A medial meniscal tear is a common diagnosis for an orthopaedic surgeon, and a partial meniscectomy is commonly performed to treat these tears. However, because of recent literature supporting increased tibiofemoral contact and increased contact stress after a partial or subtotal meniscectomy1, there has been a heightened interest in repairing meniscal tears. However, the biomechanical effects of complex repairs are poorly understood.
Muriuki and colleagues evaluated both a vertically oriented medial meniscus tear that extended to the posterior horn as well as a radial tear that extended only to the peripheral one-third of the meniscus and assessed their subsequent repairs. It is intriguing to note that although the repair potential of inner margin, radial tears is extremely poor and that most orthopaedic surgeons would perform a saucerization of this tear, leaving as much native meniscus as possible, there is little change in the maximum tibiofemoral contact area or pressure when these tears alone are present. Testing of a repair of this type of incomplete radial tear in a cadaveric specimen yields relatively little clinical information because these tears have a low likelihood of healing. However, these results do raise the intriguing question of whether the treatment may be worse than the tear itself. The true changes in tibiofemoral contact area and pressure when this tear is treated with saucerization have not been elucidated yet. On the other hand, if left untreated because of the concern of causing increased contact pressures and decreased contact area with a partial meniscectomy, these tears may enlarge and involve the peripheral one-third of the meniscus, which would certainly change the distribution of hoop stresses in the medial compartment, similar to a total meniscectomy2. Additionally, if left alone, these radial tears might have a deleterious effect on the articular cartilage wear in the medial compartment.
The biomechanical analysis of the vertical tears involving the posterior root of the medial meniscus created in these cadaveric specimens revealed significant increases in maximum contact pressure and a reduction in contact area in both the medial and lateral compartments with a repair yielding improved values resembling that of an intact medial meniscus. These results confirm data from previous articles3 that tears of the posterior root of the medial meniscus yield contact pressures similar to those following a total medial meniscectomy and should be repaired if possible. The authors should be commended for elucidating the biomechanics following repair of these tears and for confirming the importance of a medial meniscus root repair. However, it should be noted that vertical tears of the medial meniscus more commonly do not involve the posterior root. Therefore, this is a mechanical analysis of a clinically relevant tear but should not be extrapolated to the more common vertical tear without posterior root involvement.
In summary, this study provides a biomechanical rationale for repairing vertically oriented medial meniscal tears involving the posterior root attachment and eloquently elucidates the significant changes in tibiofemoral contact pressure and area in both the torn and repaired states. Additionally, as good scientific papers often do, it raises more questions than it answers regarding inner margin radial tears. These tears alone seem to have little effect on the contact pressures and area in the knee, but the current treatment for these tears, namely partial meniscectomy, likely causes deleterious effects in the knee. Further evaluation of the natural course of inner margin radial tears ought to be undertaken to determine the rate of propagation of the tear to the peripheral margin and the effects on the articular cartilage in the medial compartment.