Introduction: Current treatment options for small, contained articular cartilage defects include microfracture, osteochondral autograft plugs or newer synthetic plugs. Chondromimetic is a novel biphasic biological scaffold composed of collagen and glycosaminoglycan. The addition of brushite provides the scaffold with a regionally specific component mimicking both phases of the osteochondral unit. The aim of this study was to show the efficacy of Chondromimetic in repairing a surgically created osteochondral defect in a caprine model.

Methods: Osteochondral defects were made in the lateral trochlear sulcus (LTS) and medial femoral condyle (MFC) of nine goats. Chondromimetic scaffolds (6x6mm) were inserted into each defect (n=6), while three controls had defects left empty (n=3). All animals were sacrificed at 26 weeks postoperatively. Macroscopic evaluations and quantitative stiffness properties were assessed. Histological sections were taken at approximately the centre of the defect, stained with Safrinin O/Fast Green and scored using a validated quantitative assessment tool.

Results: Macroscopically, the repair tissue scored higher in the MFC and LTS (p< 0.05) compared to controls. In all defects, the mechanical stiffness was found to be within one standard deviation of native cartilage, except that of the LTS controls. Histologically, the predominant tissue in the cartilage layer was deemed to be hyaline-like in three of six MFC defects, and five of six LTS defects according to the modified Sellers score. This was compared to one in three and zero of three in the MFC and LTS controls respectively.

Discussion: These results represent the early findings from an ongoing in-vivo study in which a further group of animals will be sacrificed at one year. At six months, the histology and mechanical properties are encouraging and should continue to improve with time. These results show that Chondromimetic may represent an acceptable alternative to marrow stimulation in the treatment of osteochondral defects.

Introduction: Platelet rich plasma (PRP) has been hypothesised to be of potential benefit to articular cartilage tissue engineering, through its release of autologous growth factors. The aim of this study was to ascertain whether the addition of thrombin is required to achieve platelet activation and sustained growth factor release in-vitro, when PRP is applied to a collagen based osteochondral scaffold.

Methods: Collagen/glycosaminoglycan scaffolds were fashioned, to which equal combined volumes of test substances were added (n=3): 500μl PRP; 375μl PRP + 125μl autologous thrombin (3:1); 455μl PRP + 45μl bovine thrombin (10:1). One ml of DMEM/F12 medium was added to each scaffold and changed completely at 12/24 hours, and 3/10 days, following which release of TGF-β1, PDGF-AB and bFGF were measured using ELISA. Secondly, equal sized collagen/glycosaminogly-can and polylactide co-glycolide scaffolds were fashioned to which 500μl of PRP were added (n=3). Similar conditions were followed as previously except that only PDGF-AB was assayed.

Results: A similar cumulative release profile of all growth factors was found over the 10 day period. An increase in growth factor release was seen in the PRP only group at all time points with PDGF-AB in particular reaching statistical significance at all time points (p< 0.006). These findings remained apparent when a correction for volume was made (p< 0.028) suggesting a particular role of the collagen in platelet activation. This was shown in the second experiment, in which a significantly increased cumulative volume of PDGF-AB was released from the collagen/glycosaminoglycan scaffold without thrombin activation (p< 0.04).

Discussion: This study shows that collagen is a potent activator of platelets, requiring no further additive to achieve satisfactory growth factor release when applied clinically. These results suggest that if PRP is combined with polymer scaffolds, it should be activated with thrombin to achieve optimum growth factor release.

Introduction: Current treatment options for small, contained articular cartilage defects include microfracture, osteochondral autograft plugs or newer synthetic plugs. Chondromimetic is a novel biphasic biological scaffold composed of collagen and glycosaminoglycan. The addition of brushite provides the scaffold with a regionally specific component enabling the scaffold to mimic both phases of the osteochondral unit.

The aim of this study was to show the efficacy of Chondromimetic in repairing a surgically created osteochondral defect in a caprine model.

Methods: Osteochondral defects were made in the lateral trochlear sulcus (LTS) and medial femoral condyle (MFC) of nine goats. Chondromimetic scaffolds (6x6mm) were inserted into each defect (n=6), while three controls had defects left empty (n=3). All animals were sacrificed at 26 weeks postoperatively. Macroscopic evaluations and quantitative stiffness properties were assessed. Histological sections were taken at approximately the centre of the defect, stained with Safrinin O/Fast Green and scored using a validated quantitative assessment tool.

