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Objective To compare the stiffness, angular deformation, and mode of failure of lumbar vertebral column constructs stabilized with bilateral pins and polymethylmethacrylate (Pin-PMMA) or with a unilateral (left) locking compression plate (LCP) with monocortical screws. Study Design Ex vivo biomechanical, non-randomized. Samples: Cadaveric canine thoracolumbar specimens (n=16). Methods Thoracolumbar (T13-L3) vertebral specimens had the L1-L2 vertebral motion unit stabilized with either Pin-PMMA or LCP. Stiffness in flexion, extension, and right and left lateral bending after nondestructive testing were compared between intact (pretreated) specimens and Pin-PMMA, and LCP constructs. The Pin-PMMA and LCP constructs were then tested to failure in flexion and left lateral bending. Results Both the Pin-PMMA and LCP constructs had reduced range of motion at the stabilized L1-L2 vertebral motion unit compared to intact specimens. The Pin-PMMA constructs had less range of motion for the flexion elastic zone than LCP constructs. The Pin-PMMA constructs were stiffer than intact specimens in flexion, extension, and lateral bending, and stiffer than LCP constructs in flexion and left lateral bending. The Pin-PMMA constructs had less angular deformation at construct yield and lower residual deformation at L1-L2 than LCP constructs after destructive testing to failure in flexion. The Pin-PMMA constructs were stiffer, stronger, and had less deformation at yield than LCP constructs after destructive testing to failure in lateral bending. Most constructs failed distant to the implant and fixation site. Conclusions Pin-PMMA constructs had greater lumbar vertebral stiffness and reduced ROM than LCP constructs; however, both Pin-PMMA and LCP constructs were stronger than intact specimens.

Objective To use micro-computed tomography (CT) to evaluate the fissure–fracture pattern in dogs affected by medial coronoid disease (MCD). Study Design Prospective case-controlled study. Sample Population Client owned (n = 21) and cadaver dogs (n = 5). Methods Segments were excised by subtotal coronoid ostectomy from dogs with MCD. Two categories were identified: fissured (Fi) or fractured (F). Three subcategories were contingent on fissure–fracture orientation: tip (T), radial incisure (RI), and radial incisure encroaching tip (RIT). Control segments were from nondiseased cadavers. High-resolution micro-CT (3 dimensional and 2 dimensional) was performed on all segments. Measurements included mean bone mineral density, trabecular number and thickness, and the angle of the fissure–fracture relative to the predominant trabecular orientation. Results A total of 28 diseased segments from 21 dogs (mean age 23.3 months, mean bodyweight 31.5 kg) were analyzed and categorized according to fissure–fragment location as Fi-T (n = 2), Fi-RIT (n = 2), Fi-RI (n = 3), F-T (n = 5), F-RIT (n = 9), F-RI (n = 7). The 3D analysis revealed subchondral micro-fracturing occurred in association with fragmentation. Canalicular impaction was associated with increase in trabecular number and decrease in trabecular space, most notably in RI categories. The 2D analysis showed that predominant trabecular orientation in control segments was significantly different to RI but not to T. The mean (SD) angle difference between the orientation of fissure–fracture and the predominant trabecular pattern was 6.9 (6.9)° for RI and 44.6 (49.6) ° for T. Conclusion T and RI fissure–fracture patterns show morphologic differences and likely arise from different supraphysiologic loading. Medial compartment disease is not homogenous and pattern recognition may assist further investigation of etiopathogenesis.

Objective To evaluate frequency, severity, and location of patellofemoral (PF) osteoarthritis (OA) in dogs with naturally occurring cranial cruciate ligament (CCL) disease. Study Design Cross-sectional observational study. Animals Dogs (n = 40; stifles, 44). Methods Stifle arthroscopic video recordings and radiographs were performed. Cartilage pathology was scored at 3 locations (proximal, middle, distal) in the trochlear groove and patella. A radiographic osteoarthrosis and synovial pathology score were assigned. A Kruskal–Wallis test was used to determine if lesion severity varied by site, synovitis, and osteoarthrosis, and the Dunn's test was used for pairwise comparisons. The variability of body weight was evaluated using 1 way ANOVA; P

