Canis ISSN: 2398-2942

Elbow: medial coronoid process disease (MCPD)

Synonym(s): FMCP, FCP, fragmented coronoid process

Contributor(s): Prof Walter Renberg, Neil Burton

Introduction

  • Most common cause of elbow lameness in young rapidly growing dogs of large and giant breeds.
  • Was initially thought to be a form of osteochondrosis but much work more recently has refuted this.
  • Can co-exist with ununited anconeal process (UAP Ununited anconeal process ) or osteochondrosis dissecans of the humeral condyle (OCD Elbow: osteochondritis dissecans ) - likely inherited predisposition.
  • Cause: currently controversial and incompletely understood. Some dogs appear to have axial incongruency of the radius and ulna and a short radius has been associated with changes to the medial coronoid process on CT and arthroscopy. In addition some dogs appear to have an arc of curvature of the ulnar trochlear that differs to that of the trochlear of the humerus - this may overload both the medial coronoid process and anconeal process causing MCPD and UAP concurrently. However, some dogs do not have incongruency at the time of presentation so the precise contribution of incongruency in the pathogenesis of MCPD is uncertain. 
  • Signs: progressive, uni- or bilateral forelimb lameness from 4-5 months of age, abnormal gait ('duck-footed'), pain on full elbow extension and/or full flexion of the elbow with concurrent supination of the antebrachium, effusion, thickened joint(s).
  • Treatment: remains controversial. Options include: conservative/medical management; excision of fragmented coronoid arthroscopically or by conventional surgery; proximal ulna osteotomy to redistribute load on site, if medial compartment disease is present proximal abducting ulnar osteotomy (PAUL) or sliding humeral osteotomy (SHO) can be considered. If end stage joint disease is present elbow replacement may be indicated. There are a lack of prospective, objective studies comparing outcomes of these treatments making precise recommendations in each case challenging.
  • Prognosis: difficult to predict - many cases remain lame and almost all continue to develop degenerative joint disease (DJD Arthritis: osteoarthritis ).
Medial coronoid process disease (MCPD) was previously known as fragmented medial coronoid process (FMCP) but has been renamed as we now appreciate a range of changes affecting the medial coronoid process rather than just fragmentation per se.Use the interactive tool from ROYAL CANIN® UK  to explain dog anatomy and disease conditions to your client. Visit ROYAL CANIN Natom Explorer to find out more.​

Pathogenesis

Etiology

  • Likely inherited predisposition but specific candidate genes yet to be defined.
  • Abnormal shearing forces (usually resulting from abnormal skeletal development), applied to coronoid process may contribute to the development of the lesion (elbow incongruity) but this does not appear to be present in every case.

Pathophysiology

  • Elbow incongruence secondary to asynchronous development of radius and ulna, resulting in relative overgrowth of ulna/abnormal development of trochlear notch of ulna.
  • One or more fragments of bone may fracture from inner aspect coronoid process immediately adjacent to humeral head/apex coronoid process. Equally some dogs have non-displaced fissures and some have no fragmentation. Due to this spectrum of changes affecting the medial coronoid process, medial coronoid process disease (MCPD) rather than fragmented medial coronoid process is a more accurate description of the lesion.
  • Fragments, when present, usually remain attached to annular ligament.
  • Fragments may project from articular surface causing erosion ('kissing lesion'), of adjacent humeral condyle. Equally, these humeral lesions may be caused by the incongruence that may be present in the joint.
  • Coronoid may remain attached to surrounding cartilage (rare) - affected cartilage thicker (whiter), than normal, underlying bone may be fractured.
  • Other lesions: chondromalacia and fissures of coronoid process, erosion of articular cartilage in trochlear notch, OCD of distal humeral condyle.
  • End result: DJD Arthritis: osteoarthritis.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Gemmill T J, Mellor D J, Clements D N, Clarke S P, Farrell M, Bennett D & Carmichael S (2005) Evaluation of elbow incongruency using reconstructed CT in dogs suffering fragmented coronoid process. JSAP 46 (7), 327-333 PubMed.
  • Hornof W J, Wind A P, Wallack S T & Schulz K S (2000) Canine elbow dysplasia. The early radiographic detection of fragmentation of the coronoid process. Vet Clin North Am Small Anim Pract 30 (2), 257-266 PubMed.


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