The effects of acetabular cup temperature and duration of cement pressurization on cement porosity in a canine total hip replacement model.

OBJECTIVE: To determine the effect of acetabular cup temperature and duration of cement pressurization on porosity of the acetabular cement mantel. STUDY DESIGN: In vitro study. METHODS: Twenty-four polyurethane foam blocks prepared for acetabular prosthetic implantation were implanted with polyethylene acetabular cups using four combinations and variations of temperature and pressure: (1) high temperature/short-term pressurization; (2) high temperature/long-term pressurization; (3) low temperature/long-term pressurization; and (4) low temperature short-term pressurization. Five 1-mm-thick slices were taken from the center of each block using a tissue processing system. The slices were scanned into a personal computer using a photo slide scanner. Imaging software was used to determine cement surface area and size, number, and distribution of pores. The quality of the cement-implant interface was subjectively evaluated. Statistical analysis of relative cement porosity was performed by a Kruskal-Wallis analysis of variance comparing the four groups individually and combining the short-term pressurization groups versus the long-term pressurization groups. RESULTS: There were no significant differences in cement porosity between the four test groups (P =.11). There were no significant differences in porosity between the combined groups (P =.48). CONCLUSIONS: There is no benefit in prewarming acetabular cups before implantation. There are no deleterious effects of short-term pressurization of the cement during implantation.

In vitro experimental study of the effect of radial shortening and ulnar ostectomy on contact patterns in the elbow joint of dogs.

OBJECTIVE: To determine effects of incremental radial shortening and subsequent ulnar ostectomies on joint surface contact patterns in a canine elbow joint model. SAMPLE POPULATION: Paired forelimbs from 9 adult dogs. PROCEDURE: Joint casting was performed by placement of colored polymethylmethacrylate in the elbow joint cavity and loading in a materials testing system at physiologic angle and load. Joint casting was performed in unaltered specimens, after radial shortening, and after subsequent distal ulnar ostectomy, proximal ulnar ostectomy, and proximal ulnar ostectomy with intramedullary pinning. Computer-aided analysis of photographs of proximal radial and ulnar articular surfaces without joint casts was performed before and after each casting procedure. RESULTS: All increments of radial shortening changed the size and location of radial and ulnar contact areas. The radial contact area became smaller, the anconeal contact area disappeared, the medial coronoid contact area migrated craniolaterally, and the lateral projection of the coronoid process became a contact area. A proximal ulnar ostectomy stabilized with an intramedullary pin restored normal contact area size and location and restored continuity of the radial and coronoid contact areas across the radioulnar articulation in 6 of 10 specimens. A midshaft ulnar ostectomy, distal to the level of the radioulnar ligament, had no effect on contact patterns. A proximal ulnar ostectomy without stabilization resulted in varus deformity during loading. CONCLUSIONS AND CLINICAL RELEVANCE: Proximal radial shortening, which creates articular step incongruity, changes the location and size of the radioulnar contact areas. Dynamically stabilized ulnar ostectomies proximal to the radioulnar ligament restore contact patterns in vitro.

Biomechanical analysis of suture anchors and suture materials used for toggle pin stabilization of hip joint luxation in dogs.

OBJECTIVE: To compare in vitro mechanical properties of toggle pins and toggle rods used as suture anchors and of 3 suture materials (50-lb monofilament polybutester, No. 5 braided polyester, and 5-mm woven polyester) commonly used as prosthetic ligaments in the repair of hip joint luxation in dogs. SAMPLE POPULATION: Femoropelvic specimens from the cadavers of 18 dogs. PROCEDURE: Suture anchors were compared by use of pullout tests. Suture materials were compared by use of monotonic and cyclic tensile tests; cyclic tensile tests were performed with the suture placed over the edge of an aluminum bar to simulate the edge of the femoral bone tunnel. In vitro mechanical properties of the ligament of the femoral head were determined by use of monotonic tensile tests, using bone-ligament-bone cadaveric specimens. The in vitro mechanical properties of the acetabulum-ligament-femur complex and of this complex following rupture of the ligament and stabilization with a toggle rod and 5-mm woven polyester were determined by use of compression tests that simulated weight-bearing. RESULTS: Mechanical properties of the toggle rod were not significantly different from those of the toggle pin. Woven polyester had the longest fatigue life in cyclic testing. Hip joints stabilized with a toggle rod and woven polyester had less than half the strength in vitro of intact joints. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that a toggle rod or toggle pin can be used for stabilization of hip joint luxations in dogs. Of the materials tested, braided polyester had the best in vitro mechanical properties.

