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Background: Spinal stabilization in dogs is challenging, and improper implant placement can result in significant morbidity. Objectives were to evaluate reliability of a ball-tipped probe for detection of breached versus non-breached pedicle drill tracts in a canine large breed cadaveric model. CT scans obtained from T6 to sacrum. Fifty-six pedicles (T7-L7) were randomized to have 1 of 5 modified Zdichavsky drill tracts (non-breached, partial/full medial breach, partial/full lateral breach). All tracts were created using 3D-printed guides. Each pedicle was probed separately by 2 investigators in randomized fashion on 2 occasions, 2 weeks apart. Post-probing CT grading of tracts was performed by one investigator, blinded to probing results. Specificity, sensitivity, positive (PPV) and negative (NPV) predictive values and times to assign grade were compared between surgeons., Results: CT identified 43 non-breached tracts, 7 medial and 5 lateral breaches. One tract was excluded because of guide misplacement. Specificity was 90.1%. PPV for detection of medial and lateral breaches was 80.0% and 57.1%. Sensitivity for medial (grade 2a/2b) and lateral (grade 3a/3b) breaches was 100.0% and 80.0%. NPV was 98.8%. Overall median time to assign grade with probe was 37.5-59.5 s. Both surgeons had very good intraobserver agreement (k,0.823 and 0.812). Interobserver agreement for round 1 was good (k,0.674) and good-to-very good for round 2 (k,0.800)., Conclusions: Use of a ball-tipped probe is associated with excellent specificity, excellent sensitivity to detect medial breaches, and good sensitivity to detect lateral breaches. This technique may be useful to confirm integrity of pedicle screw/pin tracts in dogs., Competing Interests: Declarations. Ethics approval: Ethical approval for the study was obtained from University College Dublin’s animal research ethics committee (AREC-E-23-07-Mullins). Consent to participate: Cadavers used in this study were euthanized for reasons unrelated to the study. They were donated with owner consent to the primary author’s institution for teaching and research purposes as part of a body donation programme. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Objective: To evaluate outcomes and complication rate of utilizing a string-of-pearls (SOP) plate augmented with adjunctive fixation in the repair of canine femur fractures., Methods: Records of canine patients with mid-diaphyseal femoral fractures repaired with the SOP plate and adjunctive fixation were reviewed. Information retrieved from medical records included signalment, patient weight, fracture configuration, repair technique, healing time, and complications based on perioperative radiographic follow-up to clinical union. Forty client-owned dogs met inclusion criteria for this study. Variables analyzed for association with major complications included body weight, fracture configuration, repair technique, and adjunctive fixation., Results: Major complications requiring surgical revision occurred in 8 of 40 fractures. Five cases experienced intramedullary pin migration and were successfully treated with sedated pin removal. The remaining 3 cases involved implant failure via screw shear breakage and required surgical revision of the fixation to achieve a successful outcome. On the basis of a calculated Bonferroni correction, no statistical significance of the tested variables was found in association with major complications; however, significance was limited due to the low statistical power of this study., Conclusions: The use of adjunctive fixation with the SOP locking plate system led to radiographic union without complication in most cases, and no instances of plate breakage were reported. However, implant complications secondary to the adjunctive fixation can occur., Clinical Relevance: Adjunctive fixation used with the SOP plate for repair of canine femur fractures has a high success rate, though pin migration as a complication persists.

Introduction: Surgical glove use may be associated with a decrease in tactile sensitivity, with thicker gloves or double-gloving techniques further altering sensation. This study evaluates digital tactile sensitivity by use of a Grating Orientation Task (GOT) with multiple sterile gloving techniques (no gloves, single standard gloving, double standard gloving, orthopedic gloves, and micro-thickness gloves)., Methods: Each participant performed the GOT at increasing grating widths until correctly noting orientation in ≥8 of 10 trials with multiple glove types or double-gloving technique. Glove order was randomly assigned and participants were blinded to the orientation and dome size., Results: All gloves except micro-thickness gloves showed increased threshold sensitivity values (i.e. worse fingertip sensitivity) when compared to control (micro:control, p = 0.105, others:control, p < 0.05). Single-layer gloves showed no significant difference in sensitivity when compared to orthopedic ( p = 0.06) or double-layer latex gloves ( p = 0.26)., Discussion: Standard latex gloves decreased fingertip sensitivity when evaluated with the GOT. Double-layer and orthopedic latex gloves do not decrease sensitivity when compared with single-layer gloving. Micro-thickness gloves may provide similar tactile sensitivity to no surgical glove., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Riegel, Zellner, Hedlund and Kraus.)

Objective: To evaluate the feasibility of endoscopic inspection of thoracolumbar and lumbar pedicle tracts in a canine large-breed model and its accuracy for the detection of breached versus nonbreached tracts., Animals: 2 greyhound cadavers., Methods: CT scans of 2 greyhound cadavers from the sixth thoracic vertebra to the sacrum were obtained. Fifty-six pedicles were randomized to have drill tracts with different modified Zdichavsky grades (nonbreached, partial/full medial breach, or partial/full lateral breach) using 3-D-printed guides. Endoscopy was performed on a single occasion from October 9 to 10, 2023, using a 1.9-mm 0-degree needle arthroscope in a randomized blinded fashion. The grading of drill tracts was performed on postoperative CT. Specificity, sensitivity, positive and negative predictive values, and time to assign endoscopic grade were investigated., Results: Postoperative CT confirmed 43 nonbreached tracts, 7 medial breaches (partial/full), and 5 lateral breaches (partial/full). One tract was excluded because of guide misplacement. Intraosseous endoscopy was successfully performed in the remaining 55 drill tracts. Sensitivity to detect medial and lateral breaches was 71.4% and 60.0%. Negative predictive value was 93.1%. Specificity was 94.2%. Positive predictive value for detection of medial and lateral breaches was 83.3% and 54.5%. Median (range) time to assign an endoscopic grade was 118 (30 to 486) seconds., Clinical Relevance: Intraosseous endoscopy of pedicle drill tracts may be a useful adjunct technique during pedicle screw/pin placement in dogs.

A 7-year-old, 7.5 kg, female spayed dachshund dog presented to a veterinary teaching hospital after being referred for lameness and the inability to urinate. The dog presented as weakly ambulatory paraparetic with intact pain perception. Computed tomographic (CT) imaging showed ventral bony lysis and periosteal proliferation of the L3 vertebra, consistent with a plasma cell tumor. A corpectomy of the L3 vertebra was performed and subsequently stabilized with autogenous cortico-cancellous iliac crest bone staves, autogenous cancellous bone, and bilaterally placed locking plates [String of Pearls (SOP ® ), Orthomed]. The dog recovered well, with no decrease in neurologic status overnight, and continued to improve until discharge. Upon a recheck exam at 4 weeks postoperatively, the dog appeared neurologically improved with only mild ambulatory proprioceptive ataxia of the hind limbs. This case demonstrates that the transposition of a non-vascularized iliac crest autogenous bone graft with stabilization via SOP ® plates and screws can be used in the management of dogs with vertebral plasma cell tumors and should be considered as a surgical option in similarly affected cases., Competing Interests: KK has a financial interest in the implant used in this case. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Yoder, MacRae, Snead and Kraus.)