Results: Macroscopically, the repair tissue scored higher in the filled MFC and LTS (p< 0.05) compared to controls. In all defects, the mechanical stiffness was found to be within one standard deviation of native cartilage, except the LTS controls. Histologically, the predominant tissue in the cartilage layer was hyaline-like in three of six filled MFC defects, and five of six filled LTS defects according to the modified Sellers score. This was compared to one in three and zero of three in the MFC and LTS controls respectively.

Discussion: These results represent the early findings from an ongoing in-vivo study in which a further group of animals will be sacrificed at one year. At six months, the histology and mechanical properties are encouraging and should continue to improve with time. These results show that Chondromimetic may represent an acceptable alternative to marrow stimulation in the treatment of osteochondral defects.

Introduction: Platelet rich plasma (PRP) has been hypothesised to be of potential benefit to articular cartilage tissue engineering, through its release of autologous growth factors.

The aim of this study was to ascertain whether the addition of thrombin is required to achieve platelet activation and sustained growth factor release in-vitro, when PRP is applied to a collagen based osteochondral scaffold.

Methods: Collagen/glycosaminoglycan scaffolds were fashioned, to which equal combined volumes of test substances were added (n=3): 500μl PRP; 375μl PRP + 125μl autologous thrombin (3:1); 455μl PRP + 45μl bovine thrombin (10:1). One ml of DMEM/F12 medium was added to each scaffold and changed completely at 12/24 hours, and 3/10 days, following which release of TGF-β1, PDGF-AB and bFGF were measured using ELISA. Secondly, equal sized collagen/glycosaminogly-can and polylactide co-glycolide scaffolds were fashioned to which 500μl of PRP were added (n=3). Similar conditions were followed as previously except that only PDGF-AB was assayed.

Results: A similar cumulative release profile of all growth factors was found over the 10 day period. Greater growth factor release was seen in the PRP only group at all time points with PDGF-AB in particular reaching statistical significance at all time points (p< 0.006). These findings remained apparent when a correction for volume was made (p< 0.028) suggesting a particular role of the collagen in platelet activation. This was shown in the second experiment, in which a significantly increased cumulative volume of PDGF-AB was released from the collagen/glycosaminoglycan scaffold without thrombin activation (p< 0.04).

Discussion: This study shows that collagen is a potent activator of platelets, requiring no further addition to achieve satisfactory growth factor release when applied clinically. These results suggest that if PRP is combined with polylactide co-glycolide scaffolds, it should be activated with thrombin to achieve optimum growth factor release.

The influence of the timing of surgery for closed ankle fractures on complications is unclear. Previous studies have failed to demonstrate any associations with clear statistical support. This is a retrospective review of 221 patients presenting with closed ankle fractures treated with open reduction and internal fixation. The patients were similar in respect to age, gender, fracture type, surgeon grade, American Society of Anaesthesiologists grade, grade of anaesthetist and tourniquet time. Power analysis was performed for sample size. Patients were followed up until fracture union. The mean duration of inpatient care was greater in the delayed group (p = 0.0002). There was an increased rate of local (p = 0.0451) and total complications (p = 0.0116) if surgery was delayed more than 24 hours. This observational study demonstrates that for the management of closed ankle fractures there is an adverse clinical outcome in patients who undergo delayed operative intervention.

Articular cartilage repair remains a challenge to surgeons and basic scientists. The field of tissue engineering allows the simultaneous use of material scaffolds, cells and signalling molecules to attempt to modulate the regenerative tissue. This review summarises the research that has been undertaken to date using this approach, with a particular emphasis on those techniques that have been introduced into clinical practice, via in vitro and preclinical studies.

Carbonate-substituted hydroxyapatite (CHA) is more osteoconductive and more resorbable than hydroxyapatite (HA), but the underlying mode of its action is unclear. We hypothesised that increased resorption of the ceramic by osteoclasts might subsequently upregulate osteoblasts by a coupling mechanism, and sought to test this in a large animal model.

Defects were created in both the lateral femoral condyles of 12 adult sheep. Six were implanted with CHA granules bilaterally, and six with HA. Six of the animals in each group received the bisphosphonate zoledronate (0.05 mg/kg), which inhibits the function of osteoclasts, intra-operatively.

