The extracellular remodeling of free-soft-tissue autografts and allografts for reconstruction of the anterior cruciate ligament: a comparison study in a sheep model

Abstract

Our study was aimed to advance the currently limited knowledge about differences in the biological remodeling of free soft-tissue tendon allografts and autografts for ACL reconstruction. Allogenic and autologous ACL reconstructions were performed in a sheep model using the flexor digitalis superficialis tendon. After 6, 12 and 52 weeks the animals were sacrificed. We analyzed the collagen crimp formation and its relationship to expression of contractile myofibroblasts in both graft types. Additionally, structural properties and ap-laxity were compared during biomechanical testing. At 6 weeks only descriptive differences were found between autografts and allografts with a more organized crimp pattern and myofibroblast distribution in autografts. Significant differences in myofibroblast density and crimp formation were found after 12 weeks. At these early stages, the progress of remodeling in autografts was more advanced toward the central areas than in allografts. At 1 year, grafts in both study groups returned to an ACL-similar structure. Structural properties and ap-laxity did not vary significantly between auto- and allografts at early healing stages. However, at 52 weeks, failure loads, stiffness and ap-drawer test showed superior values for autograft ACL reconstruction. Extracellular remodeling of allografts develops slower than in autografts. Therefore, rehabilitation procedures will have to be adapted according to graft and patient selection. Postoperative treatment regimens from autograft primary ACL reconstruction should not be directly transferred to allograft ACL reconstructions.

Tibial tunnel enlargement and joint instability after anterior cruciate ligament reconstruction. A prospective comparison between autograft and allograft

“…In addition, van Eck et al have proved that the allograft failure was associated with early return to sports and high sports intensity 14 . So we advocate a less aggressive rehabilitation, and this opinion is consistent with that of Dustmann et al 15 . At the first six weeks postoperatively, ROM rehabilitation program is formulated on a weekly basis, and if the involved knee has achieved the required flexion angle for every week, knee flexion will be restricted to avoid repeated tensile force on the graft.…”

Remodeling of ACL Allografts is Inhibited by Peracetic Acid Sterilization

“…It is unclear whether the substantial crimp elongation of the PAA grafts was a result of inhibited healing or just a delay of remodeling, since no later time points were evaluated. Nonetheless, our qualitative analysis of the crimp pattern suggests the extent of crimp degradation and reorganization was substantially less in PAA grafts than what had been previously shown for nonsterilized allo-and autografts [7], providing further evidence of impaired remodeling activity.…”

“…In contrast, PAA graft cellularity only slightly increased during early healing and did not recover to values of the intact ACL, while graft vascularity never exceeded the values for the intact ACL and substantially lagged behind nonsterilized ACL alloand autografts [1,12,35]. The longer crimp of ACL autoand allografts than in the intact ACL, appears characteristic for the time of simultaneous degradation and reorganization of the extracellular matrix [7]. Restoration of the intact ACL crimp length occurs with continuing graft maturity by 1 year postoperatively [7].…”

“…The longer crimp of ACL autoand allografts than in the intact ACL, appears characteristic for the time of simultaneous degradation and reorganization of the extracellular matrix [7]. Restoration of the intact ACL crimp length occurs with continuing graft maturity by 1 year postoperatively [7]. However, our quantitative analysis of crimp length of PAA grafts remains inconclusive.…”

“…Allografts eliminate harvest morbidity and reportedly allow faster rehabilitation, earlier return to full activity, and possible cost reduction [4,10,25]. Disadvantages of using allografts, however, include potential disease transmission and prolonged graft healing [7,11,22,26,31,33]. Even though the risk of infection following allograft transplantation is very small, fatal incidences have been reported [31].…”