Introduction: etiology of late infection after arthroplasty can be difficult to establish. Histology is the gold standard for infection in patients without inflammatory arthritis but diagnosis in inflammatory arthritis depends on culture (Atkins et al). Real-time PCR offers a rapid and direct assessment for staphylococci and enterococci infection but has not been widely assessed.

The aims of this study were

to develop the Roche lightcycler Staphylococcal and Enterococcal PCR kits to facilitate diagnosis of hip and knee prosthetic infections

Methods: uplicate, multiple tissue samples were taken (with separate sterile instruments) at the 1^st stage of revision after informed consent. One set were cultured and results interpreted by the Oxford criteria. The second set were extracted using the Qiagen DNA kit, purified (in-house method) and tested using the Roche lightcycler kits.

Results:53 patients undergoing 2 stage revision for suspected infection were recruited.15 (28.3%) had negative histology and no inflammatory arthritis; 3 with single positive cultures and negative PCR – considered contaminants.

29 patients had non-inflammatory arthritis. 14/18 (77.8%) with positive cultures had staphylococci +/or enterococci isolated and 10 PCR results correlated. The other 11 patients had negative cultures.

9 patients had inflammatory arthritis. Six were culture negative and of the other three, 2 were positive for staphylococci on culture with 1 positive by PCR.

Discussion: Negative staphylococcal PCR correlates with the isolation of staphylococci from only one sample. This agrees with the Oxford criteria that such samples may be considered contaminants. Additional positives detected by staphylococcal PCR alone are rare.

Enterococcal PCR confirmed culture positivity in 2/3 patients. An additional 5 positive PCR’s were obtained from patients’ culture negative for enterococci. It is not clear if these are false positives or more sensitive detection of enterococcal isolation.

Introduction: In this study the optimal angle of fixation or splintage for partially weight bearing fractures of the patella was determined by a gait analysis measurement system.

Subjects and Methods: A knee brace was applied to eight subjects and locked at 0, 10, 20 and 30 degrees. Measurements were also taken for an unlocked brace and in the absence of a brace. The subjects were instructed on partial weight bearing mobilisation. Three dimensional motion analyses were performed using an infrared 8-camera system. The ground reaction force was recorded by two 3-dimensional force plates embedded in the walkway. Kinematic and kinetic data was collected and the data was transferred to a computer programme for further analysis and the forces acting on the patella were calculated.

Results: The results showed that the forces acting on the patella were directly proportional to the knee flexion angle. The results also showed that the knee flexion angle does not always correspond with the angle set at the knee brace; however they did exhibit a direct relationship.

Conclusion: Our findings show that, for partially weight bearing patella fractures, the optimum form of splintage corresponds with a low knee flexion angle.

Patella and extensor mechanism injuries are common injuries and are generally managed with some degree of immobilisation and partial weight bearing to facilitate healing. The aim of this project was to determine the type of immobilisation or splintage during partial weight bearing that results in minimal forces acting through the extensor mechanism.

Gait analysis studies were performed on eight healthy male subjects mobilising partially weight bearing. Measurements were taken for six types of immobilisation: locked at 0, 10, 20, 30 degrees and unlocked in an orthotic knee brace, and without a brace. The ground reaction force, knee joint angle and the knee flexion moment were measured using Qualisys Track Manager and Visual 3D Software. The extensor mechanism moment and the extensor mechanism force were calculated using static equilibrium equations and documented data. A one-way analysis of variance statistical test was performed to determine the statistical significance of the differences between the six types of immobilisation.

There was a direct relationship between the knee flex-ion angle and the extensor mechanism force. The extensor mechanism force at 0 degrees of immobilisation was significantly lower than that for 20 and 30 degrees (p< 0.05). The increase in the extensor mechanism moment arm with increasing knee flexion was not suf-ficient to offset the increase in the extensor mechanism force caused by the increase in the knee flexion moment. The results also showed that the knee flexion angle does not always correspond with the angle set at the knee brace; however they did exhibit a direct relationship.