After six weeks bony ingrowth was greater in the CHA implants than in HA, but not in the animals given zoledronate. Functional osteoclasts are necessary for the enhanced osteoconduction seen in CHA compared with HA.

There has been renewed interest in metal-on-metal bearings as hip resurfacing components for treatment in young, active patients. This study examines the effects of fixation (cemented or uncemented heads) and bone-implant interface conditions (stem-bone and head-bone) on the biomechanics of the Birmingham hip resurfacing (BHR) arthroplasty, using high resolution, 3-d computational models of the bilateral pelvis from a 45-year-old donor. Femoral bone stress and strain in the natural and BHR hips were compared. Bone remodelling stimuli were also determined for the BHR hips using changes in strain energy. Proximal femoral bone stress and strain were non-physiological when the BHR femoral component was fixed to bone. The reduction of strain energy within the femoral head was of sufficient magnitude to invoke early bone resorption. Less reduction of stress was demonstrated when the BHR femoral component was completely debonded from bone. Bone apposition around the distal stem was predicted based on the stress and strain transfer through the stem. Femoral stress or strain patterns were not affected by the type of fixation medium used (cemented vs. Uncemented). Analysis of proximal stress and strain shielding in the BHR arthroplasty provides a plausible mechanism for overall structural weakening due to loss of bony support. It is postulated that the proximal bone resorption and distal bone formation may progress to neck thinning as increasing stress and strain transfer occurs through the stem. This may be further exacerbated by additional proximal bone loss through avascular necrosis. Medium term retrieval specimens have shown bone remodelling that is consistent with our results. It is unclear if the clinical consequences of neck thinning will become more evident in longer-term follow-ups of the BHR.

One potential limitation with uncemented, hemispherical metal-backed acetabular components is stress shielding of bony structures due to the mismatch in elastic modulus between the metal backing and the peri-prosthetic bone. A proposed substitute is a horseshoe-shaped acetabular component, which replicates the bony anatomy. One such device, the Cambridge cup, has shown successful clinical and radiological outcomes at five years follow-up (Brooks 2004, Field 2005). We conducted a study of the Cambridge cup from a biomechanical perspective, using validated, high-resolution computational models of the bilateral hip. Peri-prosthetic stress and strain fields associated with the Cambridge cup were compared to those for the natural hip and a reconstructed hip with a conventional metal-backed hemispherical cup during peak gait loading. We found that the hemispherical cup caused an unphysiologic distribution of bone stresses in the superior roof and unphysiologic strain transfer around the acetabular fossa. These stress distributions are consistent with bone remodelling. In contrast, the peri-acetabular stresses and strains produced by the Cambridge cup differed from the natural hip but were more physiologic than the conventional hemispherical design. With the Cambridge cup, stresses in the superior acetabular roof, directly underneath the central bearing region, were greater than with the conventional design. Despite the thin bearing, the peak liner stresses in the Cambridge cup (max. tensile stress: 1.2 MPa; yield stress: 4.5 MPa) were much lower than the reported material strengths. Fossa loading by the hemispherical cup has been suggested as a possible mechanism for decreased implant stability (Widmer 2002). Conversely, the Cambridge cup produced semi-lunar peri-prosthetic stress fields, consistent with contact regions measured in natural hips (Widmer 2002). These analyses provide a better understanding of the biomechanics of the reconstructed acetabulum and suggest that a change in component geometry may promote long-term fixation in the pelvis.

Background: To analyse the effectiveness and complications of Less Invasive Stabilisation System (LISS plate) in the management of peri-prosthetic femoral fractures.

Materials and methods: We present a study of 18 peri-prosthetic femoral fractures around hip arthroplasty (16 females and 2 male patients) treated with LISS plate between September 2001 to February 2005. The average age of the patients was 81.6 years. Twelve patients had significant co-morbidities pre-operatively. All the fractures were classified according to the Vancouver classification for Peri-prosthetic fracture of femur. Ten were classified as type B1, two as type B2 and six as type C. Eleven fractures were around total hip replacement and seven were around hemi-arthroplasty (four cemented and 3 uncemented). Partial weight bearing started early post-operatively. Full weight bearing varied between 5-6 weeks depending on clinical and radiological status. The patients were followed up untill fracture union.

