Knee Joint Distraction. Intrinsic Cartilage Repair and Sustained Clinical Benefit

Abstract

Loading is important in the maintenance of joint homeostasis, in which biochemical processes are continuously balancing between a catabolic (breakdown) and an anabolic (synthesis and repair) metabolism. For maintenance of specific joint morphology and -function, load is essential. At the other side of the medal, load can as well be an important factor of joint tissue degradation. The cartilage matrix degrades by wear-and-tear and release of pro-inflammatory and tissue destructive mediators, creating a catabolic environment. All joint tissues are involved in this process, including bone changes and low-grade synovial inflammation. However, in case of minor damage, in which joint stability is maintained, therapeutic unloading may restore joint homeostasis or even switch it towards anabolism. This underlines the regenerative capacity of joint tissues under proper loading. Metabolic processes will be able to re-balance, with adequate synthesis of matrix proteins in combination with diminished release of pro-inflammatory and tissue destructive mediators, eventually resulting in tissue repair activity.

Osteoarthritis (OA) is a condition in which structural tissue damage is accompanied by pain and disability, impairing patients’ mobility and independency. When conservative therapy fails, these complaints will not diminish without surgical interference. This does however not mean that tissues cannot repair themselves, but apparently they need ‘help’. The capability of joint tissue self-repair is in general underestimated. The general view is still that damaged joint tissues, specifically cartilage, are unable to regenerate by intrinsic mechanisms. Indeed, regeneration will not occur without (providing) the proper environment; balancing stimulation by proper loading and with prevention of further wear-and-tear as a result of overload. The ultimate goal in treatment of joint tissue damage should be restoration of the ideal intra-articular load distribution, to initiate repair activity, and a temporary specific biomechanical condition might be a prerequisite to induce a ‘restart’ of efficient tissue repair. Knee joint distraction (KJD) is a treatment strategy potentially providing such an intra-articular condition.

Relatively young patients (<65 years), initially indicated for a total knee prosthesis (TKP) were treated with KJD. In patients under 65 years of age treatment with a TKP is undesirable, because of the increased risk of revision surgery (high costs, less promising results), due to the limited life span of the prosthesis combined with a high demanding active life style. In these patients, KJD resulted in decrease of pain and improvement of joint function, evaluated with the use of validated questionnaires, corroborated by structural tissue repair which is shown by an increased joint space width on weight bearing radiographs and quantitative cartilage measurements on MRI. Until even five years after treatment outcome scores were still statistically significant increased compared to baseline values, which postponed the need for a TKP. Furthermore it was shown that in case of returning complaints, patients can be safely treated with a TKP, not being at higher risk for post-operative infections, with a function of the prosthesis comparable with primary placed ones.