The shoulder Flashcards
On which side is the labrum of the glenoid widest?
Lateral. Extends the surface area of the glenoid by 25-30%
What holds the biceps tendon in place in the intertubercular groove?
Transverse humeral retinaculum
Is the tendon of the biceps intra or extraarticular?
Intraarticular (craniomedial aspect is surrounded by joint capsule)
What shape is the medial glenohumeral (collateral) ligament of the shoulder?
Y-shaped
What are the rotator cuff muscles of the shoulders?
Supraspinatous, infrapinatous, teres minor (lateral), subscapularis, coracobrachialis (medial). Tendons are blended with the joint capsule
What are normal flexion and extension values of the shoulder in the dog and cat?
Dog: 57 degrees flexion, 165 extension
Cat: 32 degrees flexion, 164 extension
What are the passive mechanisms of shoulder joint stabilization?
Limited joint volume, adhesion/cohesion mechanisms, concavity compression, capsuloligamentous restraints
What are some diagnostics that can be performed in the work-up of shoulder disease?
Physical/orthopedic examination, arthrocentesis, radiography +/- contrast arthrography, CT, MRI, ultrasound (cannot identify medial soft tissue structures of the shoulder).
Are mineralizations of the tendon of origin of the biceps and tendon of the supraspinatous identified on CT always pathologic?
No - identified in 40% of non-lame patients.
What are the active mechanisms of shoulder joint stabilization?
Rotator cuff muscles
What soft tissue structures of the shoulder cannot be visualized on CT?
Teres minor muscle tendon and coracobrachialis muscle
What nerve needs to be protected during excision arthroplasty of the glenoid?
Suprascapular
What are potential fixation methods for shoulder arthrodesis?
Small dogs and cats: transarticular screw, K-wires.
Medium or large dogs: single or double plate fixation (locking plates [SOP, reconstruction, LCP] ideal).
Plating is preferred in all patients for stability.
What shoulder joint angle is ideal following arthrodesis?
105-110 degrees
How far should plating extend on the scapula and humerus during shoulder arthrodesis?
Distal half of the scapula to the proximal half of the humerus (4-5 screws in each bone).
What is the outcome for dogs undergoing shoulder arthrodesis?
Good to excellent. Mild circumduction may result if arthrodesis angles of >110 degrees.
What is the most common location of shoulder OCD?
Caudocentral or caudomedial humeral hdead
What percentage of dogs have bilateral shoulder OCD lesions?
27-68%
Large or giant breed male dogs are most frequently affected. Usually present between 4-8 months of age.
In what percentage of dogs with shoulder OCD is a non-mineralized cartilage flap trapped in the tendon sheath of the biceps brachii muscle?
10%. MRI or arthrography may be required to identify the lesion in these instances.
What is the treatment for OCD of the humeral head?
Debridement of the subchondral defect to bleeding subchondral bone using a bone curette or motorized shaver.
Edges of the defect should not be bevelled to decrease the risk of fibrillation and erosion of the cartilage on the corresponding surface of the glenoid.
Alternative to debridement is the use of OATS (osteochondral autograft transfer system).
What approaches to the shoulder can be performed for removal of OCD lesions?
- Arthroscopy
- Caudal (less loss of shoulder range-of-motion)
- Caudolateral (cranial retraction of the teres minor and infraspinatous, better protection of the axillary nerve).
- Craniolateral (tenotomy of the infraspinatous). Greater exposure of the caudal aspect of the humeral head but limits access to the caudal compartment.
What is glenoid dysplasia?
Hypoplasia or dysplasia of the glenoid resulting in a grossly abnormal articulation of the shoulder joint.
What age is glenoid dysplasia typically diagnosed?
3-10 months of age. History of no or mild trauma.
Affected animals typically hold the elbow flexed and in adduction with the distal limb abducted.
What is the recommended treatment for glenoid dysplasia?
Excision arthroplasty or arthrodesis