Working Algorithm for Treatment Decision Making for Developmental Disease of the Medial Compartment of the Elbow in Dogs

Veterinary Surgery 38:285–300, 2009 INVITED REVIEW Working Algorithm for Treatment Decision Making for Developmental Disease of the Medial Compartment of the Elbow in Dogs NOEL FITZPATRICK, MVB CertSAO CertVR and RUSSELL YEADON, MA VetMB INTRODUCTION treatments for a corresponding spectrum of pathologic change. Failure to understand and address underlying HERE IS disagreement about the manifestations of processes when treating overt pathology will almost in- Telbow pathology that should be included under the evitably lead to suboptimal outcome. Despite this lack of umbrella of elbow dysplasia. This is highlighted by vari- understanding, there is increasing recognition that joint able inclusion or exclusion of diseases like ununited me- incongruency is an important factor in the development dial epicondyle1 and elbow incongruity2 with the more of canine elbow disease, albeit in a more complex manner commonly recognized and historically grouped triad of (1) than initially proposed.2,11 Concurrently, it is important disease of the medial aspect of the coronoid process (me- to understand the utility and limitations of diagnostic dial coronoid disease; MCD); (2) osteochondrosis (OC) or methods (e.g. historical, clinical, imaging) for identification osteochondritis dissecans (OCD) of the medial humeral of pertinent disease characteristics. To the extent that these condyle; and (3) ununited anconeal process (UAP). Vari- diagnostic approaches define appreciation of disease and ations in grouping syndromes within elbow dysplasia thus direct treatment approaches, their precision has po- contributes to confusion among veterinarians and dog tentially profound implications for treatment outcomes. owners about the precise nature of disease involved. Finally, relevant outcome measures are critical to evaluate Whereas several diseases may coexist within the same the efficacy of treatment approaches for individuals and joint,3–5 it has become increasingly apparent from hist- across patient groups. Outcome measures provide a frame- omorphometric,6 biomechanical,2,7,8 and genetic or her- work for accumulation of clinical evidence and application itability9,10 data that there is considerable independence in the context of ‘‘evidence-based practice,’’12,13 and allow in development of these multifactorial disease processes. continued refinement of assumptions leading to progres- This is further complicated by the spectrum of clinical sive improvements in therapeutic strategies. signs and macroscopic pathology associated with any Thus, in considering this larger challenge—decon- single disease process,11 which has important implications structing currently used terminology, defining the etio- for treatment and prognosis. Clearly, there is no single pathogenesis of disease processes included in elbow treatment for all recognized manifestations of elbow dys- dysplasia, improving diagnostic tests, and developing plasia,soseemingly,theinitialstepindevelopingaclin- therapeutic strategies and outcome measures—we report ically useful decision-making algorithm is to deconstruct the decision-making algorithms currently in use in our this oversimplified nomenclature. practice for disorders involving the medial compartment A working understanding of the etiopathogenesis of of the canine elbow. These algorithms have been devel- these disease processes is needed to define and optimize oped from synthesis of current scientific foundations for From Fitzpatrick Referrals, Eashing, UK. Address reprint requests to Noel Fitzpatrick, MVB CertSAO CertVR, Fitzpatrick Referrals, Halfway Lane, Eashing, Surrey GU7 2QQ, UK. E-mail: noelF@fitzpatrickreferrals.co.uk. Submitted April 2008; Accepted October 2008 r Copyright 2009 by The American College of Veterinary Surgeons 0161-3499/09 doi:10.1111/j.1532-950X.2008.00495.x 285 286 TREATMENT ALGORITHM FOR DISEASE OF MEDIAL COMPARTMENT OF CANINE ELBOW this constellation of disorders, and interpreted and mod- for further decision-making, rather than simply to ified based on our clinical experience. Our purpose is to confirm a diagnosis of MCD. This is of particular stimulate dialog, highlight areas of needed investigation, significance because elbows affected by MCD can be and provoke continued refinement of our collective un- radiographically normal21 or may be affected by only derstanding through robust clinical trials and focused subtle subtrochlear sclerosis.22 Furthermore, degree of studies of mechanisms and pathogenesis of elbow disease. osteophytosis is considered of minimal benefit in deter- We recognize that our efforts in this and our accompa- mination of an appropriate treatment protocol as it is nying reports might generate controversy but anticipate poorly correlated with pathology