Introduction: Correct prosthesis alignment and joint line reproduction in total knee replacement (TKR) is vital for a successful clinical outcome. It is acknowledged that the ideal coronal alignment of the knee following TKR should be between 4–10 degrees of valgus. A neutral or varus knee is associated with a higher failure rate. Previous studies have shown that ideal alignment is achieved in only around two-thirds of cases.

Joint line elevation > 8mm has been associated with inferior clinical outcome, and depression associated with retropatellar pain and increased risk of patella subluxation.

Recently, modifications have been made to the Kine-max-Plus Total Knee System instrumentation, theoretically providing better internal fixation to prevent a varus cut and a 12 mm measured resection from the “normal” tibial plateau. This study aims to examine whether these changes result in an improvement in alignment, and a more reliable restoration of joint line.

Materials and Methods: Two consecutive series, each of 75 patients who had undergone TKR using either the old (Group A) or the new (Group B) instrumentation were included in the study. Antero-posterior and lateral preoperative and postoperative knee radiographs were assessed using the American knee society radiographic analysis for prosthesis postionoing by 2 independent observers. The Tibial and Femoral Component Angles in the coronal plane (cTCA and cFCA) and in the sagittal plane (sTCA and sFCA) were measured, as was the change in joint line height.

Conclusion: Our results suggest that use of the new instrumentation is associated with better restoration of joint line, and is more effective in preventing implantation of the tibial component in varus. These figures relating to a modern instrumentation system provide a yardstick against which computer assisted and robotic surgery can be judged. Long-term follow-up will be required to assess the clinical significance of these results.

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.

Aim: To describe a radiographic biomechanical classification of tibial plateau fractures which dictates treatment. To compare the intra- and interobserver reliability and reproducibility of this, the Chertsey (C1-3) classification, and the Schatzker (SK1-6) classification.

Method: This classification system has been used at this institution for 8 years by the orthopaedic trauma consultants and consists of C1 – valgus fractures, C2 – Varus fractures and C3 axial fractures. Our treatment regime is based on this classification and results presented in a sperate study. These consultants were excluded from the study on reliability and reproducibility. 2 Orthopaedic consultants, 2 orthopaedic registrars and 2 radiologists were selected randomly to classify 30 sets of AP and Lateral radiographs, of randomly selected patients treated in this institution with tibial plateau fractures, consisting of 9 SK1-3/C1, 8 SK4/C2 and 13 SK5,6/C3 fractures, and again with the same radiographs in a random order 1 month later. Radiographs of fractures treated conservatively were excluded. Statistical analysis included Kappa concordance according to Landis and Koch, and the Mann-Whitney U test.

Results: The Schatzker system was only moderately reliable (K=0.66), and the Chertsey classification system significantly more reliable (K=0.82) (p=0.03) with regards to interobserver reliability. Excellent reproducibility (intra-observer reliability) was seen amongst all observers. The consultant orthopaedic surgeons were significantly more reliable than the radiologists, but not the orthopaedic registrars. No particular fracture type in any classification proved to be significantly more difficult to classify.

Conclusion: We present a classification used in our institution based on plain radiographs, which depicts investigations and treatment. The Chertsey classification is significantly more reliable between observers than the Schatzker classification and is reproducible.

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.

Aims: To assay the intraoperative cerebral microemboli load during primary total knee arthroplasty(TKA) using transcranial Doppler ultrasound. A battery of ten neuropsychiatric tests were carried out pre and post operatively to examine the change in cognitive outcome. The relationship between emboli load and neuropsychiatric outcome was examined.

Methods: Patients undergoing primary TKA, with no history of stroke, TIA, ongoing CNS disease or alcoholism included. Pre (baseline) and post operative (6 weeks and 6 months) neuropsychiatric tests performed. Scores were recorded as “z change” scores compared with baseline. All operations were carried out under a standardised general anaesthetic and performed by two consultant orthopaedic surgeons. Microemboli load recorded, using transcranial Doppler ultrasound (TCD), onto VHS tape for subsequent playback and analysis.

Results: 50 TKA patients were studied. Cerebral microembolisation occurred in 63% of TKA patients. Mean microembolic load for TKA patients was 3.83 (range=0–57).

There was no significant change in neuropsychiatric outcome from baseline in these patients at 6 weeks or 6 months. Those patients that experienced cerebral microembolisation did not significantly differ in neuropsychiatric outcome from those that did not.

Conclusion: Intraoperative cerebral microembolisation occurs in almost half of patients during knee arthroplasty. Emboli loads are low and do not appear to cause early or late changes in neuropsychiatric outcome.

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.

