Assessment of the craniocaudal stability of four extracapsular stabilization techniques during two cyclic loading protocols: a cadaver study.

OBJECTIVE: To (1) compare the effect of cyclic loading on craniocaudal tibial translation in cranial cruciate ligament (CrCL)-deficient stifles after extracapsular stabilization, and (2) evaluate the effect of peak force during cyclic loading on the rate of development of craniocaudal laxity. STUDY DESIGN: Biomechanical cadaveric study. SAMPLE POPULATION: Cadaveric pelvic limbs (n = 24 pairs) from skeletally mature dogs. METHODS: Twenty-four pairs of stifles were randomly assigned to 4 stabilization groups: nylon leader lateral circumfabellar-tibial suture (NLS); FiberTape lateral circumfabellar-tibial suture (FTLS); TightRope (TR); or bone anchor (BA). Contralateral limbs were cyclically loaded to produce cranial tibial translation at peak forces of either 80 or 160 N. Craniocaudal displacement of the tibia was measured with a mechanical testing machine during cyclic loading with the CrCL intact, after CrCL transection, and after extracapsular stabilization. The number of cycles each construct underwent before reaching 200% and 300% of the mean craniocaudal displacement present during cyclic loading of the CrCL-intact stifles was calculated. Number of cycles among treatment groups was compared with a Kruskal-Wallis test. P < .05 was considered significant. RESULTS: Mean ± SD translation before and after CrCL transection were 3.9 ± 0.6 and 14.6 ± 1.7 mm, respectively. TR constructs resisted significantly more cycles than NLS constructs before reaching 7.8 mm (200%) and 11.7 mm (300%) of translation when loaded to 80 N. No other differences between constructs were significant at a peak load of 80 N. All constructs reached 7.8 and 11.7 mm of translation in fewer cycles when loaded to 160 N than at 80 N. CONCLUSIONS: TR constructs were most resistant to elongation during cyclic loading. Doubling the peak force during cyclic loading significantly decreased the number of cycles constructs withstood, supporting recommendations for restricting postoperative activity after extracapsular stabilization of the CrCL-deficient stifle.

Mechanical evaluation of adjunctive fixation for prevention of periprosthetic femur fracture with the Zurich cementless total hip prosthesis.

OBJECTIVE: To evaluate whether cerclage wire or a lateral plate increases the peak-torque load to failure, compared to femora without adjunctive fixation, in femora implanted with Zurich Cementless stems. STUDY DESIGN: In vitro biomechanical study. SAMPLE POPULATION: Paired femora from adult dogs (n = 24) weighing 28-35 kg. METHODS: Pairs of femora were implanted with a stem and randomly assigned to 2 treatment groups: cerclage or plate. Within each pair, either 3 loop cerclage wires or a laterally applied 12-hole Advanced Locking Plate System 10-mm plate (ALPS 10) were implanted in a femur, whereas the contralateral femur acted as control with no adjunctive fixation. After application of a static axial load each specimen was loaded to failure in torsion. Peak torque load at failure was compared between femora with each adjunctive fixation and the control using a paired t-test; P < .05 was considered significant. RESULTS: In both treatment groups, femora with adjunctive fixation failed at higher loads compared to the femora without fixation; however, significant difference in peak torque at failure between treated femora and control was found only in the plated group (P < .05). Femora implanted with plates and with cerclage were 13.9% and 7.2% stronger in torsion than the femora without fixation, respectively. CONCLUSIONS: Adjunctive fixation with a laterally applied ALPS 10 may aid in the prevention of peri-prosthetic fractures associated with Zurich Cementless medium stems.

Effect of lateral meniscectomy and osteochondral grafting of a lateral femoral condylar defect on contact mechanics: a cadaveric study in dogs.

BACKGROUND: Osteochondral autograft transfer (OAT) aims at restoring normal articular cartilage surface geometry and articular contact mechanics. To date, no studies have evaluated the contact mechanics of the canine stifle following OAT. Additionally, there are no studies that evaluated the role of the meniscus in contact mechanics following OAT in human or canine femorotibial joints. The objective of this study was to measure the changes in femorotibial contact areas (CA), mean contact pressure (MCP) and peak contact pressure (PCP) before and after osteochondral autograft transplantation (OAT) of a simulated lateral femoral condylar cartilage defect with an intact lateral meniscus and following lateral meniscectomy. RESULTS: With an intact lateral meniscus, creation of an osteochondral defect caused a decrease in MCP and PCP by 11% and 30%, respectively, compared to the intact stifle (p < 0.01). With an intact meniscus, implanting an osteochondral graft restored MCP and PCP to 96% (p = 0.56) and 92% (p = 0.41) of the control values. Lateral meniscectomy with grafting decreased CA by 54% and increased PCP by 79% compared to the intact stifle (p < 0.01). CONCLUSIONS: OAT restored contact pressures in stifles with a simulated lateral condylar defect when the meniscus was intact. The lateral meniscus has a significant role in maintaining normal contact pressures in both stifles with a defect or following OAT. Meniscectomy should be avoided when a femoral condylar defect is present and when performing OAT.

