The effect of a single local injection of long acting corticosteroid on the healing of acute rat medial collateral Ligament injuries was studied. The medial collateral ligaments of 81 adult female rats were exposed surgically. In 32 rats, the ligament was transected sharply, the overlying muscle was closed, and a human equivalent dose of dexamethasone was injected under the muscle layer, bathing the injured ligament. The identical operation with no corticosteroid injection was done in 32 additional rats: in the remaining 17 animals, the incision was closed without ligament transection or injection. The rats were divided into 3 groups of 25. Each group consisted of 10 rats that were injected, 10 that were not injected, and 5 that underwent sham operations. One group was euthanized 6 days after surgery, 1 group after 10 days, and 1 group after 20 days. Histologic evaluation and biomechanical testing were performed for each subgroup. A cellular pathologist examined a smaller group of 6 rats (2 from each group) for histologic changes 40 days after surgery No histologic differences were noted between the injected and noninjected ligaments 6, 10, or 20 days after injury. At 40 days, the injected specimens showed a slightly more mature crimp pattern than the noninjected specimens. Mechanical testing demonstrated no significant difference in ultimate load or ultimate stress between the injected and noninjected groups, There were no detrimental effects of a single dose administration of dexamethasone on the histologic appearance or biomechanical strength of healing rat medial collateral ligaments.

Corticosteroids are known to inhibit collagen synthesis in vitro as well as having a deleterious effect on ligament healing when applied immediately following injury. An acute injection of betamethasone into a transected rabbit medial collateral ligament significantly impaired the biomechanical and histological properties compared to non-injected transected ligaments. Differences in mechanical, histological and biochemical properties were observed up to 3 months following injury and an acute steroid injection. The present study explored the effects of a corticosteroid (betamethasone) injection 7 days following the initial injury. Biomechanical and histomorphometric analyses were carried determine if the previously observed deleterious effects of a corticosteroid injection immediately following injury can be linked to an interference in the inflammatory phase of healing due to the presence of the corticosteroid.

One hundred and one skeletally mature New Zealand White rabbits were used to study the long-term effects of a single injection of corticosteroid on the biomechanical, histological, and biochemical properties of ligament-healing. Two steroid doses were studied, as previously described. The injections were made into a fascial pocket immediately after transection of the ligament. The animals were killed forty-two and eighty-four days after the injury. In our previous investigation, in which we examined the early (inflammatory and proliferative) phases of ligament-healing, the specimens that had been injected with a dose of steroids equivalent to that given to humans demonstrated significantly inferior biomechanical properties and histological organization relative to controls that had not received an injection. In the current study, we examined the later (remodeling and maturation) phases of ligament-healing and found that the tensile strength (the ultimate stress) of the specimens that had been injected with the steroids returned to a value that was equal to that of the controls that had not received an injection; however, the peak load of the specimens that had been injected with steroids remained inferior to that of the controls. This was accompanied by a lag in the histological maturation.

ABSTRACT Dog bites account for approximately one of 200 emergency room visits. The majority of bites are from dogs known to the victim. Due to the numerous small compartments and the thin covering of soft tissue over the bones and joints, bite wounds to the hand are more likely to become infected than are bites to the arm, leg, or face. Improper management can result in significant morbidity and prolonged treatment. This article discusses the microbiology of dog bite wounds, antibiotic selection, and proper wound management.

One hundred twenty-eight skeletally mature New Zealand White rabbits were used to study the effect of a single corticosteroid injection on the biomechanical, biochemical, and histologic aspects of ligamentous healing. Two steroid dosages were used. The amount of the low-dose steroid was calculated by determining the corticosteroid concentration at which fibroblastic synthesis of collagen was inhibited in vitro. A human equivalent dose of betamethasone was used as the high-dose steroid injection. These two steroid doses and a saline control were injected around a transected medial collateral ligament. At 10 days all groups showed significantly inferior biomechanical properties relative to noninjected controls. By 3 weeks the human equivalent steroid dose group continued to demonstrate significantly inferior properties. Histologic and biochemical analyses confirmed the biomechanical results. The clinical relevance of the study was that the delivery of a human equivalent steroid dose into an acutely injured ligament significantly impairs the healing process relative to a noninjected ligament at 10 days and at 3 weeks after injury. This implies that a corticosteroid-treated injured ligament may not be able to withstand the mechanical loads of early vigorous rehabilitation.

To investigate primary and secondary signs of anterior cruciate ligament (ACL) tear at magnetic resonance (MR) imaging, the authors retrospectively reviewed 103 MR imaging examinations obtained in 99 patients, the original interpretations of these examinations, clinical records, and arthroscopy reports. Fifty cases of arthroscopy-documented complete ACL tear were included. The primary signs of ACL tear (ie, abnormal ACL morphologic features or signal intensity) had respective sensitivity and specificity values of 96% (48 of 50 examinations) and 94% (50 of 53) on sagittal images and 92% (46 of 50) and 83% (43 of 52) on coronal images. As a secondary sign of ACL tear, bone bruise involving the lateral compartment of the knee was found in 40% (20 of 50) of cases of ACL tear and in 4% (2 of 53) of cases of normal ACL. The mean curvature of the posterior cruciate ligament was increased (0.40 vs 0.27; P < .0001) in cases of ACL tear. An abnormal appearance of the ACL on sagittal images remains the single most sensitive and specific sign of ACL tear.