Patellofemoral pain is a significant problem for patients with Total Knee Replacements (TKRs). It is hypothesized that pain is related to high patellofemoral forces (PFF). The aim of this study is to validate a model to estimate PFF after TKR, using a combination of non-invasive measurement and theoretical modeling.

Experiments were performed on four cadaver knee specimens to compare the PFF and the quadriceps force (QF) estimated by a model, with those measured using force transducers. Each knee was tested in its initial state and after implantation of three Scorpio designs: Cruciate Retaining (CR), Posterior Stabilised (PS), and the Posterior Stabilised Mobile Bearing (PS+). Each knee was extended/flexed under a simulated quadriceps load with 3 kg hung from the distal tibia. Relative movement of the bones was measured using a Vicon 612 motion analysis system. A 6DOF force transducer was used to measure PFFs and a uni-axial transducer was used to measure QFs. A fluoroscope simultaneously captured images of the leg extension activity. Parameters measured from the images were used as inputs to the model.

The measured and estimated PFF and QF matched closely between 20o and 80o of knee flexion for the TKRs. At higher flexion angles, the model overestimated the PFF by a maximum of 23N (7.6% max) for the PFF and by 31N for the QF (10.3% max). The estimated and measured Patellar Flexion Angles (PFA) were within 3.5o throughout the flexion range.

The model accurately predicts sagittal plane patellar kinematics and kinetics, using only fluoroscopy and externally measured forces as inputs. However, the model has a limitation in assuming that the extending moment is only due to the quadriceps.

Award for the best student biomaterials paper (US$ 2,000); a proper certificate

Oxford Unicompartmental knee arthroplasty (UKA) is now performed using a minimally invasive surgical (MIS) technique. Although early results are encouraging, the studies assessing outcome could be criticised for the restricted number of patients and limited follow-up. Aim of this study was to assess clinical outcome and prosthetic survival rate inpatients with minimally invasive Oxford medial UKA.

This prospective study assessed 500 consecutive patients, who underwent cemented Oxford UKA for medial OA using MIS technique. Patients were assessed using objective and functional Knee Society Score (KSS).

This study has confirmed preliminary findings that Oxford UKA using a minimally invasive approach is safe, reliable and effective.

Aim: To investigate the functional and radiological outcome of shelf acetabuloplasty in adults with significantly symptomatic acetabular dysplasia, with a minimum of a 5 year follow-up.

Material and Methods: 77 consecutive shelf procedures (68 patients) with an average follow-up of 10.9 years (range: 6–14) were reviewed. The Oxford hip score (OHS) was used for clinical assessment. Centre-edge angle (CEA) and acetabular angle (AA) were measured as indicators of joint containment. The severity of osteoarthiritis was based primarily on the extent of joint space narrowing. Survivorship analyses using conversion to THR as an endpoint were performed. Logrank tests were used to compare the survivorship of the shelf procedure against the variables of age, preoperative osteoarthiritis, pre and postoperative AA, CEA angles.

Results: The average age at time of surgery was 33 years (range: 17–60). At the time of the last follow-up, the mean OHS was 34.6 (maximum score: 48). Mean postoperative CEA was 55 (Pre-operatively: 13 degrees) while mean postoperative AA was 31 (Pre-operatively: 48 degrees). Thirty percent of hips needed THR at an average duration of 7.3 years. The survival in the 45 patients with only slight or no joint space narrowing was 97% (CI, 93%–100%) at 5 years and 80% (CI, 56%–100%) at 10 years. This was significantly higher (p= 0.0007) than the survival in the 32 patients with moderate or severe osteoarthiritis, which was 72% (CI, 55%–89%) at 5 years and 29% (CI, 13%–45%) at 10 years. There was no significant relationship between survival and age, pre and postoperative AA, CEA angles (p> 0.05).

Conclusion: Shelf-acetabuloplasty offers symptomatic relief to adults with acetabular dysplasia but overall deteriorates with time. About 50% of the patients do not need THR for over 10 years. Best results with shelf-acetabuloplasty were achieved in patients with slight or no joint narrowing.

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.

Aims: The purpose of this study is to determine the causes of failed medial Oxford unicompartmental knee arthroplasty (UKA) and assess the outcome after revision surgery.

