Introduction

Knee arthroscopy can be used for ligamentous repair, reconstruction and to reduce burden of infection. Understanding and feeling confident with knee arthroscopy is therefore a highly important skillset for the orthopaedic surgeon. However, with limited training or experience, furthered by reduced practical education due to COVID-19, this skill can be under-developed amongst trainee surgeons.

Abstract

Purpose

Infections in orthopaedic surgery are costly, debilitating complications. The search for new treatments and prevention strategies has led to the use of antibiotic-filled calcium sulfate (CaS) as a bone void filler that is both safe and effective. The purpose of this study was to examine the available data on the efficacy of this technology.

Summary

A meta-analysis was performed to compare rate of SSI after application of chlorhexidine vs. iodine in total joint arthroplasty. Chlorhexidine had significantly lower odds of SSI.

Patients who have multiple sclerosis (MS) may be at increased risk of developing complications after total hip arthroplasty (THA). The purpose of this study was to compare: 1) implant survivorship; 2) functional outcomes; 3) complication rates; and 4) radiographic findings after THA between MS patients and a matched cohort.

A single institutional database was reviewed for patients who had a diagnosis of MS and underwent a THA. Thirty-four patients (41 hips) were matched to a 2:1 cohort who did not have MS using based on age, sex, body mass index (BMI), and Charlson/Deyo scores. This resulted in a matching cohort of 80 patients (82 hips). The available medical records were reviewed. Functional outcomes and complications were assessed. Postoperative radiographs were evaluated.

The matching cohort had higher all-cause survivorship at 4-years postoperatively (99 vs. 93%). There were 3 revisions in the MS cohort and 0 revisions in the matching cohort. The MS cohort had lower mHHS scores (66 vs.74 points, p<0.001), lower HOOS JR scores (79 vs. 88 points, p<0.01), required more physical therapy (5 vs. 3 weeks, p<0.01), and took longer to return to their baseline functional level (7 vs. 5 weeks, p<0.05). MS patients had higher rate of complications (6 vs. 1, p<0.05). Excluding revision cases, there was no additional radiographic evidence of progressive radiolucency, loosening, or subsidence.

We found that MS patients had lower implant survivorship, lower functional outcome scores, and increased complication rates. These findings may help orthopaedists to have a better knowledge of how MS patients do after THA.

Introduction

Stiffness after total knee arthroplasty is a common occurrence. Despite its prevalence, little is known as to which patients are at risk for poor range of motion after total knee arthroplasty. The purpose of this study was to determine the risk factors for manipulation under anesthesia (MUA) after total knee arthroplasty (TKA).

Purpose

The aim of this study was to compare the short-term and mid-term outcome of lateral UKRs using a single prosthesis, the AMC Uniglide knee implant.

Introduction

Kneeling ability is better in unicompartmental than total knee arthroplasty. There is also an impression that mobile bearing knees achieve better functional outcome than their fixed bearing cousins in unicompartmental and to a lesser extent total joint arthroplasty. In the UK, the market leading unicompartmental replacement is mobile bearing.

Introduction

Trochlear dysplasia (TD) is still poorly recognised, generally considered uncommon and to present purely as persistent patella dislocation.

Between 1989 and 1992 102 knees adjudged suitable for Unicompartmental replacement (UKR) were randomised to receive either a St Georg Sled UKR or a Kinematic modular total knee replacement (TKR). The early results demonstrated that the UKR group had less complications, and more rapid rehabilitation. At 5 years there were equal failures but the UKR group had more excellent results and a greater range of movement.

Despite this doubt persisted about whether these advantages would be maintained these cases have been followed regularly by a research nurse at 8, 10, 12 years. We now report the final outcome at 15 years. 43 patients (45 knees) have died with all their knees intact. Throughout the review period the Bristol Knee Scores (BKS) of the UKR group have been better and at 15 years 77% and 53% of the surviving UKRs and TKRs achieve an excellent score. 6 TKRs and 4 UKRs have failed during the 15 years of the review.

Background

Unicompartmental knee replacements (UKR) converted to total knee replacements (TKR) have often been viewed with scepticism because of the perceived difficulty of the revision and because revision procedures generally do less well than primaries.

Introduction

The Bristol Knee Group has prospectively followed the results of over 500 isolated patellofemoral arthroplasties. Initial experience with the Lubinus prosthesis was disappointing. The main causes of failure were mal-tracking and instability leading to excessive polythene button wear and disease progression in the tibio femoral joint.

This experience resulted in the design of a new prosthesis to correct the tracking problems and improve the wear. We have now performed over 425 Avon arthroplasties with a maximum follow-up of 9 years.

Background: Although many knee surgeons routinely perform unicompartmental replacement (UKR) for medial compartment arthrosis there is still reluctance to perform lateral UKR’s as they are generally thought to be less satisfactory. The purpose of the present study was to prospectively compare the outcome of lateral UKR’s with medial UKR’s using the AMC Uniglide knee implant.

Methods: Between 2002 and 2005, 29 lateral fixed bearing AMC Uniglide UKR’s were performed at our unit. American Knee Society (AKS), Oxford and WOMAC scores were recorded pre-operatively and at two years post-op and compared with the results of 50 medial mobile bearing and 50 medial fixed bearing AMC Uni-glide UKR’s performed during the same time period. Data was acquired by a research nurse and recorded prospectively on the Bristol Knee Database. The mean ages of the patients were: 63 years in the lateral UKR group was, 62 years in the medial mobile bearing group and 69 in the medial fixed bearing group. The groups were equally sex matched with a predominate number of females in each group. There was no difference between the pre-operative scores for the 3 groups.

Results: At one-year review, the 3 groups had similar mean scores: (table removed)

Conclusions: This study suggests that at two years the quality of outcome of Lateral UKR’s is at least equivalent to both fixed and mobile bearing medial compartment UKR’s. However, continued long-term survivorship studies are needed to assess failure rates of Lateral fixed bearing UKR’s and particularly to evaluate progression of arthritis in the medial compartment. The procedure should form part of the knee surgeons’ armamentarium, but the differences in the operative techniques for lateral and medial UKR must be appreciated.

Although good long term results for fixed bearing uni-compartmental knee replacements (UKRs) have been reported mobile bearings predominate in some parts of the world. Three prospective studies have been undertaken comparing the short and medium term outcomes of fixed and mobile UKRs.

A 5 year comparative cohort study of 47 Oxford mobile bearing and 57 St Georg Sled fixed bearing UKRs.

In all groups the preoperative sex mix, average age and knee scores were extremely similar.

All patients were assessed both pre and postoperatively by a research nurse and radiographs were taken; the results were entered on the Bristol Knee database.

Results:

Multiple problems were encountered, perhaps because of the introduction of MIS, but at 5 years 11 Oxford and 4 Sleds had failed. The major problem with the mobile bearing implant was instability though tibial fractures were also seen. Both groups had three cases of arthritic progression and loose cement was seen twice in the fixed bearing group.

– Amongst the remaining patients the median scores for the Sled were better. Bristol Knee Score (Max 100) 95:90; Oxford (Max 48) 39:37; and reduced WOMAC (Best score 12) 18:24.

