Ch 51 fractures of the humerus Flashcards
A large number of animals with a fractured humerus have concurrent thoracic, abdominal, or skull injuries
Anatomy
- S-shaped bone with a twist, and ridges proximally and distally
- The radial nerve > distolateral aspect, deep to the lateral head of the triceps brachii + alongside the brachialis muscle (innervate the digital and carpal extensor muscles and the extensor carpi ulnaris)
- median and ulnar nerves > medial aspect.
- medullary canal tapers and effectively ends far proximal to the distal aspect of the bone
- tendon of origin of the biceps brachii muscle runs in the intertubercular groove and is held in place by the transverse humeral retinaculum.
- distal end of the humerus is referred to as the humeral condyle > trochlear and capitulum
- lateral and medial collateral ligaments attach to the lateral and medial epicondyles
- supratrochlear foramen is closed off in life by a membrane
- in cat, true supratrochlear foramen is absent
What is the tricipital line?
What is the deltoid tuberosity?
- Tricipital line: A bony ridge extending from the humeral head cranially and distally toward the deltoid tuberosity. Origin of the lateral head of the triceps. Bone cranial and proximal is generally cancellous
- Deltoid tuberosity: The insertion point for the deltoideus muscle
What is anatomically unique about the feline humerus in comparison to the canine?
Supracondylar foramen through which the brachial artery and median nere run
What are the two sides of the humeral condyle called?
Medial: the trochlea - articulates with the trochlear notch of the ulna
Lateral: The capitulum - smaller, articulates with the radial head
examination findings
carry the leg with the affected elbow dropped and with the paw resting on its dorsal surface > mimics the appearance of loss of proprioception resulting from nerve injury
Horner’s syndrome or loss of the panniculus reflex together with neurologic deficits > brachial plexus injury.
Mediolateral and craniocaudal or caudocranial radiographs should be taken of both humeri
> limb pulled caudally and slightly laterally to avoid a foreshortened image or horizontal beam view
temporary immobilization before surgery
analgesia
How can you best assess nerve function in a humeral fracture?
toe pinch and skin prick
If cutaneous sensation is present, will usually regain motor function in 1-6wk
What percentage of fractures of the humerus are proximal, diaphyseal, supracondylar and condylar in cats and dogs?
When does the proximal humeral physis fuse with the metaphysis?
most common # proximal humerus is the physis in immature
Dog: 7.5 - 12m
Cat: 19 - 26m
At what angle doe the humeral head and the greater tubercle fuse?
102 degrees
which salter harris # common proximal humerus
Salter-Harris type I and II
Salter-Harris type V or VI fractures can also affect the proximal physis.
may result in premature closure and shortening of the bone or bowing if closure is asymmetric.
What are some potential underlying disease processes of a proximal metaphyseal fracture?
- Nutritional secondary hyperparathyroidism
- Neoplasia OSA
- Iatrogenic fracture for harvesting cancellous autograft > usually spiral fractures that extend distally
what approach to proximal humerus?
fractures of the proximal humeral physis are exposed via a combined approach to the craniolateral region of the shoulder joint and the proximal part of the humerus
What are the fixation options of a proximal physeal fracture if the physis is complete?
in young animals > preferable to place the Kirschner wires in a parallel manner so as to minimize compression of the growth plate and allow for continued physeal growth.
What are the fixation options of a proximal physeal fracture if the physis has split between the humeral head and the greater tubercle??
Sx approach to humerus diaphysis
technically demanding because of important neurovascular structures on the lateral and medial aspects
craniolateral
combined with the approach to the proximal will expose the proximal three-fourths of the humerus
> The radial nerve with the brachialis muscle can be reflected
medial
involves cutting the pectoral muscle origins proximally
> Great care must be taken to identify the median and ulnar nerves
cranial lateral approach to humerus
medial approach to humerus
humerus # fixation methods
choice is dictated by:
type of fracture
the patient’s age
the nature and size of the animal
the surgeon’s experience
implants available
expense
AIM: Optimizing the number of implants in small fracture fragments and achieving a stable fracture repair
biologic strategy of stabilizing the proximal and distal fragments, maintaining limb and joint alignment, and not interfering with the blood supply to the fragments can be adopted.
