Showing papers by "Nuffield Orthopaedic Centre published in 2011"

"Asymptomatic" pseudotumors after metal-on-metal hip resurfacing arthroplasty: prevalence and metal ion study.

Abstract: Symptomatic abnormal periprosthetic soft-tissue reactions ("pseudotumors") have been reported after metal-on-metal hip resurfacing arthroplasty (MoMHRA). The aims of this study were (1) to determine the prevalence of asymptomatic pseudotumors after MoMHRA and (2) to measure metal ion levels in these patients. A total of 201 hips in 158 patients were evaluated at a mean follow-up of 61 months (range, 36-88) using ultrasound/magnetic resonance imaging and serum/hip aspirate cobalt and chromium measurements. Pseudotumors found in 7 patients (4%) were associated with significantly higher cobalt and chromium levels and inferior functional scores. Elevated levels of cobalt and chromium ions suggest that pseudotumors are associated with increased wear generated from metal-on-metal articulations. Clinicians need to be aware of pseudotumors as a differential diagnosis during clinical evaluation of MoMHRA patients, and further imaging such as ultrasound or magnetic resonance imaging is recommended to confirm the diagnosis.

Minimally invasive Oxford phase 3 unicompartmental knee replacement: RESULTS OF 1000 CASES

Abstract: This prospective study describes the outcome of the first 1000 phase 3 Oxford medial unicompartmental knee replacements (UKRs) implanted using a minimally invasive surgical approach for the recommended indications by two surgeons and followed up independently. The mean follow-up was 5.6 years (1 to 11) with 547 knees having a minimum follow-up of five years. At five years their mean Oxford knee score was 41.3 (sd 7.2), the mean American Knee Society Objective Score 86.4 (sd 13.4), mean American Knee Society Functional Score 86.1 (sd 16.6), mean Tegner activity score 2.8 (sd 1.1). For the entire cohort, the mean maximum flexion was 130° at the time of final review. The incidence of implant-related re-operations was 2.9%; of these 29 re-operations two were revisions requiring revision knee replacement components with stems and wedges, 17 were conversions to a primary total knee replacement, six were open reductions for dislocation of the bearing, three were secondary lateral UKRs and one was revision of a tibial component. The most common reason for further surgical intervention was progression of arthritis in the lateral compartment (0.9%), followed by dislocation of the bearing (0.6%) and revision for unexplained pain (0.6%). If all implant-related re-operations are considered failures, the ten-year survival rate was 96% (95% confidence interval, 92.5 to 99.5). If only revisions requiring revision components are considered failures the ten-year survival rate is 99.8% (confidence interval 99 to 100). This is the largest published series of UKRs implanted through a minimally invasive surgical approach and with ten-year survival data. The survival rates are similar to those obtained with a standard open approach whereas the function is better. This demonstrates the effectiveness and safety of a minimally invasive surgical approach for implanting the Oxford UKR.

A second decade lifetable survival analysis of the Oxford unicompartmental knee arthroplasty.

Abstract: Background The role of unicompartmental arthroplasty in managing osteoarthritis of the knee remains controversial. The Oxford medial unicompartmental arthroplasty employs a fully congruent mobile bearing intended to reduce wear and increase the lifespan of the implant. Long-term second decade results are required to establish if the design aim can be met.

Metal-on-metal bearings: THE EVIDENCE SO FAR

Abstract: Lately, concerns have arisen following the use of large metal-on-metal bearings in hip replacements owing to reports of catastrophic soft-tissue reactions resulting in implant failure and associated complications. This review examines the literature and contemporary presentations on current clinical dilemmas in metal-on-metal hip replacement.

