In the unstable patellofemoral joint (PFJ), the patella will articulate in an abnormal manner, producing an uneven distribution of forces. It is hypothesised that incongruency of the PFJ, even without clinical instability, may lead to degenerative changes. The aim of this study was to record the change in joint contact area of the PFJ after stabilisation surgery using an established and validated MRI mapping technique.

A prospective MRI imaging study of patients with a history of PFJ instability was performed. The patellofemoral joints were imaged with the use of an MRI scan during active movement from 0° through to 40° of flexion. The congruency through measurement of the contact surface area was mapped in 5-mm intervals on axial slices. Post-stabilisation surgery contact area was compared to the pre-surgery contact area.

In all, 26 patients were studied. The cohort included 12 male and 14 female patients with a mean age of 26 (15–43). The greatest mean differences in congruency between pre- and post-stabilised PFJs were observed at 0–10 degrees of flexion (0.54 cm² versus 1.18 cm², p = 0.04) and between 11° and 20° flexion (1.80 cm² versus 3.45 cm²; p = 0.01).

PFJ stabilisation procedures increase joint congruency. If a single axial series is to be obtained on MRI scan to compare the pre- and post-surgery joint congruity, the authors recommend 11° to 20° of tibiofemoral flexion as this was shown to have the greatest difference in contact surface area between pre- and post-operative congruency.

The extension facet angle (EFA) of the medial compartment of the knee has been implicated as a potential mechanical cause for anteromedial knee osteoarthritis.

We developed a novel sagittal plane flexion osteotomy of the medial tibiofemoral compartment. We then performed a cadaveric study to study the effect of the osteotomy on the intra-articular knee pressures under axial load mimicking the stance phase of gait. A Tekscan K400 pressure sensor was inserted submeniscally into the joint and 700N applied using an Instron machine. A topographical map of the pressure areas was then assessed pre- and post-osteotomy for the 10 cadaveric knees specimens.

We found that the intra-articular pressures are greatest in the anteromedial compartment in the native knee and after the osteotomy the area of highest pressure moves posterolaterally spread over a greater surface area.

We conclude that a flexion osteotomy of the medial compartment reduces intra-articular knee pressures concentrated anteromedially in full extension and may be beneficial in patients with an elevated EFA with anteromedial symptoms.

The aim of this study was to document the survivorship and patient reported outcome of the Avon patello-femoral replacement in a consecutive series with follow up of 10 years or more.

All cases performed in Bristol from 1996 onwards were prospectively recorded. Follow up was at 1,2,5,7,10,12 and 15 years with the Bristol Patella Score, the Oxford and WOMAC scores and SF12. Implant survival was analysed using the Kaplan-Meier method.

There were 323 PFJ replacements (280 individuals). Follow up was available for 286 cases in 250 patients (89% follow up). The 10 year survival rate was 77%, falling to 67% at 15 years. The most common reason for revision was tibio-femoral progression (45/74 revisions), with loosening or polyethylene wear recorded in 8 cases. The best results were seen in the youngest and the oldest patients. Good improvements were seen in PROMs, with the mean OKS improving from 19.5 to 34.1 at 2 years and 32.7 at the 15 years.

The Avon patello-femoral knee replacement is a successful long-term treatment for isolated patello-femoral knee osteoarthritis, although further improvements are expected in subsequent series, particularly as indications for surgery have evolved over time.

The aim of this study is to document the outcome of a large cohort of patients treated with the Bereiter trochleoplasty with between 1 and 12 years of follow up.

215 consecutive cases in 186 patients were recorded prospectively. All patients were offered yearly clinical and radiological review. PROMs were recorded including the IKDC, OKS, Kujala and SF-12. Patients unable to attend clinic were assessed with PROMS and radiographs from their local institutions where possible.

There were 133 females and 53 males, with a mean age of 21 (14–38). There were no infections and only 6 patients reported further dislocations. There was one flap breakdown and no identified cases of secondary osteoarthritis. PROMs were available for 194 cases in 167 patients (90% follow up). 84% of patients were satisfied, 87% felt their symptoms had improved and 69% had gone back to sport. All scores improved (all p<0.001) except for the SF-12 mental score (p=0.42), with averages comparable to the results of MPFL reconstruction.

Good outcomes were observed despite the difficult patient population in which these cases were performed. The Bereiter trochleoplasty is an effective method of treating recurrent patella instability in patients with severe trochlea dysplasia.

Aim

To analyse the available rotating hinge knee implants available on the market with a view to deriving a rational algorithm for implant selection.

Aim

To assess if there is a reproducible relationship between the width and thickness of the normal patella.

