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Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_13 | Pages 75 - 75
7 Aug 2023
Mackay N Bausch N McGoldrick N Krishnan H Shah F Smith N Thompson P Metcalfe A Spalding T
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Abstract

Background

Osteochondral allograft (OCA) transplantation is a clinically and cost-effective option for symptomatic cartilage defects. In 2017 we initiated a program for OCA transplantation for complex chondral and osteochondral defects as a UK tertiary referral centre.

Aim

To characterise the complications, re-operation rate, graft survivorship and clinical outcomes of knee OCA transplantation.


The Bone & Joint Journal
Vol. 104-B, Issue 6 | Pages 657 - 662
1 Jun 2022
Barlow T Coco V Shivji F Grassi A Asplin L Thompson P Metcalfe A Zaffagnini S Spalding T

Aims

Meniscal allograft transplantation (MAT) for patients with symptomatic meniscal loss has demonstrated good clinical results and survivorship. Factors that affect both functional outcome and survivorship have been reported in the literature. These are typically single-centre case series with relatively small numbers and conflicting results. Our aim was to describe an international, two-centre case series, and identify factors that affect both functional outcome and survival.

Methods

We report factors that affect outcome on 526 patients undergoing MAT across two sites (one in the UK and one in Italy). Outcomes of interest were the Knee injury and Osteoarthritis Outcome Score four (KOOS4) at two years and failure rates. We performed multiple regression analysis to examine for factors affecting KOOS, and Cox proportional hazards models for survivorship.


Bone & Joint 360
Vol. 10, Issue 2 | Pages 5 - 16
1 Apr 2021
Coco V Shivji F Thompson P Grassi A Zaffagnini S Spalding T


The Bone & Joint Journal
Vol. 100-B, Issue 1 | Pages 56 - 63
1 Jan 2018
Smith NA Parsons N Wright D Hutchinson C Metcalfe A Thompson P Costa ML Spalding T

Aims

Meniscal allograft transplantation is undertaken to improve pain and function in patients with a symptomatic meniscal deficient knee compartment. While case series have shown improvements in patient reported outcome measures (PROMs), its efficacy has not been rigorously evaluated. This study aimed to compare PROMs in patients having meniscal transplantation with those having personalized physiotherapy at 12 months.

Patients and Methods

A single-centre assessor-blinded, comprehensive cohort study, incorporating a pilot randomized controlled trial (RCT) was performed on patients with a symptomatic compartment of the knee in which a (sub)total meniscectomy had previously been performed. They were randomized to be treated either with a meniscal allograft transplantation or personalized physiotherapy, and stratified for malalignment of the limb. They entered the preference groups if they were not willing to be randomized. The Knee injury and Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC) score and Lysholm score and complications were collected at baseline and at four, eight and 12 months following the interventions.


The Bone & Joint Journal
Vol. 100-B, Issue 1 | Pages 64 - 65
1 Jan 2018
Smith NA Parsons N Wright D Hutchinson C Metcalfe A Thompson P Costa ML Spalding T


The Bone & Joint Journal
Vol. 99-B, Issue 7 | Pages 904 - 911
1 Jul 2017
Wall PDH Sprowson† AP Parsons NR Parsons H Achten J Balasubramanian S Thompson P Costa ML

Aims

The aim of this study was to compare the effectiveness of a femoral nerve block and a periarticular infiltration in the management of early post-operative pain after total knee arthroplasty (TKA).

Patients and Methods

A pragmatic, single centre, two arm parallel group, patient blinded, randomised controlled trial was undertaken. All patients due for TKA were eligible. Exclusion criteria included contraindications to the medications involved in the study and patients with a neurological abnormality of the lower limb. Patients received either a femoral nerve block with 75 mg of 0.25% levobupivacaine hydrochloride around the nerve, or periarticular infiltration with 150 mg of 0.25% levobupivacaine hydrochloride, 10 mg morphine sulphate, 30 mg ketorolac trometamol and 0.25 mg of adrenaline all diluted with 0.9% saline to make a volume of 150 ml.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_6 | Pages 35 - 35
1 Feb 2016
Mellor F Breen A Thomas P Thompson P
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Purpose and Background:

To compare static and dynamic lumbar intervertebral ranges of motion (IV-RoM) in patients with chronic, nonspecific low back pain with upper and lower cut off values derived from healthy controls when variability and measurement errors were reduced.

