Periprosthetic joint infection is a serious complication of primary total hip replacement (THR) with significant associated morbidity. In acute infection, Debridement, Antibiotics and Implant Retention (DAIR) may be considered. Current national guidelines recommend a DAIR should be performed by “an experienced arthroplasty surgeon┕ but do not specify the need for this to be a revision arthroplasty surgeon. We investigated outcomes in our NHS Trust of DAIR procedures performed by revision and non-revision arthroplasty surgeons.

Infection registry data and patient records were analysed for all DAIR procedures of infected primary THRs between 2017 and 2021. Data collected included details of the primary surgery, the presentation with infection, the DAIR procedure and any subsequent complications including return to theatre at any time point. Routinely collected pre- and post-operative patient reported outcome measures (PROMs) were reviewed.

54 periprosthetic joint infections of primary THRs received a DAIR procedure. 41 DAIRs were performed by a revision surgeon and 13 by non-revision surgeons. There was no significant difference in time from primary THR to presentation with infection, time from presentation to DAIR or pre-operative C-reactive protein between the two groups.

In 21 (38.9%) patients the DAIR procedure was classed as a treatment failure; 17 patients (31.5%) returned to theatre for further revision surgery, one (2.4%) died related to infection and three (5.6%) had persistent infection but did not receive further surgery. Treatment failure was significantly higher in the non-revision surgeon group (9/13 (69.2%)) than in the revision surgeon group (12/41 (29.3%)) (p = 0.02). Overall, improvement in PROMs after DAIR was seen at both six and 12 months.

The overall success rate of DAIR was 61.1% and there was a sustained improvement in PROMs after surgery. However, there was a significant difference in failure rates between revision surgeons and non-revision surgeons.

Aims

The rate of day-case total knee arthroplasty (TKA) in the UK is currently approximately 0.5%. Reducing length of stay allows orthopaedic providers to improve efficiency, increase operative throughput, and tackle the rising demand for joint arthroplasty surgery and the COVID-19-related backlog. Here, we report safe delivery of day-case TKA in an NHS trust via inpatient wards with no additional resources.

Abstract

Abstract

In metal-on-metal (MoM) hip replacements or resurfacings, mechanical induced corrosion can lead to a local inflammatory response, pseudo tumours and elevated serum metal ions, requiring revision surgery.

The size and diametral clearance of Anatomic (ADM) and Modular (MDM) Dual Mobility bearings matches that of certain MOM components. Presenting the opportunity for revision with exchange of the metal head for ADM/MDM bearings without removal of the acetabular component if it is well-fixed and appropriately positioned.

Between 2012 and 2020, across two centres, 94 patients underwent revision of a MoM hip replacement or resurfacing. The mean age was 65.5 (33–87) years. In 53 patients (56.4%), the acetabular component was retained, and dual mobility bearings were used (DM); in 41 (43.6%) the acetabulum was revised (AR). DM was only considered where the acetabular component was satisfactorily positioned and well-integrated into bone, with no surface damage. Patients underwent clinical and radiographic follow-up to at least one-year (mean 42.4 (12–96) months).

One (1.1%) patient died before one-year, for reasons unrelated to the surgery. In the DM group, two (3.8%) patients underwent further surgery; one (1.9%) for dislocation and one (1.9%) for infection. In the AR group, four (12.2%) underwent further procedures; two (4.9%) for loosening of the acetabular component and two (4.9%) following dislocations. There were no other dislocations in either group. In the DM group, operative time (68.4 v 101.5 mins, p<0.001), postoperative drop in haemoglobin (16.6 v 27.8 g/L, p<0.001), and length of stay (1.8 v 2.4 days, p<0.001) were significantly lower. There was a significant reduction in serum metal ions postoperatively in both groups (p<0.001 both Cobalt and Chromium) although there was no difference between groups for this reduction (p=0.674 Cobalt; p=0.186 Chromium).

In selected patients with MoM hip arthroplasty, where the acetabular component is well-fixed, in a satisfactory position and there is no surface damage, the metal head can be exchanged for ADM/MDM bearings with retention of the acetabular prosthesis. Presenting significant benefits through a less invasive procedure, and a low risk of complications, including dislocation.

