Ch 52 Elbow disease Flashcards
List the extensor muscles of the elbow joint
What innervated these muscles?
Extensors are innervated by the radial nerve and include:
- Triceps brachii
- Tensor fascia antibrachii
- anconeus muscle
List the main flexors of the elbow joint and the associated nerve
Biceps brachii - musculocutaneous n
brachialis m - musculocutaneous n
Extensor carpi radialis - radial n
What is the normal range of motion of the elbow?
At what point of extension does the anconeal process articulate with the olecranon fossa?
Normal range of motion 130 deg
- 36 flexion
- 165 extension
- At 135deg, anconeal process articulates with olecranon fossa
elbow anatomy
hinge (ginglymus) joint composed of three smaller synovial joints:
1. humeroulnar joint (humeral trochlea and ulnar trochlear notch from the anconeal process to the radial incisure, including the medial coronoid process)
2. humeroradial joint (capitulum and radial head)
3. proximal radioulnar
ulnar coronoid processes increase the surface area of the elbow joint and restrict the degree of freedom of its range of motion to the sagittal plane
The base of the medial coronoid process articulates with the radial head and the humeral trochlea, ends in an apex located distal to the radial head
radius is the main weight-bearing bone of the antebrachium
Joint Capsule and Ligamentous Support
tendon of insertion of the biceps brachii muscle splits into a stronger band attaching to the ulnar tuberosity and a weaker band inserting on the radial tuberosity
The brachialis muscle inserts between these two bands as a large flat tendon of insertion on the ulnar tuberosity
medial collateral ligament attaches to the medial humeral epicondyle, crosses the annular ligaments, and then divides into cranial and caudal crura. The weaker cranial crus attaches to the radius proximal to the radial tuberosity, while the stronger caudal crus passes more deeply into the interosseous space and attaches mainly to the ulna
lateral collateral ligament attaches proximally to the lateral humeral epicondyle and also divides into two crura. Its cranial crus attaches distal to the neck of the radius, and the caudal crus attaches to the ulna and blends with the annular
annular ligament, which may contain a sesamoid, spans transversely around the radial head, essentially forming a ring in which the radius turns during rotation of the antebrachium
The interosseous ligament, the interosseous membrane, and the ulnar attachment of the abductor pollicus longus muscle are major stabilizing structures
Functional Anatomy
Torsion and movement in the mediolateral plane are limited by the anconeal process and the collateral ligaments
olecranon fossa of the humeral condyle articulates with the anconeal process of the ulna during joint extension beyond 90 degrees and restricts elbow movement in the sagittal plane
When the elbow joint reaches 135 degrees of extension, the anconeal process articulates with the olecranon fossa and acts as the only primary stabilizer in pronation. In this position, the lateral collateral ligament provides primary stabilization for supination
paw can be rotated anywhere from 17 to 50 degrees laterally (supination) and from 31 to 70 degrees medially (pronation)
Contact area is greater in the lateral than in the medial compartment, regardless of flexion angle or antebrachial rotation
location of the area of peak contact pressure in the medial compartment shifts toward the apex of the medial coronoid process in pronation (medially)
What is the Campbells test?
Testing rotation stability via the collateral ligaments with the elbow and carpus held at 90deg
when the elbow and the carpus are held at 90 degrees, the medial collateral ligaments are responsible for the rotational stability of the elbow joint
What are the three regions of conctact in the elbow?
1.Craniolateral aspect of anconeal process
2. Radius
3. Medial coronoid process
How much of the weight through the elbow goes through the radial head?
51%
the proximal articular surface of the ulna appears to contribute substantially to load transfer through the canine elbow joint.
approaching the elbow medially
care should be taken to avoid the median nerve and the associated branch of the brachial artery, both of which lie beneath (lateral to) the pronator teres muscle at the craniomedial aspect of the joint
osteotomy of the olecranon
as they cross the caudomedial aspect of the joint before they continue distally between the flexor carpi radialis and superficial digital flexor muscles.
Which direction is most common for traumatic elbow luxation? Why?
What position does the elbow need to be in to allow for luxation?
pathophysio
Lateral (92 - 100%)
- Relatively large humeral trochlea
- MCL is inherently weaker
Elbow must be flexed beyond 45 degrees to unlock the anconeal process from the olecranon fossa
- older than age 3 years, young dogs more likely to suffer fractures
- large-breed dogs may be more susceptible
- result of indirect rotational forces transmitted to the joint
- study: not possible unless at least the lateral collateral ligament was transected
- cats, luxation requires transection of both the medial and lateral collateral
- associated with disruption of the joint capsule, rupture or avulsion of collateral ligaments, and articular cartilage damage
ulna displaced lateral to the humerus
What percentage of dogs with traumatic elbow luxation will have concurrent collateral ligament damage?
18 - 50%
elbow lux diagnosis
- characteristic position— antebrachium in abduction and external rotation, and with the elbow joint in slight flexion
- swollen, and crepitus and a pain response
- chronic luxation > 3 weeks
- assess for concurrent traumatic injuries.
- Neurologic assessment: cutaneous autosomes and withdrawal reflex.
- confirmed by radiographs or [CT]
- 16% of cases, the anconeal process remains in the olecranon fossa
- look for articular fractures, OA
elbow lux Tx
attempt at closed reduction is indicated for the treatment of acute luxation in an otherwise normal joint
contraindicated in cases of concurrent intra-articular or periarticular fracture
CT may be indicated to determine the source of the fragment
Salvage procedures may be considered for elbow joints with severe osteoarthritis.
Closed Reduction and Stabilization
- Neuromuscular blockade and regional analgesia
- elbow joint hyperflexion > fatiguing the soft tissues
- goal: lock the anconeal process into the olecranon fossa and use it as a fulcrum
- flex beyond 90 degrees, antebrachium internally rotated (pronated) and abducted to slide the anconeal process in
- medially directed pressure to olecranon +/- towel clamp
- anconeal process reduced > joint extended, and the antebrachium is adducted and internally rotated.