Measurements from functional radiographs suffer from high variability and measurement errors, making cut off values for excessive or insufficient motion problematical. This study compared maximum lumbar IV-RoM and maximum IV-RoM at any point in continuous motion sequences in patients with chronic, non-specific back pain with upper and lower cut off values for L2 to L5 from matched controls using quantitative fluoroscopy, where variation and measurement errors were reduced.

Methods and Results:

Participants underwent passive recumbent examinations in the sagittal and coronal planes. Values based on were developed for both maximum and continuous motion in controls (n=40). Fishers exact test was used to analyse proportions of patients whose IV-RoMs exceeded reference values.

For maximum IV-RoM in patients, there were no statistically significant differences between groups for the lower value. Only flexion at L4/5 significantly exceeded the upper value (p=0.03). For continuous IV-RoM, left L3/4 (p=0.01) and right L4/5 (p=0.01) were significantly below the lower cut off values. Both flexion L4/5 (p=0.05) and left L3/4 (p=0.01) were significantly above the upper cut off values.


Bone & Joint Research
Vol. 4, Issue 6 | Pages 93 - 98
1 Jun 2015
Smith NA Achten J Parsons N Wright D Parkinson B Thompson P Hutchinson CE Spalding T Costa ML

Objectives

Subtotal or total meniscectomy in the medial or lateral compartment of the knee results in a high risk of future osteoarthritis. Meniscal allograft transplantation has been performed for over thirty years with the scientifically plausible hypothesis that it functions in a similar way to a native meniscus. It is thought that a meniscal allograft transplant has a chondroprotective effect, reducing symptoms and the long-term risk of osteoarthritis. However, this hypothesis has never been tested in a high-quality study on human participants. This study aims to address this shortfall by performing a pilot randomised controlled trial within the context of a comprehensive cohort study design.

Methods

Patients will be randomised to receive either meniscal transplant or a non-operative, personalised knee therapy program. MRIs will be performed every four months for one year. The primary endpoint is the mean change in cartilage volume in the weight-bearing area of the knee at one year post intervention. Secondary outcome measures include the mean change in cartilage thickness, T2 maps, patient-reported outcome measures, health economics assessment and complications.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_12 | Pages 42 - 42
1 Mar 2013
Subbu R Nandra R Patel D McArthur J Thompson P
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In August 2007 NICE issued its guidance for the treatment of patients with knee osteoarthritis (OA) with arthroscopic lavage. The recommendations stated that referral for arthroscopic lavage and debridement should not be offered as part of treatment for osteoarthritis, unless the person has osteoarthritis with a clear history of ‘mechanical locking’ (not gelling, giving way, or x-ray evidence of loose bodies). The aim of this study was to assess both the application of these guidelines over a four month period and whether this procedure had improved symptoms at first follow-up.

This was a retrospective review from August-December 2011. The total number of arthroscopies performed during this period was obtained from theatre records. Further data was obtained through the hospital's electronic database. The diagnosis of OA was made through the analysis of referral and clinic letters, plain radiographs, MRI reports and operation notes. Only those patients with persisting OA symptoms were included, those with OA and recent history of injury or trauma were excluded. During this time period, 222 knee arthroscopies were performed in total, 99 were identified with persistent OA symptoms.

