52. humerus

Question 1

what travels through the supracondylar foramen in a cat

Answer 1

branch of brachial artery and median nerve

Question 2

if cutaneous sensation is present in a dog with a humeral fracture and radial nerve neurapraxia how long will it regain motor function

Answer 2

1-6 weeks in most animals

Question 3

normal scapulohumeral abduction angle

Answer 3

30 degrees50 degrees is considered abN and likely to have medial instability

Question 4

humeral fracture location in dog vs cat

Answer 4

dog distal 44% and diaphyseal 42%cats diaphyseal 75%

Question 5

whole proximal humeral epiphysis fuses with metaphysis at what age in cat vs dog

Answer 5

dog 7.5 - 12 monthscat 19-26 months

Question 6

repair options for proximal humeral fractures

Answer 6

–two parallel pins (decr compression on growth plate and allow growth)–pins and tension band–lag screw

Question 7

what force is the greater tubercle susceptible to

Answer 7

tension or pull from supraspinatus muscle during swing phase of gait cycle

Question 8

T/Fthe proximal humeral metaphysis is an area of predisposition for primary bone tumors most commonly OSA

Answer 8

TRUE

Question 9

cats and dogs humeral IM pin purchase

Answer 9

dogs—use medial aspect of the humeral condyle to increase length of pin and bone purchasecats–aim for center diaphysis right above olecranon fossa

Question 10

percentage of pins placed nondirected retrograde that penetrate shoulder joint

Answer 10

20%recommend normograde placement (distal to proximal) to directed retrograde to the craniolateral surface to avoid joint placement

Question 11

tension side of humerus proximally and distally

Answer 11

proximal–craniolaterallydistally–caudomedially

Question 12

why is medial plate placement advantageous for fractures involving the distal third of the humerus

Answer 12

–tension side of bone–medial approach has less ST dissection–straighter shape of the medial epicondylar crest requires minimal plate contouringDISADVANTAGE–no access proximally, neuromuscular structures

Question 13

define supracondylar humeral fracture

Answer 13

fractures where the fracture line communicates with the supratrochlear foramen but NOT the joint/articular surfacetx: IM pins (Rush or cross), IM pin + plate, 2 plates (best results especially if comminuted), ESF with a full intercondylar pin (modified I)

Question 14

one humeral condyle—two ossification centersDescribe the fusion times

Answer 14

2 ossification centers fuse by 3 months condyle fuses with metaphysis 5-6 months

Question 15

most common side (medial or lateral) of humeral condylar fractures

Answer 15

LATERAL –smaller compared to medial with a smaller epicondylar crest–lies lateral to bone axis and receives the majority of weight bearing through the radial headoccurs less often in cats due to absence of a supratrochlear foramen and sizes are approx equal wider and strongerBREED: FRENCH BULLDOGS

Question 16

lateral condylar fractures in young dogs

Answer 16

peak 4 months age—SH IV(in older dogs consider IOHC)medial aspect of the condyle will palpate DISTALLYrepair–lag screw + antirotational pin, 2 lag screws, lag screw and plate, ESF (modified I), K wires alone in dogs < 4 kg, self compressing pinscan be done closed with fluoroscopic guidance can use cannulated screws

Question 17

growth plate damage following SH IV fracture

Answer 17

NO decrease in humeral length even with implants across growth plate (may even increase growth–Lefebrve study)do NOT need to remove implantsdistal growth plate is only responsible for 20% growth and closes earlier than proximal growth plate (5-8 months)

Question 18

use of a metal washer with transcondylar screw

Answer 18

distributes forces more evenly

Question 19

complications associated with repair of lateral condylar fractures

Answer 19

increase surgery time, increased risk complicationsevery 30 min increased complication risk doubledpresence of intracondylar gap post op associated with risk of implant failure (shear stresses)

Question 20

approach for a T-Y (intracondylar) fracture

Answer 20

medial and lateral approach +/- osteotomy of olecranon +/- triceps tenotomy (YOUNG DOGS)complications of olecranon osteotomy >37%1. fix condylar portion first, then attach to diaphysis2. fix medial part of humeral condyle then lateral approach for transcondylar screw and stabilization of lateral aspect of condyle

Question 21

complications follow T-Y fracture repair are most often seen…..

Answer 21

medial aspect–inaccurate repairleads to varus deformity

Question 22

incomplete ossification of the humeral condyle

Answer 22

medial and lateral ossification center should fuse by 3 months ageif fusion is incomplete–fibrous band and weakened area remainsUK—ESS; US—Cockeroften bilateral

Question 23

radiographic views to diagnose IOHC

Answer 23

standard CrCd and flexed lateral views of the elbow15 degree craniomedial to caudolateral OBLIQUEother imaging: CT (SP/SN), scintigraphy (not SP)

Question 24

Marcellin-Little et al reported what finding with conservative treatment of IOHC after diagnosis

Answer 24

43% with partial radiolucent line and 8% with complete radiolucent line fractured within 11 days to 18 months after diagnosisprophy repair–LARGE transcondylar screw (positional vs lag) +/- transcondylar bone tunnels for vascular growth +/- cancellous graft +/- lateral epicondylar plate

Question 25

T/Fprognosis with traumatic fracture secondary to IOHC is more guarded than true traumatic humeral condylar fracture

Answer 25

TRUEIOHC has more nonunion after repairinfection, seroma common complicationsimplant failure, loss of reduction, nonunion

Question 26

T/Foutcome of dogs following condylar fracture repair, all show radiographic OA progression but did NOT correlate with force plate gait analysis or fracture reduction

Answer 26

TRUEoutcome of dogs following condylar fracture repair, all show radiographic OA progression but did NOT correlate with force plate gait analysis or fracture reduction