Advertisement for orthosearch.org.uk
Results 1 - 20 of 22
Results per page:
The Bone & Joint Journal
Vol. 101-B, Issue 1 | Pages 55 - 62
1 Jan 2019
Rombach I Merritt N Shirkey BA Rees JL Cook JA Cooper C Carr AJ Beard DJ Gray AM

Aims

The aims of this study were to compare the use of resources, costs, and quality of life outcomes associated with subacromial decompression, arthroscopy only (placebo surgery), and no treatment for subacromial pain in the United Kingdom National Health Service (NHS), and to estimate their cost-effectiveness.

Patients and Methods

The use of resources, costs, and quality-adjusted life-years (QALYs) were assessed in the trial at six months and one year. Results were extrapolated to two years after randomization. Differences between treatment arms, based on the intention-to-treat principle, were adjusted for covariates and missing data were handled using multiple imputation. Incremental cost-effectiveness ratios were calculated, with uncertainty around the values estimated using bootstrapping.


The Bone & Joint Journal
Vol. 97-B, Issue 10 | Pages 1309 - 1315
1 Oct 2015
Price AJ Erturan G Akhtar K Judge A Alvand A Rees JL

Despite being one of the most common orthopaedic operations, it is still not known how many arthroscopies of the knee must be performed during training in order to develop the skills required to become a Consultant. A total of 54 subjects were divided into five groups according to clinical experience: Novices (n = 10), Junior trainees (n = 10), Registrars (n = 18), Fellows (n = 10) and Consultants (n = 6). After viewing an instructional presentation, each subject performed a simple diagnostic arthroscopy of the knee on a simulator with visualisation and probing of ten anatomical landmarks. Performance was assessed using a validated global rating scale (GRS). Comparisons were made against clinical experience measured by the number of arthroscopies which had been undertaken, and ROC curve analysis was used to determine the number of procedures needed to perform at the level of the Consultants.

There were marked differences between the groups. There was significant improvement in performance with increasing experience (p < 0.05).

ROC curve analysis identified that approximately 170 procedures were required to achieve the level of skills of a Consultant.

We suggest that this approach to identify what represents the level of surgical skills of a Consultant should be used more widely so that standards of training are maintained through the development of an evidenced-based curriculum.

Cite this article: Bone Joint J 2015;97-B:1309–15.


Bone & Joint Research
Vol. 3, Issue 5 | Pages 155 - 160
1 May 2014
Carr AJ Rees JL Ramsay CR Fitzpatrick R Gray A Moser J Dawson J Bruhn H Cooper CD Beard DJ Campbell MK

This protocol describes a pragmatic multicentre randomised controlled trial (RCT) to assess the clinical and cost effectiveness of arthroscopic and open surgery in the management of rotator cuff tears. This trial began in 2007 and was modified in 2010, with the removal of a non-operative arm due to high rates of early crossover to surgery.

Cite this article: Bone Joint Res 2014;3:155–60.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXIX | Pages 74 - 74
1 Jul 2012
Al-Ali S Alvand A Gill HS Beard DJ Jackson W Price AJ Rees JL
Full Access

Rheumatology and Musculoskeletal Sciences, NIHR Biomedical Research Unit, University of Oxford and the Nuffield Orthopaedic Hospital, Oxford

Purpose

The aim of this study was to use motion analysis to objectively study the learning curve of surgical trainees performing arthroscopic meniscal repair on a training model in a skills laboratory.

Background

With improving technology and an appreciation of its likely chondroprotective effects, meniscal repair surgery is becoming more common. It remains a difficult procedure and is not routinely learnt during surgical training.


The Journal of Bone & Joint Surgery British Volume
Vol. 93-B, Issue 12 | Pages 1586 - 1591
1 Dec 2011
Alvand A Auplish S Khan T Gill HS Rees JL

The aim of this study was to investigate the effect of training on the arthroscopic performance of a group of medical students and to determine whether all students could be trained to competence. Thirty-three medical students with no previous experience of arthroscopy were randomised to a ‘Trained’ or an ‘Untrained’ cohort. They were required to carry out 30 episodes of two simulated arthroscopic tasks (one shoulder and one knee). The primary outcome variable was task success at each episode. Individuals achieved competence when their learning curve stabilised. The secondary outcome was technical dexterity, assessed objectively using a validated motion analysis system. Six subjects in the ‘Untrained’ cohort failed to achieve competence in the shoulder task, compared with one in the ‘Trained’ cohort. During the knee task, two subjects in each cohort failed to achieve competence. Based on the objective motion analysis parameters, the ‘Trained’ cohort performed better on the shoulder task (p < 0.05) but there was no significant difference for the knee task (p > 0.05).

