Effects of controlled abnormal joint movement on the molecular biological response in intra-articular tissues during the acute phase of anterior cruciate ligament injury in a rat model

Biologic Impact of Anterior Cruciate Ligament Injury and Reconstruction

Surgical intervention after anterior cruciate ligament (ACL) tears is typically required because of the limited healing capacity of the ACL. However, mechanical factors and the inflammatory response triggered by the injury and surgery can impact patient outcomes. This review explores key aspects of ACL injury and reconstruction biology, including the inflammatory response, limited spontaneous healing, secondary inflammation after reconstruction, and graft healing processes. Understanding these biologic mechanisms is crucial for developing new treatment strategies and enhancing patient well-being. By shedding light on these aspects, clinicians and researchers can work toward improving quality of life for individuals affected by ACL tears.

The infrapatellar fat pad contributes to spontaneous healing after complete anterior cruciate ligament injury

Anterior cruciate ligament (ACL) injuries have a very low healing capacity but have recently been shown to heal spontaneously with conservative treatment. This study examined the mechanism of spontaneous ACL healing by focusing on the intra-articular tissues of the knee joint. Skeletally mature Wistar rats (n = 70) were randomly assigned to two groups: the controlled abnormal movement (CAM) and anterior cruciate ligament transection (ACLT) groups. The ACL was completely transected at the mid-portion in both groups. Only the CAM group underwent extra-articular braking to control for abnormal tibial translation. The animals were allowed full cage activity until sacrifice for histological, and molecular biology analyses. The results showed that the behavior of the stump after ACL injury differed between models 12 h after injury. The femoral stump in the ACLT group retreated posteriorly and upwardly. Macrophage polarity analysis revealed that the stump immune response in the CAM group was more activated than that in the ACLT group 6 h after injury. Microarray analysis of the ACL parenchyma and infrapatellar fat pads suggested the involvement of nuclear factor kappa B (NF-κB) signaling. Real-time polymerase chain reaction (PCR) analysis showed that NF-κB gene expression in the infrapatellar fat pad was significantly increased in the CAM group than in the ACLT group. However, there was no difference in the gene expression levels in the ACL parenchyma between models. In conclusion, the healing response of the ACL was activated within 12 h of injury, resulting in differences in the healing response between the models. It has been suggested that infrapatellar fat pads are involved in the healing process and that angiogenesis and antiapoptotic effects through NF-κB signaling may contribute to this mechanism.

A comparative study of the epiligament of the medial collateral and anterior cruciate ligaments in the human knee: Immunohistochemical analysis of CD 34, α-smooth muscle actin and vascular endothelial growth factor in relation to epiligament theory

BACKGROUND

This study evaluated and compared the expression of VEGF, CD34, and α-SMA in the anterior cruciate ligaments and medial collateral ligaments in healthy human knees in order to enrich the epiligament theory regarding ligament healing after injury.

METHODS

Samples from the mid-substance of the anterior cruciate ligament and the medial collateral ligament of 12 fresh knee joints were used. Monoclonal antibodies against CD34, α-SMA, and VEGF were used for immunohistochemical analysis. Photomicrographs were analyzed using the ImageJ software.

RESULTS

The epiligament of the anterior cruciate ligament showed slightly higher expression of CD34, α-SMA, and VEGF than the epiligament of the medial collateral ligament. Overall, among the tested markers, α-SMA expression was most pronounced in anterior cruciate ligament epiligament images and CD34 dominated in medial collateral ligament epiligament images. The intensity of DAB staining for CD34, α-SMA, and VEGF was higher in vascular areas of the epiligament than in epiligament connective tissue.

CONCLUSIONS

The results illustrate that CD34, α-SMA, and VEGF are expressed in the human epiligament. The differences between the epiligament of the investigated ligaments and the fact that CD34, α-SMA, and VEGF, which are known to have a definite role in ligament healing, are predominantly expressed in the main vascular part of the ligament-epiligament complex enlarge the existing epiligament theory. Future investigations regarding better ligament healing should not overlook the epiligament tissue.

Influence of the site of injury on the spontaneous healing response in a rat model of total rupture of the anterior cruciate ligament

AIM

The healing ability of the anterior cruciate ligament (ACL) injury is very poor; however, it has recently been shown to undergo self-healing with conservative treatments. In this study, we evaluated the influence of the site of injury on the healing process after complete transverse tear of ACL using a rat model.

MATERIALS AND METHODS

A total of 58 skeletally mature Wistar rats were randomly assigned to various ACL injury groups: controlled abnormal movement-mid-portion (CAM-MP), controlled abnormal movement-femoral side (CAM-FS), ACL transection-mid-portion (ACLT-MP), or ACL transection-femoral side (ACLT-FS) injury groups. The ACL was completely transected in the mid-portion in the ACLT-MP and CAM-MP groups, and on the femoral side in the ACLT-FS and CAM-FS groups. Both CAM groups underwent extra-articular braking to control for abnormal tibial translation. The animals were allowed full cage activity until sacrifice postoperatively for histological and biomechanical assessment.

RESULTS

Significant differences were found in the ratios of residual ligament lengths between the CAM-MP and CAM-FS groups, demonstrating the validity of each model. Spontaneous healing of the injured ACL was observed in the CAM-MP and CAM-FS groups but not in the ACLT-MP and ACLT-FS groups. The mechanical strength of the healing ACL did not differ between the CAM-MP and CAM-FS groups 8 weeks after injury; however, the former had better mechanical strength than the latter 12 weeks after the injury.