Conclusion. Although theoretically mobile bearings will give greater longevity there is frequently a short term price to pay particularly when the procedures are performed by inexperienced surgeons and trainees. Since the wear properties of polyethylene have improved in recent years these studies suggest that a fixed bearing option can be used more safely in many patients.

Introduction: The Bristol Knee group has performed over 600 patellofemoral arthroplasties in the last 18 years. Experience with the Lubinus prosthesis led to the development of the Avon Prosthesis. In the last 11 years we have prospectively recorded the results of over 470 consecutive Avon arthroplasties. The main cause of the 9.5% failure is arthritic disease progression in the tibiofemoral compartments.

Patients and Method: Over the last 11 years we have identified 21 patients from our own series and from tertiary referrals that have persistent pain, which was mainly due to technical error rather than arthritic disease progression. The causes can be classified into three main reasons: First, an incorrect anterior cut in the saggital plane which was cut in either too much flexion or extension. Second, the anterior cut had inadequate external rotation, which should be 3–6 degrees to lateralise the groove and facilitate correct tracking. Third, the prosthesis was oversized in several cases leading to retinacular impingement.

Results: The overall results followed up to 10 years showed excellent and consistent improvement in both pain and function as judged by the WOMAC 12 scale. Of those patients with persistent pain, seven had the femoral component revised to either resize the prosthesis or revise the alignment of the anterior resection and correctly inset the prosthesis, with good results. Ten cases were revised to a total knee replacement. In the remaining cases, two had an Insall realignment, one a patella distalisation, and in one no treatment was required. As a permanent solution new instruments were designed to reduce the incision size and increase the accuracy of the saggial alignment and to create an exact amount of external rotation.

Conclusion: The lessons from 11 years experience with the Avon arthroplasty has led to the development of improved instrumentation which should reduce the failures.

Objectives: This study aims to assess the psychological profile of patients prior to total knee replacement, medial unicompartmental knee replacement and patellofemoral joint replacement and determine its effect on outcome.

Methods: 113 patients were identified (41 TKR, 37 UKR and 35 PFJR). All patients had mental health assessed preoperatively using SF-12. From the 12 questions a mental and a physical summary score can be calculated (MCS and PCS). The reduced WOMAC score was used pre-operatively to assess knee function and symptoms and then recorded at 8 and 24 months post-operation to assess outcome.

Results: 54% of the patients had pre-operative psychological distress. There was no statistically significant difference demonstrated between them mean MCS scores between the three operation groups. Pre-operative MCS had a significant effect such that increasing psychological distress lead to a worse twenty-four month outcome (p = 0.016). The effect of MCS is most marked in postoperative pain levels (p = 0.008) compared to function (p = 0.016). The mean 24-month rWOMAC in the severely distressed group (MCS< 40) was 28.4 compared to 17.4 in the psychologically well group (MCS> 60).

Conclusions: Pre-operative mental function prior to knee arthroplasty may provide useful information to guide patients as to their expected outcome in the consent process. Those patients with a very high mental component may be counseled to that although their distress is likely to improve with surgery, their eventual outcome may be worse. The effect of MCS may however only be clinically relevant in those patients with severe mental symptoms.

Purpose of Study: Fixed bearing unicompartmental knee replacement (UKR) has become popular since several series have now shown good 10 year survivorship and excellent function. However little is known about survival during the second decade.

Method: From the Bristol database of over 4000 knee replacements 203 St. Georg Sled UKR’s which had already survived 10 years were identified. The mean age at surgery was 67 years (48–85), with 64% being female. This cohort has been further reviewed at an average of 14.8 years (10–30) from surgery to determine survivorship and function.

Results: Survivorship during the second decade was 87.5%. 58 patients (69 knees) had died with implant in situ and only 2 after revision. A further 15 UKR’s have been revised at an average of 13 years post op; 7 for progression of disease in the opposite compartment, 4 for tibial loosening, 3 for polyethylene wear, 2 for femoral component fracture and 2 for infection.

99 knees were followed for 15 years, 21 knees for 20 years and four for 25 or more years. The average Bristol knee score of the surviving knees fell from 86 to 79 during the second decade, largely as a result of aging.

A previous study of the St Georg. Fixed bearing UKR showed an 89% 10 year survivorship and this is now extended to 82% at 15 years and 76.5% at 20 years.

Conclusion: Satisfactory survival of fixed bearing UKR can be achieved in the second decade suggesting that the indications for mobile bearings require careful definition since there is a higher incidence of complications in many people’s hands.

Since 1996 over 400 isolated patellofemoral replacements using the Avon prosthesis have been undertaken in Bristol. As a result of the usually gratifying outcomes seen in patients over 55 years old, the indications for this surgery were soon extended to include the many younger patients who have severely disabling patellofemoral disease. We present results from a prospective cohort study of patients under 55 years of age at the time of surgery.

110 knees in 86 patients (median age 47 years, range 24–54) have been treated with Avon patellofemoral replacement (88 in females and 22 in males). Diagnoses included lateral facet OA (59 knees), patella dislocation (25 knees), trochlear dysplasia (41 knees) and post patellectomy instability (7 knees). 79 knees had undergone previous surgery. 17 knees required additional intra-operative procedures including 11 lateral releases and 2 patella realignments. All patients were assessed pre-operatively and at regular intervals using the Oxford, Bristol and WOMAC scores.

All knees were scored preoperative and only one knee has been lost to follow-up due to the patient’s death, which was unrelated to surgery. Post-operative Oxford knee scores have been obtained for 106 knees with follow-up between 8 months and 8 years (mean follow-up 24 months). The mean Oxford score improved from 18 preoperatively to 31 at latest review. Bristol and WOMAC scores showed similar improvements. 16 knees required post-operative additional procedures including 6 lateral releases, 3 patella realignments and 11 revisions. Of the revisions 5 were for progression of tibiofemoral OA but none of these were knees with trochlear dysplasia. Equally good mean scores were seen when comparing patients with the 3 main underlying pathologies (trochlear dysplasia, patellar dislocation and lateral facet OA). At least 37% of the patients studied had pre-existing trochlear dysplasia and the majority of these patients report onset of symptoms, often patellar dislocation, in the first three decades of life. More than 90% of patients were overweight or obese according to their BMI at the time of surgery.

Many of this type of patient, with disabling symptoms, wish to “live now”. The short-term improvements are frequently dramatic. As yet there is no suggestion of prosthetic failure. Revision presents little difficulty since minimal bone is resected in the primary proceedure. Radiological deterioration of the tibio femoral joint is seen in some cases of primary OA but not with trochlear dysplasia.

Between 1989 and 1992 we had 102 knees suitable for unicompartmental knee replacement (UKR). They were randomised to receive either a St Georg Sled UKR or a Kinematic modular total knee replacement (TKR). The early results demonstrated that the UKR group had less complications and more rapid rehabilitation than the TKR group. At five years there were an equal number of failures in the two groups but the UKR group had more excellent results and a greater range of movement.