Although specific training improved the arthroscopic performance of novices, there were individuals who could not achieve competence despite focused training.These findings may have an impact on the selection process for trainees and influence individual career choices.


The Journal of Bone & Joint Surgery British Volume
Vol. 92-B, Issue 8 | Pages 1107 - 1111
1 Aug 2010
Rees JL Dawson J Hand GCR Cooper C Judge A Price AJ Beard DJ Carr AJ

We have compared the outcome of hemiarthroplasty of the shoulder in three distinct diagnostic groups, using survival analysis as used by the United Kingdom national joint registers, patient-reported outcome measures (PROMs) as recommended by Darzi in the 2008 NHS review, and transition and satisfaction questions.

A total of 72 hemiarthroplasties, 19 for primary osteoarthritis (OA) with an intact rotator cuff, 22 for OA with a torn rotator cuff, and 31 for rheumatoid arthritis (RA), were followed up for between three and eight years. All the patients survived, with no revisions or dislocations and no significant radiological evidence of loosening. The mean new Oxford shoulder score (minimum/worst 0, maximum/best 48) improved significantly for all groups (p < 0.001), in the OA group with an intact rotator cuff from 21.4 to 38.8 (effect size 2.9), in the OA group with a torn rotator cuff from 13.3 to 27.2 (effect size 2.1) and in the RA group from 13.7 to 28.0 (effect size 3.1). By this assessment, and for the survival analysis, there was no significant difference between the groups. However, when ratings using the patient satisfaction questions were analysed, eight (29.6%) of the RA group were ‘disappointed’, compared with one (9.1%) of the OA group with cuff intact and one (7.7%) of the OA group with cuff torn. All patients in the OA group with cuff torn indicated that they would undergo the operation again, compared to ten (90.9%) in the OA group with cuff intact and 20 (76.9%) in the RA group.

The use of revision rates alone does not fully represent outcome after hemiarthroplasty of the shoulder. Data from PROMs provides more information about change in pain and the ability to undertake activities and perform tasks. The additional use of satisfaction ratings shows that both the rates of revision surgery and PROMs need careful interpretation in the context of patient expectations.


The Journal of Bone & Joint Surgery British Volume
Vol. 92-B, Issue 3 | Pages 448 - 453
1 Mar 2010
Benson RT McDonnell SM Knowles HJ Rees JL Carr AJ Hulley PA

The aim of this study was to investigate the occurrence of tissue hypoxia and apoptosis at different stages of tendinopathy and tears of the rotator cuff.

We studied tissue from 24 patients with eight graded stages of either impingement (mild, moderate and severe) or tears of the rotator cuff (partial, small, medium, large and massive) and three controls. Biopsies were analysed using three immunohistochemical techniques, namely antibodies against HIF-1α (a transcription factor produced in a hypoxic environment), BNip3 (a HIF-1α regulated pro-apoptotic protein) and TUNEL (detecting DNA fragmentation in apoptosis).

The HIF-1α expression was greatest in mild impingement and in partial, small, medium and large tears. BNip3 expression increased significantly in partial, small, medium and large tears but was reduced in massive tears. Apoptosis was increased in small, medium, large and massive tears but not in partial tears.

These findings reveal evidence of hypoxic damage throughout the spectrum of pathology of the rotator cuff which may contribute to loss of cells by apoptosis. This provides a novel insight into the causes of degeneration of the rotator cuff and highlights possible options for treatment.


The Journal of Bone & Joint Surgery British Volume
Vol. 91-B, Issue 7 | Pages 915 - 917
1 Jul 2009
Gwilym SE Watkins B Cooper CD Harvie P Auplish S Pollard TCB Rees JL Carr AJ

The aim of this study was to investigate genetic influences on the development and progression of tears of the rotator cuff. From a group of siblings of patients with a tear of the rotator cuff and of controls studied five years earlier, we determined the prevalence of tears of the rotator cuff with and without associated symptoms using ultrasound and the Oxford Shoulder Score.

