Ch 50 the shoulder

Question 1

anatomy

Answer 1

two-thirds of the motion the shoulder joint, and one-third the scapulothoracic synsarcosis

the tendon of origin of the biceps brachii muscle passes through the intertubercular groove, held in place by the transverse humeral retinaculum.
The joint capsule blends with tendons > “rotator cuff” muscles in human beings:
- medially: include the subscapularis and coracobrachialis
- laterlly: supraspinatus, infraspinatus, and teres minor

lateral and medial glenohumeral (collateral) ligament

Question 2

At what age do the glenoid and proximal humeral physes fuse?

Answer 2

Glenoid - by 6mo
Proximal humerus - by 12mo

Question 3

What is the ratio of glenoid to humeral head ratio?

Answer 3

1:2.5

the joint is moderately congruent

Question 4

What are the three zones of the labrum?

Answer 4

Transitional zone (collagen fibers in a fishnet-like pattern)
Circular fiber zone
Meniscal fold

The labrum is highly vascularised along the free margin and is loosely attached to the glenoid

Question 5

How thick is the hyaline cartilage of the shoulder joint?

Answer 5

approx 1mm in 20-25kg dogs

Question 6

What shape are the collateral ligaments of the shoulder?

Answer 6

Medial glenohumeral ligament is Y-shaped
Lateral glenohumeral ligament is a thick band

Question 7

What structure function to keep the tendon of the origin of the biceps brachii within the intertubercular groove?

Answer 7

Transverse humeral retinaculum

Question 8

What are the normal flexion and extension angles of the shoulder in the dog and cat?

Answer 8

Dog
- extension 165
- flexion 57

Cat
- extension 164
- flexion 32

Question 9

List the passive mechanisms of shoulder stability

Answer 9

Limited joint volume
Adhesion/cohesion mechanism
Concavity compression
Capsuloligamentous restraints (glenohumeral ligaments, joint capsule, labrum, and biceps brachii tendon origin)

Question 10

What are the main active stabilisers of the shoulder?

Answer 10

Supraspinatus
Infraspinatus
Teres minor
Subscapularis

And to a lesser extent:
- Biceps brachii
- Long head of the triceps
- Deltoideus
- Teres major

respond to stresses created by locomotion and weight bearing. Active mechanisms also improve joint stability and glenohumeral balance by enhancing glenoid concavity compression.

Question 11

What type of mechanoreceptors are within the collateral ligaments?
What is their function?

Answer 11

Type I, II and III mechanoreceptors
Type I (Ruffini) are the most common
Allow ligaments to work as sensory structures to actively contribute to shoulder stability via reflex arcs with the associated musculature

Question 12

immobilization of shoulder joint is entirely reversible, even when the period of immobilization is prolonged.

Question 13

diagnosis

Answer 13

phyiscal exam
begin with a thorough history of the lameness, including signalment
walk, palpation of the shoulder joint and associated musculature, joint range of motion and stability, and pain
neuro: CP deficits, atrophy, neck pain, reduced withdrawal
goniometry

diagnostic intra-articular anesthesia….?

arthrocentesis
valuable information for identifying immune-mediated and septic disease,

Rads
radiographic changes, even mild ones, are strong indicators of intra-articular disease. Osteoarthritis is rarely a primary disease of the shoulder joint
fractures, OCD, incomplete ossification of the caudal glenoid, chondrocalcinosis, glenoid dysplasia, and traumatic luxations
Stress (abduction) views may assist in the diagnosis of instability of the medial side of the shoulder joint, but the highly mobile nature of the normal shoulder joint warrants caution

Arthrography
outlining soft tissue structures and abnormalities of the shoulder joint, such as the tendon of origin of the biceps brachii muscle, osteochondritis dissecans flaps, medial joint stabilizers, intra-articular loose bodies, synovial neoplasms,

CT/MRI
CT and CT arthrography allow visualization of the peri- and intra-articular soft tissue structures except for the teres minor muscle tendon and coracobrachialis muscle

MRI allows identification of both intra-articular and extra-articular structures of the joint.

ultrasound
examination of the tendon also facilitates safe and efficient aspiration of surrounding synovial fluid and therapeutic injections.
The tendons of the supraspinatus, infraspinatus, and teres minor muscles and the caudal aspect of the humeral head can also be reliably imaged ultrasonographically.
limitation medial structures

Question 14

chondrocyte toxicity

documented of many commonly used local anesthetics in a wide range of species.

One publication suggested that a single intra-articular administration of bupivacaine, because of the drug’s rapid dilution and drop in intra-articular concentration, did not pose a significant risk for chondrocyte damage.

Several in vitro studies document protective effects of vitamin C, N-acetylcysteine, and hyaluronan on chondrocytes prior to exposure to local anesthetics.

Until more is definitively known about the effects of local anesthetics on canine and feline chondrocytes and the clinical utility and effectiveness of protective drugs, intra-articular instillation of local anesthetics should be used as a single administration, if at all

Question 15

What is the optimum concentration of iodine for arthrography when VT angiography is performed?

Answer 15

60mg/ml

Question 16

What percentage of shoulder pathology is extra-articular and therefore would be missed on arthroscopy?