Having identified these patients, referral letters were further analysed to identify the initial presenting symptom. Of the 99, 50 presented with pain, 28 presented with pain plus another symptom other than locking e.g. stiffness/swelling/giving-way, 21 presented with pain plus mechanical locking. According to current guidelines only these 21 patients should have been offered arthroscopic lavage as a form of treatment. In addition to these findings we identified what procedures had been carried out during arthroscopy for each symptom. Of those presenting with pain, 82% had a washout and debridement, 8% had washout, 4% had partial medial meniscectomy, 4% had lateral patellar release and 2% had partial lateral meniscectomy. Those with pain plus other symptoms not including locking, 82% had washout and debridement, 11% had partial medial meniscectomy, and 7% had a washout. Of those presenting with pain plus mechanical locking, 81% had washout and debridement and 19% had partial medial meniscectomy.

Following the procedure, we analysed the outcome of symptoms at first-follow up. The mean follow-up time was 8 weeks. Of those presenting with just pain, 44% showed improvement, 52% had no change/on-going symptoms, 2% were unknown. Of those with pain plus other symptoms other than locking, 57% showed improvement, 35% had no change/on-going symptoms, 8% unknown. Of those with pain plus mechanical locking, 80% showed improvement, 10% had no change/on-going symptoms, 10% unknown.

The results of this study support the current evidence that unless there are clear mechanical symptoms of locking, the use of arthroscopy in arthritic knee joints should be judicious and the reasons should be clearly documented.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_8 | Pages 5 - 5
1 Feb 2013
Wood T Getgood A Smith N Spalding T Thompson P
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We reviewed all patients that suffered a deep infection following anterior cruciate ligament (ACL) repair kept between January 2007 and April 2011 at our teaching hospital NHS trust, and the two local private hospitals.

18 patients were identified. All patients underwent at least 2 arthroscopic washouts, with limited synovectomy if required. Targeted antibiotics were commenced according to the culture results, and following microbiological advice. These patients were reviewed at a minimum of 1 year following eradication of infection (range 12–46 months). There were 7 surgeons performing the ACL reconstructions.

The primary outcome measure was graft failure requiring revision. Our secondary outcome measures were a history of ongoing instability, KT 1000™ measurement, Tegner and Lysholm outcome scores. There were 18 patients identified as having suffered infection after ACL infection (mean age 24.3 years, range 15–38 years). Average C Reactive Protein (CRP) was 217 on admission (range 59–397). The most common organism isolated was coagulase negative staphylococcus in 47.3% of cases. There were 3 graft failures within the infection group. Of the remaining 15 patients there were no episodes of ongoing instability and mean pivot shift grade was 1.1, mean KT 1000™ side-to- side difference was +1.8mm. There was a reported drop on the Tegner activity score of 1.75 (range 0–6) and mean Lysholm score was 89 (range 56–100).

The failure rate is slightly higher than that reported in the literature. Patient reported outcome measures in the patients are broadly consistent. We recommend an aggressive approach to the treatment of deep infection following ACL reconstruction, in order to achieve a satisfactory outcome.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXIX | Pages 75 - 75
1 Jul 2012
Bird J Carmont M Dalton H Crane T Clewer G Dhillon M Thompson P Spalding T
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Purpose

To critically evaluate exciting new technology to reconstruct menisci for the treatment of post menisectomy pain and relate results to indication and surgical technique in a non-inventor's general knee practice.

Methods

We present our early experience of two non-comparative series with different meniscal implants.

Series 1: Thirteen patients received a Menaflex implant (Regen Bio, USA). Mean age 30, male/female 11/2, mean length of implant 44mm, mean chondral grade 1.9 (Outerbridge). At 24 months clinical scores showed improvement in 12. Second look arthroscopy in 5 however showed disappointing amounts of regenerative tissue. One patient has been revised.

