Introduction

Pre-operative urine screening is accepted practice during pre-operative assessment in elective orthopaedic practice. There is no evidence surrounding the benefits, effects or clinical outcomes of such a practice.

Introduction: The survival of massive endoprosthesis replacements is not as successful as conventional joint replacements. The main cause of failure of these implants is aseptic loosening. Bone in-growth onto the implant collar on the shaft of the prosthesis adjacent to the transaction site has been correlated with a decrease in radiolucent lines adjacent to the intramedullary stem and reduced implant loosening. We propose that bone contact and in-growth to the collar may be further enhanced with tissue engineering techniques. The hypothesis of this study was that autologous mesenchymal stem cells (MSCs) suspended within fibrin glue and sprayed onto hydroxyapatite (HA)-coated collars of massive prosthesis will augment bone growth and contact to the implant in an ovine model.

Materials and Methods: MSCs were isolated and expanded in vitro from the iliac crest of six adult sheep. Pre-implantation, 2 x 106 autologous MSCS were suspended in thrombin. During surgery, this mixture was combined with fibrinogen and sprayed onto the proximal and distal HA-coated collars of tibial midshaft prostheses using pressurized air. The implants were cemented into the right hind limb of twelve sheep, six of which received MSCs. Radiographs were taken at 2, 4 and 6 months and bone area within defined regions quantified using image analysis software. After six months, specimens were retrieved and processed for undecalcified histology. Transverse thin sections were prepared through the centre of each collar. Image analysis was used to quantify bone area and contact. Mann Whitney U tests were used for comparative statistical analysis, where p< 0.05 was classified as significant.

Results: Anterior-posterior (AP) radiographs taken at 2, 4, and 6 months showed that animals treated with MSCs produced more bone adjacent to the shaft of the implant. Analysis of bone area on both AP and medio-lateral (ML) radiographs taken after sacrifice showed that stem cell-treated implants encouraged significantly more total bone around the implants at 6 months than the control group (171.94 ± 29.04 mm2, and 87.51 ± 9.81 mm2 bone area, respectively, p = 0.016). Analysis of histological sections shows a significant increase in bone area around midshafts treated with MSCs, compared to the implant controls (53.99 ± 10.64 mm2, and 21.07 ± 7.34 mm2, respectively; p = 0.020). The average surface area contact between the midshaft and bone was almost doubled in the MSC-implant group (19.83 ± 8.73 % contact) than in the control group (8.667 ± 8.667 %, p = 0.196). In the MSC group bone was seen deep within the grooves of the HA coated collar whilst a fibrous soft tissue layer separated the newly formed bone in the control group.

Conclusion: Bone contact and in-growth to massive endoprostheses was significantly improved by spraying the implant with autologous MSCs suspended in fibrin glue. Enhanced fixation using stem cells may help prevent aseptic loosening in these massive implants.

Compression testing of cadaver specimens showed that excision of the radial head allowed proximal radial displacement. The insertion of a metallic radial head restored normal mechanics, while a silicone rubber implant did not. We reviewed 31 of 36 comminuted fractures of the radial head, 21 associated with dislocation or ulnar fracture, which had been treated by primary replacement with a Vitallium prosthesis. At a mean follow-up of 4.5 years, there was reliable restoration of stability and prevention of proximal radial migration. There had been no dislocations or prosthetic failures, but two implants had been removed for loosening. The prosthesis is recommended for use as a spacer to stabilise the elbow after severe injuries while the soft tissues heal.

The anterior cruciate ligament was replaced in rabbits, using implants of carbon or polyester filaments with known mechanical properties. The biocompatibility of the implants was assessed in detail using light microscopy, and scanning and transmission electron microscopy. Mechanical tests were made of stability, in comparison with normal joints and controls after excision of the ligament. Some carbon fibre implants broke down in vivo, allowing instability; the fragments caused chronic inflammation. Intact carbon implants did not induce the formation of neoligaments; they were covered by tissue, but there was no ingrowth. Polyester did not degrade mechanically and supported early collagenous ingrowth within the implant, even in the mid-joint space. It was concluded that there was no justification for the use of carbon fibres as anterior cruciate replacements; polyester appeared to be suitable.

The calcaneal tendons of rabbits were excised and either replaced with a carbon or polyester fibre implant, or left as controls. The strength of the neotendons and their mode of failure under tension were examined at intervals up to six months after operation. Return to near normal strength took six months to develop, suggesting that patients having ligament or tendon reconstructions should not resume normal activity for several months. Carbon fibre-based neotendons showed progressive elongation which, unless avoided by a sufficient period of immobilisation, would affect the functional result.

Carbon-fibre and polyester-fibre implants of comparable dimensions were used to replace the calcaneal tendon in 30 sheep. The neotendon produced in proximity to the polyester fibres was denser, more collagenous and more closely adherent than that in the carbon-based neotendon. Fragmentation of the carbon caused continuing cellular reaction which was associated with a poor collagen response.

The effects of synovectomy and excision of the radial head in 40 elbows affected by rheumatoid arthritis have been assessed. In contrast with many reports indicating minimal side-effects of this procedure, a common pattern of deterioration from what was often a satisfactory initial result has been demonstrated. A biomechanical theory of one of the factors responsible for failure has been put forward and the importance of conserving or replacing the radial head emphasised.

Eighteen patients with marginal depressed or comminuted fractures of the head of the radius, nine of whom had an associated posterior dislocation of the elbow, had a Silastic replacement carried out shortly after injury. After an average follow-up of twenty-six months satisfactory clinical results were observed in seventeen cases; three prostheses broke. The prosthesis has been particularly effective in the group with an associated posterior dislocation of the elbow.