Pain after THA related to iliopsoas impingement can be reasonably linked to acetabular overhang if it exceeds 4 mm on a CT scan. Below this threshold, it seems logical to look for another cause of iliopsoas irritation or another reason for the pain after THA before concluding impingement is present

Aims. It has been hypothesized that a unicompartmental knee arthroplasty (UKA) is more likely to be revised than a total knee arthroplasty (TKA) because conversion surgery to a primary TKA is a less complicated procedure. The purpose of this study was to determine if there is a lower threshold for revising a UKA compared with TKA based on Oxford Knee Scores (OKSs) and range of movement (ROM) at the time of revision. Methods. We retrospectively reviewed 619 aseptic revision cases performed between December 1998 and October 2018. This included 138 UKAs that underwent conversion to TKA and 481 initial TKA revisions. Age, body mass index (BMI), time in situ, OKS, and ROM were available for all patients. Results. There were no differences between the two groups based on demographics or time to revision. The top reasons for aseptic TKA revision were loosening in 212 (44%), instability in 88 (18%), and wear in 69 (14%). UKA revision diagnoses were primarily for loosening in 50 (36%), progression of osteoarthritis (OA) in 50 (36%), and wear in 17 (12%). Out of a maximum 48 points, the mean OKS of the UKAs before revision was 23 (SD 9.3), which was significantly higher than the TKAs at 19.2 (SD 9.8; p < 0.001). UKA patients scored statistically better on nine of the 12 individual OKS questions. The UKA cases also had a larger pre-revision mean ROM (114°, SD 14.3°) than TKAs (98°, SD 25°) ; p < 0.001). Conclusion. At revision, the mean UKA OKSs and ROM were significantly better than those of TKA cases. This study suggests that at our institution there is a difference in preoperative OKS between UKA and TKA at the time of revision, demonstrating a revision bias. Cite this article: Bone Joint J 2020;102-B(6 Supple A):91–95

Aims. We hypothesised that the synovial white blood cell (WBC) count in patients with a late periprosthetic joint infection (PJI) of the hip would depend on the duration of a patient’s symptoms, and that the optimal diagnostic threshold would also depend on this period of time. Patients and Methods. The synovial WBC count and percentage of polymorphonuclear cells (%PMN), and the serum CRP and ESR levels obtained > six weeks after primary THA were compared between 50 infected and 88 non-infected THAs, and in patients with symptoms for more than or less than two weeks. Diagnostic thresholds for the synovial WBC count were calculated using area under the curve calculation. Results. The synovial WBC count was significantly higher in patients with symptoms for ≤ two weeks compared with those with symptoms for > two weeks (p = 0.03). The optimal threshold for diagnosing PJI for the synovial WBC count was 5750 cells/µL (sensitivity 94; specificity 100; PPV 100%; NPV 89%; AUC 99%) and 1556 cells/µL (sensitivity 91; specificity 94; PPV 87% and NPV 97%; AUC 95%), respectively. The thresholds for the cut-offs based on duration of symptoms improved the diagnostic performance of this test. Conclusion. This study shows that the diagnostic thresholds for synovial fluid analysis in late periprosthetic infection following THA may depend on duration of symptoms. Cite this article: Bone Joint J 2016;98-B:1355–9

Purpose of study and background. Psychological factors are considered to play a role in development and maintenance of chronic low back pain (CLBP). Stress or anxiety can change pain sensitivity; however, this has predominantly been studied in healthy individuals with limited work in individuals with musculoskeletal pain. The objective of this study was to quantify the effect of acute exposure to a psychosocial stressor on mechanical pain sensitivity in individuals with and without CLBP. Summary of methods and results. Six individuals with CLBP and 10 individuals without CLBP performed a 10-minute computer task under conditions of low and high psychosocial stress. Psychosocial stress was manipulated using mental maths and memory tasks combined with social evaluative threat. The effect of the stressor was evaluated using blood pressure, heart rate and the state anxiety component of the Spielberger State-Trait Anxiety Index. Mechanical pressure pain threshold (PPT) was recorded on the tibialis anterior muscle using a handheld digital pressure algometer. The stress manipulation increased self-reported anxiety (p<0.001), but not blood pressure or heart rate (p>0.06). Change in PPT from low to high stress was greater in the CLBP group (median ΔPPT = −0.5 kg/cm. 2. ) than in the control group (−0.15 kg/cm. 2. ; p=0.005). Conclusion. Individuals experienced an increase in pain sensitivity after acute exposure to a stressor designed to mimic low-level workplace stressors, and this increase was greater in individuals with CLBP than asymptomatic individuals. These results indicate that this experimental model can be used to study links between pain sensitivity and psychosocial stressors and increase our understanding of their potential role in CLBP. Conflicts of Interest: No conflicts of interest. Sources of funding: No funding obtained