Series 2: Twelve patients received an Actifit implant (Orteq, UK). Mean age 38, male/female 8/4, mean length implant 43 mm, mean chondral grade 1.3. At 12 months all have improved clinical scores. We have performed two second looks, one of these showed excellent integration. However one showed only 50% regeneration. Critical review of the initial implantation shows that there may not have been adequate preparation of the host meniscus tissue.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_IX | Pages 40 - 40
1 Mar 2012
Spalding T Thompson P Clewer G Bird J Smith N Dhillon M
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Hypothesis

Recent advances in understanding of ACL insertional anatomy has led to new concepts of anatomical positioning of tunnels for ACL reconstruction. Femoral tunnel position has been defined in terms of the lateral intercondylar ridge and the bifurcate ridge but these can be difficult to identify at surgery. Measurements of the lateral wall either using C-arm x-ray control or specific arthroscopic rulers have also been advocated.

Method

30 patients undergoing ACL reconstruction before and after introduction of a new anatomical technique of ACL reconstruction were evaluated using 3D CT scan imaging with cut away views of the lateral aspect of the femoral notch and the radiological quadrant grid. In the new technique, with the knee at 90 degrees flexion, the femoral tunnel was centred 50% from deep to shallow as seen from the medial portal (Group A). Group B consisted of patients where the femoral tunnel was drilled through the antero-medial portal and offset from the posterior wall using a 5mm jig.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_IX | Pages 91 - 91
1 Mar 2012
Smith N Dhillon M Thompson P
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Introduction

There are numerous surgical techniques for medial patellofemoral ligament (MPFL) reconstruction. Problems with certain techniques include patellar fracture and re-rupture.

Aim

To investigate the functional outcomes of MPFL reconstructions performed using a free gracillis tendon graft, oblique medial patella tunnel and interference screw femoral fixation. Patients were selected for MPFL reconstruction if they had recurrent patellar dislocations, and with the use of clinical and radiographic evaluation.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_IX | Pages 92 - 92
1 Mar 2012
Smith N Dhillon M Thompson P
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Introduction

Current problem – Multiple surgical interventions for patellar instability and no defined criteria for use of medial patellofemoral ligament (MPFL) reconstruction.

Aims

Investigate the functional outcomes of MPFL reconstructions that had been performed following selection for treatment based on a defined patellar instability algorithm.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_I | Pages 13 - 13
1 Jan 2011
Saithna A Carey-Smith R Thompson P Dhillon M Spalding T
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We aim to assess the clinical and radiological outcome following cartilage repair in the knee using the TruFit plug (Smith & Nephew). Eleven active sporting patients underwent cartilage repair using TruFit plugs between February 2006 and August 2007. Postoperatively patients were touch weight bearing for 2 weeks and partial until 4 weeks.

Data was collected prospectively, patients underwent clinical review and completed Lysholm, IKDC subjective, Tegner, KOOS and SF-36 scores pre-operatively and at 6 monthly intervals. One patient has been excluded from the analysis as she emigrated and was lost to follow up. The remaining 10 patients (mean age 35 years (21–49)) had defects on the medial femoral condyle (n=6), lateral femoral condyle (n=3), and lateral trochlea (n=1). Patients received one (n=5), two (n=3) or three (n=2) plugs and four were primary procedures, and six revision procedures (1 failed OATS, 5 failed microfracture). Eight implantations were performed arthroscopically and, and two were mini-open. All patients were reviewed at 12 months, five were reviewed at 18 months and four have also been reviewed at 24 months.

Statistically significant improvements from mean pre-operative scores are seen at 12 months; Lysholm (48.3 to 71), IKDC Subjective (37.7 to 65.1), Tegner (2.4 to 4.6), SF36 physical (39.5 to 50.3) and all components of KOOS. These improvements are maintained at the latest follow up. MRI evaluation including T2 mapping demonstrates reformation of the subchondral lamina, resorption of the graft and a similar signal from neo-cartilage as that of adjacent native cartilage.

