Abstract
Joint load correlates with knee OA incidence, symptoms, radiographic, morphologic and biological changes. Available load modifying therapies are clinically effective but have drawbacks. The KineSpringTM (Moximed Inc), an investigational device, is designed to reduce compartment loads while avoiding the limitations of current treatments. We compare load reductions of braces, HTO and KineSpringTM.
Literature review and experimental data provide compartment load changes for clinically effective knee braces and HTO. Simulated gait testing was completed on four cadaver knees with early-stage OA. Gait was simulated using a cadaver-based kinematic test system that applies motion and loading patterns dynamically to cadaver specimens. Medial and lateral compartment femoro-tibial pressures were measured throughout testing using thin film dynamic pressure sensors (Tekscan, Inc.) placed inframeniscally. Three conditions were tested: no treatment, applied valgus moments to simulate a valgus moment brace, and implanted KineSpring.
Sufficient clinical data exists to support the development of new and novel load modifying therapies for knee OA. Joint load reductions provided by HTO and valgus moment braces provide insight into clinically effective load reduction ranges. Opening wedge HTOs of 5° and 10° are reported to reduce average medial compartment load by 55 N (12 lbs) and 286 N (64 lbs), respectively1. Valgus braces were reported to reduce medial compartment loads an average of 97-280 N (22-63 lbs). From this data we propose a clinically effective load reduction range of 55 to 286N is a valid indicator of the likely clinical success for medial knee load reduction treatments.
Gait simulation was successfully completed in all specimens in all test configurations. The valgus moment brace reduced medial compartment load by 58 ±20 N but did not reach statistical significance. The Kinespring reduced medial compartment load by 129±64 N in comparison to the untreated case, a statistically significant reduction. Neither the KineSpring nor the valgus moment brace caused significant changes in the lateral compartment during stance.
All treatments reduced medial compartment loads. KineSpringTM reduces loads in what we determined to be the clinically effective range. Additional studies and clinical investigations are warranted to determine the ultimate effectiveness of this implant system.
