The Effect of Triple Pelvic Osteotomy on Hip Force in Dysplastic Dogs: A Theoretical Analysis

The effect of a triple pelvic osteotomy (TPO) procedure on the forces acting about the hip joint was examined in five dysplastic canine hips using a previously described theoretical analysis. Hip reaction force (F_h) and its angle of application (θ_h) were calculated from radiographic measurements made before and after TPO procedures which sequentially increased acetabular ventroversion from 0° to 20°, 30°, and 40°. The results of the in vitro study showed that F_h decreased with increasing acetabular ventroversion reaching an asymptotic value between 30° and 40°. The decrease in F_h corresponded to an increase in θ_h toward the vertical, with statistical significance found in both F_h and θ_h between 0° and 20°. The changes observed in F_h and θ_h after TPO were attributed to the medialization of the femoral head resulting from the reduction of the subluxated head. The results of this study suggest that the noted reduction in the magnitude of the forces acting on the hip joint may act in concert with increased coverage of the femoral head to effect the beneficial clinical results observed with the TPO procedure.     

Effects of pubic symphysiodesis in dysplastic puppies

OBJECTIVE--To determine the long-term effects of juvenile pubic symphysiodesis (JPS) in dysplastic puppies. STUDY DESIGN--Prospective, randomized, clinical trial. ANIMALS--Seven dysplastic Chesapeake Bay retrievers and 2 beagle-crosses (BX1 and 2). METHODS--Five puppies had JPS performed with electrocauterization at 12, 16, 20, 22, and 24 weeks of age, respectively. Two puppies served as controls. BX1 and BX2 were used to obtain biopsies of the symphysis. Hips were evaluated for: pelvic development (transverse computerized tomography for acetabular angle [AA] and dorsal acetabular rim angle [DARA]); laxity [hip extended and stress radiography [distraction index (DI)]); Ortolani maneuver with reduction angles; acetabular coverage (Norberg angles); and function (coxofemoral range of motion, hip pain, and gait analysis by force-plate technique at 44 and 137 weeks of age). RESULTS--The pubis fused prematurely in every puppy that was operated on with the JPS technique. Greater acetabular responses were related to younger ages at surgery. The final mean AA in dogs that had JPS was 25 degrees greater than preoperative values; 40% increased over control. The DARA final mean was 10 degrees, 52% less than preoperative values and 46% less than control. The final mean DI in dogs having JPS was 0.28, 47% improved over preoperative values and 58% better than control. Mean pelvic dimensions in dogs that had JPS were 18% less than control. Gait analyses were normal for all dogs at 137 weeks. No urinary or bowel complications occurred. CONCLUSIONS--Significant ventrolateral acetabular rotation, increased hip coverage, diminished hip laxity, normal pain-free gait, and insignificantly reduced pelvic size occurred after JPS. CLINICAL SIGNIFICANCE--Dysplastic hips in young dogs were significantly improved by JPS.     

Juvenile Pubic Symphysiodesis and Juvenile Pubic Symphysiodesis Associated with Pectineus Myotomy: Short‐Term Outcome in 56 Dysplastic Puppies

Objectives— (1) To compare short‐term outcome of juvenile pubic symphysiodesis (JPS) in puppies aged 12–17 weeks with lax hips (group JPS1), in puppies aged 18–22 weeks (group JPS2), and control (group C) puppies; and (2) to document outcome of bilateral pectineus myotomy (PM) associated with JPS in 18–22‐week‐old puppies (group JPS–PM). Study Design— Prospective study. Methods— Puppies (12–22 weeks) from large and giant breed dogs with a combination of a positive Ortolani sign, poor acetabular coverage (Norberg angle [NA]≤100°), and a subluxation index (SI) >0.5 for one or both hips were selected. Puppies aged <18 weeks were randomly assigned to group JPS1 or C. Puppies aged 18–22 weeks were randomly assigned to group JPS2, JPS–PM, or C. Three to 4 months later, surgery was considered successful in pain‐free dogs with negative Ortolani sign, normalized acetabular coverage (NA≥105°), and SI>0.5. Success rates were compared using Fisher's exact tests: JPS1 versus JPS2 versus C; JPS2 versus JPS–PM. Significance was set at P<.05. Results— All dysplastic hips from nonoperated (C) groups were dysplastic at follow‐up, meaning that our criteria for case selection were accurate. JPS1 had significantly better success rate than JPS2 (85 versus 17.8%, respectively). JPS–PM dysplastic hips failed to demonstrate a better outcome than JPS2 hips. Clinical Relevance— This study confirms, on a large series of dysplastic hips, the age‐dependent effects of JPS, with better results if performed before 18 weeks of age. There is no benefit of adding PM to the procedure in candidates >18 weeks at surgery.     

