Ex Vivo Biomechanical Comparison of Titanium Locking Plate, Stainless Steel Nonlocking Plate, and Tie-in External Fixator Applied by a Dorsal Approach on Ostectomized Humeri of Pigeons (Columba livia)

To compare the bending strength of a locking plate (LP), nonlocking plate (NLP), and an external skeletal fixator intramedullary pin (ESF-IM) tie-in fixation applied by a dorsal approach in an avian humerus fracture model, 5 left humeri obtained from pigeon (Columba livia) cadavers were randomly assigned to each repair technique (n = 15). The ESF-IM group was repaired with a 0.062-inch intramedullary pin tied-in with two 0.035-inch positive profile transfixation pins using acrylic filled plastic tubing. The LP group was repaired with a dorsally applied titanium 1.6-mm screw 7-hole locking plate (1 bicortical and 2 monocortical screws in each segment). The NLP group was repaired with a dorsally applied 6-hole stainless steel 1.5-mm dynamic compression plate (all bicortical screws). All constructs were applied before complete ostectomy to allow perfect reconstruction. Constructs were cyclically tested nondestructively for 1000 cycles in four-point bending before being tested to failure. Outcome measures included stiffness, strength, and strain energy. All specimens cycled without failure. The ESF-IM specimens were significantly stiffer and stronger than the plated repair groups. Plated constructs had significantly higher strain energies than ESF-IM. LP and NLP were of equal stiffness, strength, and strain energies. This study demonstrated that bending biomechanical properties of the ESF-IM configuration were superior to those of the dorsal plate fixation. Exact properties of fixation required to facilitate avian fracture healing are largely unknown. Further study, including assessments of optimal plate position and configuration, and torsional and in vivo studies in avian species are warranted.

Variables Affecting Thigh Girth Measurement and Observer Reliability in Dogs

Objective: The purpose of the study reported here was to describe variables affecting thigh girth measurements preoperatively and 2 weeks after surgical stabilization of the stifle and to examine inter- and intra-observer reliability.

Animals: Ten hound-type dogs with experimental, unilateral, cranial cruciate ligament transection, and surgical stabilization.

Procedures: Dogs were placed in lateral recumbency for measurements of thigh circumference after the stifle was placed in flexed (F), estimated standing (S), and extended (E) positions. Measurements were made at 50 and 70% of thigh length (TL), with hair unclipped and then clipped prior to surgery, before and 2 weeks after cruciate ligament transection and stifle stabilization, and with and without sedation. A spring tension measuring tape was used to determine thigh girth that allowed a consistent amount of end-tension to be applied to the tape. All measurements were made by two blinded individuals in triplicate, data were recorded for each set of measurements and the mean of the three measurements for each condition was used for analysis.

Results: Thigh girth was significantly greater at the more proximal site of 50% TL (36.7 ± 2.6 cm) when compared to the 70% TL (31.7 ± 2.7 cm) (P = 0.001). Sedation did not significantly affect thigh girth at any stifle position at the 70% and 50% TL. Although there were no differences in thigh circumference between the flexion and standing positions at 50% TL (F 38.2 ± 2.8 cm, S 38.1 ± 2.9 cm) and 70% TL (F 33.6 ± 1.6 cm; S 33.6 ± 1.8 cm), full extension of the stifle resulted in significantly less thigh girth (50% TL 36.6 ± 2.6 cm, P = 0.006; 70% TL 31.7 ± 2.6 cm, P = 0.006). Significant decreases in thigh girth were seen after surgery in all limb positions at both measurement sites. The highest correlations between Observer 1 (OB1) and Observer 2 (OB2) with least differences in measurements were with the stifle in the extended position. Agreement between two observers using standard measuring technique was significant at both the 50% (OB1: 34.10 ± 2.93 cm, OB2: 34.08 ± 2.65 cm, P = 0.007, ICC = 0.984) and 70% (OB1: 29.89 ± 2.43 cm, OB2: 30.04 ± 2.30 cm, P = 0.004, ICC = 0.981) TL positions with the stifle placed in extended position.