Femoral cement-in-cement revision is a well described technique to reduce morbidity and complications in hip revision surgery. Traditional techniques for septic revision necessitate removal of all bone cement from the femur. In our two institutions, we have been using a cement-in-cement technique, leaving the distal femoral cement in selected cases for septic hip revision surgery.

Between February 2010 and September 2019, 89 patients with prosthetic hip infection underwent first or single stage procedures leaving the distal femoral cement in situ and performing a cement-in-cement revision. The mean patient age was 72.0 years (24–92). The median time from the last arthroplasty procedure was 29.0 months (1–294).

81 patients underwent revision using a cemented Exeter stem, 7 patients received an articulating spacer, and one patient underwent excision arthroplasty with the distal cement left in situ. Patients received clinical and radiographic follow-up with a mean of 42.8 months (range 11.0–120.1 months). Oxford hip scores were collected from each institution's existing databases.

9 patients (10.1%) died within one year of surgery. No deaths were directly related to joint infection or the surgery. One patient was lost to follow up before one year.

Of the remainder, 7 patients (8.9%) required further procedures for infection and were therefore considered to be treatment failures. 6 patients (7.6%) underwent planned second stage procedures with no recurrence of infection. 7 patients (8.9%) had further surgery for non-infective reasons. The Kaplan-Meier estimate of infection free survival at one year was 93.7% (95% CI 88.4 to 99.0%).

No patients underwent revision for stem loosening. Oxford hip scores were available at over one year postoperatively for 51 patients with a mean score of 30.6, and a mean gain of 11.9.

In our combined cohort of patients, cement-in-cement revision had an infection eradication rate of 91.1%. Patient selection is crucial, and the procedure can only be performed when there is a well-fixed cement mantle. However, when strict criteria are followed, this technique offers potential significant benefits to surgeons performing this challenging surgery, and more importantly the patients undergoing them.

Aims

Antibiotic-loaded bone cements (ALBCs) may offer early protection against the formation of bacterial biofilm after joint arthroplasty. Use in hip arthroplasty is widely accepted, but there is a lack of evidence in total knee arthroplasty (TKA). The objective of this study was to evaluate the use of ALBC in a large population of TKA patients.

Aims

Surgical site infection (SSI) is a common complication of surgery with an incidence of about 1% in the United Kingdom. Sutures can lead to the development of a SSI, as micro-organisms can colonize the suture as it is implanted. Triclosan-coated sutures, being antimicrobical, were developed to reduce the rate of SSI. Our aim was to assess whether triclosan-coated sutures cause a reduction in SSIs following arthroplasty of the hip and knee.

INTRODUCTION

Dislocation is a major complication post total hip replacement (THR) and a common cause for revision. Jameson et al (2012) studied 35,000 cemented Exeter (Stryker) THRs demonstrating the risk of revision was significantly influenced by the acetabular component design. This led 3 surgeons in a single hospital group to make a mass move from using the hooded Exeter Low Profile (LP) cup to the better performing Contemporary Flanged (CF) component. The purpose of this study was to show whether this change was associated with a fall in dislocation rates.

INTRODUCTION

Deep infection is a potentially catastrophic complication of joint replacement surgery. Early intervention in suspected prosthetic joint infection in the form of aggressive Debridement and targeted Antibiotics can lead to successful Implant Retention (DAIR). In our centre, we adopt an aggressive approach to suspected prosthetic joint infection, working in a multi-disciplinary team with microbiologists and an infection surveillance team to identify and treat suspected infected cases at the earliest opportunity.

Introduction

There is much current debate concerning wear and corrosion at the taper junctions of large head total hip replacements, particularly metal-on-metal hips. Is such damage a modern concern or has it always occurred in total hip replacement but not previously noted. To investigate this five explanted V40 Exeter femoral stems (Stryker Howmedica) were obtained following revision surgery at a single centre. In all cases, the 24–26 mm femoral heads were still attached.