Materials And Methods: From 1993 to 2003, sixty-nine Oxford UKA (58 patients) were revised to a total knee replacements (TKR) at this centre. The type of implant used at revision surgery, pre- and post-revision American Knee Society (AKS) and Tegner scores were analyzed retrospectively.

Results: The patient’s mean age at the time of UKA was 64.5 years (range: 50–79). The average pre-revision scores were as follows: AKS-Objective score was 41.2 (± 10.4), the AKS-functional score was 56.8 (±10.0) and the average Tegner score was 1.5 (±0.6). The mean follow-up period was 38.3 (range: 12–107) months. The common causes of failure were: lateral compartment osteoarthritis (34.0%), component loosening (30.4%) and early or late infection requiring two-stage revision surgery (14.3%). The majority were revised using a standard primary TKR implant and only six (9%) requiring augmentation stems. Patellar resurfacing was performed in 25% of cases. The mean polyethylene liner width of the revision TKR was 13.4mm (±3.7). The average post-revision scores were: AKS-Objective score 77.4 (±13.1), the AKS-functional AKS score 70 (±21.1) and the average Tegner score of 2.2 (±0.8). Three knees needed rerevision for infection of the revised implant.

Conclusions: Lateral compartment osteoarthritis was the commonest indication for revision surgery for a failed medial Oxford UKA. Revision of a UKA is technically easier and the results are superior to the published results of revision of a primary TKR. In more than 90% cases, no augmentation or stemmed implants were necessary.

Introduction: The indications for medial unicompartmental knee arthroplasty (UKA) remain controversial; in particular, those relating to the state of the patello-femoral joint (PFJ). Some authorities consider the presence of anterior knee pain (AKP) and/or full thickness cartilage loss (FTCL) to be a contraindication. The aim of this study was to determine the influence of patello-femoral problems on the outcome of medial UKA.

Materials and Methods: This prospective study involved one hundred knees with cemented medial Oxford UKA (phase 3), via a minimally invasive approach. Pre-operatively presence or absence of AKP was noted. The cartilage status of medial and lateral patello-femoral joint was grade and recorded intra-operatively. Outcome was evaluated at one-year with the Knee Society Score and the Oxford Knee Score (OKS).

Results: 54% of patients had pre-operative AKP. The clinical outcome at one year was not dependent on the presence or absence of pre-operative AKP [OKS: 40.2 (± 8.2) for patients without pre-op. AKP and OKS: 40.8 ((± 6.8) for patients with pre-operative AKP]. 35% of patients had FTCL seen at operation in the PFJ. The outcome at one year was independent of the state of the medial and/or lateral PFJ [OKS = 40.7 (± 7) with normal or partial thickness cartilage loss and OKS = 39.8 (± 7) with full thickness cartilage loss in PFJ]

Conclusions: These short-term results suggest that for the Oxford UKA the presence of anterior knee pain or full thickness cartilage damage in patello-femoral joint should not be considered to be a contraindication.

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 (SD) 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=0.29).

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.

Introduction: With a minimally invasive approach for unicompartmental knee replacement (UKA), it is difficult to determine the femoral component size intra-operatively. It can be difficult to template pre-operative radiographs due to superimposition of the two femoral condyles, and non-standardised x-ray magnification.

Aim: The purpose of the study was to find an easy, reliable, alternative method for this assessment such as height and gender.

Material and methods: One hundred x-rays of patients (44 men, 56 women), who had undergone Oxford UKR, were reviewed. Preoperative radiographs were templated, and postoperative x-rays were reviewed to determine the ideal component size. Patient’s height was recorded. The proportion of patients for whom an appropriate size could be selected by either template or height measurements was calculated.

Results: Current templating system accurately predicted the ideal size in 67 patients. The following size bands were set according to height. For men: size small in patients less than160 cm, medium less than 170 cm and large less than 180 cm. For women: size small in patients less than 164 cm, medium less than 174 cm and large less than 184 cm. Height accurately predicted the ideal size in 75 patients. In no case was the assessment of component size incorrect by more than one size.

Conclusion: Gender specific height safely predicted the ideal component size in 75 percent of patients undergoing UKA. Component size can be determined satisfactorily from patient height and gender and can be used as adjunct to existing templating method.