TruFit plugs offer an exciting novel solution for cartilage repair in the knee with advantages of low morbidity and rapid recovery without the need for prolonged non-weight bearing. The implant may be suitable for small lesions only and further prospective study is required to establish long-term outcome.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_III | Pages 412 - 412
1 Jul 2010
Makrides P Carmont M Dhillon M Thompson P Spalding T
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Purpose: To report on our early experience with a synthetic meniscal substitute inserted for symptomatic post meniscectomy medial or lateral knee pain.

Methods and results: Six patients underwent underwent insertion of a collagen meniscal implant (Menaflex, Hospital Innovations, UK). These were inserted onto a trephinated rim of vascular meniscus to permit the structural incorporation of healing tissue. Specific rehabilitation included 8 weeks on crutches and restricted activity for 6 months. Patients were prospectively analysed documenting KOOS, IKDC, Lysholm and SF36 outcome scores.

All patients were male, 4 patients had deficiencies in the right knee, 2 the left knee and the mean patient age was 28.8years (range 17–45). Four CMI were inserted for lateral meniscal deficiencies, two medial. The mean length of implant sutured in place was 41mm (range 35–55). Median pre op scores were KOOS P/S/ADL/QOL 53/100, 54/100, 66/100, 25/100, 44/100, IKDC 49.43%, Tegner 3, SF-36 35.38 PCS and 27.48 MCS and Lysholm 87/100. The mean elapsed time post meniscectomy was 20 months (range 2–51). All but one of the implants used were 9.5mm in width and sizes ranged 35–45mm.

At early follow up there have been no complications and background pain has improved in all 6. MIR imaging has shown that none have separated. Post operative follow up suggest improved outcome.

Conclusion: Though this is very early data, close scuritny of new treatment options is essential. So far the clinical outcome is favourable and we believe that CMI may be beneficial in reducing post menisectomy pain. Hopefully, in the future CMI may become a means of preventing post meniscectomy osteoarthrtitis.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_III | Pages 423 - 423
1 Jul 2010
Saithna A Dunne K Kuchenbecker T Thompson P Dhillon M Spalding T
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Aim: To relate clinical progress following cartilage repair using TruFit plugs with appearance on MRI imaging with a view to determining safe healing in order for patients to return to activity, without needing invasive assessment.

Methods: 26 active sporting patients underwent cartilage repair using TruFit CB plugs (Smith & Nephew) for symptomatic chondral defects in the knee between February 2006 and September 2008. The plugs are a biphasic synthetic implant designed to reform both bone and articular cartilage. As part of this prospective series patients underwent MRI at post op time-points of 6, 12, 18 and 24 months. MRI was performed using a 1.5 Tesla scanner and later using a 3T scanner. We report the results of both including T2 cartilage mapping.

Results: All 26 patients were improved at latest follow-up when compared to pre-operative scores (mean follow up 15 months (range 6–30 months)). MRI evaluation demonstrates oedema like signal surrounding the plugs at an early stage but by 6 months the oedema resolves and the subchondral lamina is seen to reform. By 12 months the bone part of the plug has similar appearance to host bone and the neo-cartilage shows similar signal to native cartilage on all MRI modalities (1.5T, 3T and T2 mapping). This suggests that the repair tissue contains a high percentage of hyaline like cartilage. In one patient slow clinical improvement was reflected in the MRI appearance.

Conclusion: MRI imaging appears to relate to clinical improvement according to KOOS, IKDC, Lysholm, Tegner and SF36 scores. This indicates that MRI is a useful imaging tool for assessing healing, and knowledge of the recovery pattern is important for quantifying healing and for better advising patients on when it may be safe to load repaired areas.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_III | Pages 415 - 415
1 Sep 2009
Saithna A Smith RC Thompson P Dhillon M Spalding T
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Aim: To assess the safety and clinical and radiological outcome of the TruFit CB porous, resorbable scaffold for symptomatic osteochondral and chondral articular defects in the knee.