These results have important implications for the management of patients with patella and extensor mechanism injuries. The results suggest that improvements in knee brace design to allow 0 degrees of knee flexion, rather than the 10 degrees as seen in this study, are likely to result in significantly reduced extensor mechanism tensile forces.

To investigate the diagnostic properties of magnetic resonance imaging (MRI) scans in detecting surgically verified disruptions of the cervical intervertebral disc and anterior (ALL) and posterior longitudinal (PLL) ligaments.

Data were extracted from the reports of cervical spine MRI scans of patients who subsequently underwent surgical stabilization for presumed instability following disco-ligamentous injuries of the cervical spine. The level and severity of disc, ALL and PLL disruption was compared with surgical findings. Unweighted kappa statistics were used to assess agreement. The sensitivity, specificity, positive (PPV) and negative (NPV) predictive values were calculated after findings where dichotomised into complete rupture, yes/no. Sensitivity analyses were performed to account for missing data.

The MRI and surgical findings were compared on 31 consecutive patients. The kappa values for intervertebral disc disruption, ALL and PLL disruption were 0.22, 0.25 and 0.31 respectively, indicating fair agreement. Sensitivity, specificity, PPV and NPV are shown in Table 1. The false negative rates for diagnosing complete disruption of the disc, ALL and PLL were 0.18, 0.40 and 0.14 respectively.

The ability of cervical MRI scans to detect surgically verified disruptions of the intervertebral disc, ALL and PLL varied depending on the structure examined. In this series, the cervical MRI scan reliably detected disruption of the intervertebral disc disruption and ALL. The false negative rates are of concern and indicate the need for additional investigations to exclude instability in the absence of negative MRI findings.

Revision hip surgery is becoming increasingly common, 300 procedures being performed in 2001 at our institution. In order to achieve a good outcome bone stock needs to be of good quantity frequently necessitating the use of impaction bone grafting using allograft bone.

Donor bone may frequently take three months before it becomes available for use due to the stringent screening procedure. Donor patients must have a clean bill of health, swabs taken at the time of surgery must obviously demonstrate no growth and blood samples taken at donation and an interval of three months, free from viral infectious diseases. It is thus easy to see the lag from the time of donation to availability and why, with increasing demand, need for allograft bone is rapidly exceeding supply.

We need to look for an alternative supply of human bone allograft.

We have compared the harvest of bone at the time of primary total knee replacement with that of the femoral head by both mass and volume. Sixty consecutive patients undergoing primary hip or knee arthroplasty were included in the study, and the masses and volume of the femoral heads compared with that of the total bone cuts in knee arthroplasty. The type of knee replacement used was documented as was whether the femoral head had had a bone block removed. It was found that the mass of femoral heads was 81g, that of knee cuts 95g this is a statistically significant difference; the volume of femoral heads 66ml and that of knee cuts 75ml.

The volumes of bone available from knee arthroplasty cuts are at least comparable femoral heads obtained using hip replacement and could, perhaps, provide a realistic source of bone allograft.

Introduction: Impaction grafting has become a popular technique to revise implants. The Norwegian Arthroplasty Registry reports its use for a third of all revisions. Yet, the technique is seen as demanding. A particular challenge is to achieve sufficient mechanical stability of the construction. This work tests two hypotheses: (1) Graft compaction is an important determinant of mechanical stability, and (2) Graft compaction depends on compaction effort and graft properties. Methods: Impaction grafting surgery was simulated in laboratory experiments using artificial bones with realistic elastic properties (Sawbones, Malmö, Sweden). Bone stock was restored with compacted morsellised graft, and the joint reconstructed with a cemented implant. The implant was loaded cyclically and its migration relative to bone measured. In a second study, morsellised bone of various particle sizes and bone densities, with or without added ceramic bone substitutes, was compacted into a cylindrical mould by impaction of a plunger by a dropping weight. Plunger displacement was measured continuously. Results: Initial mechanical stability of the prostheses correlated most strongly with degree of graft compaction achieved. Graft compaction to similar strength was achieved with less energy for morsellised bone with larger particles, higher density, or bone mixed with ceramic substitutes. Conclusion: Initial mechanical stability of impaction-grafted joint reconstructions depends largely on degree of graft compaction achieved by the surgeon. Compaction depends partly on the vigour of impaction, and partly on graft quality. Higher bone density, larger particle size and mixing with ceramic particles all help to facilitate graft compaction, giving a stronger compacted mass with less effort.

