Statistical shape modeling of the geometric morphology of the canine femur, tibia, and patella.

Bone morphometry varies among dogs of different sizes and breeds. Studying these differences may help understand the predisposition of certain breeds for specific orthopedic pathologies. This study aimed to develop a statistical shape model (SSM) of the femur, patella, and tibia of dogs without any clinical orthopeadic abnormalities to analyze and compare morphological variations based on body weight and breed. A total of 97 CT scans were collected from different facilities and divided based on breed and body weight. The 3D models of the bones were obtained and aligned to a coordinate system. The SSM was created using principal component analysis (PCA) to analyze shape variations. The study found that the first few modes of variation accounted for a significant percentage of the total variation, with size/scale being the most prominent factor. The results provide valuable insights into normal anatomical variations and can be used for future research in understanding pathological bone morphologies and developing 3D imaging algorithms in veterinary medicine.

Evaluation of anatomic landmarks to increase precision performing a mini-hemilaminectomy-an ex vivo study in dogs.

The mini-hemilaminectomy is a frequently used surgical technique for decompressive disk surgery on dogs. The aim of the study was to assess landmarks in the canine thoracolumbar spine to perform a mini-hemilaminectomy, with the aim of achieving optimal exposure of the ventral aspect of the vertebral canal. We hypothesized that the accessory process is a useful landmark for the identification of the level of the vertebral canal floor (VCF) and for decreasing surgical time. To define the level of the VCF, different landmarks and their distance to the VCF from computed tomography images of 40 mature chondrodystrophic dogs were evaluated in the first part of the study. To test the predefined landmarks, a cadaveric experiment was subsequently performed in the second part of the study. An experienced surgeon and a second-year surgical resident performed mini-hemilaminectomies as precisely as possible, with and without using the landmark values. Surgery time, precision of the mini-hemilaminectomy, and iatrogenic damage of the spinal nerve roots were compared between the two groups. Based on the results in the first part of the study, the distance from the dorsal border of the accessory process to the VCF (DBAP-VCF) was chosen as a landmark due to the good intra- (0.96) and interobserver (0.83) agreement. However, the distance is highly variable between breeds. In the second part of the study, using the DBAP-VCF landmark value did not influence the surgery time in both surgeons (p = 0.467, p > 0.99). An improved accuracy of the VCF was seen for the surgical resident with limited experience (p = 0.014), but not for the experienced surgeon (p = 0.926). For both surgeons, the spinal nerve roots were injured in 20% of the cases unrelated to the use of landmark values. In conclusion, this study suggests that the DBAP-VCF has been described as a breed-specific landmark that can be determined in CT with good agreement. Using the previously evaluated landmark values can help improve precision in decompressive spinal surgery for a surgeon with limited experience without prolonging surgical time.

Outcome and Complications following Stabilization of Coxofemoral Luxations in Cats Using a Modified Hip Toggle Stabilization-A Retrospective Multicentre Study.

OBJECTIVES: The main aim of this study was to report the surgical technique, the complications and the clinical outcomes of the mini-Tight Rope system (mini-TR) for a modified hip toggle stabilization of coxofemoral luxation in cats. STUDY DESIGN: A multicentre retrospective study. ANIMALS: Thirty-two client-owned cats. METHODS: Medical records (2009-2017) of cats, which underwent stabilization of a coxofemoral luxation with the mini-TR and had at least a 3-month follow-up, were reviewed. The femoral tunnel diameter, the use of one or two FiberWire loops, perioperative complications and clinical outcomes were recorded. Follow-up information was obtained through clinical and radiographic examinations and an owner questionnaire. RESULTS: Thirty-two cats met the inclusion criteria. Concurrent injuries were present in 16 cats. A single or double loop mini-TR was used in 21 and 12 cats respectively. One double loop (1/12 cats) and four single loop (4/16 cats) sutures failed. Moderate-to-severe coxofemoral osteoarthritis developed in 14/27 cats. Owner questionnaires revealed excellent clinical outcomes. CLINICAL SIGNIFICANCE: Mini-TR with a double-stranded implant is recommended to decrease the risk of suture failure. Osteoarthritis is common after open reduction of hip luxations.

