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Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_12 | Pages 2 - 2
1 Jun 2017
Crainic A Callisti M Palmer M Cook R
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Metallic contacts in hip replacements are susceptible to wear and corrosion processes which lead to the release of particles and metal ions. Adverse local tissue reactions (ALTRs) and systemic manifestations to solid and soluble debris can be debilitating for the patients. It is believed that particles originating from CoCrMo taper junctions trigger more severe body reactions compared to debris from MoM hip bearings. The body's reaction is highly dependent on particle characteristics, such as size, morphology, composition and aggregation state, which can reflect the specific wear and corrosion conditions at the site of release.

Here we proposed to investigate wear and corrosion flakes collected from around CoCrMo tapers at the time of revision. The particles were initially characterised with scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). This revealed the microstructure of the corrosion products, which appeared to be made of smaller metallic aggregates, entrapped in a biological matrix. The in depth characterisation of the particles released from the organo-metallic composite, was performed with transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM), both fitted with EDX. The investigation revealed clusters and individual nanoparticles, as small as 3 nm, which represent the building blocks of the large corrosion flakes, reported and characterised in the past mainly with low resolution microscopy techniques. The majority of the particles consisted of Cr and O, potentially in the form of chromium oxides, with little evidence of Co and Mo. Particles size distribution (PSD) provided by STEM and TEM characterisation showed statistically different results. The STEM technique was able to resolve tiny particles found in close proximity and provided a PSD shift towards the smaller end of the size range.

The study is the first to show microscopy evidence of Cr rich nanoparticles (3–60 nm) released in vivo from the modular taper interface, which can have important health implications caused by their increased potential to disseminate and corrode within the body.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_11 | Pages 8 - 8
1 Jun 2016
Cook R Bolland B Tilley S Latham J
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Using a femoral head from one manufacturer on the stem of another manufacturer poses the risk that the taper interface between the components do not contact correctly and the performance of the joint will be impaired. The cohorts in this study are a combination of modular Birmingham Hip Resurfacing (BHR) and Adept femoral heads on CPT stems. The study reviews the geometry of the taper interfaces to establish if the taper clearance angles was outside of the normal range for other taper interfaces. In addition the rates of material loss from the bearings and taper and a ranking of the stem damage were reviewed to determine if the levels of loss were above that seen for other similar joints.

The material loss analysis demonstrated that the rates or levels of loss from the bearings, taper and stem are no different to levels published for manufacturer matched joints and in many cases are lower. The results demonstrate that the taper clearance angles for the mixed manufacturer joints (BHR-CPT: 0.067 to −0.116, Adept-CPT: 0.101 to −0.056) were within the range of other studies and manufacturer matched clearances (0.134 to −0.149).

Using components from different manufacturers has not in this instance increased the level of material loss from the joints, when compared to other similar manufacturer matched joints.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_34 | Pages 388 - 388
1 Dec 2013
Latham J Cook R Bolland B Wakefield A Culliford D Tilley C
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Introduction

Metal on metal hip arthroplasty continues to be controversial. Emerging evidence suggests that there are multiple modes of failure, and that the results of revision surgery are influenced by host and implant factors.

Methods

This study compares a single surgeon series of hip resurfacings (Birmingham Hip Resurfacing {BHR}) and large diameter metal on metal total hip replacements (LDMOMTHR). Primary outcome measures included survival rates, failure secondary to histologically identified Adverse Reaction to Metal Debris (ARMD), and patient reported outcome measures (Oxford Hip Score {OHS}) following revision.

Between 1999 and 2005, 458 BHR and 175 LDMOMTHR were performed. At latest review 43 BHR's (9.4%) and 28 LDMOMTHR's (14%) have been revised.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_34 | Pages 115 - 115
1 Dec 2013
Latham J Cook R Bolland B Yasen S
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Background

Large diameter chrome cobalt modular heads in hip replacement surgery have caused one of the biggest challenges to face orthopaedic surgeons, manufacturers and regulators in a generation. Increasing numbers of retrieved implants offer the opportunity to look in detail at the modes of failure of these devices.

