Ability of the Tightrope® and percutaneous lateral fabellar suture techniques to control cranial tibial translation.

OBJECTIVE: To compare the ability of the Tightrope® (TR) cranial cruciate ligament (CCL) technique, percutaneous lateral fabella suture (pLFS) technique, and normal CCL to control cranial tibial translation (CTT). STUDY DESIGN: In vitro biomechanical study. SAMPLE POPULATION: Cadaveric canine pelvic limbs (n = 18 pairs). METHODS: Six small animal surgical residents (1 pair each) and a Diplomate of the American College of Veterinary Surgeons (10 pairs) performed TR and pLFS techniques on paired limbs. Two intact limb pairs served as controls. Limbs were assessed by palpation, radiographs, and dissection before mechanical testing of resistance to CTT. Forces resisted during displacement were compared between groups with a mixed ANOVA and post hoc tests. RESULTS: With 5 mm of displacement, the pLFS resisted 72 ± 45 N and the TR resisted 66 ± 48 N of load. The intact CCL resisted 400 ± 35 N. The intact CCL resisted displacement significantly more than either surgical technique. CONCLUSIONS: TR and pLFS had similar ability to resist CTT but neither restored the biomechanical properties of an intact CCL.

Evaluation of composite resin materials for maxillomandibular fixation in cats for treatment of jaw fractures and temporomandibular joint luxations.

OBJECTIVE: To identify a method of composite application for maxillomandibular fixation (MMF) in cats that ensures the material will remain bonded during convalescence but be easy to remove with a low complication rate. STUDY DESIGN: Experimental study. SAMPLE POPULATION: Feline cadavers (n=88). METHODS: MMF was applied using composite to 4 groups of 22 feline cadaver heads each. The protocols were: group CR: acid etch and composite resin; group CR+: acid etch, bonding agent, and composite resin; group FR50: partial surface acid etch and flowable composite resin; group FR100: complete surface acid etch and flowable composite resin. Removal time and complication rate were noted. Load to failure was determined by tensile loading. RESULTS: Load to failure was similar for groups CR and CR+ and for groups FR50 and FR100; however, load to failure for groups FR50 and FR100 was higher than groups CR and CR+ (P<.01). Time for material removal for group FR100 was longer (P<.01) and the complication rate was higher (P<.01) compared with the groups CR, CR+, and FR50, with no significant differences in removal times and complication rate between the latter groups. The most frequent complication during material removal in group FR100 was crown fracture. CONCLUSIONS: Partial coronal surface acid etch before use of flowable composite maintained a strong bond, yet resulted in easy material removal with a low complication rate.

Biomechanics of aggressive inline skating: landing and balancing on a grind rail.

Currently, only epidemiological injury data have been reported for the new extreme sport of aggressive inline skating, or trick skating. No studies have examined the biomechanics of this sport, which involves repetitive jumping and landing from railings, ramps, and ledges, often over 1 m in height. We present results of a pilot study that examined the effect of skater experience and lower extremity biomechanics on energy absorption ability, and observed balance strategies used during two basic tricks. In these tricks, the skater jumps onto an elevated rail and maintains balance while standing in a single position (stall) or sliding along the rail (grind). Lower extremity joint kinematics, impact force characteristics, and general movement behaviours were examined during landing and balance phases. Ten male skaters performed ten stalls and ten frontside grinds on an instrumented grind rail, capable of measuring vertical force. Vertical impact force was found to decrease with increasing skater experience in stalls (r = -0.84, P = 0.002) and grinds (r = -0.84, P = 0.009). This might imply that less-experienced skaters are (subconsciously) more concerned about maintaining balance than refining technique to minimize impact force. Similar to drop landing experiments, peak impact force decreased with increasing knee flexion during stalls (r = -0.65, P = 0.04). During stalls, skaters demonstrated classic balance maintenance strategies (ankle, hip, or multi-joint) depending on trick length. During grinds, skater centre of mass never passed over the rail base of support, suggesting the use of momentum produced from obliquely approaching the rail.

Evaluation of an osteoconductive resorbable calcium phosphate cement and polymethylmethacrylate for augmentation of orthopedic screws in the pelvis of canine cadavers.

OBJECTIVE: To evaluate the effect of an osteoconductive resorbable calcium phosphate cement (CPC) on the holding power of bone screws in canine pelvises and to compare the effect with that for polymethylmethacrylate (PMMA). SAMPLE POPULATION: 35 pelvises obtained from canine cadavers. PROCEDURE: Each pelvis was sectioned longitudinally. Within each pair of hemipelvises, one 4.0-mm cancellous screw was placed in the sacroiliac (SI) region and another in the iliac body. Similar regions on the contralateral-matched hemipelvis were assigned 1 of 3 augmentation techniques (CPC-augmented 4.0-mm cancellous screws, PMMA-augmented 4.0-mm cancellous screws, and CPC-augmented 3.5-mm cortical screws). Pullout force was compared between matched screws and between treatment groups prior to examination of cross sections for evaluation of cement filling and noncortical bone-to-cortical bone ratio. RESULTS: CPC and PMMA augmentation significantly increased pullout force of 4.0-mm screws inserted in the SI region by 19.5% and 33.2%, respectively, and CPC augmentation significantly increased pullout force of 4.0-mm cancellous screws inserted in the iliac body by 21.2%. There was no difference in the mean percentage augmentation between treatment groups at either location. Cement filling was superior in noncortical bone, compared with filling for cortical bone. Noncortical bone-to-cortical bone ratio was significantly greater in the sacrum (6.1:1) than the ilium (1.3:1). CONCLUSIONS AND CLINICAL RELEVANCE: CPC and PMMA improve the ex vivo holding strength of 4.0-mm cancellous screws in the SI and iliac body regions and SI region, respectively. Cement augmentation may be more effective in areas with greater noncortical bone-to-cortical bone ratios.

Evaluation of 2 cement techniques for augmentation of stripped 1.5 mm screw sites in the distal metaphysis of feline radii.

OBJECTIVE: To evaluate the effect of 2 cement augmentation techniques on pullout strength of 1.5 mm screws placed in stripped 1.5 mm screw sites in the distal metaphysis of feline radii. STUDY DESIGN: Experimental study. SAMPLE POPULATION: Feline radii (21 pairs). METHODS: Treatment groups (n=4) were allocated according to a Latin square design to 4 sites in each pair of radii. Positive and negative controls were a 1.5 mm screw and a screw of the same diameter in a previously stripped screw hole, respectively. Treatment groups were a 1.5 mm screw implanted in a previously stripped screw hole after injection of polymethylmethacrylate (PMMA) or a bioresorbable calcium phosphate cement (CPC, Norian skeletal repair system (SRS)). The ultimate pullout strength was compared between groups. RESULTS: The mean (+/-SEM) pullout strength of screws augmented with either bone cement was less than that of the positive control group and greater than that of the negative control. Injection of CPC or PMMA before screw implantation increased the pullout strength of the negative control by 86.8+/-22.9% and 104.1+/-32.1%, respectively. Holding power of the positive control screws differed from these 2 groups, and was 274.8+/-39.17% higher than that of the negative control. CONCLUSION: Injection of CPC or PMMA increases but does not restore the holding power of stripped 1.5 mm diameter screws. CLINICAL RELEVANCE: The use of CPC (Norian SRS) augmentation of stripped 1.5 mm diameter screws warrants clinical investigation as it combines biomechanical results similar to PMMA with osteoconduction and resorbability.