Recent NICE guidance recommends use of a well proven cemented femoral stem for hip hemiarthroplasty in management of fractured neck of femur. The Exeter Trauma Stem (ETS) has been designed based on the well proven Exeter hip stem. It has a double taper polished stem design, proclaimed to share geometry and surface finish with the Exeter hip. This study investigated the surface finish of the two stems in order to investigate the hypothesis that they were different. Two ETS and two Exeter stems were examined using a profilometer with a sensitivity of one nanometer. Macroscopic visual inspection showed that the two Exeter stems had significantly smoother surface finish than the ETS stems. The roughness average (RA) values on the ETS stems were approximately an order of magnitude higher than those of the Exeter stems, mean of 0.235μm compared with 0.025μm (p<0.0001). This difference in surface finish has implications for the biomechanical functioning of the stem. Previous change of the Exeter stem to a matt surface-finish in 1976 resulted in a significant increase in stem failure rates and an understanding of the importance of the polished surface-finish in order to function within a taper-slip philosophy. By changing the surface finish in the ETS stem, longevity of the implant may similarly be affected. Clinical results have yet to be published demonstrating this. We recommend the manufacturer reconsiders the surface finish of the ETS stem to ensure it functions as well as the Exeter primary stem with which it shares a design philosophy.

Background

Dislocation is a major complication following total hip arthroplasty (THA). Aetiology is multi-factorial, but increasing femoral head size may result in lower dislocation rates. The latest England and Wales National Joint Registry (NJR) annual report has highlighted a statistically significant increase in the use of femoral heads of size 36mm+ from 5% in 2005 to 26% in 2009, together with an increase in the use of the posterior approach. The aim of this study was to determine whether national dislocation rates have fallen over the same period.

Introduction

Rivaroxaban has been recommended for routine use as a thromboprophylactic agent in patients undergoing lower limb arthroplasty. Trials supporting its use have not fully evaluated the risks of wound complications related to rivaroxaban.

Background

Hemiarthroplasty of the hip involves the replacement of the femoral side of the joint with a metal prosthesis, resulting in metal-on-cartilage articulation. The two most common types of hemiarthroplasty used are the Austin Moore and the Thomson, both of which are available in either Titanium (Ti) or cobalt chromium (CoCr). Hemiarthroplasty may be more cost effective in elderly patients who have lower life expectancy and are less active.

Introduction

To report the short to medium term results of acetabular reconstruction using reinforcement/reconstruction ring, morcellised femoral head allograft and cemented metal on metal cup.

Introduction

The aim of this study is to report the results of Revision hip arthroplasty using large diameter, metal on metal bearing implants- minimum 2 year follow up.

Introduction: Following successful introduction in 2007, all training programs except two across the UK participated in the examination in 2008. The examination was run along the principles of curriculum based, online delivery with immediate results and providing supportive information for the questions. It remains free of charge as long as the trainee had contributed questions. The project is supported by an educational grant from Depuy, a Johnson and Johnson Company.

Material and Methods: In 2008 trainees from various regions were appointed to a UKITE review board, which creating good quality questions with supportive information. We took on board the feedback from 2007 examination and improved the quality of questions. Some questions from the 2008 examination were reported as ambiguous. The review board met and ambiguous questions were deleted from the exam and scores were recalculated.

Results: 648 trainees took UKITE 2008. The average scores increased up to 5th year SpR and dropped in year 6. Central organisation (86%) and local organisation (90%) were acceptable. 95% felt the examination pages were easy to use. There was difficulty in accessing the examination from NHS networks in some centers on the final day. 95% found there was educational benefit and 99% would like to sit again in 2009.

In the feedback from UKITE 2008, 85% of trainees felt it was better quality than 2007. The trainees wanted more questions on clinical situations. Those approaching the FRCS examination are interested in using the database towards preparation for the real examination. Some enthusiastic trainees would like the facility to submit questions early. We aim to improve on these in 2009.

In 2009 we also aim to open the examination for other surgical specialties and international trainees through elogbook.org.

Conclusion: UKITE has made progress in 2008. We aim to improve it further in 2009.

The first United Kingdom In-training Examination (UKITE) was held in 19 training programmes during December 2007. The aims of the project are to offer a national, online examination (providing immediate results to trainees) and to allow practice for the ‘real’ FRCS T& O examination with similarly formatted questions based on the UK T& O curriculum. All Speciality training years (StR2, StR3 and above, and all SpRs) and all deaneries will participate in the future. A total of 450 trainees sat this first examination. This is an online exam (accessed through the eLogbook/OCAP website) which is voluntary and has no bearing on RITA outcomes. To take part in the exam trainees were asked to provide 3 questions for a bank which can be used in subsequent years for both UKITE and the FRCS T& O examination.

