Accuracy of Lumbosacral Pedicle Screw Placement in Dogs: A Novel 3D Printed Patient-Specific Drill Guide versus Freehand Technique in Novice and Expert Surgeons.

OBJECTIVE: The aim of this study was to compare the accuracy of pedicle screw placement at the canine lumbosacral junction using a novel unilateral three-dimensional printed patient-specific guide (3D-PSG) versus a freehand drilling technique. Additionally, accuracy of screw placement between a novice and an experienced surgeon was determined. STUDY DESIGN: Preoperative computed tomography images from 20 lumbosacral cadaveric specimens were used to design a novel unilateral 3D-PSG for the L7 and sacral vertebrae which was printed in acryl-nitrile butadiene styrene plastic. A novice and an expert surgeon each placed 3.5mm cortical screws in 10 cadavers; on the left using the unilateral 3D-PSG and by the freehand (anatomic landmark) technique on the right. RESULTS: Sixty screws were placed using the unilateral 3D-PSG and 60 using the freehand technique. There was no statistical difference in accuracy for the comparison between methods performed by the expert (p = 0.679) and novice (p = 0.761) surgeon, nor between an expert and novice surgeon overall (p = 0.923). Unexpectedly, the use of a unilateral 3D-PSG increased variability for the expert surgeon in our study (p = 0.0314). CONCLUSION: Using a novel unilateral 3D-PSG did not improve the accuracy of screw placement for lumbosacral stabilization by a novice surgeon compared with an expert surgeon in lumbar spine surgery. This may reflect a suboptimal PSG design.

Polyaxial pedicle screw external fixation to stabilize oblique mandibular fractures in three standing, sedated horses.

OBJECTIVE: To report the radiographic, surgical and postoperative features in horses with unstable oblique mandibular fractures secured with polyaxial pedicle screws (PPS) external fixation construct and intraoral wiring. ANIMALS: Three client-owned horses. STUDY DESIGN: Short case series. METHODS: Two horses each had a unilateral fracture, which did not improve after conservative management, and one horse had bilateral fractures. Clinical and radiographic features were documented. Polyaxial pedicle screw external fixators and intraoral tension band wiring were applied in standing horses after combining sedation and regional nerve anesthesia. Intraoral wires were implanted through a lateral buccotomy between teeth (two horses) or burred through exposed crown (one horse) and then secured around the incisors. The PPS were inserted under radiographic guidance to avoid tooth roots. Healing was assessed with radiographic examination. The PPS external fixator rod and intraoral wires were removed first. The mandible was manipulated, and, if it was stable, the PPS were removed. RESULTS: Implants were removed at 6, 8, or 10 weeks after the mandibles were palpably stable. Complications included broken wires in one horse, bone sequestration in one horse, and infection in one horse. Follow-up communication with the owners 12 to 18 months later confirmed complete healing without further complications of the fractured mandibles or teeth. CONCLUSION: Polyaxial pedicle screw external fixation led to fracture healing and a return to function in all three horses. The complications encountered did not preclude a successful outcome. CLINICAL SIGNIFICANCE: Polyaxial pedicle screw external fixation coupled with intraoral wiring provides an alternative to treat unstable equine mandibular fractures without general anesthesia.

Accuracy of Placement of Pedicle Screws in the Lumbosacral Region of Dogs Using 3D-Printed Patient-Specific Drill Guides.

OBJECTIVE: The aim of this study was to report the accuracy of pedicle screw placement using three-dimensional (3D)-printed, patient-specific drill guides in the lumbosacral region of dogs. STUDY DESIGN: This was a retrospective study. Thirty-two pedicle screws were placed in five dogs. Medical records were reviewed between November 2015 and November 2018 for dogs showing clinical signs associated with cauda equina syndrome. Inclusion criteria included preoperative magnetic resonance imaging, pre- and postoperative computed tomography (CT) and dorsal stabilization, with pedicle screws placed using 3D-printed, patient-specific drill guides and polymethylmethacrylate. Screw placement was evaluated for medial or lateral breaching on postoperative CT. RESULTS: Five dogs met the inclusion criteria. Four had degenerative lumbosacral stenosis and one had discospondylitis. All dogs had failed medical management prior to surgery. Of 32 bicortical pedicle screws placed, 30 were fully contained inside the pedicle and 2 were partially breaching the vertebral canal (less than one-third of the screw diameter). Postoperative CT revealed good alignment of L7-S1 in all planes. CONCLUSION: This technique enabled an accurate and safe placement of pedicle screws in the lumbosacral region of dogs with lumbosacral disease. Three-dimensional, printed patient-specific drill guides are a safe and effective method of placing pedicle screws in dogs with lumbosacral disease.