Computed tomographic measurements of the femoral trochlea in dogs with and without medial patellar luxation.

OBJECTIVES: To determine cutoff values in small (SB) and medium/large (MLB) breed dogs with and without medial patellar luxation (MPL) for identifying abnormal femoral trochlea morphology. STUDY DESIGN: Original research. ANIMALS: A total of 80 computed tomographic (CT) scans from client-owned dogs METHODS: Four groups of 20 dogs were created: (1) control SB, (2) control MLB, (3) MPL-SB, and (4) MPL-MLB. Two authors measured the femoral trochlear groove angle (FTGA), femoral trochlear angle (FTA), and femoral trochlear ridge inclination angle (FTRIA) in two points with CT. ANOVA and ROC-analysis were tested to the control and MPL groups to assess sensitivity, specificity, and cutoff values. Statistical significance was set to p < .05. Intraclass correlation coefficients evaluated the inter-rater agreement. RESULTS: FTGA (± SD) in control SB (128.8° ± 4.7°) and control MLB (119.2° ± 5.6°), was smaller (p < .0001) than in MPL-SB (139.4° ± 4.4°) and MPL-MLB (133.7° ± 5.1°). FTA and FTRIA were decreased (p = .12, p = .23) in MPL-SB (2.1° ± 6.8; -0.3° ± 3.3°) and MPL-MLB (3.8° ± 5.6°; 1.7° ± 4.5°) compared to control SB (0.2° ±4.1; -0.1° ± 2.6°) and control MLB (5.3° ± 2.8°; 3.1° ± 1.3°). Cutoff values for FTGA, FTA, and FTRIA were > 134°, < -5.9°, < -2 ° (SB), and > 128.3°, < -0.4°, < -0.4° (MLB). Sensitivity, specificity, and inter-rater agreement were superior for FTGA than FTA and FTRIA. CONCLUSIONS: Dogs without MPL had a deeper femoral trochlear groove than MPL dogs. SB had a shallower groove than MLB. The measurement of FTA and FTRIA was not reliable. CLINICAL RELEVANCE: A FTGA <134° (SB) and < 128° (MLB) may be considered as a cutoff for trochleoplasty decision-making.

Three-dimensional volume rendering planning, surgical treatment, and clinical outcomes for femoral and tibial detorsional osteotomies in dogs.

OBJECTIVES: To describe a computed tomographic (CT) methodology for planning the correction of femoral and tibial torsion and report the clinical outcomes after femoral (FDO) and tibial (TDO) detorsional osteotomy in dogs affected by torsion malalignment and patellar luxation (PL). STUDY DESIGN: Multicenter retrospective study. ANIMALS: Eighteen client-owned dogs. METHODS: Dogs underwent CT to measure femoral (FTA) and tibial torsion angle (TTA). Abnormal femoral external torsion was defined when FTA <20°, abnormal femoral internal torsion if FTA >35°; abnormal tibial external torsion was defined when TTA < -10°, and abnormal tibial internal torsion when TTA >2°. The cortical arch length (CAL) was measured with CT and used intraoperatively to determine the magnitude of correction. The medical records and radiographs were reviewed and used to report clinical and radiographic outcomes. Radiographs were reviewed to evaluate postoperative limb alignment, patellar position, and bone healing. RESULTS: Twenty-two detorsional osteotomies were performed. Mean preoperative FTA was 14° for medial-PL and 45.2° for lateral-PL. Mean preoperative TTA was 11° for medial-PL. Physiological patellar tracking was restored in 22/22 of cases. CAL measurement allowed for correction of abnormal torsion in 19/22 of cases. Seventeen out 18 dogs had full or acceptable functional outcome. The median radiographic follow-up was 3 months. Major complications occurred in 2/22 cases, which suffered an iatrogenic abnormal femoral internal torsion and a persistent hindlimb lameness. CONCLUSIONS: CAL can be measured with CT and used intraoperatively to guide the correction of abnormal torsion in dogs. CLINICAL RELEVANCE: Abnormal femoral and tibial torsion are predisposing factors for PL. A higher complication rate is expected when FDO and TDO are performed in the same hindlimb.

