What we are doing 

In work package 4, the HIPPY programme wants to definitively answer which implants are best for patients under 70 years of age receiving primary elective hip replacement.  

Primary hip replacement involves replacing a damaged hip joint with an artificial implant that has two main parts. One part (the stem) goes into the thigh bone (femur) and ends in a ball which fits into a socket or cup attached to the pelvis, making a ball-and-socket joint. Implants can be fixed to bone with cement (cemented), without cement (uncemented), or partially cemented (hybrid). Cemented implants (cup and stem components are fixed to the bone with cement) have a long track-record of use worldwide and perform better regardless of hospital or surgeon expertise. Uncemented (stem and cup are press-fit to the bone) and hybrid implants (cemented stem and uncemented cup) are often more expensive and more frequently used in the younger patients.

Our previous Hip Implant Prosthesis Study showed that cemented metal-on-polyethylene hip implants are the most cost-effective option in men 75 year or older and women 65 years or older. For younger patients, cemented implants also ranked higher, but the evidence is very uncertain and has not warranted a change in guidance. An NIHR signal and BMJ editorial called for new trial evidence on revision surgery for the younger primary hip replacement patients.

How we are doing it

The HIPPY trial will recruit nearly 8,000 patients under 70 years of age undergoing primary elective hip replacement. People undergoing primary elective hip replacement will be randomised to receive cemented, uncemented, or hybrid implants.

The primary outcome of the HIPPY trial is the number of patients requiring a revision surgery within 10 years from having the primary surgery. We will follow people up in the long-term by linking study participants to their records in the National Joint Registry and their hospital data, such as the Hospital Episode Statistics or the Patient Episode Database for Wales.  Participants will also be asked to complete some questions about their health, hip function, and wellbeing approximately 6-months and 12-months after their surgery. 

We will run this trial in approximately 100 hospitals in England and Wales. Any hospital providing hip replacement surgery to NHS funded patients can take part. Surgeons will be able to choose whether to randomise their patients to two or three implant fixation types (cemented, hybrid or uncemented), and can choose bearing surface material combinations, sizes and all other surgical options according to their usual preference.