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Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XVII | Pages 11 - 11
1 May 2012
Hossain M Parfitt D Beard D Darrah C Nolan J Murray D Andrew J
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Introduction

Preoperative psychological distress has been reported to predict poor outcome and patient dissatisfaction after total hip replacement (THR). We investigated this relationship in a prospective multi-centre study between January 1999 and January 2002.

Methods

We recorded the Oxford Hip Score (OHS) and SF36 score preoperatively and up to five years after surgery and a global satisfaction questionnaire at five year follow up for 1039 patients. We dichotomised the patients into the mentally distressed (Mental Health Scale score - MHS <50) and the not mentally distressed (MHS (50) groups based on their pre-operative MHS of the SF36. 776 (677 not distressed and 99 distressed) out of 1039 patients were followed up at 5 years.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_II | Pages 65 - 65
1 Feb 2012
Cvitanich M Bowers A Darrah C Spratt M Lui D Tucker J
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We aimed to assess whether using long stem femoral components, with cemented distal fixation and proximal impaction grafting allows early patient mobilisation, reconstitution of the proximal femur and long term stability of fixation in patients with aseptic loosening and proximal femoral analysis.

Over the past ten years 239 patients have been treated with an Elite Plus cemented long stem femoral implant, 33% with concomitant proximal impaction bone grafting. Many of the patients had co-morbidities. The average age at revision was 72 years (range 48 to 91). There was a slight female predominance. Fourteen percent of hips had been previously revised. Forty-eight patients were deceased and 22 were not available for follow-up; this left a cohort of 169 patients who were available for radiological and questionnaire review at an average of 4.5 years.

According to the Paprosky grading for pre-operative bone loss 40% had moderate to severe bone loss (grade IIIb or IV). The Barrack grading was used to assess the cement mantle post-operatively with 65% showing good cementation. The Harris and O'Neill grades were used at final review to assess probability of loosening with only 8% being probably or definitely loose. The average Oxford Hip Score was 29. Mesh ± cables were required in a third of cases to allow adequate containment and pressurisation. It was generally felt that the long stem needed to be at least one third longer than the initial component. The re-revision rate was 1.2 with a 10 year survivorship analysis of 94%. The complication rate of almost 6% included periprosthetic fractures, dislocations, infection and mesh breakage.

A long stem cemented femoral implant can be useful in bypassing proximal femoral deficiency in the appropriate patient.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_III | Pages 299 - 299
1 Jul 2011
Ollivere B Darrah C Evans-Gowing R Donell S Wimhurst J Clark I
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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.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_III | Pages 299 - 299
1 Jul 2011
Ollivere B Darrah C Howard D Walton N
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Introduction: The BOA recommends clinical and radiological arthroplasty follow up at one year then every five years. Increasing pressures placed on NHS Trusts with the implementation of the 18 week pathway and limitation on new:follow-up ratios has increased the use of patient reported outcome scores in arthroplasty follow-up. No single score is validated for this purpose, and there is no data surrounding their effectiveness as a screening tool for aseptic loosening.

Patients & Results: Patients undergoing their 10 year follow were included in the study and scored with the Harris (HHS), Hospital for Special Surgery (HSS), Merle d’Aubigne (MDA), Visual Analogue (VAS) or Oxford Hip Score (OHS) according to the unit’s established follow-up protocol. All patients underwent clinical and radiographic review in addition to scoring. Patients subsequently listed for revision surgery were defined as failure. Statistical analysis included significance testing and ROC analysis to determine the predictive value of the individual scores.

Four hundred and twelve patients were included in the study. The mean Harris, VAS and HSS were significantly different between the failed and well fixed groups. However there was no statistically significant difference between the mean Oxford and MDA scores. ROC analysis demonstrated the Harris (0.97), VAS (0.98) and HSS (0.77) score to have good prediction of outcome.