Ex vivo comparison of lateral plate repairs of experimental oblique ilial fractures in cats.

OBJECTIVE: To determine the biomechanical behavior of different plate systems used for oblique ilial fracture fixation in cats. STUDY DESIGN: Ex vivo biomechanical study. SAMPLE POPULATION: Fifty fresh-frozen feline hemipelvises. METHODS: Standardized simple oblique ilial fractures were created and fixed via lateral plating, using different implant systems (10 fractures in each group) The systems were: (1) the Advanced Locking Plate System (ALPS-5); (2) the Advanced Locking Plate System (ALPS-6.5); (3) the Locking Compression Plate 2.0 (LCP); (4) the FIXIN 1.9-2.5 Series (FIXIN), and (5) the Dynamic Compression Plate 2.0 (DCP). Stepwise sinusoidal cyclic loading was applied until failure (10-mm displacement). The groups were compared with regard to construct stiffness and the number of cycles withstood before 1-, 2-, 5-, and 10-mm displacement. RESULTS: Bending stiffness was lower in ALPS-5 than in other specimens (P < .05). The ALPS-6.5 specimens withstood more cycles (P < .05) before 2-, 5-, and 10-mm displacement than the ALPS-5 and DCP specimens . The LCP and FIXIN specimens endured more cycles than DCP specimens before displaying 5- and 10-mm displacement (P < .05). The ALPS-6.5, FIXIN, and LCP specimens endured higher loads before failure than the DCP specimens (P < .05). Screw loosening occurred in all nonlocking specimens, and bone slicing occurred in all locking specimens. CONCLUSION: The DCP and ALPS-5 constructs are less resistant to cyclic loading. Failure in nonlocking specimens involved screw loosening. It involved bone slicing in locking specimens. CLINICAL SIGNIFICANCE: Both the plate size and the plate-screw interface are key to lateral plating success in cases of feline ilial fractures. The use of locking plates reduces the risk of the screw loosening in such cases.

Ex vivo study of the intradiskal pressure in the C6-7 intervertebral disk after experimental destabilization and distraction-fusion of the C5-C6 vertebrae in canine cadaveric specimens.

OBJECTIVE: To evaluate intradiskal pressure (IDP) in the C6-7 intervertebral disk (IVD) after destabilization and distraction-fusion of the C5-C6 vertebrae. SAMPLE: 7 cadaveric C4-T1 vertebral specimens with no evidence of IVD disease from large-breed dogs. PROCEDURES: Specimens were mounted in a custom-made 6 degrees of freedom spinal loading simulator so the C5-C6 and C6-C7 segments remained mobile. One specimen remained untreated and was used to assess the repeatability of the IDP measurement protocol. Six specimens underwent 3 sequential configurations (untreated, partial diskectomy of the C5-6 IVD, and distraction-fusion of the C5-C6 vertebrae). Each construct was biomechanically tested under neutral, flexion, extension, and right-lateral bending loads. The IDP was measured with a pressure transducer inserted into the C6-7 IVD and compared between the nucleus pulposus and annulus fibrosus and across all 3 constructs and 4 loads. RESULTS: Compared with untreated constructs, partial diskectomy and distraction-fusion of C5-C6 decreased the mean ± SD IDP in the C6-7 IVD by 1.3 ± 1.3% and 0.8 ± 1.3%, respectively. During motion, the IDP remained fairly constant in the annulus fibrosus and increased by 3.8 ± 3.0% in the nucleus pulposus. The increase in IDP within the nucleus pulposus was numerically greatest during flexion but did not differ significantly among loading conditions. CONCLUSIONS AND CLINICAL RELEVANCE: Distraction-fusion of C5-C6 did not significantly alter the IDP of healthy C6-7 IVDs. Effects of vertebral distraction-fusion on the IDP of adjacent IVDs with degenerative changes, such as those in dogs with caudal cervical spondylomyelopathy, warrant investigation.

