Mineralization can be an incidental ultrasonographic finding in equine tendons and ligaments.

Tendon/ligament mineralization is recognized in horses but information regarding its clinical significance is limited. The aims of this observational study were to report the structures most commonly affected by ultrasonographically detectable mineralization and, for these, determine frequency of diagnosis and key clinical features. Cases presented at our hospital in April 1999-April 2013 and September 2014-November 2015 were included: a total of 27 horses (22 retrospective, five prospective). Mineralizations were most common in deep digital flexor tendons (10) and suspensory ligament branches (eight), representing 10% and 7% (estimated), respectively, of horses diagnosed with injuries to these structures during the study. Two deep digital flexor tendon and three suspensory ligament branch cases showed bilateral mineralization. Deep digital flexor tendon mineralization was restricted to the digital flexor tendon sheath, most commonly in the proximal sheath (±sesamoidean canal), and seven of 10 cases involved hindlimbs. Suspensory ligament branch mineralization was visible in the same ultrasound window as the proximal sesamoid bones in 10/11 limbs and six of eight cases involved forelimbs. Previous corticosteroid medication was a feature of one deep digital flexor tendon and one suspensory ligament branch case. Mineralization was associated with lameness in some but not all limbs. Mineralized foci within the deep digital flexor tendon preceded hypoechoic lesion formation in two limbs. Of the cases with deep digital flexor tendon or suspensory ligament branch injury only, one of three and two of three cases, respectively, became sound. Findings indicated that tendon/ligament mineralization can be associated with lameness in some horses, but can also be an incidental finding.

IMAGING DIAGNOSIS-IDIOPATHIC HYOID MALFORMATION IN AN 8-YEAR-OLD WELSH SECTION D HORSE.

An 8-year-old gelding was evaluated for intermittent dorsal displacement of the soft palate (DDSP) at exercise. Standing laterolateral radiographs demonstrated an abnormal crossed appearance of the stylohyoid bones. Computed tomography (CT) confirmed abnormal positioning of the left stylohyoid bone and articulations with both the left thyrohyoid and ceratohyoid bones. Surgical treatment consisted of combined left ceratohyoidectomy and thyrohyoidectomy. Postoperatively the patient's presenting complaint resolved completely, with the horse returning to full work. Standing laterolateral radiographs should be obtained prior to laryngeal or hyoid surgery to rule out hyoid anomalies, which could result in surgical failure or subsequent hyoid fracture.

Heterotopic mineralization (ossification or calcification) in tendinopathy or following surgical tendon trauma.

Heterotopic tendon mineralization (ossification or calcification), which may be a feature of tendinopathy or which may develop following surgical trauma (repair or graft harvest), has not received much attention. The purpose of this article is to review the prevalence, mechanisms and consequences of heterotopic tendon mineralization and to identify the gaps in our current understanding. We focus on endochondral heterotopic ossification and draw on knowledge of the mechanisms of this process in other tissues and conditions. Finally, we introduce a novel murine Achilles tendon needle injury model, which will enable us to further study the mechanisms and biomechanical consequences of tendon mineralization.

Post-natal molecular adaptations in anteromedial and posterolateral bundles of the ovine anterior cruciate ligament: one structure with two parts or two distinct ligaments?

The human anterior cruciate ligament (ACL) is a composite structure of two anatomically distinct bundles: an anteromedial (AM) and posterolateral (PL) bundles. Tendons are often used as autografts for surgical reconstruction of ACL following severe injury. However, despite successful surgical reconstruction, some people experience re-rupture and later development of osteoarthritis. Understanding the structure and molecular makeup of normal ACL is essential for its optimal replacement. Reportedly the two bundles display different tensions throughout joint motion and may be fundamentally different. This study assessed the similarities and differences in ultrastructure and molecular composition of the AM and PL bundles to test the hypothesis that the two bundles of the ACL develop unique characteristics with maturation. ACLs from nine mature and six immature sheep were compared. The bundles were examined for mRNA and protein levels of collagen types I, III, V, and VI, and two proteoglycans. The fibril diameter composition of the two bundles was examined with transmission electron microscopy. Maturation does alter the molecular and structural composition of the two bundles of ACL. Although the PL band appears to mature slower than the AM band, no significant differences were detected between the bundles in the mature animals. We thus reject our hypothesis that the two ACL bundles are distinct. The two anatomically distinct bundles of the sheep ACL can be considered as two parts of one structure at maturity and material that would result in a structure of similar functionality can be used to replace each ACL bundle in the sheep.

Osteoarthritis develops in the operated joint of an ovine model following ACL reconstruction with immediate anatomic reattachment of the native ACL.

We tested the hypothesis that immediate reattachment of the native anterior cruciate ligament (ACL) can prevent kinematic changes and the development of osteoarthritis (OA). Five sheep underwent anatomic unilateral ACL reconstruction (ACL-R). Animals from a previous study served as sham (n = 7) or non-operated (n = 17) controls. At 4 points of walking gait, 6 degrees of freedom stifle joint kinematics of ACL-R animals were compared with sham controls at 4 and 20 weeks post-surgery. Gross cartilage, bone, and meniscal changes were graded at euthanasia; paired and differential scores were compared. Inter-animal differences were noted in all groups. Of 48 points of gait comparison between ACL-R and sham operated groups, 42 points showed no difference (p > 0.05). Of the six significant differences (p < 0.05), internal rotation in ACL-R animals accounted for three. At 20 weeks, differential scores showed that sham operated joints were morphologically indistinguishable from non-operated controls (p ≥ 0.129) while ACL-R joints had significantly higher combined cartilage and osteophyte scores than those controls (p ≤ 0.003). This method of ACL reconstruction in sheep did not restore normal walking gait kinematics completely and allowed some OA to develop in operated joints. OA may result from relatively subtle mechanical abnormalities, apparently more so in some individuals than others.

Complete ACL/MCL deficiency induces variable degrees of instability in sheep with specific kinematic abnormalities correlating with degrees of early osteoarthritis.

People are not equally disabled by combined anterior cruciate ligament (ACL)/medial collateral ligament (MCL) injuries, nor do they all develop osteoarthritis (OA). Although biological/biomechanical causes are not clear, some association presumably exists between joint instability and OA development. We hypothesized that degree of OA development following standardized complete ACL/MCL injuries will vary directly with the degree of biomechanical abnormality between individuals. Three groups of sheep were used to test the hypothesis: 17 normal, 9 ACL/MCL transected, and 7 sham animals. Normal joints were assessed morphologically while sham and experimental animals had gait assessment pre- and at 4 and 20 weeks post-surgery, with cartilage and bone changes being mapped and graded at sacrifice at 20 weeks. Sham joints were morphologically normal and had only one minor kinematic change at 20 weeks. Although variable, ACL/MCL deficient animals showed significant kinematic abnormalities in 4/6 degrees of freedom (DOFs), as well as cartilage/bone damage by 20 weeks (p < 0.05). Linear regression analysis revealed that changes in medial-lateral (ML) translation were related to the current level of joint degradation as represented by total gross OA score (p = 0.0044, R(2) = 0.71) in the ACL/MCL transected group. Even identical ACL/MCL injuries result in inter-animal variations in instability and OA, however significant kinematic abnormalities in ML translation do relate to early OA in sheep.