Forelimb lameness in the adult patient.

Lameness of the forelimb may be one of the more frustrating problems in small animal orthopedics. It is likely that numerous causes of forelimb lameness are not yet defined or well understood. The common and some less common causes of forelimb lameness are discussed as well as their means of diagnosis. The application of new diagnostic tools including arthroscopy and ultrasound are also discussed.

In vitro determination of contact areas in the normal elbow joint of dogs.

OBJECTIVE: To evaluate areas of articular contact of the proximal portions of the radius and ulna in normal elbow joints of dogs and the effects of axial load on size and location of these areas. SAMPLE POPULATION: Forelimbs obtained from cadavers of 5 adult mixed-breed dogs. PROCEDURE: After forelimbs were removed, liquid-phase polymethyl methacrylate was applied to articular surfaces of the elbow joint, and limbs were axially loaded. Articular regions void of casting material were stained with water-soluble paint. Relative articular contact areas were determined by computer-assisted image analyses of stained specimens. Repeatability of the technique was evaluated by analyses of casts from bilateral forelimbs of 1 cadaver. Incremental axial loads were applied to left forelimbs from 4 cadavers to determine effects of load on articular contact. RESULTS: Specific areas of articular contact were identified on the radius, the craniolateral aspect of the anconeus, and the medial coronoid process. The medial coronoid and radial contact areas were continuous across the radioulnar articulation. There was no articular contact of the medial aspect of the anconeus with the central trochlear notch. Coefficients of variation of contact areas between repeated tests and between contralateral limbs was < 20%. Significant overall effects of axial load on contact area or location were not identified. CONCLUSIONS: Three distinct contact areas were evident in the elbow joint of dogs. Two ulnar contact areas were detected, suggesting there may be physiologic incongruity of the humeroulnar joint. There was no evidence of surface incongruity between the medial edge of the radial head and the lateral edge of the medial coronoid process.

Comparison of the fit and geometry of reconstruction of femoral components of four cemented canine total hip replacement implants.

OBJECTIVE: To compare fit and geometry of reconstruction of femoral components of 4 canine cemented total hip replacement implants and determine which implants are most compatible with current principles of cemented arthroplasty. SAMPLE POPULATION: Paired femurs from 16 adult mixed-breed dogs. PROCEDURE: Femurs were prepared for femoral stem implantation of either the Bardet, BioMedtrix, Mathys, or Richards II implant. Mediolateral and craniocaudal radiographs were obtained with femoral components in situ. Cross-sectional analysis of implant fit was performed on transected cemented specimens. Computer-aided analyses of digitized images were performed. RESULTS: The Bardet and Richards II implants reconstructed the original femoral head position significantly better than the other 2 implants. None of the implants allowed neutralization of the implant axis in the sagittal plane or were routinely centralized in the femoral canal. The Bardet implant had the smallest minimum distal tip offset in the sagittal plane. Greatest tip to cortex distance was provided by the Richards II implant in the transverse plane and the Mathys implant in the sagittal plane. The thinnest cement mantle regions for all implants were in the central longitudinal third of the femoral stem. CONCLUSIONS AND CLINICAL RELEVANCE: The Bardet and BioMedtrix implants had stem design characteristics that were most compatible with principles of cemented stem fixation. None of the implants completely satisfied the theoretically optimal conditions of centralization and neutralization of the femoral stem. Innovative design modifications, therefore, may be needed if these conditions are important to the long-term success of canine total hip replacement.

Canine elbow dysplasia. The early radiographic detection of fragmentation of the coronoid process.

Ununited anconeal process, osteochondrosis, and fragmentation of the coronoid process (FCP), separately or together, comprise canine elbow dysplasia. Radiographic detection of ununited anconeal process or osteochondrosis is common, whereas identification of an FCP is often inferred by finding joint incongruity and secondary changes. Early identification of FCP can be improved by evaluating the elbow joint for subtle changes visible early in the course of this disease. Proper radiographic technique and positioning are essential in optimizing identification of the changes associated with mild or early FCP.

