Systematic Review
“Ligamentization” in Hamstring Tendon Grafts After Anterior Cruciate Ligament Reconstruction: A Systematic Review of the Literature and a Glimpse Into the Future

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Purpose

The aims of this study were to provide a systematic review of the literature on “ligamentization” in hamstring tendon (HT) grafts after anterior cruciate ligament (ACL) reconstruction and analyze the postoperative remodeling process in human patients and animal models.

Methods

We performed a search in the Medline, PubMed, Embase and The Cochrane Library databases, followed by a manual search of reference lists to identify relevant articles. Only studies that investigated the ligamentization of hamstring grafts by histologic examination and comprehensively reported on the remodeling process were deemed eligible for review.

Results

A total of 4 studies were determined appropriate for systematic review: 2 of the included studies investigated human ACL grafts and 2 were performed in animal models. The studies included the examination of 79 human hamstring graft biopsy specimens and grafts of 27 skeletally mature sheep. To verify the remodeling process, authors reported on various aspects of cellularity, vascularity, and collagen organization. None of the included studies reached a level of evidence higher than 3.

Conclusions

A postoperative ligamentization process can be found in HT grafts after ACL reconstruction and shows a typical progression through 3 distinguishable remodeling phases in humans and in animal models, whereas the progression and intensity of remodeling is distinctly increased in animals.

Clinical Relevance

Because postoperative remodeling influences biomechanical properties of hamstring grafts, a better understanding of this process and its timing could lead to substantial improvements in postoperative care strategies and indirectly to the optimization of surgical techniques.

Section snippets

Search Strategy

We performed a systematic review of the literature in Medline, PubMed, Embase, and The Cochrane Library databases on July 7, 2012 to identify all published studies reporting on the postoperative remodeling processes of HT grafts after ACL reconstruction. The search included all entries from the respective database's starting date to the day of our search, including articles published online as “Epub ahead of print.” For the computerized search, a combination of search terms related to the

Search Results

Our search revealed 906 potentially relevant articles. After the removal of duplicates, titles and abstracts of the remaining 383 articles were screened for relevance. This process identified 17 articles that were obtained for detailed evaluation.

Additionally, the reference lists of these articles were manually screened for relevant publications to ensure comprehensiveness of the literature search. This complementary search revealed one additional article, which was retrieved for further

Discussion

According to the progression of cellularity, vessel density, and other histologic signs of graft maturity, all included studies reported the identification of 3 consecutive distinguishable phases of postoperative remodeling.

Controlled human studies illustrating ligamentization of PT grafts found that an initial healing phase was finished 6 months after surgery, followed by intense remodeling, which was shown to recede at 12 months, to a final maturation phase, which was shown to be ongoing at

Conclusions

In principle, ligamentization occurs in human and animal hamstring grafts in a way similar to that previously reported in PT grafts. Furthermore, the postoperative healing process of HT grafts shows a typical progression through 3 chronological, distinguishable remodeling phases, whereas the progression and intensity of remodeling is distinctly increased in animals.

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    The authors report that they have no conflicts of interest in the authorship and publication of this article.

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