Human articular cartilage samples were retrieved from the resected material of patients undergoing total knee replacement. Samples underwent automated controlled freezing at various stages of preparation: as intact articular cartilage discs, as minced articular cartilage, and as chondrocytes immediately after enzymatic isolation from fresh articular cartilage. Cell viability was examined using a LIVE/DEAD assay which provided fluorescent staining. Isolated chondrocytes were then cultured and Alamar blue assay was used for estimation of cell proliferation at days zero, four, seven, 14, 21 and 28 after seeding. The mean percentage viabilities of chondrocytes isolated from group A (fresh, intact articular cartilage disc samples), group B (following cryopreservation and then thawing, after initial isolation from articular cartilage), group C (from minced cryopreserved articular cartilage samples), and group D (from cryopreserved intact articular cartilage disc samples) were 74.7% (95% confidence interval (CI) 73.1 to 76.3), 47.0% (95% CI 43 to 51), 32.0% (95% CI 30.3 to 33.7) and 23.3% (95% CI 22.1 to 24.5), respectively. Isolated chondrocytes from all groups were expanded by the following mean proportions after 28 days of culturing: group A ten times, group B 18 times, group C 106 times, and group D 154 times.

This experiment demonstrated that it is possible to isolate viable chondrocytes from cryopreserved intact human articular cartilage which can then be successfully cultured.

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.

We report a study of 112 patients with primary anteromedial osteoarthritis of the knee and their families. Sibling risk was determined using randomly selected single siblings. Spouses were used as controls. The presence of symptomatic osteoarthritis was determined using an Oxford knee score of ≥ 29 supported by a Kellgren and Lawrence radiological score of II or greater.

Using Fisher’s exact test we found that there was a significant increased risk of anteromedial osteoarthritis (OA) relative to the control group (p = 0.031). The recurrence risk of anteromedial OA to siblings was 3.21 (95% confidence interval 1.12 to 9.27).

These findings imply that genetic factors may play a major role in the development of anteromedial OA of the knee.

The Oxford medial unicompartmental knee replacement was designed to reproduce normal mobility and forces in the knee, but its detailed effect on the patellofemoral joint has not been studied previously. We have examined the effect on patellofemoral mechanics of the knee by simultaneously measuring patellofemoral kinematics and forces in 11 cadaver knee specimens in a supine leg-extension rig. Comparison was made between the intact normal knee and sequential unicompartmental and total knee replacement. Following medial mobile-bearing unicompartmental replacement in 11 knees, patellofemoral kinematics and forces did not change significantly from those in the intact knee across any measured parameter. In contrast, following posterior cruciate ligament retaining total knee replacement in eight knees, there were significant changes in patellofemoral movement and forces.

The Oxford device appears to produce near-normal patellofemoral mechanics, which may partly explain the low incidence of complications with the extensor mechanism associated with clinical use.

Introduction: This study assesses the outcome of medial unicompartmental knee arthroplasty (UKA) using the Oxford prosthesis for end-stage focal spontaneous osteonecrosis of the knee (SONK, Ahlback grades III & IV).

Methods: A total of 29 knees (27 patients) with SONK were assessed using the Oxford Knee Score. Twenty-six had osteonecrosis of the medial femoral condyle; 3 had osteonecrosis of the medial tibial plateau. This group was compared to a similar group who had undergone Oxford Medial UKA for primary osteoarthritis. Patients were matched for age, sex and time since operation.

Results: Mean length of follow-up was 5.2 years (range 1–13 years). There were no implant failures in either group, but there was one death 9 months post-arthroplasty from unrelated causes in the group with osteonecrosis. The mean Oxford Knee Score in the group with osteonecrosis was 37.8 (± 7.6) and 40.0 (± 6.6) in the group with osteoarthritis. There was no significant difference between the two groups using Student’s t-test (p=0.31).

Interpretation: Use of the Oxford Medial UKA for focal spontaneous osteonecrosis of the knee is reliable in the short to medium term, and gives similar results to when used for patients with primary osteoarthritis.

Polyethylene particulate wear debris continues to be implicated in the aetiology of aseptic loosening following knee arthroplasty. The Oxford unicompartmental knee arthroplasty employs a spherical femoral component and a fully congruous meniscal bearing to increase contact area and theoretically reduce the potential for polyethylene wear. This study measures the in vivo ten-year linear wear of the device, using a roentgenstereophotogrammetric technique.