Results: Three patients died during the follow-up period owing to unrelated causes. The average follow up period was 11.7 months. All the remaining fifteen patients had satisfactory fracture union although one patient required further LISS plate following a fall 17 days postoperatively and another one patient developed low grade deep infection with a chronic sinus. It was noted that in one patient, plate had lifted off the bone at the proximal end with no loss of reduction of the fracture. Three patients were noted to have mild to moderate discomfort around the prominent implant. No implant breakage noted.

Conclusions: Even though LISS plate was originally designed for distal femoral fracture treatment, it appears to be very promising device in the treatment of peri-prosthetic femoral fractures (Type B1, Type C and medically unfit patients with Type B2 for stem- revision) with osteoporotic bone in elderly patients. Early mobilization is a key feature. This system involves minimally invasive approach, stable construct without need for primary bone grafting.

Prior studies have compared the bacterial load observed in laminar flow operating theatres (LFOTs) and standard operating theatres (STOTs) by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the poly-merase chain reaction (PCR). This study assessed the wound contamination rate during THRs and compared the results in STOT with that in LFOTs using PCR.

We recruited patients undergoing primary THR for osteoarthritis. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date.

In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture. Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs, of which 3 were taken at the start of surgery and 9 at the end of the surgery, giving a 45% wound contamination rate (9 of 20). Two specimens (5%), both taken at the end of surgery, were positive on enriched culture. In LFOTs, bacterial DNA was identified by PCR on 8 of 40 specimens (20%), of which 2 were taken at the start of surgery and 6 at the end of surgery, giving a 30% wound contamination rate (6 of 20). No specimens were positive on enriched culture.

Wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data remind us the importance of aseptic surgical technique as significant wound contamination can occur despite the use of ultra clean air operating theatres.

Introduction: The Cambridge Acetabular cup is a unique, uncemented prosthesis that has been designed to transmit load to the supporting bone using a flexible material, carbon fibre reinforced polybutyleneterephthalate (CFRPBT). This should significantly reduce bone loss and provide long term stability. The cup consists of a ultra high molecular weight polyethylene liner within a carbon fibre composite backing that was tested with either a plasma sprayed HA coating or with the coating removed. The cup is a horseshoe shaped insert of similar thickness to the cartilage layer and transmits force only to the regions of the acetabulum originally covered with cartilage. The purpose of this study was to evaluate the response of bone and surrounding tissues to the presence of the cup in retrieved human specimens.

Methods: We examined 12 cementless Cambridge acetabular implants that were retrieved at autopsy between 2 and 84 months following surgery. Nine of the implants were coated with HA and three were uncoated. The implant and the surrounding bone were fixed, dehydrated and embedded in polymethylmethacrylate. Sections were cut parallel to the opening of the cup and in two different planes diagonally through the cup. The sections were surface stained with toluidine blue and examined by light microscopy. Image analysis was used to measure the percentage of bone apposition to the implant, the area of bone and fibrous tissue around the implant and the thickness of hydroxyapatite coating.

Results: All 9 HA coated implants showed good bone contact with a mean bone apposition and standard deviation of 50.9% +/− 17.5%. The thickness of the HA coating decreased with time and where this was occurring bone remodelling was seen adjacent to the HA surface. However, even in specimens where the HA coating had been removed completely good bone apposition to the CFRPBT remained. Bone marrow was seen apposed to the implant surface where HA and bone had both been resorbed with little or no fibrous tissue. The uncoated implants showed significantly less bone apposition than the HA coated specimens, mean 11.4% +/− 9.9%(p < 0.01) and significant amounts of fibrous tissue at the interface.

Discussion: The results of this study indicate that the anatomic design of the Cambridge Cup with a flexible CFRPBT backing and HA coating encourages good bone apposition. In the absence of HA the results are generally poor with less bone apposition and often a fibrous membrane at the implant surface. There was a decrease in HA thickness with time in situ and cell mediated bone remodelling seems to be the most likely explanation of the HA loss. However, good bone apposition was seen to the CFRPBT surface even after complete HA resorption in contrast to the uncoated specimens. Though the mean bone apposition percentage to the HA coated implants declined with time, the bone was replaced by marrow apposed to the implant surface. This is in contrast to the uncoated implants where fibrous tissue becomes apposed to the implant surface. We believe this is due to micro-motion occurring at the bone implant interface. The HA coating appears necessary to provide good initial bone bonding to the implant surface that is maintained even after complete loss of HA.

