Erosion of the medial compartment of the canine elbow: occurrence, diagnosis and currently available...

© Schattauer 2015 Vet Comp Orthop Traumatol 1/2015

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Erosion of the medial compartment of the canine elbow: occurrence, diagnosis and currently available treatment optionsE. Coppieters; I. Gielen; G. Verhoeven; D. Van Vynckt; B. Van RyssenFaculty of Veterinary Medicine, Department of Veterinary Medical Imaging and Small Animal Orthopaedics, Ghent University, Belgium

KeywordsElbow, cartilage, arthroscopy, erosion, medial compartment

SummaryErosion of the medial compartment of the elbow joint refers to full thickness cartilage loss with exposure of the subchondral bone (modified Outerbridge grades 4–5) of the medial part of the humeral condyle (MHC) and the corresponding ulnar contact area. This finding may appear in the absence of an osteochondral fragment or a cartilage flap, or in combination with fragmentation of the medial coronoid process (MCP) or osteo-chondritis dissecans (OCD) of the MHC.

With regard to the prognosis, it is important to diagnose these severe erosions. Imaging of cartilage lesions by means of radiography, ultrasonography, computed tomography or magnetic resonance imaging is challenging in dogs. In contrast, direct arthroscopic inspection provides detailed information about the cartilage.The treatment of these severe erosions is difficult because of the limited regenerative capacity of cartilage and presumed mechan-ical or physical triggering factors. Several conservative and surgical treatment methods have been proposed to treat elbows with se-vere cartilage defects. However, due to irre-versible loss of cartilage, the prognosis in these cases remains guarded.

Correspondence to:Eva CoppietersFaculty of Veterinary MedicineDepartment of Veterinary Medical Imaging and Small Animal OrthopaedicsSalisburylaan 1339820 MerelbekeBelgiumPhone: + 32 9 264 76 50Fax: +32 9 264 77 93E-mail: [email protected]

Vet Comp Orthop Traumatol 2015; 28: 9–18http://dx.doi.org/10.3415/VCOT-13-12-0147Received: December 10, 2013Accepted: October 23, 2014Epub ahead of print: November 14, 2014

Review Article

IntroductionElbow problems frequently cause forelimb lameness in young and adult large breed dogs (1–4). With the use of arthroscopy, the presence of lesions on the medial part of the humeral condyle (MHC) caused by friction from a fragment of the opposing medial coronoid process (MCP) has been recognized as a frequent finding in ad-

vanced elbow disease. Additionally, carti-lage pathology of the medial compartment in the absence of fragmentation of the MCP has also been reported since the early use of arthroscopy (1).

Recently these erosions have gained more interest because they are diagnosed more frequently with the use of arthroscopy (3–6). Regarding the prognosis, it is impor-tant to diagnose these severe erosions (7–8).

Demonstrating the presence of these lesions is the first challenge, because radiography and computed tomography (CT), the most commonly used techniques to diagnose elbow disorders, are unable to visualize car-tilage lesions (9). However, direct inspection via arthroscopy is a reliable technique to ac-curately diagnose the depth and extension of the erosions (1, 10–12). The second chal-lenge in joints with erosion of the medial compartment is the reduced capacity of car-tilage to heal. The regenerative capacity of cartilage is limited and underlying mechan-ical factors may obstruct healing (13). Since degenerative joint diseases frequently occur in man and dogs, cartilage repair is an im-portant current research focus. Other than general methods to treat cartilage lesions, some specific treatment methods have been designed to reduce the load within the medial compartment of the elbow joint in dogs (5, 14, 15). Moreover, several arthro-plasty methods are already available, but further modifications of these techniques are required to improve the results (16, 17).

The goal of this paper is to give an over-view of what is known about the occurrence and diagnosis of erosion of the medial com-partment. Furthermore, an overview is given of the treatment options specifically developed for the treatment of this debilitat-ing condition of the canine elbow joint.

