CASE DESCRIPTION 4 horses were examined because of signs of chronic hind limb lameness.
CLINICAL FINDINGS 3 horses had a history of lameness for > 6 months; specific duration was unknown for 1 horse. On initial evaluation, grade 3 to 4 (on a scale from 1 to 5) hind limb lameness was present in all 4 horses. Radiography of the stifle joint of the affected limb revealed medial femoral condyle subchondral lucencies or subchondral cystic lesions (SCLs) in all 4 horses, medial femorotibial osteoarthritis in 3 horses, and medial tibial condyle SCLs in 3 horses.
TREATMENT AND OUTCOME 2 horses were treated medically (stall rest and oral NSAID administration), and 2 horses were treated surgically by means of medial femoral transcondylar lag screw placement through the medial femoral condyle SCLs. The 2 horses treated medically did not improve and were euthanized. Necropsy confirmed the presence of medial femoral condyle and medial tibial condyle SCLs. Surgical treatment did not resolve the lameness in 1 horse with SCLs in the medial tibial condyle and medial femoral condyle, and euthanasia was performed 150 days after surgery. In the second horse, a medial tibial condyle SCL was evident on radiographs obtained 3 months after surgery; however, this was not addressed surgically, and signs of lameness resolved 11 months after surgery.
CLINICAL RELEVANCE Results of this small case series suggested that SCLs in the medial tibial condyle can occur in association with SCLs of the medial femoral condyle, with a poor prognosis for return to athletic function in affected horses. Further investigation is indicated.
To investigate the effects of triamcinolone acetonide (TA) and methylpredniso-lone acetate (MPA) on the viability of resident cells within the fibrocartilage on the dorsal surface of the deep digital flexor tendon (FC-DDFT) and fibrocartilage on the flexor surface of the navicular bone (FC-NB) of horses.
12 to 14 explants of FC-DDFT and of FC-NB from grossly normal forelimbs of 5 cadavers of horses aged 9 to 15 years without evidence of musculo-skeletal disease.
Explants were incubated with culture medium (control) or TA-supplemented (0.6 or 6 mg/mL) or MPA-supplemented (0.5 or 5 mg/mL) medium for 6 or 24 hours. Explant metabolic activity and percentage of dead cells were assessed with a resazurin-based assay and live-dead cell staining, respectively, at each time point. Drug effects were assessed relative to findings for the respective control group.
Application of TA (at both concentrations) did not significantly change the cell viability of FC-DDFT explants. For FC-NB explants, TA at 6 mg/mL significantly reduced the metabolic activity and increased the percentage of dead cells at both time points. With either MPA concentration, FC-DDFT and FC-NB explants had reduced metabolic activity and an increased percentage of dead cells at 24 hours, whereas only MPA at 5 mg/mL was cytotoxic at the 6-hour time point.
CONCLUSIONS AND CLINICAL RELEVANCE
In ex vivo explants, TA was less cytotoxic to equine FC-DDFT and FC-NB cells, compared with MPA. Further work is warranted to characterize the drugs' transcriptional and translational effects as well as investigate their cytotoxicity at lower concentrations.