The process of femoral impaction grafting requires vigorous impaction to obtain adequate stability but the force of impaction has not been determined. This process has been reported to result in femoral fractures with rates reaching 16%. The aims of this study were to determine the threshold force required for femoral impaction grafting, to determine the affect cortical thickness, canal diameter and bone mineral density (BMD) have on this threshold force and to measure subsidence of an Exeter prosthesis following impaction at the threshold force. Adult sow femurs were prepared and placed through a DEXA scanner and the BMD and canal diameter measured. Thirty five femurs were impacted with morsellised bone chips and an increasing force of 0.5kN was applied until the femur fractured. Using callipers the cortical thickness of the bone was measured along the fracture line. Once the threshold force was determined 5 femurs were impacted to this threshold force and an Exeter stem was cemented into the neomedullary canal and a 28mm Exeter head attached. Axial cyclic loading was performed between 440N (swing phase of gait) and 1320N (stance phase of gait) for 150,000 cycles at a frequency of 3Hz. The position sensor of the hydraulic testing machine measured the subsidence. 29 tests were successfully completed. The threshold force was found to be 4kN. There was no significant correlation between the load at fracture and the cortex: canal ratio or the bone mineral density. Following impaction with the maximum force of 4kN the average subsidence for the 5 femurs was 0.276mm (range 0.235 – 0.325mm). In this animal study the threshold force was 4kN. Minimal axial subsidence of the implant occurred when impacting the graft with this threshold force. We therefore achieved a stable construct without fracture which is the ultimate goal for the revision hip surgeon

Introduction: Sensory hypersensitivity, central hyper-excitability (lowered nociceptive flexion reflex (NFR) thresholds) and psychological distress are features of chronic whiplash. Relationships between these substrates are not clear. The aim of this study was to investigate relationships between psychological factors (distress, catastrophization) and pain threshold responses to sensory stimuli and spinal cord excitability as assessed by the NFR. The former assessments are considered as global pain responses to sensory stimuli as reported by the patient, whereas the latter, an objective measurement for spinal cord excitability to peripheral stimulation. Methods: 30 individuals with chronic (> 3 months) whiplash (Grade II or III; Grade IV were excluded) and 30 asymptomatic controls participated. Pressure pain thresholds (PPTs) and thermal pain thresholds (Thermotest, Somedic AB, Sweden) were measured at the cervical spine, upper and lower limbs. The NFR (intensity of electrical stimulation at the sural nerve required to elicit reflex EMG activity of biceps femoris) was measured as per previous protocols (1). Pain and disability levels (NDI), psychological distress (GHQ-28) and catastrophisation (PCS) were also measured in the whiplash group. Ethical clearance for this study was granted by the Medical Research Ethics Committee of the University of Qld. A MANCOVA was used to determine differences between the whiplash group and controls for sensory measures and the NFR. GHQ-28 and PCS scores were used as covariates in the analysis. Group differences for questionnaire data (GHQ-28 and PCS) were analysed using one way ANOVA. Pearson’s correlation coefficients were used to determine the relationship between the psychological measures (PCS and GHQ-28), pain and disability levels (NDI) and the pain threshold measures (mechanical and thermal) and to determine relationships between the psychological measures, pain and disability measures (NDI) and NFR responses (pain intensity at threshold, threshold). p< 0.05. Results: Whiplash injured participants (23 females, mean (SD) age: 37.7 (11.5) years, NDI: 46.2 (17.6) and VAS scores of pain: 4.2 (2.4)) demonstrated lowered pain thresholds to pressure and cold (p< 0.05); lowered NFR thresholds (p=0.003) and above threshold levels of psychological distress (GHQ-28) compared to controls and levels of catastrophisation comparable to other musculoskeletal conditions. There were no group differences for heat pain thresholds or pain at NFR threshold. In the whiplash group, PCS scores correlated moderately with cold pain threshold (r =0.51, p=0.01). In contrast there were no significant correlations between GHQ-28 scores and pain threshold measures or between psychological factors and NFR responses in whiplash participants. There were no significant correlations between psychological factors and pain thresholds or NFR responses in controls. Discussion: We have demonstrated that psychological factors have some association with sensory hypersensitivity (cold pain threshold measures) in chronic whiplash but do not seem to influence spinal cord excitability. This suggests that psychological disorders are important, but not the only, determinants of central hypersensitivity in whiplash patients. These findings suggest that both physical and psychological factors will need to be addressed in the management of whiplash