High failure rates with a large-diameter hybrid metal-on-metal total hip replacement: CLINICAL, RADIOLOGICAL AND RETRIEVAL ANALYSIS

Abstract: This study reports the mid-term results of a large-bearing hybrid metal-on-metal total hip replacement in 199 hips (185 patients) with a mean follow-up of 62 months (32 to 83). Two patients died of unrelated causes and 13 were lost to follow-up. In all, 17 hips (8.5%) have undergone revision, and a further 14 are awaiting surgery. All revisions were symptomatic. Of the revision cases, 14 hips showed evidence of adverse reactions to metal debris. The patients revised or awaiting revision had significantly higher whole blood cobalt ion levels (p = 0.001), but no significant difference in acetabular component size or position compared with the unrevised patients. Wear analysis (n = 5) showed increased wear at the trunnion-head interface, normal levels of wear at the articulating surfaces and evidence of corrosion on the surface of the stem. The cumulative survival rate, with revision for any reason, was 92.4% (95% confidence interval 87.4 to 95.4) at five years. Including those awaiting surgery, the revision rate would be 15.1% with a cumulative survival at five years of 89.6% (95% confidence interval 83.9 to 93.4). This hybrid metal-on-metal total hip replacement series has shown an unacceptably high rate of failure, with evidence of high wear at the trunnion-head interface and passive corrosion of the stem surface. This raises concerns about the use of large heads on conventional 12/14 tapers.

The association between hip morphology parameters and nineteen-year risk of end-stage osteoarthritis of the hip: a nested case-control study.

Abstract: Objective. Subtle deformities of the hip joint are implicated in the etiology of osteoarthritis (OA) of the hip. Parameters that quantify these deformities may aid understanding of these associations. We undertook this study to examine relationships between such parameters and the 19-year risk of total hip arthroplasty (THA) for end-stage OA. Methods. A new software program designed for measuring morphologic parameters around the hip was developed and validated in a reliability study. THA was the outcome measure for end-stage OA. A nested case– control study was used with individuals from a cohort of 1,003 women who were recruited at year 1 in 1989 and followed up to year 20 (the Chingford Study). All hips with THA by year 20 and 243 randomly selected control hips were studied. Pelvis radiographs obtained at year 2 were analyzed for variations in hip morphology. Measurements were compared between the THA case group and the control group. Results. Patients with THA had a higher prevalence of cam deformity than did their respective controls (median alpha angle 62.4° versus 45.8° [P ? 0.001]; mean modified triangular index height 28.5 mm versus 26.9 mm [P ? 0.001]) as well as a higher prevalence of acetabular dysplasia (mean lateral center edge angle 29.5° versus 34.3° [P ? 0.001]; median extrusion index 0.25 versus 0.185 [P ? 0.009]). Logistic regression analyses clustering by subject and adjusting for radiographic hip OA at year 2 showed that these morphologic parameters were still significantly associated with THA by year 20. The alpha angle and lateral center edge angle predicted the risk of THA independently when included in the same model. Conclusion. This investigation describes measurements that predict the risk of THA for end-stage OA by year 20, independently of the presence of radiographic hip OA at year 2. These measurements can be made on an anteroposterior pelvis radiograph, which is an inexpensive and commonly used clinical method of investigation.

Association of variants at 1q32 and STAT3 with ankylosing spondylitis suggests genetic overlap with Crohn's disease.

