Introduction: Injury of cranial cruciate ligament (CCL) is common causes of osteoarthritis (OA) of the stifle joint in dogs. The early diagnosis of CCL disease is very important for the prevention of complete rupture of CCL and secondary OA. Expression of tartrate-resistant acid phosphatase (TRAP) within the CCL during injury has an important role in CCL resorption and influence the success of reconstructive surgery. The purpose of this study was to investigate the concentration of TRAP in synovial fluid of normal stifle joint in order to suggest a data for comparison with that obtained incase of injury of CCL and osteoarthritis.

Materials and Methods: 23 mixed breed healthy dogs (14 adult and 9 young) without CCL disease were used in this study. Synovial fluid was collected from the femoropatellar compartment of the stifle joints by direct arthrocentesis. The concentration of TRAP in stifle joint synovial fluid was determined using a biochemical assay in 96-well plates, with pnitrophenylphosphatase (pNPP) as s substrate. Acid phosphatase was used as a standard for calculation of the concentration of the TRAP within each sample.

Results: Age--The concentration of TRAP in adult dogs was higher, 0.083±0.039 IU/mL (Mean±SD) in comparison to that in the young dogs, 0.064±0.023 IU/mL. But this difference was not statistically significant. Body weight--The concentration of TRAP in the larger dogs (weight > 22 kg), 0.075±0.028 IU/mL and that in the smaller dogs (weight < 22 kg) 0.076±0.046 IU/mL were almost equal. Sex--The concentration of TRAP in the neutered dogs, 0.085±0.036 IU/mL was significantly (p<0.05) higher when compared to that in the intact dogs, 056±0.022 IU/mL.

Discussion and Conclusion: The dogs weighing more than 22kg reported to have a higher risk of CCL injury. The prevalence of injury to the CCL is higher in neutered dogs of both sexes when compared to that in the intact dogs. A significant difference in the concentration of TRAP in synovial fluid between neutered and intact dogs of both sexes was observed in our study. Why this difference occurs is not clear, but it might be due to the rapid weight gain and changing in the endocrine system following their neutralization. The early diagnosis of some CCL diseases such as partial rupture or tear are difficult because of the absence of obvious clinical signs and lameness. Radiographs are also equivocal. However, in such cases measurement of the concentration of TRAP in synovial fluid might play an important role in their diagnosis and treatment.

References

1.  Duval JM, Budsberge SC, Flo GL, et al . Breed, sex, and body weight as risk factors for rupture of the cranial cruciate ligament in young dogs. J Am Vet Med Assoc 1999;215: 811-814

2.  Johnson KA, Hay CW, Caterson B. Cartilage-derived biomarkers of osteoarthritis in synovial fluid of dogs with naturally acuired rupture of the cranial cruciate ligament. VJVR 2002;63:775-781