Where should an IM pin be aimed towards in a dog?
What is the recommended size?
normograde > Aimed towards or inserted into the medial aspect of the humeral condyle to increase bone purchase and length
pin diameter > 36 - 45% of the medullary canal diameter observed from a lateral radiograph, measured at the 80th percentile of humeral length
+ intramedullary pin + cerclage: long oblique and simple, Cerclage used with caution because the tapered shape
+ ESF: prevent rotation or collapse for simple transverse or comminuted fractures
+ plate: comminuted fracture
plate-rod (Reems et al) successful in 46/47 cases.
> recommended using a pin 35% to 50% of the diameter of the medullary canal
inability of pin to resist rotation, shear, and axial compression
What percentage of nondirected retrograde IM pins penetrate the shoulder?
normograde or retrograde pin directed craniolaterally acceptable
20%
study compare directed retrograde, nondirected retrograde, or normograde
humerus # fixation
intramedullary pin in cats
medial epicondylar crest is rarely wide enough
- direct the pin into the central area the diaphysis just proximal to the olecranon fossa
- restricted to fractures of the proximal half of the diaphysis because anchorage of the pin is not firm
- Normograde insertion of pins, in a distal-to-proximal direction
proximal normograde insertion, the pin is usually started from the craniolateral aspect of the greater tubercle
For fractures involving the mid- or proximal diaphysis, the pin is driven distally to a point just proximal to the supratrochlear foramen.
For retrograde insertion or proximal/mid #, the pin is placed into the proximal segment from the fracture site
cadaveric studies > retrograde pin placement for fractures of the distal part NOT be recommended, in either dogs or cats, due to the potential for damage
complication IM pin
fractured humerus
pin loosening
breakage
Complications usually occur as a direct result of fracture instability
Interlocking Nailing for Fractures of the Humerus
apering shape of the humerus does not readily lend itself to interlocking nail fixation
distal aspect of the bone,6 so there is often only room for placement of one locking device
Suitable fractures for interlocking nail fixation are mid-diaphyseal, with sufficient bone on each side of the fracture
at least one bone diameter away from the fracture line
ILN complicatons
Complications
fracture collapse,
osteomyelitis,
screw missing the nail hole,
radial neuropraxia
changes include the use of bolts rather than screw will change rate of these coplications
What are the most common ESF configurations for the humerus?
esf will will prevent rotation, shear, and axial compression
Type I
Modified type I/II
ESF tied into IM pin
Usually placed on craniolateral surface
IM pin can be placed first to aid bone alignment + prevent fragment rotation + resistance to bending
particularly where bone stock is limited proximal and distal
ESF
humerus does not have a safe corridor for pin insertion; therefore, hazardous corridors are identified as the safest areas
supracondylar region > the radial nerve, in cats supracondylar foramen
ESf + IM pin
able to resist bending, shear, torsion, and compression at the fracture site.
increase frame stability, and when the distal fragment is short, a centrally threaded, positive profile pin is placed as a full transcondylar pin
may be advantageous to increase frame stiffness in large dogs
transcondylar pin
dogs
aimed from craniodistal to the lateral epicondyle to exit the bone medially at a similar point halfway between the epicondyle and the articular surface
cats
similar, but the pin should be aimed from a position slightly cranial to the lateral epicondyle
2.0 mm or 1.6 mm diameter pin
What is the tension surface of the humerus?
Craniolateral surface proximally
Caudomedial surface distally
On which side of the humeral condyle is plate application easier?
