Abstract
Introduction
Osteoarthritis (OA) represents a leading cause of disability and a growing burden on healthcare budgets. OA is particularly vexing for young, active patients who have failed less invasive therapies but are not yet candidates for arthroplasty. Often, patients suffering in this wide therapeutic gap face a debilitating spiral of disease progression, increasing pain, and decreasing activity until they become suitable arthroplasty patients. An implantable load absorber was evaluated for the treatment of medial knee OA in this patient population.
Joint overload has been cited as a contributor to OA onset or progression. In response, the KineSpring® System (Moximed, Inc, USA) has been designed to reduce the load acting on the knee. The absorber is implanted in the subcutaneous tissue without violating the joint capsule, thus preserving the option of future arthroplasty. The implant is particularly useful for young, active patients, given the reversibility of the procedure and the preservation of normal flexibility and range of motion.
Methods and Results
The KineSpring System was implanted in 55 patients, with the longest duration exceeding two years. The treated group had medial knee OA, included younger OA sufferers (range 31–68 years), with a mean BMI > 30kg/m2. Acute implant success, adverse events, and clinical outcomes using validated patient reported outcomes tools were recorded at baseline, post-op, 2 and 6 weeks, and 3, 6, 12 and 24 months post-op.
All patients were successfully implanted with a mean procedure time of 76.4 min (range 54–153 minutes). Mean hospital length of stay was 1.7 days (range 1–3 days), and patients recovered rapidly, achieving full weight bearing within 1–2 wks and normal range of motion by 6 weeks. Most patients experienced pain relief and functional improvement with 85% (35/41) reporting none or mild pain on the WOMAC pain subscale and 90% (37/41) reporting functional impairment as none on mild on the WOMAC function subscale at the latest follow-up visit (mean 9.3 ± 3.5 months). Clinically meaningful and statistically significant pain reduction and functional improvement were noted with baseline WOMAC pain scores (0–100 scale) improving from 42.4 to 16.1 (p<0.001) and WOMAC function (0–100 scale) improving from 42.0 to 14.7 (p<0.001) at latest follow-up. Patients reported satisfaction with the implant and its appearance.
Conclusions
The KineSpring System preserves natural knee anatomy and kinematics while providing pain reduction and resumption of high activity levels that have proven durable. This device, with these excellent results, fills a major gap in treatment options for young and active OA patients.