Occurrence of erosion of the medial compartment of the canine elbow

The medial compartment of the elbow joint consists of the MCP, the MHC and the medial part of the semilunar ulnar notch. Originally the term ‘medial compartment

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10 E. Coppieters et al.: Erosion of the medial compartment of the canine elbow

disease' was used to describe the massive loss of cartilage in the medial part of the elbow (5). However, the term ‘medial com-partment disease’ is often used interchange-ably with the term ‘medial coronoid disease’, indicating fissuring or fragmentation of the MCP with or without severe cartilage dam-age (3, 18). Therefore the more descriptive term ‘erosion of the medial compartment’ is being used in this paper, to avoid con-fusion and to set out a better specification of the pathology within the joint. Accord-ingly, erosion of the medial compartment refers to full thickness cartilage loss expos-ing the subchondral bone (modified Outer-bridge grades 4–5) (▶ Table 1) of the MHC and the corresponding ulnar contact area (4, 5).

Erosion of the medial compartment of the elbow joint is a sign of severe osteo -arthritis, since cartilage loss is one of the characteristics of osteoarthritis besides subchondral bone sclerosis, osteophyte and enthesophyte formation and inflammation of the joint capsule (18, 19). Joints affected by severe cartilage damage will often show these osseous changes. However, in some cases clear radiographic signs of pathology are absent, while arthroscopy demonstrates extensive erosions (4). Therefore, severe cartilage erosion of the medial compart-ment cannot be accurately diagnosed from just the radiographic examination.

The presence of gross cartilage damage of the MCP and the MHC in the absence of an osteochondral fragment has been re-ported by several authors (1, 3, 4, 20–22). Erosion of the medial compartment oc-curred as the only pathological finding in six joints in a study reporting the patho -anatomical changes found at autopsy of 120 dogs (236 elbows). Histological exam-ination of one of these joints revealed an ir-regular appearance of the superficial layer and no abnormalities of the deeper layer of the cartilage (20). This form of erosion of the medial compartment seems to occur most frequently in adult and old dogs. In a study describing the arthroscopic findings in the elbow joints of dogs of six years and older, 31% of the dogs showed an extensive erosion of the medial compartment of the joint without a fragmented coronoid pro-cess. The presence of only erosions in the control group of young dogs (5–18

months) in the same study was only three percent (4). The exact cause of these carti-lage lesions is unknown. Possibly, abnor-mal forces caused by elbow incongruity, overweight or high activity level may cause abnormal loading of normal or abnormal cartilage resulting in erosion of the medial compartment (3, 4). In the authors’ experi-ence, erosions of lesser severity may also af-fect the lateral compartment in some dogs.

Erosion of the medial compartment can occur in combination with a fragmented cor-onoid process, osteochondritis dissecans (OCD), or both together (3, 8). In those cases, the erosions are considered concomi-tant, to indicate the simultaneous presence of the two elbow lesions without stating that one lesion is the cause or consequence of the other.

The term ‘kissing lesions’ is often used for cartilage erosions of the MHC in com-bination with a fragmented coronoid pro-cess, suggesting that the damage of the MHC is caused by friction from the coron-oid lesion (7, 23). Similar cartilage lesions of the MCP were described in joints af-fected by OCD of the MHC (24, 25). These concomitant erosions were a common finding in studies reporting on the appear-ance of the joint cartilage at necropsy (20, 24, 25). One study reported deep furrows

in some cases and erosions of the radial head in joints with severe osteoarthritis (20). In a study describing the arthroscopic findings in the elbow joints of 263 dogs with disease of the MCP (age 3 – 135 months), kissing lesions (modified Outer-bridge grade >0) were identified in 49% of the elbows. Modified Outerbridge grade 4 and 5 cartilage lesions of the MHC and of the MCP (= erosion of the medial compart-ment) were identified in 14.4% of the el-bows. A more recent theory for concomi-tant erosion of the medial compartment of the elbow joint states that incongruity might be the cause of cartilage loss. Frag-mentation could be the early consequence of elbow incongruity and thereafter erosion of the remaining and more resilient part of the MCP develops with subsequent erosion of the entire medial compartment (3).

Another presentation of erosion of the medial compartment has been described in a study of 35 joints of dogs with recurrent or persistent lameness after arthroscopic treatment of disease of the MCP. In this study, 60% of the joints showed extensive cartilage erosion at the second arthroscopic inspection. Many of those joints initially showed no or mild cartilage damage at the time of the first treatment (26). A similar case was described in a study on compli-cations of elbow arthroscopy (27). To date, it is unclear whether these erosions are the consequence of the original problem or in-duced by the arthroscopic fragment re-moval which might leave a degree of insta-bility in the joint.