Introduction: The indications for unicompartmental knee arthroplasty (UKA) remain controversial; in particular, the threshold of disease in the patellofemoral compartment is debated. Whilst some authorities ignore the condition of the patellofemoral joint, others consider pre-existing patellofemoral osteoarthritis (PFOA) a contraindication to UKA. The aim of this study was to determine the influence of PFOA on the outcome of medial UKA.

Methodology: This prospective study involved one hundred consecutive patients who had undergone cemented medial Oxford UKA (phase 3), via a minimally invasive approach, at least one year previously. Patients were divided into two groups according to the presence or absence of full thickness cartilage loss (FTCL) on the patella or trochlea at operation. Outcome was evaluated with the Knee Society Score (AKSS) and the Oxford Knee Score (OKS, maximum 48). Groups were compared for differences in knee score and intra-operative cartilage status of PFJ using a one way ANOVA. Repeat analysis was performed using the presence of anterior knee pain (AKP) as the group defining variable.

Results: There were 35 patients with FTCL and 65 without. Both groups were well matched for age, gender and activity levels. No significant difference in post operative knee scores existed between groups for the pre-operative presence of FTCL (OKS = 40 in both groups). Similar, non significant, results were found when the pre-operative presence of AKP was used as a group defining factor (OKS 40 Vs 39). The study was sufficiently powered to avoid type II error.

Conclusion: Intra-operative evidence of PFOA in patients with medial compartment osteoarthritis does not prejudice the outcome of UKA at one year. Moreover, the inclusion of patients with symptomatic AKP (with or without concurrent PFOA) also appears not to influence the outcome after UKA.

Introduction: Total knee replacement (TKR) is a common treatment for end stage osteoarthritis of knee. The best knee replacement is one in which the kinematics of the normal knee are reproduced. Amongst several factors affecting kinematics, variation in surface geometry and the retention/ sacrifice of the PCL are considered especially important. It is not known which of these two factors is most influential for establishing optimum joint kinematics after TKR.

Method: Four groups of patients who had undergone TKR at least one year previously were recruited. Two groups of patients had undergone replacement with a single axis design (Scorpio, Stryker Howmedica) in both PCL retaining (Scorpio CR, n=15) and PCL sacrificing (Scorpio CS, n=15) variants. The other two groups had undergone replacement with the traditional polyradial design prosthesis (Sigma, Depuy, Johnson & Johnson), again with both PCL retaining (Sigma CR, n=14) and PCL sacrificing (Sigma CS, n=13) variants. An in-vivo fluoroscopic analysis was carried out on all patients. Patients were asked to perform closed chain step up and open chain extension and flexion against gravity. The kinematic profile of each knee was obtained by measuring patella tendon angle (PTA) at specific angles of knee flexion (KFA) using an established fluoroscopic method. The data was also compared with the kinematic profile of normal knees. American Knee Society, Oxford and Patella Scores were recorded for all patients.

Results: All groups were comparable in terms of age and gender. In addition, no significant difference was found between groups in clinical outcome. PTA results for a step-up exercise are shown in the figure. A one way ANOVA between groups revealed that knee kinematics after total knee replacement is different to that for normal knees. No differences were found between groups when the data was analysed using CR/CS as the independent variable. The only differences between groups were found when surface geometry was used as the independent variable. It was shown that the kinematic profile of the single axis Scorpio design (in both CR & CS ) was closer to normal, especially near extension, than the traditional polyradial design (Sigma CR & CS).

Conclusions: Kinematics after a total knee replacement differ from that for a normal knee. Differences in surface design between knee replacements appear to have greater influence on kinematics than the presence or absence of the PCL.

Introduction: Unicompartmental knee arthroplasty (UKA) is an increasingly popular procedure for young osteoarthritic patients whose age and activity levels preclude the use of a total knee arthroplasty (TKA). However, successful reconstruction using an unconstrained mobile bearing implant requires an intact and functioning ACL. Patients with isolated medial compartment OA and an absent ACL therefore provide a management dilemma for the treating surgeon. One option is to perform a combined ACL reconstruction and mobile bearing UKA. This paper presents early results of this new procedure using an Oxford UKA and ACL reconstruction using an autograft.