The cases were reviewed by a research nurse at 8, 10 and 12 years after operation. We report the outcome at 15 years follow-up. A total of 43 patients (45 knees) died with their prosthetic knees intact. Throughout the review period the Bristol knee scores of the UKR group have been better and at 15 years 15 (71.4%) of the surviving UKRs and 10 (52.6%) of the surviving TKRs had achieved an excellent score. The 15 years survivorship rate based on revision or failure for any reason was 24 (89.8%) for UKR and 19 (78.7%) for TKR. During the 15 years of the review four UKRs and six TKRs failed.

The better early results with UKR are maintained at 15 years with no greater failure rate. The median Bristol knee score of the UKR group was 91.1 at five years and 92 at 15 years, suggesting little functional deterioration in either the prosthesis or the remainder of the joint. These results justify the increased use of UKR.

Background: In the UK 80% unicompartmental knee replacements(UKRs) and 10% of total knee replacements(TKRs) use mobile bearings. It is suggested that mobile bearings are more physiological and wear less, however it is still unclear whether patients tolerate mobile bearing knee replacements as well.

Patients and methods: We report four prospective studies,. Two compared fixed with mobile bearings in TKR and two in UKR. The prostheses involved were fixed and mobile variants of the Rotaglide (TKR), Kinemax (TKR) and Uniglide (UKR). In addition the Oxford and St. George Sled UKRs were compared. All except the Uniglide study were randomized prospective trials (RCTs)

611 patients were involved with a mean age of 68 years. Residual pain following surgery was assessed with either the Oxford Knee Score (OKS) or the WOMAC score. The patients were followed up at one and two years postoperatively by a Research nurse and the findings recorded prospectively on the Bristol Knee database.

Results:

Conclusion: Our data suggests that the fixed bearing knee replacements result in less residual pain than their mobile bearing counterparts, at least in the first two years following surgery.

Purpose: To review long-term outcome following knee arthrodesis, and compare this with patient outcome following revision knee arthroplasty.

Methods: Case notes and radiographs of patients who underwent arthrodesis using the Mayday nail were reviewed retrospectively for evidence of clinical and radiological union. Patients also completed an SF12 health survey and Oxford knee score in the form of postal questionnaires. Each patient was matched with patients who had undergone revision knee arthoplasty and the outcomes were compared.

Results: 19 patients were reviewed who underwent knee arthrodesis using a Mayday nail in two centres between 1993 and 2004. 18 cases had united clinically and radiologically with one case lost to follow-up. Mean SF12 scores of patients following knee arthrodesis indicated severe physical (28.8) but only mild mental (43.3) disabilities. The mean Oxford knee score in this group was 41.0. These results were comparable with matched patients following revision knee arthroplasty who scores 27.2 (physical) and 41.1 (mental) on the SF12, and a mean of 38.8 on the Oxford knee score.

Conclusion: Outcome scores following knee arthrodesis were similar to those following revision knee arthroplasty making it an option worth considering in selected patients requiring revision surgery.

Discussion: The Mayday nail provides a method of knee arthrodesis with a high union rate and an acceptable complication rate. Outcome scores following arthrod-esis were not dissimilar to those following revision total knee replacement. These results suggest that knee arthrodesis may be considered as an acceptable alternative to complex knee revision surgery.

Background: We have noted a concerning number of early failures (as defined by revision) for Preservation medial mobile-bearing uni-compartmental knee replacements (UKR’s) implanted in our hospital. This study retrospectively reviewed the postoperative radiographs to see if these were as a result of surgical technical failure.

Methods: Between 2003 and 2004, 43 medial mobile-bearing Preservation UKR’s were implanted into 39 patients. The average age of the patients at the time of the index procedure was 61.4 years (range, 46–85), (20 males). The immediate post-operative radiographs were reviewed by 2 independent orthopaedic consultants and a registrar, who were blinded to the patient outcomes, using the radiographic criteria used for the Oxford UKR. We however, particularly tried to identify any medio-lateral offset between femoral and tibial components due to the constrained nature of the prosthesis. A compound error score for all other technical errors was also calculated for each patient.

Results: Six (13.9%) of 43 knees were revised (5 for persistent pain, 1 for tibial component subsidence). Technical errors were few and no correlation was found between post-operative radiographic appearances and the subsequent need for revision. The mean compound error score (maximum value 18) was 4.5 (range, 2–9) in the revision cases and in the non revised cases 3.2 (range, 0–8).

Conclusions: We believe this study gives credence to the opinion that the DePuy Preservation mobile-bearing implant has design faults and is over-constrained leading to early failures in some cases.

Medial unicompartmental replacement (UKR) has been shown to have superior functional results to total knee replacement (TKR) in appropriately selected patients, and this has been associated with a resurgence of interest in the procedure. This may relate to evidence showing that the kinematic profile of UKR is similar to the normal knee, in comparison to TKR, which has abnormal kinematics. Concerns remain over the survivorship of UKR and work has suggested the anterior cruciate ligament (ACL) may become dysfunctional over time. Cruciate mechanism dysfunction would produce poor kinematics and instability providing a potential mechanism of failure for the UKR.

Aim: To test the hypothesis that the sagittal plane kinematics (and cruciate mechanism) of a fixed bearing medial UKR deteriorate over time (short to long term).

A cross sectional study was designed in which 24 patients who had undergone successful UKR were recruited and divided into early (2–5 years) and late (> 9 years) groups according to time since surgery. Patients performed flexion/extension against gravity, and a step up. Video fluoroscopy of these activities was used to obtain the Patellar Tendon Angle (PTA), the angle between the long axis of the tibia and the patella tendon, as a function of knee flexion. This is a previously validated method of assessing sagittal plane kinematics of a knee joint.

This work suggests the sagittal plane kinematics of a fixed bearing UKR is maintained in the long term. There is no evidence that the cruciate mechanism has failed at ten years. However, increased tibial bearing conformity from ‘dishing’, and adequate muscle control, cannot be ruled out as possible mechanisms for the satisfactory kinematics observed in the long term for this UKA.

Purpose: This study was carried out to compare the alteration in skin sensation following midline, medial and short medial incisions for knee replacement.

Method: 88 patients with 102 replaced knees were examined for altered skin sensation over the front of the knee, all were at least 18 months from their knee replacement. Twenty-one knees had a medial incision, 38 a midline incision and 43 a short medial incision for UKR.

A scale of −2 to +2 was used to measure different degrees of skin hypo or hyperaesthia. A purpose-designed grid, designed to fit different knee sizes, was used to record sensations. A computer programme was created to record all patients’ data including the length and shape of the incision in relation to anatomical landmarks.

A parallel histological study was carried out on 18 skin specimens taken from the 2 standard incisions. The specimens were prepared and stained for nerve endings. The number of nerve endings in each incision was calculated.

Results Histologically, less cutaneous nerve endings were seen in specimens from midline incisions than medial incisions.

Discussion: Altered skin sensation is unpleasant to many patients at least initially and may affect function especially kneeling. The midline line incision seems to produce less dermal parasthesia than the medial incision, this probably relates to both the wound position and the density of nerve endings. As expected, the length of incision correlated with the area of numbness when comparing short and long medial incisions.