Methods

We have examined the mechanical behaviour of the head taper/trunnion using a variety of techniques including:

mechanical testing in a custom-made jig

3D nano-precision form profilometry (RedLux)

optical 3D microscopy with focus variation technology

electro-chemical testing.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_34 | Pages 36 - 36
1 Dec 2013
Cook R Shearwood-Porter N Nicolae C Bolland B Latham J Wood R
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Introduction:

Cemented femoral components have been used in hip replacement surgery since its inception. For many patients this works well, but recent retrieval studies1–4 and more fundamental studies5, 6 have highlighted the issues of damage and material loss from the both matt and polished cemented stems.

Materials and methods:

This study will focus on a cohort of retrievals from the Southampton Orthopaedics Centre for Arthroplasty Retrieval Surgery (SOCARS). The cohort consisted of a number of hybrid modular total hip replacements with cemented femoral components, both from mixed and matched manufacturer stem and head combinations. Femoral stems were polished, collarless, tapered designs; head sizes ranged from 28–54 mm. For each femoral stem, samples of Palacos R + G cement (Heraeus Medical GmbH, Hanau, Germany) were retrieved from the proximal region of the cement mantle (Gruen zones 1 and 7), corresponding to both macroscopically damaged and undamaged surfaces of the stem. The areas of damage were determined using calibrated digital photography; damaged surfaces were then imaged in detail using an Alicona InfiniteFocus microscope (Alicona Imaging GmbH, Graz, Austria). The technique uses optical microscopy and focus variation technology to extract 3D morphology and depth information from the surface with a resolution of 10 nm. A series of measurements were made and two different analysis routes were used to provide volumetric material loss measurements from the stem surface. High-resolution microscopy and elemental analysis of the cement and stem surfaces was conducted via SEM and EDX to identify the mechanisms leading to material loss at the cement-stem interface.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_13 | Pages 12 - 12
1 Mar 2013
Bolland B Roques A Maul C Cook R Wood R Tuke M Latham J
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The poor outcome of large head metal on metal total hip replacements (LHMOMTHR) in the absence of abnormal articulating surface wear has focussed attention on the trunnion / taper interface. The RedLux ultra-precision 3D form profiler provides a novel indirect optical method to detect small changes in form and surface finish of the head taper as well as quantitative assessment of wear volume. This study aimed to assess and compare qualitatively tapers from small and large diameter MOMTHR's. Tapers from 3 retrieval groups were analysed. Group 1: 28mm CoCr heads from MOMTHRs (n=5); Group 2: Large diameter CoCr heads from LHMOMTHRs (n=5); Gp 3 (control): 28mm heads from metal on polyethylene (MOP) THRs; n=3). Clinical data on the retrievals was collated. RedLux profiling of tapers produced a taper angle and 3D surface maps. The taper angles were compared to those obtained using CMM measurements. There was no difference between groups in mean 12/14 taper angles or bearing surface volumetric and linear wear. Only LHMOMs showed transfer of pattern from stem trunnion to head taper, with clear demarcation of contact and damaged areas.3D surface mapping demonstrated wear patterns compatible with motion or deformations between taper and trunnion in the LHMOM group. These appearances were not seen in tapers from small diameter MOM and MOP THRs. Differences in appearance of the taper surface between poorly functioning LHMOMTHRs and well functioning MOP or MOM small diameter devices highlight an area of concern and potential contributor to the mode of early failure.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_15 | Pages 18 - 18
1 Mar 2013
Bolland B Maul C Cook R Roques A Tuke M Wood R Latham J
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The poor outcome of large head metal on metal total hip replacements (LHMOMTHR) in the absence of abnormal wear at the articulating surfaces has focussed attention on the trunnion / taper interface. The RedLux ultra-precision 3D form profiler provides a novel indirect optical method to detect small changes in the form and surface finish of the head taper as well as a quantitative assessment of wear volume. This study aimed to assess and compare qualitatively the tapers from well functioning small diameter, with poorly functioning LHMOMTHR's using the above technique.