Medial - straighter epicondylar crest
Bone Plates and Screws for Fractures of the Humerus
plates positioned:
- craniolaterally for fractures of the proximal and middle
- medially for distal diaphyseal, supracondylar, and intracondylar fractures (less tissue dissection, straighter and better for cats vs need for careful dissection to preserve neurovascular)
lateral surface of the distal half of the humerus:
- marked curvature
- close to the radial nerve and brachialis muscle
- Penrose drain around the muscle and nerve
- Curved plates designed for use on the distal aspect
What is a supracondylar fracture?
What are the repair options?
A fracture which communicates with the supracondylar foramen but not with the articular surface
Repair options:
- Cross pins or Rush pinning (immature)
- Unilateral or bilateral plate for comminuted (adult)
- ESF - modified type I/II
require rigid stabilization because close proximity to elbow joint
humerus condylar # repair
Anatomic reduction is usually achieved by open reduction
> vs closed reduction with fluoroscopic guidance and minimally invasive surgery
> transcondylar screw in lag fashion, with or without an antirotational pin, screw, or bone plate and screws
> (self-compressing pins and a positional transcondylar screw)
lateral approach to the humeral condyle and epicondyle
lateral approach to the humeroulnar part of the elbow joint
Intracondylar (T-Y) Fractures
fracture of the supracondylar region extends to articular surface.
osteotomy of the olecranon or tenotomy
- the articular surface is first realigned using a transcondylar screw, then attached to the humeral diaphysis
medial and lateral approach
- medial part is stabilized to the diaphysis with a bone plate and screws
- lateral part of the humeral condyle is stabilized with a screw in lag fashion and lateral bone plate and screws
- medial the plate is positioned on the caudomedial aspect + screws angled in craniolateral direction
- ensure that the screws do not penetrate the olecranon fossa or articular surface
- lateral plate positioned on the caudal aspect
Incomplete Fissure of the Humeral Condyle or Humeral intracondylar fissure (HIF)
- ossification centers fail to fuse, and condyles remain separated by the fibrous band
More recently, this theory was challenged by a study that reported the development of a fissure in Spaniel that 2 years previously had a completely normal elbow CT > support a previously noted hypothesis that stress fracturing may be involved - normal physiologic forces produce micro-movement, causes persistent thoracic limb lameness
- predisposes to fracture
- Spaniels appear to be the most predisposed breed, lab/pointer/GSD
- often bilateral
- pathogenesis of this condition is unclear: metabolic disease, a form of elbow dysplasia related to conformation, intense activity resulting in stress fracture
- may be heritable with a recessive mode of inheritance
- Histology: atrophic nonunion fracture with cancellous bone and osteosclerosis, no evidence of persistent cartilage
Humero-anconeal elbow incongruity in spaniel breed dogs with humeral intracondylar fissure: Arthroscopic findings
Danielski 2022
Controlled clinical study.
Animals: Dogs with HIF (14 dogs, 21 elbows) and dogs without HIF (20 dogs)
cartilage lesion on the caudal humeral condyle of dogs with HIF. The lesion was found in all dogs with HIF but in no dogs without HIF.
Clinical significance: Humero-anconeal incongruity and an associated cartilage
lesion appear to be present in dogs with HIF. We propose that this lesion
may be associated with humero-anconeal incongruity.
The modification of the previously reported arthroscope portal to a caudo-medial:
- allowed the inspection of all major intra-articular structures of the medial elbow joint
compartment and partially of the lateral
- allowed the caudal aspect of the humeral condyle to be inspected
Medial epicondylar fissure fracture as a complication of transcondylar screw placement for the treatment of
humeral intracondylar fissure
Jenkins 2022
Retrospective study.
Sample population: Seventy-four client-owned dogs (88 elbows)
incidence of medial epicondylar fissure fracture (MEFF) after medial-to-lateral transcondylar screw placement in dogs with
humeral intracondylar fissure
identified in 10 elbows (11.4%)
MEFF tended to increase the risk of perioperative screw loosening (P = .06).
Clinical significance: Placing transcondylar screws with a diameter inferior
to 41% of the height of the condyle is recommended to avoid MEFF.
amount of torque applied while
tightening the screw.
