TMTJ Spurs require intraarticular analgesia to confirm clinical significance.

Clinical significance of osseous spurs on the dorsoproximal aspect of the third metatarsal bone

A Fairburn, S Dyson, R Murray

Background
Osseous spurs on the dorsoproximal aspect of the third metatarsal bone (MtIII) are common findings in horses; however, their clinical significance, particularly in relation to lameness, distal tarsal joint pain, and proximal suspensory desmitis (PSD), remains unclear. The study aimed to verify the anatomical sites of insertion for specific tendons and ligaments to distinguish osteophytes and entheseophytes radiologically and assess the frequency and associations of these spurs in different clinical groups.

Methods
A retrospective analysis of 455 horses with tarsal radiographs was conducted. Horses were categorized into five groups: clinically normal (Group 1) and those with hindlimb lameness caused by PSD, distal tarsal joint pain, or other conditions (Groups 2–5). Radiographs were evaluated for the presence, characteristics, and orientation of osseous spurs. Statistical associations were analyzed between spur presence and lameness, diagnostic groups, and radiological grades of distal tarsal joint abnormalities. Dissections of two cadaveric tarsi were performed to confirm insertion sites of tendons and ligaments.

Results
Osseous spurs were observed in 25% of horses, with 13% having bilateral spurs. There was no significant association between spur presence and lameness or specific diagnostic groups. However, spurs were significantly associated with higher radiological grades of abnormalities in the tarsometatarsal (TMT) and centrodistal (CD) joints. Spurs were predominantly located on the dorsal or dorsolateral aspect of MtIII. The study could not reliably differentiate osteophytes from entheseophytes due to overlapping insertion sites of the tibialis cranialis, fibularis tertius tendons, and the dorsal metatarsal ligament.

Limitations
The study was retrospective and single-point, with no follow-up to assess progression of spurs or development of lameness over time. Additionally, the generalizability to the wider horse population is limited due to the study's referral-based sample. Radiographs were assessed by a single analyst, and the study did not evaluate clinical outcomes directly linked to observed spurs.

Conclusions
Osseous spurs on the dorsoproximal aspect of MtIII are often incidental findings with no strong correlation to lameness but may indicate osteoarthritis (OA) in the distal tarsal joints. Their clinical significance must be confirmed with intra-articular analgesia. Long-term prospective studies are needed to elucidate the progression and relevance of these spurs in the context of joint health and performance.

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