In the five years since the previous assessment, three of 62 (4.8%) of the sibling group and one of the 68 (1.5%) controls had undergone shoulder surgery. These subjects were excluded from the follow-up.

Full-thickness tears were found in 39 of 62 (62.9%) siblings and in 15 of 68 (22.1%) controls (p = 0.0001). The relative risk of full-thickness tears in siblings as opposed to controls was 2.85 (95% confidence interval (CI) 1.75 to 4.64), compared to 2.42 (95% CI 1.77 to 3.31) five years earlier. Full-thickness tears associated with pain were found in 30 of 39 (76.9%) tears in the siblings and in eight of 15 (53.3%) tears in the controls (p = 0.045). The relative risk of pain associated with a full-thickness tear in the siblings as opposed to the controls was 1.44 (95% CI 2.04 to 8.28) (p = 0.045).

In the siblings group ten of 62 (16.1%) had progressed in terms of tear size or development compared to one of 68 (1.5%) in the control group which had increased in size.

Full-thickness rotator cuff tears in siblings are significantly more likely to progress over a period of five years than in a control population. This implies that genetic factors have a role, not only in the development but also in the progression of full-thickness tears of the rotator cuff.


The Journal of Bone & Joint Surgery British Volume
Vol. 91-B, Issue 1 | Pages 119 - 123
1 Jan 2009
Benson RT McDonnell SM Rees JL Athanasou NA Carr AJ

We assessed the predictive value of the macroscopic and detailed microscopic appearance of the coracoacromial ligament, subacromial bursa and rotator-cuff tendon in 20 patients undergoing subacromial decompression for impingement in the absence of full-thickness tears of the rotator cuff. Histologically, all specimens had features of degenerative change and oedema in the extracellular matrix. Inflammatory cells were seen, but there was no evidence of chronic inflammation. However, the outcome was not related to cell counts.

At three months the mean Oxford shoulder score had improved from 29.2 (20 to 40) to 39.4 (28 to 48) (p < 0.0001) and at six months to 45.5 (36 to 48) (p < 0.0001). At six months, although all patients had improved, the seven patients with a hooked acromion had done so to a less extent than those with a flat or curved acromion judged by their mean Oxford shoulder scores of 43.5 and 46.5 respectively (p = 0.046). All five patients with partial-thickness tears were within this group and demonstrated less improvement than the patients with no tear (mean Oxford shoulder scores 43.2 and 46.4, respectively, p = 0.04). These findings imply that in the presence of a partial-thickness tear subacromial decompression may require additional specific treatment to the rotator cuff if the outcome is to be improved further.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 576 - 576
1 Aug 2008
Howells NR Carr AJ Price A Rees JL
Full Access

Objective: To investigate the effect of lab based simulator training, on the ability of basic surgical trainees to perform diagnostic knee arthroscopy.

Method: 20 orthopaedic SHO’s with minimal arthroscopic experience were randomised to 2 groups. 10 received a fixed protocol of simulator based arthroscopic skills training. This consisted of 3 sessions of 6 simulated arthroscopies using a Sawbones bench-top knee model. Their learning curve was assessed objectively using motion analysis. Time taken, path length and number of movements were recorded. All 20 then spent an operating list with a blinded consultant trainer. They received instruction and demonstration of diagnostic knee arthroscopy before performing the procedure independently. Their performance was assessed using the intra- operative section of the Orthopaedic Competence Assessment Project (OCAP) procedure based assessment (PBA) protocol for diagnostic arthros-copy and further quantified with a global rating assessment scale.

Results: In theatre, simulator-trained SHO’s outscored all but one untrained SHO. The simulator trained group were scored as competent on more than 70% of occasions compared to less than 15% for the un-trained group (p< 0.05). The mean global rating score of the trained group was 24.4 out of 45 compared with 12.4 for the untrained group (p< 0.05). Motion analysis demonstrated objective and significant improvement in performance during simulator training.

Conclusion: The use of lab based arthroscopic skills training leads to subsequent significant improvement in operating theatre performance. This may suggest that formalised lab based training should be a standardised part of future surgical curricula. OCAP PBA’s appear to provide a useful framework for assessment however potential questions are raised about the ability of OCAP to truly distinguish levels of surgical competence.


The Journal of Bone & Joint Surgery British Volume
Vol. 90-B, Issue 7 | Pages 827 - 832
1 Jul 2008
Rees JL

This review discusses the pathogenesis and surgical treatment of tears of the rotator cuff.