- Pressure to radial head to force it medially
- taken through a range of motion
- assessed both radiographically and physically for instability
- Radiographic evidence of mild radial head subluxation ok, Stress radiographs with the limb extended
- Campbell’s: joint and carpus at 90 degrees of flexion so that rotational stability relies primarily on the collateral ligaments
- Mild to moderate laxity noted will usually resolve > compared with that of the normal contralateral elbow
- elongation of collateral ligaments would explain successful outcome can be obtained
- experimental evidence > cats requires transection of both collateral ligaments, surgical management recommended
What approach is recommended for open reduction of elbow luxation?
Caudolateral
What are the options ofr post-op immobilisations after elbow reduction?
Spica splint
ESF (connecting bars can be replaced by tight elastic bands to allow some early motion)
External coaptation
(after either open or closed) > maintain the limb in extension, locking the olecranon into the fossa to prevent recurrence.
Operated elbow joints retained only 19% of their original stiffness > repairs failed from suture pull-out.
minimum of 2 to 3 weeks is recommended
strict exercise restriction is enforced for the first 4 to 6 weeks
ESF
two centrally threaded pins of appropriate diameter parallel to the articular surface of the elbow joint, elbow joint is held at approximately 140 degrees of extension while the two pins are fixed
connecting bars can then be replaced by tight elastic bands
benefits of early mobility of the joint?
- decreased adhesions between periarticular structures
- stimulation of the synthesis of glycosaminoglycans and hyaluronate
- encouragement of more orderly collagen deposition and normal cross-linkage
- improved joint nutrition
- improved clearance of the joint hematoma.
Prolonged immobilization (≥3 weeks) results in?
- decreases synovial fluid production
- cartilage stiffness and thickness
- leads to osteoarthritis
- loss of muscle mass and bone mineral content
Open Reduction and Stabilization
when indicated? (5)
indicated:
- avulsion fracture (collateral ligament attachment)
- fracture articular surface
- intra-articular interposition of soft tissues
- instability or reluxation after closed
- chronic luxation
caudolateral approach (aconeus subperiosteal dissection)
articular surfaces are inspected
placement of a clamp
freer to lever the radius and ulna medially
thoroughly lavaged and elbow joint stability assessed using Campbell’s test
Reconstruction of supporting soft tissues
primary repair with augmentation or ligament replacement with synthetic materials (Damaged ligaments tend to be friable)
anchored using screws and spiked washers or bone anchors. Avulsions of the distal attachments of the collateral ligaments are sutured to the annular ligament
figure of eight pattern. Nylon, polypropylene, or a braided polyblend suture (FiberWire,
Patients with medial and lateral collateral ligament rupture may be managed by a technique that relies on transcondylar tunnels and biaxial suture repair > transhumeral (craniodistal epicobdyles), ulna (half btw trochlear joint and cortex) and radial (LCL attachment) bone tunnels
Salvage procedures may be considered in chronic
elbow lux prognosis
- not been assessed objectively
- Untreated luxation is associated with muscle contraction, fibrosis of periarticular tissue
- good to excellent: treated early, stability is achieved after closed reduction, and physical rehabilitation is started early.
- One retrospective: good to excellent approximately 89% of 35 dogs
- good to excellent outcome: 8 of 19 dogs (47%) with closed reduction (persistant instability)
- n = 37, 20 open reduction) closed reduction, followed by open reduction if unsuccessful, good to excellent outcome in the majority, 7 had major complications
complications
- after a closed reduction is reluxation
- osteoarthritis, observed in all cases
- decreased range of motion
- excessive drainage and infection around the pin tracts
- fracture of the olecranon
- premature pin loosening
What are the three types of congenital elbow luxation?
Type I: Humeroradial (young, medium- to large-breed puppies, similar to asynchronous growth between the radius and the ulna)
Type II: Humeromedial (most common type, small-breed dogs and is associated with limb deformity and severe disability)
Type III: Combined (generalized joint laxity (polyarthrodysplasia) and multiple congenital skeletal deformities, rarely treated)
How do you treat Type I humeroradial luxation?
reported in a multitude of breeds
Conservative
- mild clinical signs
- chondroprotectant administration,
- controlled exercise
- professional rehabilitation
- closely monitored until maturity
- delaying surgery increases risk of irreversible changes (remodeling of the articular surfaces, OA)
Sx
lateral approach proximal end of the radius
1. Oblique osteotomy distal to radius physis or wedge ostectomy of radius with bone plate or ESF
Reduction maintained with temporary transarticular pin (4 weeks, cartilage damage) or intraosseous screws between radius and ulna (2-3weeks)
Spica spint or carpal flexion bandage
2. radial head ostectomy
3. arthrodesis: superior alternative to amputation and is reserved for chronic dislocations and joints with severe degeneration
outcomes
inconsistent in lit > results in functional improvement case reports/series.
ligament reconstruction is inconsistent, importance of this is unknown.
considered a contraindication to joint replacement
complications
implant failure or migration,
reluxation or malalignment,
fracture,
decreased/loss ROM
progressive osteoarthritis,
physeal damage
resorption,
radioulnar synostosis
infection.
present with mild clinical signs at 2 to 5 months of age
lateral approach to the proximal end of the radius
How do you treat Type II humeroradial luxation?