Materials and Methods: Eleven patients who underwent one or two-staged ACL reconstruction and Oxford UKA for treatment of symptomatic medial compartment OA were reviewed at one year after surgery. The combined procedure required specific precautions and considerations; care had to be taken to place the tibial tunnel as far laterally as possible to avoid impingement of the graft by the tibial implant. Also, the presence of a posteromedial, rather than an anteromedial cartilage defect has the potential to reduce accuracy for placement of the initial tibial cut.

Results: All patients were male with an average age of 49 years (range: 36 – 52) and mean follow up of 1.3 years. One patient needed revision to TKA due to infection. The objective and functional knee society scores improved pre to post operatively from 55 to 98, and 85 to 100, respectively.

Conclusions: ACL reconstruction and simultaneous or staged UKA is a viable treatment option for patients with symptomatic medial compartment arthritis in whom the ACL is absent. Early results of this technically demanding procedure are encouraging but longer follow-up is required.

Introduction and Aims A randomised controlled trial (RCT) and a multi-centre unilateral cohort study were performed as part of the stepwise introduction of a new mobile bearing knee. The aim was to ensure that outcome for the new device was at least as good as that for an established fixed bearing device. This paper presents three year follow up of the published one year results. Instability and prevalence of “clicking” from the joint were examined in detail.

Method 1. A multi-centre RCT of patients undergoing bilateral knee replacement compared functional outcome between two different prostheses, the new mobile bearing device (TMK) and an established fixed bearing device (AGC). 2. A separate multi-centre cohort of 166 patients who had undergone a unilateral mobile bearing procedure at least six months previously was used to assess complication rate and corroborate any findings from the bilateral trial. Outcome measures included Oxford Knee Scores, American Knee Society ratings and complication rate.

Results The bilateral trial revealed no significant differences in outcome between the two devices. Revision rate for all (199) mobile bearing knees was less than 2%. The mean Oxford Knee Score for outcome for all mobile bearing knees was 37.1 ± 10.1. About 7% of patients reported instability. Clicking was more common in the TMK (48%) than in the AGC (30%) and was reported as a problem in 16% of TMK’s in the cohort study. However, clicking was unrelated to outcome score in both studies.

Conclusion At three years, the mobile bearing device was as good as the fixed bearing device. There was a relatively high prevalence of “clicking” in the TMK but the cause remains unclear. Furthermore, the symptom was not associated with poor functional outcome. The bilateral RCT and cohort study allows assessment of function and potential problems. It provides rigourous scientific justification for the introduction and early assessment of new implants.

Aim: To investigate the functional and radiological outcome of shelf acetabuloplasty in adults with significantly symptomatic acetabular dysplasia, with a minimum of a 5 year follow-up.

Material and Methods: 77 consecutive shelf procedures (68 patients) with an average follow-up of 10.9 years (range: 6–17) were reviewed. The Oxford hip score (OHS) was used for clinical assessment. Centre-edge angle (CEA) and acetabular angle (AA) were measured as indicators of joint containment. The severity of osteoarthiritis was based primarily on the extent of joint space narrowing. Survivorship analyses using conversion to THR as an endpoint were performed. Logrank tests were used to compare the survivorship of the shelf procedure against the variables of age, preoperative osteoarthiritis, pre and postoperative AA, CEA angles.

Results: The average age at time of surgery was 33 years (range: 17–60). At the time of the last follow-up, the mean OHS was 34.6 (maximum score: 48). Mean postoperative CEA was 55 (Pre-operatively: 13 degrees) while mean postoperative AA was 31 (Pre-operatively: 48 degrees). Thirty percent of hips needed THR at an average duration of 7.3 years. The survival in the 45 patients with only slight or no joint space narrowing was 97% (CI, 93%-100%) at 5 years and 75% (CI, 51%-100%) at 10 years. This was significantly higher (p≤= 0.0007) than the survival in the 32 patients with moderate or severe osteoarthiritis, which was 76% (CI, 55%-89%) at 5 years and 22% (CI, 5%-38%) at 10 years. There was no significant relationship between survival and age, pre and postoperative AA, CEA angles (p> 0.05).

Conclusion: Shelf-acetabuloplasty offers symptomatic relief to adults with acetabular dysplasia but overall deteriorates with time. About 50% of the patients do not need THR for over 10 years. Best results with shelf-acetabuloplasty were achieved in patients with slight or no joint narrowing.

