We inserted an electrode up the femoral neck into the femoral head of ten patients undergoing a metal-on-metal hip resurfacing arthroplasty through a posterior surgical approach and measured the oxygen concentration during the operation. In every patient the blood flow was compromised during surgery, but the extent varied. In three patients, the oxygen concentration was zero at the end of the procedure. The surgical approach caused a mean 60% drop (p < 0.005) in oxygen concentration while component insertion led to a further 20% drop (p < 0.04). The oxygen concentration did not improve significantly on wound closure. This study demonstrates that during hip resurfacing arthroplasty, patients experience some compromise to their femoral head blood supply and some have complete disruption.

Abnormal sagittal kinematics after total knee replacement (TKR) can adversely affect functional outcome. Two important determinants of knee kinematics are component geometry and the presence or absence of a posterior-stabilising mechanism (cam-post). We investigated the influence of these variables by comparing the kinematics of a TKR with a polyradial femur with a single radius design, both with and without a cam-post mechanism.

We assessed 55 patients, subdivided into four groups, who had undergone a TKR one year earlier by using an established fluoroscopy protocol in order to examine their kinematics in vivo. The kinematic profile was obtained by measuring the patellar tendon angle through the functional knee flexion range (0° to 90°) and the results compared with 14 normal knees. All designs of TKR had abnormal sagittal kinematics compared with the normal knee. There was a significant (p < 0.05) difference between those of the two TKRs near to full extension. The presence of the cam-post mechanism did not influence the kinematics for either TKR design. These differences suggest that surface geometry is a stronger determinant of kinematics than the presence or absence of a cam-post mechanism for these two designs. This may be because the cam-post mechanism is ineffective.

Polished, tapered stems are now widely used for cemented total hip replacement and many such designs have been introduced. However, a change in stem geometry may have a profound influence on stability. Stems with a wide, rectangular proximal section may be more stable than those which are narrower proximally. We examined the influence of proximal geometry on stability by comparing the two-year migration of the Exeter stem with a more recent design, the CPS-Plus, which has a wider shoulder and a more rectangular cross-section. The hypothesis was that these design features would increase rotational stability.

Both stems subsided approximately 1 mm relative to the femur during the first two years after implantation. The Exeter stem was found to rotate into valgus (mean 0.2°, sd 0.42°) and internally rotate (mean 1.28°, sd 0.99°). The CPS-Plus showed no significant valgus rotation (mean 0.2°, sd 0.42°) or internal rotation (mean −0.03°, sd 0.75°). A wider, more rectangular cross-section improves rotational stability and may have a better long-term outcome.

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.

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.

A randomised controlled trial was performed to compare the clinical outcome for the two commonest types of anterior cruciate ligament (ACL) reconstruction. Methods: Patients undergoing elective anterior cruciate reconstruction were randomised into one of two groups. Group PT underwent reconstruction using a patella tendon autograft (n=14), whereas Group SG had a semitendinosus/gracilis autograft (n=18). The same surgeon performed all operations. IKDC self reported function and activity scores were recorded pre-operatively and at one and five years post operation. KT1000 values and muscle strength were recorded pre-operatively and one year post operation.

Results: No significant difference between groups was found for any measurement at one year despite adequate study power. At five year follow up patients in the PT group had superior scores in every category of the IKDC self reported function score (mean IKDC score for PT group = 83, mean IKDC score for SG = 75). The activities of squatting and kneeling revealed the greatest difference between groups. It was found that 71% of patients in the PT group achieved IKDC scores of 80 or over whereas only 61% of patients in the SG group achieved 1 KDC scores of 80 or over.

Conclusion: The study indicates that both techniques produce acceptable outcome for anterior cruciate ligament reconstruction but use of the patella tendon autograft may provide slightly more favourable results, especially for activities involving squatting and kneeling.

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.

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.