Lateral rotation/luxation of the ulna affects predominantly small purebred dogs
deformity is typically noted at birth or soon thereafter
anconeal process and the medial coronoid process are variably present
Conservative treatment may be considered for patients with good function and no pain. However, early reduction and stabilization of the joint are generally indicated
Closed Reduction and Immobilization
younger than age 4 months
recurrence is prevented by placement of a transarticular pin or a modified ESF
one or two small threaded K wires from caudal to cranial through the trochlear notch into the distal end of the humerus.
removal 14 to 21 days later
caudolateral approach to the elbow
transposition of the olecranon medially and distally, ulnar osteotomy and radioulnar synostosis, trochlea and trochlear notch reconstruction, external fixation, and transarticular pins
developmental elbow: umbrella term for these disparate, but probably interrelated, conditions.
syndrome that includes several developmental abnormalities, leading to osteoarthritis, pain, and disability
Include
- fragmented medial coronoid process (FCP), - osteochondrosis (OC[D]) of the humeral trochlea
- ununited anconeal process
- articular cartilage damage
- joint incongruity.
inherited condition, incidence of 0% to 55%, depending on breed, population, and screening technique
young large- and giant-breed dogs, abnormality of the MCP + incongruity have been recognized in smaller (chondrodystrophic) breeds as well
precentage reported FMCP, OCD + inconguirity
- fragmented medial coronoid process (>96% of developmental elbow disease cases)
- osteochondrosis (2.7% to 25.4% > 25.4% of Golden Retrievers)
- incongruity (6.0% to 50.3% > 50.3% of Bernese Mountain Dogs)
medial coronoid process, osteochondritis dissecans of the trochlea, and elbow joint incongruity are often concurrent and affect the medial compartment of the elbow joint.
Flexor enthesopathy
(ununited medial humeral epicondyle)
not currently recognized as part of developmental elbow disease
Ununited anconeal process is also occasionally associated with lesions in the medial compartment of the elbow joint.
Incomplete ossification of the humeral condyle (IOHC) is another elbow disorder that can affect breeds of dogs susceptible to developmental elbow disease, such as the Labrador Retriever and the German Shepherd Dog
anconeal process
- provides stability by limiting mediolateral movement when engaging the humerus.
- While weight bearing, it is the primary stabilizer of the elbow joint in pronation and a secondary stabilizer in supination
Epidemiology
What dogs have the highest odds ration of UAP?
What percentage of dogs with UAP will also have FMCP?
How often is UAP bilateral?
Bernese Mt Dogs and Mastiffs
13 - 30% have concurrenct FMCP
Bilateral in 20 - 35%
male dogs twice as frequently as female
radioulnar incongruence reported in 50% to 100% of cases
often present btw 5 and 12 months
German Shepherd Dog, Golden Retriever, Labrador Retriever, Newfoundland, Rottweiler, Saint Bernard Dog, Great Dane, French Bulldog, Dachshund, and Weimaraner.
At what age does the anconeal process growth plate fuse?
14-15wk in Greyhounds
16-20wk GSD
Define positive and negative radioulnar incongruence
Positive: Ulna longer than the radius
Negeative: Radius longer than ulna
Pathogenesis and Pathophysiology of UAP
- radioulnar incongruity
- large-breed dogs have a secondary center of ossification of the anconeal process
- develops by appositional ossification, formation of a separate ossification center, or both
- STUDY: secondary center of ossification (SCO) was radiographically apparent in 16% of dogs> different to UAP.
- presence of SCO does not result in UAP,
earlier diagnosis should be possible due to the radiographic difference - etiology unclear; proposed theories:
metabolic
genetic
failed endochondral ossification,
repetitive growth plate trauma associated with rapid growth
underdevelopment of trochlear notch
incongruous growth between the radius and the ulna (proximal displacement radial head > pressure on anconeal process) - polygenic mode of inheritance
- instability caused by loss of the stabilizing function
- free or attached via fibrous tissue or fibrocartilage
elbow joint incongruity as reason for UAP (2)
- Damage to the distal ulnar physis, ulna becomes shorter than the radius> decreasing the distance between AP and radius> humeral condyle shifts proximally> excessive force on the developing anconeal process.
Repeated microtrauma > damage the center of ossification
supported by clinical reports of fusion from PUO - reduction in the vertical distance between AP and the radial incisure (decreased trochlear notch size) > poor articulation between the ulna and humeral condyle > increase loading AP thus preventing union
dx UAP
RADs
maximally flexed mediolateral radiograph > UAP dx (minimizes superimposition)
area of lucency (cleavage plane) is apparent
osteophyte production, joint distention, muscle atrophy, and irregular subchondral sclerosis
both elbows should be obtained
radiographic diagnosis traditionally not made until at least 20 weeks
CT or arthroscopy
diagnosis of concurrent dz
size and shape of the fragment, from which the likelihood of successful fixation
Treatment and Outcome UAP
Early intervention is recommended to optimize
reviewing studies : radiographic healing of the anconeal process is inconsistently defined + objective evaluation of function following surgical procedures is warranted
Anconeal Process Removal
caudolateral approach, midbelly incision anconeus muscle. The fragment is grasped
Although owners appeared satisfied with the surgical outcome, only 50% of dogs were free of lameness
warned of the progression of osteoarthritis
Consider removal > malformed anconeal process or severe OA
Anconeal Process Reattachment
dogs < 24 weeks of age
screws in lag fashion +/- K wires
from the articular surface> olecranon or caudal olecranon > anconeal process
Exact positioning is important, risk of implant failure
STUDY: Union obtained 2 to 6 months after surgery in 6 of 10 dogs retrospectively
theory of radioulnar incongruity > reattaching AP without PUO may increase the risk of implant failure
Ulnar Osteotomy/Ostectomy
rationale: contraction of the triceps brachii muscle to pull the ulna proximally during weight bearing.
This proximal migration> expected to restore the normal alignment of joint surfaces + alleviating the biomechanical loads on the AP by the humerus.
encourage union between the anconeal process and the ulna
proximal better than distal re facilitate proximal migration of the ulna > may be associated with higher morbidity (interosseous ligament prevents migration)
caudal tipping and varus deviation minimized by oblique plane or IM pin
complication > migration of IM pin
successful in dogs < 7 months and with a firmly attached and nondisplaced AP
STUDY: 15/21 healed, 17 good to excellent clinical outcome. Results were less favorable in another study 5 of 23 achieved union
limited caudal approach to the ulna
Anconeal Process Reattachment and Ulnar Osteotomy/Ostectomy
sole ulnar osteotomy or reattachment AP does not produce consistently acceptable outcomes > therefore both
total of 58 elbows has been reported in the literature, with an overall fusion rate of 93%. One of these studies was a retrospective multicenter analysis comparing the outcomes of two surgical >significantly better radiographic outcome than those that had only an ulnar osteotomy
What are the Tx options for UAP?