The threshold for decompression in acute compartment syndrome is quoted as a pressure difference between the compartment and diastolic blood pressure of less than 30mmHg. This study reports the findings of continuous compartment pressure monitoring in children who underwent tibial osteotomies. In this prospective observational study, twenty seven children who underwent tibial osteotomies had anterior compartment pressures monitored using a transducer-tipped probe for a minimum of 72 hours following surgery. Pressure data were collected hourly together with evidence of clinical signs, symptoms and patterns of analgesic use. Patients were also reviewed for late sequelae of compartment syndrome. One case of compartment syndrome were encountered. Pressure differences (diastolic BP - compartment pressure) were found to vary widely, with many children exceeding the threshold for decompression but without manifesting other signs of compartment syndrome. Fasciotomies were not performed in view of the conflicting evidence and subsequent review confirmed the absence of late sequelae. In these children, low diastolic blood pressures were a common but normal feature. The prevalence of compartment syndrome was 3.7% (1/27). The positive predictive value of using the adult threshold was 7.1%; the negative predictive value was 100%. We conclude that the threshold for decompression as applied to adults is unsuitable for use in children inasmuch as a positive result would lead to a correct diagnosis in only 7.1% of children. A negative test is more useful in correctly excluding compartment syndrome in 100% of the children studied

Background: Quantitative sensory testing (QST) conventionally identifies threshold elevation as reflecting sensory deficit. A major disadvantage of the technique is its inability to distinguish organic from feigned sensory deficit, as both are characterized by an elevated threshold. Aim: To distinguish organic from feigned sensory deficit. Method: Vibratory thresholds and their variances were measured, at foot L4, L5 and S1 sites, in 14 patients with low back pain (LBP) suspected of non-organic sensory loss by clinical criteria of Waddell, 14 patient controls with abnormal neurological examination and CT of the low back, and 20 healthy controls. Results: Thresholds of non-organic patients and of patient controls were elevated to a similar extent compared to those of healthy controls. Variances, however, were higher for non-organic patients (6.7–10.5 for the various test sites) than for either patient controls (0.39–0.80, p: 0.001–0.05) or for healthy controls (0.20–0.54, p: 0.001–0.02). Of non-organic patients with high thresholds who would otherwise be identified as pathological, 30–67% were ‘spared’ the misdiagnosis and correctly identified as non-organic because of the inclusion of the variance criterion. Conclusion: Variance evaluation is therefore suggested for inclusion into QST methodology, together with threshold itself, as a quality assurance parameter

Serological tests including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are frequently used in the preoperative workup to screen for periprosthetic infection (PPI) in total hip arthroplasty (THA). The cut-off points reported in the literature are arbitrarily chosen by investigators. Similarly, the values used in laboratories to distinguish elevated results vary from one institute to another. Therefore, we intended to define the appropriate cut-off points of ESR and CRP that can be used to differentiate infection from aseptic failure of THA. A review of our joint registry database revealed that 515 THA revisions (131 infected cases) were performed during 2000–2005. Intraoperative samples for culture were taken in all cases. The criteria used for diagnosis of infection were a positive intraoperative culture on solid media, presence of an abscess or sinus tract that communicated with the joint, positive preoperative aspiration culture, and/or elevated fluid cell count and neutrophil differential of the aspirated fluid. Non-infected patients with confounding factors that can elevate ESR and CRP including collagen vascular disease, inflammatory arthropathy, malignancy, and urinary tract infection were excluded. Receiver operator curves were used to determine the ideal cut-off point for both ESR and CRP. The mean value of ESR in the infected group (77mm/ hr) was significantly higher compared to that of the non-infected cohort (29mm/hr) (p=0.0001). Similarly, infected patients presented with a greater mean CRP (9.8 mg/dl) than their non-infected cohort (1.48 mg/ dl) (p=0.0001). The infection threshold for ESR was 45mm/hr with a sensitivity of 85% and specificity of 79%, while the optimal cut-off value for CRP was defined as 1.6 mg/dl which yielded a sensitivity of 86% and specificity of 83%. The optimal threshold values we determined are higher than the arbitrarily chosen values cited in the literature for ESR (30mm/hr) and CRP (1mg/dl). Although it has been previously reported that the sensitivity and specificity of CRP are far greater than that of ESR, we found that the two tests have comparable diagnostic value