Introduction: This study assesses the prevalence of trochlear dysplasia as a cause of patello-femoral arthritis (PFOA), though for many years the condition was scarcely recognised and not recorded.

Method: Since 1989 385 primary isolated patello-femoral replacements have been performed in Bristol for patello-femoral arthritis.

The diagnoses recorded were:

Lateral facet PFOA 227

Symmetrical PFOA 95

Medial facet PFOA 24

Dislocation 15

Subluxation 33

Post traumatic 6

Trochlear dysplasia was noted either retrospectively or as “other diagnosis” in only 10 cases between 1989 and 2003, however in the last year, the condition became recognised locally, and has been recorded in 11 of the 48 cases performed.

A recent review of 40 cases aged under 55 showed evidence of causative trochlear dysplasia in more than 50%.

This was based on:

Trochlear dysplasia recorded on operative note 8

A positive crossing sign on a true lateral xray 19

A sulcus angle > 144° 20

Conclusion: Trochlear dysplasia frequently leads to severe symptomatic patello-femoral arthritis, often at an early age, and can be helped by isolated patello-femoral replacement. Since only 38 of the 385 cases had undergone re-alignment procedures it seems likely that the condition initially presents in a variety of ways.

Introduction: Progressive symptomatic tibiofemoral arthritis following PFJR is an important cause of failure. This study is designed to quantify radiologically the degree of tibiofemoral disease progression in patients who have undergone PFJR in our institution.

Patients and Methods: A prospective series of 102 consecutive Avon PFJRs in 78 patients with a minimum follow-up of five years was analysed.

Available AP weight bearing radiographs of the knee taken at 8 months and 5 years postoperatively were examined in a random order twice by each of two surgeons who were blinded to the patient details and length of follow up. The severity of arthritis was graded using the classifications of Ahlback and Altman, giving a measure of arthritis progression.

Results and Discussion: Arthritis was seen to progress in 8.5–17% of medial and 11–17% of lateral compartments after PFJR. Statistically significant progression was demonstrated using the Altman but not the less sensitive Ahlback scoring system, suggesting that the former should be used in scoring the tibiofemoral joint prior to PFJR. Of those patients who had a preoperative tibiofemoral Altman score of zero, 87% showed no radiological evidence of disease progression at minimum 5 year follow up, suggesting that these are the ideal candidates for PFJR.

Aim: The Low Contact Stress (LCS) Total Knee Replacements (TKR) is a well-established mobile bearing prosthesis with more than 25 year experience, while the Kinemax Plus is a well established fixed bearing prosthesis. We examined whether reproducing the joint line height to within 5 mm of the pre-operative joint line height had any impact on the clinical outcome in the two different types of Total Knee Replacements.

Method: 48 consecutive LCS knee replacements with a minimum of 2 years follow up had their pre and postoperative joint line (using Figgie’s method) and range of movement (ROM) measured. We used the Oxford Knee Score as a clinical outcome measurement tool.

A cohort group of 53 CR Kinemax plus TKR from the Bristol Knee group was matched for age and sex. They had the same parameters measured.

Results: Accurate joint line restoration was achieved significantly more frequently (P< 0.05) in the Kinemax group. Better post-operative ROM also occurred in the Kinemax group than the LCS, p = 0.03 and the former produced a bigger gain in ROM p < 0.01. However, no difference in the Oxford Knee Score existed between the two prostheses, p = 0.28.

Joint line: elevation K+ LCS

0–2 mm (16/48) = 33% (26/53) = 49% 2–5 mm (14/48) = 29% (14/53) = 26%> 5 mm (18/48) = 38% (12/53) = 25%

There was no significant difference in the ROM or Oxford Knee Score when the joint line was not elevated versus elevated for each prosthesis. However, there was suggestion that the ROM in LCS might be more sensitive to joint line changes, although this was not significant.

ROM

K+ LCS

Normal joint line 116° 105°

Elevated joint line 108° 101°

Conclusion: Accurate joint line restoration could not be shown to correlate with either improved ROM or Oxford knee score; probably because of the small mount of elevation encountered and the small study size. There was a significantly greater post-operative increase in ROM with the Kinemax Plus relative to the LCS, and a significantly closer restoration of the joint line with the Kinemax Plus, both with respect to the actual measurement and with respect to the proportion of cases in which the joint line was accurately reproduced. This is surprising since in most K+ cases additional distal femur had been resected to avoid a tight knee. While in the LCS group special efforts had been made to achieve accurate restoration of the joint level.

Introduction Unicompartmental Knee Replacement (UKR) has now become an accepted and widely used treatment for unicompartmental arthritis. Our unit has performed over 1000 UKRs in the past 22 years. The optimal mechanical design of the implant has yet to be determined.

Methods After gaining ethical approval a prospective randomised trial was commenced in 1999 to compare the 2–5 year results of a fixed bearing with a mobile bearing prosthesis. 104 knees in 91 patients underwent a UKR, the mean age of the group was 65 years and a mean weight of 80kg. 57 had a St Georg Sled fixed bearing prosthesis and 47 an unconstrained mobile bearing Oxford UKR. All were prospectively reviewed using the Oxford and Bristol Knee Scores.

Results All 104 knees have been reviewed at 2 years, with none lost to follow-up. 3 patients in the Oxford group suffered a dislocated meniscus and a further 4 required revision, as well as 3 in the St Georg Sled group. The overall function of the 2 groups was the same, but the Oxford mobile bearing group had significantly more persistent pain (p=0.013).

Conclusion The results in both groups were less satisfactory than previous series from this unit probably due to the efforts being made to use minimal incision. However the early complication rate was higher with the mobile bearing devise. This must be balanced against the possible better long-term survival.

Introduction: Isolated patello-femoral arthritis occurs in up to 10% of patients suffering osteoarthritis of the knee. Reports of patello-femoral replacements have given indifferent results. We report our experience of 350 cases of the Avon Arthroplasty.

Method: In 1994 after experience with the Lubinus prosthesis which had a 50% failure rate at eight years, we defined the design criteria for a new prosthesis. Since September 1996, 350 knees have been treated with this design. Prospective review was undertaken and 150 knees have reached 2 years and 80 knees are at five years with 10 knees at eight years. The outcome was assessed using pain scores, Bartlett’s patella score and the Oxford knee score.

Results: The patients recovered function rapidly and 20 cases (6%) suffered early complications which resolved. The median pain score improved from 15/40 points to 38 at five years. The movement increased from 114 to 120 at five years. The Bartlett patella score improved from 11/30 points to 25 at five years. The Oxford knee score improved from 19/48 points to 40 points at five years.

The functional results are similar or better than those of a total knee replacement. Fourteen patients developed mal-alignment (4%) two of which required distal realignment. There have been no cases of deep infection, fracture, wear or loosening. Twenty seven knees (7%) developed evidence of disease progression, twenty two of which (6%) have required revision to a total knee replacement. Nineteen patients (5%) complained of some persistent anterior knee pain of uncertain cause.

