We aim to explain the significant difference in survivor-ship found between two cohorts of patients who underwent different total knee replacements. The first cohort included 70 patients who underwent Kinemax Plus total knee replacement, the second cohort included 58 patients who underwent PFC Total Knee replacement. All patients were under the care of one Consultant Orthopaedic Surgeon.

Interestingly, the Kinemax Plus cohort was found to have a higher rate of revision as compared to the PFC cohort. A detailed comparison was then carried out between the two groups to identify any obvious cause for the disparity.

The two cohorts were found to be well matched with respect to age, sex, ASA grade, underlying pathology and operative technique. Median follow up being 6 years and 5 years for the Kinemax and PFC groups respectively. There were 11 failed prostheses in the kinemax cohort, 7 undergoing revision with the remaining 4 patients offered revision but unwilling have surgery. Wear of the polyethylene tibial insert was the most obvious finding at revision, present in six out of the 7 revisions. 97% of the Kinemax Plus Prostheses were intact at 5 years but by 8 years only 87% were intact.

There were no revisions performed in the PFC cohort.

Post operative x-ray analysis was undertaken to rule out prosthesis misalignment as a cause for the increased failure rate. The coronal alignment of the prostheses (CAK) was calculated and all post operative x-rays were within the normal limits of 4–10 degrees.

Analysis of the explanted Kinemax Plus polyethylene liners was undertaken. In six cases, the polyethylene bearing surfaces displayed severe surface and subsurface delamination at both medial and lateral sides. This suggests massive fatigue and fatigue wear. Only one inplant showed localised delamination. The surface characterisation suggests the hypothesis of weak UHMWPE particle interface strength.

Objective: The aim of the study was to test the hypothesis that insertion of a total knee replacement (TKR) may effect range of motion as a consequence of excessive stretching of the retinaculae.

Methods: 8 fresh frozen cadaver knees were placed on a customised testing rig. The femur was rigidly fixed allowing the tibia to move freely through an arc of flexion. The quadriceps were loaded to 175N in their physiologic lines of action using a cable, pulley and weight system. The iliotibial tract was loaded with 30N. Tibiofemoral flexion and extension was measured using an optical tracking system. Monofilament sutures were passed along the fibres of the medial patellofemoral ligament (MPFL) and the deep transverse band in the lateral retinaculum with the anterior ends attached to the patella. The posterior suture ends were attached to ‘Linear Variable Displacement Transducers’. Thus small changes in ligament length were recorded by the transducers. Ligament length changes were recorded every 10° from 90° to 0° during an extension cycle. A transpatellar approach was used when performing the TKR to preserve the medial and lateral retinaculae. Testing was conducted on an intact knee and following insertion of a cruciate retaining TKR (Genesis II). Statistical analysis was performed using a two way ANOVA test.

Results: The MPFL had a mean behaviour close to isometric, while the lateral retinaculum slackened by a mean of 6mm as the knee extended from 60 degrees (Fig 1). After knee replacement there was no statistically significant difference seen in ligament length change patterns in the MPFL, however the lateral retinaculum showed significant slackening from 10 to 0°.

Conclusion: The data does not support the hypothesis that insertion of a TKR causes abnormal stretching of the retinaculuae. This result relates specifically to the TKR design tested.

Background: The determinants of range of movement following knee replacement may be surgically modifiable (tibial slope, posterior condylar offset or the level of the joint line) or non modifiable (pre-operative range of movement, sex or BMI). We aimed to quantify the influence of these factors upon restoration of flexion in the arthritic knee following knee replacement

Methods: Patients were included from two prospective trials for three different designs of knee replacement. Range of movement was recorded using a standard measuring technique preoperatively and 12 months after surgery. Radiological measurement was done by an independent observer and included the preoperative posterior condylar offset and the postoperative tibial slope, posterior condylar offset, posterior condylar offset ratio, varus-valgus alignment and Insall ratio. Multivariate analysis using stepwise selection was performed to determine the significant predictors of the range of movement at 12 months.

