An implantable shock absorber yields an 85% survival-from-arthroplasty rate through 5 years in working-age patients with medial compartment knee osteoarthritis

• Published in: Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA Vol. 31; no. 8; pp. 3307 - 3315
• Main Authors: Gomoll, Andreas H., Diduch, David R., Flanigan, David C., Ranawat, Anil S., Slynarski, Konrad, Walawski, Jacek, Crawford, Dennis C.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2023; John Wiley & Sons, Inc
• Subjects: Age; Arthritis; Arthroplasty; Clinical trials; Implantation; Joint surgery; Knee; Medicine; Medicine & Public Health; Orthopedics; Osteoarthritis; Osteotomy; Pain; Patients; Shock absorbers; Sports Medicine; Survival; Transplants & implants; Total knee arthroplasty; Survivorship; WOMAC pain and function score; Implantable shock absorber; Functional outcomes; Medial compartment knee osteoarthritis
• ISSN: 0942-2056; 1433-7347; 1433-7347
• DOI: 10.1007/s00167-023-07373-4

Purpose To evaluate the 5-year rate of survival without undergoing arthroplasty or high tibial osteotomy (HTO) in subjects with mild-to-moderate medial compartment knee osteoarthritis (OA) who were treated with an implantable shock absorber (ISA) system. Methods Three prospective, sequential, multicenter, international, single-arm clinical trials were conducted comprising subjects who received an ISA for symptomatic medial knee OA after failing ≥ 6 months of conservative therapy. Study outcomes were analyzed cumulatively and by enrollment group when all subjects’ follow-up data exceeded the 2-year threshold after ISA implantation. Primary outcome was survival rate without conversion to arthroplasty/HTO. Secondary outcomes were changes in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and function scores after ISA implantation. Results All 171 enrolled subjects (age 51 ± 9 years, body-mass index 28.5 ± 3.5 kg/m 2 , 38% female; study knee Kellgren–Lawrence score 2.7 ± 0.9 points) were followed for a minimum of 2, and up to 5, years after device implantation. Overall, 90.6% (155/171) of subjects survived without requiring arthroplasty/HTO at last follow-up (mean 3.2 ± 1.6 years). The Kaplan–Meyer median 3- and 5-year survival-without-arthroplasty point estimates were 89.8% (95% CI 86.5‒95.7%) and 84.9% (95% CI 75.1‒91.1%), respectively. The median 3-year estimated survival rate for the most recent study ( n  = 81) was 97.3%. The mean WOMAC Pain score decreased 71% from baseline to last follow-up after ISA implantation, from 58 ± 13 to 16 ± 17 points ( p  < 0.0001). The Function score improved 69%, decreasing from 56 ± 18 to 17 ± 17 points ( p  < 0.0001). Conclusions In younger patients with mild-to-moderate symptomatic medial compartment knee OA, implantation of the ISA device resulted in a 5-year survival rate of 85% from undergoing arthroplasty or HTO. The ISA system may be an effective treatment option for working-age patients with medial knee OA who are not candidates for or do not desire more invasive surgical approaches. Level of evidence II.