Total hip arthroplasty in nine canine hind limb amputees: a retrospective study.

OBJECTIVE: To determine the outcome of total hip arthroplasty in canine hindlimb amputees. STUDY DESIGN: Retrospective evaluation of clinical cases. METHODS: Data recorded from the medical records of nine dogs included patient signalment, indication for amputation and total hip arthroplasty (THA), interval between amputation and THA, and surgical complications. Radiographs were used to assess implant orientation and evidence of complications. Functional outcome was assessed using direct patient evaluation by one of the authors or primary surgeons, or through telephone interview between the primary author and the owner. RESULTS: Seven dogs ultimately had a good or excellent clinical results. Complications occurred in five dogs. Four dogs luxated the prosthetic joint without an obvious traumatic event within 9 weeks of the initial surgery. Revision surgeries resulted in successful coxofemoral reduction in three of four dogs. There were no clinical or radiographic findings suggestive of implant loosening or infection. CONCLUSION: THA can be a successful salvage procedure in the canine hindlimb amputee with disabling, non-neoplastic, noninfectious coxofemoral disease. The risk of luxation in the early postoperative period is high and revision surgery is required for stabilization.

Effect of surgical technique and use of a rigid centralizing device on stem positioning and geometric reconstruction in the sagittal plane during total hip replacement in canine cadavers.

OBJECTIVE: To determine the effect of surgical technique and use of a rigid centralizing device on stem positioning and geometric reconstruction in the sagittal plane during total hip replacement in dogs. SAMPLE POPULATION: Bilateral femurs from 8 adult mixed-breed canine cadavers. PROCEDURE: Femurs were prepared for femoral stem implantation, using 4 variations in technique. Proximal femoral reconstruction and femoral stem positioning were evaluated on radiographs. RESULTS: Implants evaluated in this study accurately reconstructed displacement of the femoral head of the intact canine femur in the sagittal plane. Centralization of the distal aspect of the stem was optimized by use of an undersized femoral stem. Ostectomy at the level of the lesser trochanter resulted in the smallest diaphysis-to-implant angle. Anteversion and retroversion of implants significantly decreased the distance between the distal tip of the implant and the adjacent cortex, compared with normoversion. The centralizing device significantly increased the minimum distance between the distal tip of the implant and adjacent cortex but did not improve the odds of actually centralizing the tip of the implant. CONCLUSIONS AND CLINICAL RELEVANCE: Malpositioning of implants in the sagittal plane may be minimized through ostectomy at the lesser trochanter and use of an undersized implant positioned in normoversion. Use of a polymethylmethacrylate centralizing device will help eliminate contact between the implant tip and adjacent cortex. Implantation of an undersized femoral component, avoidance of substantial anteversion or retroversion, and use of a rigid centralizing device are recommended when using the prosthesis described-for total hip replacement of dogs.

Transverse plane evaluation of the effects of surgical technique on stem positioning and geometry of reconstruction in canine total hip replacement.

OBJECTIVES: To test whether femoral ostectomy level, subtrochanteric bone mass removal, and stemsize selection significantly affect stem positioning in canine total hip replacement, and to determine ability of the femoral stem component to restore geometry of the normal femoral head and neck. SAMPLE POPULATION: Femurs from 8 adult mixed-breed canine cadavers. PROCEDURE: Femurs were systematically prepared, using 8 combinations of 3 surgical preparation techniques that included level of ostectomy (cervical isthmus vs lesser trochanter), subtrochanteric bone block removal, and femoral stem size (recommended, undersized). Computer-aided analysis of specimen photographs was used to evaluate femoral head offset and position and variability of femoral stem positioning for each of the preparation combinations. RESULTS: Original femoral head offset and position were reconstructed to within a mean of 0.052 and 0.031 cm, respectively, using an undersized femoral stem after ostectomy at the level of the lesser trochanter. Implantation of an undersized femoral stem after subtrochanteric bone block removal improved ability to centralize the distal tip of the implant and reduce the angle between the femoral diaphyseal and implant axes. Ostectomy at the level of the cervical isthmus tended to force femoral implants into a varus position, and ostectomy at the level of the lesser trochanter tended to force implants into a valgus position. CONCLUSIONS: Geometry of normal canine femurs was most closely reconstructed by implantation of an undersized femoral component after ostectomy at the level of the lesser trochanter. Implantation of an undersized femoral component after subtrochanteric bone block removal resulted in the best alignment and centralization of the stem.