Histopathological evaluation of cartilage damage

The modified Outerbridge score is used to quantify cartilage pathology in terms of the depth of the lesions (4). However, cartilage can also be evaluated microscopically using the Mankin histological and histochemical scoring system (28). According to this sys-tem, cartilage degeneration was categor-ized into three stages. Stage I with a Man-kin score of 0–6 points, indicates mild de-generative changes. Stage II with a Mankin score of 7–9 points, indicates moderate de-generative changes. Stage III with a Man-kin score of 10–14 points, indicates severe degenerative changes (i.e. cartilage disor-

Table 1 Modified Outerbridge classification system (4).

Modified Outerbridge classification

0

1

2

3

4

5

Description of gross cartilage findings

Normal cartilage

Chondromalacia (cartilage with softening and swelling)

FibrillationSuperficial erosions with pitting or a ‘cobblestone’ appearanceLesions that do not reach subchondral bone

Deep ulceration that does not reach the subchondral bone

Full thickness cartilage loss with exposure of the subchondral bone

Eburnated bone



11E. Coppieters et al.: Erosion of the medial compartment of the canine elbow

ganization or complete cartilage loss with extensive exposure of subchondral bone) (29). A moderate positive correlation has been demonstrated between the Mankin score and the visual cartilage pathology score of the MCP in 53 canine elbows (28). In this study, elbows with an Outerbridge score 4 had a score of 10.9 ± 0.4 by the Mankin system, equivalent to stage III car-tilage degeneration (28).

DiagnosisHistory of dogs with erosion of the medial compartmentSince the combination of elbow dysplasia lesions and ‘kissing lesions’ is a common finding, the breeds affected by concomitant erosion of the medial compartment are similar to the breeds predisposed for elbow dysplasia (3, 4). In those studies reporting cases with erosion of the medial compart-ment without concomitant fragmentation of the MCP or OCD, the breed of the dogs is not mentioned. This presentation of ero-sion of the medial compartment seems to be more common in older dogs but has also been described in young dogs (<1 year) (4, 21). In contrast, concomitant ero-sion can appear both in young adult dogs and in older dogs, probably depending on the size of the lesion and the chronicity of the problem (8, 21, 26). In a study report-ing erosion of the medial compartment as a finding in dogs with recurrent or persistent lameness after arthroscopic treatment of elbow dysplasia, the mean age of the dogs at second presentation was five years (9 months – 11 years). The average time be-tween the first and second presentation was 2.5 years (3 months – 6 years) (26).

Clinical findings

Dogs with erosion of the medial compart-ment are mostly presented with non-spe-cific clinical signs of elbow pathology (4, 8). Most dogs with erosion of the medial compartment demonstrate distinct clinical abnormalities such as severe lameness, a li-mited range-of-motion, signs of severe pain on elbow manipulation or explicit outward rotation of the affected limb and abduction of the elbow (7). Conversely, it is

the authors’ experience that some cases show only mild clinical signs.

Imaging of cartilage lesions

The radiographic diagnosis of these erosions in the canine elbow is challenging since only the osseous structures are visualized (30). Sclerosis of the subchondral bone and formation of osteophytes and enthesophytes are typical signs of osteoarthritis that are vis-ible on radiographic examination. In a study of elbow lameness in dogs of six years and

older, the degree of radiographic osteoar-thritis was significantly correlated to the ex-tent of the cartilage erosions, although se-vere erosions were also found without the development of osteophytes (4). In some cases collapse of the medial compartment is visible on the craniocaudal view (▶ Figure 1), which suggests the presence of cartilage erosions (30). However, care should be taken when evaluating the joint space in non-weight-bearing views. The limitations of radiography were also confirmed in a study demonstrating histological lesions in

Figure 1 A) Craniocaudal radio-graph of a normal elbow joint. B) Cranio-caudal radiograph of an elbow with erosion of the medial compart-ment. Severe new bone formation, collapse of the medial compartment of the joint and an irregular delineation of the medial part of the humeral condyle is visible.

Figure 2 Computer tomographic images of a sound elbow (left) demonstrating a normal medial joint space (arrow) and an elbow with erosion of the medial compartment (right) demonstrating explicit narrowing of the medial side of the joint space (arrow) and marked new bone formation.




cartilage lesions were visualized in detail by positioning the probe perpendicular to the humeral head (33). This is not possible in the elbow because of the anatomical struc-ture of the joint forcing the MCP opposite to the MHC in tight apposition.