Mechanical properties of isolated loops of nylon leader material, polyethylene cord, and polyethylene tape and mechanical properties of those materials secured to cadaveric canine femurs via lateral femoral fabellae, toggles placed through bone tunnels, or bone anchors.

OBJECTIVE: To determine mechanical properties of various prosthetic materials secured to cadaveric canine femurs via various methods and to compare results with those for isolated loops of prosthetic material. SAMPLE: 80 femurs obtained from cadavers of skeletally mature large-breed dogs. PROCEDURES: 10 femoral constructs in each of 8 groups (single circumfabellar loop of polyethylene cord, double loop of polyethylene tape secured via a bone anchor [BAPT], single or double circumfabellar loops of nylon leader material [CNL] or polyethylene tape [CPT], or single or double loops of polyethylene tape secured via a toggle placed through a bone tunnel [BTPT]) and 10 isolated loops of prosthetic material in each corresponding configuration were tested. Stress relaxation, creep, elongation, load at 3 mm of displacement, stiffness, and peak load at failure were determined. RESULTS: 5 single CNL constructs failed before completion of testing. Double CNL and single circumfabellar polyethylene cord constructs had the lowest loads at 3 mm of displacement. Single and double CPT constructs had the highest stiffness. Double BTPT and CPT constructs had the highest peak loads at failure. Double BTPT, double CPT, and BAPT constructs were mechanically superior on the basis of lower creep and stress relaxation and higher stiffness and load at 3 mm of displacement versus other constructs. Stiffness of femoral constructs was 28% to 69% that of corresponding isolated prosthetic loops. CONCLUSIONS AND CLINICAL RELEVANCE: Double BTPT, double CPT, and BAPT constructs were mechanically superior to other constucts. Mechanical properties and methods of anchorage and securing of free ends of prostheses contributed to mechanical properties of constructs.

Occlusion of the thoracic duct using ultrasonically activated shears in six dogs.

OBJECTIVE: To assess the feasibility of sealing the thoracic duct (TD) in dogs using ultrasonically activated shears via thoracoscopy. STUDY DESIGN: In vivo experimental study. ANIMALS: Mature dogs (n = 6). METHODS: Dogs were anesthetized without pulmonary exclusion and positioned in left lateral recumbency. Lymphangiography was performed to identify TD anatomy. Methylene blue was injected into the lymphatic catheter to identify the TD and its branches. Under thoracoscopic guidance (right dorsal 8-10th intercostal spaces), the TD was sealed with an ultrasonic device and lymphangiography was repeated. If the flow of contrast continued beyond the occlusion site, additional attempts to seal the duct were made. Dogs were euthanatized, the TD was excised and fixed in formalin for histopathology. RESULTS: Thoracoscopic identification of the TD was possible in 5 dogs. Three dogs required conversion to a thoracoscopic-assisted approach and 3 dogs required resealing of the TD closer to the diaphragm. Thoracic duct occlusion (TDO) was ultimately achieved in all 6 dogs based on follow-up lymphangiography. TDO by tissue coagulation was confirmed by histopathology. CONCLUSIONS: Thoracoscopic identification and occlusion of the TD using ultrasonically activated shears with bilateral lung ventilation is technically feasible in normal dogs and provides a less invasive alternative to open thoracotomy procedures.

Comparison of the guaranteed analysis with the measured nutrient composition of commercial pet foods.

OBJECTIVE: To compare guaranteed and measured concentrations of nutrients in commercial pet foods. DESIGN: Cross-sectional study. SAMPLE POPULATION: Annual inspection reports of pet food analyses from 5 states. PROCEDURES: Guaranteed and measured concentrations of crude protein (CP), crude fat (CF), crude fiber (CFb), moisture, and ash in pet foods were compared. The concentration difference for each nutrient was compared among types of food, target species, target life stages, manufacturers, and laboratories. RESULTS: The guaranteed and measured concentrations of nutrients were significantly different. For all foods, mean concentration differences were as follows: CP, 1.5%; CF, 1.0%; CFb, -0.7%; moisture, -4.0%; and ash, -0.5%. Crude protein difference for treats was significantly larger than differences for dry and canned foods. Crude fat difference for dry foods was significantly less than differences for canned foods and treats. Crude fiber and moisture differences for canned foods were significantly less than the corresponding differences for dry foods and treats. Only CFb differences differed among target species, life stages, manufacturers, or laboratories. CONCLUSIONS AND CLINICAL RELEVANCE: Addition of 1.5% and 1% to the guaranteed minimums for CP and CF, respectively; subtraction of 0.7%, 4%, and 0.5% from the guaranteed maximums for CFb, moisture, and ash, respectively; and addition of 0.23 kcal/g to the as-fed metabolizable energy value calculated by use of modified Atwater factors from guaranteed analyses provides a more accurate estimate of the nutrient and metabolizable energy content of commercial pet foods. Nevertheless, the actual composition of a food should be determined whenever possible.