Answer 16

15%

Question 17

mineralization within the tendon

Answer 17

mineralization within the tendon of origin of the biceps brachii muscle and tendon of the supraspinatus muscle

study
unilateral or bilateral thoracic limb lameness revealed that almost 40% of dogs identified by CT scan as having mineralization of periarticular soft tissue structures of the shoulder were not lame on the limb with periarticular mineralization.

Almost 90% of dogs with thoracic limb lameness and concurrent mineralization of periarticular soft tissue structures of the shoulder either had other documented shoulder pathology or had elbow disease.

Question 18

What is the recommended angle for excision arthroplasty of the glenoid?

Answer 18

excision arthroplasty is to form a “false” or fibrous joint between the humeral head and the scapular neck

• Distolateral to proximomedial osteotomy of the scapular neck
• Being careful to protect the suprascapular nerve

excision of humerus head not necessary

Question 19

What is the outcome of excisional arthroplasty?

Answer 19

Good-to-excellent in small dogs
Unknown in large breeds

Question 20

What angle of shoulder is aimed for in arthrodesis?
What landmark should be used for the rotation alignment?

Answer 20

105-110 degrees

The greater tubercle should be positioned craniodistal to the acromion and slightly medial in the sagittal plane

plate should extend from the distal half of the scapula to the proximal half of the humerus (typically at least four or five screws in each bone). The plate is contoured

In small dogs > large transarticular screw or diverging Kirschner wires
clinical outcomes are generally better when plates and screws are used for all sizes of dogs and cats.

Principles of arthrodesis (removal of articular cartilage and rigid fixation of the joint at a functional angle) are followed.

cancellous graft augmentation may not be as critical in the shoulder joint as in other joints because of the normally high cancellous bone content in the humeral head

Question 21

craniolateral approach.
The insertion of the trapezius muscle and the origin of the omotransversarius muscle are elevated from the cranial edge of the scapular spine as needed.

The incision is continued distally along the cranial border of the acromial head of the deltoideus muscle. The omobrachial vein (and cephalic vein, if necessary) is divided, and the incision follows the lateral aspect of the brachiocephalicus muscle to its insertion. The insertion of the superficial pectoral muscle is incised and the muscle elevated and retracted cranially.

Although osteotomies can be performed, tenotomy of deltoideus and supraspinatus tendons may result in fewer complications due to osteotomy nonunion

Answer 21

Elevation of the supraspinatus muscle, uprascapular nerve is identified, The lateral collateral ligament is transected and the joint capsule incised to allow luxation of the humeral head from the glenoid fossa.

A motorized burr is used to remove the articular cartilage from the surfaces of the humeral head and the glenoid fossa. stectomy of the distal tip of the glenoid and corresponding humeral head may be required to create an acceptable degree of contact between

thin bone of the scapula makes screw pull-out and construct failure more likely. Locking plate technology may therefore be preferred, however consider compression

Question 22

What is the reported outcome after shoulder arthrodesis?

Answer 22

Good-to-excellent
Normal or near-normal gait in 12 weeks

Question 23

What is the most common location of shoulder OCD?
How often is this disease bilateral?

Answer 23

caudocentral or caudomedial aspect of the humeral head, usually opposite the caudoventral rim of the glenoid
27-68% bilateral

Question 24

What percentage of OCD cases will have a nonmineralised cartilage flap trapped within the tendon sheath of the biceps?

Answer 24

Approx 10%

Question 25

What are the approach options of debridement of a shoulder OCD flap?

Answer 25

Caudal
- requires assistant for retraction
- results in less loss of RoM and improve weight bearing in first month

Caudolateral interdeltoideus approach
- Craniodorsal retraction of infraspinatus and teres minor
- Better protection og caudal circumflex humeral artery and axillary nerve

Craniolateral
- Included tenotomy of infraspinatus tendon
- Greater exposure of caudal aspect of humeral head but limits access to caudal joint pouch

modified cheli
articular access between the distal segment
of the supraspinatus muscle and the infraspinatus tendon. Cheli modification > forced hyperflexion.
caudal displacement of the acromial deltoid and infraspinatus muscles, further modified by Vezzoni to limited open approach without humeral head luxation

Question 26

a caudolateral approach
with craniodorsal retraction of the teres minor muscle (no tenotomy) has been shown to result in increased joint extension and range-of-motion compared with a craniolateral approach with tenotomy of the infraspinatus muscle, but there was less exposure to the articular surface compared with a craniolateral approach

Question 27

What is glenoid dysplasia?
What breeds are predisposed?
What does it cause?
What is the treatment?

Answer 27

Glenoid dysplasia is hypoplasia or aplasia of the glenoid resulting in grossly abnormal articulation
Toy breeds (Toy and Min poodle, Chihuahua, Pom, Sheltieetc)
Results in medial luxation of the shoulder
Tx: Arthrodesis or excision arthroplasty with an acceptable return to function

generally diagnosed in dogs between 3 and 10 months

Question 28

What is multiple epiphyseal dysplasia?
What is the treatment?

Answer 28

A rare defect in the ossification of the epiphyses of long bones, vertebrae, cuboidal bones and apophyses
Severe lameness, resembles bony changes seen with congenital hypothyroidism
Tx: euthanasia

Question 29

In what breed has focal humeral head dysplasia been reported?

Answer 29

Boerboel (Arthrodesis)