Introduction: There are approximately 50000 hip and knee arthroplasties performed in the UK every year. With this increasing number the prevalence of periprosthetic fractures is also rising. These are often challenging problems with increased morbidity and mortality. The use of cortical strut allografts in periprosthetic fractures was first reported in the early 90’s with favourable results.The aim of this study was to assess the radiological outcome of cortical strut allografts used as the treatment for periprosthetic fractures of the femur in patients presenting to our institution.

Patients & Methods: 17 patients with who had received strut allografts as part of their treatment for a periprosthetic fracture of the femur were identified. 13 fractures were around a total hip replacement and 4 around other femoral implants (2 long stemmed TKR’s and 2 fracture fixation devices).

We undertook a radiological evaluation of this technique. We assessed fracture union and strut allograft incorporation using the radiological criteria of Emerson et al. The procedure was deemed a success if the fracture had united, with evidence of graft incorporation with a stable implant. We also undertook a notes review identifying any risk factors and any previous surgery.

Results: Two patients died in the early post-operative period. 15 patients were available for analysis. The average length of radiographic review was 16 months. 11/15 procedures (73%) were deemed a success. All these showed evidence of graft incorporation which was time dependent. There were four failures. In one patient the struts fractured at two months. There were three cases of deep sepsis, this required amputation in one and excision arthroplasty in two.

Conclusion: Cortical strut allografts are a good technique for the management of periprosthetic fractures of the femur. As well as providing initial support they also become incorporated which improves the host bone stock.

To document the incidence of intra-articular pathology resulting from delayed Anterior Cruciate Ligament (ACL) reconstruction

A prospective assessment of meniscal and chondral damage found at the time of primary ACL reconstruction, and the relationship of incidence of intra-articular pathology to time since original ACL injury.

We reviewed 1960 patients who had undergone a primary ACL reconstruction. There were 1443 Males and 517 females, with an average age of 28.3 years. The average age at injury was 25.4 years.

1136 patients (58%) had secondary intra-articular pathology, 621 (54.7%) had a medial meniscal tear, 594 (52.4%) had a lateral meniscal tear and 381 (33.5%) had chondral damage. The average time from injury to reconstruction was 2.9 years (34.8 months) Those with secondary intraarticular pathology presented for reconstruction later, average 3.9 years (46.8 months), compared to those without secondary pathology, average 1.5 years (18 months).

The incidence of secondary intra-articular pathology increased with delay between original ACL injury and reconstruction. 41% of those waiting 12 months; 60% of those waiting 3 years; 79% of those waiting 5 years and 88% of those waiting 10 years had secondary intra-articular pathology.

This study confirms the relationship between an unstable ACL deficient knee and the incidence of secondary intra-articular pathology. Furthermore, our study reveals the increasing incidence of meniscal and chondral pathology the greater the delay from injury to ACL reconstruction. To prevent unnecessary secondary intra-articular pathology we recommend ACL reconstruction is performed with minimal delay.

Introduction: The Motus (Osteo) total knee replacement design is an uncemented, stemless, hydroxyapatite-coated prosthesis designed as a low profile resurfacing implant.

Aim: To review the results after five to eight years of the use of this prosthesis by one surgeon and to discuss the perceived advantages of its design.

