The Exeter hip

Ling's ambition was to create a hip replacement that could be secured to bony skeleton with acrylic bone cement.^[7] Through extensive laboratory analyses of modified hip implants, Ling and engineer Dr Clive Lee built on the work of Sir John Charnley to demonstrate that over a period of time, bone cement can undergo "creep" and act as a thick liquid. This mechanism permits the transmitting weight through the joint to the skeleton and allows patients to remain pain free and active for years.^[1]

Ling and Lee, using acrylic bone cement, eventually constructed an implant that could be firmly fixed to the bony skeleton.^[8] They proposed a tapered implant profile that would encourage the stem to stay firmly attached to the skeleton for a long period of time.^[1] From 1965, together with Lee, Ling worked on replacement arthroscopy at the School of Engineering, University of Exeter. It was here, that the "Exeter hip" was invented.^[3] Originally called the "Ling-Lee hip", it was first implanted in 1970 and became the most common artificial hip to be inserted.^[8] Unlike previous designs, this hip replacement was inserted through the posterior approach^[9] and required just one assistant.^[7]

The stem of the Exeter hip was a distinct, polished, tapered and cemented part unlike any former hip prosthesis. Its longstanding success was due to this polished tapered design with its capability to perform like a wedge. It was deliberately not bonded, and therefore free to move at the stem-cement border, and consequently behaved as a self-locking point, successfully and persistently tightening step by step during the life of the hip. For the first five years, the Exeter stem was carefully observed in Exeter only. Around 1975 the stem was being made from a heavier steel and the polished surface was not retained. Appearance and cost had led to a matte rather than polished surface, which caused complications of stem loosening and osteolysis. The Exeter stem returned to the original polished surface by 1986 once these complications were realised.^[5] The stem finally changed to a modular system.^[10] Ling, as well as Charnley before him, had in the 1980s, made provisional recommendations for a hip replacement registry, opposed by the department of health but later supported by the National Audit Office (United Kingdom) and NICE.^[9]

Ling was known for carefully following up his patients.^[9] A review of the earliest Exeter hip implants, at 33 years after the first replacements, revealed that 92% did not undergo mechanical loosening.^[10] Sir John Charnley himself was also reported to have observed and commended Ling.^[1] Copies of the Exeter hip have been marketed by leading manufacturers of artificial hips.^[7][11] Internationally, as well as in the UK, 30 years following the first implant, it was the most implanted cemented hip replacement. By the end of 2010, more than one million operations had been done.^[1][12]

Surgical positions

Ling acted as president of the British Orthopaedic Research Society between 1979–80 and was president of the British Orthopaedic Association for 1986–7. He was vice-president of the European Orthopaedic Research Society 1989–1991, president of the British Hip Society 1991–93, and president of the International Hip Society 1997–98.^[3]

Honorary positions

In 1986, Ling was appointed honorary professor of bioengineering in the School of Engineering of the University of Exeter. In 1989, he was given an honorary fellowship of the Royal College of Surgeons of Edinburgh followed by the Order of the British Empire in 1992. He was made a fellow of the Australian Orthopaedic Association in 1999 and an honorary fellow of the British Orthopaedic Association in 2000.^[3]