Aims

Femoroacetabular Junction Impingement (FAI) describes abnormalities in the shape of the femoral head–neck junction, or abnormalities in the orientation of the acetabulum. In the short term, FAI can give rise to pain and disability, and in the long-term it significantly increases the risk of developing osteoarthritis. The Femoroacetabular Impingement Trial (FAIT) aims to determine whether operative or non-operative intervention is more effective at improving symptoms and preventing the development and progression of osteoarthritis.

The Femoro Patella Vialli (FPV) is indicated for isolated patello-femoral joint replacement (PFJR). It is now the second most commonly used PFJR in the UK, however there are limited studies evaluating its outcome. Key differences include a larger component sulcus angle of 140 degrees which more closely mimics the normal knee.

Between 2006 and 2012, we performed 53 consecutive FPV patellofemoral arthroplasties in 41 patients with isolated patellofemoral joint osteoarthritis. Mean age was 62.2years (39–86) and mean follow-up was 3.5 years. Mean Oxford Knee scores improved from 19.7 to 37.7 at latest follow-up. Ninety four percent of patients were happy or very happy with their knees. Progression of tibiofemoral osteoarthritis was seen 12% of knees. 2 knees required revision to TKR at 7 months post-operatively, which we attribute to poor patient selection. There were no cases of maltracking patella or patella dislocations at final follow-up, which we attribute to the larger sulcus angle. There were no cases of radiological loosening.

Our findings suggest the FPV patellofemoral prosthesis has good mid-term functional outcomes.

Purpose of Study:

To describe the degree and type of disability experience by patients with combined postero-lateral corner and posterior cruciate ligament knee injuries

Methods and Results: After rigorous exclusion criteria were instituted twelve patients were identified as having the required combined knee ligament injuries. These patients underwent functional assessment, clinic examination and gait analysis at the Oxford Gait Laboratory.

Significant functional disability was noted in all patients. Characteristic gait abnormalities identified included hyperextension and dynamic varus deformity with a corresponding increase in the internal valgus knee moment. Electromyographic data revealed early and prolonged contraction of the medial hamstrings and gastrocnemius muscles.

Conclusion: These results suggest the presence of compensatory mechanisms of the musculature around the knee and suggest direction in rehabilitation programs in patients with combined injuries to the posterior cruciate ligament and posterolateral corner of the knee. The results also provide baseline data that will be useful when evaluating the post-operative outcomes in patients undergoing knee ligament reconstruction in the future.

Medial unicompartmental replacement (UKR) has been shown to have superior functional results to total knee replacement (TKR) in appropriately selected patients, and this has been associated with a resurgence of interest in the procedure. This may relate to evidence showing that the kinematic profile of UKR is similar to the normal knee, in comparison to TKR, which has abnormal kinematics. Concerns remain over the survivorship of UKR and work has suggested the anterior cruciate ligament (ACL) may become dysfunctional over time. Cruciate mechanism dysfunction would produce poor kinematics and instability providing a potential mechanism of failure for the UKR.

Aim: To test the hypothesis that the sagittal plane kinematics (and cruciate mechanism) of a fixed bearing medial UKR deteriorate over time (short to long term).

A cross sectional study was designed in which 24 patients who had undergone successful UKR were recruited and divided into early (2–5 years) and late (> 9 years) groups according to time since surgery. Patients performed flexion/extension against gravity, and a step up. Video fluoroscopy of these activities was used to obtain the Patellar Tendon Angle (PTA), the angle between the long axis of the tibia and the patella tendon, as a function of knee flexion. This is a previously validated method of assessing sagittal plane kinematics of a knee joint.

This work suggests the sagittal plane kinematics of a fixed bearing UKR is maintained in the long term. There is no evidence that the cruciate mechanism has failed at ten years. However, increased tibial bearing conformity from ‘dishing’, and adequate muscle control, cannot be ruled out as possible mechanisms for the satisfactory kinematics observed in the long term for this UKA.

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 contra-indication to UKA. The aim of this study was to determine the influence of PFOA on the outcome of medial UKA.

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. A pre-operative skyline radiograph was graded using the Altman score, by an independent Musculoskeletal Radiologist. 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 Altman grade using a one way ANOVA. Repeat analysis was performed using the presence of anterior knee pain (AKP) as the group defining variable.

There were 28 patients with FTCL, and both groups were well matched for age, gender and activity levels. Analysis showed no significant difference in post operative knee scores between groups with either the presence of FTCL or the presence of AKP pre-operatively as a factor. There was no significant difference in Altman grade between groups.

Intra-operative evidence of PFOA in patients with medial compartment osteoarthritis does not prejudice the outcome of UKA. Even the inclusion of patients with symptomatic AKP, without necessarily having PFOA, does not affect the outcome after UKA. These short results are encouraging, but longer follow up is required.

Functional outcome after patellofemoral joint replacement (PFA) for osteoarthritis remains inconsistent. It is believed that functional outcome for joint replacement is dependent upon postoperative joint kinematics. Minimal disruption of the native joint, as in PFA, should produce more normal kinematics and improved outcome. No previous studies have examined joint kinematics after isolated PFA.

Aim: To investigate the sagittal plane kinematics of patellofemoral replacement and compare with the normal knee.