Conclusion and Clinical Importance: Thigh girth measurement may be useful as an outcome measure when appropriate measuring technique is used. It is recommended that thigh girth be obtained at a distance of 70% thigh length, with the leg in an extended position while in lateral recumbency, and the dog relaxed or under sedation. Further studies should be performed in a variety of clinical situations.

Contribution of antirotational pins and an intact fibula to the ex vivo compressive strength of four tibial plateau leveling osteotomy constructs

OBJECTIVE To assess the contribution of antirotational pins (ARPs) and an intact fibula to the compressive strength of 4 tibial plateau leveling osteotomy (TPLO) constructs (bone and implants). SAMPLE 20 hind limbs from 10 canine cadavers. PROCEDURES Each hind limb was assigned to 1 of 4 TPLO constructs (construct in which the ARP was removed, constructs in which 1 or 2 ARPs were left in place, and construct in which the ARP was removed and the fibula was cut). Following TPLO completion, all limbs underwent mechanical testing that included 10,000 cycles of cyclic axial compression followed by testing to failure at a displacement rate of 1 mm/s. Displacement during cyclic testing; load generated at 0.5, 1.0, and 3.0 mm of displacement; ultimate load; and failure type were recorded for each limb. Mean values were compared among the groups. RESULTS None of the specimens failed during cyclic testing. None of the variables assessed during mechanical testing differed significantly among the 4 groups. During testing to failure, the majority (17/20) of specimens failed as the result of a long oblique fracture through the first screw hole in the distal segment. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the axial compressive strength and stiffness of a TPLO construct were not significantly affected by the addition of 1 or 2 ARPs or the presence of an intact fibula. These findings appear to support removal of ARPs during uncomplicated TPLOs, but further research is warranted to assess the effect of ARP removal on bone healing and complication rates.

Use of an inverse dynamics method to compare the three-dimensional motion of the pelvic limb among clinically normal dogs and dogs with cranial cruciate ligament-deficient stifle joints following tibial plateau leveling osteotomy or lateral fabellar-tibial suture stabilization

OBJECTIVE

To compare the 3-D motion of the pelvic limb among clinically normal dogs and dogs with cranial cruciate ligament (CCL)-deficient stifle joints following tibial plateau leveling osteotomy (TPLO) or lateral fabellar-tibial suture (LFS) stabilization by use of an inverse dynamics method.

ANIMALS

6 clinically normal dogs and 19 dogs with CCL-deficient stifle joints that had undergone TPLO (n = 13) or LFS (6) stabilization at a mean of 4 and 8 years, respectively, prior to evaluation.

PROCEDURES

For all dogs, an inverse dynamics method was used to describe the motion of the pelvic limbs in the sagittal, frontal, and transverse planes. Motion and energy patterns for the hip, stifle, and tibiotarsal (hock) joints in all 3 planes were compared among the 3 groups.

RESULTS

Compared with corresponding variables for clinically normal dogs, the hip joint was more extended at the beginning of the stance phase in the sagittal plane for dogs that had a TPLO performed and the maximum power across the stifle joint in the frontal plane was greater for dogs that had an LFS procedure performed. Otherwise, variables in all planes were similar among the 3 groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Gait characteristics of the pelvic limb did not differ between dogs that underwent TPLO and dogs that underwent an LFS procedure for CCL repair and were similar to those of clinically normal dogs. Both TPLO and LFS successfully provided long-term stabilization of CCL-deficient stifle joints of dogs with minimal alterations in gait.

Biomechanics of Rehabilitation

The biomechanics of motion and rehabilitation are complex, with many tissue types and structures involved. In addition, consideration must be given to the stage of tissue healing with some injuries, such as fractures.A more thorough knowledge of some of the infrequently discussed biomechanical aspects of musculoskeletal tissues and motion during rehabilitation, combined with known features of tissue recovery, should enhance the development of rehabilitation programs for patients.

Results of arthroscopic versus open arthrotomy for surgical management of cranial cruciate ligament deficiency in dogs

OBJECTIVE

To evaluate postoperative morbidity in dogs after experimental cranial cruciate ligament transection and immediate stifle stabilization using an arthroscopically assisted or open arthrotomy technique.

STUDY DESIGN

Experimental, prospective study.