Objective: To compare pin placement accuracy, intraoperative technique deviations, and duration of pin placement for pins placed by free-hand probing (FHP) or 3D-printed drill guide (3DPG) technique., Sample Population: Four greyhound cadavers., Methods: Computed tomography (CT) examinations from T6-sacrum were obtained for determination of optimal pin placement and 3DPG creation. Two 3.2/2.4-mm positive profile pins were inserted per vertebra, one left and one right from T7-L7 (FHP [n = 56]; 3DPG [n = 56]) by one surgeon and removed for repeat CT. Duration of pin placement and intraoperative deviations (unanticipated deviations from planned technique) were recorded. Pin tracts were graded by two blinded observers using modified Zdichavsky classification. Descriptive statistics were used., Results: A total of 54/56 pins placed with 3DPGs were assigned grade I (optimal placement) compared with 49/56 pins using the FHP technique. A total of 2/56 pins placed with 3DPGs and 3/56 pins using the FHP technique were assigned grade IIa (partial medial violation). A total of 4/56 pins placed using the FHP technique were assigned grade IIIa (partial lateral violation). No pins were assigned grade IIb (full medial violation). Intraoperative technique deviations occurred with 6/56 pins placed using the FHP technique and no pins with 3DPGs. Overall, pins were placed faster (mean ± SD 2.6 [1.3] vs. 4.5 [1.8] min) with 3DPGs., Conclusions: Both techniques were accurate for placement of spinal fixation pins. The 3DPG technique may decrease intraoperative deviations and duration of pin placement., Clinical Relevance: Both techniques allow accurate pin placement in the canine thoracolumbar spine. The FHP technique requires specific training and has learning curve, whereas 3DPG technique requires specific software and 3D printers., (© 2023 The Authors. Veterinary Surgery published by Wiley Periodicals LLC on behalf of American College of Veterinary Surgeons.)

Objective: The objective of this study was to evaluate the use of linear external skeletal fixation (ESF) applied using minimally invasive techniques in dogs and cats., Study Design: Retrospective study., Animals: Forty-nine dogs and 6 cats., Methods: Medical records of cases with nonarticular tibial fractures, repaired using linear ESF at a single academic institution between July 2010 and 2020, were reviewed. All records of cases that had nonarticular tibial fractures repaired using linear ESF were included. Information was collected regarding signalment, surgical procedures performed, perioperative care, radiographic evaluation, and postoperative complications., Results: Intraoperative imaging was used in 40/55 (72%) of cases. Tibal plateau angle (TPA), tibial mechanical medial proximal and distal tibial angles (mMPTA and mMDTA, respectively) were not affected by intraoperative imaging (P = .344, P = .687, P = .418). A total of 22 (40%) complications occurred. Of these, 18 were considered minor and 4 were considered major. Open fractures had more major complications than closed fractures (P = .019). All fractures reached radiographic union of the fracture. The mean ± SD time to external fixator removal was 71 ± 48 days., Conclusion: Linear ESF applied using minimally invasive techniques with or without intraoperative imaging was an effective treatment for nonarticular tibial fractures., Clinical Significance: Closed application of linear ESF should be considered as a minimally invasive option for stabilizing nonarticular tibial fractures., (© 2022 The Authors. Veterinary Surgery published by Wiley Periodicals LLC on behalf of American College of Veterinary Surgeons.)

Traction was used to diagnose instability of a T5-T6 traumatic luxation that was stabilized with locking plates in the laminae and dorsal pedicles. A two-year-old, 27 kg, female spayed golden retriever was presented to a veterinary teaching hospital after being referred for possible mandibular and spinal fractures after being hit by a car. The dog presented non-ambulatory paraparetic with intact pain perception. Computed tomographic (CT) imaging showed a fifth and sixth thoracic vertebral fracture/luxation, with and without manual traction. Surgical stabilization of the spine was performed with bilateral dorsally placed locking plates (String-of-Pearls, Orthomed, UK) in the laminae and dorsal aspects of the vertebral pedicles. The dog recovered well, and neurologic status improved significantly overnight and continued to improve up until discharge, which was 6 days postoperatively. Upon recheck exam at 8 weeks postoperatively, the dog appeared neurologically normal with no obvious surgical complications. This case demonstrates that diagnostic traction-the process of pulling, during imaging, on the dog's pelvis while the forelimbs are secured in extension-demonstrated instability of the spine which was not readily apparent on initial CT imaging. Additionally, the dorsal locking plate stabilization is a viable fixation option that provided acceptable stabilization of the mid-thoracic vertebrae., Competing Interests: KK has a financial interest in the implant used in this case. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Tammaro, Early, Bergman, Petrovsky and Kraus.)

Objective: Identify acceptable implant corridors in the normal canine thoracic vertebrae (T) from T1 to T9., Study Design: Retrospective study., Sample Population: Computed tomographic (CT) studies of normal canine thoracic spines (n = 39)., Methods: CT imaging studies of normal T1-T9 canine spines were evaluated by five independent observers. Each identified a proposed corridor, measured the width, length, and angle off mid-sagittal that the corridor occupied., Results: CT studies were from 39 dogs weighing 3.19-60 kg (mean 10.72, SD 9.9 kg). Vertebral corridors ranged in average width from 3.8 to 5.2 mm, the widest being located at T1. They ranged in average length from 13.3 to 17.5 mm, shortest being T1 and longest being T6. The angle of corridors varied the most between individual vertebrae at T1-T3. The average corridor angles were: T1 = 38°, T2 = 32°, T3 = 27°, T4 = 26°. T5-T9 angle ranged from 23° to 24°., Conclusion: The average dimensions of corridors measured in dogs weighing 3.1-60 kg were consistent with those of commercially available cortical screws and pins., Clinical Significance: Corridor trajectories identified in this population can be achieved from a dorsal approach between T5 and T9. A dorsal approach for implant placement would be challenging for T1-T4 due to the variability found in these vertebrae as well as regional anatomical constraints., (© 2021 The Authors. Veterinary Surgery published by Wiley Periodicals LLC on behalf of American College of Veterinary Surgeons.)

Objective: To determine the influence of suture patterns on resistance to gap formation after tendon plating STUDY DESIGN: Ex vivo study SAMPLE POPULATION: Suspensory ligament and superficial and deep digital flexor tendons harvested from 16 neonatal cadaver foal limbs., Methods: Each tendon/ligament from a given limb was randomly assigned to one of three treatment groups consisting of a 7-hole veterinary cuttable plate fixed with alternating simple interrupted, figure-8, or hybrid suture patterns. The constructs were distracted at a rate of 1.0 mm/s to failure, as determined by the formation of a 1 mm gap for initial failure and a 3 mm gap for ultimate failure. The mode of failure was also recorded., Results: Constructs prepared with hybrid and figure-8 patterns sustained over 2× higher (p < .01) forces before gap formation compared to those prepared with a simple interrupted pattern. No difference was identified between tendons whose plate was secured with hybrid or figure-8 suture patterns. Mode of failure between groups did not differ., Conclusion: The figure-8 and hybrid patterns described herein improved the resistance to gap formation of plated tendons compared to an alternating simple interrupted pattern described previously., Clinical Significance: Figure-8 and hybrid patterns should be considered over simple interrupted patterns to improve resistance to gap formation in horses undergoing tendon plating., (© 2021 The Authors. Veterinary Surgery published by Wiley Periodicals LLC on behalf of American College of Veterinary Surgeons.)