Acetabular ventroversion with double pelvic osteotomy versus triple pelvic osteotomy: a cadaveric study in dogs

Objective: To determine which of 3 different plate angles (20°, 25°, 30°) used in double pelvic osteotomy (DPO) would result in the most similar acetabular angle (AA) achieved with a 20° triple pelvic osteotomy (TPO) technique in dogs. Study Design: Experimental anatomic study. Animals: Cadaveric canine pelves (n=8). Methods: Transverse plane computed tomographic images of cadaveric pelves with intact sacroiliac joints, mounted in a custom jig, were made (baseline) and again after DPO (20°, 25°, 30°) and TPO (20°) and pelvic angles measured in 6 transverse planes. Pelvic angles of the 3 DPO techniques were compared with TPO using concordance correlation to determine which DPO angle resulted in an acetabular ventroversion angle closest to TPO. Results: Mean ± SD AAs were 32.89 ± 2.23 (baseline), 47.39 ± 4.39 (20° DPO), 51.43 ± 5.06 (25° DPO), 54.75 ± 4.38 (30° DPO), and 50.20 ± 5.76 (20° TPO). Concordance correlations for the AA compared with 20° TPO were 0.027 (baseline), 0.721 (20° DPO), 0.902 (25° DPO), and 0.593 (30° DPO). A concordance correlation of ≥0.8 indicates good correlation. Conclusions: A 25° DPO is most similar in acetabular ventroversion to 20° TPO (concordance correlation, 0.902).     

Measurement of femoral angles in four dog breeds

Objective— To develop a standard method of measurement for femoral angles and report values for normal Labrador Retrievers, Golden Retrievers, German Shepherds, and Rottweilers.
Study Design— Retrospective evaluation of canine pelvis and femoral radiographs.
Sample Population— Radiographs of Labrador Retrievers, Golden Retrievers, German Shepherds, and Rottweilers (n=100 for each breed).
Methods— Anatomic lateral distal and proximal femoral angle, mechanical lateral distal and proximal femoral angle, and femoral angle of inclination were measured from radiographs.
Results— For the 4 breeds (Labrador Retrievers, Golden Retrievers, German Shepherds, and Rottweilers, respectively) anatomic lateral distal femoral angles were 97°, 97°, 94°, and 98°; mechanical lateral distal femoral angles were 100°, 100°, 97°, and 100°; anatomic lateral proximal femoral angles were 103°, 98°, 101°, and 96°; mechanical lateral proximal femoral angles were 100°, 95°, 97°, and 93°; and inclination angles were 134°, 134°, 132°, and 137°. Labrador Retrievers, Golden Retrievers, and Rottweilers had significantly higher values for both anatomic and mechanical lateral distal femoral angle than German Shepherds. Anatomic and mechanical lateral proximal angles were greatest for Labrador Retrievers and lowest for Rottweilers.
Conclusion— Anatomic and mechanical femoral joint angles vary between breeds of dogs.
Clinical Relevance— Values for femoral joint angles may be clinically useful for angular limb deformity diagnosis, treatment, and assessment.     

Radiographic measurement of the proximal and distal mechanical joint angles in the canine tibia