Ex vivo Evaluation of the Dynamic Morphometry of the Caudal Cervical Intervertebral Disc Spaces of Small Dogs and Cats.

The objective of this study was to provide a morphometric description of the caudal cervical intervertebral disc (IVD) spaces of small-breed dogs and cats. Specimens consisting of C4 through C7 from five small-breed dogs and six cats were positioned in neutral, flexion, extension, and lateral bending positions; and CT images were acquired. Height and width of the cranial and caudal vertebral endplates (VEPs), angle between the VEPs (IVD wedge angle), and craniocaudal distance (IVD width) between VEPs for the four loading positions were measured and compared for three segments (C4-C5, C5-C6, and C6-C7). VEP size normalized to body weight from medium-sized dogs was retrieved from a previous study and compared with data from small dogs and cats. A linear mixed model was used to compare outcome measures. Significance was set to p < 0.05. VEP size normalized to body weight was the largest in small dogs compared with cats (p = 0.0422) and medium-sized dogs (p = 0.0064). Cats and medium-sized dogs were similar (p = 0.2763) in this regard. Flexion and extension induced a reduction of IVD width in the ventral portion of the IVD and the area of the nucleus. The dorsal part of the IVD remained unchanged throughout loading conditions. Unique morphometric characteristics of the caudal cervical IVD space of small dogs and cats were detected that are different from those described in sizes of dogs (medium-sized) typically affected by caudal cervical spondylomyelopathy (CSM). These findings may help to understand the different pathomechanisms in cervical spinal disease between small- and medium-sized dogs, including caudal CSM.

Biomechanical comparison of ex vivo lumbar vertebral fracture luxations stabilized with tension band or polymethylmethacrylate in cats.

OBJECTIVE: To evaluate spinal stabilization with tension band stabilization (TS) in cats compared to screw and polymethylmethacrylate fixation (SP). STUDY DESIGN: Ex vivo study. SAMPLE POPULATION: Sixteen feline thoracolumbar spinal specimens. METHODS: The intact specimens were mounted in a six-degree-of-freedom biaxial testing machine for nondestructive testing to obtain the neutral zones (NZ) and range of motion (ROM) in flexion and extension. Thereafter, nondestructive testing was consecutively performed after destabilization by disc fenestration and partial L1 corpectomy and after treatment with either TS or SP. Load to failure was compared after surgical treatment in flexion. Significance was assessed by Student's t test or Wilcoxon signed-rank test. RESULTS: Range of motion was 26.4° ± 2.2° in TS constructs and 13.4° ± 2.1° in SP constructs (P = .0005). When flexion and extension were analyzed separately, no difference was found for ROM in flexion (SP, 7.0° ± 3.7°; TS, 8.3° ± 2.1°; P = .38). In extension, the mean displacement was 6.4° ± 2.7° and 18.1° ± 5.1° in SP and TS constructs, respectively (P = .0001). Neutral zone was 2.9° ± 0.6° and 7.5° ± 0.8° for the SP and TS groups, respectively (P = .0003). Screw and polymethylmethacrylate fixation constructs were two times stiffer (P = .045). CONCLUSION: Tension band stabilization provided stability comparable to SP in flexion. In extension, ROM of SP constructs was half that of TS constructs. The mode of failure of TS was related to the limited dorsal bone stock of feline lumbar vertebrae. CLINICAL SIGNIFICANCE: Surgeons should be aware of the limited stability in extension provided by TS when it is used to stabilize thoracolumbar spinal injuries. Our results provide evidence to justify additional studies to clarify the type of fractures amenable to TS.

