Introduction

The biological pathways responsible for adverse reactions to metal debris (ARMD) are unknown. Necrotic and inflammatory changes in response to Co-Cr nanoparticles in periprosthetic tissues may involve both a cytotoxic response and a type IV delayed hypersensitivity response.

Our aim was to establish whether differences in biological cascade activation exists in tissues of patients with end-stage OA compared to those with aseptic loosening of a metal on polyethylene (MoP) THR and those with ARMD from metal-on-metal (MoM) THR.

Background

Patellar instability is a complex, multi-factorial disorder. Radiological assessment is regarded as an important part of the management of this population. The purpose of this study was to determine the intra- and inter-rater reliability of common radiological measurements used to evaluate patellar instability.

Background

Shockwave therapy has been shown to induce osteoneogenesis in animal models. The mechanism of action is unclear, but experimental evidence suggests micro-fracture formation and increased blood flow as the most likely explanation. Several reports from Europe have suggested good results from the treatment of delayed fracture union with shock-waves. We present the results of a randomised double-blind placebo-controlled pilot study.

Patella instability is a common problem with many surgical options. We prospectively evaluated the results of medial patella femoral ligament (MPFL) reconstruction with an autogenous gracilis or semitendinous graft. With a minimum follow up of one year patients were reviewed using the Kujala scoring system.

Twenty MPFL reconstructions were performed on seventeen patients over a two year period, from January 2004 to December 2005. There were 13 females and 4 males. Three patients had bilateral involvement. Thirteen patients had a lateral release with their MPFL reconstruction and three had a distal realignment procedure as well to correct their patella instability.

The mean follow up was 17 months (range 12 to 26 months). The average age was 25 years old at operation (range 13 to 47) and the average age of their first dislocation was 16 (range 0-35). Nine patients had previous surgical treatment for patella instability. The average hypermobility score in the patients was 5/9 and six patients scored 9/9.

At follow up 18 out of 20 patients (90%) had stable tracking with no further subluxations/dislocations. Of the two with unstable tracking, one had a stable patella before falling several times onto her knee. An MRI confirmed the ligament was intact but a type 2 trochlear dysplasia was present and a Bereiter trochleoplasty was subsequently performed. The other patient described no frank dislocation but instead subluxations.

Eighteen of the twenty reconstructions (90%) achieved a stable patella. Overall Kujala scores increased by a third.

The aim of this study was to compare immediate weight-bearing mobilisation with traditional plaster casting in the rehabilitation of non-operatively treated Achilles tendon ruptures.

Forty-eight patients with Achilles tendon rupture were randomised into two groups. The treatment group was fitted with an off-the-shelf carbon-fibre orthotic and the patients were mobilised with immediate full weight-bearing. The control group was immobilised in traditional serial equinus plaster casts. The heel raise within the orthotic and the equinus position of the cast was reduced over a period of eight weeks and then the orthotic or cast was removed. Each patient followed the same rehabilitation protocol. The primary outcome measure was return to the patient's normal activity level as defined by the patient.

There was no statistical difference between the groups in terms of return to normal work [p=0.37] and sporting activity [p=0.63]. Nor was there any difference in terms of return to normal walking and stair climbing. There was weak evidence for improved early function in the treatment group.

There was 1 re-rupture of the tendon in each group and a further failure of healing in the control group. One patient in the control group died from a fatal pulmonary embolism secondary to a DVT in the ipsilateral leg.

Immediate weight-bearing mobilisation provides practical and functional advantages to patients treated non-operatively after Achilles tendon rupture. However, this study provides only weak evidence of faster rehabilitation.

The purpose of this study was to profile the mRNA expression for the 23 known matrix metalloproteinases (MMPs), 4 tissue inhibitor of metalloproteinases (TIMPs) and 19 ADAMTSs (a disintegrin and metalloproteinase with thrombospontin motif) in Dupuytren's Disease and normal palmar fascia.

Dupuytren's Disease (DD) is a fibroproliferative disorder affecting the palmar fascia, leading to contractures. The MMPs and ADAMTSs are related enzymes collectively responsible for turnover of the extracellular matrix. The balance between the proteolytic action of the MMPs and ADAMTSs and their inhibition by the TIMPs underpins many pathological processes. Deviation in favour of proteolysis is seen in e.g. invasive carcinomata, whereas an imbalance towards inhibition causes e.g. fibrosis. A group of patients with end-stage gastric carcinoma was treated with a broad spectrum MMP inhibitor in an attempt to reduce the rate of carcinoma advancement; a proportion developed a ‘musculoskeletal syndrome’ resembling DD.

