Orthopaedic cobalt chromium particles and ions can induce indirect DNA damage and chromosome aberrations in human cells on the other side of a cellular barrier in tissue culture. This occurs by intercellular signalling across the barrier. We now show that the threshold for this effect depends on the metal form and the particle composition.

Ionic cobalt and chromium induced single strand breaks at concentrations equivalent to those found in the blood of patients with well functioning metal on metal hip prostheses. However, they only caused double strand breaks if the chromium was present as chromium (VI), and did not induce chromosome aberrations. Nanoparticles of cobalt chromium alloy caused DNA double strand breaks and chromosome aberrations, of which the majority were tetraploidy. Ceramic nanoparticles induced only single strand breaks and/or alkaline labile sites when indirectly exposed to human fibroblasts.

The assessment of reproductive risk from maternal exposure to biomaterials, especially those liberated by orthopaedic implants, is not yet possible with epidemiology. Whilst the barrier model used here differs from the in vivo situation in several respects, it may be useful as a framework to evaluate biomaterial induced damage across physiological barriers.

It is generally accepted that urgent debridement and fixation of open tibial fractures minimizes the risk of infection. Traditionally surgeons follow the unwritten six hour rule. The purpose of this study was to determine the association between time to definite surgical management and rates of infection in open fractures of the tibia.

One hundred and twenty-seven patients with one hundred and twenty-eight open tibia fractures were retrospectively reviewed. Of these ninety patients with ninety-one one fractures were available for this study. All patients were followed up to clinical and radiological fracture union or until a definitive procedure for infection or non-union had been carried out.

The time from injury to surgery ranged from 2 hours 35 minutes to 12 hours with an average time of 5 hours 40 minutes. There were 24 Gustillo type I fractures (26.37%), 11 type II fractures (12.08%), 23 type IIIA fractures (25.27%) and 33 type IIIB fractures (36.26%). 5 patients (5.49%) in this study went onto develop a deep infection and there were 4(4.39%) non-unions. No infection occurred when the surgery was done within 2 hours. All the 5 infections in this study occurred in patients operated between 3 to 8 hours of the injury and were all in Gustillo Grade III fractures. The average time to treatment was not significantly different between the infected versus non infected group across all fracture types. There was no increase in infection rate in those treated after 6 hours compared to those treated within 6 hours.

The risk of developing an infection was not increased if the primary surgical management was delayed more than 6 hours after injury provided intravenous antibiotics were administered on presentation to the emergency department. The Gustillo grading of open fractures is a more accurate prognostic indicator for developing an infection.

Introduction: It is generally accepted that urgent debride-ment and fixation minimizes the risk of infection. Traditionally surgeons follow the unwritten six hour rule. The purpose of this study was to determine the association between time to definite surgical management and rates of infection in open fractures of the tibia.

Methods: One hundred and twenty-seven patients with one hundred and twenty-eight open tibia fractures were retrospectively reviewed. Of these sixty patients with sixty fractures were available for this study. All patients were followed up to clinical and radiological fracture union or until a definitive procedure for infection or non-union had been carried out.

Results: The time from injury to surgery ranged from 2 hours 35 minutes to 12 hours with an average time of 5 hours 40 minutes. There were 23 type IIIA fractures (38%) and 37 type IIIB fractures (62%). 5 patients (5.49%) in this study went onto develop a deep infection and there were 4(4.39%) non-unions. No infection occurred when the surgery was done within 2 hours. All the 5 infections in this study occurred in patients operated between 3 to 8 hours of the injury. The average time to treatment was not significantly different between the infected versus non infected group across all fracture types. There was no increase in infection rate in those treated after 6 hours compared to those treated within 6 hours.

Conclusions: The risk of developing an infection was not increased if the primary surgical management was delayed more than 6 hours after injury provided intravenous antibiotics were administered on presentation to the emergency department. The Gustillo grading of open fractures is a more accurate prognostic indicator for developing an infection.

Increasing numbers of young people receive metal on metal (CoCr on CoCr) total hip replacements. These implants generate nano-particles and ions of Co and Cr. Previous studies have shown that micro-particles, nano-particles and ions of CoCr cause DNA damage and chromosomal abberrations in human fibroblasts in tissue culture, and in lymphocytes and bone marrow cells in patients with implants. Several surgeons have used these implants in women of child-bearing age who have subsequently had children. Significantly elevated levels of cobalt and cromium ions have been measured in cord blood of pregnant women with CoCr hip implants. The MHRA (Medicines and Healthcare products Regulatory Agency) subsequently stated that there is a need to determine whether exposure to cobalt and chromium represents a health risk during pregnancy.