Influence of a customized three-dimensionally printed drill guide on the accuracy of pedicle screw placement in lumbosacral vertebrae: An ex vivo study.

OBJECTIVE: To compare the accuracy of pedicle screw insertion (PSI) into canine lumbosacral vertebrae with custom-made three-dimensionally (3D)-printed drill guides or freehand insertion. STUDY DESIGN: Ex vivo study. SAMPLE POPULATION: Nineteen canine lumbosacral specimens. METHODS: Drill guides for PSI were designed on the basis of safe screw insertion trajectories by using preoperative computed tomography (CT) and produced by 3D printing of templates. Right and left sides of the specimens were randomly allocated to two groups; 4-mm pedicle screws were inserted in L5-L6 and L7-S1 spinal segments either freehand (control group) or with custom-made drill guides (guide group). Sixty-six screws were inserted with each method. Insertion angles (α, ß), bone stock, and vertebral canal breach were assessed according to postoperative CT. χ2 Tests were used to compare vertebral canal breach between groups and vertebrae. RESULTS: Breaches in the vertebral canal were less common (P < .001) when screws were placed with a guide in the guide group (9/66, 14%) than without a guide (30/66, 45%). The rate of vertebral canal breach differed at L5 (P = .021) but not at L6 (P = .05), L7 (P = .075) or S1 (P = .658). The angle of insertion (α) did not differ between specimens with and without breaches (guide, P = .068; control, P = .394). CONCLUSION: The use of a customized 3D-printed guide generally improved the accuracy of PSI in canine lumbosacral vertebrae, although statistical significance was reached only at L5. CLINICAL SIGNIFICANCE: The use of customized drill guides may be considered as an alternative to freehand PSI in the lumbosacral area, especially for L5-L6 vertebrae.

Recommendations for rehabilitation after surgical treatment of cranial cruciate ligament disease in dogs: A 2017 survey of veterinary practitioners.

OBJECTIVE: To report current recommendations made by veterinarians for rehabilitation after surgical treatment of cranial cruciate ligament (CrCL) disease. STUDY DESIGN: Anonymized electronic survey. SAMPLE POPULATION: Veterinarians performing CrCL stabilization. METHODS: An electronic survey was created to collect information on general attitudes toward postoperative rehabilitation and recommendations regarding therapeutic modalities and bandaging. Quantitative data are reported by descriptive statistical analysis, percentage of responses, or mean (±SD). The recommendations for postoperative bandaging beyond 24 hours and for postoperative rehabilitation after extracapsular stabilization compared with after tibial osteotomy were tested by using Cochran-Mantel-Haenszel tests, with P < .05 considered statistically significant. RESULTS: The data analysis included 376 responses (13% response rate). Most (71%) respondents consistently recommended postoperative rehabilitation. Rehabilitation was more than twofold more likely to be recommended after extracapsular stabilization than after osteotomies (P = .0142). Most respondents did not recommend bandaging beyond 24 hours postoperatively (P = .00012). CONCLUSION: Most respondents recommended either formal or informal postoperative rehabilitation therapy. CLINICAL SIGNIFICANCE: If the survey respondents are representative of veterinarians performing CrCL surgery, the current attitude is supportive of postsurgical rehabilitation. Most respondents would welcome evidence-based guidelines for rehabilitation protocols.

Biomechanical comparison of knotted and knotless stabilization techniques of the tarsal medial collateral ligament in cats: A cadaveric study.