Purpose of the study: To evaluate the clinical outcome of revision total hip arthroplasty (THA) using the Oxford Hip prosthesis combined with impaction allografting. Methods and results: The Oxford hip is a trimodular prosthesis with a polished tapered metaphyseal section that is free to slide on the stem. The stem is inserted uncemented into the diaphysis, bone graft is impacted proximally, with mesh if necessary, and then the proximal wedge is cemented in.

Between 1999 and 2002, we revised 72 hips in 69 patients using this technique (mean age 65years, 28 to 88). Fifty-six cases had aseptic loosening, 8 had infection (2 stages), 7 had peri-prosthetic fractures and 1 had a broken stem. The mean time to revision was 8.5years (1 to 21). Patients were assessed clinically and with the Oxford Hip Score (OHS) pre- and post-operatively. Fifty-seven patients also had acetabular revision. Four patients required femoral osteotomy to remove the old prosthesis. We used a mean of 1.8 (1 to 4) femoral heads per operation.

Complications included 6 peri-operative femoral fractures diagnosed at operation and fixed successfully, 6 infections, 10 dislocations (2 were recurrent), one deep vein thrombosis, 2 pulmonary embolism and one gastrointestinal haemorrhage. The average blood transfusion was 1.8 units (0 to 9).

The OHS improved from 45 (26 to 58) pre-operatively to 24.3 post-operatively (12 to 43). No hip has been re-revised for aseptic loosening at a mean follow-up of 32.7 months (16 to 51).

Conclusion: Although we accept that this is only a preliminary experience, we believe that the use of the trimodular Oxford stem combined with minimal proximal impaction allografting was found to be a reliable method and a successful way of dealing with revision femoral surgery. The results were comparable with a primary arthroplasty in terms of pain relief and functional results

Introduction: The aim of this study was to compare two methods of femoral fixation for four strand Hamstring (4SH) primary ACL reconstruction: namely a recently introduced suspensory fixation using absorbable polylactic acid cross pins versus our traditional method of anchor fixation.

Method: Forty-five consecutive patients, who had undergone primary ACL reconstruction using 4SH graft and the suspensory femoral fixation were prospectively evaluated by an independent observer. IKDC scores were recorded and laxity was assessed using cruciometer. These results were compared with a similar well-matched cohort of patients whose femoral fixation was with an anchor. Tibial fixation in both the groups was similar.

Results: No significant difference was noted between the two groups on comparison of IKDC scores or cruciometer readings at a minimum one-year follow-up.

Conclusions: This suspensory method of femoral fixation for a four-strand hamstring graft provided a secure fixation with satisfactory early clinical results. As this method of fixation is a new technique, further follow-up is needed for long-term validation.

Aim: To compare the kinematic profile of two types of TKRs – a single-axis design Vs a polyradial design, with that of the normal knee.

Methodology: An in-vivo fluoroscopic analysis was carried out as part of a four-armed prospective randomised trial comparing the clinical outcome of two commonly used types of TKRs each with posterior cruciate retaining -CR and sacrificing –CS models. The kinematic profile was obtained by measuring patella tendon angle at specific angles of knee flexion using an established fluoroscopic method whilst the patients performed close and open chain exercises. The data was compared with the kinematic profile of the normal knee.

Results: Fifty-five patients who had undergone TKR at least one year prior, were invited to take part in this ethically approved study. They were matched for age and gender and had a similar clinical outcome.

The kinematic profile of single axis design TKR was closer to normal especially near extension. During mid-flexion, abnormal anterior femoral translation was noticed with the polyradial design. No significant difference was noted between CR and CS designs.

Conclusions: Kinematics after a TKR differed from that of a normal knee. Reproducible differences were found between the two designs, which may predict mode of failure and longevity.

Introduction: Oxford Unicompartmental knee arthroplasty (UKA) is now performed using a minimally invasive surgical (MIS) technique. Although early results are encouraging, the studies assessing outcome could be criticised for the restricted number of patients and centres involved. A multi-centre follow-up of patients is required to confirm the preliminary findings.

Aim: To examine early clinical outcome in patients with minimally invasive Oxford medial UKA using a multi-centre, multi-surgeon design.

Materials and Methods: This prospective study was carried out in three centres with involvement of six surgeons. All patients undergoing cemented Oxford UKA for medial OA using MIS were included. 231 consecutive UKAs with a minimum follow up of 2 years (mean: 2.84) were assessed using objective and functional Knee Society Score (KSS).