Patello-femoral arthritis can result in a considerable thinning of the patella. The restoration of an adequate patella thickness is key to the successful outcome of knee arthroplasty.

The objectives were (1) to establish a reproducible patella width:thickness index including chondral surface and (2) to investigate whether there is a difference between bone alone and bone/chondral construct thickness as shown by MRI.

Forty three MRI scans of young adults, mean age 27 (range 17–38), 34 male and 9 female, were studied. Exclusion criteria included degenerative joint disease, patello-femoral pathology or age under 16/over 40 (102 patients). The bony and chondral thickness of the patella and its width were measured. Inter/intra observer variability was calculated and correlation analysis performed.

We found a strong correlation between patella plus cartilage thickness and width (Pearson 0.75, P < 0.001). The mean width:thickness ratio was 1.8 (SD 0.10, 95% CI 1.77–1.83). Without cartilage the ratio was 2.16 (SD 0.15, 95% CI 2.11–2.21), correlation was moderate (Pearson 0.68, P < 0.001). The average patella cartilage thickness was 4.1mm (SD 1.1, 95% CI 3.8–4.5).

The narrow confidence intervals for the ratio of patella width:thickness suggest that patella width can be used as a guide to accurate restoration of patella thickness during total knee or patella-femoral replacement. We would recommend a ratio of 1.8:1.

This study is a prospective analysis of clinical outcome in 201 consecutive patients treated with medial patellofemoral ligament reconstruction using an autologous semitendinosus graft between October 2005 and January 2011. Patients received pre and post-operative clinical evaluation, radiological assessment and outcome scoring systems.

193 patients (92 male, 119 female) underwent 211 procedures, with mean age 26 (16–49) and follow-up 16 months (6–42 months). Indications were atraumatic recurrent patella dislocation (68%), traumatic recurrent dislocation (22.8%), instability (5%), single dislocation (2.7%) and anterior knee pain (1.4%). Trochlea dysplasia was moderate in 57% and mild in 35%.

There have been no recurrent dislocations/ subluxations. 10 patients have required further surgery. The mean pre-op Kujala Scores were 55 (SE 5.21) and post-op scores improved to mean 82 (31–100) (SE 1.18)(p < 0.001). This improvement and significance is mirrored with Oxford (27 to 41), WOMAC (76 to 93), Fulkerson (53 to 83), IKDC (46 to 75), Tegner (4.1 to 5.3) and SF12 (38 to 51) scores (p < 0.005). 93% of patients were satisfied with their operation. History of prior realignment surgery was associated with significantly worse outcomes compared to patients where MPFL reconstruction was their first realignment procedure (p < 0.05).

This series is the largest reported in the literature for any technique of MPFL surgery. This technique allows for objective intra-operative evaluation of the required graft tension to optimise patella tracking.

Trochlear dysplasia is a developmental condition characterised by an abnormally flat or dome shaped trochlea and is an important contributing factor to patellofemoral instability and recurrent patellar dislocation. We prospectively studied a cohort of 54 consecutive patients (59 knees) with patellofemoral instability secondary to trochlear dysplasia, treated with a trochleoplasty by a single surgeon over a 5 year period.

Patients were recruited from the senior author's specialist knee clinic and pre-operatively, multiple patient-centred scores were recorded. After the trochleoplasty, these were repeated along with a patient satisfaction questionnaire. Of the 54 patients and 59 knees operated, 39 of the patients (44 knees) were female and 15 (15 knees) male and 40 patients (42 knees) had follow-up of 12 months or more. Their mean age at surgery was 21 years and 6 months and mean length of follow up 2 years. One patient was unable to attend for follow up due to the development of a pelvic Ewings sarcoma. A statistically significant improvement in outcomes was demonstrated when the pre and post-operative scores were compared (mean scores of Oxford 26 to 19, WOMAC 23 to 17, IKDC 54 to 72, Kujala 62 to 76, Lysholm 57 to 78, p values <0.001 for all scores). 93% (50 patients) were satisfied with the outcome of their procedure.

We conclude that in the short and medium term, the results of trochleoplasty are encouraging in this challenging group of patients.

Introduction

The Bristol Knee Group has prospectively followed the results of over 500 isolated patellofemoral arthroplasties. Initial experience with the Lubinus prosthesis was disappointing. The main causes of failure were mal-tracking and instability leading to excessive polythene button wear and disease progression in the tibio femoral joint.

This experience resulted in the design of a new prosthesis to correct the tracking problems and improve the wear. We have now performed over 425 Avon arthroplasties with a maximum follow-up of 9 years.