In this in vivo study, seven medial Oxford unicompartmental prostheses, which had been implanted ten years previously were studied. Stereo pairs of radiographs were acquired for each patient and the films were analysed using a roentgen stereophotogrammetric analysis calibration and a computer-aided design model silhouette-fitting technique. Penetration of the femoral component into the original volume of the bearing was our estimate of linear wear. In addition, eight control patients were examined less than three weeks post-insertion of an Oxford prosthesis, where no wear would be expected. The control group showed no measured wear and suggested a system accuracy of 0.1 mm. At ten years, the mean linear wear rate was 0.02 mm/year.

The results from this in vivo study confirm that the device has low ten-year linear wear in clinical practice. This may offer the device a survival advantage in the long term.

We present a comparison of the results of the Oxford unicompartmental knee arthroplasty in patients younger and older than 60 years of age. The ten-year all-cause survival of the < 60 years of age group (52) was 91% (95% confidence interval (CI) 12), while in the ≥ 60 years of age group (512), the figure was 96% (95% CI 3). For the younger group, the mean Hospital for Special Surgery score at ten-year follow-up (n = 21) was 94 of 100, compared with a mean of 86 of 100 for the older group (n = 135). The results show that the Oxford unicompartmental arthroplasty can achieve ten-year results that are comparable to total knee arthroplasty in patients < 60 years of age. We conclude that for patients aged over 50, age should not be considered a contraindication for this procedure.

Replacement of the shoulder in juvenile idiopathic arthritis is not often performed and there have been no published series to date.

We present nine glenohumeral hemiarthroplasties in eight patients with systemic or polyarticular juvenile idiopathic arthritis. The mean follow-up was six years (59 to 89 months). The mean age at the time of surgery was 32 years. Surgery took place at a mean of 27 years after diagnosis. The results indicated excellent relief from pain. There was restoration of useful function which deteriorated with time, in part because of progression of the systemic disease in this severely affected group. No patient has required revision to date and there has been no radiological evidence of loosening or osteolysis around the implants.

We discuss the pathoanatomical challenges unique to this group. There was very little space for a prosthetic joint and, in some cases, bony deformity and the small size necessitated the use of custom-made implants.

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.

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.

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.

The purpose of this study was to establish the long-term clinical outcome of the Oxford Medial Unicompartmental Knee Arthroplasty (UKA).

Methods: A continuous series of 420 patients underwent medial Oxford UKA. Indications were anteromedial osteoarthritis with full thickness lateral compartment cartilage, a functioning anterior cruciate ligament and correctable varus deformity. Survival analysis with all cause revision as the endpoint was carried out for the entire group. At the time of this study 121 were still alive at 10 years and pre/post-operative 10-year clinical data had been prospectively recorded for them from which the AKS and HSS scores were calculated. Results: Seventeen patients required revision (4%) and the fifteen year survival rate was 94.3% (95% CI 85.6 - 100%). At ten years AKS and HSS scores were: AKSS (Knee) pre 30 / post 90, AKSS (Function): pre 42/ post 69 and HSS pre 56/ post 86. The differences were statistically significant (p< 0.01).

Discussion and Conclusion: We conclude that providing careful patient selection is maintained, meniscal bearing medial unicompartmental knee arthroplasty has clinical and survival results comparable to modern total knee arthroplasty. The advantages of lower morbidity and earlier return to function, enhanced by the introduction of minimally invasive techniques may make this the treatment of choice for suitable patients with anteromedial osteoarthritis of the knee.

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.

Aim: This study was designed to investigate the nature and extent of tibial translation (TT) during open kinetic chain (OKC) and closed kinetic chain (CKC) activity; recent reports have suggested that the anterior cruciate ligament (ACL) may be strained to an equal amount during CKC and OKC exercise.

Method: Fifteen unilaterally ACL deficient (ACLD) patients and six control subjects underwent fluoroscopic assessment while performing a passive extension exercise, an OKC resisted extension exercise, and a weight-bearing CKC exercise designed to reflect knee motion experienced during dynamic daily activity. Measurements of the patella tendon angle (the angle between the long axis of the tibia and the patella tendon) were obtained to calculate relative TT.

Results: The results show that in ACL intact (ACLI) knees the CKC exercise caused greater anterior TT than the OKC exercise from 0 to 60° of knee flexion (p< 0.05). No difference between ACLI and ACLD knees was detected during the CKC exercise. Maximum weight-bearing (CKC) TT was 8±3 mm. The ACLD tibia during the OKC exercise translated more than the ACLI tibia, and to the same extent as the CKC exercise at 10 to 200 of knee flexion. The ACLI tibia during OKC exercise translated to a maximum of 3±4 mm at 1 0° knee flexion.