The Journal of Bone & Joint Surgery British Volume
Vol. 90-B, Issue 4 | Pages 494 - 499
1 Apr 2008
Howells NR Gill HS Carr AJ Price AJ Rees JL

The aim of this study was to investigate the effect of laboratory-based simulator training on the ability of surgical trainees to perform diagnostic arthroscopy of the knee.

A total of 20 junior orthopaedic trainees were randomised to receive either a fixed protocol of arthroscopic simulator training on a bench-top knee simulator or no additional training. Motion analysis was used to assess performance objectively. Each trainee then received traditional instruction and demonstrations of diagnostic arthroscopy of the knee in theatre before performing the procedure under the supervision of a blinded consultant trainer. Their performance was assessed using a procedure-based assessment from the Orthopaedic Competence Assessment Project and a five-point global rating assessment scale.

In theatre the simulator-trained group performed significantly better than the untrained group using the Orthopaedic Competence Assessment Project score (p = 0.0007) and assessment by the global rating scale (p = 0.0011), demonstrating the transfer of psychomotor skills from simulator training to arthroscopy in the operating theatre. This has implications for the planning of future training curricula.


The Journal of Bone & Joint Surgery British Volume
Vol. 89-B, Issue 5 | Pages 633 - 638
1 May 2007
Matthews TJW Smith SR Peach CA Rees JL Urban JPG Carr AJ

We have undertaken an in vivo assessment of the tissue metabolism and cellular activity in torn tendons of the rotator cuff. Cellular oxygen consumption was measured in 13 patients undergoing mini-open repair of small, medium, large and massive full-thickness tears. Measurements were also taken from three control patients who were undergoing open stabilisation of the shoulder with grossly normal tendons. The level of oxygen and nitrous oxide was measured amperometrically using silver needle microelectrodes at the apex of the tear and 1.5 cm from its edge. With nitrous oxide indicating the degree of perfusion, oxygen consumption was calculated at each location to reflect cellular activity.

All of the torn tendons had lower levels of cellular activity than the control group. This activity was lower still in the tissue nearest to the edge of the tear with the larger tears showing the lowest activity. This indicated reduced levels of tissue metabolism and infers a reduction in tendon viability.

Our findings suggest that surgical repair of torn tendons of the rotator-cuff should include the more proximal, viable tissue, and may help to explain the high rate of re-rupture seen in larger tears.


The Journal of Bone & Joint Surgery British Volume
Vol. 88-B, Issue 4 | Pages 489 - 495
1 Apr 2006
Matthews TJW Hand GC Rees JL Athanasou NA Carr AJ

We have studied cellular and vascular changes in different stages of full thickness tears of the rotator cuff. We examined biopsies from the supraspinatus tendon in 40 patients with chronic rotator cuff tears who were undergoing surgery and compared them with biopsies from four uninjured subscapularis tendons. Morphological and immunocytochemical methods using monoclonal antibodies directed against leucocytes, macrophages, mast cells, proliferative and vascular markers were used.

Histological changes indicative of repair and inflammation were most evident in small sized rotator cuff tears with increased fibroblast cellularity and intimal hyperplasia, together with increased expression of leucocyte and vascular markers. These reparative and inflammatory changes diminished as the size of the rotator cuff tear increased. Marked oedema and degeneration was seen in large and massive tears, which more often showed chondroid metaplasia and amyloid deposition. There was no association between the age of the patient and the duration of symptoms. In contrast, large and massive tears showed no increase in the number of inflammatory cells and blood vessels.

Small sized rotator cuff tears retained the greatest potential to heal, showing increased fibroblast cellularity, blood vessel proliferation and the presence of a significant inflammatory component. Tissue from large and massive tears is of such a degenerative nature that it may be a significant cause of re-rupture after surgical repair and could make healing improbable in this group.


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_IV | Pages 439 - 439
1 Apr 2004
Rees JL Price AJ Beard DJ McLardy-Smith P Dodd CAF Murray DW
Full Access

Introduction: A new procedure has been recently adopted to implant the Oxford medial unicompartmental arthroplasty (UCA). All cases are now implanted through a short incision without dislocation of the patella. The aims of this study were to assess the one-year results using this new technique and to determine if the outcome is dependent on surgical experience.