Twelve patients who had undergone successful PFA at least two years previously were recruited. Patients performed flexion/extension against gravity, and a step up. Video fluoroscopy of these activities was used to obtain the Patellar Tendon Angle (PTA), the angle between the long axis of the tibia and the patella tendon, as a function of knee flexion. This is a previously validated method of assessing sagittal plane kinematics of a knee joint. The kinematic profile of the PFA joints was compared to the profiles for fourteen normal knees.

Overall, the kinematic plot obtained for PFA reflected similar trends to that for normal knees; but the PTA was slightly but significantly increased throughout the entire range of flexion (two degrees). This is equivalent to an average displacement of the lower pole of the patella of 1.5mm.

Sagittal plane knee kinematics after PFA are much more normal than after TKR and this should give improved functional outcome. The observed increase in PTA through range may result from increased patella thickness or a shallow trochlear groove and may influence patellofemoral contact forces.

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

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: 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 and Aims: The effects of injury to the posterior cruciate ligament (PCL) and posterior-lateral corner (PLC) on physical function are not as well documented compared to the more common injury to the anterior cruciate ligament. This study aimed at improving our understanding of PCL/PLC injury through gait analysis and electromyographic (EMG) testing.

Method: We studied 19 patients, average age 30 years (20–55) with clinically and radiologically confirmed PCL/PLC deficiency in isolation. Ninety percent of patients complained of instability when performing the activities of daily living and all complained of pain. All patients were assessed using the Lysholm and Gillquist functional knee score as well as gait analysis, including Kinematics, Kinetics and EMG of the quadriceps, hamstrings and gastrocnemius muscles. Findings were compared to our normal database. The mean Lysholm score was 51/100 (24–90). Those with a Lysholm greater than 50 were designated as ‘copers’.

Results: There were 12 ‘non-copers’ and seven ‘copers’. Fifty percent of patients demonstrated a varus thrust through stance. Forty-two percent of patients demonstrated hyperextension of the knee through stance. Sixty-three percent of patients demonstrated premature and prolonged hamstring activity. Thirty-seven percent of patients had premature activity of the gastrocnemius muscle in stance. Fifty-seven percent of the ‘copers’ demonstrated premature and prolonged hamstring activity through the gait cycle compared to forty-five percent of ‘non-copers’ (non-significant p=0.25 Fishers Exact Test). Fifty-five of ‘non-copers’ demonstrated premature activity of the gastrocnemius muscle in stance compared to none of the ‘copers’ (significant p=0.025 Fishers Exact Test).

Conclusion: The observed varus thrust may be responsible for the development of medial and patellofemoral compartment osteoarthritis, a recognised problem in PCL deficient knees. Hyperextension that occurs dynamically during gait could explain failure of PCL/PLC reconstruction over time. The observed abnormal hamstrings activity is unlikely to be a compensatory mechanism.

Introduction and Aims: Single compartmental replacement procedures are increasingly preferred over total knee replacement (TKR) for single compartment osteoarthritis of the knee joint. Theoretically, reduced disruption of the native joint should produce more normal kinematics. This study aimed to describe and compare the sagittal plane kinematics of four different, commonly used devices.

Method: Four groups of patients who had undergone successful single compartment replacement at least two years previously were recruited. Fifteen following Oxford medial UKA, 12 following medial St Georg Sled UKA, five following Oxford lateral UKA, and 12 following Avon PFJ replacement. Patients performed flexion/extension against gravity, and a step-up during video fluoroscopy. The Patellar Tendon Angle (PTA), the angle between the long axis of the tibia and the patella tendon, was obtained as a function of knee flexion. This relationship provides indication of sagittal movement between femur and tibia through range and has been validated as a reliable measure of joint kinematics.

Results: The kinematic profile for each group was compared to that of the profile for 12 normal and 30 TKR (AGC) knees. All three tibiofemoral devices produced knee kinematics similar to the normal knee. The PTA was found to have a linear relationship to flexion angle, decreasing with increasing knee flexion angle. No such linear relationship exists for the TKR joint, which display abnormal kinematics. The PF device also reflected similar trends to that for normal knees except that the PTA was moderately increased throughout the entire range of flexion (three degrees).

Conclusion: In contrast to TKR, all single compartmental knee replacements provided kinematics similar to the normal joint. The kinematic pattern of the PFJ replacement may be of most interest as the observed increase in PTA through range could influence patello-femoral contact forces

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.

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.

Over a five year period 50 patients required combined orthoplastic care out of 987 patients presenting with bone and soft tissue tumours. Thirty men, mean age 51 years, had their treatment reviewed at a mean follow up of 23 months (3–54 months) post surgery. All surviving patients completed the Toronto Extremity Salvage Score.

There were 23 bone and 27 soft tissue sarcomas, 4 were Enneking stage I, 41 stage II and 5 stage III. All tumours were removed by wide resection to achieve microscopically clear margins in 49. 9 endoprostheses were inserted. Soft tissue reconstruction involved 9 local flaps, 13 distant flaps (mainly muscle) and 8 free flaps (including 3 composite osseous flaps). 20 patients received adjuvant radiotherapy and 14 patients received chemotherapy.

Two endoprosthetic replacements required surgery for infection, one distant lap and one free flap required further surgery (6%). The mean disease free interval was 29 months (2–49 months). There were 6 deaths and pulmonary metastases occurred in a further 8 patients. Within this study period there was one episode of local recurrence, but no local recurrence in the group that had radiotherapy. 77% of surviving patients completed the Toronto Extremity Salvage Score and good to excellent function was seen in most cases.

Combined orthoplastic approach facilitates limb sparing surgery and early adjuvant radiotherapy.