Objective: To determine radiation exposure to surgical personnel and to evaluate the accuracy of a modified percutaneous lag screw fixation technique for sacroiliac luxation (SIL) under fluoroscopic guidance in dogs., Study Design: Cadaveric experimental study., Sample Population: Seventeen beagle cadavers with iatrogenic SIL., Methods: Seventeen beagles with iatrogenic SIL underwent reduction and stabilization with 3.5-mm screws. Hypodermic needles (14 gauge) and fluoroscopy were used to orient two Kirschner wires for temporary stabilization and to guide drilling of glide and pilot holes using cannulated drill bits. Duration of surgery and radiation exposure were recorded. Postoperative computed tomographic evaluation of screw position and angulation was performed., Results: Average time for fixation was 15.85 minutes (range, 6.37-33.5). Cumulative radiation doses of 0.4 mrem for the dominant arm of the assistant and 0 mrem for the primary surgeon were recorded. The mean dorsoventral and craniocaudal screw angles were 0.68° ± 3.4° (range - 5.4° to 9.5°) and 1.9° ± 3.2° (range - 4.3° to 9.1°), respectively. Sixteen of the 17 dogs had 100% sacral screw purchase, with the remaining case achieving 93.4% purchase., Conclusion: Fluoroscopy-assisted percutaneous placement of 3.5-mm cortical screws in lag fashion performed with 14-gauge needles in conjunction with Kirschner wires and cannulated drill bits yielded repeatable accurate screw placement with low levels of ionizing radiation exposure to the surgical team., Clinical Significance: The described technique may be a viable method for minimally invasive osteosynthesis fixation of SIL with low levels of radiation exposure to the surgical team. These results provide evidence to support further evaluation of radiation exposure in clinical cases and can aid in study design and sample size determination., (© 2021 The Authors. Veterinary Surgery published by Wiley Periodicals LLC on behalf of American College of Veterinary Surgeons.)

A tunable stiffness bone rod was designed, optimized, and 3D printed to address the shortcomings of existing bone fixation devices, such as stress shielding and bone nonunion in the healing of fractured bones. Current bone plates/rods have constant and high stiffness. High initial stiffness prevents the micromotion of newly formed bone and results in poor bone healing. Our novel design framework provides surgeons with a ready-for-3D-printing, patient-specific design, optimized to have the desired force-displacement response with a stopping mechanism for preventing further deformation under higher-than-normal loads, such as falling. The computational framework is a design optimization based on the multi-objective genetic algorithm (GA) optimization with the FE simulation to quantify the objectives: tuning the varied stiffness while minimizing the maximum von Mises stress of the model to avoid plastic and permanent deformation of the bone rod. The computational framework for optimum design of tunable stiffness metamaterial presented in this paper is not specific for a tibia bone rod, and it can be used for any application where bilinear stiffness is desirable., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The objective of this case report was to describe successful surgical and post-operative management of a medial patellar luxation in a Vietnamese Potbellied Pig. A two-year old, castrated, Vietnamese Potbellied Pig presented to a veterinary teaching hospital for right pelvic limb lameness of 2 weeks duration. Upon physical examination a grade 3 patellar luxation was diagnosed on the right pelvic limb. Surgical repair included a trochlear wedge sulcoplasty, tibial tuberosity transposition, and lateral imbrication as described for canine patellar luxation. The pig was managed post-operatively with meloxicam and a physical therapy regimen of seven weeks duration. At recheck examination the pig was sound, no complications were observed, and the owners were satisfied with the outcome. As miniature companion pigs, such as Vietnamese Potbellied Pigs are currently increasing in popularity as pets, this case demonstrated that comparative techniques from other veterinary species should be considered when considering a treatment plan for a pig with a medial patellar luxation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Høy-Petersen, Smith, Merkatoris, Black, Faivre, Miles, Tatarniuk and Kraus.)

Objective: To determine the influence of plate fixation (locking or dynamic compression) and the site of application (ventral [V] or ventrolateral [VL]) on the resistance to bending of transverse mandibular fractures., Study Design: Ex vivo, simple randomized study., Sample Population: Mandibles harvested from adult equine cadavers (n = 18)., Methods: Bilateral osteotomies were created 1 cm caudal to the mental foramen and perpendicular to the long axis of each mandible. Mandibles were fixed with 1 of 3 methods: (1) VL dynamic compression plate (DCP), (2) V-DCP, or (3) VL locking compression plating (LCP). Constructs were mounted on a custom testing jig and tested for resistance in bending by applying force to the rostral aspect of the mandible. Stiffness and change of distance of the dorsal osteotomy at 200 N were compared among constructs., Results: VL-LCP constructs were 5.25 and 2.42 times stiffer than V and VL constructs, respectively (P<.001). Change in the width of the osteotomy gap at 200 N of load was reduced 6.04 times when osteotomies were stabilized with VL compared to V (P<.001); no difference was detected between the VL and VL-LCP constructs (P=.836)., Conclusion: Ventrolateral LCP fixation of equine transverse mandibular osteotomies provided greater resistance to bending compared with V and VL constructs., Clinical Significance: These results provide evidence to recommend fixation of transverse interdental mandibular fractures with VL-LCP rather than with DCP in horses., (© 2019 The American College of Veterinary Surgeons.)

Objective:  The aim of this study was to to determine the comparative stiffness following repair of an axial sagittal fracture model in equine distal sesamoid bones using either a single 3.5-mm or 4.5-mm cortical bone screw placed in lag fashion., Study Design:  The present study was an in vitro biomechanical study., Results:  The mean (±standard deviation) stiffness value for the 4.5-mm screw-bone construct (522.49 N/mm ± 168.21) was significantly greater than the 3.5-mm screw-bone construct (408.46 N/mm ± 131.13) ( p  = 0.047). This represents a 28% difference in mean stiffness., Conclusions:   In vitro , the 4.5-mm screw-bone construct creates a stiffer repair of fractured distal sesamoid bones by a margin of 28%. The 4.5-mm cortical bone screw may better withstand forces imparted on the distal sesamoid bone sustained during anaesthetic recovery, normal weight bearing and athletic exercise, thereby minimizing the risk of implant failure., Competing Interests: All authors have no conflicts of interest to disclose., (Georg Thieme Verlag KG Stuttgart · New York.)

Background: Suture materials and techniques are frequently evaluated in ex vivo studies by comparing tensile strengths. However, the direct measurement techniques to obtain the tensile forces in canine skin are not available, and, therefore, the conditions suture lines undergo is unknown. A soft elastomeric capacitor is used to monitor deformation in the skin over time by sensing strain. This sensor was applied to a sample of canine skin to evaluate its capacity to sense strain in the sample while loaded in a dynamic material testing machine. The measured strain of the sensor was compared with the strain measured by the dynamic testing machine. The sample of skin was evaluated with and without the sensor adhered., Results: In this study, the soft elastomeric capacitor was able to measure strain and a correlation was made to stress using a modified Kelvin-Voigt model for the canine skin sample. The sensor significantly increases the stiffness of canine skin when applied which required the derivation of mechanical models for interpretation of the results., Conclusions: Flexible sensors can be applied to canine skin to investigate the inherent biomechanical properties. These sensors need to be lightweight and highly elastic to avoid interference with the stress across a suture line. The sensor studied here serves as a prototype for future sensor development and has demonstrated that a lightweight highly elastic sensor is needed to decrease the effect on the sensor/skin construct. Further studies are required for biomechanical characterization of canine skin.

