Introduction: Failed surgical treatment of hip fractures typically leads to profound functional disability and pain for the individual, technical challenges for the surgical team, and an increase in the financial burden on society. This study had three purposes:

to determine the reason/s for failure of internal fixation

Methods: Between 1999 and 2005 41 patients (30 women and 11 men) with a mean age of 70 were treated at our institution with a total hip arthroplasty for failed dynamic hip screw fixation of a fracture of the proximal femur. The radiographs and medical charts of all patients were obtained following institutional approval. The quality of the reduction of the fracture achieved was assessed on the basis of displacement and alignment. Screw position was also assessed. Each patient who had undergone salvage arthroplasty (Group 1) was matched with a patient who had undergone total hip arthroplasty for degenerative disease in our unit (Group 2). Patients were matched for age, sex, implant and time since insertion of the implant. All surviving patients form both groups were followed up for a minimum of two years (mean 5 years). Three main outcome measures were compared between the two groups; surgical complications, the Oxford hip score, and radiographic analysis of the femoral component for signs of loosening

Results: Failure to achieve a good reduction and optimal screw placement was evident in 80% of cases of failed fixation. A high incidence of complications was recorded in the perioperative period during conversion to a salvage arthroplasty. Functional outcome was statistically inferior in Group1, this group also had a much higher incidence of complications. Radiographs at 2 years post operatively showed evidence of femoral stem loosening in 16% of the salvage group compared with 3% in the primary hip arthroplasty group.

Conclusion: When undertaking surgical stabilisation of proximal femoral fractures one should make every effort to achieve the best reduction and most accurate fixation possible. Factors such as osteoporosis, compliance with post-operative mobilisation and delay in fracture fixation are to some extent ‘out of the surgeon’s hands’. Conversion to arthroplasty is technically challenging, and is associated with higher complication rate and poorer outcome than primary hip arthroplasty. We recorded a high incidence of femoral stem loosening in patients who had undergone conversion to hip arthroplasty for failed fixation and would recommend more frequent clinical and radiographic follow up of these patients

Background: The success of the increasing number of arthroplasty, spinal instrumentation and other implanted orthopaedic devices is hampered by device-related infections. More than half of these infections are caused by staphylococcal biofilm mediated antibiotic resistance. The hope of preventing prosthetic joint infection by antibiotic loaded cement is threatened by emerging resistant organisms. No bacterial resistance to betadine has been reported.

Current intervention strategy is focussed on prevention of initial device colonisation and inhibition of genes encoding biofilm formation.

Aim:

Determine the minimum inhibitory concentration (MIC) of betadine.

Methods: MIC of betadine for both reference strains and strains isolated from infected orthopaedic implants was determined. Biofilm assay was performed at different betadine concentrations using 96-well polystyrene plates.

Total RNA for cDNA synthesis was isolated from bacterial at different twofold dilutions of betadine concentrations.

Real time polymerase chain reaction was used to quantify effects of betadine on gene expression pattern of the icaADBC operon using the constitutively expressed gyrB gene as internal control.

Bacterial was cultivated on polystyrene plates coated with different sub-inhibitory and clinical in-use doses of betadine to assess surface adherence.

Results: The MIC of betadine was 1.4% for all bacterial strains. Clinical in-use doses of betadine prevented biofilm formation.

A step-wise reduction of biofilm was observed at increasing sub-inhibitory doses of betadine (p< 0.0001).

IcaA expression correlated with biofilm formation in staphylococcal organisms. Decrease in icaA expression was strongly associated with an increase in expression in the biofilm repressor gene, icaR.

The repressive effect of betadine on biofilm formation by Staphylococcal bacteria is by a separate mechanism from its bacteriostatic mechanism of action.

Conclusion: This study shows that icaR is a potential therapeutic target through which the ability of Staphylococcal bacterial to form biofilm may be reduced. Sub-inhibitory dose of betadine inhibited biofilm formation.

Prevention of bacterial surface attachment as demonstrated by this study is suggestive that these compounds could be developed as a surface coating agents for orthopaedic implants.

Introduction: There is concern that cobalt and chromium ions released from metal on metal (MOM) bearing surfaces may have an adverse effect on renal function over time.

Aim: The aim of this study was to assess renal function in patients who have had MOM hip resurfacing at between two and seven years follow up.

Methods and Materials: Seventy seven patients had MOM hip resurfacing performed in our unit between 1st March 2001 and 28th February 2006. All patients were invited to present for an up to date renal profile. Of these, 59 patients volunteered a sample (76%). Forty-eight were male and eleven were female. Ages ranged from 33 to 63 years (mean 59 years). Nine patients had hypertension pre-operatively. No other risk factors for renal dysfunction were present in our patient population.

