Introduction An approximation of normal knee kinematics after knee replacement may improve knee function and implant fixation and reduce wear of the prosthesis. This study describes the knee joint kinematics after unicondylar knee arthroplasty (UKA) in general, and compares the Miller-Glante (MG, fixed bearing) and Oxford (mobile bearing) implants in particular.

Methods Twenty-two knees in 17 patients (11 males, six females, mean age of 69.7 yrars) were randomized into MG (11 knees) or Oxford (11 knees). No clinical complications or signs of loosening were observed. At the one year follow-up, RSA (Radiosterometry) x-rays were taken by using two x-ray tubes positioned at knee level and exposing the knee simultaneously from the side. Four pairs of weight bearing x-ray were obtained at zero degrees, 30°, 60°, 90° of knee flexion, with zero as reference position. Tibial rotation, rollback, translation of tibia-femur contact point, and the bearing movement were analyzed using UmRSA software.

Results With the MG implant, the tibia internally rotated 3.0°, 3.0°, and 4.2° respectively at 30°, 60°, and 90° of flexion, while with the Oxford implant, the tibia internally rotated 4.3°, 7.6°, and 9.5° respectively at 30°, 60°, and 90°. No significant difference was found between the two groups (P> 0.05, Repeated-measures ANOVA). The medial femoral condyle moved backward (1.8 and 1.5 mm respectively in MG and Oxford) from zero degrees to 30° of flexion. At 60°, it moved anteriorly in both knees, in MG to 0.9 mm anteriorly and in Oxford to 0.6 mm posteriorly to the reference position. At 90° the condyle moved 4.2 mm (MG) and 0.7 mm (Oxford) anteriorly to the reference position. No significant difference between the groups (P> 0.05). The femur-tibia contact point in MG moved anteriorly 2.8, 5.1, and 3.9 mm, respectively at 30°, 60°, and 90° of flexion, whereas the contact point in Oxford moved posteriorly 2.6, 1.8, 2.4 mm respectively at 30°, 60°, and 90°. A significant difference was found between the groups (P=0.003). The bearing in the Oxford implant moved backward of 2.2, 2.0, and 0.9 mm respectively at 30°, 60°, and 90° of knee flexion.

Conclusions The in-vivo weight bearing 3D knee kinematics after UKA with fixed or mobile bearing was described. In MG the medial femoral condyle moved forward with knee flexion, whereas in Oxford it moved backward together with the bearing, which is closer to normal knee kinematics.

Introduction Fibrin-sealant has been widely used clinically for the protection of haemorrhage, wounds and tissue fluid leakage. Recently fibrin-sealant has been recommended as a tissue glue for autologous chondrocyte implantation. It is known that the active compound of fibrin-sealant is thrombin but its effect on chondro-cyte is still unclear. The aims of this study are to examine if fibrin-sealant stimulates proliferation and survival of human chondrocytes.

Methods Primary human chondrocytes derived from articular cartilage were used for the detection of thrombin receptors RAR type I, II, III and IV by immunohistochemistry and RT-PCR. To examine the effect of thrombin on chondrocytes, the changes in free intra-cellular calcium were monitored after the addition of thrombin. Proliferation of chondrocytes were also tested with various concentrations of thrombin. The survival of chondrocytes was monitored by co-culturing of the cells with fibrin-sealant for up to 15 days. Primary human chondrocytes express thrombin receptor RAR types I, II, III and IV as evidenced by immunohistochemistry and RT-PCR. However, the level of expression appears to be varied between cells. This has been reflected by the measurement of intracellular calcium signal in chondrocytes.

Results Induction of intracellular calcium signals was evidenced in the majority of chondrocytes at 100 seconds after addition of thrombin. When human chondrocytes were co-cultured with thrombin at a dose between 1u/ml to 10u/ml, there was no effect on cellular proliferation at 24 hours. However, at 48 hours thrombin stimulated proliferation and survival of chondrocytes in a dose dependent manner. A maximum of three folds induction was evidenced at a dose of 10u/ml (p< 0001). Co-culture of chondrocytes with fibrin-sealant showed that after 12 hours only a few cells had migrated from the membrane to the fibrin-sealant, but after 36 hours many cells had formed a layer on the surface of fibrin-sealant. By 15 days of co-culture, it was evidenced that majority of chondrocytes were migrating into the fibrin-sealant. Immunohistology study showed that these cells express type II collagen, suggesting that they maintain the phenotype of chondrocytes.