Objective: To report the application of a plate to treat a complicated calcaneal tendon rupture and the resulting outcome., Study Design: Clinical case report., Animals: A 3-year-old Labrador retriever., Methods: A 3-year-old Labrador retriever was treated for a partially ruptured calcaneal tendon. Two primary tendon repairs with sutures and external fixation had failed. A veterinary cuttable plate was placed to internally span the tendon over the primary repair. The external fixation that had been previously placed was maintained, and the dog was placed in a non-weight-bearing sling for 3 weeks after surgery. Adjunct therapy included an injection of platelet-rich plasma in the tendon and laser therapy. The external fixator was removed 4 weeks postoperatively, and the plate was removed 8 weeks postoperatively., Results: A mature fibrous union bridged the site of anastomosis 8 weeks after surgery. The owners reported normal activity 6 months after surgery and symmetric hock angles and musculature 2 years after surgery., Conclusion: Adjunct plating of previously failed calcaneal tendon repairs in a dog resulted in an excellent long-term outcome., Clinical Significance: Plating tendons can be considered as an additional method that may improve tendon apposition and decrease gap formation., (© 2018 The American College of Veterinary Surgeons.)

OBJECTIVE To compare suture placement time, tension at skin separation and suture line failure, and mode of failure among 4 suture patterns. DESIGN Randomized trial. SAMPLE 60 skin specimens from the pelvic limbs of 30 purpose-bred Beagles. PROCEDURES Skin specimens were harvested within 2 hours after euthanasia and tested within 6 hours after harvest. An 8-cm incision was made in each specimen and sutured with 1 of 4 randomly assigned suture patterns (simple interrupted, cruciate, intradermal, or subdermal). Suture placement time and percentage of skin apposition were evaluated. Specimens were mounted in a calibrated material testing machine and distracted until suture line failure. Tensile strength at skin-edge separation and suture-line failure and mode of failure were compared among the 4 patterns. RESULTS Mean suture placement time for the cruciate pattern was significantly less than that for other patterns. Percentage of skin apposition did not differ among the 4 patterns. Mean tensile strength at skin-edge separation and suture-line failure for the simple interrupted and cruciate patterns were significantly higher than those for the intradermal and subdermal patterns. Mean tensile strength at skin-edge separation and suture-line failure did not differ significantly between the intradermal and subdermal patterns or the simple interrupted and cruciate patterns. The primary mode of failure for the simple interrupted pattern was suture breakage, whereas that for the cruciate, intradermal, and subdermal patterns was tissue failure. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested external skin sutures may be preferred for closure of incisions under tension to reduce risk of dehiscence.

Objective: To investigate associations between recovery of locomotion and putative prognostic factors in dogs with loss of deep pain perception in the pelvic limbs caused by intervertebral disk herniation (IVDH)., Design: Prospective cohort study., Animals: 78 client-owned dogs evaluated for IVDH that underwent spinal decompression surgery., Procedures: Dogs with complete loss of deep pain perception in the pelvic limbs and tail underwent routine examinations, advanced imaging, and spinal decompression surgery in accordance with standards of practice and owner consent. For each dog, information was prospectively collected on duration of clinical signs prior to onset of paraplegia; delay between onset of paraplegia and initial referral evaluation; date of recovery of locomotion, death, or euthanasia (3-month follow-up period); and whether dogs had received corticosteroid drugs before surgery. Severity of spinal cord compression at the lesion epicenter was measured via CT or MRI., Results: 45 of 78 (58%) of dogs recovered the ability to ambulate independently within 3 months after spinal decompression surgery. No evidence of prognostic value was identified for any of the investigated factors; importantly, a greater delay between onset of paraplegia and referral evaluation was not associated with a poorer prognosis., Conclusions and Clinical Relevance: In this group of dogs with IVDH, immediacy of surgical treatment had no apparent association with outcome. The prognosis for recovery may instead be strongly influenced by the precise nature of the initiating injury.

Objective: To compare 2-0 polyglyconate barbed suture (V-LOC™ 180 Absorbable Wound Closure Device, Covidien, Mansfield, MA) to standard 2-0 monofilament absorbable polyglyconate suture (Maxon™, Covidien) for maximum load to failure and failure mode when used to appose standardized defects in canine diaphragm muscle., Study Design: Randomized, cadaveric ex vivo mechanical testing., Sample Population: Canine cadaveric hemi-diaphragmatic specimens (n = 32 pairs)., Methods: Thirty-two cadaveric diaphragm specimens were collected and divided to obtain 64 muscle specimens (9 cm × 4 cm). Paired specimens were bisected in the midpoint of their 9 cm length in the direction of the muscle fibers and apposed using either 2-0 polyglyconate or 2-0 barbed polyglyconate (V-LOC™ 180 Absorbable Wound Closure Device) in a simple continuous pattern. Increasing tension was applied perpendicular to the suture line until specimen failure. Failure mode and maximum load to failure were recorded for each specimen., Results: Mean ± SD failure load of simulated herniorrhaphies performed with barbed polyglyconate suture (54.5 ± 10.27 N) was not significantly different than repair with polyglyconate (56.9 ± 10.87 N). Failure mode for both construct types was suture tear out rather than suture failure., Conclusions: Clinical application of 2-0 barbed polyglyconate suture can be considered as an alternative to the use of 2-0 polyglyconate for diaphragmatic herniorrhaphy., (© Copyright 2014 by The American College of Veterinary Surgeons.)

Locking plates have been shown to offer improved fixation in fractures involving either osteoporotic bone or bone with lesser screw pullout strength, such as thin and flat bones. Fractures of the scapular body are one type of fracture where the screw pullout strength using conventional plate fixation may not be sufficient to overcome physiologic forces. The purpose of this study was to compare the pullout strengths of locking plates to conventional nonlocking plates in the canine scapula. A 2.7 mm string of pearls plate (SOP) and a 2.7 mm limited contact dynamic compression plate (LC-DCP) were applied with similar divergent screws to the supraspinatus fossa of the scapula. Forces perpendicular to the plates were applied and both the loads at failure and modes of failure were recorded. No differences were noted in loads at failure between the two plating systems. Although the modes of failure were not significantly different, the SOP constructs tended to fail more often by bone slicing and coring, whereas the LC-DCP constructs failed primarily by screw stripping. Neither of the plate systems used in this study demonstrated a distinct mechanical advantage. The application and limitations of locking plate systems in various clinical situations require further study.

Objective: To compare the holding strength of a conventional plate-screw construct with a locking plate-screw construct in the thin cortical bone of the canine mandibular ramus., Study Design: Mechanical study., Animals: Paired cadaveric canine mandibles (n = 10 pairs)., Methods: Perpendicular pull-out testing was performed on 2.0-mm limited-contact dynamic compression plate (LC-DCP)-screw constructs and 2.0-mm string-of-pearls (SOP) plate-screw constructs applied to the ramus of the canine mandible. Pull-out force was applied perpendicular to the long axis of the plates. Construct stiffness and load at failure were determined from load-displacement curves and method of failure was determined from high speed digital video recordings. A paired t-test was used to compare mean construct stiffness and load at failure between groups., Results: SOP plate-screw constructs had a significantly higher mean construct stiffness and load at failure than did LC-DCP-screw constructs. LC-DCP constructs failed by screw pull-out while bone slicing and fracture were prominent mechanisms of failure for SOP constructs., Conclusions: SOP plate-screw constructs sustained a significantly higher perpendicular load at failure than did LC-DCP-screw constructs., (© Copyright 2011 by The American College of Veterinary Surgeons.)

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 degrees and mean lateromedial insertion angle was 20 degrees., 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 degrees and an average lateromedial pin trajectory of 20 degrees., 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 degrees as guidelines for the craniocaudal and lateromedial pin insertion angles in the ilium.