Introduction; In contrast to hydroxyapatite (HA), carbonate substituted hydroxyapatite (CHA) is resorbed by osteoclasts, and is more osteoconductive in vivo. On bone, osteoclastic resorption results not only in topographical changes, but also changes in the proteinaceous matrix within the resorption pit to which osteoblasts respond [1]. This study sought to investigate a possible link between the different bioresorptive properties of these biomaterials and subsequent bone formation on their surfaces, analogous to the coupling seen in normal bone remodelling.

Methods; Phase-pure HA and 2.7wt% CHA were prepared by aqueous precipitation methods [2] and processed into dense sintered discs for cell culture. Human osteoclasts derived from CD14+ precursors were cultured for 21 days on discs of HA and CHA; subsequently, cells and the proteinaceous layer were removed from some discs leaving a topographically altered surface (assessed by SEM and profilometry), whilst in others the proteinaceous layer was left intact. Control (unresorbed) discs were also prepared. The discs were then seeded with human osteoblasts (HOBs) which were cultured for up to 28 days, in some cases in the presence of hydrocortisone and â-glycerophosphate. Proliferation (MTS assay), collagen synthesis (3-H Proline incorporation), and the formation of mineralised nodules (tetra-cycline labelling [3] and SEM) were assessed.

Results; Osteoclasts altered the ceramic surfaces. Large pits were seen on CHA in contrast to limited erosion of the HA surface, accompanied by a greater increase surface roughness (Ra) (p< 0.05). After 6 days of culture, proliferation of HOBs was increased on resorbed discs provided the proteinaceous layer resulting from osteoclastic activity was left intact. At 28 days, cells had formed confluent sheets and there were no significant differences in their number. At 6 days, collagen synthesis by HOBs on CHA was increased on resorbed surfaces, and further increased if the proteinaceous layer was left intact. A similar response was seen on HA, but not until 28 days. Mineralised nodules formed after 28 days of culture in the presence of hydrocortisone and â-glycerophosphate on tissue culture plastic, but not in their absence. By contrast on the ceramics there was no evidence of mineralised nodule formation on any of the discs, although globular accretions were present in small amounts throughout the collagenous matrix regardless of the presence or absence of supplements.

Conclusion; Prior osteoclastic activity on HA and CHA affects subsequent proliferation and collagen production by HOBs. The effects of topographical alteration and matrix conditioning appear synergistic, and are apparent at an earlier time-point on a more resorbable ceramic. Osteoclastic activity may be important in the osteoconductive properties of biomaterials.

The effects of the method of fixation and interface conditions on the biomechanics of the femoral component of the Birmingham hip resurfacing arthroplasty were examined using a highly detailed three-dimensional computer model of the hip. Stresses and strains in the proximal femur were compared for the natural femur and for the femur resurfaced with the Birmingham hip resurfacing. A comparison of cemented versus uncemented fixation showed no advantage of either with regard to bone loading. When the Birmingham hip resurfacing femoral component was fixed to bone, proximal femoral stresses and strains were non-physiological. Bone resorption was predicted in the inferomedial and superolateral bone within the Birmingham hip resurfacing shell. Resorption was limited to the superolateral region when the stem was not fixed. The increased bone strain observed adjacent to the distal stem should stimulate an increase in bone density at that location. The remodelling of bone seen during revision of failed Birmingham hip resurfacing implants appears to be consistent with the predictions of our finite element analysis.

The Cambridge Cup has been designed to replace the horseshoe-shaped articular cartilage of the acetabulum and the underlying subchondral bone. It is intended to provide physiological loading with minimal resection of healthy bone.

The cup has been used in 50 women with displaced, subcapital fractures of the neck of the femur. In 24 cases, the cup was coated with hydroxyapatite. In 26, the coating was removed before implantation in order to simulate the effect of long-term resorption.

The mean Barthel index and the Charnley-modified Merle d’Aubigné scores recovered to their levels before fracture. We reviewed 30 women at two years, 21 were asymptomatic and nine reported minimal pain. The mean scores deteriorated slightly after five years reflecting the comorbidity of advancing age. Patients with the hydroxyapatite-coated components remained asymptomatic, with no wear or loosening. The uncoated components migrated after four years and three required revision. This trial shows good early results using a novel, hydroxyapatite-coated, physiological acetabular component.

