In vitro biomechanical comparison of limited contact dynamic compression plate and locking compression plate

The locking compression plate (LCP) supports biological osteosynthesis by functioning as an internal fixator, rather than as a full or limited contact bone plate which must be adequately contoured and affixed directly to the bone for stable internal fixation of the fracture. In order to help justify the use of the LCP in our veterinary patients, in vitro biomechanical testing was performed comparing the LCP to the conventional limited contact dynamic compression plate (LC-DCP) in canine femurs. We hypothesized that the LCP construct would be at least as stiff under bending and torsional loads as the LC-DCP. The LCP and LC-DCP were applied over a 20-mm osteotomy gap to contralateral bones within each pair of 14 femora. Non-destructive four-point bending and torsion, and cyclical testing in torsion were performed. The constructs were then loaded to failure in torsion. In medial-lateral and lateral-medial structural bending, significant differences were not found between the LCP and LC-DCP, however, at the gap, the LCP construct was stiffer than the LC-DCP in lateral-medial bending. Significant differences in behaviour over time were not noted between the plate designs during cyclical testing. When loading the constructs to failure in internal rotation, the LC-DCP failed at a significantly lower twist angle (P = .0024) than the LCP. Based on the similar performance with loading, the locking compression plate is a good alternative implant for unstable diaphyseal femoral fracture repair in dogs.

In vitro biomechanical comparison of limited contat dynamic compression plate and locking compression plate

The locking compression plate (LCP) supports biological osteosynthesis by functioning as an internal fixator, rather than as a full or limited contact bone plate which must be adequately contoured and affixed directly to the bone for stable internal fixation of the fracture. In order to help justify the use of the LCP in our veterinary patients, in vitro biomechanical testing was performed comparing the LCP to the conventional limited contact dynamic compression plate (LC-DCP) in canine femurs. We hypothesized that the LCP construct would be at least as stiff under bending and torsional loads as the LC-DCP. The LCP and LC-DCP were applied over a 20-mm osteotomy gap to contralateroal bones within each pair of 14 femora. Non-destructive four-point bending and torsion, and cyclical testing in torsion were performed. The constructs were then loaded to failure in torsion. In medial-lateral and lateral-medial structural bending, significant differences were not found between the LCP and LC-DCP, however, at the gap, the LCP construct was stiffer than the LC-DCP in lateral-medial bending. Significant differences in behaviour over time were not noted between the plate designs during cyclical testing. When loading the constructs to failure in internal rotation, the LC-DCP failed at a significantly lower twist angle (P = .0024) than the LCP. Based on the similar performance with loading, the locking compression plate is a good alternative implant for unstable diaphyseal femoral fracture repair in dogs.

Assessing the efficacy of perioperative carprofen administration in dogs undergoing surgical repair of a ruptured cranial cruciate ligament

Twenty-one otherwise healthy dogs that presented for surgical repair of a ruptured cranial cruciate ligament were blindly and randomly given either carprofen (2.2 mg/kg body weight, orally) or a placebo beginning 12 hours preoperatively and continuing every 12 hours for a total of three doses. The patients were assessed for postoperative pain using a subjective pain score and given oxymorphone (0.1 mg/kg body weight, intramuscularly) every four hours if the pain score was 2 or greater. Blood samples were also collected to determine serum cortisol levels. There was a significant increase in serum cortisol levels in the immediate postoperative period in both the placebo group and the carprofen group (p less than 0.05). There was no significant difference in the percentage of increase in serum cortisol levels between the two groups. No correlation was evident between the serum cortisol levels and the corresponding pain scores in either group. This subjective method of assessing postoperative pain was not accurate and should not be relied upon for determination of postoperative analgesic administration. Perioperative oral administration of carprofen did not appear to be effective in controlling postoperative pain in these patients.

Biomechanical comparison of two plating techniques for fixation of acetabular osteotomies in dogs

OBJECTIVE

To compare the failure properties of a 5-hole, 2.7-mm curved acetabular plate (AP) to a 5-hole, 3.5-mm reconstruction plate (RP) when applied to acetabular osteotomies.