- Anconeal process removal (owners satisfied but only 50% free of lameness)
- Reattachment (dogs under 24 weeks with normal trochlear notch, 60% fusion 2-6m)
- Ulnar osteotomy/ostectomy
- Reattachment and ulnar osteotomy/ostectomy (fusion 93%)
What are some guidelines for an ulnar osteotomy for the Tx of UAP?
Most successful in dogs under 7m with firmly attached, non-displaced anconeal process
Located 3-6cm distal to articular surface
Proximocaudolateral to distocraniomedial at 40-50 degrees to long axis
+/- IM pin
What breeds are predisposed to flexor entheseopathy?
Labradors, GSD, English Setter
term flexor enthesopathy proposed to summarise pathological changes within the flexor muscles of the carpus and digits and their attachments to the medial epicondyle, without referring to any suspected, but still unknown, etiology (i.e osseous metaplasia, ununited medial humeral epicondyle etc)
What percentage of flexor entheseopathy is primary?
15 - 35%
What test can be performed to test for pain associated with flexor entheseopathy?
Extending the carpus while holding the elbow at 90 degrees
Rads
partial avulsion of the tendons, discreet enthesophyte on the medial aspect of the distal part of the humeral diaphysis (just proximal to the medial epicondyle) and large ossified bodies
Arthroscopy allows for evaluation of the tendinous muscle attachment from within the joint capsule,
What are the treatment options for primary flexor entheseopathy?
Conservative
Intra-articular methylpred
Tenotomy
Partial excision
Resection of osseous bodies
Prognosis is generally good with the primary form (i.e without intra-articular lesions and osteoarthritis)
Medial Compartment Disease
Definitions
medial coronoid process disease
medial coronoid sclerosis, coronoid microfracture, coronoid fragmentation or fissuring, and cartilage damage to the coronoid process
medial compartment disease
advanced” or “end-stage” in elbows with extensive damage to or loss of joint cartilage within the medial joint compartment
Cartilage lesions within the medial compartment include:
OCD
abrasion from humeroulnar conflict i.e., “kissing lesions”
joint incongruity
Epidemiology elbow dz
young, large- to giant-breed dogs.
Males twice as frequently
OCD + MCPD share similar breed predisposition in Labrador Retrievers, German Shepherd Dogs, and Rottweilers
incongruity is seen primarily in lab, GSD, Rotti, bernese affecting 60% of elbows with medial coronoid process disease
elbow joint incongruity > chondrodystrophic breeds
OCD present between 5 and 8 months, medial coronoid process disease is 13 months
bilateral disease has been reported as anywhere from 25% to 80% of dogs
distinct biphasic pattern, with peaks at ≤3 years and ≥7 years
incidence of multiple components varies > anywhere from 0 to 60%
Etiology elbow dz
screening programs still based on the radiographic appearance of elbows, rather than on genetic screening, because the genes involved remain unidentified
osteochondritis dissecans, medial coronoid process disease, and elbow joint incongruity appear to be inherited independently as polygenic traits
complexity of inheritance and the effect of environmental variables in disease expression
complexity also affects breeding programs focusing on phenotypic selection
phenotypic selection results in the exclusion of at most 18% of the highest risk animals from breeding.
Estimated breeding values have been shown to be more reliable than phenotype
etiopathogenesis of medial coronoid process disease
Micro-CT evaluation of coronoid processes at 5, 7, 9, and 12 weeks of age clearly proved the absence of a secondary ossification center
STUDY: no evidence of osteochondrosis on histomorphometric analysis of MCP in 38 dogs, instead, microcracks were noted in the trabecular bone > indicate that fatigue microdamage of the underlying subchondral bone plays a crucial role in the pathogenesis (consequence of excessive loading of this area)
Microdamage and loss of osteocytes and canalicular density was greatest in the radial incisure region
structural changes within the subchondral bone precede articular cartilage fissure/fracture
STUDY: Prospective and, in part, serial evaluation of medial coronoid processes of growing Labrador Retriever puppies,186-189 with or without developmental elbow disease, using radiography, CT, necropsy examination, micro-CT, and histology revealed that medial coronoid process disease begins at approximately 15 weeks of age and that it involves only subchondral bone > By 15 weeks of age, localized disturbance of endochondral ossification, leaving weak points that may develop into cracks between the retained cartilage and the subchondral bone
Pathophysiology
Medial Coronoid Process Disease
Delay in endochondral ossification and biomechanical forces acting on the medial coronoid process during maturation are thought to initiate cleft formation, fracture, bone remodeling, and, ultimately, fatigue of the subchondral bone, resulting in the medial coronoid process disease
Overloading of the medial compartment of the canine elbow joint may result from different forms of joint incongruence, humeroulnar conflict, and/or joint instability
point pressure on the radioulnar joint cup, the joint surface formed by the humeroulnar and humeroradial joint surfaces, with areas of high load and stress at the anconeal and medial coronoid processes.
> mismatch between the humeral condyle and the shape of the radioulnar joint cup is one type of joint incongruence potentially associated
Elbow joint incongruence: misalignment of any of the three joints constituting the canine cubital joint: radioulnar, humeroradial, and humeroulnar joints.
traditionally as two forms of incongruity:
(1) small radius of curvature) shape of the trochlear notch of the ulna, leading to humeroulnar incongruence
(2) an uneven alignment of the radius and ulna (short ulna or short radius), leading to radioulnar incongruence and humeroulnar conflict.