Introduction: In the 1970’s, ‘viscosupplementation’ with hyaluronan was proposed as a potential treatment for OA with the idea that it would improve joint lubrication. However, despite studies showing its ability to reduce pain, the fact that the resident time within a joint (48 hours) is much less than its clinical effect (several months) along with pharmacological effects on chondroctyes and synoviocytes has confirmed that injected hyaluronan acts as a pharmaceutical rather than as a lubricant as originally thought. In this regard, the effects of inert synthetic lubricants on arthritic joints have not previously been adequately investigated.

This study examines the effect of injecting an inert synthetic lubricant, perfluoroalkylether (PFAE16350), as a mechanical joint lubricant to prevent the development of osteoarthritis in a surgically induced model of osteoarthritis in the adult guinea pig.

Materials & Methods: Osteoarthritic changes were initiated in the hind knee joint of 12 adult male Dunkin-Hartley guinea-pigs by excision of the medial meniscus and anterior cruciate ligament.

After wound closure, the animals were randomly assigned to 1 of 2 groups: (1) Single intra-articular injection of 1ml synthetic, sterile lubricant (PFAE16350) or (2) Control group with single intra-articular injection of 1ml 0.9% sterile saline.

At 9 weeks after surgery, after sacrifice, knee arthrotomy was performed, the presence of synthetic lubricant noted and the articular cartilages examined for macroscopic evidence of osteoarthritis. These cartilages were then fixed, embedded, sectioned, stained and graded histologically for osteoarthritis according to a modified Mankin scoring system.

Immunohistochemical studies were performed to assess for any inflammatory or cytotoxic effect by the lubricant.

Results: All guinea-pigs remained healthy and mobile throughout the study.

Subjective macroscopic assessment of the medial tibial plateau osteophyte was noted to be larger and the articular surface more roughened in the control cases compared to the lubricated cases. Synthetic lubricant was noted at arthrotomy in all cases where it was injected.

Guinea-pig joints treated with the synthetic lubricant showed a mean modified Mankin score of 3.0 points compared with the guinea-pig joints treated with saline where the median modified Mankin score was 8.5 points (p< 0.001). There was no evidence of an inflammatory or cytotoxic response by immunohistochemical studies.

Discussion: This study has confirmed that inert synthetic perfluoroalkylether lubricants can remain in the articular space for prolonged periods and inhibit the development of osteoarthritis without initiating an inflammatory response. Synthetic lubricants such as PFAE16350 warrant further investigation for potential use in osteoarthritis.

Introduction: Although there is evidence that laminar flow operating theatres (LFOTs) can reduce the incidence of wound infection over standard operating theatres (STOTs) when no routine peri-operative antibiotics were used, the evidence for the use with concurrent parenteral antibiotics is less compelling. A number of prior studies have compared the bacterial load observed in LFOTs and STOTs by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the polymerase chain reaction (PCR), a molecular biology test for the presence of bacterial DNA. The purpose of this study was to compare the wound contamination rate during THRs performed in STOT with that in LFOTs using PCR.

Method: Patients undergoing primary THR for osteoarthritis without a history of joint infection were recruited for the study. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date.

Results: In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture (80 specimens and 40 THRs in total).

Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs. Of these 12, three were taken at the start of surgery and nine at the end of the surgery, equivalent to a 45% wound contamination rate (9 of 20). Only two specimens (5%), both taken at the end of surgery, were positive on enriched culture.

In LFOTs, bacterial DNA was identified by PCR on eight of 40 specimens (20%). Of these eight, two were taken at the start of surgery and six at the end of surgery, equivalent to a 30% wound contamination rate (6 of 20). None of the specimens were positive on enriched culture.

Discussions: We concluded that wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data are important in that they confirm that continued vigilance to technique continue to be important as significant wound contamination can occur despite the use of ultra clean air operating theatres.

Research is the quest for information. It is not an excuse for attending meetings in exotic places, nor is it an escape from clinical work that has become uninteresting. The early orthopaedic joumals contained reports of patients who have been treated by individual surgeons in specific, often novel, ways. There was little scientific structure, but nevertheless these papers were valuable as they disseminated knowledge to other Surgeons and also stimulated enquiry.

Orthopaedic research has developed dramatically over the last two or three decades. Patient related research has been advanced as a result of the availability of new techniques for example electron microscopy, DNA sequencing and the Genome, together with the discovery of the fine details of the cytokine control of cellular processes. This has gone hand in hand with the development of surgical sophistication allowing more adventurous interventions.