Summary: This study has demonstrated that fluoroscopic analysis may be used to detect differences in the kinematics of ACLI and ACLD limbs during activity. It validates recent data demonstrating that the ACL may be strained during CKC exercise to an equal or greater amount than during OKC exercise, and shows that the ACLD knee kinematics are similar to the ACLI knee during CKC exercise. Factors other than the ACL may control the extent of maximal TT during weightbearing activity. This has important consequences for the development of rehabilitation regimes after ACL reconstruction. The commonly held assumption that CKC exercise will protect an ACL graft may not be valid.

Purpose: As part of the step-wise introduction of a meniscal-bearing total knee replacement (Oxford TMK) we needed to know, before proceeding to longer term studies, whether its early clinical results were at least as good as those of an established fixed bearing device (AGC).

Material and Methods: With ethical approval, patients requiring bilateral knee replacement for osteoarthritis consented to have the operations under one anaesthetic using one of each prosthesis; to accept random choice of knee; and to remain ignorant which side was which. American Knee Society Scores, Oxford Knee Scores, ROM and pain scores were to be recorded preoperatively and at one year. By January 2001, 40 patients had reached one year and data is available for 36.

Results: Preoperatively there was no difference between the two knees. One patient died in the peri-operative period.

Results at one year (TMK first): AKSS(Knee) 91.6 / 84.1 (p=0.003), OKS 39.8 / 37.6 (p=0.006), ROM 104 / 104 (p=0.364), Pain (AKSS) 47.3 / 41.7 (p=0.01), Pain (OKS) 3.5 / 2.9 (p=0.006).

Conclusion: The TMK performed as well as the AGC. Its AKSS, OKS and pain scores were significantly better. We believe this controlled, blinded trial is the first to have compared the function of a new knee prosthesis with a standard implant before marketing; and the first to have demonstrated a significant clinical advantage for a meniscal-bearing over a fixed bearing TKR. The comparison of bilateral implants in the same patient can reveal significant differences while putting at risk many fewer subjects than would be needed for a classical twocohort RCT.

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.

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.

We have assessed the effectiveness of reconstruction of the anterior cruciate ligament (ACL) in reducing functional tibial translation (TT).

The gait of 11 ACL-deficient patients was studied using Vicon equipment before and after surgery. Measurements of the angle between the patellar tendon and the long axis of the tibia were obtained in order to calculate TT in the sagittal plane relative to the uninjured limb during standing and walking.

Before surgery, patients did not show abnormal TT on the injured side, but after surgery significant anterior TT was found in the operated limb for every parameter of gait.

Abnormal anterior TT occurring during activity does not seem to be reduced by reconstruction; rather, it increases. It may be that the increased translation results from relaxation of excess contraction of the hamstring muscles, since compensatory muscle activity no longer is required in a reconstructed knee. The reduction of TT may not be an appropriate objective in surgery on the ACL.

Satisfactory selection criteria are essential for the successful outcome of unicompartmental knee arthroplasty (UCA). We report the frequency of revision of the Oxford medial unicompartmental arthroplasty in knees previously treated for anteromedial osteoarthritis by high tibial osteotomy (HTO). The combined results from three sources were used to allow statistical analysis of this uncommon subgroup.

In the combined series of 631 knees (507 patients) which had medial unicompartmental replacement, 613 were primary procedures and 18 were for a failed HTO. The mean follow-up times of the two groups were similar (5.8 years and 5.4 years, respectively). At review, 19 (3.1%) of the primary procedures and five (27.8%) of those undertaken for a failed HTO had been revised to total knee replacement. Survival analysis revealed the ten-year cumulative survivals to be 96% and 66%, respectively. The log-rank comparison of these survivals revealed a highly significant difference (p < 0.0001).

We recommend that the Oxford UCA should not be used in knees which have previously undergone an HTO.

We describe the outcome of a series of 124 Oxford meniscal-bearing unicompartmental arthroplasties carried out for osteoarthritis of the medial compartment. They had been undertaken more than ten years ago in a non-teaching hospital in Sweden by three surgeons. All the knees had an intact anterior cruciate ligament, a correctable varus deformity and full-thickness cartilage in the lateral compartment. Thirty-seven patients had died; the mean time since operation for the remainder was 12.5 years (10.1 to 15.6).

Using the endpoint of revision for any cause, the outcome for every knee was established. Six had been revised (4.8%). At ten years there were 94 knees still at risk and the cumulative survival rate was 95.0% (95% confidence interval 90.8 to 99.3). This figure is similar to that reported by the designers of the prosthesis and to the best published results for independent series of total knee replacement. If patients are selected appropriately, this implant is a reliable treatment for anteromedial osteoarthritis of the knee.