In an attempt to investigate this risk, we used a well established in vitro model of the placental barrier comprised of BeWo cells (3 cells in thickness) derived from the chorion and exposed this barrier to nanometer (29nm) and micron (3.4μm) sized CoCr particles, as well as ions of Co2+ and Cr6+ individually or in combination. We monitored DNA damage in BJ fibroblasts beneath the barrier with the alkaline gel electrophoresis comet assay and with γH2AX staining.

The results showed evidence of DNA damage after all types of exposure. The indirect damage (through the barrier) was equal to the direct damage at the concentrations tested. The integrity of the barriers was checked with measurements of electrical resistance (TEER values) and permeability to sodium fluorescein (376Da) and found to be intact.

In light of these results and with the knowledge that BeWo cells express the transmembrane protein Connexin 43, we tested the theory that a damaging signal was being relayed via gap junctions or hemi channels in the BeWo cells to the underlying fibroblasts. We used the connexin mimetic peptides Gap19 and Gap26 (known to selectively block hemichannels and gap junctions respectively) and 18α-glycyrrhetinic acid (non-selective gap junction blocker). All of these compounds completely obliterated the indirect damaging effect seen in our previous experiments.

We conclude that CoCr particles can cause DNA damage through a seemingly intact barrier, and that this damage occurs via a bystander mechanism. It would be of interest to test whether this is simply a tissue culture effect or could be seen in vivo.

Introduction: Mismatch between patient load and out-patient clinic resources in South Australian public sector has resulted in a long waiting list for initial appointment of new patients with shoulder complaints. There is no validated triage tool to help prioritize the patient referrals appropriately, to avoid inappropriate delays.

Methods: We devised a self evaluation questionnaire to appropriately triage new referrals with shoulder complaints. Ethics committee approval was obtained. Forty eight new referrals to shoulder clinic filled in this questionnaire and the self evaluation part of American Shoulder and Elbow Society form. The patients were assessed in chronological order by two surgeons. Both were blinded to the GP referral and questionnaire findings at the time of patient assessment. GP referrals and the questionnaires were subsequently assessed and triaged. These findings were compared to assessment in the clinic.

Results: Whilst the questionnaire provided significantly more information when compared to GP referrals, both were inadequate on their own as reliable triage tool. However in combination, majority of the patients could be triaged appropriately. Based on the presumptive diagnosis, basic investigations and therapy can be correctly instituted whilst awaiting formal orthopaedic review. None of the patients would have been allocated a lower priority than appropriate. The self evaluation part of ASES form on its own was not a satisfactory tool for triaging.

Discussion: The proposed questionnaire and initial referral letter can be used for safe triaging and ensuring most basic relevant clinical workup is done prior to presentation. Further refinement of the questionnaire and additional studies are required to fully define its role in routine public hospital use.

Limited wrist arthrodesis has been shown to be an effective treatment for the degenerative and unstable wrist, abolishing pain but limiting motion. The aim of the study was to assess the effect of excision of the scaphoid and triquetrum on wrist joint range of motion, in the setting of a limited midcarpal arthrodesis. Twelve cadaveric wrists had the range of motion measured, before and after, ulnar four-corner fusion (lunate, capitate, triquetrum and hamate fusion). This was measured again following sequential scaphoid and triquetral resection.

Scaphoid excision after four-corner arthrodesis resulted in a 12 degrees increase in the radio-ulnar (R-U) arc and 10 degrees increase in the flexion-extension (F-E) arc range of motion. Subsequent excision of the triquetrum, to produce a three-corner fusion, further increased R-U arc by seven degrees and F-E arc by six degrees.

These results demonstrate that three-corner fusion with excision of scaphoid and triquetrum results in improvement in wrist motion when compared to four-corner fusion with scaphoid excision alone. From this we conclude that triquetrum excision should be considered in Scapholunate advanced collapse (SLAC) wrist reconstruction to improve residual wrist range of motion.

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.