Joint replacement and internal fixation have led to close associations between orthopaedic surgeons and scientists from other disciplines, notably engineers and material scientists. This multi-disciplinary involvement is typical of orthopaedic surgeons and results in each discipline benefiting from the specialist knowledge of the others. The natural tendeney for orthopaedic surgeons to be interested in mechanical items is clear from a study of the distribution of interesting cars in the hospital car park!

The efficacy of different treatment methods should be challenged and this has resulted in the need for careful audit and epidemiological review. In some instances this has resulted in the conclusion that often used treatments are not effective. The assiduous application of the Cochrane principles is often very revealing, not least in that it indicates the lack of properly conducted orthopaedic trials.

Academic orthopaedics is in danger. In many countries the speciality is under pressure, normally as a result of economic measures that restrict the avallability of salarles and grants. In spite of these restrictions, it is surprising that there is a steady supply of excellent papers. How much better it could be with more funding.

The purpose of publícation is to share information. It should be the aim of every research worker to make a contribution to the understanding of the subject and to share his findings with his colleagues. Curiously many researchers feeI that their commitment to their project is complete as soon as they finish the trial and have the results. The preparafion of their work for dissemination through publication is often a very weak link and in some instances is absent. This is a dangerous tendency as their information may not be broadcast, wasting the scientific endeavour and endangering the status of the fundíng organisation, whose charitable status often depends on sharing the fruitg of research.

The incentive to publish is very variable. In some institutions the very existenee of a research department depends on a ‘paper score’ which is normally calculated from the product of the number of papers and the impact factor of the j ournal in which they are published. The calculation used to determine the impact factor of ajournal does not favour orthopaedic journals, as most orthopaedic papers are not quoted prolifically within the first year of publication. In contrast orthopaedic papers tend to have a much longer and more valuable lifetime and to some this is the more important and relevant feature. Unfortunately, the long-term value of the papers is not part of the calculation of impact factor. In order to achieve a high impact factor the publication must be in a rapidly changing field and contain at least a tiny element of special originality, which leads to it being quoted by most of the workers in that field. In the publishing world there is an ongoing discussion conceming an index that is more relevant than the impact factor.

For some, the competition for publication is so intense that there is ‘salami slicing’. Salami slicing is a process of publishing very small morsels of information in short papers instead of producing the complete study. It is done intentionally to increase the number of papers published and is frowned upon by scientific editors. Even worse there are cases of plagiarism and fraud, sadly occurring more commonly in surgical publication, than in other disciplines.

It may be time to ask fundamental questions about the need for research, articularly the need for every doctor in training to improve or embellish his or her Curriculum Vitae by decorating it with published works. There ís a tendeney for the more wealthy and better respected grant awarding bodies to fund successful rescarch teams, rather than to risk their limited resources on a spectacular project from an unknown team.

Funding is avallable from commercial sources. The role of this type of rescarch may require special assessment. There are issues of intellectual property rights and instances of commercial organisations delaymg or preventing publication if the findings of the study are not favourable. Many cynical readers give no weight to papers that are sponsored by commercial sources.

It is essential that rescarch in orthopaedics continues and that every possible step is taken in order to facilitate high quality research. There may be strength in numbers and it could be that the newly revitalised European Orthopaedic Research Society could help in supporting the endeavours of rescarch workers, particularly when it comes to European funding.

There is evidence that fractures heal more rapidly in patients with head injury. We measured the circulating level of interleukin-6 (IL-6) and its soluble receptor (sIL-6R) and soluble glycoprotein 130 (sgp130) in serum from patients who had sustained a head injury with and without fracture and compared these with levels found in control subjects.

Within 12 hours of injury the serum level of IL-6 was significantly higher in patients with head injury and fracture compared with the control group. Levels of IL-6 were also significantly higher in patients with head injury and fracture compared with fracture only. While there was no significant difference in circulating levels of sIL-6R in the initial samples they were increased one week after surgery in patients with head injury and fracture and with head injury only. In addition, reduced levels of sgp130 in patients with head injury with and without fracture indicated a possible reduction of the inhibitory effect of this protein on the activity of IL-6.

Our study suggests that IL-6 may be involved in altered healing of a fracture after head injury.