Theorized Mechanism and Type of Incongruity in the Development of Medial Coronoid Process Disease (6)
.1. insufficient growth of the trochlear notch, leading to a slightly elliptical notch that is too small to accommodate the humeral trochlea, Unproven to be present
.2. Radioulnar incongruity (RUI)
- static axial radioulnar incongruence (short radius) leads to redistribution of load-bearing forces from the radial head to the medial coronoid process dt creates a step at the level of the radial incisure and proximal displacement of the entire coronoid process
- localised positive RUI at apex: tip deformation, (dt Abnormal development). rejected: authors concluded that subchondral bone surface geometry does not relate to medial coronoid process disease (normal anatomical variation)
- traditional linear model: Positive RUI = short radius → pressure on MCP or Negative RUI = short ulna → pressure on AP. The documented coexistence of ununited anconeal process and medial coronoid process disease in the same joint challenges the linear model
- Angular vector model
Positive RUI = short radius → pressure on MCP
Negative RUI = short ulna → pressure on MCP and AP: hort ulna) is believed to increase intraarticular pressure within the medial joint compartment by applying force against the lateral aspect of the humeral condyle. while CT restrospective STUDY documents negative RUI > Experimental evidence is lacking.
axial radioulnar incongruence, is thought to develop as a consequence of asynchronous growth between the bones
etiologic relationship between the initiation of medial coronoid process disease and radioulnar incongruence has been disproved by prospective monitoring of the development > puppies that later proved to have medial coronoid process disease showed normal skeletal development similar to the seven sound control dogs: but probably related to course and severity of disease later on
.3. Dynamic axial RUI
Same scenarios as with static RUI, but being dependent on deformation of the radioulnar joint cup during weight-bearing activity
(dt elasticity in the interosseous membrane in young) but adult dogs without elbow disease, activity results in dynamic axial translation
.4. Rotational RUI
Supraphysiological loading of the lateral aspect, along the radioulnar joint, postulated to be mechanical cause of radial incisure fracture/fissure pattern
- Load-induced pronation → pressure of radial head on MCP
- Mismatch between curvature of the radial head and MCP → radioulnar conflict
- Increased biceps brachii and brachialis muscle pull → pressure of MCP on radial head
Micro-CT findings: some torsional force component in fragment development, torque moment could result from soft tissue laxity in the lateral aspect
excessive pull of the biceps brachii/brachialis muscle > eccentrically located position (medial to the joint), a substantial portion of the flexion forces would be expected to cause supination, thereby creating shear
.5. Varus-instability of the humeroradioulnar joint
Osseous conformational discrepancy/ ligamentous insufficiency> allow for angulation of the humeroulnar joint surfaces (varus deformation)
Varus-instability → compression of MCP between humeral trochlea and radial head
.6. Dynamic axial humeroulnar joint instability
Osseous conformational discrepancy/ ligamentous insufficiency, relative humeroulnar rotational instability, moment forces the trochlea against MCP, probably resulting in repetitive, chronic mechanical overload
STUDY: kinematics in sound dogs and MCPD, In vivo humeroulnar contact patterns support this assumption of mechanical overload at the lateral border
Describe the Modified Outerbridge Scoring System
MOS 1: Cartilage softening anf swelling
MOS 2: Partial thickness surface defects, fibrillation
MOS 3: Deep fibrillation to subchondral bone
MOS 4: Full thickeness cartilage erosion
MOS 5: Subchondral bone eburnation
Arthroscopic Grading Scheme for Medial Compartment Lesions
MOS + MCP changes + humerus changes
RADS for MCPD
- craniocaudal (OA, OCD, FMCP)
- 90 degrees mediolateral (inconguirity)
- flexed mediolateral projections (UAP)
Radiographic evaluation for medial coronoid process disease is directed at excluding other lesions dt low sensitivity
Suggestive of MCPD (sn 80% sp 100%):
- Trochlea notch sclerosis
- blurring cranial margin of the medial coronoid process
Fitzpatrick et al: 13 of 437 (3%) elbows, considered to be free of any radiographic evidence later arthroscopic dx of MCPD
high incidence of false-negative radiographic diagnoses (specificity, 10% to 69%
CT or arthroscopy is highly recommended in dogs with lameness localized to the elbow joint
opacity at proximal aspect of the anconeal process can be incorrectly interpreted as a mild form of osteophytosis
appreciation of subtrochlear sclerosis may be rather subjective
width of sclerosis on mediolateral radiographs: sensitive predictors of MCPD (91% to 93%)
although juvenile elbow screening may reveal radiographic changes in dogs with developmental elbow disease, negative findings do not necessarily rule out medial coronoid process disease
Radiographic assessment of periarticular osteophytosis where?
- proximal surface of the anconeal process,
- cranial aspect of the radial head,
- cranial edge of the medial coronoid process,
- caudal surface of the lateral supracondylar crest,
- medial contour of the humeral trochlea,
- medial contour of the medial coronoid process
What is the internation elbow working group (IEWG) grading system for developmental elbow disease base on radiographs?
0 = Normal elbows
1 = Mild: osteophytes less than 2mm high, subtrochlear sclerosis but trabecular pattern still visible
2 = Moderate: Osteophytes 2-5mm high, obvious subtrochlear sclerosis (no trabecular pattern). RU step 3-5mm, indirect signs of primary lesion
3 =Severe: Osteophytes over 5mm high, RU step over 5mm, obvious primary lesion
What are the 4 types of medial coronoid process shape?
Which is most common in normal elbows?
- Type 1: Round
- Type 2: Pointed
- Type 3: Flattened
- Type 4: Irregular
Type 1 most common in normal elbows
Type 4 indicative of FMCP
What is the most common technique for assessing incongruence?
