Angela Palumbo Piccionello, Luca Pennasilico, Adolfo Maria Tambella, Sara Sassaroli, Margherita Galosi, Nicola Pilati, Fabrizio Dini
Background
Cranial cruciate ligament (CCL) rupture leads to stifle instability in dogs and is commonly treated surgically via tibial plateau leveling osteotomy (TPLO). Although highly successful, TPLO is associated with postoperative patellar ligament thickening and desmopathy. These changes are suspected to arise from altered biomechanics and increased ligament loading. Prior studies report radiographic thickening and ultrasonographic abnormalities, but their mechanical significance, particularly elasticity changes measurable by elastosonography, is less understood. This study evaluates structural and mechanical alterations in the patellar ligament before and up to six months after TPLO.
Methods
This prospective clinical study enrolled 22 dogs (20–50 kg) with unilateral complete CCL rupture undergoing TPLO. Radiographic, ultrasonographic, and real-time strain elastosonographic assessments were performed preoperatively (T0) and at 1 month (T1), 2 months (T2), and 6 months (T3) postoperatively. Patellar ligament thickness was measured at proximal, central, and distal points and normalized to tibial width. Ultrasound scoring assessed echogenicity and fiber architecture (0–3). Elastosonography quantified hardness (HRD%) and softness (SFT%) of the ligament. Statistical analyses included repeated-measures ANOVA, Friedman tests, Dunn's post hoc tests, and Spearman correlation.
Results
Radiographic and ultrasonographic measurements showed significant postoperative thickening of the patellar ligament at all evaluated points compared to T0. Thickening was greatest distally at T2 and T3. Ultrasound grading revealed moderate abnormalities (score 2) in 82% of ligaments at T1 and T2, with partial improvement by T3. Elastosonography demonstrated a marked increase in ligament hardness and reduction in softness at all postoperative times, with partial softening at T3 but without return to baseline. Radiographic and ultrasonographic thicknesses correlated strongly, but neither correlated with elastosonographic hardness or softness. Hardness and softness values were inversely correlated.
Limitations
Limitations include the absence of histological or mechanical tissue validation, which was not feasible in clinical patients. Elastosonography lacked semiquantitative strain ratios relative to surrounding tissues. Measurements of elasticity were performed over the entire ligament rather than at regional segments. The stifle position used (maximal passive flexion) may differ from positions identified as optimal in prior studies. Additionally, fixed measurement distances for ligament thickness may not fully account for differences in patient size.
Conclusions
TPLO induces persistent structural and mechanical alterations in the patellar ligament, including increased thickness and reduced elasticity, detectable up to six months after surgery. Radiography and ultrasonography provide concordant assessments of ligament thickening, whereas elastosonography reveals biomechanical changes that do not correlate with structural measurements. Clinical monitoring—including imaging and potentially rehabilitation—may help identify or mitigate postoperative ligament desmopathy in TPLO patients.
Mediolateral radiographic view of the stifle before the surgery. The thickness of the patellar was evaluated at three points: proximal, central and distal (white arrows). The proximal point was established one centimeter distally to the base of the patella (green line), the distal point was established one centimeter proximally to the tibial tuberosity (green line) and the central point was halfway between the first two points previously described (red cross).
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