Computed tomography is a routinely applied additional diagnostic technique to identify osseous lesions of the elbow joint (34). Direct imaging of cartilage with CT is not possible since CT cannot differentiate cartilage from other soft tissue structures (▶ Figure 2) (12). Cartilage lesions can be estimated indirectly based on the corre-lation between osteophyte size seen with CT and the degree of cartilage erosions of

the elbow joint seen on arthroscopy (12). Similarly, an irregular radial incisure of the ulna on CT was significantly associated with the arthroscopic identification of car-tilage erosions of the MCP. However the absence of those lesions on CT does not preclude erosion of the medial compart-ment (12). More information about the ar-ticular cartilage may be provided with CT-arthrography. In human medicine, CT-arthrography is being used to evaluate ar-ticular cartilage in several joints (35, 36). In veterinary medicine, the technique has only been described for the detection of meniscal tears, rupture of the cranial cru-ciate ligament in the canine stifle joint, or both lesions in combination (37–39).

The gold standard for articular cartilage examination in dogs is arthroscopy, a minim-ally invasive technique which allows direct in-spection of the intra-articular structures (1, 10–12, 27). The colour and surface anatomy of the cartilage can be inspected in detail. Typical lesions seen in joints with erosion of the medial compartment are full thickness cartilage lesions with exposure of subchon-dral bone, showing linear excoriations in ad-vanced cases (modified Outerbridge grades 4–5) (▶ Table 1) (▶ Figure 3). The cartilage of the lateral part of the humeral condyle mainly remains intact and is sharply delineated from the eroded area, although pathology of the cartilage of the lateral compartment of the elbow joint is occasionally observed (4, 25).

More sensitive diagnostic measures are required to identify those cases with marked cartilage disease and minimal radiographic or computed tomographic pathology. Magnetic resonance imaging (MRI) is regularly used in human medicine to detect osteoarthritic changes. In contrast to human joints, MRI of canine joints is not routinely used to visualize cartilage (40). Due to the low resolution of most currently available MRI devices in veterinary medi-cine, the opposing thin cartilage layers of the canine elbow cannot be clearly differ-entiated (41).

Treatment

The regenerative capacity of cartilage is li-mited due to the low cellular mitotic activ-ity of chondrocytes and the lack of direct

Figure 3 Different presentations of erosion of the medial compartment. A) Left elbow of a nine-year-old female crossbreed dog showing severe erosion of the medial compartment of the elbow joint with-out fragmentation of the medial coronoid process. The radial head (R) is also affected. B) Left elbow of a 10-year-old male Labrador showing erosion of the medial compartment of the elbow combined with a very small fragment of the medial coronoid process (arrow). C) Left elbow of a one-year-old male Ameri-can Bulldog showing erosion of the medial compartment with a clear wear lesion on the medial part of the humeral condyle (large black arrow), probably caused by the large fragment of the medial coronoid process (small red arrows). D) Left elbow of a seven-year-old male Labrador showing erosion of the medial compartment and a distinct delineation with the normal cartilage of the lateral compartment of the joint. Obvious linear excoriations are visible in the diseased area (arrow).

the cartilage of elbows that were scored as radiographically normal (28).

Visualization of bone and cartilage via ultrasound is limited by depth of pen-etration and ability to clearly distinguish tissue architecture because of the high acoustic impedance of bone (31). One study compared ultrasonographic findings with anatomic and radiographic features of the elbow joint. In this study, the head of the radius and its hyaline cartilage were im-aged but it remains unclear whether lesions of the articular surface of the MCP or the MHC can be visualized (32). In a study on the ultrasonographic appearance of osteo-chondrosis lesions of the canine shoulder,



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management of pain and lameness in case of erosion of the medial compartment. An important concern is the possible develop-ment of cartilage lesions in the lateral com-partment of the joint after performing slid-ing humeral osteotomy. Arthroscopic re-evaluation of some dogs several months postoperatively revealed healing of the pre-viously diseased medial joint compartment with fibrocartilage, and did not demon-strate any visible cartilage disease of the lat-eral compartment (5, 51). Necropsy in one dog 17 months postoperatively revealed a healthy cartilage cover on the lateral part of the humeral condyle with minimal indi-cation of disease (5). Long-term follow-up with force plate analysis of seven dogs demonstrated no significant improvements in limb function in three dogs (51).