Results: Pre-operative urea and creatinine levels ranged from 2.9 to 10.6mmol/L (mean 6.4mmol/L) and 50 umol/L to 121umol/L (mean 77.2umol/L) respectively. Post-operative urea and creatinine levels ranged from 5.3mmol/L to 6.3mmol/L (mean 5.3mmol/L) and 62umol/L to 75umol/L (mean 67umol/L) respectively. Two patients who had normal serum creatinine profiles pre-operatively showed mildly elevated serum creatinine levels at most recent follow up.

Conclusion: Medium term follow up of patients following MOM hip resurfacing does not suggest evidence for the development of renal impairment in this patient population.

Introduction: It is standard procedure in our unit to use compartment pressure monitoring in all patients presenting with tibial fractures. A sustained difference of less than 30mmhg between the diastolic blood pressure and the compartment pressure (known as the delta pressure) is taken as an indication for fasciotomy.

Aim: To review the impact continuous compartment pressure monitoring has on the management of patients with tibial fractures.

Methods and materials: Between January 2004 and June 2006, 28 patients admitted to our unit following tibial fracture had a compartment pressure monitor inserted. The outer sheath from a 16G cannula connected to an arterial manometer was used in each case.

The records of these 28 patients were reviewed. Twenty three were male. Ages ranged from 19 to 83 years old. Eight patients had open fractures and 20 had closed fractures. Seven patients (25%) had difficulties with communication which could have impeded or delayed the diagnosis of a compartment syndrome.

Results: Average delta pressure ranged from nine to 69mmHg in our patient population. High energy injuries resulted in a significantly lower delta pressure (p=0.05). Open fractures were more likely to result from high energy, although this was not statistically significant (p=0.068). Two patients had fasciotomy performed based on clinical picture and a sustained decrease in delta pressure. No patient had a missed compartment syndrome.

Conclusion: Continuous compartment pressure monitoring is especially useful in patients who are most at risk for compartment syndrome i.e. those having sustained high energy injury or open fractures. It can also aid decision making when the clinical picture of compartment syndrome is equivocal, or when a patient’s ability to communicate pain is impaired.

However, due to the ease of use and the low cost involved, we recommend that all patients with tibial fracture should have continuous compartment pressure monitoring performed.

Introduction: Total hip arthroplasty for osteoarthritis secondary to developmental dysplasia of the hip (DDH) is technically difficult due to the abnormal anatomy involved. The use of a modular hip replacement system is advantageous in that its versatility allows for intra-operative adjustment to accommodate for final acetabular position and version.

Aim: The aim of this study was to assess our early results with the S-ROM hip (DePuy), a cementless modular femoral implant.

Methods and materials: We performed 22 total hip replacements on 20 patients with DDH over a three and a half year period. Nineteen patients were female and one was male. Ages ranged from 30 to 59 years (average 38.3 years). Ten patients had had previous osteotomies performed, including two of whom had Ganz periace-tabular osteotomies performed in our centre.

Nine patients had additional acetabular bone grafting with autologous femoral head, two patients had subtrochanteric osteotomy, and another patient had an adductor tenotomy performed at the time of their surgery. Follow-up ranged from 6 to 44 (mean 19.6) months.

Results: Harris hip scores improved from an average of 42 points pre-operatively to 90 points post-operatively. No radiographic evidence of osteolysis was seen around the femoral implant. Two patients required revision of their acetabular components. Both had satisfactory outcomes.

Conclusion: Our early results with the S-ROM femoral prosthesis correlate well with those from other studies involving arthroplasty for DDH. There were no complications related to the use of uncemented prostheses. Modularity makes this implant extremely versatile and easy to use in this complex patient population.

Introduction: Staphylococcal bacteria, especially the coagulase negative Staphylococci, are responsible for the majority of orthopaedic device related infection. These infections are sub acute, and may not present for months or years following surgery. The virulence of these bacteria is related to their ability to form biofilm, a protective slime which allows them to survive the effects of the host immune system and antimicrobial therapy. Treatment of biofilm based infection almost always necessitates removal of the implant.

Recent work has identified environmental stimuli which induce biofilm formation in Staphylococci. These include stressors such as high temperature, high osmolarity, anaerobiosis, nutrient depletion, salt, ethanol and subinhibitory concentrations of certain antimicrobial drugs. Given the ability of these bacteria to survive the “respiratory burst” from the cells of the mononuclear-macrophage system, we hypothesised that oxidative stress may be one such promoter of biofilm formation by Staphylococci.