OBJECTIVE: To compare mechanical properties of intact feline medial collateral ligaments and three techniques for treatment of feline medial tarsal instability. STUDY DESIGN: Controlled laboratory study. SAMPLE POPULATION: Forty-eight normal, adult feline tarsi. METHODS: Three repairs were tested: a bone tunnel with polypropylene (PP) suture, a bone tunnel with polyethylene (PE) cord, and a knotless anchor technique with PE cord. A cyclic (6-N preload; 5-N amplitude; 2-Hz frequency) tensile test (600 cycles) was performed on feline tarsi with either the long or the short medial tarsal ligament intact, with each reconstruction technique followed by a single-cycle load-to-failure test (0.5 mm/s) with a failure point at 2 mm of displacement. Total elongation, peak-to-peak elongation, stiffness, and maximum load to failure point were compared with the intact condition. RESULTS: No differences in stiffness, total elongation, or peak-to-peak elongation were found between specimens repaired with the knotless technique and intact controls (P > .04), whereas tarsi repaired with the tunnel technique and PP were weaker (P < .008). Total and conditioning elongation were greater after tunnel reconstruction with PP than after knotless reconstruction (P = .005). Mean load to 2 mm of displacement tended (P = .03) to be higher after knotless than after knotted PP repairs and did not differ (P = .47) between tarsi repaired with the tunnel or anchor repairs with PE. CONCLUSION: The mechanical properties of intact tarsi were superior to those of tarsi repaired with tunnel techniques and PP but were similar to those of tarsi repaired with knotless techniques with PE. CLINICAL SIGNIFICANCE: Feline tarsal stabilization with the knotless technique for tarsal medial collateral ligament insufficiency may reduce the requirement for or duration of postoperative coaptation.

Case report - azygos vein drainage into the left atrium in a dog with cor triatriatum dexter and a patent foramen ovale.

A 2-year-old Airedale terrier was presented with exercise intolerance since birth and newly developed chylous pleural effusion. Imaging procedures including echocardiography, cardiac magnetic resonance imaging, computed tomography, and selective angiography revealed an aberrant connection of the azygos vein and the left atrium, a membrane in the right atrium consistent with cor triatriatum dexter, and a patent foramen ovale with right-to-left shunt. Balloon dilation of the membrane in the right atrium seemed to result in transient improvement of exercise tolerance compared with the previous 2 years. When chylothorax relapsed after three months, the dog was euthanized. Necropsy confirmed the azygos vein to left atrial connection, the patent foramen ovale, and the cor triatriatum dexter.

Safety and Accuracy of Minimally Invasive Long Bone Fracture Repair Using a 2.5-mm Interlocking Nail: A Cadaveric Feline Study.

OBJECTIVES: The Targon Vet System (TVS) is a 2.5-mm interlocking nail that can be applied minimally invasively. The purpose of this study was to test if the TVS could be safely applied percutaneously to different feline long bones without fluoroscopic guidance. METHODS: A gap fracture was created in 96 feline humeri, femora and tibiae (n = 32/group). Paired bones were randomly assigned to two treatment groups: (1) TVS inserted percutaneously with fluoroscopy and (2) TVS inserted percutaneously without fluoroscopy. Intraoperative evaluation (complications, procedure time, attempts), radiographs (pre-/postoperative alignment, length) and anatomical dissection (neurovascular injury, rotational alignment) were compared between treatment groups. RESULTS: The use of fluoroscopy did not lead to significant differences in any of the outcome measures. Intraoperative complications predominantly occurred in the distal humerus (12/32) and the proximal femur (7/32). In total, 20/96 complications occurred with no complications for the tibia. Neurovascular structures were only damaged at the medial side of the distal humerus (10/32). CLINICAL SIGNIFICANCE: We conclude that the TVS can be safely applied percutaneously to the tibia and with limitations to the femur in normal cadaveric cats without fluoroscopy. Despite the limitations of a cadaveric study, the high number of complications is leading us to consider the humerus not safe for the TVS. A learning curve has to be expected and technical recommendations should be respected to decrease complications.