Conclusions: Results to date show a large improvement in pain and function and this improved design has reduced the problems of mal-alignment and polythene wear. There is a low complication rate and an excellent range of movement. Disease progression remains a problem which is not predictable. This type of prosthesis offers an alternative to total knee replacement in this small group of patients with isolated patello-femoral disease with a low morbidity.

Introduction: Proximal femoral fracture (PFF) is the leading cause of Trauma admission. Deep surgical wound infection occurs in approximately 3% of these patients. The purpose of this study was to assess the cost of deep infection to the patient, in terms of mortality and social consequences, and to the National Health Service, in terms of financial burden.

Methods: 61 consecutive patients (51 females, 10 males) treated for PFF, complicated with deep surgical wound infection over a seven-year period are presented. A control group consisting of 122 patients, without infection, were individually case matched (2:1) for factors that affect outcome after PFF (age, sex, ASA grade, fracture type, operation, and pre-fracture residence, social dependence, and mobility). Outcomes included length of admission (Trauma unit, rehabilitation bed, community hospital), number of operations, antibiotic administration and outpatient treatment, final destination, and mortality at one, three, and six months. A total cost of treatment was obtained from this data and supplied finance department figures.

Results: MRSA was responsible for 31 cases. Infected cases required an average of two wound debridements. 16 patients had a Girdlestones procedure of whom two were subsequently revised to total hip replacement. For all patients, the average Trauma unit admission was 58 days in the infected cases, with a further 40 days spent in rehabilitation or community beds, versus 16 days and 27 days respectively in the controls (p < 0.001). 34% of infected cases died before discharge versus 15% of controls (p = 0.004). For the patients surviving to discharge, the mean total hospital stay was 124 days for the infected cases versus 45 days in the controls (p < 0.001). A higher proportion of the survivors in the control group returned to their original residence compared to the infected survivors (p = 0.002). The mortality rates in the infected group were 15% at 1 month, 31% at 3 months, and 38% at six months, versus 9%, 20%, and 25% respectively in the control group (p = 0.36, 0.12, 0.12). The median cost of treatment per infected case was 23960 versus 7390 per control case.

Conclusions: Deep surgical wound infection after proximal femoral fracture is a devastating complication for both the patient and the NHS. It is associated with a higher in-patient mortality, and fewer survivors return to their pre-fracture residence. Hospital stay is greatly increased and survivors spend 4 months on average in hospital. Additional costs are huge and are incurred at all levels. The extra financial cost of treating a single infected case would fund the treatment of two non-infected cases. These costs should be considered when allocating funds and beds to Trauma services, in addition to ensuring measures known to minimise infection rates are in place.

Introduction. There has been a recent major increase in the use of unicompartmental knee replacement (UKR) but few studies exist comparing its long term efficiency with total knee replacement (TKR)

Method. Ethical approval was obtained.

Between 1989 and 1992 a randomised prospective study was undertaken in which 102 cases adjudged suitable for UKR were allocated to receive either a St Georg Sled UKR or a Kinematic Modular TKR. Both cohorts had a median age of 68 and a similar sex distribution and preoperative knee score. Regular follow up has been maintained. As reported the early results favoured UKR. All cases have now been assessed after a minimum of 10 years using modified WOMAC, Oxford and Bristol Knee Scores (BKS) as well as radiographs.

Results. 28 cases had died with their knees known to be intact, 2 cases were untraceable. 33 knees in each group were reviewed. 3 in each group had been revised, no impending failures were identified on the radiographs.

At 10 years the UKR group had better Oxford and WOMAC scores as well as significantly more excellent results (19:14) and fewer fair and poor results on the BKS. Both groups averaged over 105′ of flexion but 61% of the UKR and only 15% of the TKR group had 120′ or more of flexion.

Conclusion. The faster rehabilitation and better early results with UKR are maintained for 10 years with few failures occurring. The average BKS of the UKR group only fell from 91 to 88 between 5 and 10 years suggesting minimal evidence of functional deterioration in either the prosthesis or the remainder of the joint.

Introduction and Aims: Single compartmental replacement procedures are increasingly preferred over total knee replacement (TKR) for single compartment osteoarthritis of the knee joint. Theoretically, reduced disruption of the native joint should produce more normal kinematics. This study aimed to describe and compare the sagittal plane kinematics of four different, commonly used devices.

Method: Four groups of patients who had undergone successful single compartment replacement at least two years previously were recruited. Fifteen following Oxford medial UKA, 12 following medial St Georg Sled UKA, five following Oxford lateral UKA, and 12 following Avon PFJ replacement. Patients performed flexion/extension against gravity, and a step-up during video fluoroscopy. The Patellar Tendon Angle (PTA), the angle between the long axis of the tibia and the patella tendon, was obtained as a function of knee flexion. This relationship provides indication of sagittal movement between femur and tibia through range and has been validated as a reliable measure of joint kinematics.

Results: The kinematic profile for each group was compared to that of the profile for 12 normal and 30 TKR (AGC) knees. All three tibiofemoral devices produced knee kinematics similar to the normal knee. The PTA was found to have a linear relationship to flexion angle, decreasing with increasing knee flexion angle. No such linear relationship exists for the TKR joint, which display abnormal kinematics. The PF device also reflected similar trends to that for normal knees except that the PTA was moderately increased throughout the entire range of flexion (three degrees).

Conclusion: In contrast to TKR, all single compartmental knee replacements provided kinematics similar to the normal joint. The kinematic pattern of the PFJ replacement may be of most interest as the observed increase in PTA through range could influence patello-femoral contact forces

Introduction: Uni-compartmental Knee Replacement (UKR) has now become an accepted and widely used treatment for uni-compartmental arthritis. Our unit has performed over 1000 UKRs in the past 22 years. The optimal mechanical design of the implant has yet to be determined.

Method: A prospective trial was commenced in 1999 to compare the short-term results of a fixed bearing with a mobile bearing prosthesis. One hundred and three knees in 95 patients underwent a UKR. Fifty-three had a St Georg Sled fixed bearing prosthesis and 50 had unconstrained mobile bearing Oxford UKR. All were prospectively reviewed using the Oxford and Bristol Knee Scores.

Results: Eighty-four knees have been reviewed at two years with one lost to follow-up. One fixed (2%) and six mobile (12%) bearing knees had been revised. Three fixed bearing and eight mobile bearing knees were dissatisfied because of stiffness or persistent pain and seven mobile bearing knees had undergone further minor procedures, usually for dislocation. At two years, the Bristol and Oxford knee scores for fixed bearing were better than the mobile bearing knees at 90:83 /100 and 38:33 /48 respectively.

Conclusion: There were more early complications in the mobile bearing UKR group, but the functional results were slightly better than in the fixed bearing knees.

Introduction and Aims: There has recently been an increase in the use of uni-compartmental knee replacement (UKR), but there are few studies comparing its long-term efficacy and survival with total knee replacement (TKR). We reported the five-year results of a randomised trial which showed that uni-compartmental replacement had a faster rehabilitation and better functional results than total replacement. We now report the 10-year results.