Fragment Removal and Subtotal Coronoid Ostectomy
probe the medial coronoid process
Transection of the fibrous attachments or use shaver (round burr tip (3 to 3.5 mm)), osteotome
why coronoidectomy:
- Because microcracks can be present (recurrent fragmentation and persistent pain)
- improvement of joint incongruence in the presence of positive radioulnar incongruity
- Exact guidelines for resection margins of have not been published > my vary according to fragment size
- Fitzpatrick et al: the medial portion of the MCP from its medial border to the most caudal extent of the radial incisure cranial to the sagittal ridge of the trochlear notch
- Conservative approach: starting osteotomy just caudal to the medial collateral ligament and slightly caudal to the coronoid fissure
- Aggressive could significantly reduce the weight-bearing surface of MCP > resulting in humeroulnar conflict with acute end-stage medial compartment disease
- fragment removal, without subtotal does not address the underlying cause of the disease > palliative
thorough evaluation of intra-articular structures
biceps ulnar release procedure (BURP)
treatment option for concept of rotational (transverse-plane) radioulnar incongruity
- eccentric attachment of the biceps at the ulnar tuberosity, just distal to abaxial MCP, > muscle contraction produce a large rotational moment in the form of supination
- moment rotates the craniolateral border of the MCP against the radial head (compressive stress + microdamage)
- BURP eliminate the proximally directed traction at the ulna
- tenotomy > cranial to the ulnar tuberosity and just caudal to the medial collateral ligament
- Arthroscopically assisted biceps ulnar release, using an arthroscopic push knife, has been shown to be safe
- No objective method has demonstrated the clinical contribution of this mechanism of trauma
- there is very limited clinical evidence regarding the contribution of rotational dynamic incongruity to the pathogenesis of medial coronoid process disease or regarding the efficacy of the biceps ulnar release procedure
Osteotomy of the Ulna
Static osteotomies
- involve intraoperative lengthening or shortening to correct for radioulnar incongruity followed by stable internal fixation
- reduce postoperative morbidity compared to that of dynamic osteotomies; however, precise measurement of incongruity and the correction needed to reestablish congruity = procedural limitation (arthroscopy not help)
Dynamic ulnar osteotomies
- rely on the forces (tension and compression) acting on the proximal segment to reestablish joint congruence.
- dictated by the action of soft tissues, articular interface and loading forces
- The pull of the triceps brachii muscle as well as flexor and extensor moments acting on the medial and lateral epicondyles are the most important muscle forces
- presence of positive radioulnar incongruity, realignment expected to occur by “pushing” the proximal ulnar segment distally
- adult dogs: axial shifts of 4.68 and 0.95 mm reported for proximally and distally performed ulnar osteotomy
- varying magnitudes of axial translation and tilting will occur. depends on if interosseus mobilised, IM pin used etc
- complications:osteotomy site instability, signs of discomfort, delayed or non-union, excessive callus formation, varus deformity,
ulnar fissure fractures and ligament or vessel damage.
Distal dynamic ulnar ostectomy (DDUO)
- abolish the supraphysiological pressure within medial joint compartment by allowing the ulna to slide proximally or distally as needed depending on the type (positive or negative)
- in older dogs is not advised because the interosseous ligament is expected to become too strong
- may last 2 to 4 weeks
- no precise data exist on the elasticity of the interosseous ligament (age), 4 to 6 months of thought to be the maximum age
- 4 to 5 mm of ulna
- 2 to 3 cm proximal to ulnar epiphysis.
- well tolerated, even when performed bilaterally
- preserve the periosteal envelope to avoid radioulnar synostosis
- =/- arthroscopically assisted fragment removal
- ostectomy–treated cases seemed to have only very mild progression of OA
Dynamic proximal ulnar osteotomy/bi-oblique
- BODPUO: junction of the proximal and middle one-third of the radius, with the long axis of the saw blade held at the most acute angle possible relative to the caudolateral cortex of the ulna
- Tilting and axial rotation of the proximal ulnar segment can be observed > excessive varus controlled by bi-oblique (fitz)
- following DPUO, incongruity only mildly reduced, but the concentration of joint contact at MCP was significantly ameliorated because of caudal tipping
- most proximal portion of the interosseous ligament should be elevated
- simultaneous bilateral bi-oblique associated with greater risk of postop complications
PROS:
- unload the medial joint compartment
- improve joint congruity
- better fit of the opposing joint surfaces
- overall increased load-bearing area
- combination with local intra-articular treatment of medial coronoid process disease or end stage dz or OCD
- Most reports lack a control group; therefore, observed improvement following DPUO might not be related to the procedure alone
- comparison of treated with and without DPUO indicates only weak superiority of dynamic (function and progression of OA)
- pinning would limit caudal tipping as well as varus deviation
- Clinical improvement in end-stage documented objectively using force plate analyisis
- On second-look arthroscopy, denuded humeral trochlea covered by fibrocartilage
proximal abducting ulnar osteotomy (PAUL)
kyon
custom locking plate (Advanced Locking Plate System [ALPS] PAUL, Kyon)
- mild abduction
- mild caudal tipping
- mild axial rotation of the proximal segment
derived from assessment of joints radiographed under simulated weight-bearing conditions > Mimicking short radius and subsequently performing a PAUL resulted in normalization of joint congruity.
- one specific radioulnar joint cup, which is present in approximately 30% of elbow joints
- manufacturer, PAUL unloads the medial compartment and thereby alleviates lameness, stiffness, and joint pain by introducing a slight abduction of the proximal ulna of 4 to 6 degrees
- Biomechanical testing: cadaver elbows incongruent due to a short radius confirmed the theory of medial joint unloading.
- load does not seem to be transferred from the medial to the lateral joint compartment
- STUDY: 64 elbow, end-stage medial compartment disease, improvement in lameness, Age affect prognosis, older dogs performing worse.
- reported complication rate is low (5% plate removal)
contraindicated if OA involves lateral compartment of joint
sliding humeral osteotomy (SHO)
New Generation Devices
derived from the application of closing wedge osteotomies as tx in human beings with unicompartmental arthrosis of the knee
- Based on contact patterns in normal cadaver joints, loads were distributed more equally (approximately 50 : 50) between the radius and the ulna
- transmitted through three zones of contact in the elbow joint
- uneven distribution of forces across the joint was aggravated by experimental radioulnar incongruity
- a lateral translation of the distal portion of the humeral diaphysis relative to the elbow would cause a shift in the radioulnar-humeral mechanical axis.