Tissue samples were obtained from patients undergoing surgery to correct contractures caused by DD and from healthy controls undergoing carpal tunnel decompression. The DD tissue was separated macroscopically into cord and nodule. Total RNA was extracted and mRNA expression analysed by quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR), normalised to 18S rRNA. Comparing across all genes, the DD nodule, DD cord and normal palmar fascia samples each had a distinct mRNA expression profile. Statistically significant (p<0.05) differences in mRNA expression included: higher MMP-2, -7 and ADAMTS-3 levels in both cord and nodule; higher MMP-1, -14, TIMP-1 and ADAMTS-4 and -5 in nodule alone, lower MMP-3 in nodule and cord and lower TIMP-2, -3 and -4 and ADAMTS-1 and -8 levels in nodule alone.

The distinct mRNA profile of each group suggests differences in extracellular proteolytic activity which may underlie the process of fascial remodelling in DD.

Classification of osteoarthritis of the hip is fraught with difficulty Although different patterns of disease are recognised, there is no accepted classification or grading system. We aim to develop a classification system that reflects both the radiological changes, and the local disease process within the joint.

After ethical permission and consent tissue was taken from 20 patients undergoing primary hip replacement surgery. Intra-operative tissue samples were taken from each patient and the steady state gene expression of several cytokines (TNF-α, IL1-β, IFN-γ, IL-6, RANKL and OPG) measured quantitatively using Taqman RT-PCR. Relative expression was calculated for each sample using standard curves and normalised to 18S expression. The technique was consistent with high correlations for repeated measures from the same tissue type (κ=0.99) and from different tissue types in the same joint (κ=0.92). Intra-observer (κ=0.93) and inter-observer (κ=0.89) reliability for the technique were also found to be high.

Preoperative radiographs were scored by two independent observers and joint space narrowing, cysts, osteophytes and sclerosis noted in each of the DeLee-Charnley zones on the femoral and acetabular side. Based on these scores patients were then classified to either lytic or sclerotic type and subclassified into either hypertrophic or atrophic.

Subgroup analysis of cytokine expression by radiographic type was performed. There were statically significant differences in expression of macrophage stimulating cytokines (IL-1γ and OPG) in the lytic group as compared to the sclerotic group (p< 0.05). Conversely, the sclerotic group expressed significantly higher levels of IL-6. Individuals with atrophic subtype demonstrated significantly higher levels of IL-1β and IL-6, but lower levels of IFN-γ

Our results demonstrate greatly differing patterns of disease within osteoarthritic hip joints. These changes are reflected in radiographic appearances of osteoarthritis. Our proposed classification system can be used grade and classify osteoarthritis in a manner that reflects the disease process.

We report a retrospective study of the major complications following one-stage and two-stage bilateral unicompartmental knee replacements (UKR). Between 1999 and 2008, 911 patients underwent 1150 UKRs through a minimally- invasive approach in our unit. Of these, 159 patients (318 UKRs) had one-stage bilateral UKR and 80 patients (160 UKRs) had two-stage bilateral UKRs. The remainder were unilateral UKRs.

The bilateral UKR groups were comparable in age and ASA grade, but more females were in the two-staged group (p=0.019). Mechanical thromboprophylaxis was used in all cases. Major complications were recorded as death, pulmonary embolus, proximal deep vein thrombosis (DVT) and adverse cardiac events within 30 days of surgery.

No statistical differences between the groups were found regarding operating surgeon, tourniquet time or minor complications (excepting distal DVT). Anaesthetic times were greater for the two-stage group (p= 0.0001). Major complications were significantly more common with one-stage bilateral UKR (13 patients, 8.2%) compared to two-stage bilateral UKR (no patients) (p=0.005). Distal DVT was more frequent in the two-stage group (p=0.036).

This series reports significantly higher risks of major complications are associated with one-stage bilateral UKR when compared to two-stage bilateral UKR. There is no evidence that the addition of chemical thrombo-prophylaxis would change this risk. We advocate caution before undertaking a one-stage bilateral UKR.