Results: The study includes 133 knee replacements performed on 125 patients. Complete clinical and radiographic data for preoperative and 12-month assessment was available for 101 knees and only these were included for the analyses. There was no significant difference between the three groups in terms of postoperative range of movement or the radiological parameters measured. Multivariate analysis after adjusting for age, sex, diagnosis and the type of prosthesis revealed that the only significant correlates of range of movement at 12-months were the difference in posterior condylar offset ratio, tibial slope and preoperative range of movement. Moderate correlation was noted between range of movement at 12 months and posterior tibial slope (R=0.58) and the difference of post femoral condylar offset (that is, post-operative minus preoperative posterior condylar offset, R=0.65). Preoperative range of movement had only a weak correlation with post-operative range of movement (R=0.20).

Conclusions: We found that the posterior femoral condylar offset had the greatest impact upon final range of movement. We would encourage the operating surgeon at pre-operative templating to take this into account when choosing size and design of femoral component.

Objective: The aim of this study was to test the hypothesis that malrotation of the femoral component following total knee replacement (TKR) may lead to patellofemoral complications as a consequence of excessive stretching of the retinaculae.

Methods: 8 fresh frozen cadaver knees were placed on a customised testing rig. The femur was rigidly fixed allowing the tibia to move freely through an arc of flexion. The quadriceps and iliotibial tract were loaded to 205N in their physiologic lines of action using a cable, pulley and weight system. Tibiofemoral flexion and extension was measured using an optical tracking system. Monofilament sutures were passed along the fibres of the medial patellofemoral ligament (MPFL) and the deep transverse band in the lateral retinaculum with the anterior ends attached to the patella. The posterior suture ends were attached to ‘Linear Variable Displacement Transducers’. Thus small changes in ligament length were recorded by the transducers. Ligament length changes were recorded every 10° from 90° to 0° during an extension cycle. A transpatellar approach was used when performing the TKR to preserve the medial and lateral retinaculae. Testing was conducted following insertion of a cruciate retaining TKR (Genesis II). The femoral component was rotated using a custom built intramedullary device. Ligament length changes were measured at neutral rotation, 5° internal and 5° external rotation. Statistical analysis was performed using a two way ANOVA test.

Results: Internal rotation resulted in the MPFL slackening a mean of 1.7mm from 70-0° extension (p< 0.001). External rotation resulted in the MPFL tightening a mean of 1.5mm over the same range (p< 0.01). The lateral retinaculum showed less significant differences.

Conclusion: External rotation resulted in smaller length changes than internal rotation. Patellar tilting as a result of internal rotation may be caused by MPFL slackening and not lateral retinacular tension, contrary to popular understanding.

Objective: This study tested the hypothesis that complications resulting from overstuffing the patellofemoral joint after total knee replacement (TKR) may be a consequence of excessive stretching of the retinaculae.

Methods: 8 fresh frozen cadaver knees were placed on a customised testing rig. The femur was rigidly fixed and the tibia moved freely through an arc of flexion. The quadriceps and iliotibial tract were physiologically loaded to 205N using a cable, pulley and weight system. Tibiofemoral flexion/extension was measured using an optical tracking system. Monofilament sutures were passed along the fibres of the medial patellofemoral ligament (MPFL) and the deep transverse band in the lateral retinaculum with the anterior ends attached to the patella. The posterior suture ends were attached to ‘Linear Variable Displacement Transducers’. Thus, small changes in ligament length were recorded by the transducers. Length changes were recorded every 10° from 90°- 0° during an extension cycle. A transpatellar approach was used when performing the TKR to preserve the medial and lateral retinaculae. Testing was conducted following insertion of a cruciate retaining TKR (Genesis II). The patella was resurfaced and various patellar thicknesses were achieved by placing 2mm thick nylon washers behind the ‘onlay’ button. The thicknesses measured were 2mm understuff, pre-cut thickness, 2 and 4mm overstuff. Statistical analysis was performed using a two way ANOVA test.

Results: Patellar understuff resulted in the MPFL slackening an average of 1.6mm from 60 to 0° (p< 0.05). Overstuffing the patella 2mm resulted in no significant length changes whereas 4mm overstuff resulted in a mean increase in MPFL length of 2.3mm throughout extension (p< 0.001). No significant length changes seen in the lateral retinaculum

Conclusion: Overstuffing the PFJ stretches the MPFL, because it attaches directly between two bones. The lateral retinaculum attaches to the relatively mobile ITT, so overstuffing does not stretch it.