Method

3 groups of retrieval tapers were analysed (Group 1: 28 mm CoCr heads from well functioning MOMTHRs (n=5); Group 2: Large diameter CoCr heads from LHMOMTHRs revised for failure secondary to adverse reaction to metal debris (n=5); Gp 3 (control): 28 mm heads from well functioning metal on Polyethylene (MOP) THRs; n=3). Clinical data on the retrievals was collated. The Redlux profiling of modular head tapers involves a non direct method whereby an imprint of the inside surface of a modular head is taken, and this is subsequently scanned by an optical non contact sensor using dedicated equipment [1]. The wear was also measured on the bearing surface [1]. RedLux profiling of the tapers produced a taper angle and 3D surface maps. The taper angles obtained with the Redlux method were compared to those obtained using CMM measurement on 3 parts. The Redlux profiling, including imprints, was also repeated 3 times to gauge potential errors.

Results

There was no difference in mean 12/14 taper angles between groups. There was no difference in volumetric and linear wear at the bearing surface between groups. Only the LHMOMs showed transfer of pattern from the stem to the internal head taper, with clear demarcation of the contact and damaged area between head taper and stem trunnion (see figure 1 – interpretation of head taper surface features demonstrated using Redlux optical imaging). 3D surface mapping demonstrated wear patterns compatible with motion or deformations between taper and trunnion in the LHMOM group. These appearances were not seen in tapers from small diameter MOM and MOP THRs (see Figure 2).


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_15 | Pages 19 - 19
1 Mar 2013
Bolland B Tilley S Tilley C Cook R Latham J
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Pseudotumour formation is being reported with increasing frequency in failing metal-on-metal hip resurfacings and replacements. This mode of failure complication has also been reported with metal-on-polyethylene bearing bearings when it is usually associated with evidence of surface corrosion and no apparent wear at the head–neck taper.

We present a case with evidence of taper wear and damage secondary to corrosion in an uncemented total hip replacement with a metal on polyethylene articulation (TMZF (Titanium, Molybdenum, Zirconium and Ferrous) Accolade® stem, Trident® HA coated acetabular shell, Low Friction Ion Treatment (LFIT™) Cobalt-Chrome anatomic head (40 mm), X3® polyethylene liner)

Case

A 69 year old woman had a THR in 2008. A year later she started to complain of lateral based hip pain. Clinical examination and initial imaging indicated trochanteric bursitis and heterotopic bone formation. The symptoms became worse over the next 3 years and the patient was listed for exploration and excision of heterotopic bone.

Surgical findings

Extensive pseudotumour was encountered deep to bursa and adherent to capsule. Abductors, external rotators and vastus lateralis were spared. There was minimal calcar osteolysis and marginal erosion in superior acetabulum. There was no obvious wear on the articulating surfaces of the femoral head and polyethylene inlay of the socket nor was there any evidence of neck-to-rim impingement or edge loading. There was visible blackening of both the taper and trunnion after femoral head removal.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_1 | Pages 139 - 139
1 Jan 2013
Bolland B Maul C Cook R Roques A Wood R Latham J
Full Access

