Histological Changes in the Blood Vessels of Ruptured Human Anterior Cruciate Ligaments

Anterior cruciate ligament (ACL) rupture is a commonly encountered sports injury worldwide. ACL rupture is known to have poor healing capacity, hypothesized to be due to low vascularity. ACL reconstruction surgery with ligament removal and tendon graft became essential for the higher grades of ACL tears. However, ACL-reconstructed patients faced post-traumatic osteoarthritis 10-15 years after surgery. In the recent past, the tibial remnant of ACL was shown to have intrinsic healing potential. Blood vessel density and the location of blood vessels of ACL remnants have critical implications in the newly upcoming remnant-preservation ACL reconstruction surgeries that showed better healing response. This study was performed to characterize the histological features of ruptured ACL remnants in terms of blood vessels to assess the healing potential and their utility in novel surgical techniques.

This was a descriptive cross-sectional study in which the tibial remnant of 24 ruptured ACL samples was evaluated for blood vessel density (per sq. mm), luminal area (sq. µm), and location of blood vessels using hematoxylin and eosin (H&E) staining with ImageJ software (U. S. National Institutes of Health, Bethesda, Maryland, USA). The blood vessel density and location of blood vessels were compared among various groups based on the duration of injury and number of injuries.

Twenty-three male and one female adult patients with a mean duration of injury of 7.54 ± 5.63 months (range: 2-24 months) were included in the study. They were divided into three groups based on duration of injury: group I (2-5 months; n = 10), group II (6-8 months; n = 8), and group III (9-24 months; n = 6). The median blood vessel density (blood vessels per sq. mm) was 5.50 (3.30, 10.23) per sq. mm. There was no correlation of blood vessel density observed with duration of injury. All groups showed similar results statistically. More patients in earlier duration of injury showed very high range (10.1-40 per sq. mm) of blood vessels compared to the patients of later duration. Immature and intermediary blood vessels were identified denoting angiogenesis. Location of blood vessels varied in the groups based on duration of injury. There was no significant difference in blood vessel density and location of blood vessels between patients with single injury and those with multiple injuries.

The present study demonstrates the presence of healing potential of ruptured anterior cruciate ligaments in terms of blood vessel density, luminal area, and location of blood vessels. Future studies looking into the functional outcome would enhance the understanding of utility of novel remnant-preservation surgeries in place of standard graft reconstruction surgeries.