Discussion: The scores in our study have been validated as outcome measures for joint arthroplasty, however they perform differently in the follow-up setting. There is evidence that a failing hip is reflected in a poorer VAS, Harris, Oxford and HSS scores however the VAS was more sensitive and specific than any hip score. Patient administered outcomes have a place in the follow up of joint replacement it must be remembered they are validated as outcome measures, not for follow up purposes.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_I | Pages 41 - 42
1 Jan 2011
Harle D Ilyas S Tucker K Donell S Darrah C
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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 Journal of Bone & Joint Surgery British Volume
Vol. 92-B, Issue 11 | Pages 1501 - 1508
1 Nov 2010
Donell ST Darrah C Nolan JF Wimhurst J Toms A Barker THW Case CP Tucker JK

Metal-on-metal total hip replacement has been targeted at younger patients with anticipated long-term survival, but the effect of the production of metal ions is a concern because of their possible toxicity to cells. We have reviewed the results of the use of the Ultima hybrid metal-on-metal total hip replacement, with a cemented polished tapered femoral component with a 28 mm diameter and a cobalt-chrome (CoCr) modular head, articulating with a 28 mm CoCr acetabular bearing surface secured in a titanium alloy uncemented shell.

Between 1997 and 2004, 545 patients with 652 affected hips underwent replacement using this system. Up to 31 January 2008, 90 (13.8%) hips in 82 patients had been revised. Pain was the sole reason for revision in 44 hips (48.9%) of which 35 had normal plain radiographs. Peri-prosthetic fractures occurred in 17 hips (18.9%) with early dislocation in three (3.3%) and late dislocation in 16 (17.8%). Infection was found in nine hips (10.0%).

At operation, a range of changes was noted including cavities containing cloudy fluid under pressure, necrotic soft tissues with avulsed tendons and denuded osteonecrotic upper femora. Corrosion was frequently observed on the retrieved cemented part of the femoral component. Typically, the peri-operative findings confirmed those found on pre-operative metal artefact reduction sequence MRI and histological examination showed severe necrosis.

Metal artefact reduction sequence MRI proved to be useful when investigating these patients with pain in the absence of adverse plain radiological features.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_III | Pages 421 - 422
1 Jul 2010
Nickinson RSJ Darrah C Donell ST
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Aim: To determine the accuracy of clinical diagnosis in patients undergoing arthroscopic surgery of the knee.

Methods: A retrospective analysis of patients who had undergone knee arthroscopy at the Norfolk and Norwich University Hospital was performed from a prospectively gathered database. Pre-operative diagnosis was compared with operative diagnosis to determine the accuracy, sensitivity and specificity of the clinical diagnosis. The data was then analysed to determine how many patients underwent a beneficial procedure, which was defined as “a procedure from which the patient is likely to have benefited, either as a result of confirming the diagnosis or therapeutic intervention”. Finally, the results were compared with those from studies where the accuracy of MRI was assessed, to determine whether MRI is a more accurate diagnostic modality than clinical examination.

Results: The data of 698 patients was analysed. Of these 64% were male and 36% were female. The mean age at operation was 41 years (9 to 92). The overall accuracy, sensitivity and specificity of clinical diagnosis was 99%, 70% and 99% respectively. 90% of patients underwent a beneficial procedure, while 10% had a normal knee diagnosed at operation. Medial meniscal tear was the hardest pathology to diagnose, with accuracy, sensitivity and specificity rates of 82%, 92% and 79%. The results fell within the range of those found in studies, which examined the accuracy, sensitivity and specificity of MRI.

Conclusion: Our results show that clinical examination remains an accurate method of diagnosing intra-articular pathologies of the knee. Medial meniscal tear appears to be the hardest pathology to diagnose, and was the only condition with an accuracy rate under the 90th percentile. This is probably because medial tibio-femoral articular dysfunction has similar clinical findings. MRI was found to be no more effective than clinical examination at diagnosing pathologies of the knee.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_III | Pages 389 - 390
1 Jul 2010
Ollivere BJ Darrah C Barker T Nolan J Porteous M
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Introduction: As candidates for arthroplasty become younger and life expectancy increases the required working life of a total hip arthroplasty continues to rise. Hip resurfacing offers potential further advantages in young patients as minimal bone resection makes for easier revision, and the design allows for an increased range of movement. The Birmingham Hip Resurfacing (BHR) is the first of the second generation hip resurfacings.

Reports are beginning to emerge of unexplained failure, pseudotumour formation, individual cases of metallosis. Joint registry data also demonstrates an unexplained high early failure rate for all designs of hip resurfacing. This paper examines the rate and mode of early failures of the BHR in a multi-centre, multi-surgeon series.

Methods: All patients undergoing BHRs in our two centres were recruited prospectively into our arthroplasty follow up programme. Patients have been followed up radiographically and with clinical scores.