Joint replacement failure is usually caused by the formation of wear debris resulting in aseptic loosening. Particulate metal and soluble metal ions from orthopaedic alloys (cobalt chromium or vanadium titanium aluminium) that are used in medical prostheses can accumulate in tissues and blood leading to increased chromosome aberrations in bone marrow and peripheral blood lymphocytes. This paper demonstrates that two of the metals used in orthopaedic prostheses, chromium and vanadium can produce delayed as well as immediate effects on the chromosomes of human fibroblasts in vitro. Fibroblasts were exposed to metal ions for only 24 hours and were then expanded over 30 population doublings involving ten passages. The initial increase of chromosomal aberrations, micronuclei formation and cell loss due to lethal mutations persisted over multiple population doublings, thereby demonstrating genomic instability. Differences were seen in the reactions of normal human fibroblasts and those infected with a retrovirus carrying the cDNA encoding hTERT that rendered the normal human fibroblasts telomerase-positive and replicatively immortal. This suggests that chromosomal instability caused by metal ions is influenced by telomere length or telomerase activity. Formerly this syndrome of genomic instability has been demonstrated in two forms following irradiation. One type is non-clonal and involves the appearance of lethal aberrations that cannot have been carried by the surviving cells. The other type is clonal and the aberrations are not lethal. These may arise as a result of complex rearrangements occurring at a high rate post-insult in surviving cells. The consequences of genomic instability are not yet known but it is possible that the increase of chromosomal aberrations that have been previously observed in human patients could be due to immediate and delayed expression of cellular damage after exposure to orthopaedic metals.

Previous research has shown an increase in chromosomal aberrations in patients with worn implants. The type of aberration depended on the type of metal alloy in the prosthesis. We have investigated the metal-specific difference in the level of DNA damage (DNA stand breaks and alkali labile sites) induced by culturing human fibroblasts in synovial fluid retrieved at revision arthroplasty.

All six samples from revision cobalt-chromium metal-on-metal and four of six samples from cobalt-chromium metal-on-polyethylene prostheses caused DNA damage. By contrast, none of six samples from revision stainless-steel metal-on-polyethylene prostheses caused significant damage. Samples of cobalt-chromium alloy left to corrode in phosphate-buffered saline also caused DNA damage and this depended on a synergistic effect between the cobalt and chromium ions.

Our results further emphasise that epidemiological studies of orthopaedic implants should take account of the type of metal alloy used.

Introduction Radio-scapho-lunate (RSL) arthrodesis has been shown to be an effective treatment for arthritis limited to the radio-carpal joint. It preserves wrist motion at the mid-carpal joint while relieving pain. The main shortcoming of this procedure has been restricted residual wrist range of motion (ROM) compromising clinical outcome. The aim of the study was to assess the effect of excision of distal scaphoid and triquetrum on wrist motion following RSL arthrodesis.

Methods Ten cadaveric wrists had their range of motion measured before and after RSL arthrodesis and after sequential distal scaphoid and then triquetral resection. The mean and standard deviation of the change in motion were calculated for each step. The two-tailed Student’s t-test with p < 0.05 was used to determine the statistical significance of the changes.

Results Distal scaphoid excision after RSL arthrodesis resulted in 25° (35%, p< 0.01) increase in flexion-extension (F-E) arc and 11° (34%, p< 0.01) increase in radio-ulnar (R-U) arc. Subsequent excision of triquetrum further increased F-E arc by 13° (13%, p< 0.05) and R-U arc by 9° (21%, p< 0.01).

Conclusions In the cadaveric wrists, distal scaphoid excision resulted in significantly improved R-U arc and F-E arc. Subsequent triquetral excision further improved wrist ROM. Modification of RSL fusion to include distal scaphoid and triquetrum excision should be considered to improve residual wrist motion.

Introduction Proximal femoral fractures (PFF) in the elderly have high complication rates contributing to associated morbidity and mortality. This study aimed to identify any specific patterns or factors contributing to surgical failures requiring re-operation in these patients.

Methods A retrospective review of 441 PFF treated operatively during a consecutive 27 month period was performed. Relevant data was obtained from operation records, medical records and x-ray reviews. The re-operation rate was calculated according to the fixation method (e.g. DHS) as well as fracture type (e.g. intertrochanteric).

Results Of the PFF treated operatively 40 required subsequent procedure(s). There were 28 mechanical failures and 12 deep infections. Of the mechanical failures four required more than one subsequent operation and five patients died within six months of revision surgery. Technical error was a significant factor in six of the 28. Repeat falls during the post-operative rehabilitation phase accounted for the majority of periprosthetic fractures. Of the deep infections five required removal of hardware and seven underwent incision and drainage. Dynamic condylar screw fixation for the subtrochanteric fractures had higher mechanical failure (50%) compared to intramedullary nail fixation (13%).

Conclusions Technical error, improper implant selection and falls during post-operative rehabilitation period are significant factors contributing to failures in PFF fixation and should be avoided.