Methods: Between 1992 and 1996 the Motus (Osteo) prosthesis was used in 606 primary total knee replacements in 409 patients. The evaluation was undertaken using a clinical knee score based on the Knee Society Score and the Hospital for Special Surgery (HSS) score, which produces a maximum score of 200/200.

Results: The mean age was 69 years (range: 31 to 88 years) with 53% of the patients being female. Osteoarthritis was the underlying pathology in the majority of the cases. The minimum time to follow up was 60 months (mean: 79, range: 60 to 104 months). The mean pre-operative knee score was 98/200 with a range of movement from six degrees to 122 degrees. After five years, the mean knee score was 180/200 with a range of movement from one degree to 113 degrees. To date only two patients have required a revision procedure, both for deep infection. Twenty-six patients have died and six have been lost to follow-up as they are overseas.

Conclusion: At a minimum five-year review, the Motus (Osteo) total knee replacement prosthesis produced excellent functional and clinical results with a low rate of complications.

Preliminary costectomy before Harrington instrumentation and fusion for idiopathic scoliosis allows direct excision of the rib prominence and better correction at the second-stage operation. The excised rib fragments are used as grafts, thus avoiding the need for a separate pelvic incision. The management regime and the technique of costectomy are described. The results in 42 children, most suffering from adolescent idiopathic scoliosis and all treated by this method, have been reviewed. Respiratory function in a group of these children has been compared with that of a group treated by Harrington instrumentation alone. Costectomy produced a significantly greater reduction in total lung capacity and peak expiratory flow rate but, providing the preliminary lung function tests were reasonably normal, the cosmetic and psychological effects of costectomy were very rewarding.

A case of rotatory dislocation of both atlanto-axial joints is presented. A review of the literature reveals two other cases, both in children. This would appear to be the first report in an adult, who survived and made a full recovery.

1. This is a simple clinical study of the end-results of arthrodesis of the hip joint in patients followed up and re-examined five to twenty-five years after operation.

2. The study was stimulated by our astonishment at recent reports which suggested that arthrodesis of the hip caused serious operative mortality, a high rate of wound infection, and failure of sound fusion in one of every two cases; and that even when sound fusion was gained there was always pain in the back and usually stiffness of the knee. To say that we were astonished puts it mildly.

3. This review includes 120 patients aged from ten to seventy years, treated for osteoarthritis of the hip joint by intra-articular arthrodesis with the internal fixation of a nail, usually with an iliac graft, and with immobilisation in plaster for not less than four months.

4. Of these 120 patients there was sound fusion of the joint, proved radiographically, in 94 per cent; a mortality of nil; and recovery of free movement of the knee joint to the right angle or far beyond in 91·5 per cent. Almost half of the patients regained normal movement, the heel touching the buttock. Only in eight patients was there less than right-angled flexion.

5. There was no pain in the back—none whatever—in 64 per cent of the patients. In 36 per cent there was some pain or discomfort. One alone said that the low back pain was worse than before the operation. Many others said that pain in the back had been relieved by the operation.

6. It is emphasised that these results were gained only from sound fixation of the joint in the mid-position with neutral rotation, no more abduction than is needed to correct true shortening, and no more flexion of the joint than that with which the patient lies on the table. The limb was immobilised in plaster for at least four months after operation. The stiff knee was mobilised by the patient's own exercise without passive stretching, force or manipulation.

7. Two other groups of patients are considered. There are fourteen treated by fixation of the joint with nail alone, an operation that was never intended to arthrodese the joint and which has long since been abandoned. The other small group is that of patients with old unreduced traumatic dislocation of the hip, a procedure in which the risks of operation are so great and the number of successful results so small as to dissuade us from attempting operative reduction.

8. After successful arthrodesis of the hip joint patients can return to every household activity and every recreation including ski-ing, mountaineering, rock climbing, or whatever else they want.