There has been very little documented regarding the impact of meniscal injuries on knee proprioception. The aim of this study was to investigate the proprioceptive function of patients with meniscal tears and asses the influence that arthroscopic partial menisectomy has on knee proprioception.

One hundred subjects were recruited comprising an Arthroscopy group (50 patients) and a Normal Control group (50 subjects). The Biodex Balance SD System was used to assess proprioception. This equipment measures knee proprioception on an electronic platform. The balance of the subject is computed producing an Overall Stability Index (OSI). Lower scores reflect better proprioception. Knee stability was assessed clinically and with the Rolimeter knee arthrometer. The Lysholm and IKDC scoring systems were used to evaluate all the subjects.

Of the 50 subjects within the Arthroscopy group (all of whom had a normal ACL confirmed) 34 were found to have meniscal tears. Twenty-nine of the 34 patients with meniscal tears returned for their follow-up review 3 months post-operatively.

The proprioceptive function of the injured knee of the Arthroscopy group with meniscal tears (mean OSI 0.86) was significantly poorer compared to that of their uninjured knee (mean OSI 0.62, p< 0.001, 95%CI 0.14, 0.34) and to the Normal Control group (mean OSI 0.49, p< 0.001, 95%CI 0.21, 0.54). There was no significant improvement in their proprioceptive function following menisectomy (mean OSI 0.75, p=0.23, 95%CI −0.07, 0.28). There was a significant improvement of both the Lysholm (p=0.004) and IKDC (p=0.021) scores postoperatively.

Conclusion: These results indicate that there is a demonstrable proprioceptive deficit in patients with meniscal tears even in the presence of a normal ACL. This deficiency in proprioception did not improve within three months following arthroscopic partial menisectomy despite the improvement in functional outcome measures.

Our objective was to investigate how patients, general practitioners (GPs) and orthopaedic trainees, feel about the proposed governmental changes to reduce orthopaedic outpatient clinics by having GPs and specialist nurses follow-up post operative orthopaedics patients in the community. This was a cross-sectional questionnaire study of Teaching hospital and general practitioners in the Norfolk primary care trust.

Of 73 orthopaedic post-operative patients who attended outpatients over a one week period in July 2007, all responded. Of 250 General Practitioners, 239 responded. Of 38 orthopaedic trainees at the level of SHO (post MRCS) and SpR’s (Eastern deanery rotation and Pott rotation) 30 responded. Main outcome measures: opinions of GPs, Surgical trainees and Patients regarding proposed changes to outpatient orthopaedic clinics.

Of the patients 56 of 73 (77%) felt the surgeon was best suited to manage them post-operatively. Of these 47 felt that it was very important that the surgical team saw them post-operatively. Also 53 felt that their GP did not have sufficient knowledge and experience to adequately deal with their current orthopaedic problem. General Practitioners: Only 12 of 239 (5%) felt very confident assessing post-operative patients. Inadequate resources available to diagnose and treat post-operative complications was noted by 74% as the reason for not performing follow-up in primary care, and only 18% felt they should follow up post-operative patients. Trainees: All felt that following up their own post-operative patients was important to their training.

Most patients, GPs, and orthopaedic trainees had serious doubts about proposed governmental changes to reduce orthopaedic outpatient clinics by having GPs and specialist nurses follow-up post operative orthopaedics patients in the community.

The introduction of new treatments needs to be both clinically effective and cost effective. Clinicians tend to be unaware of the importance of the latter, and how health economic assessments are undertaken, especially in a public health system where the inclusion of funded treatments is made on a national basis. The purpose of this study was to determine the cost savings from a societal perspective in the use of recombinant human Bone Morphogenetic Protein -2 (rhBMP-2) in grade III A and B open tibia fractures treated with a locked intramedullary nail and soft-tissue management in the UK, Germany, and France. Healthcare system (direct healthcare costs) and costs for productivity losses (indirect health-care costs) were calculated using the raw data from the Bone Morphogenetic Protein Evaluation Group in Surgery for Tibial Trauma “BESTT study”. Return-to-work time for estimation of productivity losses was assumed to correspond with the time of fracture healing. For calculation of secondary interventions costs and productivity losses the respective 2007/08 national tariffs for surgical procedures and average national wages for the UK, Germany, and France were used. From a societal perspective, overall savings per case of €7911 for the UK, €9270 for Germany, and €9291 were calculated. Those savings largely offset the upfront price of rhBMP-2 of €2266(£1,790) in the UK, €2970 in Germany, and €2950 in France. Total net savings can be estimated to be €9.6 million for the UK, €14.5 million for Germany, and €11.4 million for France. For all three countries reduced productivity losses are the key driver for the overall savings. In summary, despite the apparent high direct cost of rhBMP-2 in grade III A and B open tibia fractures, at a national level there are net cost-savings from a societal perspective for all three countries.