Method: After obtaining ethical approval, between 1989 and 1992, 102 cases judged suitable for UKR were randomly allocated to receive either a St Georg Sled UKR or a Kinematic Modular TKR. Both cohorts had a median age of 68 and a similar sex distribution and pre-operative knee scores. Regular follow-up has been maintained. All cases have now been assessed after a minimum of 10 years using modified the WOMAC, Pain, Oxford and Bristol Knee (BSK) scoring systems as well as radiographs.

Results: At 10 years, 29 cases had died with their knees known to be intact, two totals cases were untraceable. Thirty-two uni`s, and 34 totals were available for review. Three uni`s (6%) and two totals (4%) had been revised; there was one impending total failure on the radiographs.

The UKR group had better scores with Oxford: 38 v 34 /48 and WOMAC: 17 v 21 /60 and more excellent results (19 v 14) and fewer fair and poor results on the BKS (4 v 6). The range of movement improved in UKA`s from 107 degrees to 117 degrees, whereas the range decreased in TRK`s from 107 degrees to 104 degrees. Sixty-one percent of the UKR and only 16% of the TKR group had more than 120 degrees of flexion.

Conclusion: The St Georg Uni-compartmental arthroplasty continues to function well at 10 years, with better functional scores and a better range of movement than the Kinematic Total arthroplasty. There were similar failures in both groups.

Introduction: Isolated patello-femoral arthritis occurs in up to 10% of patients suffering osteoarthritis of the knee. Reports of patello-femoral replacements have given indifferent results so we wish to report our experience of 326 cases using two different protheses.

Method: In 1989 we started a prospective series of the Lubinus prosthesis. The results of 76 cases at eight years showed a 50% failure rate. The main reasons for failure were malalignment, wear and disease progression. The Avon patello-femoral arthroplasty was designed to solve some of these problems.

Since September 1996, 250 knees have been treated. Prospective review was undertaken and 120 knees have reached two years and 40 are at five years. The outcome was assessed using pain scores, Bartlett’s patella score and the Oxford knee score.

Results: The median pain score improved from 15/40 points to 35 at five years. The movement increased from 114 to 120 degrees at five years. The Bartlett patella score improved from 10/30 points to 26 at five years. The Oxford knee score improved from 19/48 points to 40 points at five years.

The functional results are similar to those of a total knee replacement. Two patients developed malalignment (1%) one of which required distal soft tissue realignment. There have been no cases of deep infection, fracture, wear or loosening. Sixteen knees (6%) developed evidence of disease progression, 14 of which (6%) have required revision to a total knee replacement.

Conclusions: Results to date suggest that this improved design has reduced the problems of malalignment and early wear. There is a low complication rate and an excellent range of movement. Disease progression remains a problem that is not predictable. This type of prosthesis offers an alternative to total knee replacement in this small group of patients with isolated patello-femoral disease with a lower morbidity.

Introduction and Aims: Our experience with over 200 cases of Avon patellofemoral replacement (PFR) in the elderly with severe arthritis has been satisfactory, so we have extended the indications to younger patients with severe symptoms and various pathologies.

Method: Sixty-six knees in 53 patients (10M: 46F) under the age of 55 years (average 47 years) have been treated with an AVON PFR for the following conditions:

PATHOLOGY NUMBER of Knees

Isolated lateral facet OA 34

Failed realignment 12

Persistent subluxation/dislocation 5

Trochlear dysplasia 5

Pure chondral disease 3

Failed carbon fibre implant 3

Post-patellectomy instability 3

Post-traumatic pain 1

All patients were recorded prospectively and have been regularly reviewed using the modified Oxford, Bartlett & Bristol Knee scoring systems. The mean follow-up of the group is 24 months.

Results: No patient has been lost to follow-up, all knee scores improved substantially.

Most of the patients retained their range of flexion and the mean range of movement increased from 112 to 122 degrees. Patients with persistent subluxation were the most dramatically improved. There have been no cases of deep infection, loosening or wear.

Conclusion: Avon PFR provides a reliable short-term solution to some of the more difficult and disabling problems of the patello-femoral joint as long as demonstrable pathology is present.

Introduction and Aims: Kneeling is an important function of the knee joint but little information is available on ability to kneel after different types of knee arthroplasty. We aimed to assess patients’ kneeling ability pre- and post-operatively after uni-compartmental, patellofemoral and total knee arthroplasty (UKR, PFR, TKR) and to objectively examine: kneeling ability, factors that affect it and whether this ability differed from the patient’s perception.

Method: In 253 knee arthroplasty cases, we prospectively analysed the ability to kneel pre-operatively, and post-operatively at one and two years using the relevant section of the Oxford Knee Score questionnaire. One hundred and twenty-two post-operative patients (38 TKR, 53 UKR, 31 PFR) were then examined to assess their actual kneeling ability.

Results: Patients’ perception of their kneeling ability prior to surgery was poor in all three groups (mean score 0.7 out of 4) and improved in all groups after surgery (mean score at two years 1.46 out of 4). Perceived kneeling ability was best in UKR and worst in PFR (P< 0.001). Perceived kneeling ability improved most in the first year post-operatively, but continued to improve between one and two years although the final kneeling function was still not good. When examined, only 37% of patients thought they could kneel, whereas 81% were actually able to kneel (P< 0.001). Ability to kneel was significantly better than perceived ability for all prosthesis types (P< 0.001). Kneeling ability was better in men and associated with an increased range of movement (P< 0.001).

Conclusion: Kneeling ability is poor prior to knee arthroplasty and improves up to two years post-operatively, though it is still perceived to be poor, but can be improved with rehabilitation. UKR gave better kneeling ability than PFR or TKR. Patient-centred questionnaires do not accurately document kneeling ability after knee arthroplasty.

Purpose This study was carried out to compare the alteration in skin sensation following midline, medial and short medial incisions for knee replacement.

Method 88 patients with 102 knees were examined for altered skin sensation over the front of the knee, all were at least 18 months from their knee replacement. Twenty-one knees had a medial incision, 38 a midline incision and 43 a short medial incision for UKR.

A scale of −2 to +2 was used to measure different degrees of skin hypo or hyperaesthia. A purpose-designed grid, designed to fit different knee sizes, was used to record sensations. A computer programme was created to record all patients’ data including the length and shape of the incision in relation to anatomical landmarks.

A parallel histological study was carried out on 12 skin specimens taken from the 2 standard incisions. The specimens were prepared and stained for nerve endings. The number of nerve endings in each incision was calculated.

Results The average length for the medial incision was 17 cm with an average post-operative time of 3.37 yrs and skin numbness of 87.78 cm square.

The midline incision average length was 17.85 cm with an average post-operative time of 4.7 yrs and a numb area of 73.7 cm square.

The short medial incision used for UKR averaged to be 9 cm in length with an average post operative time of 3.9 yrs and an area of numbness of 48.1 cm square.

Histologically less cutaneous nerve endings were seen in specimens from midline incisions than medial incisions.

Discussion The midline line incision seems to produce less dermal parasthesia than the medial incision, this probably relates to both the wound position and the density of nerve endings. The length of the incision correlated with the area of numbness when comparing the short and long medial incisions.