subsequently identified that the framework we provide can serve as the founda- by direct joint inspection23,24 but has close associations tion for future improvements. with expression of cartilage genes.25 Other imaging techniques or diagnostic tests useful for exclusion of potential DISEASE OF THE MEDIAL ASPECT OF THE primary or concomitant pathologies (e.g. shoulder lesions, musculotendinous injuries, neurogenic lameness, CORONOID PROCESS or neoplasia) are selected based on clinical findings. In Diagnosis particular, diseases involving the shoulder joint and ad- jacent structures should be excluded as causes of thoracic Even when free fragmentation has been subsequently limb lameness.26 identified by arthroscopy or arthrotomy, identification of CT and more recently MRI scans are increasingly used disease of the medial aspect of the coronoid process to evaluate elbows where changes are equivocal on ra- (MCD) has historically proven challenging despite use of diographic assessment27; however, arthroscopic evalua- diverse imaging modalities including radiography2,14–17; tion constitutes the most important single interrogation computed tomography (CT)11,18;scintigraphy19;and directing our decision-making process for MCD with or magnetic resonance imaging (MRI).20 Typically, diagno- without pathology of the medial aspect of the humeral sis is based on identification of secondary markers of condyle. We have observed equivocal findings on both degenerative joint disease in the absence of other dis- CT and MRI where subchondral pathology was subse- cernable discrete pathologic changes. quently proven by histologic examination of coronoid We consider thorough clinical evaluation to be as im- specimens after arthroscopically identified MCD.28 A portant as subsequent diagnostic imaging techniques. spectrum of arthroscopic changes including fragmenta- Recognition of thoracic limb lameness can be relatively tion, cartilage fissures, chondromalacia, and cartilage insensitive because of the high incidence of bilateral dis- fibrillation affect the medial coronoid process (MCP) ease and because many younger dogs remain surprisingly and we consider these to be manifestations of a common mobile or behaviorally active despite severe elbow pa- underlying disease process.24,29 thology. We find that evaluation of discomfort caused by elbow manipulation is a strong indicator of disease in- Etiopathogenesis volving the medial compartment of the canine elbow. The most reproducible discomfort can be elicited on maximal Pathologic changes initially affect subchondral bone flexion, and particularly on firm supination of the ante- with formation of microcracks, characteristic of local brachium while the elbow is held in moderate flexion. fatigue failure.6 These changes typically occur at one of Response to deep digital pressure in the region of the two anatomic sites, either the craniodistal tip of the me- insertion of the bicep brachii muscle over the medial as- dial aspect of the coronoid process, or more axially ori- pect of the coronoid process is also a valuable indicator ented in the region of the radial incisure. Although the of potential disease. Positive responses to these tests precise nature of this fatigue phenomenon remains elu- alone, in the absence of any other identified source of sive, several hypotheses encompass the disparate range of lameness or pain, creates a high index of suspicion such recognized pathologic changes, all of which may be at- that diagnostic imaging is directed toward identification tributable to some form of humeroulnar conflict (HUC). of disease of the medial compartment of the elbow and Static Radioulnar Length Disparity. Characterized by more specifically MCD. If results of noninvasive imaging shortening of the radius relative to the ulna. This dispar- techniques are equivocal, we consider direct observation ity effectively exposes the coronoid process of the ulna to by arthroscopy or arthrotomy to be justified. increased load-bearing forces from the humerus through- Detailed radiographic examination of both elbows is out the full range of elbow movement. MCP disease essential before any intervention. This allows more de- has been identified by CT and arthroscopy in the absence tailed classification of the nature of disease (specifically, of overt static incongruity,27 so it seems unlikely that likely chronicity, radiographic severity of subchondral static incongruency plays a major role in some dogs,11 disease, and presence of OC lesions) that may be valuable although where definitively identified, MCD should be FITZPATRICK AND YEADON 287 considered a likely sequel. This form of incongruency Musculotendinous Mismatch. Rotational instability might be expected to result in pathologic change focused could occur as a secondary effect of musculotendinous

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