Ch 54 radius and ulna Flashcards
What percentage of weight at the elbow is transmitted through the radius and the ulna?
Radius 51%
Ulna 49%
Anatomy
The tendons of which muscle insert on the medial side of the radius and ulna?
Biceps brachii
Bracialis
What muscles share their origin with both the radius and the ulna in the mid-diaphysis?
Pronator quadratus
Deep digital flexor
Abductor pollicus longus
cranial muscles
What is the radioulnar ligament?
Proximal extension of the antebrachiocarpal joint capsule between the radius and ulna. Attaches proximally to the interosseus ligament
How much of the growth below the elbow is the distal ulna physis responsible for?
Proximal radial physis?
Distal ulnar physis 100%
Proximal radial physis 30-50%
What age do the physes of the antebrachium close?
222-250d (in Beagles)
aLDRA, Anatomic lateral distal radial angle; aMPRA, anatomic medial proximal radial angle.
What is the mean radial procurvatum of Labs?
26.6 degrees
(range, 14 to 39 degrees)
conformation of normal chondrodystrophic dogs possesses values far outside the ranges established
How do you calculate procurvatum?
On sagittal view:
Procurvatum = CORA magnitude + (90-aCdPRA) + (90-aCdDRA)
radius procurvatum
what is considered “normal” for any individual within these breeds, and at what point the characteristic conformation seen becomes pathologic in the sense of resulting pain and disability, is unknown
radial shortening
- compensatory increase in growth at the proximal radius falls short of maintaining appropriate radial length
- radius subsequently shortens > humeroradial and humeroulnar subluxation occur.
- With increasing space, the humeral condyle becomes cranially displaced, putting pressure on the coronoid processes of the ulna
- premature closure of the proximal radial physis can also result in overall radial shortening
What is the sensitivity and specificity of rads for diagnosing radioulnar incongruity?
Sensitivity 78%
Specificity 86%
Radial shortening needed to be between 1.5-4mm for a 90% sensitivty
What is the sensitivty and specificity of arthroscopy for diagnosing radioulnar incongruity?
Sensitivity 94%
Specificity 81.9%
What it he sensitivity, specificity and interobserver agreement for radioulnar incongruency on 3D printed models with a 1mm incongruence
Sensitivity 82%
Specificity 100%
Interobservor agreement 87%
Radial shortening Tx
goal: reestablish radioulnar congruency at the elbow + bone alignment.
- depending on the severity of the condition and the age
- young animals may outgrow the correctional measures
- Elbow joint congruence > either by lengthening the radius or by shortening the ulna
- can be completed acutely or gradually
- gradual > radius should cease its migration when the articular cartilage contacts the humeral capitulum
- in immature > gradual/dynamic best
- in skeletally mature dogs > any of gradual dynamic lengthening procedures (for stretching the soft tissues joining the two bones) OR one-stage radial elongations
- for acute: confirm radial head position requires radiography or, optimally, arthroscopy
What are the Tx options for radial lengthening? (4)
.1. Distraction osteogenesis
- advantages in the young animal, allow some adjustability to adapt to continued growth.
- Semi-controlled, gradual elongation: transverse osteotomy of the proximal radius and the placement of separate pins and radius and humerus with elastic material
- main advantage> little risk that the radial head will reposition too far proximally
- controlled: circular ESF, disadvantage is radial head position is under the direction of the surgeon
.2. Transverse osteotomy and acute correction
- use of bone spreaders for distraction, stabilization with plate or ESF
- large bone gap > lack of load sharing with the implant > consider cortical bone graft
.3. Sagittal sliding osteotomy (acute correction)
- preserving load sharing
- lag screw with neutral plate
.4. ulnar ostectomy above interosseous ligament
- shorten under the progressive use of the limb and the weight of the animal
- with an IM pin> dynamic + gradual shortening
- acutely shortened with hemicerclage
- recommended for mature animals.
- in puppies, the risk ostectomy gap may heal before
How much radial lengthening has been reported with the use of an ESF and distraction osteogenesis?
Up to 50% of the original radial length
ulna shortening
- geometric configuration of the distal growth plate is the primary reason why affected
- Most physes are relatively flat > predispose to shear fractures
- physis of the ulna is conical in shape and thus is unable to shear
- force from any direction can cause compression > injury to the germinal cells
- heritability of premature ulnar physeal closure as related to conformational development of specific breeds
- ulna shortening can affect radius growth too
- can cause humeroulnar incongruity (alter trochlear notch) excessive biomechanical loads on radial head and anconeal process > OA
What percentage off physeal insults is made up of distal ulnar physeal injury?