CONCLUSION

ACL injuries in the mid-portion and on the femoral side may be treated with conservative therapy for spontaneous healing.

The novel epiligament theory: differences in healing failure between the medial collateral and anterior cruciate ligaments

According to current literature, 90% of knee ligament injuries involve the medial collateral ligament or the anterior cruciate ligament. In contrast to the medial collateral ligament, which regenerates relatively well, the anterior cruciate ligament demonstrates compromised healing. In the past, there were numerous studies in animal models that examined the healing process of these ligaments, and different explanations were established. Although the healing of these ligaments has been largely investigated and different theories exist, unanswered questions persist.

Therefore, the aim of this article is 1) to review the different historical aspects of healing of the medial collateral ligament and present the theories for healing failure of the anterior cruciate ligament; 2) to examine the novel epiligament theory explaining the medial collateral ligament healing process and failure of anterior cruciate ligament healing; and 3) to discuss why the enveloping tissue microstructure of the aforementioned ligaments needs to be examined in future studies.

We believe that knowledge of the novel epiligament theory will lead to a better understanding of the normal healing process for implementing optimal treatments, as well as a more holistic explanation for anterior cruciate ligament healing failure.

A comparative study of the epiligament of the medial collateral and the anterior cruciate ligament in the human knee. Immunohistochemical analysis of collagen type I and V and procollagen type III

BACKGROUND

Recent reports in rat models have shown that fibroblasts in the epiligament, an enveloping tissue of the ligament, are not static cells and play an important role during the early ligament healing of isolated grade III injury of the collateral ligaments of the knee. Fibroblasts produce collagen types I, III and V and infiltrate within the ligament body via the endoligament. In addition, similarities have been reported between the structure of the epiligament of the medial collateral ligament and anterior cruciate ligament of the knee in rat and in human. In line with the ascribed role of the epiligament tissue and the synthesis of these collagens and their role in ligament healing, the aim of this study was to determine their presence in the normal epiligament of the aforementioned ligaments in humans, to compare their differential expression and to present a novel hypothesis about the failure of healing of the anterior cruciate ligament in contrast to the medial collateral ligament.

MATERIALS AND METHODS

We used samples from the mid-substance of the medial collateral and the anterior cruciate ligament of the knee joint, acquired from 12 fresh knee joints. Routine histological analysis was performed through hematoxylin and eosin stain, Mallory's trichrome stain and Van Gieson's stain. The immunohistochemical analysis was conducted using monoclonal antibodies against collagen type I and V and procollagen type III. The number of cells in the epiligament, endoligament and the ligament tissue was assessed quantitatively through a computerized system for image analysis NIS-Elements Advanced Research and Statistica software.

RESULTS

Our observations revealed certain differences in the morphology of the epiligament, as well as variations in the expression of the investigated molecules. Expression of collagen type I was mostly low-positive (1+) in the epiligament and positive (2+) in the ligament tissue of both ligaments. Expression of procollagen type III was mostly positive (2+) in the epiligament and ligament tissue of the medial collateral ligament, low-positive (1+) in the epiligament and negative (0) in ligament tissue of the anterior cruciate ligament. Expression of collagen type V was predominantly low-positive (1+) in the epiligament and negative (0) in the ligament tissue of both ligaments. The immunoreactivity for all three molecules was always higher in the epiligament of the medial collateral ligament than that of the anterior cruciate ligament.

CONCLUSIONS

The results of our study illustrate for the first time that fibroblasts in the human epiligament are indeed responsible for the synthesis of the main types of collagen participating in the early ligament healing, thus corresponding to previous data of the medial collateral ligament healing in animal models. The differences between the epiligament of the investigated ligaments could add a novel explanation for the failed anterior cruciate ligament healing.

Determining the effective timing of an open arthrolysis for post-traumatic elbow stiffness: a retrospective cohort study

Background

Following trauma, the elbow is the most susceptible to restricted motion among all joints. Open arthrolysis is often performed for post-traumatic elbow stiffness if that stiffness does not improve with non-operative management. However, the optimal timing for performing an open arthrolysis remains controversial. The purpose of this study was to compare the outcome (elbow motion and function) and the rate of complications among patients who had undergone early, median and late release procedures to establish an optimal time interval following the injury, after which, an effective open arthrolysis can be performed.

Methods

In this retrospective cohort study, we included total 133 patients, who had undergone open arthrolysis for post-traumatic elbow stiffness. The subjects were divided into 3 groups, with 31 patients in the early release group (arthrolysis performed at 6–10 months after injury), 78 patients in the median release group (at 11–20 months), and 24 patients in the late release group (at > 20 months). The release procedure in all patients was performed by the same surgeon, using the same technique. The general data, functional performance, and complications, if any, were retrospectively documented for all patients and statistically analysed.

Results

The demographic data and disease characteristics of all patients were comparable at baseline. Postoperatively, no significant differences were found among the three groups with respect to the range of motion (p = 0.067), Mayo Elbow Performance Score (p = 0.350) and its ratings (p = 0.329), visual analog scale score for pain (p = 0.227), Dellon classification for ulnar nerve symptoms (p = 0.497), and each discrete complication (all p values > 0.05).

Conclusions

At the final follow-up, our results showed no significant difference in the postoperative elbow motion capacities, functional scores and the rates of complications among patients who had undergone an early, median, and late release. Therefore, we have recommended that an early arthrolysis would be preferable due to its multiple advantages, and the conventionally observed interval of > 1 year after the injury, could be shortened.

Level of evidence

Level III; Retrospective Cohort Design; Therapeutic Study.