Method: The first 104 Oxford UCA’s (Phase 3) implanted by six surgeons under the care of two consultants were reviewed at one year. All operations were performed using the new technique. The average age at surgery was 68 years. All knees were scored pre-operatively and at review with the American Knee Society score. The cohort was divided into two groups; the first ten cases for each surgeon were included in a ‘learning’ group, whilst the remaining cases were included in an ‘experienced’ group.

Results: Overall the average ‘knee score’ improved from 37 points to 94 and the average ‘functional score’ from 50 points to 92. Average maximum flexion improved from 117° to 131°. The ‘knee score’ for the ‘learning’ group was 91 points. This was significantly less (p = 0.008) than the score of the ‘experienced’ group (96 points).

Conclusions: These results are significantly better than the best historical results of the Oxford (UCA), performed through an open approach with dislocation of the patella.

Despite impressive overall results at one year, lower knee scores were associated with a surgeons ‘learning curve’. After this ‘learning curve’, increased surgical experience led to further improvement with 90% achieving an excellent result, 8% a good, 2% a fair and 0% a poor result.


Orthopaedic Proceedings
Vol. 85-B, Issue SUPP_I | Pages 55 - 55
1 Jan 2003
Rees JL Beard DJ Price AJ Gill HS Dodd CAF Murray DW
Full Access

Introduction: In conjunction with a bilateral randomised control trial comparing the clinical outcome of two total knee arthroplasties (TKA), we carried out an in-vivo fluoroscopic analysis of both knees in the trial. Knee A, is a new mobile bearing posterior cruciate retaining TKA and Knee B, an established fixed bearing posterior cruciate retaining TKA.

Method: In an ethically approved study, video fluoroscopy was taken of both knees of seven patients performing three exercises; extension against gravity, flexion against gravity and a step up exercise. Ten images at ten-degree intervals over the flexion range were frame grabbed and digitised. The relationship of patella tendon angle (PTA) to knee flexion angle (KFA) was assessed using a newly developed computer system. Five normal knees in fit volunteers were also fluoroscoped and assessed.

Results: A similar pattern of results was obtai ed for all three exercises. Knee A behaved in a linear, more consistent fashion than Knee B, which behaved non-linearly. Analysis of variance showed this difference was significant for all three exercises (p < 0.039).

Conclusions: This bilateral study provides a powerful way of assessing the kinematics of two different knee implants. Knee A behaves in a linear predictable fashion that is nearer normal than Knee B. These results will be used in conjunction with a clinical outcome study and an RSA study to provide a complete assessment of a new TKA.


The Journal of Bone & Joint Surgery British Volume
Vol. 85-B, Issue 1 | Pages 62 - 67
1 Jan 2003
Price AJ Rees JL Beard D Juszczak E Carter S White S de Steiger R Dodd CAF Gibbons M McLardy-Smith P Goodfellow JW Murray DW

Before proceeding to longer-term studies, we have studied the early clinical results of a new mobile-bearing total knee prosthesis in comparison with an established fixed-bearing device. Patients requiring bilateral knee replacement consented to have their operations under one anaesthetic using one of each prosthesis. They also agreed to accept the random choice of knee (right or left) and to remain ignorant as to which side had which implant. Outcomes were measured using the American Knee Society Score (AKSS), the Oxford Knee Score (OKS), and determination of the range of movement and pain scores before and at one year after operation.

Preoperatively, there was no systematic difference between the right and left knees. One patient died in the perioperative period and one mobile-bearing prosthesis required early revision for dislocation of the meniscal component.

At one year the mean AKSS, OKS and pain scores for the new device were slightly better (p < 0.025) than those for the fixed-bearing device. There was no difference in the range of movement.

We believe that this is the first controlled, blinded trial to compare early function of a new knee prosthesis with that of a standard implant. It demonstrates a small but significant clinical advantage for the mobile-bearing design.


Orthopaedic Proceedings
Vol. 85-B, Issue SUPP_I | Pages 52 - 53
1 Jan 2003
Rees JL Price AJ Beard DJ Robinson BJ Dodd CAF Murray DW
Full Access

Introduction: The Oxford medial unicompartmental arthroplasty (UCA) is now routinely performed through a short incision without Dislocation of the patella. The aim of this study was to assess the one-year results of this new technique to determine whether it enhances the quality of outcome, as well as the speed of its achievement.

