Role of the Quadriceps Muscle in a Cranial Cruciate Ligament Deficient Stifle: A Pilot Study

Introduction
Quadriceps muscles-tendon unit (QMtu) has been proposed to be antagonistic to the cranial cruciate ligament (CrCL) in dogs1. application of tension in the QMtu could trig- ger the cranial tibial thrust (Crtt) in case of CrCL rupture.
objective: to evaluate the effect of pre-tension applied in the QMtu on the magnitude of Crtt after CrCL rupture.

Materials and Methods
The QMtu and the Gastrocnemius muscles/ achilles tendon unit (GMatu) were replaced by a strain gage and a turn-buckle.
Eight adult dogs left limbs were placed in a servo-hydraulic testing machine, applying 50% of body weight (BW) in a first phase. Limbs were then tested after CrCL transection and after CrCL transection and pre-tension of 15% BW applied in the QMtu, prior to loading the limbs.
Stifle and hock angles were measured using a goniometer. plain radiographs were taken in order to measure Crtt. forces in both QMtu and GMatu were recorded via data log- ger and acquisition software.
Limbs were divided in 2 groups: tibial plateau angle (tpa)< 23° and tpa > 23°. a com- parison between these groups was conducted by means of a one way anoVa. relation- ship between tpa, Crtt and other parameters measured in the same limb was studied by means of pearson correlation

Results
After pre-tension in QMtu, limbs with tpa > 23°, had significantly higher Crtt than limbs with tpa ≤ 23°
Higher forces were recorded in the QMtu of the limbs with CrCL rupture compared to CrCL intact and CrCL rupture and pre-tension limbs (p<0.05).

Conclusion
Pre-tension in QMtu seemed to reduce Crtt upon loading of the limb after CrCL transection. this beneficial effect seemed more pronounced in limbs with tpa ≤ 23.