- fibrocartilage at the formerly denuded humeral trochlea prves redction innpressure/friction
- Pain scores and owner assessments of function generally improved and lameness resolved in approximately 66% of dogs available for follow-up
- initial complication rate was high, 19% (5% major complications) related to failure or instability of the bone-implant construct
STUDY: proximal segment, where shear loading appears to concentrate > locking screw created + stepped plate
- reduced the complication rate to 4.17% with no major complications. Lameness resolved in 49 of 60 limbs.
STUDY: 18 dogs, Significant improvement in ground reaction force
contraindicated if OA involves lateral compartment of joint
Canine Unicompartmental Elbow
Arthrex Vet Systems
- Pain related to end-stage medial compartment disease is thought to arise from bone-on-bone contact
- Reestablishing articular contact surfaces (focal joint resurfacing) could improve load transmission and joint kinematics, clinical function and ameliorate associated pain
- contraindicated if osteoarthritis involves the lateral compartment of the elbow joint
compare favorably with that of total elbow joint replacement BUT cannot be considered as minimally invasive:
- subluxation of the joint
- tenotomy of the flexor tendons
- desmotomy of MCL or osteotomy of medial epicondyle
- 4 to 6 mm diameter polyethylene plug in MCP (porous titanium socket for bone ingrowth)
- figure eight”–shaped cobalt chrome prosthesis into opposing humeral trochlea
- press-fit
- humeral implant slightly proud to restore normal joint space width > relieves pressure on the denuded joint surfaces around the implant + counterbalances the varus deviation
STUDY: multicenter, prospective (103 cases) (follow-up 10 months), catastrophic (1%), 11 major (10.7%), and minor (27.2%) complications. Functional outcomes: full (47.6%), acceptable (43.7%), and unacceptable (8.7%)
- CUE limited to MCPD (UAP is more lateral)
complications
- avulsion or nonunion of the medial epicondyle,
- implant malpositioning
- incisional/extraarticular infection
- persistent pain and lameness
safe, effective, consistent, repeatable and clinically practical
Effect of proximal abducting ulnar osteotomy (PAUL) on frontal plane thoracic limb alignment: An ex vivo canine study
Amadio 2020
Ex vivo cadaveric study.
Sample population: Canine thoracic limbs (n = 15 limb pairs).
There were differences in five of 12 limb alignment values pre-PAUL and post-PAUL in standing and recumbent positions
increase in mechanical medial proximal radioulnar angle and a decrease in elbow
compression angle
In the ex vivo setting, PAUL resulted in translation of the mechanical axis of the thoracic limb from a medial to lateral direction
The results of the present study provide evidence that in the ex vivo setting PAUL3 has more dramatic effects on limb alignment values compared with PAUL2
use of contact pressure systems in small, confined, curvilinear joints is prone to a number of data recording errors.
CT evaluation of elbow congruity in
dogs: radial incisure versus apical medial
coronoid process fragmentation
Baud 2020
studied 99 elbows
results do not identify a significant difference in axial radioulnar congruity between the radial incisure and apical MCP
protocol used in our study to
measure joint space in the transverse plane, even though consistent between observers, has not been validated, no control group
Abnormal ulnar morphology in the radial incisure group could result in a fulcrum
effect within the radioulnar joint, overloading the radial incisure and predisposing to osteochondral damage at this site.
can exclude genetic contribution to the development of either radial incisure or apical fragmentation
Fluoroscopic kinematography studies have quantified dynamic change in humeroradioulnar articulation, revealing
axial incongruity of similar magnitude in both normal and dysplastic elbows (Rohwedder et al. 2017), as well as increased rotational humeroulnar laxity in dysplastic elbows (Rohwedder et al. 2018).
Lateral Radial Head Subluxation as a Complication Following Proximal Ulnar Osteotomy or Ostectomy in Eight Dogs
Heather Williams 2019
retrospective, Eight dogs
Five of the eight dogs had surgical revision
of lateral radial head subluxation. Resolution of lateral radial head subluxation was
achieved in four dogs
Such subluxation is debilitating and appears to result from ulnar osteotomy instability.
a greater proportion of lateral radial head subluxation dogs had angular limb deformities > cofounding factor
five of eight dogs had different concurrent procedures performed
interosseus ligament release??
The intra- and intertester repeatability of radiographic elbow
incongruity grading is high in chondrodystrophic dog breeds
Pulkkinen 2020
novel radiographic incongruity
grading system for assessing elbow incongruity
retrospective secondary analysis evaluating observer agreement
220 mediolateral antebrachial radiographs from 110 dogs with the elbow in
90◦ flexion.
A novel surgical treatment of type 3 congenital elbow luxation
in a dog
Gordon 2023
AVJ
The left trochlear notch is markedly flattened with irregular margins
and lamellar/smooth solid periosteal reaction. The left anconeal process
is blunted. The soft tissues of the left lateral elbow have heterogeneous
mineralization potentially secondary to surgery.
At the most recent review, 7 months postoperatively, the lameness
had become moderate weight-bearing lameness
CT attenuation of the medial coronoid process
is reduced in dogs with medial coronoid disease
but independent of arthroscopic disease severity
Humphreys 2022
Attenuation of the MCP was reduced in dogs with MCD compared with those with no MCD (P < .002). No significant
differences were observed in the attenuation between categories of severity (MOS). There was good inter- and
intraobserver agreement between measurements (intraclass correlation coefficient = 0.89 and 0.95, respectively).
CLINICAL RELEVANCE
MCP attenuation is reduced in dogs with MCD compared with dogs with no evidence of MCD. This finding may be
a useful tool for early detection of MCD, but there is no relationship with arthroscopic lesion severity.