A large body of preclinical and clinical data now documents that recombinant BMPs can be used for skeletal regeneration in humans and animals. Recombinant human BMP-2 and BMP-7 have been approved for use in human patients with long-bone fractures and nonunions and in patients undergoing lumbar fusion or various maxillofacial and dental regenerative procedures. These products have also been made available for veterinary use.

Objective: To determine if composite connecting rods confer nonlinear stiffness characteristics on unilateral and bilateral external skeletal fixators (ESF) in cranial-caudal bending and axial loading., Study Design: Mechanical testing performed on models., Sample Population: Six models of 6-pin ESF constructs composed of birch dowels, a commercial ESF system, and composite connecting rods., Methods: Unilateral and bilateral ESF configurations were assembled using either specially designed composite titanium and silicone (composite group) or solid titanium (solid group) connecting rods. Mechanical testing was performed in axial loading and 4-point cranial-caudal bending. Stiffness was determined at a low and high-load range, and was considered increasing and nonlinear if the stiffness at high loads was greater than at low loads., Results: The stiffness of the solid group was linear in all testing modes and configurations. Bilateral composite fixators had a nonlinear increasing stiffness in axial loading and cranial-caudal bending. Unilateral composite fixators had a nonlinear increasing stiffness in axial loading, but not cranial-caudal bending. Solid connecting rods conferred a higher stiffness in all testing modes and configurations., Conclusions: Composite connecting rods resulted in nonlinear increasing axial and bending stiffness in bilateral fixators, and in axial load in unilateral fixators., Clinical Relevance: Conventional ESF can be constructed so that the stiffness increases as load increases. This provides the surgeon with additional options to control the local mechanical environment of a healing fracture, which may be used to enhance fracture healing.

Using a canine critical-size segmental defect model, a two-phased study was undertaken to evaluate the healing efficacy of demineralized bone and cancellous chips (DBM-CC) enriched with osteoprogenitor cells using a Selective Cell Retention (SCR) technology. The goals of this study were: 1) to determine the bone-healing efficacy of SCR-enriched grafts versus autograft, and 2) to assess the value of clotting SCR-enriched grafts with platelet-rich plasma (PRP). Thirty dogs were included in Phase I: 18 dogs were treated with an SCR-enriched DBM-CC graft clotted with autologous bone marrow, and were compared to 12 autograft controls. In Phase II, 24 animals were divided into 4 groups of 6 animals, each treated with a different bone graft material: 1) iliac crest autograft, 2) DBM-CC alone, 3) DBM-CC saturated with marrow, and 4) SCR-enriched DBM-CC clotted with PRP. All grafts were placed unilaterally in a 21-mm long osteoperiosteal femoral, instrumented, critical-size defect. Radiographs were obtained for all animals postoperatively and every 4-16 weeks; animals were then sacrificed. All femurs were prepared for histology. Femurs in the Phase II study were also analyzed by micro-CT. At 16 weeks, healing--defined by bridging bone across the defects--was observed in 50% of the DBM-CC alone group and 67% of the DBM-CC saturated with marrow group; 100% of the autograft and SCR-enriched DBM-CC groups were healed. Histologically, grafts clotted with PRP showed more mature bone than those implanted with autologous bone, which in turn were similar to those implanted with bone marrow clotted SCR-enriched grafts. These results demonstrated that: 1) SCR-enriched DBM-CC was equivalent to autograft to repair critical-size defects, and 2) while not statistically significant, PRP may have accelerated bone maturation when used to clot osteoprogenitor-enriched DBM-CC grafts--as compared to cell-enriched, DBM-CC grafts without PRP--in large animal models., (Copyright 2006 Orthopaedic Research Society.)

Objective: To review the role of mesenchymal stem cells (MSC) in bone formation and regeneration, and outline the development of strategies that use MSC in bone healing and regeneration., Study Design: Literature review., Methods: Medline review, synopses of authors' published research., Results: The MSC is the basic cellular unit of embryologic bone formation. Secondary bone healing mimics bone formation with proliferation of MSC then their differentiation into components of fracture callus. Bone regeneration, where large amounts of bone must form, mimics bone healing and can be achieved with MSC combined with strategies of osteogenesis, osteoinduction, osteoconduction, and osteopromotion. MSC based strategies first employed isolated and culture expanded stem cells in an osteoconductive carrier to successfully regenerate a critical segmental defect in the femur of dogs, which was as effective as autogenous cancellous bone. Because MSC appeared to be immunologically privileged, a study using mismatched allogeneic stem cells demonstrated that these cells would regenerate bone without inciting an immunologic response, documenting the possibility of banked allogeneic MSC for bone regeneration. A technique was developed for selectively retaining MSC from large bone marrow aspirates at surgery for bone regeneration. These techniques utilized osteoconductive and osteoinductive carriers and resulted in bone regeneration that was similar to autogenous cancellous bone., Conclusion: MSC can be manipulated and combined with carriers that will result in bone regeneration of critically sized bone defects., Clinical Relevance: These techniques can be employed clinically to regenerate bone and serve as an alternative to autogenous cancellous bone.

Bilateral transverse mid-shaft tibial osteotomies, with a 4-mm gap, were performed in purpose-bred research dogs and stabilized using a Securos Type 2 external skeletal fixotor (ESF). Full (100%) axial dynamization of one randomly selected ESF in each dog was performed at 31 days postoperatively. Caudo-cranial radiographs were obtained at weekly intervals, which were qualitatively and quantitatively evaluated (densitometry and ImageJ analysis). The dogs were euthanatized 13 weeks postoperatively, at which time dual energy x-ray absorptiometry (DEXA), peripheral quantitative computed tomography (pQCT), mechanical testing in torsion, and qualitative histological analysis were performed. A two-tailed paired Student's t-test was performed for statistical analysis of all parameters of interest, with significance set at p < 0.05. Three of five dynamized bones bridged quicker, and four of five dynamized bones appeared to have greater callus formation, however, statistically significant differences could not be definitively determined. Statistically significant differences were not found with densitometry (any time frame), DEXA, pQCT, torsional stiffness or maximum torque. Despite the lack of statistically relevant data, trends were observed with larger callus size and density in the dynamized tibiae. The dynamized tibiae appeared to fracture more consistently outside of the area of the healing callus as compared to the control tibiae. Histological evaluation showed greater remodelling in four of five control limbs when compared to the dynamized limb. Dynamization at 31 days post-operatively may delay bone remodelling, despite a trend towards a larger callus size. The results of this study failed to show a definitive role for early full axial dynamization.

Objective: To characterize the mechanical performance of a veterinary bone anchor under static and cyclic loads., Study Design: Mechanical testing study., Animals: Cadaveric canine humeri., Methods: Humeri (6 pairs) were collected from skeletally mature dogs (mean [+/-SD] age, 17.2+/-2.1 months; weight, 20.8+/-1.5 kg). Bone anchors were inserted in the proximal metaphysis using nylon, and were longitudinally extracted. For the opposite humerus, anchors were subjected to longitudinal cyclic load (50% of the load at failure of their pair) for 1200 cycles then longitudinally loaded to failure. Anchors were then installed in a similar and adjacent area of these 2(nd) humeri with nylon and cyclically tested perpendicular to the axis of anchor insertion (100% of the longitudinal holding power of their pair) for 1200 cycles, then perpendicularly loaded to failure. Paired t-tests were used to compare holding power before and after longitudinal cyclic testing., Results: Longitudinal holding power of the screw-type anchor in the proximal humerus was 385+/-30 N. Anchor pullout was the only mode of failure. Anchors in the paired humeri did not fail after 1200 cycles of 50% longitudinal loading, and post-cycle holding strength was not different (335+/-87 N; P=.32). Perpendicularly loaded anchors did not fail after 1200 cycles of 100% of opposite longitudinal holding strength, and had post-cycle perpendicular holding strengths of 514+/-72 N. Suture breakage was the mode of failure., Clinical Relevance: Bone anchor holding strength is dependent on orientation of suture load. Screw-type bone anchor holding strength was not affected by longitudinal cyclic loading, and holding strengths of approximately 385 N can be expected in metaphyseal bone of large-breed mature dogs. Perpendicularly loaded anchors have higher failure loads, and holding strength of approximately 514 N can be expected in metaphyseal bone of the proximal humerus.