STUDY DESIGN

Cadaver study.

ANIMALS OR SAMPLE POPULATION

Pelves of 8 mature, large-breed dogs.

METHODS

A 5-hole, 2.7-mm AP and a 5-hole, 3.5-mm RP were contoured and applied to the dorsal acetabulum of each pelvis. A central acetabular fracture was simulated after plate application by a transverse osteotomy with a fine saw. Each acetabulum was loaded in a weight-bearing direction. A load-deformation curve was produced for each construct, and biomechanical properties of the AP and RP were compared with the Student's paired t-test. A P value of < .05 was considered significant.

RESULTS

For the AP and RP composite respectively, the mean +/- SD maximum load to failure was 2,721 +/- 632 N and 2,488 +/- 800 N, the stiffness was 4.8 +/- 1.8 N/m and 5.3 +/- 1.9 N/m, and the energy absorbed was 15.1 +/- 5.2 Nm and 16.3 +/- 8.3 Nm. None of these differences was statistically significant.

CONCLUSIONS

Both fixation techniques provided comparable strength, stiffness, and energy absorbed under the loading conditions of this study.

CLINICAL RELEVANCE

Because of the relative ease of application, the 2.7-mm curved AP may be the practical choice for acetabular fracture repair in large dogs.

Exposure and postoperative stability of three medial surgical approaches to the canine elbow

Articular cartilage exposure and immediate postoperative stability provided by three medial surgical approaches in canine cadaver elbows were compared. The approaches evaluated were a desmotomy of the medial collateral ligament (DMCL) that included a tenotomy of the pronator teres muscle, a longitudinal myotomy of the flexor carpi radialis (MFCR), and an osteotomy of the medial epicondyle (OME). Nondestructive biomechanical testing was performed before the surgical approach and repeated after surgery. The stiffness at 13 degrees valgus deviation of the elbow and energy absorption up to 13 degrees valgus deviation of the elbow were determined from the preoperative and postoperative torque-rotation curves. The perimeters of the ulnar and humeral articular cartilage that were visualized through the approach were scored with a dental pick. Latex casts were made of articular surfaces of the elbow. The humeral and ulnar articular exposures were determined by computerized planimetric analysis of latex cast photocopies. The humeral cartilage exposure of the OME approach was significantly greater than either the MFCR or DMCL approaches. The DMCL approach provided a significantly greater humeral cartilage exposure than the MFCR approach. All three approaches provided statistically similar percentages of ulnar cartilage exposure. The stiffness and energy absorption of the OME and MFCR approaches were similar and significantly greater than the DMCL approach. The OME approach provided the best combination of exposure and immediate postoperative stability.

The effect of long-term bone plate application for fixation of radial fractures in dogs

This study was divided into two phases. In the in vitro phase, a stainless steel bone plate was applied to the cranial surface of the radius in 14 canine limbs. The effect of the presence of a bone plate on bone density analysis using radiographic photodensitometry (RP) was evaluated by comparing the density measurement of the unplated limb to the density measurement of the plated limb. The optical density of the plated bones was 12% greater than that of the unplated bones. This information was used as a correction factor for the in vivo study. In the in vivo phase, 23 dogs with radial and ulnar fractures were examined for complications associated with the long-term application of a stainless steel plate applied to the cranial surface of the radius. In 14 dogs, RP analysis was used to compare the plated limb with the normal, contralateral limb. No significant differences in radial cortical bone density existed between the plated limb and the contralateral limb after taking into account the effect a bone plate had on photodensitometry readings. There was no significant correlation between the change in radial cortical density and the duration of bone plate application, suggesting that a steady state between bone loss and bone production occurs after long-term plate fixation of the fractured canine radius. The majority (87%) of the dogs with a plate applied to the radius greater than 1 year had normal limb usage when standing, walking, or running.

Cervical fibrotic stenosis in a young Rottweiler

An 18-month-old neutered male Rottweiler was examined because of slowly progressive spastic tetraparesis and ataxia. Signalment and clinical signs were suggestive of 2 neuronal degenerative diseases presumed to be inherited in young Rottweilers: leukoencephalomyelopathy and neuroaxonal dystrophy. Myelography revealed an extradural compression at the articulation of the second and third cervical vertebrae. At surgery, focal hypertrophy of the yellow ligament was observed to compress the spinal cord ventrally at that site.