The exam was 3 hours and questions were of multi-choice (MCQ) and extended matching question (EMQ) style covering all aspects of orthopaedics. Correct answers and explanations were available to the trainee after their answer had been submitted. Final scores ranged from 35% to 92%. Mean scores increased from 48% (StR2) to 73% in SpR year 5 (StR7 equivalent). This was followed by a drop off in performance in the final year of training. Three candidates had equal top scores at 92%. 97% stated they would sit the UKITE again and 93% felt there was educational benefit. The length and level of difficulty of the exam was felt to be satisfactory. Improvements were suggested for question quality. The UKITE is a powerful tool for self-assessment of trainees. This analysis establishes a baseline for future years.

Introduction: Following successful introduction in 2007, all training programs except two participated in 2008. The examination was run along the principles of curriculum based, online delivery with immediate results and providing supportive information for the questions. The examination remains free of charge for the trainees and is supported by an educational grant from Depuy.

Material and methods: In 2008 a UKITE review board was appointed to create good quality questions with supportive information. We took on board the feedback from 2007 examination. Some questions from the 2008 examination were reported as ambiguous. The review board met and ambiguous questions were deleted from the examination and the scores recalculated.

Results: 648 trainees took UKITE 2008. Central organisation (86%) and local organisation (90%) were acceptable. 95% felt the examination pages were easy to use. There was difficulty in accessing the examination from NHS networks in some centers on the final day. 95% found there was educational benefit and 99% would like to sit again in 2009.

In the feedback from UKITE 2008, 85% of trainees felt it was better quality than 2007. The trainees approaching the FRCS examination are interested in using the database towards preparation.

In 2009 we aim to open the examination for SAS doctors, other surgical specialties and international trainees through elogbook.org.

Conclusion: UKITE has made progress in 2008. We aim to improve it further and open it to SAS doctors, other specialties and international trainees in 2009.

Background: There are no large comparative metal ion studies of commercially available hip resurfacing devices which have taken into account the effects of femoral size and cup inclination and anteversion.

Patients and methods: Metal ion analysis is carried out routinely at our independent centre. We present the metal ion results of 95 unilateral ASR patients and 70 unilateral BHR patients. For all patients, acetabular cup orientation was assessed using EBRA software. Patients with other metallic implants and those within 12 months of surgery were excluded.

Results: Whole blood/serum chromium (Cr) and cobalt (Co) concentrations were inversely related to femoral component size in both the ASR and BHR group (p< 0.05). Cr and Co levels were only seen to increase in the BHR group when the cup was implanted with an inclination greater than 55°. A significant relationship was identifed between the anteversion of the BHR cup and Cr and Co (p< 0.05 for Co, Spearman Rank correlation), with an increase in ions observed at anteversion angles > 17°. Cr and Co were more strongly influenced by cup position in the case of the ASR, with an increase in metal ions observed at inclinations greater than 45° and anteversion angles of < 10° and > 20°.

Discussion: The increased tolerance of the BHR cup to inclinations between 45–55° is likely due to the larger BHR cup providing greater protection against edge loading. When the cohort was divided by gender, the median Cr concentrations of the male ASR patients were significantly lower than those of the BHR males (p< 0.001). This suggests that in larger components positioned at more satisfactory angles of inclination and anteversion, the lower clearance of the ASR proves more significant than the extra coverage provided by the BHR cup. The BHR appears to be more sensitive to changes in anteversion than inclination.

There have been no large comparative studies of the blood levels of metal ions after implantation of commercially available hip resurfacing devices which have taken into account the effects of femoral size and inclination and anteversion of the acetabular component. We present the results in 90 patients with unilateral articular surface replacement (ASR) hip resurfacings (mean time to blood sampling 26 months) and 70 patients with unilateral Birmingham Hip Resurfacing (BHR) implants (mean time 47 months).

The whole blood and serum chromium (Cr) and cobalt (Co) concentrations were inversely related to the size of the femoral component in both groups (p < 0.05). Cr and Co were more strongly influenced by the position of the acetabular component in the case of the ASR, with an increase in metal ions observed at inclinations > 45° and anteversion angles of < 10° and > 20°. These levels were only increased in the BHR group when the acetabular component was implanted with an inclination > 55°.