Purpose of the study: To develop a new treatment algorithm for patients with chronic anterior knee pain based on kinematic patella tracking MR imaging.

Methods and Results: Patients with anterior knee pain of more than one year duration and not responding to non-operative treatment, underwent kinematic MRI study. The provocative test was performed with the conventional MRI scanner and the patient extending the knee against resistance, the resistance provided by inflated beach ball. A retrospective analysis was done of first seventy patients, who had undergone this scanning technique.

On the imaging films, four measurements were made. They were patella subluxation, tilt, cartilage thickness and the Tibial Tubercle Trochlear distance (TTD). Patellar subluxation was classified as mild, moderate and severe. We found that a Tibial Tubercle Trochlea distance of 18mm had a specifity of 100% and a sensitivity of 89% for severe maltracking.

Conclusion: Kinematic MR Imaging is a useful investigation before considering operative treatment for patients with chronic anterior knee pain. Based on our study, we conclude that those patients with moderate lateral maltracking with a TTD< 18 mm should be offered lateral release and those with severe maltracking and TTD> 18mm should have a tibial tubercle transfer, in addition to lateral release.

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.

Purpose: To assess the outcome of customised hinged knee replacements when used to salvage catastrophically failed knee replacements in elderly patients.

Methods: Since 1993, 30 of the 280 (10.7%) revision knee replacements at the Avon Orthopaedic Centre, Bristol have used Endo customised hinged knee pros-theses (21 rotating, 9 fixed) for salvage of limb threatening situations in elderly patients. All were prospectively recorded and regularly reviewed. The average age was 75 years with a predominance of females. Surgical indications were 22 periprosthetic fractures (with or without aseptic loosening), 5 massive aseptic osteolyses, and 3 deep infections.

Results: The mean length of postoperative hospital stay was just 14.6 days and all patients were discharged walking with aids. At follow up (mean 3.0 years, range 0.5–9.3 years) 9 patients had died with their prostheses in situ and functioning. 2 had undergone amputation for recurrent sepsis and 2 had received further surgery for septic problems. 2 patients required further surgery for prosthetic disarticulation and one patient had successful on table vascular repair. 25 patients had mid or long term follow up. Their mean American Knee Scores (AKS) were 69.8 for knee and 35.6 for function (maximum 100), with a mean total knee flexion of 83 degrees. Mean Oxford knee scores (OKS) and WOMAC scores (both scored between 12 and 60 with low score indicating less difficulties) were 34.0 and 30.5 respectively.

Conclusions: Customised hinge revision knee replacements gave extremely rapid rehabilitation and hospital discharge which justified the high prosthetic cost. Complications were high but at mid and long-term review, no prostheses had failed from an aseptic cause and most of the knees of this challenging group were providing both stability and flex

Purpose of the study: To develop a new treatment algorithm for patients with chronic anterior knee pain based on kinematic patella tracking MR imaging.

Methods and Results: Patients with anterior knee pain of more than one year duration and not responding to non-operative treatment, underwent kinematic MRI study. The provocative test was performed with the conventional MRI scanner and the patient extending the knee against resistance, the resistance provided by inflated beach ball. A retrospective analysis was done of first seventy patients, who had undergone this scanning technique.

On the imaging films, four measurements were made. They were patella subluxation, tilt, cartilage thickness and the Tibial Tubercle Trochlear distance (TTD). Patellar subluxation was classified as mild, moderate and severe. We found that a Tibial Tubercle Trochlea distance of 18mm had a specifity of 100% and a sensitivity of 89% for severe maltracking.

Conclusion: Kinematic MR Imaging is a useful investigation before considering operative treatment for patients with chronic anterior knee pain. Based on our study, we conclude that those patients with moderate lateral maltracking with a TTD< 18 mm should be offered lateral release and those with severe maltracking and TTD> 18mm should have a tibial tubercle transfer, in addition to lateral release.

Following total hip arthroplasty (THA) and total knee arthroplasty (TKR) only the ‘visible’ measured blood loss is usually known. This underestimates the ‘true’ total loss, as some loss is ‘hidden’. Correct management of blood loss should take hidden loss into account.

We studied 101 THAs and 101 TKAs (with re-infusion of drained blood). Following THA, the mean total loss was 1510 ml and the hidden loss 471 ml (26%). Following TKA, the mean total loss was 1498 ml. The hidden loss was 765 ml (49%). Obesity made no difference with either operation.

THA involves a small hidden loss, the total loss being 1.3 times that measured. However, following TKA, there may be substantial hidden blood loss due to bleeding into the tissues and residual blood in the joint. The true total loss can be determined by doubling the measured loss.