Objective— To describe a method for radiographic measurement of proximal and distal mechanical joint angles of the canine tibia. Normal ranges were established for a population of dogs, and specifically, Labrador retrievers, with cranial cruciate ligament rupture.
Study Design— Retrospective study.
Sample Population— Tibiae (n=105) of dogs evaluated for cranial cruciate ligament rupture; 70 tibiae were from Labrador retrievers, 35 tibiae were from other breeds.
Methods— Anatomic landmarks were established and craniocaudal radiographs were used to measure the mechanical medial proximal (mMPTA) and distal (mMDTA) tibial angles in the frontal plane.
Results— Means (±SD) for all tibiae were mMPTA, 93.30±1.78°, and mMDTA, 95.99±2.70°. For Labrador retrievers, means were mMPTA, 93.38±1.81°, and mMDTA 96.34±2.51°. No significant differences were detected between Labrador Retrievers and non-Labrador retrievers with respect to mMPTA (power=0.5) or mMDTA (power=0.342). Labrador Retrievers were significantly younger than non-Labradors ( P =.003).
Conclusion— A method for measurement of the mechanical joint angles of the canine tibia in the frontal plane was established and reference ranges for a population of dogs and Labrador Retrievers with cranial cruciate ligament rupture are reported.
Clinical Relevance— The established method of measurement and references ranges can be used to aid in diagnosis, determining indications, and surgical planning for angular limb deformities of the tibia, especially when affected bilaterally. The methodology and reference values may also be used for postoperative critique.     

Interobserver Repeatability of Measurements on Computed Tomography Images of Lax Canine Hip Joints from Youth to Maturity

Objectives— To determine interobserver repeatability of measurements on computed tomography (CT) images of lax canine hip joints at different ages and in the presence of degenerative joint disease at maturity. Study Design— Longitudinal observational investigation. Animals— Sibling crossbreed hounds. Methods— Pelvic CT was performed at 20, 24, 32, 48, 68, and 104 weeks of age. Measures were performed on 3 contiguous two‐dimensional (2D) transverse CT images of both hips at each time point by 3 investigators. Center‐edge angle (CEA), horizontal toit externe angle (HTEA), ventral (VASA), dorsal (DASA), and horizontal (HASA) acetabular sector angles, acetabular index (AI), and percent femoral head coverage (CPC) were measured. Interobserver repeatability was quantified with the intraclass correlation coefficient (ICC). Satisfactory repeatability was considered when ICC≥0.75. Results— DASA, CEA, and CPC were repeatable in all age groups. HASA and HTEA were repeatable for all but 1 time point. At 20 weeks of age, all measures but AI were repeatable, and at 104 weeks of age, DASA, CEA, CPC, and HASA were repeatable. Measures were repeatable in hips with and without degenerative changes with the exceptions of AI and HASA in normal hips and VASA and HTEA in osteoarthritic hips. Conclusions— Most 2D CT measurements examined were repeatable regardless of age or joint disease. Clinical Relevance— Two‐dimensional CT measures may augment current techniques for assessing joint changes in lax canine hips.     

Sacroiliac Luxation in the Cat: Defining a Safe Corridor in the Dorsoventral Plane for Screw Insertion in Lag Fashion

Objective— To define a safe corridor in the dorsoventral plane within the feline sacral body for placement of screws inserted in lag fashion for repair of sacroiliac luxation.
Study Design— Anatomic study.
Sample Population— Frozen cadaveric feline sacra.
Methods— Feline sacra (n=20) were used to perform a radiographic study to define a safe corridor to a depth of 66% of the sacral body width. Two drill start points (A and B) were evaluated. Dorsal exit from the safe corridor was considered unacceptable.
Results— Forty safe corridors were measured. The mean articular surface was 100±6.4° from horizontal. Mean maximum, optimum, and minimum safe corridor drill angles from drill point A were 107±6.8°, 97±6.9°, and 87±7.2°, respectively, from the articular surface. Mean maximum, optimum, and minimum angles from drill point B were 109±7.2°, 99±7.1°, and 89.5±7.2°, respectively. Point B increased the risk of ventral exit from the sacral body.
Conclusions— Point A and a drill angle of 90±4° for drilling of the feline sacral body is recommended. This margin for error risks ventral exit from the body in 23/40 (58%) of the sacra in this study. Reduction of the margin for error to ±2° would reduce the risk of ventral exit to 14/40 (35%) of the sacra in this study.
Clinical Relevance— Drilling at 90° to the feline sacral articular surface is recommended. Findings from this study present a strong case for use of angled drill guides.     