Abstract: Ankylosing spondylitis (AS) is a common inflammatory arthritic condition. Overt inflammatory bowel disease (IBD) occurs in about 10% of AS patients, and in addition 70% of AS cases may have subclinical terminal ileitis. Spondyloarthritis is also common in IBD patients. We therefore tested Crohn's disease susceptibility genes for association with AS, aiming to identify pleiotropic genetic associations with both diseases. Genotyping was carried out using Sequenom and Applied Biosystems TaqMan and OpenArray technologies on 53 markers selected from 30 Crohn's disease associated genomic regions. We tested genotypes in a population of unrelated individual cases (n = 2,773) and controls (n = 2,215) of white European ancestry for association with AS. Statistical analysis was carried out using a Cochran-Armitage test for trend in PLINK. Strong association was detected at chr1q32 near KIF21B (rs11584383, P = 1.6×10−10, odds ratio (OR) = 0.74, 95% CI:0.68–0.82). Association with disease was also detected for 2 variants within STAT3 (rs6503695, P = 4.6×10−4. OR = 0.86 (95% CI:0.79–0.93); rs744166, P = 2.6×10−5, OR = 0.84 (95% CI:0.77–0.91)). Association was confirmed for IL23R (rs11465804, P = 1.2×10−5, OR = 0.65 (95% CI:0.54–0.79)), and further associations were detected for IL12B (rs10045431, P = 5.2×10−5, OR = 0.83 (95% CI:0.76–0.91)), CDKAL1 (rs6908425, P = 1.1×10−4, OR = 0.82 (95% CI:0.74–0.91)), LRRK2/MUC19 (rs11175593, P = 9.9×10−5, OR = 1.92 (95% CI: 1.38–2.67)), and chr13q14 (rs3764147, P = 5.9×10−4, OR = 1.19 (95% CI: 1.08–1.31)). Excluding cases with clinical IBD did not significantly affect these findings. This study identifies chr1q32 and STAT3 as ankylosing spondylitis susceptibility loci. It also further confirms association for IL23R and detects suggestive association with another 4 loci. STAT3 is a key signaling molecule within the Th17 lymphocyte differentiation pathway and further enhances the case for a major role of this T-lymphocyte subset in ankylosing spondylitis. Finally these findings suggest common aetiopathogenic pathways for AS and Crohn's disease and further highlight the involvement of common risk variants across multiple diseases.

Unnecessary contraindications for mobile-bearing unicompartmental knee replacement

Abstract: The contraindications for unicompartmental knee replacement (UKR) remain controversial. The views of many surgeons are based on Kozinn and Scott's 1989 publication which stated that patients who weighed more than 82 kg, were younger than 60 years, undertook heavy labour, had exposed bone in the patellofemoral joint or chondrocalcinosis, were not ideal candidates for UKR. Our aim was to determine whether these potential contraindications should apply to patients with a mobile-bearing UKR. In order to do this the outcome of patients with these potential contraindications was compared with that of patients without the contraindications in a prospective series of 1000 UKRs. The outcome was assessed using the Oxford knee score, the American Knee Society score, the Tegner activity score, revision rate and survival. The clinical outcome of patients with each of the potential contraindications was similar to or better than those without each contraindication. Overall, 678 UKRs (68%) were performed in patients who had at least one potential contraindication and only 322 (32%) in patients deemed to be ideal. The survival at ten years was 97.0% (95% confidence interval 93.4 to 100.0) for those with potential contraindications and 93.6% (95% confidence interval 87.2 to 100.0) in the ideal patients. We conclude that the thresholds proposed by Kozinn and Scott using weight, age, activity, the state of the patellofemoral joint and chondrocalcinosis should not be considered to be contraindications for the use of the Oxford UKR.

The seven-year wear of highly cross-linked polyethylene in total hip arthroplasty: a double-blind, randomized controlled trial using radiostereometric analysis.

Abstract: Background: The use of highly cross-linked polyethylene is now commonplace in total hip arthroplasty. Hip simulator studies and short-term in vivo measurements have suggested that the wear rate of highly cross-linked polyethylene is significantly less than that of conventional ultra-high molecular weight polyethylene. However, long-term data to support its use are limited. The aim of this study was to compare the intermediate-term steady-state wear of highly cross-linked polyethylene compared with that of conventional ultra-high molecular weight polyethylene acetabular liners in a prospective, double-blind, randomized controlled trial with use of radiostereometric analysis. Methods: Fifty-four patients were randomized to receive hip replacements with either conventional ultra-high molecular weight polyethylene acetabular liners (Zimmer) or highly cross-linked polyethylene liners (Longevity; Zimmer). All patients received a cemented, collarless, polished, tapered femoral component (CPT; Zimmer) and an uncemented acetabular component (Trilogy; Zimmer). Clinical outcomes were assessed and the three-dimensional penetration of the head into the socket was determined for a minimum of seven years. Linear regression was used to calculate the steady-state wear rate following the creep-dominated penetration seen during the first year. Results: At a minimum of seven years postoperatively, the mean total femoral head penetration was significantly lower in the highly cross-linked polyethylene group (0.33 mm; 95% confidence interval [CI], ±0.10 mm) than it was in the ultra-high molecular weight polyethylene group (0.55 mm; 95% CI, ±0.10 mm) (p = 0.005). The mean steady-state wear rate of highly cross-linked polyethylene was 0.005 mm/yr (95% CI, ±0.015 mm/yr), compared with 0.037 mm/yr (95% CI, ±0.019 mm/yr) for conventional ultra-high molecular weight polyethylene (p = 0.007). No patient in the highly cross-linked polyethylene group had a wear rate above the osteolysis threshold of 0.1 mm/yr, compared with 9% of patients in the ultra-high molecular weight polyethylene group. Conclusions: This study demonstrates that highly cross-linked polyethylene has a significantly lower steady-state wear rate compared with that of conventional ultra-high molecular weight polyethylene. Longer-term follow-up is required to determine if this will translate into improved clinical performance and longevity of these implants. Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

