5-Year Results of an Implantable Shock Absorber Demonstrate Durable Outcomes in Patients with Medial Knee Osteoarthritis

Background: The implantable shock absorber (ISA) addresses patients within the knee osteoarthritis treatment gap between failure of nonsurgical care and arthroplasty. Methods: This follow-up of a prospective, open-label, comparative cohort study reports effectiveness and safety outcomes at 5 years. Results: Eighty-one participants received the ISA. Participants had statistically significant improvement in Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain (mean 43.4 point improvement, p < 0.0001) and function (mean 42.1 point improvement, p < 0.0001) versus baseline, beginning 6 weeks postsurgery, and remaining statistically significant and clinically meaningful through the 5-year follow-up. The study was designed to satisfy regulatory requirements, and survival was defined, a priori, in the study protocol with US Food and Drug Administration to be freedom from conversion to arthroplasty or high tibial osteotomy. At 5 years, 73/81 (90.1%) participants reported conversion-free survival. Conclusion: ISA provided benefits that were statistically significant and clinically meaningful for at least 5 years. Based on these 5-year data of durable, conversion-free survivorship, the ISA has proven to be a treatment option for medial knee osteoarthritis patients.