Measurement of humeroradial and humeroulnar transarticular joint forces in the canine elbow joint after humeral wedge and humeral slide osteotomies

Objective— To determine the effect of humeral wedge and humeral slide osteotomies on force distribution between the articular surfaces of the humerus and the radius and ulna in normal canine thoracic limbs.
Study Design— In vitro mechanical testing.
Sample population— Cadaveric canine right thoracic limbs (n=12).
Methods— Transarticular elbow force maps were measured using a tactile array pressure sensor in elbow joints of axially aligned limbs under 200 N axial load before and after humeral wedge and humeral slide osteotomies.
Results— Loading induced 2 distinct areas of high forces that corresponded with the proximal articular surfaces of the radius and ulna. Mean force on the proximal articular surface of the ulna was reduced by 25% and 28% after 4 and 8 mm sliding osteotomies, respectively. Statistically significant differences were not observed for the wedge osteotomies.
Conclusion— Humeral slide osteotomy significantly decreases force on the proximal articular surface of the ulna.
Clinical Relevance— The proximal articular surface of the ulna contributes significantly to load transfer through the canine elbow joint. Abnormalities that significantly increase this force might contribute to canine elbow dysplasia, specifically fragmentation of the medial coronoid process and osteochondritis dissecans of the medial aspect of the humeral condyle. Under the conditions studied, the overall reduction in mean joint surface force across the proximal articular surface of the ulna after humeral slide osteotomy indicates that this technique merits further investigation for potential use in medial compartmental osteoarthritis of the canine elbow joint.     

Juvenile pubic symphysiodesis in dysplastic puppies at 15 and 20 weeks of age

OBJECTIVE: To examine the effects of juvenile pubic symphysiodesis (JPS) on hip joint conformation, hip laxity, gait, and the development of degenerative joint disease (DJD) in dysplastic puppies operated at 15 and 20 weeks of age. STUDY DESIGN: Randomized controlled prospective study. ANIMALS-Eighteen female hound puppies with increased hip laxity. METHODS: Puppies were randomized to 1 of 4 treatment groups: JPS at 15 weeks of age (n = 6), sham-operated control at 15 weeks of age (n = 3), JPS at 20 weeks of age (n = 6), and sham-operated control at 20 weeks of age (n = 3). Hip extension with pain scoring, Ortolani palpation, hip reduction angle measurement (HRA), PennHIP radiography (University of Pennsylvania) with measurement of distraction index, Norberg angle measurement, and transverse computed tomographic imaging to measure acetabular angle (AA) and dorsal acetabular rim angle (DARA), were tested preoperatively, and at 1 and 2 years of age. RESULTS: JPS resulted in significant changes in AA, HRA, DARA, and conversion to Ortolani negative status. Larger and more rapid changes in hip conformation were seen when surgery was performed at 15 weeks of age. No significant changes were identified in control dogs. Twenty-five percent of JPS dogs developed DJD whereas 83% of control dogs developed DJD. CONCLUSIONS: JPS resulted in significant improvements in hip joint conformation and hip laxity in dysplastic puppies treated at 15 and 20 weeks of age. Improvements in conformation were significantly greater when surgery was performed at 15 weeks of age. CLINICAL RELEVANCE: JPS appears to be a promising treatment for hip dysplasia and is a safe and technically simple procedure to perform.     

Radiographic measurement of canine tibial angles in the sagittal plane

Objective— To describe a method for radiographic measurement of the mechanical joint angles of the tibia in the sagittal plane and report reference ranges for a population of dogs with cranial cruciate ligament disease, and specifically for Labrador Retrievers.
Study Design— Retrospective evaluation of radiographs.
Animals— Canine tibia (n=150) of dogs evaluated for cranial cruciate ligament disease; 104 tibiae were from Labrador Retrievers, 46 tibiae were from other medium- to large-breed dogs.
Methods— Medial-lateral radiographs were used to establish anatomic landmarks and measure the mechanical cranial distal tibial angle (mCrDTA) and mechanical caudal proximal tibial angle (mCaPTA).
Results— For all tibiae mean mCrDTA was 81.6° and mCaPTA, 63.6°. For Labrador Retriever tibiae mean mCrDTA was 81.7° and mCaPTA, 63.8°. For non-Labradors, means mCrDTA was 81.5° and mCaPTA, 63°. Labrador Retrievers were significantly younger than non-Labradors in our study population. No significant differences were noted between Labrador Retrievers and non-Labradors for mCrDTA or mCaPTA and correlations between mCrDTA and mCaPTA were neither strong nor significant.
Conclusion— A method was established for radiographic measurement of mechanical joint angles of the canine tibia in the sagittal plane. Reference ranges are reported for a population of Labrador Retrievers and a population of non-Labradors with cranial cruciate ligament disease.
Clinical Relevance— Measurement method and reference ranges provided for mechanical tibial angles may be used to aid in diagnosis, surgical planning, and postoperative critique for hindlimb angular deformities.     