The poor outcome of large head metal on metal total hip replacements (LHMOMTHR) in the absence of abnormal wear at the articulating surfaces has focussed attention on the trunnion/taper interface. The RedLux ultra-precision 3D form profiler provides a novel indirect optical method to detect small changes in form and surface finish of the head taper as well as a quantitative assessment of wear volume. This study aimed to assess and compare qualitatively the tapers from small diameter with LHMOMTHR's. 3 groups of retrieval tapers were analysed (Group 1: 28mm CoCr heads from MOMTHRs (n=5); Group 2: Large diameter CoCr heads from LHMOMTHRs (n=5); Group 3: 28mm heads from metal on polyethylene (MOP) THRs; n=3). Clinical data on the retrievals was collated. Both bearing surfaces and head tapers were measured for wear using the Redlux profiling non contact measurement system. Measurements included taper angle and 3D surface maps. Taper angles obtained with the Redlux method were compared to those obtained using CMM measurement on 3 parts. The Redlux profiling, including imprints, was also repeated 3 times to gauge potential errors. There was no difference in mean 12/14 taper angles between groups. There was no difference in volumetric and linear wear at the bearing surface between groups. Only the LHMOMs showed transfer of pattern from the stem to the internal head taper, with clear demarcation of the contact and damaged area between head taper and stem trunnion. 3D surface mapping demonstrated wear patterns compatible with motion or deformations between taper and trunnion in the LHMOM group alone. Discussion: Differences in appearance of the taper surface between LHMOMTHRs and MOP or MOM small diameter devices highlight an area of concern and potential contributor to the mode of early failure. Further work is required to fully qualify the Redlux method capabilities.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVI | Pages 98 - 98
1 Aug 2012
Cook R Curwen C Tasker T Zioupos P
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Osteoporosis (OP) results in a reduction in the mechanical competence of the bone tissue of the sufferers. In skeletal sites such as the proximal femur and the vertebrae, OP manifests itself in low trauma fragility fractures which are debilitating for the patient. The relationships between the compressive strength of cancellous tissue and its apparent density are well established in studies of the past. Recently the authors have presented a method able to assess the fracture toughness properties of cancellous bone (1), a challenging cellular material which can exhibit large elasto-plastic deformations. The in-vitro measurement of fracture toughness alongside the customary compressive strength can provide a comprehensive assessment of the mechanical capacity of cancellous bone, which will reflect closer its ability to resist crack initiation. The aims of the present study were: (1) to examine whether the observed fracture toughness deterioration can also be detected by non-invasive quantitative ultrasound (QUS); and (2) to provide rational evidence for the well proven ability of QUS to predict directly ‘risk of fracture’. 20 femoral heads were obtained from donors undergoing emergency surgery for a fractured neck of femur. QUS investigations of the calcaneus, proximal phalanx and distal radius were undertaken within 72 hours of surgery. 128 fracture toughness samples and 20 compression cores were manufactured and tested. Two clinical QUS systems were used to obtain in-vivo scan data and then directly compared those to the density, porosity and the fracture mechanics of tissue extracted from the same individuals. The results demonstrated not only that there was a significant link between in-vivo determined QUS values for the calcaneus and finger to the density of the density of the femoral head; but that there was also a significant link between the QUS results from the calcaneus and the fracture toughness of the cancellous bone from the femoral head. These results point towards a systemic effect of osteoporosis which affects similarly different parts of the skeleton and supports the use of clinical QUS systems as a diagnostic tool for the prediction of fracture risk.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXIII | Pages 12 - 12
1 Jul 2012
Waterson H Brenkel I Cook R
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The Oxford medial unicompartmental knee replacement has been shown to provide good long-tern results in numerous studies with survivorship at 10 years ranging from 82% to 100%. This prospective study describes the survival of 265 Oxford unicompartmental knee replacements implanted in one centre from 1995-2009. 8 were lost to follow up. 40 of the 265 knees were revised. For operation performed from1995-1999 the risk of revision at 5 years was 10%, operations from 2000-2004 the risk of revision was 15% and from 2005-2009 the risk of revision at 5 years was 36%.

This study demonstrates that since 2005 there has been a significant increase in early failure of the Oxford unicompartmental knee at this institution and discusses the possible reasons for this.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_III | Pages 6 - 6
1 Feb 2012
Amin A Clayton R Patton J Gaston M Cook R Brenkel I
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Aim

To compare the results of total knee replacement in a consecutive series of morbidly obese patients (body mass index (BMI) > 40 kg/m2) with a matched group of non-obese (BMI< 30 kg/m2) patients.

Methods

41 consecutive total knee replacements performed in morbidly obese patients were matched pre-operatively with 41 total knee replacements performed in non-obese patients for age, sex, diagnosis, type of prosthesis, laterality, knee score and function score components of the Knee Society Score (KSS). All patients were prospectively followed up and the post-operative KSS, radiographs, complications (superficial wound infection, deep joint infection, deep venous thrombosis, peri-operative mortality) and five-year survivorship compared for the two groups. No patients were lost to follow-up (mean follow-up in morbidly obese: 38.5 (range 6-66) months; non-obese: 44 (range 6-67) months).