Methods and Materials: Staphylococcus epidermidis CSF41498 and Staphylococcus aureus RN422O were selected for study as these are known biofilm forming organisms. Hydrogen peroxide (H₂O₂) was used as an oxidizing agent.

Bacteria were incubated for 24 hours at 37°C in Brain-Heart Infusion (BHI, Oxoid) containing progressively weaker concentrations of H₂O₂ to determine a Minimal Inhibitory Concentration (M.I.C.) for the representative strains. Bacterial viability was assessed by measuring the optical density of the incubated culture using a cell density meter (Ultraspec 10, Amersham Biosciences).

The bacteria were then grown as a biofilm on a 96 well microtitre plate (Nunc) in the presence of subinhibitory concentrations of H₂O₂, using pure BHI as a control. Semiquantative determination of biofilm formation was performed by washing the plates, staining the adherent cells with crystal violet, and measuring the light absorbance of the adherent stained cells at 492 nm using a Multiskan plate reader (Flow Laboratories).

Results: The M.I.C. of H₂O₂ was 18 mM for both Staphylococcus epidermidis CSF41498 and Staphylococcus aureus RN422O. Concentrations of H₂O₂ of 16 mM and below had no normal bacterial growth and replication.

There was no difference in biofilm formation by Staphylococcus epidermidis csf41498 in the presence of 15 mM H₂O₂ when compared to that of the control. However, H₂O₂ had a significant inhibitory effect on biofilm formation by Staphylococcus aureus RN422O, even at a concentration well below the M.I.C.

Conclusion: We conclude that oxidative stress may have an antibiofilm action on certain Staphylococcal species, which is independent from its bactericidal effect, and which is manifest at a concentration below the M.I.C. for that species.

Introduction: An arthroplasty database, such as the Swedish Hip Registry, provides a crude means of quality control over the sizable number of prosthetic implants available on the market today. It provides relatively rapid feedback on the performance of orthopaedic devices and surgical techniques, allowing inferior devices and methods to be discontinued. The maintenance of an arthroplasty register is inexpensive and of enormous benefit to the patient. At present, there is no nationwide arthroplasty register in operation in the Republic of Ireland.

Aim: To develop an arthroplasty register which prospectively captures all clinical, radiographic and medical outcome data on patients undergoing surgery in our unit

Materials and methods We are using an existing computer software programme (Bluespier Patient Manager) to capture our information, although our database is stored independently of this.

Data recorded includes medical outcome scores (WOMAC and MOS SF-36), patient data, operative details (including type of prostheses used and operative technique employed), inpatient course, and any postoperative events. For revision procedures, additional data such as location of bony defects (Gruen zones) and acetabular bone loss (Paprosky classification) are also recorded. Follow up in a special Joint Register Clinic is at six months, two years and every five years thereafter for primary procedures. This is reduced to every two years in the case of revision procedures.

To date, a pilot study involving four surgeons has prospectively captured data on 82 patients undergoing both primary and revision procedures in our unit. We aim to enrol all our patients in the register from July 2005, increasing the amount of data collected, which we hope will subsequently benefit patients undergoing hip and knee arthroplasty in the future.

Introduction: The use of allogeneic blood is associated with many complications. A baseline audit performed in our institution in 2000 showed that 11% of patients undergoing primary total knee arthroplasty required post-operative transfusion. Following this audit, patients undergoing primary knee arthroplasty were no longer routinely cross matched, a Haemovigilance Nurse was employed in compliance with the National Blood Users Group guidelines, and post-operative cell salvage was introduced for patients with a pre-operative haemoglobin level of less than 12 g/dL.

Aim: To assess the impact of these changes on our transfusion practice

Methods and materials A prospective audit was performed over a nine month period, from 1^st January to 30^th September 2003. Data was collected on 233 patients who had primary total knee arthroplasty performed during this period. Patients were transfused if their blood loss exceeded a pre-calculated maximal allowable loss, or based on a 48 hour post-operative haemoglobin level.

Results: Seventeen of the 233 patients (7%) received allogeneic blood. The average amount received was two units. Pre-operative anaemia and advanced patient age were predictive for increased risk of transfusion. Thirty six per cent of patients who were given a cell saver did not collect sufficient blood for re-transfusion. Ten per cent of this group required further transfusion with allogeneic blood.

Conclusion: There was no statistically significant difference in either the percentage of patients transfused or the volume of blood given to each patient between the two periods of audit. We did not find post-operative cell salvage to be an effective method of reducing allogeneic blood use.