Objective: To determine if screw loosening in triple pelvic osteotomies (TPO) is minimized when screws cranial to the ilial osteotomy had maximal sacral purchase., Study Design: Prospective study., Animals: Forty-six dogs with decreased acetabular coverage of the femoral head and minimal degenerative joint changes., Methods: TPOs were performed where screws cranial to the ilial osteotomy were inserted to maximally engage sacral bone. Data collected were: use of ilial and ischial cerclage wire, screw length, ventrodorsal radiographic sacral width (most caudal aspect), pelvic canal diameter, and sacral penetration of the 3 cranial screws. On all subsequent radiographs, changes in screw position, pelvic canal diameter, and sacral purchase were noted., Results: For 69 TPOs, 414 screws were used. Mean radiographic cranial screw length was 34.54 mm. Combined sacral depth of all 3 screws was 93.3% of sacral width. All osteotomies healed uneventfully. Twenty-four screws (6%) loosened with 12 being in the most cranial positions. Use of ischial or ilial cerclage wires did not statistically influence screw loosening. Pelvic diameter decreased by a mean of 7.79% from postoperative radiographs to the last radiographic recheck., Conclusions: By sufficiently engaging the sacrum with screws cranial to the ilial osteotomy, implant failures can be avoided and screw loosening minimized when a 6-hole TPO plate is used., Clinical Relevance: To minimize screw-loosening in TPO, screws inserted cranial to the ilial osteotomy should be inserted to maximum sacral depth without penetrating the vertebral canal.

Objective: To quantify the effect on gap stiffness and cranial to caudal bending stiffness of conversion of the 6 distal clamps of planar bilateral fixator models to sliding clamps and the effect of attachment of composite beams to the sliding clamp models., Study Design: Mdash;Mechanical testing performed on models., Sample Population: Five models using birch dowels and a commercially available external skeletal fixator system., Methods: A segmentally comminuted, middiaphyseal fracture was simulated with the use of wooden dowels, and a bilateral 6-pin fixator was applied to create each of 5 models. The models were mechanically tested with all fixed clamps, with the 6 distal clamps converted to sliding clamps and with composite beams attached to the sliding clamp models. Testing was carried out in axial loading with physiologically relevant loads for a canine model, and in bending in the cranial to caudal plane., Results: Sliding clamp fixators with composite beams attached exhibited a nonlinear increase in axial loading gap stiffness as load increased. The composite beam group also exhibited an increase in cranial to caudal bending stiffness as compared with fixed clamp and sliding clamp models., Conclusions: Using composite beam elements, planar bilateral external fixators can be constructed such that the fracture site would undergo controlled amounts of displacement at low loads and lessening displacement at higher loads., Clinical Relevance: The nonlinear stiffness profile attained by the addition of composite beam elements to a planar external fixator allows controlled axial micromotion at the fracture site. Because controlled axial micromotion appears to stimulate fracture healing, a nonlinear stiffness profile of this type should enhance fracture healing., (Copyright 2003 by The American College of Veterinary Surgeons)

Objective: To assess the effect of a supplemental plate on the stiffness of a six-pin unilateral external skeletal fixator., Study Design: Mechanical testing performed on models., Methods: Wooden (birch) dowels were used to create five models of a fracture. A commercially available external fixation system was applied to the model with a uniform unilateral six-pin fixator design. The models were mechanically tested with and without a supplemental plate attached to the 2 clamps adjacent to the fracture gap. Testing was conducted in axial loading, medial to lateral bending, and cranial to caudal bending., Results: Results showed a 4.42-fold increase in stiffness in axial load, a 4.23-fold increase in stiffness in medial to lateral bending, and a 1.94-fold increase in stiffness in cranial to caudal bending with the addition of the plate., Conclusions: The addition of a supplemental plate increases the mechanical stiffness of unilateral fixators. This was especially true in axial load and medial to lateral bending., Clinical Relevance: A supplemental plate can be used with unilateral fixators to increase stiffness of the fixator. Conversely, the plate can be removed to decrease stiffness without the removal of fixation pins., (Copyright 2002 by The American College of Veterinary Surgeons)

Several studies have reported enhanced repair of damaged cartilage following implantation of mesenchymal stem cells (MSCs) into full-thickness cartilage defects suggesting that the cells in the repair tissue were derived from the implant. However, it cannot be excluded that the enhanced tissue repair is derived from host cells recruited to the defect in response to the implant, rather than the re-population of the tissue by the implanted MSCs. Our objective was to study the short-term fate of fluorescently labeled MSCs after implantation into full-thickness cartilage defects in vivo. The fluorescent dye used in our studies did not affect MSC viability or their ability to undergo osteogenic and chondrogenic differentiation in vitro. MSC gelatin constructs were implanted into full-thickness cartilage defects in goats. These cells retained the dye and were detectable by histology and flow cytometry. At intervals spanning 2 weeks post-implantation we observed gradual loss of implanted cells in the defect as well as fragments of gelatin sponge containing labeled MSCs in deep marrow spaces indicating fragmentation, dislodgement and passive migration. Fluorescent labeling enabled us to determine whether the implanted cells were lost during early time points after implantation as well as their spatial orientation throughout the defect. By determining the fate of implanted cells, new biomaterials could be engineered to correct undesirable characteristics. Testing of new biomaterials in short-term in vivo models would provide faster optimization for cell retention needed for successful, long-term cartilage regeneration.

We report another technique of transcranial magnetic stimulation (TMS) for exciting the originating cells of the descending corticospinal tract. A cap shaped TMS coil has been described for simultaneously exciting muscles in all four extremities. This TMS coil is useful for monitoring the functional integrity of the descending motor paths during spinal cord surgery, because information regarding the integrity of both the left and right sides of the spinal cord motor paths can be obtained concurrently. Despite the improved design of the cap coil, careful placement is required for achieving bilateral spinal cord motor responses. Cortical mapping was used to identify the optimum scalp foci for the muscles studied. The cap coil must overlap these foci to simultaneously elicit compound muscle action potentials (CMAPs) in all four extremities. Increasing TMS stimulation intensity will increase the magnitude of the acquired CMAPs responses without significantly changing latency.