A model to predict cardiovascular events in patients with newly diagnosed Wegener's granulomatosis and microscopic polyangiitis

Abstract: Objective. To create a prognostic tool to quantify the 5-year cardiovascular (CV) risk in patients with newly diagnosed Wegener's granulomatosis (WG) and microscopic polyangiitis (MPA) without premorbid CV disease. Methods. We reviewed CV outcomes during the long-term followup of patients in the first 4 European Vasculitis Study Group (EUVAS) trials of WG and MPA. CV events were defined as CV death, stroke, myocardial infarction, coronary artery bypass graft, or percutaneous coronary intervention. Logistic regression was performed to create a model to predict the absolute risk of a CV event. The model was tested using the Wegener's Granulomatosis Etanercept Trial (WGET) cohort. Results. Seventy-four (13.8%) of 535 patients with 5 years of followup from the EUVAS trials had at least 1 CV event: 33 (11.7%) of 281 WG versus 41 (16.1%) of 254 MPA. The independent determinants of CV outcomes were older age (odds ratio [OR] 1.45, 95% confidence interval [95% CI] 1.11-1.90), diastolic hypertension (OR 1.97, 95% CI 0.98-3.95), and positive proteinase 3 (PR3) antineutrophil cytoplasmic antibody (ANCA) status (OR 0.39, 95% CI 0.20-0.74). The model was validated using the WGET cohort (area under the receiver operating characteristic curve of 0.80). Conclusion. Within 5 years of diagnosis of WG or MPA, 14% of patients will have a CV event. We have constructed and validated a tool to quantify the risk of a CV event based on age, diastolic hypertension, and PR3 ANCA status in patients without prior CV disease. In patients with vasculitis, PR3 ANCA is associated with a reduced CV risk compared to myeloperoxidase ANCA or negative ANCA status.

Evidence that central sensitisation is present in patients with shoulder impingement syndrome and influences the outcome after surgery

Abstract: Impingement syndrome in the shoulder has generally been considered to be a clinical condition of mechanical origin. However, anomalies exist between the pathology in the subacromial space and the degree of pain experienced. These may be explained by variations in the processing of nociceptive inputs between different patients. We investigated the evidence for augmented pain transmission (central sensitisation) in patients with impingement, and the relationship between pre-operative central sensitisation and the outcomes following arthroscopic subacromial decompression. We recruited 17 patients with unilateral impingement of the shoulder and 17 age- and gender-matched controls, all of whom underwent quantitative sensory testing to detect thresholds for mechanical stimuli, distinctions between sharp and blunt punctate stimuli, and heat pain. Additionally Oxford shoulder scores to assess pain and function, and PainDETECT questionnaires to identify 'neuropathic' and referred symptoms were completed. Patients completed these questionnaires pre-operatively and three months post-operatively. A significant proportion of patients awaiting subacromial decompression had referred pain radiating down the arm and had significant hyperalgesia to punctate stimulus of the skin compared with controls (unpaired t-test, p < 0.0001). These are felt to represent peripheral manifestations of augmented central pain processing (central sensitisation). The presence of either hyperalgesia or referred pain pre-operatively resulted in a significantly worse outcome from decompression three months after surgery (unpaired t-test, p = 0.04 and p = 0.005, respectively). These observations confirm the presence of central sensitisation in a proportion of patients with shoulder pain associated with impingement. Also, if patients had relatively high levels of central sensitisation pre-operatively, as indicated by higher levels of punctate hyperalgesia and/or referred pain, the outcome three months after subacromial decompression was significantly worse.

