Radiographic changes of the patellar ligament in dogs after tibial tuberosity advancement

Patellar desmopathy in dogs after tibial plateau levelling osteotomy has been described in many studies. Tibial tuberosity advancement is a biomechanically different technique. It is assumed that the patellar ligament is loaded with little force similarly as after tibial plateau levelling osteotomy. Various aspects related to secondary patellar desmopathy are not completely understood. This study deals with computed radiography measurement of patellar ligament thickness after tibial tuberosity advancement in dogs with cranial cruciate ligament rupture. The thickness of the patellar ligament in exactly predetermined locations was measured from mediolateral radiographs of stifle joints. A total of 18 dogs (20 knee joints) with cranial cruciate ligament (ligamentum cruciatum craniale) rupture underwent three radiographic examinations of the knee (preoperative examination and control examination 7 and 15 weeks after the surgery). Significant difference was found between the thickness of the patellar ligament in the first and second examinations. Some of the demographic factors possibly related to patellar ligament thickness (age, sex, body weight, type of cranial cruciate ligament rupture, arthrotomy, cage size, meniscal injury, time between surgery and radiographic examination) were analyzed. However, statistical analyses did not show any effect of these factors on the thickness of the patellar ligament, except for the time between surgery and radiographic examination. These findings can extend the surgeons’ knowledge of biomechanical aspects of tibial tuberosity advancement. Computed radiography, ligamentum patellae, cranial cruciate ligament, TTA Cranial cruciate ligament (ligamentum cruciatum craniale, LCCr) disease is one of the most common disorders of the knee joint in the dog (Pacchiana et al. 2003). Disturbed integrity of the LCCr causes translational and rotational instability of the knee joint (Arnoczky and Marshall 1977). There are many surgical procedures to secure the stability of the knee joint with disrupted cranial cruciate ligament. All these methods can be divided into static or dynamic in accordance to the technique used (Boudrieau 2009; Kühn et al. 2011). Tibial plateau levelling osteotomy (TPLO) and tibial tuberosity advancement (TTA) are the most popular methods for dynamic stabilization of the stifle (Slocum and Slocum 1993; Montavon et al. 2002; Boudrieau 2009). Some studies were published about the patellar desmopathy after the TPLO procedure (Pacchiana et al. 2003; Carey et al. 2005; Boudrieau 2009). However, one study deals with the changes within the patellar ligament after the TTA (Kühn et al. 2011). The aim of this study was to determine the thickness of the patellar ligament in dogs after the TTA using computed radiography. Materials and Methods This retrospective study evaluated 20 knee joints of eighteen dogs treated surgically at the Department of Surgery and Orthopaedics, Small Animal Clinic, Faculty of Veterinary Medicine, University of Veterinary and Pharmaceutical Sciences Brno between April 2007 and September 2012. Inclusion criteria were surgically confirmed diagnosis of the LCCr rupture, series of radiographs of the affected knee joint and TTA stabilization of the affected knee joint. There were three radiographic examinations in each dog. The first radiographic examination was done right before the surgery (T0), the second examination in the 7th week (T1) and the third one in the 15th week (T2) after the surgery. ACTA VET. BRNO 2013, 82: 215–218; doi:10.2754/avb201382020215 Address for correspondence: MVDr. Ladislav Stehlík Department of Diagnostic Imaging Small Animal Clinic, Faculty of Veterinary Medicine University of Veterinary and Pharmaceutical Sciences Brno Palackého tř. 1/3,61242 Brno, Czech Republic Phone: +420 541 562343 Email: [email protected] http://actavet.vfu.cz/ The radiographic examination was done with the X-ray machine Proteus XR/a and cassettes for computed radiography. The digital radiographs were stored in the DICOM format using computed radiography system Capsula XL (Fuji, Japan). Resolution of the radiographs was 1770 × 2370 and 1576 × 1976, respectively. Two orthogonal views of the stifle joint were made using the table top technique. The mediolateral projection was used for the measuring of the patellar ligament thickness. The thickness was measured in three different predetermined points within the patellar ligament (Plate III, Fig. 1). The first point of measurement was located 1 cm distally to the distal patellar apex (PV1), the second was located in the middle of the patellar ligament (PV2) and the third point was located 1 cm proximally to the patellar ligament attachment (PV3). To avoid some discrepancies because of different size of joints, and to correct the magnification, the ratios of each particular thickness and the length of the patellar ligament were calculated. These ratios were used for all the calculations within this study. Medical records of all the included dogs were searched for some demographic data (age, sex, body weight, type of LCCr rupture, arthrotomy, cage size, meniscal injury, time between surgery and radiographic examination). All the statistical analysis was done with commercial software Minitab (Minitab Inc., Coventry, UK). To compare the measurements between each control a Wilcoxon test for paired data was used. The effect of the categorical variables (sex, type of LCCr rupture, arthrotomy, cage size, meniscal injury, time between surgery and radiographic examination) or continuous variables (age, weight) on the measured values was analysed by multivariate ANOVA (MANOVA).