Natural history of healing in the repaired medial collateral ligament

Abstract

The purpose of this study was to assess morphologically the healing of repaired medial collateral ligaments (MCLs) in a rabbit model. Healing ligaments were examined grossly and histologically at various intervals, from 3 days to 2 1/2 years after injury, and compared with the appearances of normal age-, sex-, and activity-matched controls. Results show that all ligaments healed by bridging scar formation rather than true ligament regeneration. Increases in cellularity and temporary matrix disorganization along the entire length of the ligaments during healing suggest a combination of diffuse mechanical damage from their failure in tension and regional inflammatory injury (in excess of surgical exposure alone) from the processes of degradation and replacement. Substance that was not injured physically in this model demonstrated complete recovery, while that replaced by scar did not. Healing processes were similar to those of other highly specialized soft tissues (e.g., tendons), with short phases of hemorrhage and inflammation, an intermediate phase of proliferation, and a prolonged phase of remodeling. Failure of repairs to maintain anatomical apposition of torn ends may have contributed to the delay of these healing processes by increasing scar mass. Incomplete scar remodeling at 2 1/2 years, however, suggests much slower MCL healing than previously reported and probably, therefore, a longer period for potential treatment influence.

Type I and type III procollagen gene expressions in the early phase of ligament healing in rabbits: an in situ hybridization study

“…In our study, the expression of type I procollagen gene increased not only in the scar tissue but also at the ends of the previously normal ligament. This suggests that fibroblasts in this "intermediate area" [6], as well as those in the scar tissue, respond early after injury and contribute to restoring the function of the healing ligament by synthesizing type I collagen, which is considered to be more mature and to contribute more to the mechanical properties of the ligament than type I11 [ll]. On the other hand, the increased expression of type 111 procollagen gene was observed almost only in the newly created scar tissue at 7 days after injury.…”

Early biological effect of in vivo gene transfer of platelet-derived growth factor (PDGF)-B into healing patellar ligament

“…The healed ligament is biologically scar-like and is biomechanically inferior to normal ligament tissue. [4][5][6][7] At present, despite a variety of acute treatments including surgical repairs, grafting and physiotherapy, the optimal conditions for the healing of ligaments have still not been established. Further, even the 'functional success' of treatment does not appear to be preventing osteoarthritis.…”

Promotion of rabbit ligament healing by local delivery of hepatocyte growth factor

“…1 Yet, the mechanical properties, collagen types and histological appearance are not restored to pre-injury levels even after 1 to 2 years. 2,3 Clinically, severe isolated MCL injuries take several months for return pre-injury activity level, and they may require MCL surgery because of residual valgus laxity. Controversy remains regarding the best treatment for the MCL in combined ligamentous injuries.…”