# ANTERIOR CRUCIATE LIGAMENT HEALING

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA, SAN DIEGO · 1987 · $152,435

## Abstract

The limitation in the healing response of the anterior cruciate ligament
(ACL) are well recognized.  Several hypotheses have been proposed to
explain why this tissue fails to heal, including mechanical retraction of
the ends, and nutritional deprivation resulting from a limited blood
supply.  Others propose that synovial fluid may exert a deleterious effect
on repair, because of proteolytic enzymes which may be harmful to immature
proliferating cells and matrix at the repair site.  It is presently
believed that the failure of ACL repair is most likely the result of a
multifactorial process.

In contrast, we have demonstrated intrinisic repair of flexor tendon in the
flexor tendon sheath when intermittent passive motion is utilized.  The
healing occurs more rapidly and with greater strength than with traditional
techniques which permit tissue ingrowth from the tendon sheath of the
immobilized digit.  The tendon sheath environment is seemingly as "hostile"
as that of the ACL, with similar limitations of blood supply and nutrition
in both cases.  Why is intrinsic healing so effective in the case of
tendon, but so limited in the case of the ACL?

Our laboratory has recently developed a model of ACL injury which
demonstrates healing in a reproducible manner.  We have also developed a
new methodology which standardizes biomechanical testing of the ACL.  These
will be valuable tools in understanding the biology of this ligament.
These advances will be incorporated into a multidisciplinary investigation
involving histological, biochemical, biomechanical and nutritional
studies.  ACL repair rate and repair quality will be compared to those of
the medial collateral ligament, a ligament with a soft tissue environment.
In light of the fact that passive motion was useful in flexor tendon
healing, the influrence of past-injury activity on ACL healing will also be
studied.

We have also demonstrated successful ACL reconstruction in rabbits, and
plan a multidisciplinary study of the natural history of ACL autografts of
patellar tendon origin.  We have shown that these autografts undergo a
gradual metamorphosis, acquiring histological and biochemical properties
very similar to normal ACL with time.

These advances in model development will allow a detailed study of the
healing and reconstructed ACL and should provide valuable insight as to the
most appropriate treatment for injuries of this ligament.

## Key facts

- **NIH application ID:** 3156767
- **Project number:** 5R01AR034264-04
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN DIEGO
- **SAM.gov UEI:** UYTTZT6G9DT1
- **Principal Investigator:** Wayne H. Akeson
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1987
- **Award amount:** $152,435
- **Award type:** 5
- **Project period:** 1984-07-01 → 1989-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3156767

## Citation

> US National Institutes of Health, RePORTER application 3156767, ANTERIOR CRUCIATE LIGAMENT HEALING (5R01AR034264-04). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3156767. Licensed CC0.

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