Methods: 11 active sporting patients underwent cartilage repair using TruFit CB plugs (Smith & Nephew) for symptomatic defects on the medial or lateral femoral condyle. All had failed previous treatment (debridement/microfracture) and had persistent symptoms. Postoperatively patients were touch weight bearing for 2 weeks and partial until 4 weeks. Data was collected prospectively. The mean age was 34 (range 19 – 50) and 5 were male. Four lateral femoral condyle defects were treated, all associated with lateral meniscal tears. Four medial defects were associated with ACL injury (1), PCL injury (1) or isolated chondral injury (2). Single plugs were required in 5 (9mm in 3 and 7mm plugs in 2), 2 patients required 2 plugs (9mm and 7mm), and 2 required 3 (2×9mm + 1×7mm).

Results: All 11 patients were improved at a mean follow up of 14.5 months (3–21 months) with 4 currently back to full pre-injury level of sport. Subjective IKDC scores improved from 45 pre-op to 79 post-op (p< 0.05), Lysholm from 47 to 71 (p< 0.05), and latest Tegner activity score at 5. MRI evaluation including T2 mapping demonstrates reformation of the subchondral lamina and resorption of the graft. 2nd look arthroscopy was undertaken in 2 showing a well healed and well integrated surface.

Conclusion: These preliminary results indicate that TruFit CB plugs offer a potential solution for small focal chondral defects, offering an alternative to microfracture or osteochondral grafting with advantages of low morbidity and rapid recovery without the need for prolonged non-weight bearing.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_III | Pages 421 - 421
1 Sep 2009
Cooper LA Mauffrey C Carey-Smith R Thompson P Spalding T
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The purpose of this study was to assess the accuracy of a modified version of the pivot shift test in detecting ruptures of the anterior cruciate (ACL) ligament.

Methods: Two groups of patients aged 18 to 50 years were recruited from operating theatre lists examined at a check and consent clinic. One of the groups had ACL deficient knees and the control group had intact ACL, later proven at arthroscopy. A total of 48 independent examinations, 26 with ACL rupture and 22 without, were undertaken by a consultant or registrar proficient in the modified version of the pivot shift test. At the start of the consultation the examiner, who was blinded to the operation that the patient was listed for and to the patient’s history, performed the modified pivot shift test only. The result of the test was reported as positive or negative for ACL rupture to the study co-ordinator before the examiner continued with the consultation.

Results: Of the 26 examinations of ACL deficient knees, 22 were reported as positive and four negative for ACL rupture using the pivot shift test only. Of the 22 examinations of ACL intact knees one was reported as positive for ACL rupture and 21 as negative. This gives a specificity and sensitivity of the modified version of the pivot shift test as 95.5% (95% CI 75.1–99.8%) and 84.6% (95%CI 64.3–95.0%) respectively.

Conclusion: The modified pivot shift test is an accurate test for the detection of ACL rupture. Our modified pivot shift test compares favourably with data from previous accuracy studies of previously described versions of the pivot shift test. We now plan to assess the accuracy of the modified pivot shift test when carried out by medical students and junior doctors.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_III | Pages 416 - 416
1 Sep 2009
Saithna A Smith RC Thomas M Thompson P Spalding T
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Aim: To assess the results and complications of the opening wedge form of distal femoral varus osteotomy (DFVO) in treating valgus arthritis and ligament instability of the knee.

Methods: Patients undergoing DFVO were assessed prospectively using validated scoring systems and pre/post operative alignment radiographs. All had failed non operative and arthroscopic procedures and were keen to avoid arthroplasty. The lateral based opening wedge osteotomy aimed to correct the weight bearing line to position 50% medial to lateral and was held with either the Puddu femoral plate (Arthrex UK) or the Tomofix plate (Synthes UK).