ANIMALS

Thirteen mature, healthy dogs.

METHODS

Dogs were randomly assigned to 1 of 2 groups. Seven underwent open arthrotomy while 6 underwent arthroscopy of 1 stifle joint. Cranial cruciate ligaments were transected and debrided and all stifles were stabilized using 2 lateral extracapsular fabellar-tibial sutures. Minimally invasive suture placement was employed in the arthroscopy group. All animals were evaluated for 9 weeks using kinetic gait assessments, comfortable stifle range of motion measurements, thigh girth measurements, differential cell counts of synovial fluid, and subjective scores of behavior, limb use, and lameness.

RESULTS

Significant differences in postoperative morbidity were observed during the 9-week postoperative period. Greater peak vertical force for 8 weeks (P=.015), vertical impulse for 6 weeks (P=.044), comfortable stifle range of motion for 9 weeks (P=.017), comfortable stifle flexion for 4 weeks (P=.005), and operative limb thigh circumference (P=.020) for 9 weeks were observed for the arthroscopy group. A trend towards a lower differential mean synovial polymorphonuclear cell count in the arthroscopy group was seen at 4 and 8 weeks postoperatively. No differences in subjective evaluation scores were noted.

CONCLUSIONS

In this study population, significant differences were seen between the arthroscopy and arthrotomy groups for peak vertical force, vertical impulse, comfortable stifle range of motion, comfortable stifle flexion, and thigh circumference data.

CLINICAL RELEVANCE

The results of this study suggest that short-term postoperative morbidity may be reduced in dogs receiving arthroscopic joint surgery with a limited approach for stifle stabilization as compared with a traditional open arthrotomy technique.

Effect of deracoxib, a new COX-2 inhibitor, on the prevention of lameness induced by chemical synovitis in dogs

Twenty-four healthy, mixed-breed hound-type dogs were evenly and randomly assigned to a placebo control group, one of four dosages of deracoxib (0.3, 1, 3, or 10 mg/kg), or carprofen (2.2 mg/kg). Oral dosing of placebo, carprofen, or deracoxib was done 30 minutes before intraarticular injection of urate crystal suspension for induction of synovitis. Ground reaction forces, subjective clinical lameness scores, pain, joint effusion, and quantitative pain threshold responses were measured in a blinded fashion before induction of synovitis and 2, 4, 6, 8, 12, and 24 hours after injection. The medium and high dosages of deracoxib were effective in preventing lameness and pain associated with synovitis. Carprofen was also somewhat effective in attenuating the severity of urate-induced synovitis but to a lesser degree than the medium dose of deracoxib. Preemptive deracoxib treatment at dosages as low as 1 mg/kg reduced lameness and pain of synovitis associated with intraarticular administration of urate crystals.

Radiographic, densitometric, and biomechanical effects of recombinant canine somatotropin in an unstable ostectomy gap model of bone healing in dogs

OBJECTIVE

To determine the effect of recombinant canine somatotropin (STH) on radiographic, densitometric, and biomechanical aspects of bone healing using an unstable ostectomy gap model.

STUDY DESIGN

After an ostectomy of the midshaft radius, bone healing was evaluated over an 8-week period in control dogs (n = 4) and dogs receiving recombinant canine STH (n = 4).

ANIMALS OR SAMPLE POPULATION

Eight sexually intact female Beagle dogs, 4 to 5 years old.

METHODS

Bone healing was evaluated by qualitative and quantitative evaluation of serial radiographs every 2 weeks. Terminal dual-energy x-ray absorptiometry and three-point bending biomechanical testing were also performed.

RESULTS

Dogs receiving STH had more advanced radiographic healing of ostectomy sites. Bone area, bone mineral content, and bone density were two to five times greater at the ostectomy sites of treated dogs. Ultimate load at failure and stiffness were three and five times greater in dogs receiving STH.

CONCLUSIONS

Using the ostectomy gap model, recombinant canine STH enhanced the radiographic, densitometric, and biomechanical aspects of bone healing in dogs.

CLINICAL RELEVANCE

Dogs at risk for delayed healing of fractures may benefit from treatment with recombinant canine STH.