Conclusions The results of this study show that human chondrocytes express thrombin receptor and fibrin-sealant is capable of inducing chondrocyte proliferation and maintain the survival of chondrocytes.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction There are clear theoretical advantages to support the use of bioabsorbable interference screws in the reconstruction of the anterior cruciate ligament. The purpose of this study is to determine how long it takes for an ACL screw marketed as bioabsorbable to be absorbed in the tibia.

Methods Eight patients that underwent an ACL reconstruction utilising a femoral endobutton and tibial bio-absorbable screw (Arthrex Bio-interference) made of Poly-L-Lactide (PLA) were followed up radiographically with sequential MRI scans at one, two and four years post-operatively. The scans, (Axial T1 and T2 with minimal interslice gap) were assessed by two independent consultant radiologists.

Results There was no evidence radiologically of progression to absorption of the tibial screw on any scan. The MRI appearance remained unchanged from one to four years with the exception of the presence of a small cyst in the tunnel of one of the patients.

Conclusions Despite claims by manufacturers of rapid rates of bio-absorption of their products, this study questions the accuracy of such statements not tested in-vivo. Our study clearly shows the continued presence of such a bioabsorbable screw at four years post-operatively.

Introduction Wear particle induced osteolysis is regarded as the main reason for aseptic loosening of hip replacements. Crosslinked polyethylene show extremely low wear in lab studies and is routinely used today, though with very little clinical testing. We report wear, migration and function for uncemented cups with a crosslinked poly.

Methods Twelve hips in 12 patients with mean age of 70 years were operated with uncemented cups (Reflection), cemented stems and metal heads. Five Mrad cross linked liners annealed below melt temperature were used in all hips (XLPE, Smith & Nephew). Tantalum markers were inserted in liners and acetabular bone for RSA measurements and migration and wear measured over two years. The result was compared to matched controls from a study of 80 cups with the same implant and non cross linked poly, operated by the same surgeon. X-rays, WOMAC and Sf-36 were performed pre-operatively and at two years.

Results The mean proximal head penetration at two months was 0.09 mm. This was thought to be mainly due to the creep of the polyethylene and was equal to “normal” poly. At the one year follow-up the mean proximal wear had increased with 0.02 mm and at two years 0.03 mm. This compares with the 0.33 mm recorded for the old poly (p=0.001, Mann Whitney U test.). The cups migrated 0.2 mm proximally and showed a normal migration profile, comparable to the cups with non cross-linked poly. The accuracy of measuring proximal wear, in this study, was found to be 0.07 mm (95% CI). No differences in radiolucent lines or clinical scores were found.

Conclusions The first two years proximal wear was 0.03 mm compared to the 0.33 mm found for non crosslinked poly. This is a reduction with 90% which certainly looks promising.

Successful reconstructive surgery with allografts is severely limited by a failure rate of 30 – 40%. Allograft failure is due to nonunion of the graft-host junction. The molecular mechanism by which this occurs is not yet fully elucidated. Using a sheep femoral allograft model, we have investigated the cellular and molecular mechanisms associated with nonunion of bone allografts. Five, from a total of twelve operations, resulted in the development of graft-host nonunion, reflecting a failure rate of 42%. Histological assessment revealed that allograft failure was due to the excessive accumulation of and resorption by, osteoclasts (Ocs) on the surface of the bone allograft. Three distinct layers, lying adjacent to the allograft bone surface, in the nonunion groups, were identified. The outer fibroblastic layer contained abundant fibroblasts and connective tissue. Underlying this layer were synovial-like cells and some multinuclear giant cells. The third layer, opposing the bone surface, consisted of Ocs and round mononuclear cells. Histomorphometric analysis showed that allograft unions, featured a large amount of newly formed bone on the surface, (OS/BS = 47.81%) with a small proportion of eroded surface (ES/BS = 20.59%). The number of osteoclasts associated with the allograft bone surface were few (Oc/B.Pm = 1.7190/mm) and activity (ES/BS = 46.68%) of Ocs with a reduced amount of new bone formation (OS = 6.35%). Both calcitonin receptor and H+ATPase mRNA, characteristically expressed by Ocs, were localised to the multinuclear giant cells, indicating that they were Ocs. Synovial-like cells in the histological layer above the Ocs, expressed gene transcript for the Osteoprotegrin Ligand (OPGL), a membrane bound factor that is critical for the induction of Oc activity and osteoclastogenesis. In conclusion, these findings suggest that failure of bone allografts is partially due to excessive resorption by host Ocs, accompanied by reduced bone formation. The production of OPGL by synovial-like cells, may be responsible for the recruitment and generation of Ocs.