Aim: To systematically review the present evidence-base, assessing the clinical and radiological outcomes following trochleoplasty for trochlear dysplasia.

Methods: An electronic literature search was performed using the AMED, British Nursing Index, CINAHL, Cochrane, EMBASE, ovid Medline, Physiotherapy Evidence Database, PsycINFO, Pubmed and Zetoc databases from their inception to August 2007. Reference lists of identified papers and a hand search of specialist knee journals was also undertaken. All English language, human subject clinical studies, detailing the clinical and/or radiological outcomes of patellar instability patients following a trochleoplasty were included. Two independent reviewers appraised each paper using the CASP tool.

Results: Six papers comprising of 117 trochleoplasty procedures on 99 patients were reviewed. Clinically and radiologically, trochleoplasty was shown to be a safe and effective procedure to correct patellar instability in trochlear dysplasia patients. However, the CASP tool identified that the evidence-base reviewed presented with a number of methodological limitations. These included: limited use of inferential statistics; not applying reliable outcome measurements; poor description of patient recruitment; and evaluating small samples.

Conclusion: Although trochleoplasty may be an effective procedure to correct patellar instability in trochlear dysplasia patients, further study is recommended to assess longer-term outcomes using well-designed studies.

Introduction: The addition of recombinant human bone morphogenetic protein-2 (rhBMP-2) showed significant reduction of secondary intervention, fracture healing time and infection rates compared with intramedullary nailing alone in open tibia fractures. However, the upfront price of approx. 3000 € is a barrier to its regular use. The goal of the study was to determine potential cost savings and cost-effectiveness of rhBMP-2 in grade III open tibia fractures from the perspective of the UK National Health Service (NHS) and the German Health Care System and to derive conclusions for other European health care systems.

Materials and Methods: Clinical data from a previously published randomised controlled study with 450 patients (“BESTT study”) were used to generate total treatment costs for each patient for the control and the 1.5 mg/ml BMP-2 group based on the current German-DRG and the NHS for UK. The analysis was performed from a health care system and a societal perspective for a one year time horizon. Furthermore, assessment of the cost-effectiveness of BMP-2 was done by utility analysis.

Results: The use of BMP-2 for grade III open tibia fractures is leading to cost savings of 3183 € per case and, therefore, to net savings for the German health care system. The main driver for cost savings is faster fracture healing with faster resumption of work and reduced expenses for sickness leave payments. For the UK rhBMP-2 is a cost-effective strategy with a cost-effectiveness ratio of approx. £11,000/QALY which is well below the standard £30,000 benchmark for the NHS. From a societal perspective, rhBMP-2 is a cost-saving treatment.

Conclusions: BMP-2 leads to net savings in grade III open tibia fractures in Germany which can be expected for other European countries where sickness payments are provided by health care insurers. For countries like UK where sickness are provided by third parties BMP-2 is a cost-effective treatment strategy from a health care system perspective and a cost-saving treatment from a societal perspective.

This study was performed to compare the clinical outcomes and radiographic changes between patients with cruciate retaining (CR) and cruciate substituting (CS) total knee replacements (TKR) where the PCL was cut in both groups.

From 1997 to 2001, 114 patients (79 females and 35 males) were enrolled in this study. Patients were blindly randomized into two groups, group 1 having a CR TKR and group 2 having a CS TKR. After surgery patients were followed up at six weeks, one year and at five years. The evaluation parameters at the 5 year assessment included the Oxford Knee Questionnaire, American Knee Society scoring system, SF-12 questionnaire and weight bearing radiographs of the knee, with anteroposterior and lateral views.

There were 80 patients at the time of five year follow up. Of the other patients, 26 had died and 10 were either too ill to attend or did not respond to a follow up request. The average patient follow up was for 77 months (ranging from 51 to 96 months). There was no statistical difference between the two groups in the Oxford Knee Questionnaire, American Knee Society scoring system or the SF-12. Radiological assessment showed no statistical difference in radiolucent lines in either group. At five year follow up, one knee in the CS group had been revised for deep infection. The patient required a two stage revision procedure.