Ex vivo computed tomography evaluation of loading position on morphometry of the caudal cervical intervertebral disk spaces of dogs.

OBJECTIVE To provide an objective, quantitative morphometric description of the caudal cervical intervertebral disk (IVD) spaces of dogs. SAMPLE Vertebral specimens consisting of C4 through C7 from 5 medium-sized dogs. PROCEDURES CT images were obtained with the specimens positioned in neutral, flexion, extension, and lateral bending positions. Size and shape of the cranial and caudal end plates, angle between the end plates (IVD wedge angle), and craniocaudal distance (IVD width) between end plates for the 4 loading positions were measured and compared for the 3 segments (C4-5, C5-6, and C6-7). RESULTS End plate size and shape, IVD wedge angle, and IVD width were not significantly different among the 3 segments. Caudal cervical end plates were consistently larger than cranial cervical end plates. The IVD wedge angle ranged from -4.8° to 15.2°. Flexion induced a reduction in IVD width in the ventral portion of the IVD, whereas extension induced a decrease in width in the dorsal portion of the IVD. Central IVD width remained unchanged among the loading positions. CONCLUSIONS AND CLINICAL RELEVANCE Unique morphometric and dynamic characteristics of the caudal cervical IVD space of dogs were detected. These findings may help investigators when designing IVD prostheses for dogs with cervical spondylomyelopathy.

Biomechanical properties of plate constructs for feline ilial fracture gap stabilization.

OBJECTIVE: To determine the biomechanical properties of plating techniques for comminuted feline ilial fractures. STUDY DESIGN: Ex vivo study on 40 paired feline hemipelves. SAMPLE POPULATION: Forty paired fresh-frozen hemipelves that had been collected from 20 cats aged 2-6 years and weighing 4.0-5.5 kg. METHODS: A transverse 3-mm gap was created in each ilium. Hemipelves were fixed with one of the following methods (n = 10 per group): (1) a dorsal plate and nonlocking screws, (2) a lateral plate and nonlocking screws, (3) a lateral plate and locking screws, or (4) a lateral and dorsal locking compression plate using nonlocking screws. Each specimen was subjected to incremental, sinusoidal cyclic loading until failure, defined as 10-mm displacement. The initial stiffness and number of cycles required to reach 1-, 2-, 5-, and 10-mm axial displacement were statistically analyzed. RESULTS: The initial stiffness and number of cycles to failure were higher in specimens fixed with double nonlocking plates than in all other fixations (P < .05) except specimens fixed with lateral locking plate at 10-mm displacement (P = .44). Locking implants withstood more cycles to 5- (P < .05) and 10-mm (P < .05) displacement compared with other single-plate nonlocking groups. Screw loosening occurred only in the 3 nonlocking fixations. CONCLUSION: Double plating improved stiffness and resistance to failure of comminuted feline ilial fracture constructs compared with all other fixations. Single locking plates produced superior constructs compared with single nonlocking constructs. CLINICAL SIGNIFICANCE: Locking implants are recommended to repair comminuted feline ilial fractures for their extended fatigue life and resistance to screw loosening. Orthogonal plating offers a strong nonlocking alternative.

An anatomical study of plate-rod fixation in feline tibiae.