Introduction: Transmission of infection is always a concern in allograft bone banking and the surgical applications of such bone.

Aim: To review the microbiological results of the femoral head donor program at Perth Bone and Tissue Bank from March 1992 until April 2001.

Methods: There were 4515 femoral head donations. All were cultured by means of a swab and bone chip at time of retrieval, prior to storage at −75 degrees C. Once six month repeat serological testing of donors had been obtained, the heads were processed under sterile conditions. All soft tissues were removed, the bone was milled and washed with 1.5 litres warm saline as pulsed lavage. A microbiological swab was taken prior to packaging the graft ready for irradiation and freezer storage until use.

Results: Five hundred and seventy-nine femoral heads had a positive swab or chip at retrieval, with 31 cases having the same organism on both tests. In 516 cases only one of these tests was positive, with skin organisms being the dominant finding. In 10 cases the swab at the end of processing was positive on culture. Eight of these cases were negative on retrieval testing, and in only one case was the same organism, a coagulase negative staphylococcus, present on the processing swab and retrieval testing.

Conclusions: This work suggested that microbiological culture of femoral head swabs and bone chips at time of retrieval has little effect on the culture at the end of processing. After storage at −75 degrees C, mechanical cleaning and washing, less than 1% of femoral heads were positive prior to irradiation.

A paper was presented two years ago reviewing evidence of absorption of the Bio Interference screw and tunnel widening at three, six and 12 months following anterior cruciate ligament reconstruction using double-stranded hamstrings. The femoral fixation was with an Endobutton with a double loop of Mercylene tape with a Bio Interference screw and an extra small staple for the distal fixation. This paper presents further magnet resonance imaging (MRI) studies at least two years after surgery on 10 of those patients to assess if there was any MRI evidence of absorption of the Bio Interference screw or tunnel widening (in particular ganglion formation) in the femoral or tibial tunnels.

The results showed that at least two years after surgery there was little evidence of Bio Interference screw absorption. There was no evidence of tunnel widening.

Articular cartilage defects of the knee occur commonly in sports injuries and trauma. Increasing evidence suggests that the only technique that enables the regeneration of articular hyaline cartilage in chondral defects is autologous chondrocyte implantation (ACI). Here we have reported our clinical experience of autologous chondrocyte implantation using biodegradable type I/III collagen membrane (CACI). A total of 26 patients (age range from 19 to 60 years, average 37 years) was conducted with CACI. Pre-operative magnetic resonance imaging (MRI) scans were performed on all patients. Post-operative MRI scans were planned for approximately three and 12 months after the surgery to determine the success of integration of implanted chondrocytes.

The results demonstrated that the initial post-operative MRI scans at three months showed the presence of oedematous tissue at the defect sites in 23 patients, contrasting with the fluid filled defects seen preoperatively and with and MRI signal differing from that of the surrounding normal hyaline articular cartilage. MRI scans in nine patients at 12 months after their operations showed maturation of cartilage graft in all patients. Apopototic testing of the chondrocytes using Annexin IV before implantation showed that the viability of the chondrocytes was over 85% where the apopototic rate of chondrocytes was less than 2%. One patient with an apopototic rate of over 10% has a delayed repair in cartilage defects as shown by MRI.

In conclusion, early phase clinical studies showed that autologous chondrocyte implantation remains promising for the treatment of chondral defects with restoration of hyaline cartilage. Longer clinical follow-up of the patients and better assessment of cellular phenotype of chondrocytes before implantation are required.

We report a prospective study of the influence of various factors on the six-month mortality of 531 patients with subcapital hip fractures. We performed univariate and multivariate analyses on the 403 patients treated surgically. The most significant predictors of the six-month mortality were dementia, postoperative chest infection, malignant neoplasia, old age and deep-wound infection, in that order. A simple test of mental ability was the most significant prognostic indicator and this test should be included in future studies of the management of hip fractures in the elderly.

The early results of revision osteoarticular allografts in weight-bearing joints are reported. Sixteen consecutive patients underwent surgery over a six-year period between 1982 and 1988. At the time of review eight patients (50%) had surviving second allografts with an average follow-up time of 48 months (range 12 to 87). Five patients were graded excellent according to the Mankin scale, one good and two fair. Eight patients (50%) required further surgery, but only two patients came to amputation.