Our study has shown no statistical difference in the five year results for a CR TKR or CS TKR. This suggests that a non-functioning PCL does not affect the performance of a CR TKR.

One of the factors that influence the outcome after Achilles tendon rupture is gait abnormality. We prospectively assessed 14 patients with Achilles tendon rupture and 15 normal control subjects using an in-shoe plantar pressure measurement system. There was a significant reduction in peak mean forefoot pressure in the early period of rehabilitation (p < 0.001). There was a concomitant rise in heel pressure on the injured side (p=0.05). However, there was no difference in cadence, as determined by the duration of the terminal stance and pre-swing phases as a proportion of the total stance component of the gait cycle. The forefoot pressure deficit in the Achilles tendon rupture group was smaller when assessed six months after the injury but was still significant (p=0.029). Pedobarographic assessment of patients after Achilles tendon rupture confirms that there are marked abnormalities within the gait cycle. Rehabilitation programmes which address these abnormalities may improve outcome.

The matrix metalloproteinases (MMPs) and ADAMTSs (a disintegrin and metalloproteinase with thrombos-pontin motif) are related enzymes collectively responsible for turnover of the extracellular matrix. The balance between the proteolytic action of the MMPs and ADAMTSs, and their inhibition by the tissue inhibitors of metalloproteinases (TIMPs), underpins many pathological processes. Deviation in favour of proteolysis is seen in e.g. invasive carcinoma, whereas an imbalance towards inhibition causes e.g. fibrosis.

Dupuytren’s Disease (DD) is a fibroproliferative disorder affecting the palmar fascia, leading to contractures. A group of patients with end-stage gastric carcinoma were treated with a broad spectrum MMP inhibitor in an attempt to reduce the rate of tumour advancement: a proportion developed a ‘musculoskeletal syndrome’ resembling DD. Several groups have looked at subsets of the metalloproteinase family in relation to DD, but to date, a study of the gene expression of all of the members has not been published. We therefore set out to profile the mRNA expression for the 23 known MMPs, 4 TIMPs & 19 ADAMTSs in DD and normal palmar fascia.

Tissue samples were obtained from patients undergoing surgery to correct contractures caused by DD and from healthy controls undergoing carpal tunnel decompression. The DD tissue was separated macroscopically into cord and nodule. Total RNA was extracted and mRNA expression analysed by quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR), normalised to 18S rRNA. Comparing across all genes, the DD nodule, DD cord and normal palmar fascia samples each had a distinct mRNA expression profile. Statistically significant (p< 0.05) differences in mRNA expression included: higher MMP-2, -7 and ADAMTS-3 levels in both cord and nodule; higher MMP-1, -14, TIMP-1 and ADAMTS-4 and -5 in nodule alone, lower MMP-3 in nodule and cord and lower TIMP-2, -3 and -4 and ADAMTS-1 and -8 levels in nodule alone.

The distinct mRNA profile of each group suggests differences in extracellular proteolytic activity which may underlie the process of fascial remodelling in DD. Further in vitro experiments are planned based on these observed differences in gene expression.

Introduction: Tendon lengthening is an important cause of morbidity after Achilles tendon rupture. However, direct measurement of the tendon length is difficult. Ankle dorsiflexion has therefore been used as a surrogate measure, on the assumption that it is the Achilles tendon that limits this movement. The aim of this investigation was to assess the relationship between Achilles tendon length and ankle dorsiflexion. The primary research question was whether or not the Achilles tendon is the structure that limits ankle dorsiflexion. The secondary purpose was to quantify the relationship between Achilles tendon lengthening and dorsiflexion at the ankle joint.

Methods: Five cadaveric specimens were dissected to expose the tendons and capsular tissue of the leg and hindfoot. Fixed bony reference points were used as markers for the measurements. In the first specimen, the Achilles tendon was intact and the other structures that may limit ankle dorsiflexion were sequentially divided. In the other specimens the Achilles tendon was lengthened by 1cm intervals and the effect upon ankle dorsiflexion movement was recorded.

