A biomechanical and histological evaluation of the structure and function of the healing medial collateral ligament in a goat model

Abstract

This study evaluated the healing process of an isolated medial collateral ligament (MCL) rupture at 12 weeks in a goat model. Using a robotic/UFS testing system, knee kinematics in multiple degrees of freedom and in situ forces in the healing MCL in response to (1) a 67-N anterior tibial load and (2) a 5-Nm valgus moment were evaluated as a function of angles of knee flexion. Then a uniaxial tensile test of femur-MCL-tibia complexes (FMTCs) was preformed to obtain the structural properties of the FMTC and mechanical properties of the healing MCL substance. The histological appearance of the healing MCL was also examined for collagen and cell organization. The anterior tibial translation in response to a 67-N anterior tibial load was found to range from 1.9 to 2.4 mm, which was not significantly different from the sham-operated, contralateral control knee. In response to a 5-Nm valgus moment, however, MCL injury caused a 40% or more increase in valgus rotations over sham-operated controls for all angles of knee flexion tested. The magnitudes of the in situ forces in the healing MCLs for neither external loading conditions differed from sham-operated controls. For the structural properties of the healing FMTC, the stiffness returned to sham-operated control levels, but ultimate load at failure remained 60% of sham-operated control values. In terms of mechanical properties of the healing MCL, its tangent modulus and stress at failure were only 40% of sham-operated control values. Histologically, the collagen and cell organization at the femoral and tibial insertions as well as the midsubstance remained disorganized. Comparing these data to those previously reported at 6 weeks, there was a marked improvement in the in situ forces in the healing MCL and of the stiffness of the FMTC. Also, the data obtained for the goat model revealed a faster healing process than those for the rabbit model. These findings suggest that greater post-injury activity levels may render the goat to be a better animal model for studying the healing process of the MCL.

Comparison between Operative and Non-Operative Treatment of the Medial Collateral Ligament: Histological and Ultrastructural Findings during Early Healing in the Epiligament Tissue in a Rat Knee Model

“…These authors considered that a possible reason for that may be that the operative treatment with suture application probably accelerates the healing process to such degree that angiogenesis is reversed or the reposition of the ends of the injured ligament hinders the neovascularization. Some studies have shown that even 52 weeks after injury, the mechanical properties of the torn ligament remain weaker than those of the control [Inoue et al, 1990;Loitz-Ramage et al, 1997;Abramowitch et al, 2003]. They are not improved even on the second year after injury [Inoue et al, 1990;Loitz-Ramage et al, 1997;Abramowitch et al, 2003].…”

“…Arguments against conservative treatment are based on this very instability, as well as on subjective complaints, muscle weakness, a higher incidence of subsequent traumatic injuries and posttraumatic osteoarthritis [Kannus, 1988]. Abramowitch et al [2003] hypothesized that the valgus-varus instability of the knee joint may be a result of non-operative treatment. However, it has been proved experimentally that treatment by means of suture reduces varus-valgus rotation only initially and that there is no statistically significant difference between operated and unoperated animals [Weiss et al, 1991].…”

Ligament Injury and Healing: A Review of Current Clinical Diagnostics and Therapeutics

“…More specifically, ACL and MCL structures tend to heal at varying rates comparatively, and the quality of remodeled tissue overall among different animal species remains inferior to that of normal ligaments [53,54,56,60,63,68,[79][80][81][82][83]. In fact, studies of healing ligaments have consistently shown that certain ligaments do not heal independently following rupture, and those that do heal, do so with characteristically inferior compositional properties compared with normal tissue [64,74,84,85].…”

Consideration of growth factors and bio-scaffolds for treatment of combined grade II MCL and ACL injury

“…The underlying premise behind this line of reasoning was that the healing MCL could eventually develop sufficient structural integrity to replicate pre-morbid function with the presence of any residual laxity being inconsequential to knee joint health. Several reports, however, have suggested that Grade II MCL injuries that are allowed to heal naturally are likely to be histologically, mechanically, and functionally deficient compared to a healthy, non-injured MCL [1,[16][17][18]51]. The healing MCL becomes denser by 3-6 weeks postinjury when it begins to remodel.…”

“…There are three basic approaches to improve MCL healing: (1) alter cellular components at the lesion site. (2) alter what the cells at the lesion site express (gene therapy), or (3) some combination of #1 and #2 [19].…”