Results: There were 108 females and 102 males (21-bilateral) with average age of 66.8 years (42 – 86). No significant difference was noted between various age groups or between different surgeons. Three knees were revised: one for infection, one for unexplained pain and one for bearing dislocation. Cumulative survival rate at 2 years was 98.6% with 93% patients having good or excellent KSS rating.

Conclusions: This multi-centre study has confirmed preliminary findings that Oxford UKA using a minimally invasive approach is safe and effective.

Aim: To study the sagittal plane kinematics of the Avon patello-femoral replacement (Stryker-Howmedica), PTA.

Introduction: Replacement of the patello-femoral joint for end stage osteoarthritis has previously been associated with inconsistent results. Retention of the cruciate ligaments is likely to be important in maintaining normal kinematics and hence improved functional outcome.

Methodology: Twelve patients who had undergone Avon PFR least two years previously were recruited following ethical approval. American Knee Society, Bristol and Oxford knee scores were obtained. Patients performed open chain flexion and extension against gravity, in addition to closed chain step up. Video fluoroscopy of these activities was used to obtain the Patellar Tendon Angle (PTA), which is the angle between the long axis of the tibia and the patella tendon, at specific angles of knee flexion. This is a previously validated method of assessing the kinematic profile of a knee joint. These measurements were used to determine the kinematic profile of each knee and they were then compared to a group of twelve normal knees.

Results: A one way ANOVA revealed no significant differences between the kinematic profile following Avon PFR and that of the normal knee. All patients had good or excellent knee scores.

Conclusion: The kinematic profile after Avon PFR is similar to that of the normal knee. In contrast all TKRs we have studied have abnormal kinematics, which are associated with abnormal patello-femoral joint loading. This suggests that isolated PFR should have a functional advantage over TKR.

Introduction: Number of patients needing revision ACL surgery has increased more than 10 fold. Results of revision surgery are traditionally thought to be inferior to primary reconstruction. Aim of this paper is to describe results of revision surgery using a two-stage technique and compare it with results of primary ACL reconstruction. Materials and Methods: We studied 44 consecutive patients with revision ACL surgery. They had 10 ACL reconstruction elsewhere using autologous (34) or prosthetic ligament (10). Rrevision surgery was two staged. First of debridement and bone grafting and second stage after 3 mths of meniscal and chondral work along with ACL reconstruction using autograft. We compared this group with a similar cohort of patients with primary ACL surgery. Conclusions: A two-stage revision technique for revision ACL surgery allows accurate assessment & opportunity for the bone graft to heal to provide good bed for graft fixation at the time of second procedure.

Introduction: Radiolucencies are frequently observed around joint replacements. Their signiþcance & etiology remain unclear. Aim: 1. To study radiolucency under tibial tray of Oxford UKA and correlate it to the clinical outcome. 2. To study implant migration using RSA and study the correlation between migration and radiolucency. Materials and Methods: Fifty consecutive patients cemented Oxford UKA with a minimum follow up of two years were studied. At 2 years precisely aligned radiographs were obtained and evaluated for presence and extent of radiolucency under the tibial tray. The patients were divided into two groups Ð those with (Group I) and those without presence of radiolucency under the tibial tray (Group II). All the patients were assessed using KSS. Patients had RSA marker balls inserted around the prosthesis at the time of index procedure. Using RSA, the degree and direction of implant movement was measured at 1 & 2 yrs post surgery. Results: A) There were 26 patients in group I and 24 in group II. Both the groups were well matched for age and sex distribution. There was no signiþcant difference between the two groups when various clinical scores were compared. Maximum width of radiolucency was 1.1 mm and the average width was 0.57 mm. B) RSA study: By 12 months, the tibial component had migrated signiþcantly distally (mean: 0.42 mm, S.D.: 0.15 mm) and anteriorly (mean: 0.47 mm, S.D. 0.27mm). No signiþcant migration occurred after 12 mths. There was no correlation between presence or extent of radiolucency and migration of the tibial component. Conclusion: There is no relationship at 2 years between radiolucency and clinical results. There is also no relationship between radiolucency and migration. Therefore radiolucencies of 1mm or less can be ignored