Results: Mean radiographic and clinical follow up was to 43 months (range 6 – 90 months). Of the 463 BHRs two have died and three are lost to follow up. Thirteen arthroplasties (2.8%) have been revised. Eight for pain, three for fracture, two for dislocation and one for sepsis. Of these nine were found to have macroscopic and histological evidence of metalloisis. Survival analysis at 5 years is 95.8% (CI 94.1 – 96.8%) for revisions and 96.9% (CI 95.5 – 98.3%) for metallosis.

Discussion: Histopathological examination demonstrated a range of inflammatory changes including necrosis, inflammation, ALVAL and metal containing macrophages. Not all features were associated with each patient and it is likely that these features form part of the spectrum of metal wear debris disease.

The likely rate of metallosis is 3.1% at five years. Risk factors for metallosis in this series are female sex, small femoral component, high abduction angle and obesity. We not advocate use of the BHR in patients with these risk factors.


The Journal of Bone & Joint Surgery British Volume
Vol. 91-B, Issue 8 | Pages 1025 - 1030
1 Aug 2009
Ollivere B Darrah C Barker T Nolan J Porteous MJ

The rate and mode of early failure in 463 Birmingham hip resurfacings in a two-centre, multisurgeon series were examined. Of the 463 patients two have died and three were lost to follow-up. The mean radiological and clinical follow-up was for 43 months (6 to 90).

We have revised 13 resurfacings (2.8%) including seven for pain, three for fracture, two for dislocation and another for sepsis. Of these, nine had macroscopic and histological evidence of metallosis. The survival at five years was 95.8% (95% confidence interval (CI) 94.1 to 96.8) for revision for all causes and 96.9% (95% CI 95.5 to 98.3) for metallosis.

The rate of metallosis related revision was 3.1% at five years. Risk factors for metallosis were female gender, a small femoral component, a high abduction angle and obesity. We do not advocate the use of the Birmingham Hip resurfacing procedure in patients with these risk factors.


The Journal of Bone & Joint Surgery British Volume
Vol. 91-B, Issue 6 | Pages 720 - 724
1 Jun 2009
Ollivere B Darrah C Brankin RC Donnell ST Walton NP

We report the follow-up at 12 years of the use of the Elite Plus total hip replacement (THR). We have previously reported the results at a mean of 6.4 years. Of the 217 patients (234 THRs), 83 had died and nine had been lost to follow-up. The patients were reviewed radiologically and clinically using the Oxford hip score.

Of the 234 THRs, 19 (8.1%) had required a revision by the final follow-up in all but one for aseptic loosening. Survivorship analysis for revision showed a survival of 93.9% (95% confidence interval (CI) 89.2 to 96.5) at ten years, and of 88.0% (95% CI 81.8 to 92.3) at 12 years. At the final follow-up survival analysis showed that 37% (95% CI 37.3 to 44.7) of the prostheses had either failed radiologically or had been revised. Patients with a radiologically loose femoral component had a significantly poorer Oxford hip score than those with a well-fixed component (p = 0.03). Radiological loosening at 6.4 years was predictive of failure at 12 years.

Medium-term radiographs and clinical scores should be included in the surveillance of THR to give an early indication of the performance of specific implants.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 531 - 531
1 Aug 2008
Nolan JF Darrah C Donell ST Wimhurst J Toms A Marshall T Barker T Case CP Peters C Tucker JK
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60 out of total series of 643 metal-on-metal hip replacements, carried out over the last nine years, have so far required revision, 13 for peri-prosthetic fracture and 47 for extensive, symptomatic, peri-articular soft-tissue changes.

Dramatic corrosion of generally solidly fixed, cemented stems has been observed and is believed to have resulted in the release of high levels of cobalt chrome ions from the stem surface. The contribution of the metal-to-metal articulation is, as yet, unclear.

Not including the fracture cases, plain films have demonstrated little or no abnormality to account for patients’ progressive symptoms. MRI scanning, on the other hand, utilising a technique designed to minimise implant artefact, has correlated very closely with findings at the time of revision surgery.

The histological changes, typified by extensive lymphocytic infiltration and a severe vasculitis leading to, in some cases, extensive tissue necrosis are demonstrated and discussed.

