Evaluation of the relationship of tibiofemoral kinematics before and after total knee replacement in an in vitro model of cranial cruciate deficiency in the dog.

OBJECTIVE: To investigate the relationship between tibiofemoral kinematics before and after total knee replacement (TKR) in vitro. ANIMALS: Eight canine hemipelves. METHODS: A modified Oxford Knee Rig was used to place cadaveric limbs through a range of passive motion allowing the kinematics of the stifle to be evaluated. Four measurements were performed: a control stage, followed by a cranial cruciate transection stage, then following TKR with the musculature intact stage, and finally TKR with removal of limb musculature stage. Joint angles and translations of the femur relative to the tibia, including flexion-extension versus adduction-abduction, flexion-extension versus internal-external rotation, as well as flexion-extension versus each translation (cranial-caudal and lateral-medial) were calculated. RESULTS: Significant differences were identified in kinematic data from limbs following TKR implantation as compared to the unaltered stifle. The TKR resulted in significant decreases in external rotation of the stifle during flexion-extension compared to the limb prior to any intervention, as well as increasing the abduction. The TKR significantly increased the caudal translation of the femur relative to the tibia compared to the unaltered limb. When compared with the cranial cruciate ligament-transection stage, TKR significantly decreased the ratio of the external rotation to flexion. DISCUSSION: All three test periods showed significant differences from the unaltered stifle. The TKR did not completely restore the normal kinematics of the stifle.

Correlation of near-infrared spectroscopy and direct pressure monitoring in an acute porcine compartmental syndrome model.

OBJECTIVE: To correlate near-infrared spectroscopy (NIRS) and the tibial intracompartmental perfusion pressure (TIPP) in an acute limb compartmental syndrome. METHODS: Landrace swine were subdivided into 2 groups: plasma infusion (n = 16) and blunt trauma plus plasma infusion (n = 15). NIRS sensors were placed over the craniolateral muscle compartment of proximal both tibiae. Albumin infusion elevated tibial intracompartmental pressures (TICP). Time-synchronized measures of systolic, diastolic, and mean arterial pressures, TICP, and percent oxygenation from each leg were collected. For the blunt trauma group, trauma was induced by dropping a 2-kg weight 30 times from 100 cm directly on the muscle compartment. For each group, a repeated-measures analysis of variance model was used to test differences in the TICP, TIPP, and oxygenation values. Pearson correlations were calculated between TICP and oxygenation and between TIPP and oxygenation. RESULTS: Both models created reproducible increases in TICP and decreases in TIPP. Trauma did not alter TICP, TIPP, or percent oxygenation in the model. NIRS was able to detect significant changes in tissue oxygenation at all the same time points. NIRS was able to detect decreased oxygenation at every TIPP decrease and subsequent increase after fasciotomies. An increase in percent oxygenation was seen in all cases once fasciotomy was performed and TICP was reduced. CONCLUSIONS: NIRS provided a sensitive measure correlating to both an increase and decrease in TICP and TIPP, respectively, in this infusion model. The addition of blunt trauma to the model did not alter the correlations of NIRS values with TICP and TIPP. Fasciotomy produced a rebound in oxygenation values.