Accuracy and safety of pin placement during lateral versus dorsal stabilization of lumbar spinal fracture-luxation in dogs.

OBJECTIVE: To determine the accuracy and safety of pin placement for lateral vertebral stabilization to the reference dorsal stabilization. STUDY DESIGN: A randomized noninferiority trial. SAMPLE POPULATION: Twenty Greyhound cadaveric lumbar spines (L1-L6). METHODS: One hundred and fifty-nine lumbar vertebral pins placed in 80 vertebrae were assessed; these pins were distributed approximately equally between the dorsal and lateral approaches, and between 2 surgeons. Pin angle accuracy, bone purchase distance, and distances from pin to the spinal canal and the aorta were measured for each pin. RESULTS: The lateral approach was superior for pin angle accuracy and bone purchase. The mean angle of deviation was 15.3° with the dorsal approach and 7.0° with the lateral approach. The mean bone purchase was 16.7 mm with the dorsal approach and 22.2 mm with the lateral approach. Pins were placed at a mean of 2.3 mm from the spinal canal with the dorsal approach and 1.7 mm with the lateral approach. Pins were placed at a mean of 3.8 mm from the aorta with the dorsal approach and 8.0 mm with the lateral approach. The percentage of pins breaching the spinal canal was 14% with the dorsal approach and 19% with the lateral approach. Fourteen percent of pins placed via the dorsal approach breached the aorta, whereas no pins placed via the lateral approach breached the aorta. CONCLUSION: Relative to the dorsal approach, the lateral approach improves angle accuracy, bone purchase, and distance between pins, and the aorta and is noninferior with regards to the distance between pins and the spinal canal.

Bending strength and stiffness of canine cadaver spines after fixation of a lumbar spinal fracture-luxation using a novel unilateral stabilization technique compared to traditional dorsal stabilization.

OBJECTIVE: To 1) assess the bending strength and stiffness of canine cadaver spines after fixation of a lumbar spinal fracture-luxation using a novel unilateral stabilization technique with pins and polymethyl methacrylate (PMMA) and 2) compare the results to a reference standard dorsal pin and PMMA technique. STUDY DESIGN: A randomized non-inferiority trial. SAMPLE POPULATION: Cadaveric lumbar spines (L1-L6) from 20 Greyhounds. METHODS: Specimens were paired to match bodyweight and vertebral size. A standardized fracture/luxation was performed between L3 and L4. One spine within each pair was randomly assigned the unilateral fixation technique and the other received the reference standard dorsal fixation technique. Four-point bending of each specimen in flexion was performed by applying load to pins placed transversely into vertebrae L1, L2, L5, and L6. During testing, angular bending strength and stiffness were measured as a function of flexion angle. Margins for non-inferiority were defined a priori. Strength and stiffness of the specimens for each technique were compared statistically. RESULTS: Lower limits of 95% confidence intervals were above the defined margins for non-inferiority. Thus, based on these margins, for strength and stiffness, unilateral fixation was not inferior to dorsal fixation. CONCLUSIONS: This novel unilateral approach to lumbar spinal fixation yielded comparable strength and stiffness when tested for bending in flexion to that of reference standard dorsal approach. This approach is therefore a suitable alternative to the dorsal approach in appropriate lumbar spinal fracture configurations.

Implantation of the VentrAssist Implantable Rotary Blood Pump in sheep.

The VentrAssist Implantable Rotary Blood Pump (IRBP) is a hydrodynamically suspended, electromagnetically driven, centrifugal blood pump that provides continuous flow of up to 10 L/min at 3,000 rpm. In vivo studies in sheep were conducted to assess system design and performance. Surgery involved thoracotomy with subdiaphragmatic pump placement. Cannulae were transdiaphragmatic, with inflow in the left ventricular apex and outflow anastomosed to the descending aorta. Animals had no anticoagulation or antiplatelet therapy after surgery and no prophylactic antibiotics after recovery. Twelve sheep were supported for 622 pump days. Estimated pump flow ranged from 1 to 5.5 L/min at 1,800 to 2,000 rpm using 2.5 to 4.5 W. There was no clinical evidence of hemolysis or cardiovascular, renal, or hepatic dysfunction. Adverse outcomes included kinking/disconnection of the outflow cannula caused by the graft bend relief (n = 4), which was addressed through cannula redesign. Pump electrical malfunction (n = 4), caused by a silicone potting compound, was corrected using a neutral curing potting material. Surgical/husbandry issues (n = 2) also were addressed. The VentrAssist IRBP provides high flow at low rotational speed and power consumption. Further trials are in progress in advance of in vivo studies of the safety and efficacy of the final system.