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_I | Pages 100 - 100
1 Mar 2006
Amin A Patton J Cook R Gaston M Brenkel I
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Introduction To assess five-year survivorship and clinical outcome following unicompartmental knee replacement (UKR) and total knee replacement (TKR) in pre-operatively matched patient groups.

Methods From a prospective database of over 600 patients undergoing knee replacement for osteoarthritis, 70 primary Oxford UKRs (62 patients) were matched pre-operatively with 70 primary PFC TKRs (68 patients) for age, sex, body mass index, knee range of movement and Knee Society Score (KSS). The two groups were assessed at six, eighteen, thirty-six and sixty months following knee replacement and compared for survivorship of the prosthesis (with failure defined as revision for any reason or ‘worst-case’ assuming all patients lost to follow up are revised), post-operative ROM achieved and clinical outcome based on the KSS (reported as separate knee and function score).

Results Three (5 percent) patients in the UKR group and two (3 percent) in the TKR group were unavailable for follow-up at five years. Five-year survivorship based on revision for any reason was 90 percent (95 percent Confidence Interval (CI): 82 to 98) for UKR and 100 percent (95 percent CI: 100 to 100) for TKR (log rank test: p=0.009). The ‘worst-case’ five-year survivorship (assuming all patients lost to follow up are revised) was 85 percent (95 percent CI: 76 to 94) for UKR and 97 percent (95 percent CI: 93 to 100) for TKR (log rank test: p=0.02). The mean post-operative ROM achieved was 105.3 degrees following UKR and 98.3 degrees following TKR (difference 7.0 (95 percent CI 3.3 to 10.6), p< 0.001). There was no difference in the KSS between the two groups for the knee score (difference 0.1 (95 percent CI: −4.3 to 4.5), p=0.9) and function score (difference 2.6 (95 percent CI: −1.7 to 6.9), p=0.2).

Conclusion In comparable patients with osteoarthritis of the knee, survivorship remains superior for TKR at five years. The ROM achieved is greater for UKR but there is no difference in the overall clinical outcome following UKR or TKR. We believe that UKR should only be performed in carefully selected cases because mid-term clinical outcome is similar following UKR or TKR and the complication rate may be higher for UKR.


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_I | Pages 89 - 89
1 Mar 2006
Amin A Patton J Cook R Brenkel I
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Aim To compare clinical outcome and complication rates in obese and non-obese patients five years following primary Total Knee Replacement (TKR) for osteoarthritis.

Methods 328 primary TKRs (283 patients) performed between 1995–1999 at a single institution, were followed up prospectively at intervals of 6, 18, 36 and 60 months following surgery and the clinical outcome based on the Knee Society Clinical rating system (subdivided into a Knee Score (KS) and Function score (FS)) recorded at each follow-up interval. The following complications were also recorded: peri-operative mortality, superficial wound infection, deep wound infection, deep vein thrombosis, and revision rate. Three separate comparisons were undertaken by subdividing the study sample into two sub-groups: (1) Group A comprised two subgroups based on body mass index (BMI) – Non-obese (BMI 15–30, 181 TKRs) or Obese (BMI> 30, 147 TKRs). (2) Group B comprised only female patients divided into two sub-groups based on BMI – ‘Non-obese females’ (BMI 15–30, 84 TKRs) or Obese females (BMI> 30, 87 TKRs). (3) Group C comprised two sub-groups based on body weight alone – weight < 100kg (300 TKRs) or weight > 100kg (28 TKRs). A repeated measures split-plot analysis of variance (SPANOVA) was used to evaluate the difference in the clinical outcome at five years between the sub-groups in Group A, B and C. The complication rates were also compared.