A 21-mm defect was created in 1 femoral diaphysis each of 15 dogs. Periosteum as well as a cylinder of bone was removed, and the defect was stabilized with a bone plate. Twelve of the defects were filled with an equal volume of autogenous cancellous bone harvested from the ipsilateral ilium. Three defects were left untreated. Cranial to caudal radiographs were taken postoperatively and every 4 weeks for 16 weeks. The radiographs were evaluated for healing using two ordinal scales. At 16 weeks, the dogs were euthanized and the femurs harvested for biomechanical testing and histologic evaluation. Both operated and contralateral not operated femurs were mechanically tested to failure in torsion, and load at failure and stiffness were calculated. All dogs tolerated the procedure well, and were using the operated limb within 1 or 2 days postoperatively. There were no complications noted during the 16 weeks of the study. Unfilled defects did not heal and became atrophic nonunions. The defects filled with autogenous cancellous bone healed in a consistent pattern of consolidation, incorporation, and remodeling, with uniform increases of both ordinal scales used. The femoral cortex opposite the bone plate demonstrated most mature remodeling, evident both radiographically as well as histologically. Unoperated femurs failed at 13.61 +/- 3.88 N-m and grafted femurs failed at 2.96 +/- 1.3 N-m, which was 23% of the measurement of the unoperated femur. Relative stiffness of the unoperated femurs was 5974 +/- 4316 N-m2/radian, and grafted femurs had a relative stiffness of 642 +/- 561 N-m2/radian, which was 10.4% of the measurement of unoperated femur. This model proved to be a critically sized defect, which when left unfilled resulted in an atrophic nonunion, and when filled with cancellous bone resulted in a consistent healing pattern.

Bone marrow contains a population of rare progenitor cells capable of differentiating into bone, cartilage, muscle, tendon, and other connective tissues. These cells, referred to as MSCs, can be purified and culture expanded from animals and humans. This review summarizes recent experimentation focused on characterizing the cellular aspects of osteogenic differentiation, and exploration of the potential for using autologous stem cell therapy to augment bone repair and regeneration. The authors have completed an array of preclinical studies showing the feasibility and efficacy of MSC based implants to heal large osseous defects. After confirming that syngeneic rat MSCs could heal a critical size segmental defect in the femur, it was established that human MSCs form bone of considerable mechanical integrity when implanted in an osseous defect in an immunocompromised animal. Furthermore, bone repair studies in dogs verify that the technology is transferable to large animals, and that the application of this technology to patients at geographically remote sites is feasible. These studies suggest that by combining MSCs with an appropriate delivery vehicle, it may be possible to offer patients new therapeutic options.

Bone marrow has been shown to contain a population of rare mesenchymal stem cells that are capable of forming bone, cartilage, and other connective tissues. We examined the effect of cultured autologous mesenchymal stem cells on the healing of critical-sized (twenty-one-millimeter-long) segmental defects in the femora of adult female dogs. Autologous mesenchymal stem cells were isolated from bone marrow, grown in culture, and loaded onto porous ceramic cylinders consisting of hydroxyapatite (65 per cent) and beta-tricalcium phosphate ceramic (35 per cent). The animals were randomly assigned to one of three groups. In Group A (six dogs), a porous ceramic cylinder that had been loaded with autologous mesenchymal stem cells was implanted in the defect. In Group B (six dogs), a ceramic cylinder that had not been loaded with cells was placed in the defect. In Group C (three dogs), the defect was left untreated (no ceramic cylinder was implanted). Radiographs were made immediately after the operation and at four-week intervals. At sixteen weeks, the animals were killed, the involved femora were removed, and undecalcified histological sections from the defects and adjacent bone were prepared. Histological and histomorphometric studies were carried out to examine the healing of the defects and the formation of bone in and around the ceramic implants. Atrophic non-union occurred in all of the femora that had untreated defects, and only a small amount of trabecular bone formed at the cut ends of the cortex of the host bone in this group. In contrast, radiographic union was established rapidly at the interface between the host bone and the implants that had been loaded with mesenchymal stem cells. Numerous fractures, which became more pronounced with time, developed in the implants that had not been loaded with cells. Histological and morphometric analyses demonstrated that both woven and lamellar bone had filled the pores of the implants that had been loaded with mesenchymal stem cells; the amount of bone was significantly greater (p < 0.05) than that found in the pores of the implants that had not been loaded with cells. In addition, a large collar of bone (mean maximum thickness, 3.14 millimeters) formed around the implants that had been loaded with cells; this collar became integrated and contiguous with callus that formed in the region of the periosteum of the host bone. The collar of bone remodeled during the sixteen-week period of study, resulting in a size and shape that were comparable with those of the segment of bone that had been resected. Callus did not develop around the cortex of the host bone or around the defect in any of the specimens in the other two groups.

Objective: To compare two external fixation clamp designs for their ability to resist movement of a fixation pin in relation to the connecting rod., Study Design: Two designs of external fixator clamps were attached to connecting rods mounted on a jig for mechanical testing. Fixator pins were placed perpendicular to the connecting rod. A mechanical testing machine was used to deflect each 3.2-mm pin at a distance that was 25 mm from the center of the clamp bolt. Both clamp designs were tightened to 4.4, 6.1, and 7.8 newton-meters (N x m) torque, and loads were applied in a position ramp through 4 mm and resisting loads were measured. Two clamp orientations were used during load application, such that the deflection of the pin tended to tighten the clamp bolt or tended to loosen the clamp bolt. The tests were videotaped to determine mode of failure. Comparisons of the load/displacement curves for the two external fixator clamp designs were made using nonlinear equational curve fitting methods. The resultant plateau and rise coefficients were compared using analysis of variance., Results: Slippage of the pin in relation to the clamp occurred with the Kirschner-Ehmer clamp tightened to 4.4, 6.1, and 7.8 N x m, and slipping of the pin in relation to the clamp occurred with the experimental clamp design tightened to 4.4 and 6.1 N x m but not to 7.8 N m. At 7.8 N x m, the 3.2-mm pin deformed plastically with the experimental clamp design. Increasing the torque of the clamp bolt resulted in superior plateau coefficients for both clamp designs. At each level of tightness and in each clamp orientation to applied pin load, the experimental clamp design provided greater plateau coefficients than did the Kirschner-Ehmer clamp design. At 7.8 N x m of tightness, the Kirschner-Ehmer clamp and bolt bent, whereas only slight plastic deformation of the experimental clamp design occurred., Conclusions: The experimental external fixator clamp was more secure in resisting fixator pin movement at all levels of tightening compared with the Kirschner-Ehmer-type external fixator clamp. At 7.8 N x m of tightening, the new clamp design did not allow slippage of the pin within the clamp., Clinical Significance: The experimental external fixator clamp should result in greater rigidity of fixator configurations, in addition to providing design features that allow addition of a clamp between two installed clamps, sleeved predrilling of pilot holes for all pins, measurement of pin depth, and placement of positive profile pins at all sites.

A new external fixation system for repair of fractures of the radius and tibia was developed that uses positive-profile threaded pins. This system allows for addition of a fixation clamp between 2 installed clamps, predrilling of pin holes through a drill sleeve, use of positive-profile threaded pins in all locations, and easier application of full pins. Type-II external fixators were applied, using this system, to fractures in 10 client-owned dogs, and outcome was evaluated. All fractures healed without complications. Duration of surgery, mean time until radiographic evidence of a bridging callus, and mean time until removal of the external fixator were shorter, and frequency of pin loosening were less than with other techniques. Pin loosening was uncommon. This system provides an important improvement in external skeletal fixation.