63%
What are the typical changes in the radius secondary to premature closure of the distal ulnar physis?
PTSDv
Procurvatum
Torsion
Shortening
Distal valgus
What are the surgical options for ulnar lengthening? (5)
(immature or mature)
Dynamic ulnar ostectomy/osteotomy
Distal ulnar ostectomy
ESF and distraction osteogenesis
(mature)
Distracted osteotomy and plating
Sagittal sliding osteotomy
proximal ulna guided in semi-controlled or controlled, dynamic or static
dynamic ulnar ostectomy
semi-controlled woth IM pin
- skeletally immature patients, treatment of choice.
- frees the proximal ulna, so it is no longer constrained by retarded growth of the distal physis, move proximally and optimize congruency with the humerus.
- goal is to allow unrestricted longitudinal bone growth of the radius, may prevent worsening of radial angulation if growth potential still reside
- In the immature, ostectomy is preferable > larger gap will help prevent osseous union before cessation of radial growth
- mature dog, “osteotomy” because premature union is less of a concern
- ostectomy just distal to the coronoid processes (semi-controlled), contraction of the triceps brachii muscle group exerts a traction force
- Placement of Hohmann retractors around the ulna will isolate the ulna and protect the radius > sawing may be ceased, completed with osteotome
complications: - pulling force of the triceps not perfectly axial but an angle, exerting a bending moment at ostectomy
- bending/caudal displacement causes an iatrogenic recurvatum deformity (methods to counteract: IM pin, oblique ostectomy but wont work if large gap)
- accidentally score the radius, result in a synostosing callus between the two bones.
- Instability > formation of an exuberant callus > syostosis or irritate soft tisssue caudal ulna
- pin migration
- irritation of triceps brachii muscle
- pin failure
What can done to aid in stability of a proximal dynamic ulnar osteotomy/ostectomy? (2)
to prevent bending moment
Oblique cut (proximocaudal to craniodistal)
IM pin (in immature)
revision sx: graft + plate
method used to avoid instability and recurvatum of the ostectomized ulna
ostectomy of the distal part of the ulnar diaphysis or removal of the distal physis itself
- interosseous ligament to help stabilize
- unknown is the comparative efficacy of low versus high dynamic ulnar ostectomies in the skeletally immature dog in reestablishing humeroulnar congruence
- in vitro: distal to the interosseous ligament did not allow adequate movement of the ulna in one study
What methods can reduce the chances of permature healing of the ulna ostectomy? (3)
goal: unrestricted longitudinal bone growth of the radius
- Ostectomy gap greater than 1.5x diameter of the bone (Key’s hypothesis)
- Removal of all periosteum in the vicinity
- Insertion of free fat graft into ostectomy
What is the Heuter-Volkmann law (aka Delpech’s law)?
Physeal growth is slowed by excessive compression and is accelerated by distraction
Developmental antebrachial angulation
(1) asymmetric premature closure of the proximal or distal physis of the radius or both
(2) premature closure of the distal physis of the ulna with continued radial development
(3) a combination of the two
- decisions regarding timing and the type of correction to be completed
- skeletally immature risk: correction before development ceases is that the angulation can return
- delay surgery until mature risk: angulation will negatively affect biomechanical loads at joints, creating stress + OA
- success rate of ulnar ostectomy as the sole treatment for premature ulna closure of juvenile dogs is relatively unknown
- reestablishing normal antebrachial bone and joint alignment, or resolution of lameness, not prospectively studied
- PUO utility as the sole corrective procedure limited to mild radial changes
- > > radial corrective measures are often necessary
- likely that distal radial physis also damaged, resulting in more complex deformity
Antebrachial Angular Limb Deformity Surgical Planning
presurgical planning called the center of rotation of angulation (CORA) method
goal of this technique is to determine the apex of the deformity or deformities (also referred to as CORAs) using the radial anatomic or mechanical axis in conjunction with the joint orientation angles
1. normal contralateral antebrachium agles used or mean joint orientation angles (bilateral dz)
2. frontal plane joint orientation lines
3. frontal plane radial anatomic axes
4. Determine where the anatomic axes intersect within the cortical confines of the bone > CORA
5. repreat in sagital
6. If angulation in both orthogonal planes, then an oblique plane deformity is present
radioulnar angular limb deformities frequently include torsion
Uniapical Deformities
- premature closure of the distal physis of the ulna and possible associated premature closure of the lateral aspect of the distal radial physis
- valgus, procurvatum, and torsion of the radius.