Results: Division of the other tendons and the capsular tissue around the ankle joint did not affect the range of ankle dorsiflexion. When the Achilles was divided the foot could be dorsiflexed until the talar neck impinged upon the anterior aspect of the distal tibia. There was a mean increase of 12 degrees of dorsiflexion for each centimetre increase in tendon length.

Conclusion: The Achilles tendon is the anatomical structure that limits ankle dorsiflexion, even when the tendon is lengthened. There was a linear relationship between the length of the Achilles tendon and the range of ankle dorsiflexion in this cadaveric model. Ankle dorsiflexion would appear to be a clinically useful indicator of tendon length.

We performed two independent randomised controlled trials to assess the potential benefits of immediate weight-bearing mobilisation for Achilles tendon ruptures. The first trial on surgically treated patients provides strong evidence of improved functional outcome for patients mobilised fully weight-bearing after operative repair of their Achilles tendon rupture. The two cases of re-rupture in the treatment group suggest that careful patient selection may be required as patients need to follow a structured rehabilitation regime.

The second trial performed upon non-operatively treated patients provides only weak evidence of a functional benefit from immediate weight-bearing mobilisation. However, the practical advantages of immediate weight-bearing did not predispose the patients to a higher complication rate. In particular there was no evidence of tendon lengthening or a higher re-rupture rate. We would therefore advocate the use of immediate weight-bearing mobilisation for the rehabilitation of all patients with rupture of the Achilles tendon.

The aim of this study was to test the efficacy of shock-wave therapy for chronic Achilles pain. Forty-nine patients with Achilles tendon pain for a minimum of 4 months were included in the study. Patients were randomised to either shockwave therapy (n=27) or placebo control (n=22). The treatment group were given 2000 shocks at up to 1500 mJ/mm2 per shock. The control (sham) treatment was applied using the same parametres but the shockwaves were dispersed before they reached the patient. Each patient was treated once a month over 3 months. The primary outcome measure was pain on walking indicated on a 100mm visual analogue score (VAS) at 3 months. The walking pain scores were very similar at baseline between the two groups. In the treatment group the mean (standard deviation) was 55.5 mm (30.6) and in the control group 55.6mm (26.5). By 3 months, the pain scores had reduced in both groups to a mean (standard deviation) of 34.5 mm (34.2) and 50.3 mm (36.3). Although lower in the treatment group this difference was not statistically significant at the 5% level (t-test, p=0.127, 95% CI : −4.7 to 36.2). Two elderly patients in the treatment group sustained spontaneous rupture of the tendon after falls during the course of the trial. The results of this trial provided no evidence for the use of shockwave therapy in the treatment of patients with chronic Achilles tendinopathy. However, a treatment effect cannot be ruled out since the 95% confidence interval included a potential clinically relevant difference. The two cases of rupture suggest extreme caution in treating the elderly.

Introduction: Patellofemoral instability (PFI) is a disabling condition that occurs in adolescence. Recurrence after patellar dislocation has been reported in 2–50% of cases. This study aimed to compare the shape of the distal femur in PFI to a normal cohort.

Method: 108 CT scans from 54 subjects with PFI were compared to 197 CT scans from 102 normal subjects. Outlines of the trochlear groove and lateral condyle were extracted from CT scans using Interactive Data Language version 5.0 image manipulation software. The shapes were aligned using a modified Procrustes analysis and interpolation performed with a basic cubic spline. A statistical method from the field of functional data analysis was used to quantify shape. A discriminant analysis was then used to provide a tool for deciding which patients had abnormal grooves thus improving patient selection for trochleoplasty.

Results: Mathematical quantification showed a significant difference at the 0.001 level using an independent t-test between the normal and PFI groups for the shape of the trochlear groove with PFI knees having a more complex shape than normal. The second largest source of variation is in the position of the trochlear groove minimum with respect to the coronal plane together with variation in the shape of the medial condyle. The trochlear groove is situated more medially, with a shallower medial condyle, in PFI. In contrast the trochlear groove is situated more laterally, with a more prominent medial condyle in normal knees. Analysis of shape of the lateral condyle showed that in PFI, it is shorter and broader.

Conclusion: Principal components analysis can be used to quantify the variation in shape of the distal femur and allow a discriminant function analysis to be performed comparing PFI knees to normal knees. This quantification of shape can be applied to diagnosis of instability, operative planning for trochleoplasty and implant design.