The effects of plate type, angle of ilial osteotomy, and degree of axial rotation on the structural anatomy of the pelvis

Unilateral triple pelvic osteotomy was performed with three variations in technique on canine cadaver pelves. The following variables were studied: the angle of the ilial osteotomy (perpendicular to the long axis of the ilium and 10 degrees, 20 degrees, and 30 degrees off perpendicular); the degree of axial rotation (20 degrees, 30 degrees, and 45 degrees); and the type of fixation (canine pelvic osteotomy plate [CPOP] or a 2.7-mm dynamic compression plate [DCP]). Structural changes measured were the pelvic inlet and acetabular area, interischiatic tuberosity distance, and degree of acetabular version. Means and standard error of the means were determined for all pelvic measurements and were analyzed by three-way analysis of variance (P < .05). As the axial rotation increased from 20 degrees to 45 degrees an ilial osteotomy angled 10 degrees, 20 degrees, or 30 degrees resulted in a significantly greater decrease in the pelvic inlet area and significantly less deviation of the interischiatic tuberosity distance and degree of acetabular version from normal than an osteotomy directed perpendicular to the long axis of the ilium. Compared with the CPOP, as the axial rotation increased from 20 degrees to 45 degrees, the DCP resulted in a significantly greater decrease in the pelvic inlet area, an increase in the interischiatic tuberosity distance and degree of acetabular version, and less of an increase in the acetabular area. The results of this study suggest that to maximize dorsal acetabular coverage, while minimizing disruption of normal pelvic architecture, a CPOP and an ilial osteotomy angled 10 degrees to 30 degrees are preferred for all degrees of axial rotation.

Biomechanics of the normal and abnormal hip joint

Static analysis of the canine hip has given some insight to the nature and trend of the force and subsequent stress that is normally applied to the joint. Using the static model, the magnitude and direction of force and stress worsens in the hip with the anatomic and stability changes associated with CHD. More sophisticated dynamic models that take into account unbalanced forces and moments with the resultant motion are needed to better understand the mechanics of the hip joint.

Thoracic, abdominal, and vertebral actinomycosis. Diagnosis and long-term therapy in three dogs

The clinical, laboratory, radiographic, and histologic features and the response to therapy in three dogs with actinomycosis are reported. One dog (dog 1) had a 12-cm nonresectable mass extending from the ventrolateral chest wall into the left ventricular myocardium. Another dog (dog 2) had a diffuse peritonitis with "sulfur granules" and two large masses. One of these masses was nonresectable involving adjacent abdominal structures. A third dog (dog 3) had a subvertebral mass at T1-3 producing quadraplegia. Two dogs had periosteal reactions involving adjacent sternebrae (dog 1) or ribs and vertebral bodies (dog 3) that are characteristic of Actinomyces spp infections. In dogs 1 and 2 the diagnosis was based on the morphologic and tinctorial properties of free sulfur granules and/or tissue granules. Culture results were variable. Tissue from dog 1 yielded no growth, while polymicrobial infections, which included Actinomyces spp, were identified in dogs 2 and 3. Actinomyces odontolyticus was isolated from dog 3. Although the actinomycotic granulomas were either not excised or only partially excised from dogs 1 and 2, both animals were cured by the oral administration of high doses of penicillin G for 19 and 6 months, respectively. Dog 3 responded dramatically to the same antibiotic therapy given for 5 months. However, within 4 months of discontinuing treatment an abscess and draining fistulous tracts developed in the left axillary region. Two surgical fistulectomies and additional penicillin therapy were required to cure this animal. These cases and the current veterinary and human literature on actinomycosis are used to propose a rational approach to the treatment of actinomycosis in the dog.

Growth deformities

This article discusses principles of corrective osteotomy and describes operative plans for specific growth deformities such as premature closure of the distal ulna, asynchronous growth of the radius and ulna in achondroplastic breeds, retarded growth of the distal radius, retarded growth of the proximal radius, and synostosis of the radius and ulna.