Medial epicondylar fissure fracture appears to have a low clinical significance
Arthroscopic treatment of medial coronoid process disease was performed prior to transcondylar screw placement in 25% of elbows (n = 22
Overall, complications were documented in 24.9% of elbows (15% major and 9.9% minor).
The effect of an aiming device on the accuracy of humeral
transcondylar screw placement
Neal 2023
evaluate the accuracy of an aiming device on placement of humeral transcondylar screws compared to fluoroscopic kwire/cannulated methods
Study design: Randomized, match pair, prospective ex-vivo study.
Sample population: A total of 68 dogs.
The risk of joint involvement was 8 times greater in aiming device groups, though not significant (p = .0575). aiming device used, only 7 had joint involvement (10%),
compared to 1/68 (1.5%) legs using fluoroscopic
Significant complications included increased drill attempts in fluoroscopic groups (p = .0237).
more accurate with the aiming device
whenever a right thoracic limb was being operated on. This is most likely a consequence of both surgeons being right-hand dominant.
The aiming device provided accurate placement of transcondylar
screws, in terms of both position on the condyle and trajectory angle. Results
were similar to fluoroscopic-guided method.
Limiting the screw trajectory angle is
important for eliminating the risk of intracondylar fracture gap formation and limiting repair failure
Use of an extended CT scale reconstruction to diagnosemetal implant failure in a canine elbow
Labrador 2021
VRU
Presumed concurrent medial coronoid process fracture is a frequent radiographic finding in dogs and cats
with humeral condylar fractures
Pierrot 2023
observational radiographic retrospective study, particular attention should be taken when evaluating cases of humeral condylar fractures for a potential associated fractured medial coronoid process, even more so in comminuted fractures
Adjunctive fixation of the humeral epicondyle in a lateral condylar fracture model: Ex vivo comparison of pins and
plates with a novel composite (AdhFix)
Quinn 2024
Study design: Cadaveric biomechanical assessment, 9
4.5 mm cortical screw placed in lag fashion. Adjunct fixations, axially loaded to failure and construct stiffness, yield load
yield load was significantly higher for AdhFix
group compared to the pin group, p = .016. No statistical significance was seen in
the comparison between AdhFix group and the plate group
may be a viable alternative
for adjunct fixation of humeral condylar fractures, a technique that circumvents
plate contouring
high energy visible light-cured fixator plate
A humeral intracondylar repair system for the management of humeral intracondylar fissure and humeral condylar fracture
Walton 2020
Retrospective review
There was one major surgical complication and one major medical complication out of 34 fissure cases, and two major surgical and one major medical complication out of 14 fractures (implant losening, infection)
drill bit creates a 5.9 mm diameter void around the screw, at the fissure, allowing the void to be packed with graft
we report at least partial healing in all cases with CT follow-up, with the fissure accounting for <50% of the cross-sectional area of the
condyle in 15 of 17 cases.
post-op infection 21-30% (not all receieve post-op abs)
Accuracy of three-dimensional printed patient-specific drill
guides for treatment of canine humeral intracondylar
fissure
Easter 2020
Retrospective consecutive case series.
Animals: 11 Client-owned dogs with HIF treated with a 5-mm transcondylar
screw (TCS) placed from medial to lateral with a 3D-PDG
There was no intra-articular
screw placement.
Conclusion: Use of a 3D-PDG permitted accurate placement of a mediolateral
5-mm locking TCS within the humeral condyle
Fluoroscopic guidance and aiming devices have previously been used to improve accuracy of screw placement.
6,10,11 Fluoroscopy units are not widely available, and fluoroscopy-assisted screw placement is highly operator dependent, requires multiple exposures, and exposes
theatre staff to repeated doses of ionizing radiation; it can also be time consuming. Commercial drill guides can be challenging to position and may slip during drilling.
invasive to fit guide on
canine humeral
anatomic plating system (CHAPS) for humeral condylar
fracture repair in spaniels
Neil J. Burton