Correlation of clinical, radiographic, and surgical localization of intervertebral disc extrusion in small-breed dogs: a prospective study of 50 cases.

OBJECTIVE: To compare prospectively clinical, radiographic, and surgical findings of intervertebral disc extrusion (IDE) localization in small-breed dogs and to determine the best means of lesion localization for the purpose of hemilaminectomy. STUDY DESIGN: Clinical, radiographic, and surgical findings of small-breed dogs with thoracolumbar IDE were prospectively compared for agreement on lesion localization. SAMPLE POPULATION: 50 small-breed dogs with IDE treated at the three participating veterinary hospitals were included in the study if no other confounding diseases were identified and if the owner gave permission for diagnostic tests and surgery. METHODS: Clinical and surgical findings were recorded by the surgeon assigned to the case. Radiographic studies were evaluated independently by two radiologists blinded as to the clinical and surgical findings. kappa values and 95% confidence intervals were calculated for agreement on lesion localization by clinical, radiographic, and surgical means and for agreement between radiologists. RESULTS: kappa values for agreement of lesion localization were as follows: clinical versus surgical, 0.595; radiologist A versus radiologist B, 0.81; radiologist A versus surgical findings, 0.60; radiologist B versus surgical findings, 0.71. Both radiologists' interpretation of IDE localization agreed with surgical localization in 60% of cases. CONCLUSIONS: Clinical lateralization of IDE was found to be the least reliable factor of those studied for determining on which side the hemilaminectomy should be performed. Results of this study differ from those of previous studies examining the reliability of myelography to localize the site of IDE accurately. The results of this study further suggest that surgery may not be an absolute standard for determination of the localization of IDE in small-breed dogs. CLINICAL RELEVANCE: Intervertebral disc extrusion in small-breed dogs frequently results in bilateral distribution of extruded material. Computed tomography or magnetic resonance imaging may be necessary to delineate completely the distribution of extruded disc material in IDE.

Calcinosis circumscripta of the thoracic wall in a German shepherd dog.

Calcinosis circumscripta of the left thoracic wall was diagnosed in a six-month-old, female German shepherd dog by thoracic radiography and ultrasonographic-guided biopsy. The puppy developed the lesion following a left thoracotomy to repair a patent ductus arteriosus. Complete resolution occurred following surgical excision of the lesion. Calcinosis circumscripta associated with routine surgical manipulation and postoperative inflammation has been reported rarely but should be suspected when a focal, mineralized lesion occurs at a previous surgical site, especially in German shepherd dogs.

Application of ventral pins and polymethylmethacrylate for the management of atlantoaxial instability: results in nine dogs.

OBJECTIVE: The purpose of this report was to determine the efficacy of the application of ventral pins and polymethylmethacrylate for the management of congenital and traumatic atlantoaxial instability (AAI) in dogs. STUDY DESIGN: Medical records and radiographs of nine dogs with AAI were reviewed for neurological deficits, clinical diagnosis, surgical technique, and long-term outcome. SAMPLE POPULATION: Six toy breed dogs with congenital AAI and three medium or large breed dogs with traumatic AAI were identified for inclusion in the study. METHODS: The atlantoaxial joints of nine dogs with AAI were surgically stabilized using ventral application of pins and polymethylmethacrylate. Follow-up evaluation for resolution of clinical signs and possible complications of surgery was performed in all dogs. The median follow-up time for surviving dogs (8) was 11.5 months with a mean of 13 months. RESULTS: An excellent outcome was identified in five patients. Three dogs had a good outcome and one dog died of respiratory complications. Cervical pain was eliminated or significantly reduced in all dogs that survived and none of the dogs had major residual neurological deficits. CONCLUSIONS: Arthrodesis could not be confirmed on follow-up radiographs due to the presence of the polymethylmethacrylate; however, adequate stabilization of C1-C2 appears to have been achieved based on the resolution of clinical signs. CLINICAL RELEVANCE: Application of ventral pins and polymethylmethacrylate is an effective means of surgical treatment for congenital and traumatic AAI.