Objective To develop a surgical technique to elevate the medial trochlear ridge for surgical correction of medial patellar luxation, and to evaluate clinical outcome. Study Design Case series. Animals Dogs (n = 5) with Grade 3 medial patellar luxation. Methods An asymmetrical wedge was removed from the trochlear groove, rotated 180°, and placed in the recess to create an elevated medial trochlear ridge. Postoperative radiography, CT scan, and subjective evaluation of clinical outcomes were performed. Results Surgical procedure and postoperative recovery were uncomplicated. There was no recurrence of spontaneous luxation and subjectively, gait improved in all dogs. Postoperative radiographs and CT images confirmed the elevated medial trochlear ridge, a significantly increased groove depth/patellar thickness ratio (P

Objective To compare (1) proximal femoral axial strains, (2) femoral head deflection, and (3) failure mechanical properties, between Helica head and neck prosthesis implanted femora and normal femora. Study Design In vitro study. Sample Population Cadaveric canine femora (n = 5 pair). Methods Femoral bone strains and head displacement during in vitro simulation of midstance of the gallop were evaluated using cadaveric femurs cyclically loaded in vitro. Strains and displacements were compared within femurs, before and after, prosthesis implantation; and throughout cycling to seek evidence of movement with cyclic loading. Subsequently, implanted femurs and contralateral, intact femurs were loaded to failure to compare failure mechanical properties and modes of failure. Results Proximal femoral axial strains were significantly different between intact and implanted femora on all 4 cortical surfaces (P .05). Vertical head displacement was ∼0.1 mm greater for implanted femora than intact femora (P < .05). Yield and failure loads and yield energy of implanted femora were 39–54% lower than those for intact femora (P < .05). Mode of failure for both the intact and implanted femora did not appear to be different. Conclusion Helica femoral prosthesis alters strain distribution in the proximal aspect of the femur and exhibits initial micromotion. Failure load in axial compression of the Helica-implanted femur is less than that of the normal femur, but greater than that expected in vivo.

Objectives: To (1) describe vascular distribution in the grossly intact canine cranial cruciate ligament (CCL) using immunohistochemical techniques specific to 2 components of blood vessels (factor VIII for endothelial cells, laminin for basement membrane); and (2) compare the vascularity in different areas of interest (craniomedial versus caudolateral bands; core versus epiligamentous regions; and proximal versus middle versus distal portions) in the intact normal canine CCL. Study Design: In vitro study. Animals: Large, mature dogs (n=7) of breeds prone to CCL disease that were euthanatized for nonorthopedic conditions. Methods: Intact CCL were collected from fresh canine cadavers free from stifle pathology. CCL tissue was processed for immunohistochemistry and stained for factor VIII and laminin. Vascular density was determined by histomorphometric analysis. Results: Specific vascular staining was sparsely identified throughout the CCL; however, the proximal portion of the CCL appears to have a greater number of vessels than the middle or distal portion of the ligament. Conclusions: The CCL is a hypovascular tissue and its vascular distribution is not homogeneous.

Objective: To (1) determine the microanatomic vascular distribution in ruptured canine cranial cruciate ligaments (CCL) using specific vascular immunohistochemical techniques, and (2) compare vessel density between ruptured and intact canine CCL and between different areas of interest in ruptured CCL using histomorphometric analysis. Study Design: In vitro study. Animals: Dogs (n=41) admitted for surgical treatment of ruptured CCL and 19 dogs euthanatized for nonorthopedic conditions. Methods: Diseased (variable CCL rupture) and intact (normal control) CCL were processed for immunohistochemical staining specific to vessels (factor VIII, laminin). Mean vascular density was assessed and compared in areas of interest (torn end versus remaining core regions of CCL, proximal femoral versus distal tibial core CCL regions). Results: Ruptured CCL was more vascular than intact CCL; however there was no difference in vascular density between the torn end and the remaining core area of the ruptured CCL. Ruptured CCL was vascularized to a greater degree at the proximal portion than the distal portion of the CCL. Partially ruptured CCLs had a higher vessel density than completely ruptured CCLs. Conclusions: Vascular density is increased in diseased CCL compared with intact CCL. It remains to be determined whether this finding is associated with the cause of CCL rupture or is a result of CCL degeneration and rupture.

Objective: To evaluate the use of a locking compression plate (LCP) with monocortical screw purchase for stabilization of the canine cervical spine. Study Design: Experimental study. Animals: Cadaveric canine cervical spine specimens (n=7). Methods: Flexion and extension bending moments were applied to canine cadaveric specimens (C3–C6) in 4-point bending, before and after creation of a ventral slot at C4–C5, and after fixation with a 5 hole, 3.5 mm LCP with monocortical screw placement. Screw placement and penetration into the vertebral canal were determined by radiography. Range of motion, stiffness, and energy for passive physiologic loads were determined for the C3–C4, C4–C5, and C5–C6 vertebral motion units (VMU). Monotonic failure properties were determined for cervical extension. Effects of treatments on biomechanical variables were assessed using repeated measures analysis of variance and least square means (P≤.05). Results: The ventral slot procedure increased range of motion at the treated VMU. Plate fixation decreased range of motion, increased stiffness, and decreased energy at the treated VMU. No changes were observed at adjacent VMUs. None of the screws penetrated the vertebral canal. Mean (± SD) yield bending moment of plate stabilized, slotted spines was 15.6 ± 4.6 N m. Conclusion: LCP fixation with monocortical screws stabilized the canine cervical spine.

