Measuring Craniocaudal Instability in Stifle Joints of Dogs Using Stress Radiographs

Abstract

Zatloukal J . , Neaas, A. , Dvofiak, M: Measuring Craniocaudal Instability in Stifle Joints of Dogs Using Stress Radiographs. Acta Vet. Brno 2000, 69: 311-317. Craniocaudal stifle joint laxity in dogs affected by various stifle disorders was determined using mediolateral X-ray projections of the stifle joint in neutral and tibial compression stress position. In all, 129 stifle joints of 80 dogs were included in the study. Patients were classified into following groups characterised by: 1) total cranial cruciate ligament (CCL) rupture, 2) total CCL rupture and medial meniscus lesion, 3) partial CCL rupture, 4) partial CCL rupture and medial meniscus lesion, 5) clinically evident CCL rupture only, 6) normal stifle joints, 7) normal stifle joint on the contralateral joint to the one affected by the CCL rupture, 8) radiographically abnormal and clinically stable stifle contralateral to the joint affected by the CCL rupture, and 9) other stifle disorders. Index of laxity (IL) of the stifle joint giving the extent of cranial tibial displacement relative to the femur in the stress tibial compression projection expressed as percents of the femur width was computed. Stifle joints with IL values over 25 can be supposed to be affected by CCL rupture, whereas joints with the IL value less than 15 can be considered to have an intact cranial cruciate ligament. There were significantly higher IL values in stifle joints with clinically or by arthrotomy diagnosed CCL rupture as compared to the group of healthy joints (Wilcoxon’s test; p < 0.01 and p < 0.05, respectively in these ones with partial CCL rupture and medial meniscus damage). Contrary to published data, we found considerably higher IL values in stifle joints with total CCL rupture as compared to those ones with partial rupture (p < 0.01). Significant differences in the index of laxity value were not found in stifles with other disorder than the CCL rupture as compared to the group of healthy joints. Measurement of the index of laxity is an undemanding and noninvasive technique supplementing the clinical examination and could serve as an early diagnostic method for the CCL injury. Index of laxity, stifle joint, cranial cruciate ligament, rupture, tibial compression test Disorders of the stifle joint in dogs are relatively frequent (Johnson et al. 1994). Craniocaudal instability of the stifle joint is mainly associated with the cranial cruciate ligament rupture (CCL). This instability is diagnosed clinically by the cranial drawer sign and tibial compression test and is mainly pathognomonic for the CCL rupture (Arnoczky 1993). It is more difficult to diagnose cases of chronic stifle joint affection with periarticular fibrosis or partial CCL rupture, when even in sedation of the patient, the clinically detectable instability is small or non-conclusive (Tarvin and Arnoczky 1981, Scavel l i et al. 1990, Strom 1990, de Rooster and van Bree 1999a). The diagnosis of the CCL rupture in these cases is based on ruling out other causes of lameness due to the stifle joint disorder. It may be necessary to directly evaluate the integrity of the cranial cruciate ligament using arthroscopy or arthrotomy (Mil ler and Presnel l 1985). Radiographic examination of the stifle joint in neutral projections shows in cases of CCL rupture only nonspecific changes such as arthrosis and effusion in the stifle joint. It is only in exceptional ACTA VET. BRNO 2000, 69: 311–317 Address for correspondence: MVDr. Josef Zatloukal Department of Diagnostic Imaging, Small Animal Clinic University of Veterinary and Pharmaceutical Sciences Palackeho 1-3, 612 42 Brno, Czech Republic, Phone: +420 602 51 14 28 Fax: +420 5 4156 2344 E-mail: zatloukalj@vfu.cz http://www.vfu.cz/acta-vet/actavet.htm