Clinical history A 10 year old castrated male golden retriever presented with a chronic history of mild intermittent lameness - he has been physically active during his life. On palpation, both feet have firm swelling around the MCP joints that are not painful but crepitus is suggested in some digits. DP radiographs were made of both feet. What is your diagnosis? Both front feet Both front feet Radiographic changes The major injury involves the MCP joints of the 3rd and 4th digits and the adjacent MC bones and phalanges. The joint spaces are well identified but there is a suggestion of flattening of the subchondral bone and narrowing of the joint spaces. Heavy periosteal new bone (enthesophytosis) with uniform bone density and smooth margins involves the affected digits - note the almost complete involvement of the first phalanx of the 3rd digit - the presence of the periosteal response is superimposed over the cortices and makes them appear modeled without an endosteal surface - the superimposed periosteal new bone makes the trabecular bone in distal MC 3/4 appear increased in density with a new pattern of cancellous bone. The associated proximal sesamoid bones are difficult to evaluate but are not fragmented or malformed. The carpal bones and associated joints are within normal limits. Radiographic diagnosis
- The bony changes are benign is appearance with a symmetry between digits and feet
- Nothing suggests old malunion fractures especially involving the proximal sesamoid bones
- Changes in the joint spaces are minimal and chronic appearing and appear secondary
- No destructive changes in either bones or joints would suggest inflammatory or infectious disease
- The involvement of multiple bones in several digits with marked symmetry plus the absence of destructive lesions rules out primary or secondary bone tumors
- Failure to involve the 2nd and 5th digits tends to rule out metabolic or nutritional disease
- The pattern of new bone response follows the insertion of the soft tissues of the MCP joints (enthesophytes) including the
- Joint capsule
- Collateral ligaments
- Intersesamoidean, lateral and medial sesamoidean, distal sesamoidean, and cruciate ligaments of the sesamoid bones
- Interosssus muscles plus the digital flexors and extensors
- and suggests chronic injury to these anatomical structures
Comments It is suggested these changes be considered the result of chronic, repetitive injury with benign bony response (a chronic post-traumatic periostitis/enthesophytosis) - the minimal involvement of the joints perhaps suggests another term (a chronic post-traumatic arthrosis). An interesting feature is the difference between the feet of this dog with injury to the 3rd and 4th digits and those dogs with injury centered on the 2nd and 7th sesamoid bones that may have a similar pattern of periosteal response around the MCP joints of the 2nd and 5th digits.