Effects of exposure to ambient air on articular cartilage of rabbits

Effects of exposure to ambient air (20 to 22 C) on articular cartilage from rabbits were evaluated. Bilateral arthrotomies were performed on the stifles of 18 New Zealand White rabbits. The cranial surface of the left distal femur, including the articular cartilage of the trochlea, was exposed to air for 2 hours. The right stifle was opened and closed immediately. Six rabbits were killed at the end of the surgical operation (group 1), 6 after 2 weeks (group 2), and 6 after 4 weeks (group 3), and femurs were harvested. A distinct color change was seen in the exposed cartilage in group 1; however, minimal change was detected in group 2, and no change was seen in group 3. Proteoglycan content did not differ between the exposed and control cartilage in any group. The number of viable cells and empty lacunae in articular cartilage did not differ between the exposed and control femurs. Total cell counts and degenerative cell counts were similar, comparing the left and right trochlea in groups 1 and 3. A significant increase in cellularity was noticed in the radial zone of the exposed cartilage in group 2 (P less than 0.01). In the same group, a significantly increased number of degenerative cells were seen in the tangential zone of the exposed cartilage (P less than 0.05). Changes in cellularity were consistent with cartilage damage. Seemingly, exposing articular cartilage to air for 2 hours causes reversible cartilage damage.

Effects of tenotomy of the tensor tympani muscle on the acoustic reflex in dogs

The acoustic reflex (AR) was recorded from 12 healthy mixed-breed dogs. Latency and amplitude were measured from ipsilateral and contralateral AR at stimulus frequencies of 1 and 2 kHz and intensities of 70 to 110 dB sound pressure level for ipsilateral AR and 70 to 120 dB hearing level for contralateral AR. Mean latencies for ipsilateral and contralateral AR were between 33.46 and 206.10 ms and between 45.26 and 180.89 ms, respectively, and amplitudes were between 0.14 and 1.79 cm3 and between 0.31 and 1.86 cm3 of air, respectively. Stimulus frequencies and intensities had significant effects (P less than 0.05) on ipsilateral and contralateral AR latencies and amplitudes. Ipsilateral and contralateral AR decays were determined by measuring compliance change during a 10-s pure-tone stimulation at frequencies of 1 and 2 kHz at an intensity of 10 dB above AR threshold. Reflex decays for 1 kHz and 2 kHz frequencies averaged 5.74% and 9.71%, respectively, for ipsilateral AR and 5.08% and 5.40%, respectively, for contralateral AR. Bilateral tympanograms and brain stem auditory-evoked responses were performed on each dog. Mean normal static compliance of the middle ear, as determined by tympanometry, was 0.15 cm3. Unilateral tenotomy of the tensor tympani muscle was done on 6 of the 12 dogs, and each of the preceding procedures were repeated within 1 week after surgical operation. Transection of the tensor tympani tendon did not alter (P greater than 0.05) the latencies or amplitudes of 1 kHz- or 2 kHz-evoked contralateral AR, the latency or amplitude of 1 kHz-evoked ipsilateral AR, or the amplitude of 2 kHz-evoked ipsilateral AR. However, the latency of 2 kHz-evoked ipsilateral AR was significantly (P less than 0.05) increased. Reflex decay increased significantly (P less than or equal to 0.001) for the contralateral reflex elicited by the 2 kHz stimulus. Neither compliance of the middle ear system nor amplitude and latency of the brain stem auditory-evoked response were affected (P greater than 0.05) by tenotomy. Since tenotomy eliminates participation of the tensor tympani in the AR, these data indicate that contraction of this muscle is not primarily responsible for the compliance changes recorded during an acoustic reflex in dogs.

Preliminary study on the use of ultrasonic transmission imaging to evaluate the hip joint in the immature dog

Real-time ultrasonic transmission imaging presents an orthographic image of anatomy similar to that obtained with X-ray fluoroscopy. Transmission imaging allows visualization of the dynamic interaction of muscle, cartilage, bone, tendon and joints during selective palpation and movement. The hip joints of deceased dogs, 7-8 weeks of age, were sonographically evaluated at various levels of dissection and correlated with anatomic features. Wherever possible correlation was made qualitatively with radiographs of the pelvis and coxofemoral joints. Although some features of the hip could be imaged, ultrasonic transmission imaging will require additional research and development before it is proven to be a useful diagnostic adjunct in clinical veterinary medicine.