Changes in Third Carpal Bone Articular Cartilage After Synovectomy in Normal and Inflamed Joints

Objective —To determine if arthroscopic synovectomy in normal and inflamed joints had temporal or site-related effects on articular cartilage.
Study Design —Alterations in equine third carpal bone articular cartilage were studied at two time periods: groups 1 and 2 (6 weeks) and groups 3 and 4 (2 weeks) after synovectomy in normal (groups 2 and 4) and inflamed carpi (groups 1 and 3).
Animal Population —16 carpi from eight horses.
Methods —Biochemical and biomechanical properties of dorsal and palmar articular cartilage were determined by radiolabeling, proteoglycan (PG) extraction, chromatography, electrophoresis, and indentation testing.
Results —Synovectomy in inflamed joints produced the greatest concentration of newly synthesized PG in articular cartilage by 2 weeks. Synovectomy in normal joints produced significantly greater newly synthesized PG in articular cartilage by 6 weeks. Endogenous PG was only significantly greater in inflamed joints after 6 weeks. Dorsal sites had greater newly synthesized and endogenous PG in some groups. Chromatographic profiles of newly synthesized PG demonstrated early and late PG peaks. Electrophoresis of late PG peak showed a toluidine blue-positive band that comigrated with human A1D1 PG monomer in the two groups with the most newly synthesized PG. This band was reactive with monoclonal antibody 1C6 specific for the hyaluronic acid-binding region of aggrecan. For the material properties evaluated, only Poisson's ratio was significantly decreased between groups as a function of time (6 weeks < 2 weeks), and this was most pronounced in the thicker dorsal sites.
Conclusions —Synovectomy in inflamed joints produced site-specific, significantly greater responses in articular cartilage as compared with synovectomy in normal joints.
Clinical Relevance —Synovectomy may not be beneficial to the articular cartilage in inflamed joints.     

Use of a four pin and methylmethacrylate fixation in L7 and the iliac body to stabilize lumbosacral fracture-luxations: a clinical and anatomic study

Objectives— To describe the clinical outcome of a 4 pin lumbosacral fixation technique for lumbosacral fracture–luxations, and to refine placement technique for iliac pins based on canine cadaver studies.
Study Design— Retrospective and anatomic study.
Sample Population— Dogs (n=5) with lumbosacral fracture-luxations and 8 cadaveric canine pelvi.
Methods— Lumbosacral fracture–luxations were stabilized with a 4 pin (positive-profile threaded) and bone cement fixation. Caudal pins were inserted in the iliac body and cranial pins were inserted into the L7 or L6 pedicle and body. Follow-up examinations and radiographs were performed to assess patient outcome. Intramedullary pins were inserted into the iliac bodies of 8 cadaver pelvi. Radiographs were taken to measure pin insertion angles and define ideal insertion angles that would maximize pin purchase in the ilium.
Results— Follow-up neurologic examination was normal in 4 dogs. Radiographic healing of the fracture was evident in 5 dogs. One implant failure occurred but did not require re-operation. For cadaver iliac pins, mean craniocaudal insertion angle was 29° and mean lateromedial insertion angle was 20°.
Conclusions— Four pin and bone cement fixation effectively stabilizes lumbosacral fracture luxations. The iliac body provides ample bone stock, which can be maximized using an average craniocaudal pin trajectory of 29° and an average lateromedial pin trajectory of 20°.
Clinical Relevance— Lumbosacral fracture–luxations can be stabilized with 4 pin and bone cement fixation in the lumbar vertebrae and iliac body, using 29 and 20° as guidelines for the craniocaudal and lateromedial pin insertion angles in the ilium.     