Aim: The aim of this study was to evaluate the functional results and ease of performing revision surgery after a primary unicompartmental arthroplasty versus primary total knee arthroplasty.

Method: 114 revision TKRs had data collected prospectively as part of our unit’s Knee Database. 45 were revisions of UKR’s and 79 revisions of TKR’s. This data included Bristol Knee Scores (BKS), reason for revision, use of implant augments and bone graft. Measurements were also made of the ability to restore joint-line after revision.

Results: In both groups there was a significant improvement in BKS post-operatively. In the UKR group the commonest reason for revision was progression of disease, while in the TKR group it was aseptic loosening. Bone graft was required in significantly fewer UKR cases (20% vs 40%, P< 0.05). Distal femoral augments were used in 45% of the TKR revisions but in none of the revisions from UKR. The joint line was elevated in a significantly higher proportion of revision from TKR cases versus revision from UKR cases (P< 0.001). Revisions from UKR had higher Total BKS and Functional BKS score than revisions from TKR.

Conclusions: Revision TKR after a primary UKR requires less bone graft, fewer augments, restores the joint line more frequently and gives improved functional results over revisions after primary TKR.

Aim: To assess the functional results of revision TKR with the PFC/TC3 system, and to correlate this with the reasons for revision and restoration of joint height. Method: 153 patients underwent revision TKR using the PFC/TC3 system. Data was prospectively collected (using the Bristol Knee Score) pre-operatively and at a mean of 4.2 years post-revision. 43 revisions were for infection and 81 revisions were for aseptic loosening. Measurements of the joint height were made pre and post-operatively using FiggieÔs method and were divided into 3 groups: lower by more than 5mm, restored and elevated more than 5mm. Use of distal augments and polyethylene thickness were recorded. Results: The mean pre-op function score was 12 and post-operatively was 19 for the infection group and 20 for the aseptic loosening group. Revision after initial UKR gave a mean score of 21, while revision after TKR gave a mean score of 18 (max 27). Knees in which the joint line was elevated by more than 5 mm had a mean score of 17 while those where the joint line was restored had a mean score of 19. Recent increasing use of distal augments improved the joint line and results. Conclusion: revision using the PFC/TC3 system produced acceptable medium term functional results and good survival. Better restoration of joint line and functional results were achieved by distal femoral rather than proximal tibial augmentation.

Aims: To investigate whether normal statistical ßuctuation in the incidence of early complications of primary Knee Arthroplasty (TKA) follows the laws of statistical probability and can thus be amenable to analysis by standard Statistical Quality Control (SQC) methods. The þnal objective is to apply such techniques to distinguish random ßuctuation from real (undetected by traditional p value statistical methods) increase in the incidence of early complications in primary joint Arthroplasty. Methods: We employed statistical quality control charts (X-bar, p, c, u and np) to analyse postoperative complications and length of stay in 1,196 consecutive primary TKAs performed over a 20-quarter time period (October 1995 to September 2000). For all analyses (Minitab 12.1 software) the standard practice of employing ± 3 standard deviation upper and lower control limits and generally accepted criteria for determining the presence or absence of statistical control were used. Results: Deep infection, major thromboembolic incident, total number of complications per case and total number of complicated cases appeared to be in stable statistical control and followed the laws of statistical ßuctuation throughout the entire study period. However, patella mal-tracking, persistent knee stiffness, postoperative length of stay and total number of postoperative complications showed an (undetected by conventional postoperative audit methods) lack of control at various time periods with subsequent return to the statistically-controlled range. Conclusions: SQC methods may be employed in the audit of postoperative events in TKA and can be a valuable tool in continuous assessment of the statistical variability of postoperative complications, with the aim of reducing the variability and improving clinical outcome Arthritic knee imaging

Introduction: Lateral uni-compartmental knee replacement (UKR) is seldom indicated and remains controversial. It has been considered a technically challenging operation with variable success. Aim: The aim of this paper is to assess the results of unicompartmental knee replacement using a þxed noncongruous prosthesis. Methods: Eighty-eight knees in 79 patients with lateral unicompartmental osteoarthritis treated with a þxed bearing, non-congruous, fully unconstrained prosthesis. (St Georg Sled UKR) over a period of 21 years by different consultants and there trainees. Surgical approach and rehabilitation protocol varied over this period but there was no change in the surgical indications. Results: At a mean follow up of 9 years (range 2 to 21 years). Fifteen knees had revision surgery (9 for progression of arthritis and 6 for component loosening, 4 for implant breakage and 4 for more than one reason). Six patients complained of moderate or severe pain at þnal follow up. Only þve knees were lost to follow up in the 21-year period. Survivorship analysis was performed on the group using revision for any cause as the end point. At ten years the cumulative survival rate was 83% and at 15 years, when ten knees were still at risk, the cumulative survival rate was 74%. Conclusion: Based on our clinical results and survival rate the St Georg Sled UKR can be considered a suitable treatment for isolated lateral compartment osteoarthritis.

Isolated patello-femoral arthritis occurs in up to 10% of patients suffering osteoarthritis of the knee. Previous reports of several different patello-femoral designs have given indifferent results. The Lubinus prosthesis has a reported 50% failure rate at eight years in a study of 76 cases. The main reasons for failure were mal-alignment, wear, impingement and disease progression. The Avon patello-femoral arthroplasty was designed to solve some of these problems.

The first cases were implanted in September 1996 and entered into a prospective review. The outcome was assessed using pain scores, Bartlett’s patella score and the Oxford knee score. To date 207 knees have been treated and 95 knees have reviewed at two to five years. The median pain score improved from 15/40 points to 35 at five years. The movement increased from 114° to 120° at five years. The Bartlett patella score improved from 10/30 points to 26 at five years. The Oxford knee score improved from 19/48 points to 40 points at five years. Two patients developed mal-alignment (1%) one of which required distal soft tissue realignment. There have been no cases of deep infection, fracture, wear or loosening. Fifteen knees (7%) developed evidence of disease progression, twelve of which (6%) have required revision to a total knee replacement. The functional results are similar to those of a total knee replacement.

Results to date suggest that this improved design has all but eliminated the previous problems of mal-alignment and early wear. The functional results are as good as or better than those of a total knee replacement. There is a low complication rate and an excellent range of movement. Disease progression remains a potential problem. This type of prosthesis offers a reasonable alternative to total knee replacement in this small group of patients with isolated, early patello-femoral disease.

The Bristol Knee Replacement Registry was established in the 1970’s and contains prospectively recorded data on 3024 patients. The present study examines the group of 812 patients for whom complete pre-operative and five year post-operative data is available in order to relate their eventual health status to the pre-operative demographic data and to disease severity. The group comprised 593 women and 219 men who had undergone either Kinematic, Total or Sled unicompartmental knee replacement.

Pre-operatively, the average American Knee Society Score (AKSS) was 89 with the elderly, rheumatoid patients and women having significantly lower scores.

Five years later the average AKSS had risen to 161 with patients of all ages, (including the over 80’s) gaining considerably. However, the rheumatoid patients remained more disabled as did women who had a final AKSS of 157 as opposed to 171 for the men (p< 0.01). In addition, a statistically significant finding was that those with the lowest pre-operative scores also had the lowest 5 year scores - they never catch up.