The failure of any of the existing protective mechanisms or regulatory restrictions to identify and limit the exposure of large numbers of patients to unsatisfactory implants has again been demonstrated.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_II | Pages 302 - 302
1 Jul 2008
Nolan J Darrah C
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A series of sixteen patients, 14 males and 2 females with an average age of 50 years (28–93) underwent total hip replacement surgery after acetabular fracture. Thirteen patients had previously undergone internal fixation of their acute fractures. Hip replacement surgery was performed by a single surgeon over an eight year period at an average of 30.36 (range 3–84) months after injury. Cases include high energy injuries as well as low energy fractures of the elderly (2 patients).

These were complex procedures due in some cases to the dramatic femoral head and acetabular bone stock loss when avascular necrosis had occurred following internal fixation. The use of acetabular mesh, allograft and reinforcement rings is discussed.

At the time of reporting the total hip replacements in this group of relatively young patients continue to be highly successful. One hip has been revised for recurrent dislocation.

This paper describes important surgical tips for the management of these complex cases. Removal of exposed metal work can be difficult. A role for MRI scanning in the early postoperative care following fracture fixation is postulated. The importance of early liaison of fracture fixation surgeons with arthroplasty colleagues leads to earlier surgery with reduction of bone stock loss.


The Journal of Bone & Joint Surgery British Volume
Vol. 90-B, Issue 4 | Pages 542 - 542
1 Apr 2008
OLLIVERE B DARRAH C WALTON N


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_II | Pages 259 - 259
1 May 2006
Smith RC Ainsworth B Varnier M Cooper A Darrah C Glasgow M
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Aim: To demonstrate that a multidisciplinary protocol reduces both in-patient stay and the need for out-patient physiotherapy following minimally invasive (MIS) uni-condylar knee replacements (UKR).

Methods: The data for hospital stay was collated for a consecutive group of primary UKR at our institution during 2002. We then compared this with a consecutive group of patients seen in a dedicated physiotherapist run clinic, with the provision of brochures and a “patient experience video”, with input from nurses, physiotherapists, anaesthetists, and surgeons, as well as time of expected discharge. The data was compared between informed (dedicated pre-operative assessment and patient video) and uninformed patients (standard pre-operative care).

Results: Total of 57 patients were initially assessed and compared with 81 patients after introduction of specific pre-op care pathway. Average hospital stay was reduced from 3.7 days to 2.1 days, with 60% going home within 24 hours.

Discussion: By changing the preconception of long hospital stays after arthroplasty ingrained in patients and staff we have reduced hospital stay significantly. Major factors contributing to this include the team approach, patient and ward staff education, perceptions of discharge and the inclusion of specific local anaesthetic techniques, and a minimally invasive approach. Delays in discharge include the geography of the region.


The Journal of Bone & Joint Surgery British Volume
Vol. 87-B, Issue 4 | Pages 458 - 462
1 Apr 2005
Walton NP Darrah C Shepstone L Donell ST Phillips H

We prospectively studied 217 patients who underwent 234 Elite Plus total hip arthroplasties. At a mean of 6.4 (SD 0.7) years post-operatively, 39 patients had died and 22 were either lost to follow-up or had no radiographs available. Clinical (Oxford hip score) and radiological assessments were performed on 156 patients (168 hip arthroplasties) who had a mean age of 67.7 (SD 9.7) years at operation.

In the assessed group, 26 of 159 (16.4%) of femoral stems which had not already been revised and 19 of 159 (11.9%) of acetabular cups were definitely loose. In total, 52 of 168 (31%) of hips had either been revised or had definite evidence of loosening of a component. We could not establish any relationship between clinical and radiological outcomes.

Despite the fact that the clinical outcome and rate of revision for the Elite Plus appeared to meet international standards, our findings give us cause for concern. We believe that joint registries should include radiological surveillance in order to provide reliable information about medium-term outcomes for hip prostheses.


Orthopaedic Proceedings
Vol. 85-B, Issue SUPP_II | Pages 158 - 158
1 Feb 2003
Nolan J Darrah C Fairman B Fleming J
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This prospective study evaluates the outcome of a new metal -on-metal total hip replacement in a younger group of patients.

Fifty-five primary all-metal total hip replacements (THR) were evaluated prospectively at a follow-up of 2.8–5.5 years. Patients were selected according to age and activity levels. The mean age was 58 years (41–69). 33 males and 22 females were included in the study. Surgery was carried out for osteoarthritis in 52 patients and for non-union fractured femoral neck, ankylosing spondilitis and post slipped upper femoral epiphysis in the three remaining patients. A single surgeon (the senior author) through the posterior approach carried out the surgery. All patients received the porous coated titanium shell with a Morse taper cobalt chrome liner and double wedge tapered polished cobalt chrome stem and modular head. Blood metal ion analysis was performed on a cohort of 24 patients using High Resolution Inductively Coupled Plasma Mass Spectrometry, sampling taken preoperatively and then repeated post operatively at 6 months, 1 year and then annually.