Outcome, and Complications For Clinical Orthopedic Studies in Veterinary Medicine James L. Cook, DVM, PhD, Diplomate ACVS, Richard Evans, PhD, Michael G. Conzemius, DVM, PhD, Diplomate ACVS, B. Duncan X. Lascelles, BVSc, PhD, Diplomate ECVS, Diplomate ACVS, C. Wayne McIlwraith, BVSc, PhD, Diplomate ACVS, Antonio Pozzi, DMV, MS, Diplomate ACVS, Peter Clegg, MA, VetMB, PhD, Diplomate ECVS, MRCVS, John Innes, BVSc, PhD, DSAS (Orth), MRCVS, Kurt Schulz, DVM, Diplomate ACVS, John Houlton, MA, VetMB, DVR, DSAO, MRCVS, Diplomate ECVS, Lisa Fortier, DVM, PhD, Diplomate ACVS, Alan R. Cross, DVM, Diplomate ACVS, Kei Hayashi, DVM, PhD, Diplomate ACVS, Amy Kapatkin, DVM, MS, Diplomate ACVS, Dorothy Cimino Brown, DVM, MSCE, Diplomate ACVS, and Allison Stewart, DVM, MS, Diplomate ACVS Comparative Orthopaedic Laboratory, University of Missouri, Columbia, MO, College of Veterinary Medicine, University of Illinois, Urbana, IL, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, Comparative Pain Research Laboratory, North Carolina State University

Objective: To report biomechanical properties of the Biologic Fixation System (BFX) acetabular cup impacted into a normal canine pelvis and to compare the effect of implant positioned to and beyond the medial acetabular wall. Study Design: In vitro cadaveric study. Animals: Hemipelves of mature, large-breed dogs (n=6). Methods: For each dog, 1 hemipelvis was reamed to the depth of the acetabular wall (group A) and 1 was reamed an additional 6 mm after penetration of the medial cortex of the acetabulum (group B). The hemipelves were implanted with acetabular cups and loaded in compression through a matching femoral prosthetic component until failure. Specimen stiffness, and failure displacement, load, and energy were determined from load and displacement data and results between groups compared with a paired t-test. Results: Mean failure load was greater in group A (3812 ± 391 N) than group B (2924 ± 316 N; P .05) were observed between groups. Bone fracture (n=5) and cup displacement (1) occurred in group A whereas in group B there were 3 fractures and 3 cup displacements. Conclusions: Although medial placement of the BFX cup affected compressive failure loads, failure loads for both groups exceeded normal physiologic loads. Clinical Relevance: Medial positioning of the acetabular cup does not appear to compromise acetabular implant-pelvic stability under normal physiologic loads. Because arthroplasty candidates often have abnormal acetabular architecture, mechanical properties of the cup placed in acetabula without a dorsal rim should be investigated.

Objective: To report clinical application of a tibial plateau leveling and medial opening crescentic osteotomy (TPLMOCO) by a single blade cut to ameliorate lameness in dogs with cranial cruciate ligament (CCL) rupture (CCLR) and concurrent tibia vara. Study Design: Case series. Animals: Bullmastiff-type dogs (n=4; 5 stifles). Methods: Dogs were evaluated clinically and radiographically and records retrospectively reviewed. Pins were driven through both cortices of the proximal and distal tibia and a multidirectional jig attached medially. Tibial plateau leveling osteotomy was performed with torsional realignment of the calcaneo-patellar axis. A rigid connecting bar applied to the pins laterally before distraction of the medial jig allowed medial opening of the osteotomy while maintaining contact on the lateral aspect of the osteotomy. A 3.5 mm plate was applied. Results: Meniscal and articular cartilage pathology was identified in the medial joint compartment in 4 stifles, and in both medial and lateral compartments in 1 stifle. Postoperatively, subjectively assessed lameness resolved in 4/5 limbs and improved in 1 limb. All osteotomies healed uneventfully, with superficial wound infection being the only complication in 1 dog. Conclusions: TPLMOCO is a potential treatment methodology for dogs with CCLR and tibia vara with or without tibial torsion. Clinical lameness was successfully ameliorated. Intraoperative assessment and correction of sagittal and rotational malalignment was sufficient to achieve satisfactory clinical outcome in these 4 dogs. Clinical Relevance: TPLMOCO offers a potential treatment option and warrants further investigation for use in selected cases.