Osteonecrosis of the Jaw and the Role of Macrophages

Abstract: Nitrogen-containing bisphosphonates have been associated with the development of osteonecrosis of the jaws (ONJ), but the lack of reliable epidemiological data and appropriate animal models has restricted our understanding of ONJ pathophysiology and limited its management. The best available information is from histopathologic findings, which implicate bone necrosis and infection, although it is not clear which is primary. However, there are data suggesting that macrophages could well be the central factor in allowing the infection to develop first, followed by local necrosis, which could also account for the development of ONJ in patients treated with denosumab, a human monoclonal antibody to the receptor activator of nuclear factor-κB ligand. This review examines the evidence that macrophages could play a prominent role in development of ONJ and the proposal that it may be more appropriate to view ONJ as a drug and not only a bisphosphonate-related complication.

Case report: imaging and surgical treatment of a snapping hip due to ischiofemoral impingement

Abstract: An association between hip pain and quadratus femoris MRI abnormality with concurrent narrowing of the ischiofemoral space has been reported in a number of patients to date, raising the possibility that the muscular damage observed is due to ischiofemoral impingement [1]. Possible impingement has been noted primarily in middle-aged females either with or without a history of trauma or surgery, and associated snapping of the hip is a rarely described feature [1–3]. We report here on a 17-year-old girl who presented with post-traumatic hip pain; she later developed evidence of ischiofemoral narrowing and quadratus femoris edema on MRI in addition to an audible snapping. Surgical resection of the lesser trochanter was performed, relieving both her hip pain and the snapping. To our knowledge, this is the first reported case of non-iatrogenic ischiofemoral impingement with surgical confirmation. The diagnosis of ischiofemoral impingement should be considered in patients complaining of a snapping hip.

The role of classification of chronic low back pain.

Abstract: STUDY DESIGN Systematic review. OBJECTIVE To describe the various ways chronic low back pain (CLBP) is classified, to determine if the classification systems are reliable and to assess whether classification-specific interventions have been shown to be effective in treating CLBP. SUMMARY OF BACKGROUND DATA A classification system by which individual patients with CLBP could be identified and directed to an effective treatment protocol would be beneficial. Those systems that direct treatment have the greatest potential influence on patient outcomes. METHODS A systematic search was conducted in MEDLINE and the Cochrane Collaboration Library for English language literature published through January 2011. We included articles that specifically described a clinical classification system for CLBP, reported on the reliability of a classification system, or evaluated the effectiveness of classification-specific interventions. RESULTS A total of 60 articles were initially reviewed. We identified 28 classification systems that met inclusion criteria: 16 diagnostic systems, 7 prognostic systems, and 5 treatment-based systems. In addition, we found 10 randomized controlled trials of CLBP treatment from which we compared inclusion and exclusion criteria. Treatment-based systems were all directed at nonoperative management. Four of the 5 treatment-based systems underwent reliability testing and were found to have interobserver agreement of 70% to 100%. Reliability increased with training and familiarity with a given classification. As the number of subgroups within a classification increased, interobserver agreement decreased. Function and pain were similar between patients treated with the McKenzie classification system and those treated with dynamic strengthening training after 8 months of follow-up in one randomized controlled trial. One prospective cohort study reported better pain and function using the Canadian Back Institute Classification system than with standard rehabilitation. An analysis of the admission criteria to recent randomized studies with either nonoperative care or another surgical intervention provided a methodology for refining criteria to be met by patients considering surgery. CONCLUSION There currently are many classification systems for CLBP; some that are descriptive, some prognostic, and some that attempt to direct treatment. We recommend that no one classification system be adopted for all purposes. We further recommend that future efforts in developing a classification system focus on one that helps to direct both surgical and nonsurgical treatments. CLINICAL RECOMMENDATIONS There currently are many classification systems for CLBP; some that are descriptive, some prognostic, and some that attempt to direct treatment. We recommend that no one classification system be adopted for all purposes. We further recommend that future efforts in developing a classification system focus on one that helps to direct both surgical and nonsurgical treatments.