We report the results of a prospective randomised controlled clinical trial assessing the radiosterophotogrametric analysis (RSA), clinical and radiological performance of a metal backed and an all-polyethylene tibial cruciate retaining, condylar design, PFC-TKA up to twenty four months.

65 patients were recruited, of which 41 patients were randomised. There were 20 metal backed and 21 all-polyethylene. None were lost to follow-up. There were no significant inter-group demographic differences. We found a significant increase in SF-12 and Oxford knee scores after surgery in both groups. No significant difference was found between the groups in the RSA, SF-12, Oxford Knee score, radiological alignment and range of movement at 6, 12 or 24 months. At 2 years one metal backed implant showed translational migration > 1mm. No all polyethylene implant migrated > 1mm. Further analysis identified possible progressive subsidence of the metal backed implants compared to all-polyethylene implants, although the magnitude of this difference was very small.

We conclude that in the uncomplicated primary total knee arthroplasty, all polyethylene PFC-_ tibial prostheses had equivalent performance to the metal backed counterpart, using RSA as the primary assessment instrument at 24 months. We found no differences between the two designs as assessed by the secondary instruments: SF-12, Oxford knee score, alignment and range of movement at 24 months. Should half of all primary total knee replacements performed in the UK receive an all-polyethylene tibial implant, the estimated annual cost saving would be 21 million pounds per annum.

Aim: To analyse the posterior and external rotational laxities in single bundle PCL (sPCL) and double bundle PCL reconstruction (dPCL) in a PCL and PLC deficient knee.

Methods: Ten fresh frozen were used. A custom made wooden rig with electromagnetic tracking was used to measured knee kinematics. Each knee was tested with posterior and anterior drawer forces of 80N and an external rotation moment of 5Nm when intact, after PCL resection, after dividing the PLC and after performing dPCL and sPCL reconstructions with a bone patellar tendon bone allograft and tibial inlay technique.

Results: The one-tailed paired Student’s t test with Bon-ferroni correction was used. There was a significant difference between the ability of the dPCL and sPCL reconstruction to correct the posterior drawer in extension (p=0.002). There was no difference between the dPCL reconstruction and the intact condition of the knee near extension (p=0.142, Fig 1). There was no significant difference between the intact condition and both sPCL (p=0.26) and dPCL (p=0.20) reconstructions in flexion in restoring posterior laxity. Neither of the reconstructions could restore the rotational laxity (Fig 3).

Conclusion: In a combined PCL and PLC deficient knee the posterior laxity can be controlled by both the sPCL as well as the dPCL reconstructions except near extension where the dPCL reconstruction was better.

Aim: To compare the ability of two different PLC reconstruction techniques to restore the kinematics of a PCL & PLC deficient knee to PCL deficient condition.

Methods: 8 fresh frozen cadaver knees were used. A custom rig with electromagnetic tracking system measured knee kinematics. Each knee was tested with posterior & anterior drawer forces of 80N, external rotation moment of 5Nm & varus moment of 5Nm when intact, after dividing PCL, PLC (lateral collateral ligament & popliteus tendon), after PLC reconstruction type1 (1PLC) & PLC reconstruction type 2 (2PLC). 1PLC was modification of Larson’s technique with semitendinosus graft. 2PLC was performed with semitendinosus graft to reconstruct the lateral collateral ligament & the pop-liteofibular ligament, gracillis used to reconstruct pop-liteus tendon.

Results: The one-tailed paired student’s t test with Bon-ferroni correction was used to analyse the data. Only in deep flexion 2PLC reconstruction was significantly better than the 1PLC reconstruction in restoring the posterior laxity to PCL deficient condition (p=0.02). (Figure1) In deep flexion 1PLC could not restore the rotational laxity to PCL deficient condition (p=0.02). In mid flexion the 2PLC was unable to restore the rotational laxity to PCL deficient condition (p=0.048) (Figure 2).

Conclusion: The 2PLC reconstruction was better than the 1PCL in controlling the posterior drawer. The 1PLC technique though not significant tended to over constrain the external & varus rotations.