173 patients underwent bilateral knee replacement at separate times. Their pre-operative AKSS was significantly higher at the time of the second knee replacement (90) than the first (82) p< 0.01.

We conclude that since patients present earlier for their second TKR and those with most disability fail to catch up the procedure should be performed earlier in the natural history of the disease, especially in women.

In Total Knee Arthroplasty (TKA) and Total Hip Arthroplasty (THA) the total blood loss is composed of ‘visible’ blood loss from the surgical field and wound drainage, and blood loss into the tissues which is ‘hidden’. Blood management should be aimed at addressing the total blood loss.

56 TKAs and 46 THAs were prospectively studied. TKAs were performed with tourniquet. After tourniquet release, all drained blood was salvaged and significant volumes reinfused. No reinfusion was used for THAs.

The true total blood loss was calculated in the following way:

Patient Blood Volume (PBV) is: [1]

PBV = k1 x height3 + k2 x weight + k3

Therefore patient total Red Blood Cell volume (RBCv) is:

RBCv = PBV x Hct. (where Hct is Haematocrit)

Total RBCv loss = PBV x (Hct preop – Hct postop) + ml RBC transfused

The result is reconverted to Whole Blood volume.

Hidden Loss = Total Loss – Visible Loss.

In TKA, the mean total true blood loss was 1474ml. The mean hidden loss was 735ml. Therefore hidden loss is 50% of the total loss and the total true loss following TKA is twice the visible volume. In THA, the mean total true blood loss was 1629ml. The mean hidden loss was 343ml.

Thus hidden loss in THA is much smaller. (21%) Total loss is 1.3 times the visible loss. In the TKA group, comparing patients with large losses receiving reinfusion and those with small losses not receiving reinfusion, the proportion of total true loss which was hidden was the same, at 50%.

Patients with Body Mass Index (BMI) > 30 were compared with those with a BMI < 30 and no correlation was found between BMI and Hidden Loss.

Joint Replacement Surgery involves a ‘hidden’ blood loss which is not revealed and cannot be measured or reinfused in practice, but which should be taken into account when planning blood loss management. In TKA it is substantial. In THA it is much smaller and probably not of as much clinical concern. Hidden loss is no greater in the Obese patient.

We report a prospective case-controlled study which compared the outcome of knee replacement in seriously deformed and slightly deformed knees. There were 51 knees with varus or valgus deformity greater than 20 degrees matched for age, gender, disease, type of prosthesis and time of operation with a control group in which the alignment of the leg was within 5 degrees of normal. The clinical outcome at a mean 5.5 years was similar in the two groups. Some deformity persisted in 14 patients in the first group, 13 of whom were initially in valgus. These patients had a significantly poorer mean clinical outcome. Lateral dislocation or subluxation of the patella was found in four knees, all of which had had valgus deformity of 30 degrees or more.

We studied the mechanical properties of cartilage from the apparently unaffected compartment of knees with unicompartmental osteoarthritis (OA). Plugs of cartilage and subchondral bone, 8 mm in diameter, were obtained from the tibial plateau of seven patients treated by total knee replacement. Control specimens were obtained from eight cadaver knees of similar age. Specimens were loaded by a plane-ended indentor in a hydraulic materials testing machine; we measured thickness, 'softness', rate of creep, and compressive strength of the articular cartilage. We found that the 'unaffected' cartilage from OA knees was significantly thinner and softer than control cartilage, and it was slightly, although not significantly, weaker. We conclude that the apparently unaffected cartilage in knees with unicompartmental OA is mechanically inferior to normal cartilage, even although clinically, radiologically and morphologically it appears to be sound.

Diaphyseal fractures of the tibia in 80 patients were treated by external skeletal fixation using a unilateral frame, either in a fixed mode or in a mode which allowed the application of a small amount of predominantly axial micromovement. Patients were allocated to each regime by random selection. Fracture healing was assessed clinically, radiologically and by measurement of the mechanical stiffness of the fracture. Both clinical and mechanical healing were enhanced in the group subjected to micromovement, compared to those treated with frames in a fixed mode possessing an overall stiffness similar to that of others in common clinical use. The differences in healing time were statistically significant and independently related to the treatment method. There was no difference in complication rates between treatment groups.

We have reviewed the results of treating 75 fractures of the proximal femoral shaft in the presence of a cemented femoral prosthesis. A simple radiographic classification into four types is proposed, and suggestions are made on the appropriate management of each. Comminuted fractures around the implant need early revision, whilst spiral fractures in this region may be treated conservatively or by operation. Transverse fractures at the level of the tip of the prosthesis are difficult to manage, and may require open reduction and internal fixation.

Antibiotic levels in bone and fat were measured in patients undergoing knee replacement to determine the time that should elapse between intravenous injection and tourniquet inflation. The tissue levels increased progressively with time, and there was wide variation in absorption rate between patients and between the two cephalosporins assessed. Five minutes should probably be left between systemic injection and inflation of the tourniquet, though two minutes may be long enough for drugs which are rapidly absorbed.

This paper reports the results of bone scans on 78 painful feet. Scanning helped in the diagnosis of persistent foot pain following injury and it enabled stress fractures, fractures of the sesamoids and subtalar arthritis to be diagnosed earlier. It reliably excluded bone infection and was useful as a screening test when radiographs were normal.

We have made a retrospective comparison between the results of 49 high tibial osteotomies and 42 unicompartmental replacement arthroplasties performed for the treatment of osteoarthritis of the knee, assessed 5 to 10 years after operation. The type of operation depended on the policy of the consultant responsible for treatment but analysis of the pre-operative findings showed that the two groups were sufficiently similar for direct comparison between them. In the replacement group, 32 (76%) were good, 4 were fair, 3 were poor and 3 had been revised. In the osteotomy group 21 (43%) were good, 11 were fair, 7 were poor and 10 had been revised. It was concluded that, in this series, the results of unicompartmental replacement were significantly better and that this group had shown no sign of late deterioration.

Five elderly patients with chronic pyrophosphate arthropathy developed stress fractures of the tibia. All patients had deformed, painful knees with the result that their increasing symptoms were not readily attributed to a stress fracture. Such a possibility should be considered in patients with chronic pyrophosphate arthropathy since early recognition makes management of the stress fracture easier.

Six different conditions of non-infective bone and joint pathology have been seen amongst 67 patients with diabetic neuropathy. The characteristics of each are described. Not all the conditions require treatment but they should be differentiated from osteomyelitis. Charcot osteoarthropathy is the most common condition seen but spontaneous fractures and dislocations generally present greater therapeutic problems. The aim of treatment should be to obtain a stable foot in which there is no undue pressure on the skin from a bony prominence.

The clinical details of six patients who developed spontaneous dislocations in the foot or ankle are presented. All were shown to have diabetic neuropathy. This previously unreported condition can occur with a short history of diabetes. Some cases can be managed without operation, though arthrodesis probably offers the best chance of obtaining a stable foot of satisfactory shape.