The Effects of Active Peripheral Skin Warming on Perioperative Hypothermia in Dogs

Objective — This study evaluates the efficacy of three perioperative warming protocols to improve control of body temperature in anesthetized dogs.
Study Design — A randomized controlled clinical trial.
Animals or Sample Population — Thirty-two client-owned dogs.
Methods — We prospectively studied dogs entering the University of Pennsylvania Veterinary Teaching Hospital for orthopedic or dental procedures and assigned them to one of three perianes-thetic warming protocols. Group 1 (n = 10) had a single circulating warm water mattress applied over the trunk (single-trunk warming). Group 2 (n = 12) had two circulating warm water mattresses, one placed over and one under the trunk (double-trunk warming). Group 3 (n = 10) had warm circulating mattresses applied only around the feet and legs of all available limbs (peripheral warming). The warm water mattresses were prewarmed and maintained at 40°C (104°F) and applied immediately after induction of general anesthesia. All dogs had a layer of thick terry cloth toweling beneath and above the trunk. Body temperature measurements were recorded every 15 minutes for the first 2.5 hours of anesthesia.
Results — The lowest mean temperature for dogs in group 3 was 37.4 ± 0.2°C (99.5°F), compared with 36.4 ± 0.2°C (97.4°F) and 36.7 ± 0.2°C (98.0°F) in groups 1 and 2, respectively.
Conclusions — Dogs in the peripheral warming group maintained significantly higher core body temperatures than dogs in either trunk warming groups throughout the 2.5-hour study period.
Clinical Relevance — To maintain body heat in dogs during anesthesia, it is more effective to warm the feet and legs than to warm the trunk.     

Short-Term Hemodynamic Evaluation of Circumferential Mitral Annuloplasty for Correction of Mitral Valve Regurgitation in Dogs

Objective —To determine the short-term hemodynamic effects associated with circumferential mitral annuloplasty (CMA) in dogs with mitral regurgitation.
Study Design —Prospective experimental study.
Animals —Seven healthy adult mongrel dogs.
Methods —Mitral regurgitation was surgically induced, and annular dilation occurred. Echocardiography and cardiac catheterization were used to determine forward ejection fraction (FEF), regurgitant fraction (RF), pulmonary capillary wedge pressure (PCWP), and annular diameter before and immediately after CMA in five dogs. FEF and RF were also evaluated 7 days after annuloplasty.
Results —Mean annular diameter and PCWP were significantly reduced immediately after CMA. Significant increases in FEF of 19% and 22% were shown immediately and 7 days after CMA. Significant reductions in RF of 19% and 22% were also shown immediately and 7 days after annuloplasty.
Conclusions —Sustained hemodynamic benefits and a reduction in annular diameter were achieved by CMA in a canine model of mitral regurgitation.
Clinical Implications—CMA may be a suitable treatment for heart failure because of mitral regurgitation when early signs of cardiovascular decompensation persist despite appropriate medical management.     

Fragmented Coronoid Process and Incomplete Ossification of the Humeral Condyle in a Rottweiler

Objective —To describe incomplete ossification of the humeral condyle and fragmentation of the medial coronoid process in a Rottweiler.
Study Design —Clinical report.
Animal Population —A 4-year-old sexually intact male Rottweiler.
Methods —Physical examination, radiography, and computed tomography of both elbow joints were performed initially. Drill holes were made across the humeral condyle to promote ossification. Radiography and computed tomography were repeated 14 weeks later. Radiography was repeated 15 months later. A mild, intermittent lameness remained.
Results —Preoperatively a radiolucent line was present across the right humeral condyle. This radiolucent line remained unchanged 14 weeks after drill holes were made across the condyle.
Conclusions —Incomplete ossification of the humeral condyle is present in Rottweilers.
Clinical Relevance —Incomplete ossification of the humeral condyle is present in Rottweilers and may coexist with fragmentation of the medial coronoid process in that breed. The radiographic diagnosis may be difficult because precise positioning is required to see the area of incomplete ossification. Computed tomography may be required to confirm the presence of incomplete ossification of the humeral condyle. Drilling holes across the humeral condyle does not appear to lead to union of the area of incomplete ossification.     