Objective— To determine the clinical value of a novel osteoarthritis (OA) biomarker in detecting canine cruciate disease. Study Design— Cross sectional clinical study. Animals— Dogs (n=22) with cranial cruciate ligament (CCL) rupture and 12 control dogs. Methods— Concentrations of collagenase-generated cleavage epitope of type II collagen (Col2-3/4Clong mono, or C2C) in serum, urine, and joint fluid were compared between a group of dogs with CCL rupture and a control group. Correlation of C2C concentrations to the clinical stage of stifle OA was also evaluated. Results— There were no significant differences in C2C concentrations in serum, urine, and joint fluid between groups (P>.05). Subjective scores of lameness, joint effusion, osteophytosis were significantly more severe in the CCL rupture group compared with the control group (P .05). Conclusion— This OA biomarker did not detect pathology associated with CCL rupture. Our results suggest that collagenase-specific degradation of type II collagen in articular cartilage may not be involved in the early stage of naturally occurring canine cruciate disease, and that pathology associated with naturally occurring CCL rupture is different from that of experimental OA model. Clinical Relevance— C2C is not clinically useful in detecting CCL rupture in dogs.

Objective— To report use of combined cisterna chyli ablation (CCA) and thoracic duct ligation (TDL) for treatment of spontaneously occurring chylothorax in dogs. Study Design— Retrospective study. Animals— Eight dogs with chylothorax. Methods— TDL was performed through a right caudal intercostal thoracotomy and CCA through a left flank paracostal approach or ventral median celiotomy. Long-term outcome (range, 2–48 months; median, 11.5 months) was evaluated by telephone communication with owners. Results— Seven dogs were free of clinical signs related to chylothorax at last follow-up (range, 4–48 months; median, 15.5 months). One dog was euthanatized 2 months after surgery because of lack of improvement. No major complications occurred from CCA. Conclusion— CCA and TDL resolved chylothorax in most dogs (88%). Clinical Relevance— CCA combined with TDL may improve the outcome of chylothorax in dogs.

Objectives— To determine changes to the cells and collagenous and amorphous extracellular matrix (ECM) structure in ruptured canine cranial cruciate ligaments (CCL). Study Design— Prospective clinical study. Animals— CCL specimens obtained from 29 dogs with ruptured CCL and 6 young dogs with intact CCL. Methods— Ligament fibroblast number density and phenotype were determined in the core and epiligamentous regions. ECM birefringence and crimp structure in the core region were also studied. Results— Loss of fibroblasts from the core region of ruptured CCL was seen (P < .001), whereas, in the epiligamentous region, cell number densities were similar in ruptured and intact CCL (P= .7). In ruptured CCL, numbers of typical ligament fibroblasts (fusiform and ovoid cells) were decreased, and numbers of cells exhibiting chondroid transformation (spheroid cells) were increased in the core region (P < .001). Expansion of the volume of the epiligamentous region was also seen, although bridging scar tissue was not seen between the ends of ruptured CCL. The structure of the ECM collagen in the core region was extensively disrupted in ruptured CCL. This was, in part, because of decreased birefringence and elongation of the crimp in the remaining collagen fibers when compared with intact CCL (P < .01). Conclusions— Extensive alterations to the cell populations and collagenous ECM structure were seen in ruptured CCL. Although a proliferative epiligamentous repair response was seen in ruptured CCL, there was a lack of any bridging scar between the ruptured ends of the CCL. Clinical Relevance— The cellular and ECM changes in ruptured CCL that we have described appear to result from the cumulative effects of remodeling and adaptation to mechanical loading and microinjury. Treatment of early cruciate disease in dogs will need to inhibit or reverse these progressive changes to CCL tissue, which are directly associated with partial or complete structural failure of the CCL under conditions of normal activity.