Results: 26 distal femoral osteotomies were performed in 23 patients with a mean age of 34 (16 –58). The mean duration of follow up is 32.5 months (1–72). 8 were undertaken for primary valgus malalignment, and 15 for secondary valgus with OA due to previous lateral menisectomy. Simultaneous additional procedures included microfracture (3), MACI (1), meniscal transplantation (1), and MCL advancement (1). Mean hospital stay was 4 days (2–6). Post op alignment was out by greater than 10% of intended in 2/3. 3 early major complications required re-operation: 2 for plate and screw cut out and 1 for infection. 2 developed delayed union requiring bone grafting. Failure with conversion to arthroplasty has occurred in 2 (1 lateral UKA, 1 TKA), and 2 patients are awaiting either multi-ligament reconstruction or collagen meniscal implantation. The overall mean Tegner score is 4 (2–6), and 20 of the 23 patients feel satisfied with the outcome having avoided arthroplasty.

Conclusion: Opening wedge DFVO is a technically difficult procedure with significant complications, but in the right indication offers long lasting pain relief and joint preservation prior to arthroplasty. New techniques including accurate closing wedge fixation systems and computer guided operative planning and surgery may offer improvements to this vital surgical option.


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_III | Pages 377 - 377
1 Oct 2006
Joyce T Monk D Thompson P Chiu P Unsworth A Green S
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Introduction: The wear of orthopaedic biopolymers is recognised as a major factor in the failure of total joint replacements. Clinical wear data exists for acetabular cups manufactured from three biopolymers: ultra high molecular weight polyethylene (UHMWPE); poly tetra fluoro ethylene (PTFE); and polyacetal. The aim of this paper was to wear test these biopolymers and compare the results with clinical data.

Method and Materials: The biopolymers were tested using a modified, four-station, pin-on-plate wear rig [1]. In the tests, two of the four stations applied reciprocating motion and two applied multi-directional motion. Biopolymer pins articulated against stainless steel plates under a load of 40N. The lubricant consisted of 25% bovine serum and 75% distilled water. A standardised cleaning and weighing protocol was followed, and the biopolymer wear factors were calculated by dividing the volume lost by the product of the load and the sliding distance.

Discussion and Conclusions: Failed and retrieved UHMWPE acetabular cups have been reported as having a clinical wear factor of 2.1 x 10−6mm3/Nm [2]. However, UHMWPE cups which have been functioning well until removal at post-mortem have been said to show 45 to 69% less wear than revised UHMWPE cups [3]. Combining these values suggests clinical wear factors for functional UHMWPE in the range of 0.95 to 1.45 x 10−6mm3/Nm. This range fits well with the value of 1.1 x 10−6mm3/Nm shown in table 1 for UHMWPE under multi-directional motion. A clinical wear factor of 37 x10−6mm3/Nm has been calculated for PTFE acetabular cups [4]. When compared with the mean wear factor for PTFE pins under multi-directional motion obtained from the pin-on-plate rig, the match is remarkable. For polyacetal cups a mean volumetric wear of 136mm3/ year has been reported [5] and it has been calculated that explanted hip prostheses averaged 1.54 million cycles/year [2]. In polyacetal acetabular cups of 37mm diameter, an average sliding distance of 25mm/cycle can be calculated [6] and it has been said that an equivalent static load of 1000N applies [7]. Taking these four values permits a clinical wear factor for polyacetal cups of 3.5 x 10−6mm3/Nm to be calculated. This number compares well with the value of 3.8 x 10−6mm3/Nm seen for the polyacetal test pins under multi-directional motion. In summary, all three biopolymers subject to multi-directional motion exhibited clinically relevant values of wear.


The Journal of Bone & Joint Surgery British Volume
Vol. 61-B, Issue 4 | Pages 474 - 480
1 Nov 1979
Tayton K Thompson P

The operation of soft-tissue release and calcaneocuboid fusion, published by Dillwyn Evans in 1961, is described in detail and a long-term review of 118 club feet is presented. The average age of the patients at review was nearly seventeen years. All were resistant cases and in all the Dillwyn Evans "collateral operation", deliberately delayed by a policy of prolonged conservative treatment, had been the main surgical procedure.