COMPARISON OF CLINICAL, RADIOGRAPHIC, COMPUTED TOMOGRAPHIC, AND MAGNETIC RESONANCE IMAGING METHODS FOR EARLY PREDICTION OF CANINE HIP LAXITY AND DYSPLASIA

The purpose of the study was to use two palpation methods (Bardens and Ortolani), a radiographic distraction view, three computed tomography (CT) measurements (dorsolateral subluxation score, the lateral center-edge angle, and acetabular ventroversion angle) and two magnetic resonance (MR) imaging hip studies (synovial fluid and acetabular depth indices) in the early monitoring of hip morphology and laxity in 7–9 week old puppies; and in a follow-up study to compare their accuracy in predicting later hip laxity and dysplasia. The MR imaging study was performed with the dog in dorsal recumbency and the CT study with the animal in a weight-bearing position. There was no association between clinical laxity with later hip laxity or dysplasia. The dorsolateral subluxation score and the lateral center-edge angle were characterized by a weak negative correlation with later radiographic passive hip laxity (−0.26< r <−0.38, P <0.05) but its association with hip dysplasia was not significant. There was an association between early radiographic passive hip laxity and synovial fluid index with later passive hip laxity (0.41< r <0.55, P <0.05) and this was significantly different in dysplastic vs. nondysplastic hips ( P <0.05). There was no association between the remaining variables and later hip laxity or dysplasia. The overlapping ranges of early passive hip laxity and synovial fluid index for hip dysplasia grades and the moderate correlations with the later passive hip laxity make the results of these variables unreliable for use in predicting hip laxity and dysplasia susceptibility.     

Biomechanical Comparison of the Trocar Tip Point and the Hollow Ground Tip Point for Smooth External Skeletal Fixation Pins

Objective —To compare the insertional characteristics of external fixator pins with hollow ground (HG), modified HG, and trocar (T) points.
Study Design —An acute, in vitro biomechanical evaluation.
Sample Population—Thirteen radii from canine cadavers.
Methods —A total of 16 T-tipped and 16 HG-tipped pins were inserted into 8 canine radii. Ten pins of each modification of the HG tip (length of the cutting edge reduced by 0.127 mm and 0.254 mm, respectively) were inserted into another five radii. All pins were inserted with low-speed power drilling and 80 N drilling load. Differences between peak tip temperature, drilling energy, and pullout force were determined for each pin type at both diaphyseal and metaphyseal locations.
Results —HG-tipped pins showed a 40% lower tip temperature in diaphyseal bone, a 25% reduction in drilling energy in diaphyseal bone, and a reduction of pullout force in both diaphyseal (65%) and metaphyseal (50%) bone compared with T-tipped pins. HG 0.254-mm pins generated higher tip temperatures and had greater pullout than HG pins in diaphyseal bone.
Conclusions —The HG tip was a more efficient design; however, the reduction in pullout force suggests that, because a better hole was drilled, radial preload is reduced. Reduction of the cutting edge by 0.254 mm increased the pullout force but also increased the temperatures.
Clinical Relevance —Thermal and microstructural damage are reduced by the HG tip, but pin-bone interface stability is also compromised. The use of a tip with 0.254 mm reduction in the cutting edge may optimize the biological and mechanical factors at the pin-bone interface.     

Comparison of nuclear morphometric parameters in cytologic smears and histologic sections of spontaneous canine tumors

Background — Nuclear morphometry may provide useful diagnostic and prognostic information for neoplasms in animals. Most available data have been obtained from histologic sections. Nuclear morphometry of cytologic smears may provide important pre-operative information.
Objectives — The goal of this study was to compare nuclear morphometric parameters in cytologic smears and histologic sections from spontaneous canine tumors.
Methods — Mean nuclear area (MNA), mean nuclear perimeter (MNP), mean nuclear form factor (FF; nuclear perimeter²/4π nuclear area) and their respective SDs were assessed by image analysis of both hematoxylin and eosin-stained histologic sections and May-Grünwald-Giemsa-stained cytologic smears from the same case in 20 spontaneous canine tumors of different histogenesis. The above parameters were selected as being the best morphometric tools for measuring variation in shape and size in cells after neoplastic transformation. Data were compared by ANOVA with P<.01 considered significant.
Results — There was a significant difference between histologic and cytologic specimens for MNA, MNP, and their SDs. Only the differences between FF and the SD of FF were not statistically significant.
Conclusions — Only nuclear morphometric data related to nuclear shape and nuclear shape variability are comparable between histologic and cytologic specimens. Nuclear area and perimeter may be affected by the different fixation and smear preparation techniques used in histology and cytology.     

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.