Humerus, Shoulder & Scapula

Question 1

Sites of humeral stress fractures

Answer 1

1. Proximal - caudal aspect of the neck
2. Distal - Craniodistomedial - medial supracondylar region
3. Mid-shaft - Medial diaphyseal - close to teres major tuberosity (on the medial aspect of the limb, teres minor on the lateral aspect distal to the humeral neck and proximal to deltoid tuberosity)
4. Cranioproximal and caudodistal fractures are less common

Bilateral stress fractures are common. Happen usually within the first 60-90 days of resumption of training following a layup period

Question 2

Radiographic projection that best highlights deltoid tuberosity fractures

Answer 2

Caudomedial craniolateral oblique

The deltoid tuberosity is located on the craniolateral aspect of the humerus.

Question 3

What did Frei et al (2017 VCOT) conclude about optimal plate positioning for SGT fractures

Answer 3

1. Recommend that the plate be slightly over-bent (at the passage over the nerve) and placed cranial to the scapular spine
2. The cranial scapula cortex is thicker than the caudal cortex at most levels proximal to the SGT, ∴ the more ideal location for a plate
3. It is also easiest to avoid the SS nerve at the most cranial aspect of the scapula, where it has not yet ramified - LCPs protect the periosteal blood supply as there is only limited contact and pressure on the bone is reduced; however this may be insufficient as the suprascapular nerve embedded in the connective tissue is rather prominent and extensive. Precise over-bending of the plate at the nerve passage site may be needed to prevent its damage
4. Cranial aspect is the tension surface so represents another advantage of plating here
5. SS nerve averages 2cm distal to the scapular spine
6. Although the bone density of distal scapula significantly lower cranially than caudally, may account for implant failure in prev reports

Question 4

Which 2 tendons origonate at the supraglenoid tubercle of the scapula

Answer 4

Biceps brachii

Corachobrachialis

Question 5

Treatment options for supraglenoid tubercle fractures

(list)

Answer 5

1. Conservative management
2. Resection of the fracture fragment - should only be attempted in cases with articular fractures involving <30% of the articular surface of the scapula and comminuted fractures. W removal of smaller SGT fractures, full restoration of function can be achieved
3. Lag screw fixation +/- addition of wire tension band: (2-3, 5.5mm cortex screws inserted in lag fashion in combination with a figure-of-8 tension band may lead to a successful functional result). May not require the tension band part if the biceps tendon is transected
4. LCP fixation in horizontal cranial orientation (Frei 2017 VCOT)
5. Fixation w human femoral LCP (Frei 2016 VCOT)

BICEPS TENOTOMY may or may not be combined with repair to decr. the distractive forces on the fracture fragment (origin of biceps brachii)

Question 6

Physes associated with the shoulder joint

Answer 6

1. Humeral head and lesser tubercle
2. Greater tubercle

( Lesser tubercle can appear as distinct incompletely ossified area see diagram)

3. Supraglenoid tubercle
4. Small ossification centre for the cranial part of the glenoid

Question 7

Which plate position using the human distal femoral LCP was most successful for fixation of supraglenoid tubercle fractures?

Answer 7

Plate positioned cranial to the scapula spine, overbent at the site it runs over the suprascapular nerve lead to the best outcome - minimal transient supra/infraspinatus atrophy, no joint instability and long term soundness without implant removal

Other positions were caudal to the spine and cranial to the spine under the SS nerve. Both resulting in atrophy, instability and necessity for plate removal.

Question 8

Ideal angle of fixation for shoulder arthrodesis in Shetlands (Kadic 2020 EVE)

Answer 8

110°

NB fetlock arthrodesis angle approx 170°