Exercise for multiple sclerosis: a single-blind randomized trial comparing three exercise intensities:

Abstract: Background: The most effective exercise dose has yet to be established for multiple sclerosis (MS).Objective: The aim of this study was to investigate the effect of different exercise intensities in people with MS.Methods: We completed a randomized comparator study of three cycling exercise intensities, with blinded assessment, was carried out in Oxford. Sixty-one adults with MS who fulfilled inclusion criteria were randomized at entry into the study, using a computer-generated list held by an exercise professional, into either: continuous (at 45% peak power, n = 20), intermittent (30 sec on, 30 sec off at 90% peak power, n = 21) or combined (10 min intermittent at 90% peak power then 10 min continuous at 45% peak power, n = 20) exercise for 20 min twice a week for 12 weeks in a leisure facility. Groups were assessed at: baseline, halfway (6 weeks), end intervention (12 weeks) and follow-up (24 weeks). Primary outcome measure was 2 min walk.Results: Fifty-five participants were included in the analysis (n...

Patellar resurfacing in total knee replacement: five-year clinical and economic results of a large randomized controlled trial.

Abstract: Background: There is conflicting evidence regarding the merits of patellar resurfacing during total knee arthroplasty, as many of the previous randomized controlled trials have not been adequately powered. Methods: A pragmatic, multicenter, randomized controlled trial was initiated in 1999 in the United Kingdom. Within a partial factorial design, 1715 patients were randomly allocated to receive or not receive patellar resurfacing during total knee arthroplasty. The primary outcome measure was the Oxford Knee Score; secondary measures included the Short Form-12, the EuroQoL 5D, cost, cost-effectiveness, and the need for subsequent knee surgery. Results: The mean Oxford Knee Score was 35 points at five years postoperatively in both groups. There was no significant difference between the groups with respect to the mean Oxford Knee Score (difference, 0.59 point; 95% confidence interval, –0.58 to 1.76 points) or any other outcome measure at five years postoperatively. The outcome was not affected by whether the patella was domed or anatomic. There was no significant difference between the two groups with respect to the prevalence of knee-related readmission, of minor or intermediate reoperation, or of subsequent patella-related surgery. The total health care cost for the primary arthroplasty, subsequent monitoring, and any revision surgery did not differ significantly between the two groups. Conclusions: In the largest randomized controlled trial of patellar resurfacing reported to date, the functional outcome, reoperation rate, and total health care cost five years after primary total knee arthroplasty were not significantly affected by the addition of patellar resurfacing to the surgical procedure. Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

Orthotic management of cerebral palsy: recommendations from a consensus conference.

Abstract: An international multidisciplinary group of healthcare professionals and researchers participated in a consensus conference on the management of cerebral palsy, convened by the International Society for Prosthetics and Orthotics. Participants reviewed the evidence and considered contemporary thinking on a range of treatment options including physical and occupational therapy, and medical, surgical and orthotic interventions. The quality of many of the reviewed papers was compromised by inadequate reporting and lack of transparency, in particular regarding the types of patients and the design of the interventions being evaluated. Substantial evidence suggests that ankle-foot orthoses (AFOs) that control the foot and ankle in stance and swing phases can improve gait efficiency in ambulant children (GMFCS levels I-III). By contrast, little high quality evidence exists to support the use of orthoses for the hip, spine or upper limb. Where the evidence for orthosis use was not compelling consensus was reached on recommendations for orthotic intervention. Subsequent group discussions identified recommendations for future research. The evidence to support using orthoses is generally limited by the brevity of follow-up periods in research studies; hence the extent to which orthoses may prevent deformities developing over time remains unclear. The full report of the conference can be accessed free of charge at www.ispoint.org.

Unicompartmental knee arthroplasties implanted for osteoarthritis with partial loss of joint space have high re-operation rates.