- gross appearance of cranial bowing of the antebrachium, valgus deviation and external rotation of the distal limb
- CORA may occur anywhere > most frequently localized on/proximal to, the distal physis
- radial deformities in distal diaphysis or metaphysis can occur congenitally and may result in lateral deviation and luxation of the radial head
- deformities occur secondary to malunion
Biapical Deformities
- two CORAs within the cortical confines of the radius
.1.Partially compensated - planes of the proximal and distal CORAs occur in opposite directions
- result of the Hueter-Volkmann law
- proximal CORA with varus deviation, partially compensated by a distal CORA with valgus deviation
- many chondrodystrophic dogs naturally possess biapical, partially compensated
.2. Noncompensated - planes of the two CORAs exist in the same direction, thus magnifying the overall deviation of the deformity in one direction
Multiapical Deformities
possess more than two CORAs
craniomedial approach
distal radius juxta-articular (metaphyseal or epiphyseal) deformity
- if hinged ring fixator > opening osteotomy may be placed on the CORA
- insufficient bone or using a bone plate, then Paley’s second rule can be employed > osteotomy proximal to the CORA.
- result in a translational deformity
- use cylindrical or true dome osteotomy blade
What are the treatment options for congenital radial head luxation?
- Conservative managment
- Open surgical reducation and fixation (50% retained reduction of between 50-80%, 50% reluxated)
- Radial head ostectomy (in young dog regrowth become exuberant, humeroulnar articulation in the adult dog)
- Arthrodesis
Antebrachial Fracture in the Juvenile Patient
- Salter-Harris fracture of proximal or distal radial physes or the distal physis of the ulna
proximal radius - challenging because of the small size of the epiphysis, the complexity of surrounding soft tissue, and the constraints of the elbow joint
- ORIF, craniolateral approach
- epiphysis is cross-pinned to the metaphysis with Kirschner wires
distal physis of the radius
- usually accompanied by a fracture of distal ulna
- fluoroscopically guided closed reduction
- Kirschner wires crossed, starting at the radial and ulnar styloid processes and directed proximally
- caudal splint for 1 to 2 weeks to gain additional stability (protect against the force generated by the long lever arm)
- removal of the implants in 4 to 6 weeks
- possibility of premature closing of the radial or ulnar physes, may result in 3 issues:
.1. radial shortening,
.2. elbow joint incongruity
.3. antebrachial angulation
greenstick, or incomplete, fractures
- nondisplaced nature, successfully achieved with external coaptation
- immobilize both carpus and elbow
What are the surgical options for proximal radial fractures?
T-plate
CESF
Proximal ulna stabilised to distal radius with ESF (type Ib or type II)
Fractures of the proximal Ulna
radius transmits load between elbow and carpus
Nonarticular ulnar fractures proximal to the elbow joint are usually avulsion fractures of the olecranon
- pull of the triceps brachii muscle group, tensile forces must be counteracted
- caudal or lateral approach > lateral has less pressure when lying sternally; thus, incision dehiscence may be avoided
- two Kirschner wires and a tension band along the caudal aspect
- retrograde fashion reduces the risk inadvertently directed into the trochlear notch
- fixation strength increases with increasing implant diameter, and wire diameter is more critical than pin diameter
articular #
- minimize changes associated with secondary osteoarthritis
- bone plate and screws along the caudal or lateral cortex of the bone
- caudal: biomechnically because tension surface, disadvantage soft tissue coverage is sparse, may become irritated
- comminuted fractures of the proximal part of the ulna may require interfragmentary compression techniques
- Nonreducible fractures > ESF, severe osteoarthritis and loss ROM are certain sequelae.
What are the 4 types of Monteggia fracture?
ulna # accompanied by subluxation or luxation of the radial head
Type I: Cranial luxation of the radial head with cranioproximal angulation of ulnar fracture
Type II: Caudal luxations of the radius and caudal angulation of ulnar fracture
Type III: Lateral luxation of the radius
Type IV: Fracture of the proximal part of the radius and the ulna diaphysis with cranial luxation of the radial head
- annular ligament is still intact, closed reduction of the radial head + IM pin (and cast)
- fractures of the ulna distal to the coronoid processes, the radioulnar joint is also luxated, thus necessarily disrupting the annular ligament
- If the radioulnar joint is no longer intact, will have to stabilise once radial head is reduced (screw from caudal to cranial) + plate for ulna
- radioulnar screws are subject to tremendous shear forces, To eliminate the effect on limiting radioulnar motion and prevent screw failure, screws may be removed 4 to 6 weeks following repair.
ulna is most frequently fractured just distal to the coronoid processes