Objective: To evaluate the efficacy of combined administration of platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF-I) on the regeneration of transected and anastomosed sciatic nerves., Animals: 25 male Lewis rats., Procedure: Transection and anastomosis was performed of the left sciatic nerve of all rats. At the time of surgery, treatment group rats received a combination of PDGF (0.75 microgram) and IGF-I (1.5 micrograms) along with vehicle (2% methyl cellulose gel) at the anastomosis site. Control rats received vehicle alone. Evaluation consisted of motor evoked potentials and nerve conduction velocity, quantitative histologic examination, sciatic functional index, and visual assessment of repair organization (lesion scores)., Results: Significant differences in motor evoked potential latency, nerve conduction velocity, axon number, sciatic functional index, or lesion scores were not found between groups., Conclusions: Combined administration of PDGF and IGF-I did not enhance peripheral nerve regeneration in a transection and anastomosis model as determined 6 weeks after surgery., Clinical Relevance: These findings support the assumption that mechanical, versus trophic, effects predominate when nerve ends are closely apposed.

Motor-evoked potentials elicited from transcranial magnetic stimulation were recorded from both cranial tibial muscles of 10 Lewis rats. One sciatic nerve was then transected and surgically reanastomosed and allowed to regenerate for 6 weeks. Walking function was tested weekly using a footprint test giving a functional sciatic nerve index. At the end of the study motor-evoked potentials were again performed, as were nerve conduction velocities and supramaximal stimulation of operated and unoperated sciatic nerves. The nerve was evaluated for myelinated axon numbers. Functional sciatic index, numbers of myelinated axons, nerve conduction velocities, and supramaximal stimulation demonstrated the regenerated nerve to be functional, but to a lesser extent than the unoperated nerve. In all cases the amplitude of the compound muscle action potential evoked from transcranial magnetic stimulation of the motor cortex was greater in the operated motor pathway. This finding demonstrates hyperexcitability of the motor pathway to magnetic stimulation during peripheral nerve regeneration.

Brain tumors occur commonly in small animals. The clinical history and physical examination findings can strongly suggest their presence. Specifically, an older dog with onset of seizures and behavioral changes, or an older cat with behavioural changes and weakness, should be further evaluated for the presence of a brain tumor. A thorough neurological examination should be performed to localize the lesion(s). Groups of neurological signs will suggest the tumor to be cerebral, cerebellar, or brainstem. Cerebral tumors without brainstem signs carry the best prognosis, especially for cats. Patients suspected of having brain tumors should be imaged with computed tomography, or magnetic resonance imaging. Initial medical therapy includes anticonvulsants and glucocorticosteroids. Cerebral tumors not located on the floor of the calvarium can be successfully excised. These and other tumors can also be treated with radiation therapy.

The pathophysiology of spinal cord injury can be categorized as acute impact or compression. Acute impact injury is a concussion of the spinal cord. This type of injury initiates a cascade of events focused in the gray matter, and results in hemorrhagic necrosis. The initiating event is a hypoperfusion of the gray matter. Increases in intracellular calcium and reperfusion injury play key roles in cellular injury, and occur early after injury. The extent of necrosis is contingent on the amount of initial force of trauma, but also involves concomitant compression, perfusion pressures and blood flow, and administration of pharmacological agents. Preventing or quelling this cascade of events must involve mechanisms occurring in the initial stages. Spinal cord compression occurs when a mass impinges on the spinal cord causing increased parenchymal pressure. The tissue response is gliosis, demyelination, and axonal loss. This occurs in the white matter, whereas gray matter structures are preserved. Rapid or a critical degree of compression will result in collapse of the venous side of the microvasculature, resulting in vasogenic edema. Vasogenic edema exacerbates parenchymal pressure, and may lead to rapid progression of disfunction. Treatment of compression should focus on removal of the offending mass.

A modified technique for distraction-stabilization that used an interbody polymethyl methacrylate plug was performed in 22 dogs with confirmed caudal cervical spondylomyelopathy. Myelographically, all compressive lesions were dynamic and predominantly located ventral to the spinal cord. Nineteen of 21 (90%) dogs for which success/failure could be determined had a successful outcome, and 11 of 22 (50%) dogs attained normal neurologic status. The 2 cases that were considered failures involved dogs that were nonambulatory tetraparetic prior to surgery and failed to improve to a functional status. Complications were self-limiting and included ventral displacement of the cement without loss of distraction in 1 dog and diskosponsylitis at an adjacent disk space in another dog. Evidence of fusion of the affected vertebrae, in the distracted position, was radiographically evident in all dogs. Use of the interbody polymethyl methacrylate plug appears to be a viable surgical treatment of caudal cervical spondylomyelopathy in dogs.

Three dogs and 2 cats were treated by partial scapulectomy for management of sarcomas of the proximal aspect of the scapula. Surgical margins were considered complete in all cases. In 3 animals, limb function was excellent for 8, 18, and 24 months, respectively, after surgery. Poor limb function persisted in 1 dog that developed local metastatic disease to the affected forelimb. One dog had good limb function for 3 months after surgery and underwent force-plate analysis, which determined a reduction in peak vertical force, decelerating force, and stride time for the affected limb, compared with that for the forelimb that was not subjected to surgery. Tumor recurrence associated with fibrosarcomas was detected in 2 animals. In selected cases, partial scapulectomy can preserve limb function and may be considered a viable alternative to limb amputation.

Experimental island and peninsular axial pattern flaps that incorporated the cranial superficial epigastric artery and vein were developed in 6 Beagles. Mean percentage of flap area that survived, for both flaps, was 87%, and percentage of surviving flap area was not significantly different for island versus peninsular flaps. In 1 dog, ligation of an aberrant, perforating branch of the cranial epigastric artery resulted in necrosis of 53% of the flap area. The cranial superficial epigastric axial pattern flaps have potential application for closure of skin defects within their arc of rotation and may be particularly useful for closure of large defects on the ventral aspect of the thorax. A peninsular flap was used to close a defect of the ventral portion of the thoracic wall in a clinical case.

The vascular and microvascular anatomy of the equine deep digital flexor tendon (DDFT) within the digital sheath was studied by injecting the vasculature with either colored latex or barium sulphate for radiographic, microangiographic, histologic, and computed tomographic (CT) evaluation. Consecutive 4-mm thick two-dimensional CT slice data were reconstructed to 3-dimensional volumetric images to enhance spatial evaluation of the blood supply. Gross dissection and angiographic studies identified three major vascular sources. Above the fetlock, the DDFT was supplied by either a branch of the medial palmar artery (Arteriae digitalis palmaris communis II) or a branch of the medial palmar digital artery (A. digitalis [palmaris propria III] medialis). Below the fetlock, the DDFT was supplied by branches from the lateral and medial palmar branches to the proximal phalanx (Ramus palmaris phalangis proximalis). The most distal aspect of the tendon received small branches from the medial and lateral palmar digital arteries. Using histology and microangigraphy we observed an extensive and uniform intratendinous vascular network above and below the fetlock, with a relatively avascular region of tendon palmar to the fetlock. The most distal 2.0 to 2.5 cm of the tendon within the sheath was heavily infiltrated with fibrocartilage along its dorsal aspect.

A 3.5-mm cortical orthopedic screw was compared with a 4.0-mm cancellous screw for maximal load to failure in the pelvis of immature dogs. The pelvis from young cadavers (7 to 13 months old) was divided into hemipelves and used for testing of the 2 screw types. Two sites in each hemipelvis were used, mid-shaft of the ilium and mid-sacrum, including the wing of the ilium. The screws were extracted, and maximal load to failure and mode of failure were recorded. Maximal load to failure per millimeter of engaged thread was calculated. In either pelvic site, the 4.0-mm cancellous screw required a significantly (P < 0.05) higher pullout force per millimeter of engaged screw threads than did the 3.5-mm cortical bone screw.