Computed tomography-guided cannulated lag screw placement for treatment of ununited anconeal process: surgical technique, clinical outcome, and radiographic healing in 7 dogs
Danner 2024
7 canine, retrospectively evaluated
(0 to 3 months postoperatively) complications included seroma formation (n = 1) and major surgical site infections (2), with 2 patients requiring implant removal
All patients achieved radiographic union, defined as partial or complete bridging 5/8 joints partial bridging, 3/8 joints complete bridging) and pre- versus postoperative elbow arthrosis scores remained static in all patients.
2/7 had no PUO performed.
The present study is confounded by treatment of multiple elbow diseases, as those with concurrent incongruity or FMCP had secondary procedures performed and the effect of the secondary procedure was not investigated.
SSI necessitating implant removal occurred exclusively in German Shepherd Dogs
limitation to the present study is that fibrous bridging of the anconeal process to the ulna was not determined arthroscopically prior to lag screw
CT-guided lag screw placement is more difficult on patients with loose fragments;
Prolonged anesthetic time is a significant downside
level of asepsis that can be achieved is not comparable to the operating room, specifically the ventilation and flow of personnel cannot be equally controlled.
level of radiation exposure
Slight placement of the cannulated screw within the joint space may have also contributed to seroma formation, with synovial fluid movement through the screw into the subcutaneous space. Bone wax was placed in the screw head
Many of the UAP fragments measured < 10 mm in height. Therefore, engagement of screw threads within the fragment was minimal, and stabilization, lag effect, and stripping of the screw hole were all weighed when determining if changing to a shorter screw was necessary. All screws that breached the joint did so dorsal to the UAP articular
Countersinking of the screw was not performed but would distribute forces against the screw head evenly to reduce the risk of head fracture, and should be considered in future cases. Additionally, countersinking could potentially reduce soft tissue irritation and seroma formation.
Evaluation of subchondral bone cysts in canine elbows with radiographic osteoarthritis secondary to elbow dysplasia
Jones 2024
Retrospective cross-sectional study.
Sample population: Thirty-eight Labrador retrievers (total of 76 elbows).
Elbow computed tomography (CT) images
Subchondral bone cysts were only identified in elbows with osteophytic
new bone formation. The number and size of SBCs were associated with
radiographic OA severity
Subchondral bone cysts were identified as a feature of radiographic elbow osteoarthritis in Labrador retrievers, and their number and size were indicative of the presence and severity of radiographic elbow OA.
not confirmed histologically
tendency for SBCs to form within the medial compartment of the elbow.
this study has demonstrated that SBCs
are a recognized radiographic hallmark of osteoarthritis in canine elbows.
It is well established that other radiographic features of
OA do not always correlate with the clinical presentation; however, further research would be required to determine if SBCs are also nonpredictive
radiographic OA severity was based on the size of the largest osteophyte.
Outcomes of 11 dogs with short radius syndrome treated with acute arthroscopically assisted ulnar shortening
von Pfeil 2024
Case series.
Animals: Eleven client owned dogs
Radiographic and arthroscopic radiohumeral
articulation were improved and short-term (median 9 weeks) clinical improvement was
documented following AUS in all 11 dogs.
ostectomy of the ulna, interfragmentary orthopedic wire for fragments are compressed under arthroscopic control
until radiohumeral articulation is considered optimal. Plate for stabilisation.
treatment of fragmented medial coronoid process via subtotal coronoidectomy was performed
surgeons applied their personal experience from previous elbow arthroscopies to assess the physiological relationships of the articular surfaces
No major complications occurred. Minor complications: screw loosening without + superficial incisional irritation
Four dogs had follow-up more than 2 years
> LOAD scores suggesting no progression to severe elbow arthrosis or chronic pain
- average age of 12.7 months and none with significant deformity
- total length of the planned ostectomy resulted from the measured radioulnar distance and the addition of 2–3 mm
loss of normal radiohumeral articulation and increased transarticular load on the medial coronoid region of the ulna
treatment has been recommended for short radius syndrome >2–3 mm
Alternatives to AUS include ulnar osteotomy with pin
placement or an adjustable external/ring fixator.41
Advantages or disadvantages of these techniques in terms
of improve joint congruence have not been reported.
The radiographic progression of osteoarthrosis as a result of FMCP disease versus AUS could not be separated out.
retrospective nature and small sample size, multiple surgeons and limited outcome reporting
Relation of Computed Tomography-Based Static Axial Radioulnar Incongruence Measurements under General Anaesthesia and Dynamic, In Vivo RUI during the Walk in Canine Elbow Joints with and without Medial Coronoid Process Disease
Rohwedder 2021
prospective clinical study
Static axial radioulnar incongruence was measured using the
sphere fitting technique on computed tomography-based three-dimensional (3D)
models of radius and ulna. The in vivo pose of radius and ulna was derived from
radiostereometric analysis during the walk
Animals: skeletally mature controls or MCPD
In normal elbow joints, sRUI does not represent the in vivo condition
during weight bearing. Dynamic and slightly negative RUI occurs during loading
(0.2mm positive to 0.4mm negative RUI).
Current results show that sRUI persists in canine elbowjoints with MCPD during thewalk.
radioulnar biomechanics do not seem to be increased in dogs with MCPD. It rather seems that radioulnar motion is decreased
primary mechanism or a secondary result of the disease process?
Chronic pain and the
resulting lameness, muscle atrophy, a shortened stance
phase and probably altered muscle function might influence
angular vector model (AVM) into account,
which was developed to explain the effects of negative sRUI on the disease process of MCPD, a lifted radial head might lead to increased load onto the medial joint compartment. As negative dRUI was measured in sound elbow joints only, increase in mechanical overload due to the described negative dRUI, in accordance to the AVM, can be excluded
CT-based measurements of sRUI are comparable to the in vivo. Therefore, measurements performed under general anaesthesia can be seen as reliable and truly
representing the in vivo situation.