A proximal ulnar osteotomy has been proposed as a method to treat radio-ulnar incongruity, a presumed cause of medial compartment overload. Performing a proximal ulnar osteotomy results in a movement of the proximal ulnar segment which may permit re-distribution of forces along the contact areas of the MCP (52, 53). A recent ex vivo study demonstrated

dicular to the long humeral axis and a special sliding humeral osteotomy-plate is fixed to the medial aspect of the humerus causing lateral transposition of the proxi-mal part of the humerus. This lateral trans-position results in reduced loading of the medial joint compartment. The technique was evaluated in an evidence based medi-cine level 4d study involving 59 elbow joints (49 dogs) with severe cartilage lesions and providing medium-term fol-low-up of 32 joints. Lameness improved in all 32 joints after 26 weeks and resolved in 21/32 joints. Reported complications were a humeral fracture, screw breakage, de-layed osteotomy union and minor surgical wound breakdown. Major complications requiring surgical revision were reported in up to 22.2% of the joints (5). More recent preliminary data from the same author demonstrate a reduction of the total com-plication rate to 4.17% (50). However, an-other recent evidence based medicine level 4a study involving 32 dogs (35 elbows) treated with a sliding humeral osteotomy reported major complications in 17% of the joints (51). Care should be taken in ad-vising a sliding humeral osteotomy for the

E. Coppieters et al.: Erosion of the medial compartment of the canine elbow

vascular supply (13, 42). Treatment of ero-sion of the medial compartment of the ca-nine elbow is challenging.

Conservative and pharmacologic treatment

Routinely used treatments for osteoarthri-tis can be applied to dogs with erosion of the medial compartment, including non-steroidal anti-inflammatory drugs, nutra-ceuticals, platelet-rich plasma, hyaluronic acid, and pentosan polysulfate sodium (13, 43-45). However, actual evidence that these products have a positive effect on the carti-lage lesions in the canine elbow is lacking.

Surgical treatment of erosion of the medial compartment of the canine elbow

In general, arthroscopy is performed to con-firm the diagnosis of erosion of the medial compartment. When observing a concomi-tant osteochondral fragment of the MCP (▶ Figure 3), it can be removed immediately (7, 18, 46). In an evidence based medicine level 4d study (▶ Table 2) describing the arthroscopic removal of a fragmented MCP as a single treatment in dogs with concomi-tant severe elbow incongruity (radio-ulnar step >3 mm), some dogs also had modified Outerbridge score 4 cartilage lesions. Des-pite the cartilage lesions, the dogs had a fair to good long-term outcome. Important limitations of this study included the small number of dogs (n = 8) and the lack of force-plate or motion analysis (46). In addi-tion to fragment removal, several procedur-es have been described to stimulate sponta-neous repair or to induce repair by cartilage transplantation (42, 47–49). However, infor-mation is lacking on the long-term results of these techniques.

As only the cartilage of the medial com-partment of the joint is significantly dam-aged, surgical techniques transferring the load bearing forces towards the healthy lat-eral compartment have been developed (▶ Table 3 and ▶ Table 4).

One such load bearing transferring technique is the sliding humeral osteotomy (▶ Figure 4). After arthroscopic joint in-spection and removal of fragments of the MCP, an osteotomy is performed perpen-

Table 2 Levels of evidence based medicine (65).

Grade

1a

1b

2a

2b

3a

3b

4a

4b

4c

4d

4e

5

*A cohort study is a study that follows a group of patients over a period of time and investigates the effect of a treatment or risk factor. †A case-control study is one that examines the effect of a risk factor on the outcome for a group of patients with a disease compared to that of a matched control group without the disease.