Results There was no significant difference in the KS at five years between sub-groups in Group A (p=0.2), B (p=0.2) or C (p=0.3). There was a statistically significant difference in the FS between the subgroups in Group A (p=0.01) and B (p=0.02) but the effect size (relative magnitude of the difference between means) was small (partial eta squared = 0.02 and 0.03, for Group A and B respectively). There was no significant difference in the FS between sub-groups in Group C (p=0.5). There was no significant difference in the complication rate between the sub-groups in Group A, B or C (p> 0.2 for all complications).

Conclusion Obesity does not influence clinical outcome, peri-operative mortality and complication rates five years following TKR. Further studies are required to determine the long-term success of TKR in obese patients.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 301 - 302
1 Sep 2005
Walmsley P Cook R Brenkel I
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Introduction and Aims: Venous Thromboembolism is a common complication following a hip replacement. Recently the pulmonary embolism prevention study was published. It reported that aspirin decreased the fatal pulmonary embolism rate in patients admitted with a fracture neck of femur. In addition, new products (synthetic factor X inhibitor-Fondaparinux, and a direct thrombin inhibiter-Desirudin) have been reported to be more effective than low molecular weight heparin in preventing asymptomatic deep vein thrombosis. We felt it was important to repeat a survey, done in 1997, on the use of thromboembolism prophylaxis among British Orthopaedic Surgeons.

Method: A single page questionnaire was sent out to all 1308 consultants – orthopaedic surgeons who were members of the British Orthopaedic Association. Those who did not respond were sent a reminder letter.

Results: We achieved a 72% response rate. All surgeons use some form of prophylaxis. Eighty-five percent of surgeons use pharmacological prophylaxis. Low molecular weight heparin is used by 55% of surgeons. Twenty percent of surgeons use aspirin as their only form of pharmacological prophylaxis. Less than 1% (five consultants) use early mobilisation alone and nearly 2% (13 consultants) use graded stockings and early mobilisation as their only form of prophylaxis. Seventy-four percent of surgeons have a unit policy. Thirty percent have changed their regime in the last three years.

Conclusion: The majority of British orthopaedic surgeons still use pharmacological thromboprophylaxis. There has been a significant increase in the use of Aspirin, from 5% to 30%. Aspirin is often combined with a mechanical prophylaxis. This has led to an increase in the use of intermittent calf compression (3% to 22%), and foot pumps (12% to 19%). Low molecular weight heparin use has fallen by 10%.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 277 - 277
1 Sep 2005
Brenkel I Cook R
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Venous thrombo-embolism is a common complication following hip replacement. The recently-published pulmonary embolism prevention study reported that aspirin decreased the fatal pulmonary embolism rate in patients with femoral neck fractures. In addition, new products (synthetic factor X-inhibitor Fondaparinux and direct thrombin-inhibiter Desirudin) have been reported to be more effective than low-molecular-weight heparin in preventing asymptomatic DVT. We thought it important to update the 1997 survey on thrombo-embolism prophylaxis by British Orthopaedic Surgeons.

A single page questionnaire was sent to 1308 members of the British Orthopaedic Association who are consultant orthopaedic surgeons. Those who did not respond received a reminder. We had a 72% response rate.

All surgeons use some form of prophylaxis, with 85% using pharmacological agents. Low-molecular-weight heparin is used by 55% of surgeons, while 20% use only aspirin. Fewer than 1% (five consultants) use early mobilisation and nearly 2% (13 consultants) use graded stockings and early mobilisation as their only prophylactic measures. Unit policies govern 74% of surgeons. In the last 3 years, 30% have changed their regime.

Most British orthopaedic surgeons still use pharmacological thromboprophylaxis. The use of aspirin has increased from 5% to 30%. Aspirin is often combined with a mechanical prophylactic. The use of intermittent calf compression has increased from 3% to 22% and of foot pumps from 12% to 19%. The use of low-molecular-weight heparin has fallen by 10%.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 343 - 343
1 Sep 2005
Patton J Amin A Gaston M Cook R Brenkel I
Full Access

Introduction and Aims: Several non-comparative studies for uni-compartmental knee replacement (UKR) and total knee replacement (TKR) have been published, but few provide a direct comparison in well-matched patients. The aim of this study was to assess five-year survivorship and the quality of outcome following UKR and TKR in pre-operatively matched patient groups.

