Title: Prevent bone fracture during or shortly after hip replacement surgery
Funder: Department of Health and Social Care

Abstract: Research question Can a force limiting instrument reduce the risk of fracture in hip replacement surgery? Background The NHS performs 100,000 hip replacements annually. Periprosthetic fracture is the second most common short term complication. Half these fractures occur when the surgeon impacts the broaching tool into the femur using a hammer. The impact force generated by the hammer is uncontrolled and highly variable depending on the mass of the hammer and how hard the surgeon hits. Aim & Objectives Aim: To create a surgical instrument that reduces the risk of fracture. Objectives: (1) Define a safe impact force for different femur types, (2) Validate our instrument reduces risk of fracture in laboratory testing, (3) CE mark instrument & first-in-man use. Methods The force limiting component is an additively manufactured lattice structure that yields at a safe impact force. This yielding dissipates high energy over a longer duration thus reducing peak force. The safe impact force will be determined by measuring the strain in cadaver femur specimens. These specimens are selected to capture the range of morphology and bone density of total hip replacement patients. We will validate our instrument in a paired femur analysis, one used with, and one without the force limiting instrument. Timelines for delivery We plan for a CE marked instrument, with first-in-man use at the end of 24 months. Anticipated impact The work will reduce the cost burden of fracture for the NHS, it will improve the wellbeing of hip replacement patients and surgeons by reducing the risk of surgery and it will help establish a British manufacturing company which will benefit regional supply chains and manufacturing jobs in the UK.

Lay abstract: Aims of the research Our proposal will develop a way of preventing the fractures that accidently occur during hip replacement treatment. Background of the research The NHS performs approximately 100,000 hip replacement operations every year and the demand is growing due to our ageing population. In about 5,000 of these the thigh bone is accidently cracked or even broken by the surgeon. This usually means another operation with all the added risk for the patient. The second operation is less successful, more expensive and has more complications than an uncomplicated operation in the first place. Design and methods used The main cause of thigh bone fracture during the operation is when the bone is prepared to accept the implant. The tool used to prepare the bone is put into the top of the thigh bone and struck by a metal hammer to create the space for the implant. If the force delivered by the hammer is too strong, it can crack the bone. We propose creating a bone preparation tool that has a built in force limiter so that the bone never experiences high forces, even if the force delivered by the hammer is too high. This has now been made possible by the introduction of 3D printing in surgical grade stainless steel. We have already proven this works with a prototype device that could be struck with any force on one end, but always delivered a fixed force out the other end. Patient & Public Involvement A patient advisory group has already helped to define the project and will continue to help the team to decide on priorities. This group will also be involved in disseminating the work through public engagement activities and writing material for non-academic audiences. Dissemination In order to ensure the research reaches clinical practice in the shortest possible time, a team from Imperial College will lead the design work of the force limiter and prove that it reduces the risk of bone damage. At the same time, our university spin-out company will undertake the development work to ensure the force limiter meets the strict regulations that govern the medical sector. Once we have achieved this, we will partner with one of the major implant manufacturers with global distribution networks, enabling the force limiter to be used as widely as possible for the benefit of all patients.

Research activity codes: 6.3 MEDICAL DEVICES;5.3 MEDICAL DEVICES
Health categories: MUSCULOSKELETAL