Description

Systematic review of randomized controlled trials (RCT)

Individual RCT

Systematic review of cohort studies*

Individual cohort study

Systematic review of case-control studies†

Individual case-control study

Lower quality prospective cohort/case control study

Retrospective cohort/case-control study

Case series – describing outcome for one treatment method with no control group

Case series – describing novel aspect of management and providing some information regarding outcome

Lower quality case series – concerns regarding study design and/or ability to interpret information

Expert opinion without explicit critical appraisal, or based on physiology, bench research or “first principles”




that proximal ulnar osteotomy is effective in unloading the medial compartment in an incongruent joint (54). A caudoproxi-mal to craniodistal and proximolateral to distomedial oblique osteotomy is recom-mended to prevent extreme tilting of the proximal ulnar segment (7, 55). The osteot-omy should be located proximal to the strong interosseus ligament because a distal ulnar osteotomy will not restore the radio-ulnar contact areas (52). A favourable clini-cal outcome after performing a proximal ulnar osteotomy was reported in dogs with focal deep cartilage lesions of the MHC, combined with treatment of the fragmen-tation of the MCP (7, 50). Force plate analysis was performed on 32 elbows at six

weeks, 12 weeks and six months after sur-gery. A significant improvement in peak vertical force was measured after six months (50). Complications were minimal and included infection, superficial inflam-mation due to self-trauma, excessive proxi-mal segment migration and seroma. A sec-ondary surgical intervention was never required (50). The actual lameness status was not mentioned in this evidence based medicine level 5 study and long-term fol-low-up data were not reported.

An external rotational humeral osteot-omy has been described as a technique with a potential beneficial effect in dogs with severe erosion of the medial compart-ment of the elbow (14). This technique was

only evaluated in a cadaveric study, proving a lateral shift of the peak pressure location and the centre of pressure, and thus reduc-ing the pressure acting on the ulna. How-ever, the orientation of the effective loading axis depends on the positioning of the leg during weight-bearing, so clinical trials are required to investigate the load shift after external rotational humeral osteotomy and to evaluate the efficacy of the technique for treating erosion of the medial elbow com-partment (14).

Another technique developed to unload the medial side of the canine elbow joint is the proximal abduction ulnar osteotomy. A transverse ulnar osteotomy is performed and fixed with a proximal abducting ulnar

Table 3 Summary of selected references related to in vivo evaluation of the surgical treatment of erosion of the medial compartment of the canine elbow joint.

Author

Fitzpatrick et al.,2009 (5)

Pfeil et al.,2012 (15)

Déjardin, 2012 (58)

Conzemius et al.,2003 (59)

Allen, 2012 (60)

Allen, 2012 (60)

MHC = medial part of the humeral condyle; PVF = peak vertical force; post-op = postoperative; NA = not available; SHO= sliding humeral osteotomy; PAUL = proximal abduction ulnar osteotomy; CUE = canine unicompartmental elbow.*Complication rate = lowest total complications rate reported.

Type of publication

Peer- reviewed

Proceedings

Proceedings

Peer- reviewed

Review

Review

Treatment method

SHO

PAUL

TATE

Iowa state

Sirius elbow

CUE

Number of dogs or joints

59 elbows of 49 dogs with carti-lage eburnation of the medial compartment

36 dogs with high grade cartilage erosion

39 dogs

20 dogs with elbow osteo -arthritis

NA

22 dogs

Compli-cation rate*

19%

11%

18%

30%

NA

NA

Reported complications

Humeral fracture, multiple/single screw breakage, delayed osteotomy union, wound breakdown, haematoma

Screw breakage, screw loosening

Ulnar fracture, implant loosening, pin mi-gration, screw loosen-ing, wound dehiscence, iatrogenic transection ulnar nerve

Intra- and post-op lat-eral luxation, intra- and postoperative fracture of the MHC, osteomyelitis

NA

NA

Subjective follow-up data

26 weeks post-op: resolved lameness in 21/32 elbows

>5 months post-op: resolved lameness in 13/18 elbows

NA

Satisfactory outcome (= increased post-op vertical force, reduced pain and owner satisfaction) in 80% of dogs

NA

>6 months post-op: 17/22 good or acceptable elbow function

Objective follow-up data (pressure/force plate)

Force plate analysis of 7 dogs, >12 months post-op: 3 dogs showed no improvement in limb function (51).

NA

Force plate analysis of 6 dogs, 6–12 months post-op: PVF > contra -lateral side

NA

NA




osteotomy platea with a step of 2 or 3 mm (▶ Figure 4). In an evidence based medi-cine level 5 study involving 36 dogs with high grade cartilage erosions, compli-cations were registered in four dogs, all in-volving screw breakage or loosening. Half the dogs were presented for re-examination after more than five months and 73% of these were sound (15). No peer-reviewed studies of this technique are available at the moment and concerns are similar to those for the other load transferring techniques: the risk of creating cartilage damage in the lateral compartment and the lack of long-term follow-up studies using objective measuring techniques.