OBJECTIVE: To investigate the feasibility of placing bi-cortical cortex (B-cort) or mono-cortical locking screws (M-lock) in a plate-rod construct applied to the feline tibia in combination with different intramedullary (IM) pins. METHODS: Twenty-four feline tibiae of cats were divided into 4 groups, corresponding to IM pin sizes filling approximately 30% (1.0 mm), 40% (1.4 mm), 45% (1.6 mm), and 50% (1.8 mm) of the medullary canal. Computed tomography (CT) was performed to trace potential screw trajectories in each group. A 12-hole, 2.4 mm locking compression plate was then applied on the medial aspect of the tibia. M-lock and B-cort screws were inserted subsequently in each plate hole. Success rates of screw insertion based on CT analysis and cadaveric simulation were compared with screw type, IM pin diameter, and anatomic location as variables. RESULTS: Screw insertion rates were underestimated on CT compared to cadaveric specimens. During cadaveric simulation, B-cort screws could be inserted in all specimens in the 3 most proximal plate holes and in at least 1 of the 3 distal plate holes. The smallest pin size (30%) allowed placement of a greater number of B-cort screws (P < .05) compared to other pins. Fewer B-cort screws could be inserted in the distal diaphyseal region (P < .05) compared to other regions. A total of 99.3% of M-lock screws could be inserted regardless of IMP size. CLINICAL SIGNIFICANCE: Plate rod constructs can include bicortical screws in the proximal and distal metaphysis, and monocortical screws in the diaphysis, combined with an IM pin filling up to 50% of the medullary canal.

Screw Loosening and Pelvic Canal Narrowing After Lateral Plating of Feline Ilial Fractures With Locking and Nonlocking Plates.

OBJECTIVE: To compare the frequency of complications, including screw loosening and pelvic canal narrowing, associated with dynamic compression plating, locking plating, and double locking plating of ilial fractures in cats. STUDY DESIGN: Historical cohort study. METHODS: The radiographs and medical records of cats with pelvic fractures that were presented between 2004 and 2013 were reviewed. The cases were categorized based on the plate type and number as dynamic compression plate (DCP), single locking plate (LPS) and double locking plates (dLPS). The frequency of screw loosening was compared across categories using a Fisher's exact test. The change in pelvic alignment, described by the change in sacral index (postoperative sacral index-followup sacral index), was compared across plate categories using ANOVA. RESULTS: The frequency of screw loosening for DCP (5/10) was significantly higher than LPS (1/13) and dLPS (0/11) (P = .05, P = .012, respectively). There was no significant difference in the SI change across plate categories. The mean change in sacral index for DCP was -0.11 (95%CI -0.25 to 0.03), for LPS was 0.0007 (95%CI -0.07 to 0.08), and for dLPS was -0.01 (95%CI -0.04 to 0.02). None of the cats showed constipation postoperatively. CONCLUSION: Screw loosening occurred less often but the change in pelvic canal alignment was not significantly different in ilial fractures repaired with LPS or dLPS compared to ilial fractures repaired with DCP. Locking plating of ilial fractures in cats may offer advantages compared to nonlocking plating.

Chronic expanding haematoma in a cat.

A 5-year-old cat developed a recurrent haematoma in the right hindlimb after receiving an intramuscular injection. Cold packs and a compressive bandage were applied without success. The haematoma resolved initially but recurred twice within a week after conservative treatment. Contrast computed tomography was performed after the second recurrence. A large cavernous lesion was found craniolateral to the right stifle. The lesion was removed surgically. No recurrence occurred during a 5 month follow-up. On histopathology the lesion was characterised as a chronic expansive haematoma. To our knowledge, this type of lesion has not previously been described in a small animal.

Novel avulsion pattern of the left principal bronchus with involvement of the carina and caudal thoracic trachea in a cat.

A 2-year-old, 4.5 kg, neutered male domestic shorthair cat was presented to the emergency service with dyspnoea, anorexia and apathetic behaviour. Thoracic radiographs showed typical signs for a thoracic trauma and a tracheal lesion in the region of the carina, consistent with pseudoairway formation. Computed tomography (CT) was performed in the conscious cat to avoid aggravation of air leakage associated with ventilation. The additional CT findings were consistent with a novel pattern of a traumatic avulsion of the left principal bronchus expanding into the carina and caudal thoracic trachea. Despite the complex avulsion pattern, successful treatment was achieved surgically by performing an end-to-end anastomosis via a fifth right intercostal lateral thoracotomy. The cat was ventilated with a feeding tube and jet ventilation throughout. The cat showed excellent recovery 6 months after surgery.