Clinical results have been excellent. X rays show Harris A cementation in all femurs, with no component migration or radiolucencies being identified on follow-up radiographs. No prosthesis to-date has required revision. One patient has died and one is lost to follow up. The following non-device related complications were reported in the group, 2 (4%) superficial wound infections, 1 (2%) dislocation, 1 (2%) thrombosis, 1 (2%) IT band defect and 2 (4%) impingement. The dislocation was treated with a closed reduction. The impingement has resolved by one year in both patients. The results of the pre and postoperative blood metal ion analysis demonstrate some elevated levels, these levels being similar to those previously reported in the literature.

The hybrid all-metal THR may represent a valuable alternative in the younger, high demand patient.


Orthopaedic Proceedings
Vol. 85-B, Issue SUPP_I | Pages 64 - 64
1 Jan 2003
Nolan J Darrah C
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Fifty five primary Ultima® hybrid all-metal (Johnson & Johnson Professional DePuy) total hip replacements (THR) were evaluated prospectively at a mean follow up of 24 months. Patients were selected according to age and activity levels. The mean age at surgery was 58 years (41–69 years). 33 males and 22 females were included in the study. Surgery was carried out for osteoarthritis in 52 patients and for non-union fractured neck of femur, ankylosing spondilitis and post slipped upper femoral epiphysis in the three remaining patients. A single surgeon (the senior author) through the posterior approach carried out surgery. All patients received the Ultima® porous coated titanium shell with a morse taper cobalt chrome liner and double wedge taper polished stem and modular head. Blood metal ion analysis was performed on a cohort of 24 patients using High Resolution Inductively Coupled Plasma Mass Spectrometry, sampling taken pre operatively and then repeated post operatively at 6 months, 1 year and then annually.

Clinical results reported at a mean follow-up interval of 2.016 years have been excellent, with no prosthesis to-date requiring revision and no component migration or radiolucuencies being identified on any follow-up radiographs. One patient has died and one is lost to follow-up. The following non-device related complications were reported in the group, 2 (4%) superficial wound infections, 1 (2%) dislocation, 1 (2%) thrombosis, 1 (2%) IT band defect and 2 (4%) impingement. The dislocation was treated with a closed reduction, the position of the component having been judged as satisfactory. The impingement has resolved by one year in both patients. The results of pre and postoperative blood metal ion analysis in a cohort of 24 patients demonstrate some elevated levels, these levels are similar to those previously reported in the literature.

The Ultima® hybrid all-metal THR may represent a valuable alternative in the younger, high demand patient.


Orthopaedic Proceedings
Vol. 84-B, Issue SUPP_II | Pages 157 - 158
1 Jul 2002
Davies A Bayer J Owen-Johnstone S Darrah C Shepstone L Glasgow M Donell S
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A prospective clinical investigation to determine the optimum knee flexion angle for the ‘skyline’ patellofemoral joint radiograph.

Plain radiography of the patello-femoral joint includes the axial or ‘skyline’ radiograph. The optimum knee flexion angle for making this image remains unclear.

We therefore performed a prospective clinical study in which patients underwent three skyline radiographs with knee flexion angles of 30(or minimal flexion), 50 and 90 degrees. The patients were new patients, aged between 12 and 30, presenting to a knee clinic with anterior knee pain. Two observers evaluated the radiographs, making a standardised series of measurements. Blinding was organised so that the observers were unable to use any information other than the radiographic image alone. One observer evaluated all the films on two separate occasions to allow calculation of intra- and interassessor agreement.

There were 67 knees from 46 patients. There was a high level of intra- and inter-observer agreement. There were a number of patients in which the radiographic appearance of the patello-femoral varied markedly between the different views; in all cases the abnormality was best demonstrated by the 30-degree view. There were however a number of minimal flexion views in which the film contained incomplete information because part of the patello-femoral joint was missing from the image.

We conclude that whilst a minimal flexion skyline view is the most sensitive method for the detection of patellar tilt and subluxation, not all knees can be successfully imaged at the required position. A flexible approach is therefore needed, to obtain satisfactory images at minimal flexion.