A proximal ulnar rotational osteotomy, consisting of a transverse osteotomy with 30° external rotation of the proximal seg-ment, is also a technique that shifts contact pressures towards the lateral elbow com-partment. An ex vivo study demonstrated a significant decrease in contact pressure in the medial compartment and an increased pressure in the lateral compartment, but it is unknown whether this procedure would be efficacious in vivo (56).

Total elbow replacement and unicom-partmental elbow arthroplasty are other approaches to treating erosion of the medi-al compartment (▶ Table 3 and ▶ Table 4).

The first two total elbow replacement designs which were recently introduced are the Iowa stateb (Conzemius) prosthesis and the TATE®b (Acker) prosthesis (17). Both designs consist of a humeral and radio-ulnar component. The Iowa state design is a non-constrained, stemmed and cemented prosthesis while the TATE elbow system is semi-constrained and uses a cementless re-surfacing design (16, 17). An ex vivo inves-tigation revealed that the TATE arthro-plasty system accurately reproduces the sa-gittal axis of the elbow, which is a critical factor in the success of functional outcome in human elbow arthroplasty. This finding suggests that the TATE arthroplasty might be less predisposed to component loosen-ing, uneven wear and clinical failure (57). Objective data regarding the functional outcome following TATE implantation are

Table 4 Summary of selected references related to ex vivo evaluation of surgical treatment methods of erosion of the medial compartment of the canine elbow joint.

Author

Gutbrod and Guerrero, 2012 (14)

Cuddy et al., 2012 (56)

Burton et al., 2013 (57)

Smith et al., 2013 (62)

ERHO = external rotational humeral osteotomy; PURO = proximal ulnar rotational osteotomy; CUE = canine unicompartmental elbow; 3D = three-dimensional.

Type of publication

Peer-reviewed

Peer-reviewed

Peer-reviewed

Peer-reviewed

Treatment method

ERHO

PURO

TATE (first generation)

CUE

Number of dogs/joints

8 cadaveric elbows

12 unpaired cadaveric thoracic limbs

5 pairs of cadaveric forelimbs

6 pairs of cadaveric forelimbs

Evaluation system

Digital pressure sensors in sub-chondral osteo -tomy distal to the elbow joint

Digital pressure sensors and 3D static elbow poses

Kinematic analy-sis, using reflective markers

Axial compression using a mechan-ical testing system

Results

Peak pressure location and centre of pressure shifted laterally

Mean and peak contact pressure significantly de-creased in medial compartment and increased in lateral compartment

No significant differ-ence in orientation of the elbow axis pre- and postoper-ative or between left and right

No significant differ-ence between im-planted and control limbs in supra-physiological load to failure.

Figure 4 The principles of sliding humeral osteotomy (right) and proximal abduction ulnar osteotomy (left): transfer of load bearing forces from the eroded medial to the healthy lateral compartment of the elbow joint.

a KYON AG, Zurick, Switzerlandb TATE Prosthesis: BioMedtrix, Boonton, NJ, USA




lacking at this moment but available sub-jective data (evidence based medicine level 5) suggest an improvement of limb func-tion up to one year after surgery, although mild lameness may persist. This conclusion was based on data obtained from two clini-cal centres where the TATE prosthesis was implanted in 39 cases (58). An evidence based medicine level 4a study evaluating the short-term outcome after total elbow replacement with the Iowa state design in dogs with severe osteoarthritis led to a sat-isfactory result in 80% of the dogs (n = 20) (59). The major complication rate for the TATE elbow system is 7.7% with a similar minor complication rate (58). Reported complication rates for the Iowa state design are 10% intra-operative complications and 20% postoperative complications (59). Po-tential complications of a total elbow re-placement are infection, luxation and frac-ture of the humeral condyle, fracture of the ulna and implant loosening (58, 59). The newest semi-constrained total elbow re-placement system is the Sirius prosthesisc. The implant consists of a cemented hum-eral component and a cementless radio-ulnar component that is secured to bone with screws (60). Further information about the clinical outcome and compli-cation rate of this Sirius system is scarce at the moment. More long-term clinical evaluation of the currently available sys-tems is required and further research into the development of new total elbow re-placement systems is underway (50).