Aims

Total hip arthroplasty (THA) is a very successful and cost-effective operation, yet debate continues about the optimum fixation philosophy in different age groups. The concept of the 'cementless paradox' and the UK 'Getting it Right First Time' initiative encourage increased use of cemented fixation due to purported lower revision rates, especially in elderly patients, and decreased cost.

The aim was to determine reliability in treatment threshold based on USS angular measurements between observers involved in the DDH hip screening programme at the NOC and assess the effect of image orientation on the accuracy of these measurements. 3 independent observers measured alpha and beta angles on bilateral hips in 10 consecutive patients seen in the DDH hip screening clinic. All scans were performed by a single radiographer and observers used the same set of USS images for a given patient. Each observer measured alpha and beta angles a total of 4 times: conventional ultrasound image projection (with the ilium horizontal) (round 1), Graf's anatomical projection (round 2), and both techniques repeated 1 month later (round 3 and 4 respectively) to assess intra-observer reliability. To determine its effect on treatment threshold taking into account alpha and beta angles and patient's age, the consistency between observers' management recommendations was evaluated for each round. Possible outcomes were: 1) patient discharged, 2) no treatment needed yet, but follow-up required, 3) start treatment. Intra-observer reliability for conventional projection was moderate (Kappa 0.58), and improved for anatomical projection (Kappa 0.65). Inter-observer reliability, as a surrogate measure of consistency in management recommendations between observers, ranged from fair to moderate across the 4 rounds (Kappa 0.30 – 0.50). However, contrary to previous recommendations, reliability was better with conventional projection (Kappa 0.41 (95% CI 0.11–0.72)) compared to anatomical projection (Kappa 0.36 (95% CI −0.01–0.73)). The overall agreement in management recommendations, pooling all results across 4 rounds, was 51.3% (Kappa 0.39 (95%CI 0.15–0.63)). This audit supports the argument that anatomical image projection improves intra-observer consistency. However, as with all USS measurements, angular measurements were highly user dependent and treatment threshold based on USS may not be as consistent as anticipated

It has been suggested that metal ion level elevations in certain bilateral MM bearing arthroplasties were overwhelming the renal threshold for metal excretion leading to systemic build-up of metal ions above the expected levels. In order to investigate this we studied renal concentrating efficacy through concurrent specimens of urine and whole blood over a range of metal levels. Concurrent specimens from 305 unselected patients were obtained. They include preoperative patients (76) and those with unilateral and bilateral hip arthroplasties (229) through to ten years after operation. 39 pre-operative specimens and 4 follow-up specimens had blood levels at or below the detection limit for cobalt or chromium and were excluded. The ratio of urine to whole blood concentration was 0.78 in the pre-operative patients. In patients with MM arthroplasties the different ratios in patients increased (from 3.1 to 9.2) with increasing urine concentrations. The ratio of urine cobalt concentration to blood cobalt concentration is a measure of renal concentrating efficacy. Amongst pre-operative controls, this ratio is 0.78, indicating that there is renal conservation of cobalt. In terms of cobalt, these patients’ urine was dilute in comparison to whole blood. In patients with MM bearings, the ratio went up to 4.8 indicating that the kidneys were now actively excreting against a concentration gradient in an attempt to maintain internal milieu. If renal threshold was being breached at higher levels, then the ratio should progressively fall at higher concentrations. The trend in this experiment shows quite the contrary effect and the ratio reached 9.2 in those with urine cobalt > 15 μg/l, demonstrating that renal clearance efficiency holds up even against this steep gradient and that the threshold is not breached within clinically relevant levels

