The randomised controlled trial will be carried out on patients that require a total hip replacement (THR) to reduce pain and restore their function. One way of fixing the hip joint to the bone is by coating the implant to encourage the body to grow bone onto the replacement hip. This study is aiming to find out whether the new (Bonemaster) coating allows increased bony growth onto the cup when compared to the usual (plasma-sprayed) coating. This may reduce the incidence of early failures due to poor bony attachment, which is a well known complication for early failure of total hip replacements.

The study will compare two different types of coating (BoneMaster and Plasma-sprayed) on the cup of the replacement hip. Density of the bone immediately surrounding the cup will be observed to see if there are differences between the two groups. The density of bone will be measured using standard x-ray assessment and in a smaller sample of 14 patients, using a special scan called Dual Energy X-ray Absorptiometry (DEXA Scan). Functional comparisons will be assessed through clinical scores.

The patients will be identified by the orthopaedic surgeon in the orthopaedic clinic and deemed suitable for the study if all inclusion and exclusion criteria are met. 210 patients will be recruited to the study and each patient will be randomised into either of the groups allowing 105 patients into each group. Patients will be followed up at 6 months, 1 year and 2 years after the surgery. All patients will have radiographic assessments at these follow-up intervals, as well as Harris Hip, Oxford Hip and Womac scores. This will allow comparison of the two groups.

The BoneMaster coating has been extensively tested in cell and animal studies and has been evaluated in one previous clinical study and showed favorable results. Further investigation is required to ensure the new coating may enhance bony growth allowing better fixation of the hips in the early period after the operation and also over a longer period of time. The growth needs to be measured using a more sensitive scan than radiographic assessment alone, called DEXA which was also used in the previous study.

Inclusion Criteria

• Patients suitable for THR surgery with a diagnosis of Osteoarthritis
• Patients aged 40 -85 years old.
• Patients with limited co-morbidity - ASA I - III (low risk for surgery)
• Patients must be able to understand instructions and be willing to return for follow up

Exclusion Criteria

• Rheumatoid arthritis
• Patients requiring supplemental screw fixation
• Previous hip surgery to the affected hip
• Patients with significant co-morbidity - ASA IV - V (high risk for surgery)
• Dementia
• Neurological conditions affecting everyday functional ability and hip movement
• The patient is unable to give informed consent
• Patients who have suffered from cancer
• The patient is currently part of another research study
• Patients who need to take Non Steroidal Anti-inflammatory Drugs (NSAIDs) in the first 6 weeks after surgery