The canine unicompartmental elbow (CUE®) arthroplasty systemd replaces parts of the eroded cartilage in the medial com-partment of the elbow joint with a synthetic plug on the ulna and a metal implant on the medial aspect of the humerus (60, 61). This unicompartmental technique has some conceptual advantages compared to the total elbow replacement techniques and the load-shifting osteotomies. First, CUE is designed to restore physiologic medial compartment loading as closely as possible. Secondly, CUE still allows supination and pronation of the radius and ulna in contrast to total elbow replacement where a synos-

tosis is created between the radius and ulna. Third, CUE implantation can be done without violation of the collateral ligaments which may decrease the likelihood of post-operative complications such as joint lu-xation. The CUE also allows several strat-egies for revision in case of complications (61). Preliminary results from a clinical study (evidence based medicine level 5) in-volving 22 dogs demonstrate good or ac-ceptable outcome after follow-up of more than six months, based on subjective as-sessment of lameness (60). An important limitation of the CUE technique is that only a portion of cartilage is resurfaced. If the cartilage of the lateral compartment is also damaged or the area of resurfacing is insufficient, such that bone-on-bone con-tact still occurs, the dog may suffer persist-ent pain (61). Also, objective data about the long-term outcome and complication rate of this procedure are lacking.

A recent ex vivo study reported another type of medial compartment elbow arthro-plasty system (62). The ulnar component of this medial unicompartmental elbow pros-thesis replaces the cartilage of the MCP, the trochlear notch and the medial part of the anconeal process of the ulna, thus replacing a larger area of the cartilage of the medial compartment than the CUE (62). However, no data are available concerning clinical use and outcome of this type of prosthesis.

Elbow arthrodesis is a salvage procedure that has been abandoned by many sur-geons since this complicated surgery leaves a substantial mechanical lameness (63). However, in case of failure of other tech-niques, arthrodesis of the elbow joint might be the only option left (58).

Sensory denervation of the elbow has been proposed as a possible future treat-ment method for painful degenerated elbow joints. Similar to the hip, dener-vation of the elbow has been hypothesized to relieve pain. An evidence based medi-cine level 5 study in four normal dogs dem-onstrated no sensory or motor deficits of the forelimb after sensory elbow dener-vation (64). Clinical studies have not been performed so far.

PrognosisThe prognosis for patients with severe ero-sion of the medial compartment is guarded because of the limited regeneration capac-ity of cartilage.

The surgical load bearing transferring techniques are promising treatment meth-ods. Unfortunately, the level of evidence for the success of all these procedures is low. Sufficient information on complication rates and long-term clinical and objective follow-up are still lacking. Also the risk of developing lateral compartment erosions after these procedures has to be examined before routinely applying these techniques.

The prognosis after total elbow replace-ment is also questionable. Regardless of the design, a major disadvantage of total elbow replacement are the limited revision op-tions in case of failure (17, 62). Unfortu-nately, amputation of the leg in case of fail-ure is not an option in most dogs, since elbow dysplasia is typically a bilateral prob-lem.

Regardless of the applied therapy, the owners have to be informed accurately about the complication rate and prognosis in order to have realistic expectations.

Conclusion

Erosion of the medial compartment of the canine elbow is a complex problem which can present as a single lesion or a concomi-tant condition. Diagnosis is challenging be-cause erosion of the medial compartment does not generate pathognomonic clinical signs and the cartilage cannot be visualized using non-invasive medical techniques. Treatment of the extensive cartilage dam-age is challenging since the regeneration capacity of cartilage is limited. Despite a variety of therapies the ideal treatment has not yet been developed. Long-term follow-up studies and studies comparing different techniques may prove the value of cur-rently used techniques. In addition, re-search into the cause of the problem might lead to preventive measures.

c Osteogen Ltd., Bath, UKd Arthrex Vet Systems, Naples, FL, USA




Acknowledgements

Dr. Coppieters would like to thank the ‘Agency for innovation by science and tech-nology in Flanders’ (IWT) for funding her PhD research project and thereby making the realization of this paper possible.

Conflict of interest statement

None of the authors of this paper have a fi-nancial or personal relation with other people or organizations that could inappro-priately influence the content of the paper.

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Erosion of the medial compartment of the canine elbow: occurrence, diagnosis and currently available...

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