A significant relationship was identified between the anteversion of the BHR acetabular component and the levels of Cr and Co (p < 0.05 for Co), with an increase observed at anteversion angles < 10° and > 20°. The median whole blood and serum Cr concentrations of the male ASR patients were significantly lower than those of the BHR men (p < 0.001). This indicates that reduced diametral clearance may equate to a reduction in metal ion concentrations in larger joints with satisfactory orientation of the acetabular component.

Purpose: Recent animal evidence has suggested that Bupivicaine may be harmful to articular cartilage. The purpose of this study was establish whether, following arthroscopy of the knee, infiltration of Bupivicaine around the portals is as effective as intra-articular infiltration for post-operative analgesia.

Method: Consecutive patients attending for knee arthroscopy were consented and randomised to one of two groups. Following arthroscopy, Group I received 20mls 0.5% Bupivicaine infiltrated into the joint; Group II received 20mls 0.5% Bupivicaine infiltrated around the portals. A Visual Analogue Score (VAS) was collected at one hour post-operatively and rescue analgesia recorded. A power calculation was performed. Ethical approval was granted.

Results: There were 68 patients in Group I (intra-articular) and 69 patients in Group II (portal). There was no significant difference in the age or sex distribution of patients in either group. The mean VAS score was 3.04 in Group I and 3.24 in Group II. There was no significant difference between the two groups (p=0.619). There was also no significant difference in the need for rescue analgesia (p=0.930). The study has demonstrated equivalence between the two groups, within one VAS point (Power = 80%).

Conclusion: We would recommend that following knee arthroscopy, Bupivicaine should be infiltrated around the portals, avoiding intra-articular infiltration.

The administration of intra-articular local anaesthetic is common following arthroscopy of the knee. However, recent evidence has suggested that bupivacaine may be harmful to articular cartilage. This study aimed to establish whether infiltration of bupivacaine around the portals is as effective as intra-articular injection.

We randomised 137 patients to receive either 20 ml 0.5% bupivacaine introduced into the joint (group 1) or 20 ml 0.5% bupivacaine infiltrated only around the portals (group 2) following arthroscopy. A visual analogue scale was administered one hour post-operatively to assess pain relief. Both patients and observers were blinded to the treatment group. A power calculation was performed.

The mean visual analogue score was 3.24 (sd 2.20) in group I and 3.04 (sd 2.31) in group 2. This difference was not statistically significant (p = 0.62).

Infiltration of bupivacaine around the portals had an equivalent effect on pain scores at one hour, and we would therefore recommend this technique to avoid the possible chondrotoxic effect of intra-articular bupivacaine.

Digital radiography is becoming widespread. Accurate pre-operative templating of digital images of the hip traditionally involves positioning a calibration object at its centre. This can be difficult and cause embarrassment. We have devised a method whereby a planar disc placed on the radiographic cassette accounts for the expected magnification. Initial examination of 50 pelvic CT scans showed a mean hip centre distance of 117 mm (79 to 142) above the gluteal skin. Further calculations predicted that a disc of 37.17 mm diameter, placed on the cassette, would appear identical to a 30 mm sphere placed at the level of the centre of the hip as requested by our templating software. We assessed accuracy and reproducibility by ‘reverse calibration’ of 20 radiographs taken three months after hip replacement using simultaneous sphere and disc methods, and a further 20 with a precision disc of accurate size. Even when variations in patient size were ignored, the disc proved more accurate and reliable than the sphere.

The technique is reliable, robust, cost effective and acceptable to patients and radiographers. It can easily be used in any radiography department after a few simple calculations and manufacture of appropriately-sized discs.

Purpose: to quantify the cost of hospitalisation and theatre time in the treatment of infected primary total knee replacements.

Materials and Methods: hospital approval was obtained for the study. Inclusion criteria were defined as: patients requiring surgery for deep or superficial infection of a primary total knee replacement (TKR) with subsequent positive bacteriological cultures. Clinical coding provided a list of patients with the ICD 10 code T845 (infection or inflammatory reaction due to an internal joint replacement) over a 2 year period and notes of patients were obtained to confirm the inclusion criteria were met. The theatre procedures performed and numbers of days in hospital for all admissions related to joint infection were recorded. The cost of a day in hospital and the cost of each procedure by time in minutes were obtained from the hospital finance department hence the overall cost of hospitalisation and theatre per patient estimated.