Method: The first 88 consecutive Oxford UCA’s (Phase 3) implanted into 75 patients by two consultant surgeons were scored pre-operatively and at review with the American Knee Society Score. The average age of the patients was 68.1 years; the male to female ratio was 0.9 to 1.

Results: At review, one patient (one knee) had died and one knee had been revised for infection. The other patients (86 knees) were examined at a mean of 1.3 years from surgery. The average ‘knee score’ improved from 37 points to 95 and the average ‘functional score’ from 51 points to 93. Average maximum flexion improved from 117° to 132°. The ‘knee score’ outcome categories at review were 87% excellent, 8% good, 2.5% fair and 2.5% poor.

Conclusions: Historical comparison of these results with the best results of the Oxford UCA, performed through an open approach with dislocation of the patella, suggest that the minimally invasive approach, in addition to faster recovery, improves the quality of outcome at one year.


Orthopaedic Proceedings
Vol. 84-B, Issue SUPP_II | Pages 156 - 157
1 Jul 2002
Beard DJ Murray DW Rees JL Price AJ Hambly PR Dodd CAF
Full Access

A pilot study was performed to assess the feasibility of discharging patients undergoing unicompartmental knee replacement (UKR) within a day of surgery; both clinical and administrative issues were examined.

Logistics and responsibilities were organised prior to the study. Representatives of anaesthetics, pain team, orthopaedics, admissions, bed management, nursing, theatres, physiotherapy, radiology and outpatients were involved. Patients with medial compartment osteoarthritis undergoing unicompartmental knee replacement who passed strict exclusion criteria were recruited. Factors included; unsuitable home situation (no phone, excessive stairs, no support person), low tolerance to NSAIDS, and not living within a 25 mile radius of the hospital. To date seven NHS patients (mean age 60 years) have been recruited. All patients underwent preoperative assessment and counselling. The mean preoperative Oxford Knee Score was 24/48, the mean Knee Society Score (KSS) was 43/100 and average pain score was 14/50 indicating all patients had significant dysfunction and pain before operation. Average knee flexion was 111° and the average flexion deformity was 5°.

Each patient had a medial UKR using the minimally invasive approach and then underwent the accelerated recovery program. The program included pain control, accelerated rehabilitation, dedicated instructions and self assessment. Post operative pain was controlled by an intra-operative infiltration of local anaesthetic around the knee and large doses of NSAIDs. All patients were mobilised on the day of surgery and all except one who was delayed for administrative reasons) were discharged the following day. Patients were discharged in an extension splint and provided with post operative instructions including an emergency back up telephone number. A designated clinician made regular contact with the patient at home to assess progress. Patients were then assessed in clinic at 6 days, 13 days, and 6 weeks after surgery.

Patients average pain scores at 7 days and 14 days were 2/10 and 2.2/10 respectively. At 6 week follow up the average knee flexion was 124° and average flexion deformity was 1°. All patients were walking independently and painfree. No complications were encountered except one patient required further manipulation for limited knee flexion.

The new pain control protocol permits early mobilisation and discharge for patients undergoing UKR. Potential benefits include increased patient comfort, functional rehabilitation, avoidance of hospital induced infection and substantial cost benefits to the NHS. The pilot study demonstrates that, provided adequate communication is maintained between involved personnel, the program is both practical and safe. It now is planned to implement the accelerated recovery program for UKR as routine.


The Journal of Bone & Joint Surgery British Volume
Vol. 84-B, Issue 5 | Pages 653 - 657
1 Jul 2002
Robinson BJ Rees JL Price AJ Beard DJ Murray DW Smith PM Dodd CAF

When the Oxford unicompartmental meniscal bearing arthroplasty is used in the lateral compartment of the knee, 10% of the bearings dislocate. A radiological review was carried out to establish if dislocation was related to surgical technique.

The postoperative radiographs of 46 lateral unicompartmental arthroplasties were analysed. Five variables which related to the position and alignment of the components were measured. Dislocations occurred in six knees.

Only one of the five variables, the proximal tibial varus angle, had a statistically significant relationship to dislocation. This variable quantifies the height of the lateral joint line. The mean proximal tibial varus angle for knees the bearings of which had dislocated was 9° and for those which had not it was 5°. In both groups it was greater than would be expected in the normal knee (3°).

Our study suggests that a high proximal tibial varus angle is associated with dislocation. The surgical technique should be modified to account for this, with care being taken to avoid damage to or over-distraction of the lateral soft tissues.