Although wait-times for hip fracture surgery have been linked to mortality and are being used as quality-of-care indicators worldwide, controversy exists about the duration of the wait that leads to complications. Our objective was to use new population-based wait-time data to emprically derive an optimal time window in which to conduct hip fracture surgery before the risk of complications increases. We used health administrative data from Ontario, Canada to identify hip fracture patients between 2009 and 2014. The main exposure was the time from hospital arrival to surgery (in hours). The primary outcome was mortality within 30 days. Secondary outcomes included a composite of mortality or other medical complications (MI, DVT, PE, and pneumonia) also within 30 days. Risk-adjusted cubic splines modeled the probability of each complication according to wait-time. The inflection point (in hours) when complications began to increase was used to define ‘early’ and ‘delayed’ surgery. To evaluate the robustness of this definition, outcomes amongst propensity-score matched early and delayed patients were compared using percent absolute risk differences (% ARDs, with 95% confidence intervals [CIs]). There were 42,230 patients who met entry criteria. Their mean age was 80.1 (±10.7) and the majority were female (70.5%). The risk of complications modeled by cubic splines consistently increased when wait-times were greater than 24 hours, irrespective of the complication considered. Compared to 13,731 propensity-score matched patients who received surgery earlier, 13,731 patients receiving surgery after 24 hours had a significantly higher risk of 30-day mortality (N=898 versus N=790, % ARD 0.79 [95% CI 0.23 to 1.35], p = .006) and the composite outcome (N=1,680 versus N=1,383, % ARD 2.16 [95% CI 1.43 to 2.89], p < .001). Overall, there were 14,174 patients (33.6%) who received surgery within 24 hours and 28,056 patients (66.4%) who received surgery after 24 hours. Increased wait-time was associated with a greater risk for 30-day mortality and other complications. The finding that a wait-time of 24 hours represents a threshold defining higher risk may inform existing hip fracture guidelines. Since two-thirds of patients did not receive surgery within this timeframe, performance improvement efforts that reduce wait-times are warranted

We studied 27 patients with low back pain and unilateral L5 or S1 spinal nerve root pain. Significant radiological changes were restricted to the symptomatic root level, when compared with controls. Low back and leg pain were graded on a visual analogue scale. Dermatomal quantitative sensory tests revealed significant elevations of warm, cool and touch perception thresholds in the affected dermatome, compared with controls. These elevations correlated with root pain (warm v L5 root pain; r = 0.88, p < 0.0001), but not with back pain. Low back pain correlated with restriction of anteroposterior spinal flexion (p = 0.02), but not with leg pain. A subset of 16 patients underwent decompressive surgery with improvement of pain scores, sensory thresholds and spinal mobility. A further 14 patients with back pain, multilevel nerve root symptoms and radiological changes were also studied. The only correlation found was of low back pain with spinal movement (p < 0.002). We conclude that, in patients with single level disease, dermatomal sensory threshold elevation and restriction of spinal movement are independent correlates of sciatica and low back pain

Aim of the study: To calculate minimum-provider-volumes in total knee replacement by means of German routine data for the first time. Materials and methods: In patients with primary total knee replacement (TKR) the correlation between hospital volume per year and risk of “insufficient mobility” (primary quality indicator) and “wound infection” (secondary quality indicator) was calculated by means of logistic regression models based on the data of 110.349 primary total knee replacements operated in 1.016 German hospitals in 2004. Results: For both indicators a statistically significant relationship between hospital volume and outcome could be proven. Other risk factors such as age and ASA-status also had a significant influence, but did not appear as important confounders. The risk for the secondary quality indicator “infection” decreased constantly by increasing hospital volume, thus the curve was very flat. This supports the hypothesis that high volume hospitals show up to have a higher quality level than low-volume hospitals. A threshold value of 116 TKR per year (95% CI 90–141) could be calculated. However, the explanation value of the hospital volume was too low to derive a threshold level that clearly discriminates between good and bad quality of care. The relationship between the primary quality indicator “insufficient mobility” and the hospital volume unexpectedly showed a U-shaped distribution. This questions the concept of a minimum provider volume regulation for primary total knee replacement regarding the risk factor “insufficient mobility”. Therefore, in this case no quantitative threshold values were calculated. Conclusion: This analysis supports the hypothesis of a volume-outcome-relationship in primary total knee replacement. However, a minimum provider volume that clearly discriminates between good and bad quality of care could not be calculated on basis of German quality assurance data