Results: 15 patients were identified as having undergone surgery for an infected primary TKR. Prolonged hospital stay, predominantly for administration of antibiotics claimed the largest proportion of expenditure in our patient group. An average of 64 excess days per patient were spent in hospital (range 13 to 218). The cost of an overnight hospital stay is £180, therefore the cost per patient was £11544. Seven day procedures at a cost of £473 each were also carried out. Each patient underwent an average of 4.7 theatre procedures (range 1 to 12). The most common surgical procedures were joint washout / debridement for early infection, joint aspiration, first and second stage revision. The cost of a minute of theatre time is £12.97, hence the cost of theatre time per patient was £4959. The overall estimated cost per patient for treatment of an infected primary total knee replacement is £16503 (exclusive of implant and antibiotic costs).

Conclusion: the cost of an infected TKR is a substantial financial burden for trusts as well as a catastrophic complication for patients. Methods of reducing expenditure include reduction in hospital stay by administration of antibiotics by district nurses or trained family members, rapid management of early joint infection by washout and debridement with the possibility of avoiding revision surgery and explantation of components upon diagnosis of bone/cement interface infection hence avoiding futile operations.

Aim: to compare the reliability of pre-operative templating for total hip and knee arthroplasty using printed digital radiographs versus conventional radiographs.

Materials and Methods: a prospective continuous study commenced January 2005. The PACS digital imaging system was introduced in May 2005 and the radiology department adopted a policy of printing orthopaedic radiographs to ‘true size’. All consultants and their registrars undertaking primary total hip and knee arthroplasty were asked to participate in the study and agreed. The operating surgeon completed a proforma for each Total Hip Replacement (THR) performed noting the templated cup and stem size and offset. Following the surgery the actual sizes and offset of the components implanted were also recorded on the proforma. A similar procedure was followed for the femoral and tibial components of Total Knee Replacements (TKR).

Results: there were 254 completed proformae. 186 pro-formae for conventional radiographs and 68 proformae for printed digital radiographs. Templating was possible from all the conventional radiographs; however templating was only possible from 58 of 68 (85%) digital radiographs as the images were obviously not true size. The templated sizes of both hip and knee components from conventional radiographs were more predictive of the actual size implanted in all cases. Furthermore there were a greater number of predicted outlying sizes using printed digital radiographs.

Conclusion: digital radiographs, even those said to be true size are unreliable for the purposes of pre-operative planning.

Introduction: There has been a renewed interest in metal-on-metal bearing for total hip replacement with the benefit of a larger head size and decreased incidence of dislocation. In the revision hip scenario cementation of a polyethylene liner, for a previously compromised liner fixation mechanism into a preexisting well-fixed shell or a cage, has become an accepted method to decrease the morbidity of the procedure. Perhaps Bir-mingham cementless cups could be used as cemented devices in primary and revision hip surgery where a cementless cup is not possible.

Aim: To study the pull-out strength of cemented Bir-mingham sockets in an experimental model.

Materials and Methods: Eight Birmingham cups were cemented into wooden blocks after they were reamed to the appropriate size allowing for a 3mm cement mantle, multiple holes drilled into the reamed sockets and cement vacuum-mixed. Cable was then threaded through the holes on the rim of the cup and the wooden block was then mounted on a metal plate and secured. Linear tension was then gradually applied on the cup through the cable.

Results: The pull-out strength of the cemented Birming-ham cups was higher than the failure of the cable. The tensile load to failure for the cables ranged from 3642.6 N to 4960 N with an average load of 4286.9 N.

Conclusion: The average tensile load of 4286.9 is very high compared to previous studies with cemented poly-ethylene and metal liners. This finding is very promising and might support clinical application in complex primary and revision total hip replacement.

Introduction: Aseptic loosening is the commonest complication of cemented total hip arthroplasy. Gaseous voids within the cement mantle are thought to act as stress concentrators and points of origin and preferential fracture propagation at the cement stem interface. Assuming a bone tempereature of 37°C, Bishop recommended heating the prosthesis to 44°C, thereby effecting a reduction in cement-prosthesis interface porosity.