The aim of this longitudinal study is to compare the clinical outcomes of endoscopic ACL reconstruction with either a 4-strand HT or PT autograft over a 5-year period.

90 patients with isolated ACL rupture received PT autograft and 90 received HT autograft were studied annually for 5 years. Assessment included the IKDC Knee Ligament Evaluation, KT1000, Lysholm Knee Score, thigh atrophy, kneeling pain, hamstring pain and radiographs.

The median Lysholm Knee Score was 96 for the PT group and 95 for the HT group. No significant difference was found for subjective knee function, overall IKDC assessment, Xray findings, manual ligament KT1000 instrumented testing, graft rupture or contralateral ACL rupture. There was an increasing incidence of fixed flex-ion deformity seen in the PT group. There was no difference in the requirement for subsequent surgery. The incidence of kneeling pain at 5 years was significantly higher in the PT group.

Endoscopic reconstruction of the ACL utilizing either autograft can restore knee stability and is menisco protective despite a high level of sporting activity. We did find a worrying trend towards an increasing incidence of fixed flexion deformity with time in the patellar tendon group. Kneeling pain also remains a persistent problem in this subgroup.

Aim: To compare, in a longitudinal study, the clinical outcomes of endoscopic anterior cruciate ligament (ACL) reconstruction with either a four-strand hamstring tendon (HT) or a patellar tendon (PT) autograft over a five-year period, when a similar operative procedure is followed for both groups.

Method: Ninety patients with isolated ACL ruptures who had received PT autografts and another 90 who had received HT autografts were studied annually for five years. Fifty patients were randomised as a subgroup. The assessments included the IKDC Knee Ligament Evaluation, KT1000, Lysholm Knee Score, thigh atrophy, kneeling pain, hamstring pain and radiographs.

Results: The median Lysholm Knee Score was 96 for the PT group and 95 for the HT group. No significant difference was found for subjective knee function, overall IKDC assessment, X-ray findings, manual ligament KT1000 instrumented testing, graft rupture or contra-lateral ACL rupture. There was an increasing incidence of fixed flexion deformity seen in the PT group. There was no difference in the requirement for subsequent surgery. The incidence of kneeling pain at five years was significantly higher in the PT group. The results of the randomised patients were identical to the sequential patients.

Conclusions: Endoscopic reconstruction of the ACL utilizing either type of autograft restored knee stability and was protective of the meniscus despite a high level of sporting activity. We found a worrying trend towards an increasing incidence of fixed flexion deformity with time in the PT group. Pain when kneeling also remained a persistent problem in this subgroup. PT grafts appeared tighter clinically and, with the KT 1000, when assessed up to three years post operatively, compared with HT grafts. Thereafter the results were similar.

Aim: To study the influence of anterior cruciate ligament (ACL) deficiency upon functional outcome after Coventry high tibial osteotomy, four to seven years after the surgery.

Method: One hundred and thirty-five patients (142 knees) each underwent a Coventry high-tibial osteotomy with staple fixation, performed by a single surgeon for medial arthrosis of the knee. During the study period, six patients (seven knees) proceeded to total knee arthroplasty and three patients died from unrelated causes. Nine patients were lost to follow-up. Comparisons were drawn between those patients with an intact ACL (ACLi) and those with ACL deficiency (ACLd).

Results: One hundred and seventeen patients (122 procedures) were available for review (100 males, median age 49 years, range: 29years to 70 years). The median follow up period was 64 months (range 37 to 80 months). The ACLd group was significantly younger (median age was 44 versus 51, p< 0.05) and reported significantly less pain and difficulty with stairs, shopping and rising to stand than the ACLi group. Seventy-eight percent of ACLd patients underwent previous surgical procedures on the affected knee. Ninety-six percent of the ACLd group and 89% of the ACLi group were either enthusiastic or satisfied with the outcome of the surgery. The mean Knee Society Score was 83 and 79 (respectively). All six revisions of the knee arthroplasties were in the ACLi group.

Conclusions: High tibial osteotomy was performed at a younger age for those patients with an absent anterior cruciate ligament. These patients had a subjectively better functional medium-term outcome, despite having had a greater number of surgical procedures prior to the osteotomy and having an ACL-deficient joint.