Equine Forelimb

Overview of Angular Limb Deformities and Associated Procedures

  • Discuss a surgical procedure utilized in equine surgery for the treatment of angular limb deformities, referred to as periosteal stripping.

  • Mention the objective of the surgery: inhibit bone growth on one side of the affected bone using surgical wire or a screw to allow the slower growing bone to catch up with the faster growing side.

Brachial Plexus and Muscle Innervation

  • Overview of the brachial plexus as the network supplying all forelimb muscles.

  • Key muscles supplied by the brachial plexus:

    • Supraspinatus

    • Infraspinatus

    • Subscapularis

    • Gluteus

    • Biceps

    • Triceps

    • Extensor carpi radialis

    • Common digital extensor

  • Muscles on the flexor side include the deep and superficial digital flexors.

Clinical Signs of Nerve Injury

  • The first clinical sign of nerve issues in muscle supply is lameness.

  • Over time, muscle weakness and atrophy are observed, highlighting the connection between nerve damage and muscle tone.

  • Example of nerve injury:

    • Brachial plexus avulsion can lead to loss of function in affected muscles of the forelimb.

Trauma in Racehorses

  • Discussion of common injuries in racehorses, particularly due to competition and handling.

  • Horses often exhibit signs of stress due to the competitive environment, leading to gastrointestinal issues (e.g., ulcers).

  • Emphasis on the risk of shoulder injuries from metal gates during races, particularly affecting the supraspinatus nerve.

Muscle Atrophy Due to Nerve Damage

  • When nerves such as the supraspinatus are injured, muscle atrophy will occur in both the supraspinatus and infraspinatus muscles.

  • Sign of atrophy includes prominence of the scapular spine.

  • Injury to the axillary nerve affects the deltoid and brachiocephalicus muscles, causing significant muscle atrophy.

Important Terms for Clinical Assessments

  • Key words to remember for NAVLE questions:

    • Lameness (common in all cases)

    • Timeframe for muscle atrophy following nerve injury is critical.

Radial Nerve Paralysis

  • Key clinical signs of radial nerve paralysis include atrophy of the triceps and extensor muscles as well as elbow dropping due to loss of extensor muscle function.

Bursa and Bursitis

  • Bursas are locations for synovial fluid accumulation to reduce friction during intense muscle/limb movement.

  • Olecranon bursa and bicipital bursa are notable for potential infection leading to bursitis.

  • Infections occur through skin barrier breaches, allowing opportunistic bacteria to invade.

Treatment for Bursitis

  • Treatment involves injection of antibiotics and proper drainage of pus or inflammatory fluid, with care taken to mitigate irritation post-procedure (e.g., using shoes to prevent rubbing).

Passive Stay Apparatus

  • Defined as a collection of tendons, ligaments, and muscles enabling horses to support their weight while standing, reducing joint fatigue.

  • Each joint has specific structures preventing over-flexion or over-extension:

    • Shoulder joint: tendon of the biceps

    • Elbow joint: collateral ligaments

    • Carpus: flat surfaces of adjacent bones support stability and prevent overextension.

Flexor Muscles and Tendons

  • Discussion of the flexor muscles:

    • Common digital extensor: key tendon reaching P3 (coffin bone) from dorsal aspect.

    • Extensor carpi radialis: serves as landmark for carpal joint injections and anatomical procedures.

  • Deep and superficial digital flexors: functionality includes flexing the digit and providing structural support through accessory check ligaments.

Angular Limb Deformities Treatment

  • Overview of how check ligaments (proximal and distal) aid in treating angular limb deformities like varus and valgus deformities.

  • Procedures like periosteal stripping may be combined with measures to address contracted tendons (club foot).

The Carpus Joint and Associated Structures

  • Carpus consists of three distinct joints: radiocarpal, intercarpal, and carpal metacarpal.

  • Anatomical features include articulation between the distal radius and proximal row of carpal bones (radial, intermediate, ulnar, and accessory).

  • Discussion of passive stay apparatus functions in the carpal region.

Synovial Fluid Characteristics

  • Synovial fluid is essential for joint lubrication. Quality is judged by viscosity according to the ‘string test’.

  • In conditions like carpal cysts and carpal fractures, fluid dynamics change, so appropriate interventions are vital for treatment.

Navicular Disease and Associated Diagnostics

  • Definition and diagnosed pathologies (e.g., navicular bursitis).

  • Diagnostic technique includes hoof testing, noting lameness during locomotion, and imaging for fractures or necrosis features.

  • Identify key signals in navicular disease management, emphasizing the importance of early diagnosis and treatment protocols (e.g., nerve blocks, synovial fluid analysis).

Laminitis and Its Pathophysiology

  • Detailed description of laminitis, its stages, and anatomical implications on the hoof.

  • Distinction between founder (early laminitis) and rotation (advanced laminitis) stages, with emphasis on the consequences of vascular insults leading to inflammation and tissue separation in the lamina.

  • Consequences of untreated laminitis include significant pain and potential loss of hoof integrity.

  • Importance of careful monitoring and intervention strategies for horses prone to laminitis.

Conclusion

  • Recap of important anatomical structures, nerve innervations, treatment modalities, and disease mechanisms affecting equine health.

  • Need for comprehensive understanding of equine anatomy, physiology, and appropriate clinical interventions in managing equine injuries and diseases.