The aim of this study was to (I) determine the intra-operative temperature of the femoral cancellous bed prior to insertion of prosthesis, (II) to investigate whether the magnitude of the temperature gradient effects interface porosity (III) to develop clinically relevant recommendations.

Materials and Methods: (I) The intra-operative determination of femoral cancellous boney bed temperature. Sterile, single use thermocouples (Mon-a-therm) were used to record interface temperature in six patients, after canal preparation and lavage. (II) A simulated femoral model was designed consisting of a waterbath, set at temperature determined by (I) with an inner water-tight chamber formed by 19mm diameter polyethylene tubing. Cement (Palacos) was non-vacuum mixed (to exaggerate porosity) for 1 minute and injected in a retrograde manner into the inner tube at 3 minutes. Femoral stems (Exeter) were pre-heated in a second waterbath to 18, 32,35,37,40,44°C, were thoroughly dried and lowered into the inner tube by a Lloyd universal testing machine via a custom jig. The cement was left to polymerise.

The cement mantle was sectioned transversely, then longitudinally to expose the cement-prosthesis interface. This was stained with acrylic dye to facilitate image analysis. Three mantles for each temperature were produced.

Results: (I) The mean femoral canal temperature was 32.3°C, (II) the effect of stem temperature on interface porosity is shown in fig1.

Conclusions: Bone temperature is 32°C after canal preparation using contemporary cementing techniques. Heating to 35°C reduces interface porosity, heating to 40°C is optimal.

To determine whether resection of osteophyte at TKR improves movement, 139 TKRs were performed on knees with pre-operative posterior osteophyte. Randomisation was to have either resection of distal femoral osteophyte guided by a custom made ruler or no resection. After preparation of the femoral bone cuts the ruler measuring 19 mm was placed just proximal to the posterior chamfer cut. The proximal end of this ruler marked the bone to be resected and this was performed using an osteotome at 45 degrees. Knees randomised to no resection had no further femoral bony cuts. Three months after implantation the patients had range of motion assessed.

One hundred and fourteen suitable knees were assessed, with 59 knees (57 patients) in the resection group and 55 knees (54 patients) in the no resection group. Full extension was more likely in the resection group (62%) than the group without resection (41%)(p=0.08). Flexion to at least 110 degrees was, however, less in the resection group (37%) than the no resection group (54%) (p=0.09).

Our study failed to show a statistically significant difference if the bony osteophyte is removed. There were however sharp trends, with statistically a one in ten chance these results would be different if the trial was repeated. Although there is no indication as to the cause of improved extension this could be explained by the release of the posterior capsular structures allowing full extension. The reduction in flexion is harder to explain and this may be due to increase in perioperative trauma and resultant swelling, possibly with fibrosis. Range of movement, particularly flexion, is known to improve up to 1 year post-operatively and assessment of these groups at that stage would be beneficial.

The aim of this study was to establish the ability of an invasive fibre-optic probe to measure intra-muscular pH, pCO₂, pO₂, HCO₃-⁻, ambient temperature, base excess and O₂ saturation. The secondary aim was to determine the effect of elevation of the limb on these parameters.

Fibre-optic probes were introduced into the anterior compartment muscle of the leg in five volunteers via 16G cannulae. After equilibration the limb was monitored for 11min with the volunteer supine on an examination couch. The limb was elevated to 22cm (Braun frame) and then 44cm for the same time. Subsequently the leg was returned to 22cm and supine. All volunteers followed this set protocol. Continuous recording of all indices was made throughout. Data was stored to a personal computer for analysis.

Similar trends were observed across all subjects for all parameters. The mean pO₂ when lying flat was 27mmHg (S.D.7.4). Elevation to 22cm increased muscle pO₂ to 33 mmHg (S.D. 5.8). Further elevation to 44 cm resulted in a reduction in muscle pO₂ to a level below that measured when supine. When the limb was returned to 22cm the pO2 trend reversed, the level improving. Returning to the supine position the pO₂ returned to the level seen at the start of monitoring.

This novel probe gives reproducible measures of pH, pCO₂, pO₂, HCO₃⁻, ambient temperature, base excess and O₂ saturation. Results indicate that elevation to 22cm improves muscle oxygenation; a height of 44cm seems detrimental. This technique may be applicable in surveillance for compartment syndromes and muscle ischaemia.