Objective— To evaluate the mechanical properties of 5 types of fishing material, 2 sterilization methods, and a commercially designed crimp-clamp system for the extra-articular repair of the canine stifle joint. Study Design— Experimental study. Sample Population— Animals were not used in this study. Methods— Two brands of monofilament nylon fishing line and 3 brands of monofilament nylon leader line were used to determine the effect of steam and ethylene oxide sterilization on strength and elongation of the material. A strand of 36-kg test monofilament nylon fishing material was wrapped around 2 rods or knotted to form a loop around 2 rods on a materials-testing machine. Ten trials of each brand of unsterilized, steam-sterilized, and ethylene oxide–sterilized fishing material were tested. A strand of each material was elongated to failure at a constant displacement of 1,000 mm/min to determine strength. A strand of each material was cycled 10 times to a load of 50 N to determine percent elongation. The brand of fishing material with the greatest strength and least elongation was crimped to form a loop around 2 rods on a materials-testing machine and tested as described above. ANOVA was used to determine the effect of sterilization method, brand of material, knot, wrap, and crimp on strength and elongation of the material, and a post-hoc t test was used when significant differences were found. A Student t test was used to compare fixation techniques (wrap, knot, and crimp). Results— Sterilization by steam or ethylene oxide had no significant effect on the strength of the nylon fishing material. Steam sterilization resulted in significant increases (2- to 4-fold) in elongation of most nylon fishing material when compared with unsterilized material. Ethylene oxide sterilization had minimal effect on elongation of the fishing material. Mason leader line showed no significant change in strength or elongation regardless of sterilization method. Significantly less strength and significantly less elongation were demonstrated in Mason leader line that was crimped as compared with Mason leader line that was knotted. Conclusion— Ethlylene oxide was the preferred method of sterilization to preserve strength and minimize elongation of the fishing material. Of the materials tested, Mason leader line had the least elongation and the greatest preservation of strength when ethylene oxide was used as the sterilization method. Mason leader line and Sufix fishing line were comparable choices when steam was used as the sterilization method. Significantly less elongation was demonstrated in crimped Mason leader line as compared with knotted Mason leader line. Clinical Relevance— Of the materials tested, Mason leader line and Sufix fishing line had the best mechanical properties for extracapsular stabilization of the canine stifle joint. Crimping is an attractive alternative to knotting and results in a reduction in elongation of the nylon fishing material.

Objective To determine presence of bacterial DNA in canine stifles with cranial cruciate ligament rupture (CCLR) and medial patellar luxation (MPL) compared to normal canine stifles (control). Study design Prospective clinical study. Animals Dogs (n = 44). Methods Dogs of varying age, breed, sex, and weight residing in California were assessed for stifle pathology (CCLR, MPL, or normal control). Synovial fluid of all stifles was assessed for the presence of bacterial DNA using broad-ranging 16S rRNA primers and PCR. Results Bacterial DNA was detected in normal control stifles and those with CCLR and MPL. There were no statistical differences in the copy numbers of bacterial DNA in the stifle synovial fluid among groups (P > .05); however, synovial fluid specimens from dogs with stifle pathology (CCLR and MPL combined) tended to have higher copy numbers of bacterial DNA than those from controls (P = .06). There was no significant difference in the number of bacterial DNA between the CCLR and MPL groups (P = .57). The copy numbers of bacterial DNA had a weak positive significant correlation with the duration of lameness in CCLR group (P

Objective To determine the effect of implant placement on proximal femoral axial bone strains, implant subsidence, implant motion, and failure mechanical properties of Helica implants. Study Design In vitro biomechanical study. Sample Population Cadaveric canine femora (n = 8 pairs). Methods Femora instrumented with strain gauges and kinematic markers were cyclically loaded in axial compression before (intact femora) and after implantation with a Helica prosthesis that engaged only cancellous bone (traditional technique) or cancellous bone and lateral cortex (modified technique) to evaluate bone strains, subsidence, and motion; femora were then loaded to failure to evaluate failure mechanical properties. Results After implantation, modified femoral prosthesis angle was 5% less than intact femora and 5.7% less than traditional implanted femora. Medial femoral bone strain was lower (P ≤ .05) for intact (−570 µstrain) than modified (−790), but not (P = .08) traditional (−700) implanted femora. High-load implant subsidence was present but small (−0.087 mm) for the modified technique. Motion (traditional and modified) increased (P = .05) during cyclic loading (−0.17 and −0.328 mm) and failure (P = .04) (−2.121 and −3.390 mm); remaining yield and failure properties revealed no significant findings (P ≤ .05). Conclusions The modified technique resulted in a smaller neck angle and minimal subsidence. Bone strain was minimally altered so stress shielding may be less compared to findings with traditional implants. Motion detected during cyclic and failure testing may lead to implant loosening in vivo.