Healing characteristics of free and pedicle fat grafts after dorsal laminectomy and durotomy in dogs

Dorsal laminectomy and durotomy were performed at thoracic vertebrae 12 and 13 (T12-T13) and lumbar vertebrae 1 and 2 (L1-L2) in 12 normal dogs. A free fat graft harvested from subcutaneous tissue adjacent to the incision was placed over the T12-T13 laminectomy site. A 75 X 25 X 5 mm pedicle fat graft harvested from a similar location was placed over the L1-L2 laminectomy site. Three dogs each were euthanatized at weeks 2, 4, 8, and 16. With both types of fat grafts, an initial inflammatory stage reduced the size of the graft approximately 50%. Axonal degeneration and demyelination of the spinal cord resolved by week 16. At week 16, the durotomy sites had healed, but the dura mater was adhered to the spinal cord. No difference between the grafts could be demonstrated by antemortem myelography and cerebrospinal fluid analysis. There was no demonstrable advantage to the use of pedicle fat grafts.

Influence of nonbiologic implants on laminectomy membrane formation in dogs

The effects of various surgical implants, spinal cord hypothermia, and glucocorticoid administration on formation of the laminectomy membrane were evaluated in 32 preconditioned chondrodystrophoid dogs. Modified dorsal laminectomies and full-length durotomies, from T12 to L1, were performed on all dogs. Dogs were allotted to 2 groups. Group-1 dogs (n = 20) were further allocated to 4 subgroups (a, b, c, and d) consisting of 5 dogs each. Group-1a dogs received no implant, group-1b dogs had absorbable gelatin sponges implanted, group-1c dogs had absorbable gelatin films implanted, and group-1d dogs had absorbable gelatin sponges and absorbable gelatin films implanted. Daily neurologic examinations permitted correlation of neurologic dysfunction with secondary spinal cord compression in those dogs in which it developed. The influence of these implants on laminectomy membrane formation and dural healing was assessed by gross and microscopic evaluation of transverse sections of the vertebrae and spinal cord after euthanasia of one member of each subgroup at 1, 2, 4, 8, and 16 weeks after surgery. Group-2 dogs (n = 12) were further allotted to 3 subgroups (a, b, and c) consisting of 4 dogs each. One dog in each group-2 subgroup underwent the same surgical procedures described for the group-1 subgroups (ie, 4 procedures/group-2 subgroup). The additional effects of 3 conventional supportive techniques (selective regional spinal cord hypothermia, glucocorticoid administration, or spinal cord hypothermia and glucocorticoid administration) on laminectomy membrane formation and on immediate postoperative recovery were examined in groups 2a, 2b, and 2c, respectively. Neurologic examinations were performed daily until this time. All dogs in group 2 were euthanatized 1 week after surgery for gross and microscopic examination of transverse sections of the vertebrae and spinal cord. Qualitative histopathologic effects of the different implants and supportive techniques on formation of the laminectomy membrane were determined. Statistical analysis of the degrees of secondary spinal cord compression was performed in group-1 dogs by measuring and comparing ratios of the vertical to the horizontal diameters of the transverse spinal cord sections from locations within (T12 to L1) and out of (T11, T11-12, L1-2, and L2) the region of surgical intervention. The vertical/horizontal diameter ratios measured from transverse sections from T11 to L2 in size-matched, untreated control dogs formed the standards for a mean roundness index of the spinal cord in the various anatomic locations of the vertebral column.(ABSTRACT TRUNCATED AT 400 WORDS)

Modified deep dorsal laminectomy in the dog

Spinal cord compression subsequent to radical laminectomy was investigated. A modified deep dorsal laminectomy technique was devised to allow extensive exposure and decompression of the canine spinal cord without undue hazard of postoperative fibrotic spinal cord compression. A previously described laminectomy technique was modified by the addition of spinal plating to avoid the occurrence of constrictive fibrosis.