Sterile Allogeneic Spongioflex® Allograft as Partial Meniscal Replacement After Incomplete Meniscal Loss, an Investigator-initiated Low Interventional Trial.

The menisci consist of fibrocartilage. They are partially (laterally more than medially) mobile parts of the joint surfaces and compensate for the incongruence of the femur and tibia. They reduce the joint pressure on the tibial plateau and the femoral condyles and help to stabilize the joint. Due to this biomechanical relevance, the partial loss of the meniscus leads to arthritic changes in long term. Suturing the torn meniscus is increasingly becoming the focus of knee surgery. Degenerative torn menisci have a significantly poorer prognosis with regard to healing than traumatically torn menisci (e.g. meniscus damage associated with a cruciate ligament tear).

Indications for partial meniscus replacement are symptomatic, degenerative, and irreparable damage to the medial and lateral meniscus, possibly with early osteoarthritis of the compartments, as well as partial loss of the meniscus in the event of anterior knee instability in young, active patients, in which case simultaneous reconstruction of the anterior cruciate ligament should be performed. A prerequisite for a good clinical result after partial meniscus replacement is a stable knee without malalignment in the coronal plane. Partial meniscus replacement is not suitable in the case of axial deviation and knee instability, patients older than 60 years, advanced chondromalacia and degenerative changes in the affected compartment, an extension deficit of more than 3° compared to the opposite side or a knee flexion of less than 125°. Inflammatory arthritis or synovial inflammation of the knee and a Body Mass Index (BMI) greater than 30 kg/m² are additional exclusion criteria.

Williams et al. 2007 could show, that 5 years after partial removal of the medial or lateral meniscus, despite an excellent functional result, 64% of patients showed medial and 33% lateral cartilage damage on magnetic resonance imaging (MRI). This study highlights the considerable delay with which the symptoms occur despite already detectable arthritic changes.

Englund et al. were able to show in a study that patients developed osteoarthritis significantly more frequently over a period of 30 months if they had meniscus damage than if they did not. Englund et al. detected tibiofemoral osteoarthritis in 27% of patients 15 years after partial meniscus removal compared to 10% in a control group that had not undergone surgery.

In the case of incomplete meniscus loss, where the peripheral rim is sufficiently intact, defect filling is the only way to restore the lost substance and function of the meniscus. In the past, an implant made of bovine collagen (Collagen Meniscus Implant (CMI), Stryker) or an artificial meniscus made of polyurethane (Actifit, 2med) was often used. The CMI has been withdrawn from the market by the manufacturer, so that no biological treatment alternative exists.