Biomechanics of the thoracolumbar vertebral column of dogs during lateral bending.

OBJECTIVE: To study biomechanical characteristics of the normal and surgically altered canine thoracolumbar vertebral column to determine the effects of surgery and trauma on lateral stability. ANIMALS: The T13-L1 vertebral motion units of 48 mixed-breed dogs were dissected free of surrounding musculature and prepared for biomechanical testing by cross-pinning the vertebral bodies and mounting in polymethylmethacrylate. PROCEDURE: Normal and surgically altered spinal specimens were subjected to lateral bending. The mean slope of the bending moment versus angular displacement curve and the load to failure were compared between treatment groups and significance was determined by the method of least squares (P < 0.05). Specimens were surgically altered by facetectomy, lateral fenestration, diskectomy, and combinations of these procedures. Each specimen was subjected to lateral bending to failure at a rate of 2.5 cm/min in a swing arm bending jig designed to simulate 4-point bending and subject the specimen to pure bending. RESULTS: Only specimens undergoing diskectomy had a significant decrease in slope and load at failure. Unilateral and bilateral facetectomies and fenestration induced a nonsignificant decrease in stiffness, compared with control specimens. CONCLUSIONS: Fenestrations and facetectomies do not appear to increase the risk of injury to the canine thora-columbar spinal cord during lateral bending. CLINICAL RELEVANCE: Fenestrations and facetectomies, as used in routine laminectomies, may be performed without concern for significant destabilization of the spine in lateral bending; however, it is possible that thoracolumbar spinal fractures involving only the vertebral body may significantly destabilize the spine in all modes of bending.

Magnetic resonance imaging of the brain for diagnosis of neurocysticercosis in a dog.

Neurocysticercosis was diagnosed in a 2-year-old spayed Whippet by use of magnetic resonance imaging. The dog was evaluated because of a 3-month history of slowly progressive balance and directional abnormalities, which were indicative of brain stem disease. Magnetic resonance imaging of the brain and CSF analysis were chosen as the best diagnostic modalities for determination of the primary disease. Results of CSF analysis were within reference ranges. Examination of T1-weighted, contrast-enhanced, 3-mm-thick axial, sagittal, and coronal views of the brain revealed multiple cyst-like lesions. The cysts had high-signal-intensity, ring-like peripheral margins and were located in the subdural portion of the left occipital lobe and the dorsal midline and right dorsolateral aspect of the brain stem. A tentative diagnosis of neurocysticercosis was made on the basis of similar findings in human beings with this disease. Treatment with albendazole and prednisone was initiated, and clinical signs resolved during the following weeks. Repeat magnetic resonance imaging confirmed resolution of the disease.

Inadvertent prostatectomy as a complication of cryptorchidectomy in four dogs.

Inadvertent prostatectomy was identified as a complication of cryptorchidectomy in four dogs. Surgical correction of the resulting urethral trauma was attempted in each case. One case was euthanized due to a poor prognosis for recovery. Three cases survived without clinical evidence of urinary incontinence. Inadvertent prostatectomy during cryptorchidectomy may be avoided by adequate surgical exposure and proper identification of the abdominally retained testicle.

Transsplenic portal catheterization. Surgical technique and use in two dogs with portosystemic shunts.

The portal vasculature can be accessed by using a through-the-needle catheter system to pass a catheter through the splenic parenchyma and into a major splenic vein at the hilus. The authors have termed this technique transsplenic portal catheterization (TPC). Transsplenic portal catheterization is indicated for portal angiography, portal pressure measurement, and chronic portal blood sampling. Clinical applications of this technique include use in diagnosis and surgical management of portosystemic shunts and differentiation of prehepatic, hepatic, and posthepatic hypertension. This report describes the technique of transsplenic portal catheterization. Clinical use of this technique in two cases of portosystemic shunts are included.