Abstract: The indications and contraindications for unicompartmental knee arthroplasty (UKA) are controversial. The aim of the study was to determine the risk factors for re-operation in our practice. A series of 113 medial UKAs with mean follow-up of 63 months were reviewed retrospectively. Pre-operatively all knees had radiographic or arthroscopic evidence of severe cartilage damage. The re-operation rate was not related to age, gender, arthroscopic finding or body mass index. It was related to the joint space on pre-operative standing weight bearing radiographs taken in extension. The re-operation rate was 6 (95% CI 2.1-17, P 2 mm rather than ≤2 mm. It was 8 (95% CI 2.8-22.5, P 40% of the thickness of the lateral space. The ratio of pre-operative joint spaces has a greater influence on revision rate than the absolute measurement and is independent of radiographic magnification or the patient's normal cartilage thickness. We therefore recommend that, in medial knee osteoarthritis, UKA should only be used if the pre-operative medial joint space on standing radiographs is ≤40% of the lateral joint space, even if severe cartilage damage is seen arthroscopically.

The Emotiv EPOC neuroheadset: an inexpensive method of controlling assistive technologies using facial expressions and thoughts?

Abstract: The EPOC neuroheadset is a commercially available device that allows game players to control a computer using their facial expressions or their thoughts. This paper aims to examine whether it has the potential to be used as an input for assistive technology (AT) devices. Two experiments were conducted. In the first, 12 non-impaired subjects used the neuroheadset to control a computer with their facial expressions. They also used a simple system of two head switches for comparison. In the second experiment, three non-impaired subjects were trained to use the neuroheadset to control a computer with their thoughts. In the first experiment, the neuroheadset was slower and less accurate than the head switches (p<0.05), and was also harder to use. It is unlikely to be preferred to existing methods of accessing AT for those that retain a small amount of head movement. In the second experiment, by the end of the week, all three subjects achieved accuracy rates greater than chance. All subjects were non-impaired, and the sample size in the second experiment was small. Further research should concentrate on the second experiment, using larger sample sizes and impaired subjects. The EPOC neuroheadset is substantially cheaper than similar specialist devices, and has the potential to allow those with no voluntary muscle control to access AT with their thoughts. The results of these two experiments show that the Emotiv EPOC neuroheadset can be used as an interface for non-impaired users to transfer information to a computer, which could in turn be used to control AT.

Innate arthroscopic skills in medical students and variation in learning curves.

Abstract: Background: Technical skill is an essential domain of surgical competence, and arthroscopic surgery requires a particularly challenging subset of technical skills. The innate ability to acquire arthroscopic skills is not fully understood. The aim of this study was to investigate the innate arthroscopic skills and learning curve patterns of medical students. Methods: Tests of two arthroscopic tasks (one shoulder and one knee task designed to represent core skills required for arthroscopic training) were conducted in a surgical skills laboratory. The performance of twenty medical students with no previous arthroscopic surgery experience was assessed as they performed thirty repetitions of each task. The primary outcome measure for each repetition was success or failure in performing the task. An individual was deemed “competent” at the conclusion of the testing if he or she achieved stabilization of the learning curve (success on all subsequent repetitions) within twenty repetitions of the task. The secondary outcome measures were objective assessments of technical dexterity (time taken to complete the task, total length of the path traveled by the subject's hands, and number of hand movements) measured with use of a validated motion analysis system. Results: The performance on each task varied among the students. Seven students were unable to achieve competence in the shoulder task and four were unable to achieve competence in the knee task. Motion analysis demonstrated that students who achieved task competence had better objective technical dexterity and thus better innate arthroscopic ability. The total path length and the number of hand movements differed significantly between the students who did and did not become competent at the shoulder task (p < 0.05, Mann-Whitney U test). The difference in path length was also significant for students performing the knee task (p < 0.05). Conclusions: Variation in innate arthroscopic skill exists among future surgeons, with some individuals being unable to achieve competence in basic arthroscopic tasks despite sustained practice. Clinical Relevance: Identifying individuals who lack innate arthroscopic skills early in their career, in order to provide them with focused training and relevant career guidance, may be of great value.