Method: From a prospective database of over 600 patients undergoing knee replacement for osteoarthritis, 70 primary medial Oxford UKRs (62 patients) were matched pre-operatively with 70 primary Kinematic TKRs (68 patients) for age, sex, body mass index, active range of movement (ROM) and Knee Society Score (KSS). The two groups were assessed at six, 18, 36 and 60 months following knee replacement and compared for survivorship of the prosthesis (with failure defined as revision for any reason or ‘worst-case’ assuming all patients lost to follow-up are revised), quality of outcome based on the KSS (reported as separate knee and function score) and the ROM achieved.

Results: Three (4%) patients in the UKR group and two (3%) in the TKR group were unavailable for follow-up at five years. Five-year survivorship (Kaplan-Meier methodology) was significantly different for the two groups using revision for any reason as an endpoint – 90% for UKR, 100% for TKR (log-rank test, p=0.01). Assuming all patients lost to follow-up were revised, the ‘worst-case’ five-year survivorship was also significantly different for the two groups – 85% for UKR, 97% for TKR (log-rank test, p=0.02). Analysis of the KSS at six, 18, 36 and 60 months showed no significant difference between the two groups for the knee score (p=0.48) and the function score (p=0.1). The ROM achieved at five years was greater for the UKR group and the difference was statistically significant (UKR: Least square mean 105 degrees, standard error 1.2; TKR: Least square mean 98 degrees, standard error 1.2, p< 0.001).

Conclusion: In comparable patients with osteoarthritis of the knee, survivorship remains superior for TKR at five years. The ROM achieved is greater for UKR, but there is no difference in the overall quality of outcome following UKR or TKR. We believe that UKR should only be performed in carefully selected cases because mid-term functional outcome is similar following UKR or TKR and the complication rate may be higher for UKR.


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_I | Pages 73 - 73
1 Jan 2004
Brenkel IJ Cook R
Full Access

Venous Thromboembolism is a common complication following a hip replacement. Recently the pulmonary embolism prevention study was published. It reported that aspirin decreased the fatal pulmonary embolism rate in patients admitted with a fracture neck of femur. In addition new products (synthetic factor X inhibitor -Fondaparinux, and a direct thrombin inhibiter-Desirudin) have been reported to be more effective than low molecular weight heparin in preventing asymptomatic deep vein thrombosis. We felt it was important to repeat a survey, done in 1997, on the use thromboembolism prophylaxis among British Orthopaedic Surgeons.

A single page questionnaire was sent out to all 1308 consultants Orthopaedic surgeons who were members of the British Orthopaedic Association. Those who did not respond were sent a reminder letter.

We achieved a 72% response rate. All surgeons use some form of prophylaxis. Eighty five percent of surgeons use pharmacological prophylaxis. Low molecular weight heparin is used by 55% of surgeons. Twenty percent of surgeons use aspirin as their only form of pharmacological prophylaxis. Less than 1% (5 consultants) use early mobilisation alone and nearly 2% (13 consultants) use graded stockings and early mobilisation as their only form of prophylaxis. Seventy four percent of surgeons have a unit policy. Thirty percent have changed their regime in the last 3 years.

The majority of British Orthopaedic surgeons still use pharmacological thromboprophylaxis. There has been a significant increase in the use of Aspirin from 5% to 30%. Aspirin is often combined with a mechanical prophylaxis. This has led to an increase in the use of intermittent calf compression (3% to 22%), and foot pumps (12% to 19%). Low molecular weight heparin use has fallen by 10%.

The majority of British Orthopaedic surgeons still use pharmacological thromboprophylaxis. There has been a significant increase in the use of Aspirin from 5% to 30%. Aspirin is often combined with a mechanical prophylaxis. This has led to an increase in the use of intermittent calf compression (3% to 22%), and foot pumps (12% to 19%). Low molecular weight heparin use has fallen by 10%.