Enxerto pediculado de omento maior como adjuvante no tratamento de osteomielite de tíbia em cão - relato de caso / [Greater omentum pedicle flap as adjunctive treatment of tibial osteomyelitis in a dog - case report]

A osteomielite é um desafio terapêutico em ortopedia, capaz de retardar ou mesmo impedir a consolidação óssea. O omento, há anos, tem sido empregado como alternativa em diferentes procedimentos cirúrgicos, por sua capacidade, entre outras, de angiogênese, sendo aplicado na ortopedia veterinária quando há o risco de não união óssea. Neste caso, um cão Fila Brasileiro foi submetido à realização de enxerto com retalho pediculado de omento maior, após osteomielite resistente presente em osteossíntese de fratura múltipla de tíbia aberta grau II. Durante 16 dias, manteve-se a comunicação do retalho, mas, diante do risco de peritonite, o pedículo foi seccionado. Numa sequência de intervenções cirúrgicas, após 89 dias, houve cicatrização óssea e remissão da osteomielite, mesmo na presença de bactérias multirresistentes. Neste relato, o omento foi efetivo como terapia adjuvante no tratamento da osteomielite e garantiu o retorno da função do membro.(AU)

Osteomyelitis is a therapeutic challenge in orthopedics, capable of delaying or even preventing bone healing. The omentum has been used in different surgical procedures as an alternative for its capacity, among others, of angiogenesis, being applied in veterinary orthopedics, when there is a risk of non-union of bone. In this case, a Brazilian row dog was submitted to grafting with pedicle flap of greater omentum, after resistant osteomyelitis present in open fracture osteosynthesis of open tibia grade II. For 16 days the communication of the flap was maintained, but at the risk of peritonitis, the pedicle was sectioned. In a sequence of surgical interventions, after 89 days, there was bone healing and remission of osteomyelitis, even in the presence of multi-resistant bacteria. In this report, the omentum was effective as adjuvant therapy in the treatment of osteomyelitis and guaranteed the return of limb function.(AU)

Biomechanical comparison of locking compression plate fixation and a novel pedicle screw external fixation to repair equine mandibular fractures.

OBJECTIVE: To determine the biomechanical properties of pedicle screw external fixation (PDW) for equine mandibular fracture repair and compare PDW to locking compression plates (LCP). STUDY DESIGN: Cadaveric study. SAMPLE POPULATION: Sixteen adult equine mandibles. METHODS: Four mandibles were kept intact, while 12 were osteotomized and stabilized with the LCP or PDW construct (6 mandibles/group). Failure, stiffness, and yield were calculated from quasi-static ramp to failure and compared with previous analysis of mandibular fracture constructs. Tooth root involvement and method of failure were determined from radiographs and videos. RESULTS: Locking compression plate constructs achieved greater stiffness and load at failure (4656 ± 577 N-m/radian, 558 ± 27 N-m P < .05) compared with PDW constructs (2626 ± 127 N-m/radian, 315 ± 48 N-m). Yield did not differ between types of fixation (369 ± 57 N-m, 193 ± 35 N-m, P = .145). Tooth involvement was noted in two LCP constructs with failure via bone fracture. Pedicle screw external fixation constructs failed via wire unraveling and screw bending. CONCLUSION: Locking compression plate fixation increased stiffness and failure of constructs but did not influence yield. It also increased the risk to tooth root involvement relative to fixation with PDW. Compared with another study, PDW offered stiffness and failure similar to an intraoral splint with interdental wires, external fixator (EF), and external fixator with wires (EFW) and yield similar to an EF, an EFW, and a dynamic compression plate. CLINICAL RELEVANCE: Pedicle screw external fixation offers biomechanical stability comparable to other relevant mandibular fixation techniques and reduces the risk of tooth root damage compared with LCP fixation.

Temporary Segmental Distraction in a Dog with Degenerative Lumbosacral Stenosis.

OBJECTIVES: Degenerative lumbosacral stenosis (DLSS) is characterized by intervertebral disc degeneration and causes lower back pain in dogs. Temporary distraction in rabbit models with induced intervertebral disc degeneration showed signs of intervertebral disc repair. In the present study, we assessed safety and efficacy of temporary segmental distraction in a dog with clinical signs of DLSS. METHODS: Distraction of the lumbosacral junction by pedicle screw-rod fixation was applied in a 5-year-old Greyhound with DLSS and evaluated by radiography, magnetic resonance imaging, and force plate analysis before and after distraction. RESULTS: Safe distraction of the lumbosacral junction was demonstrated, with improvement of clinical signs after removal of the distraction device. Signal intensity of the intervertebral disc showed no changes over time. T2 value was highest directly after removal of the distraction device but decreased by 10% of the preoperative value at 9 months of follow-up. Disc height decreased (8%) immediately after removal of the distraction device, but recovered to the initial value. A decrease in the pelvic/thoracic propulsive force during pedicle screw-rod fixation and distraction was demonstrated, which slowly increased by 4% compared with the initial value. CLINICAL SIGNIFICANCE: Temporary pedicle screw-rod fixation in combination with distraction in a dog with DLSS was safe, improved clinical signs and retained disc height at 9 months of follow-up.

Kinematic behavior of a novel pedicle screw-rod fixation system for the canine lumbosacral joint.

OBJECTIVE: To determine the biomechanical behavior of a novel distraction-stabilization system, consisting of an intervertebral distraction bolt, polyaxial screws, and connecting rods, in the canine lumbosacral spine. STUDY DESIGN: Biomechanical study. SAMPLE POPULATION: Cadaveric canine lumbosacral spines (L4-Cd3) (N = 8). METHODS: Cadaveric lumbosacral spines were harvested, stripped of musculature, mounted on a 4-point bending jig, and tested in extension, flexion, and lateral bending using nondestructive compressive axial loads (0-150 N). Angular displacement was recorded from reflective optical trackers rigidly secured to L6, L7, and S1. Data for primary and coupled motion were collected from intact spines, after destabilization at L7-S1, and following surgical stabilization with the new implant system. RESULTS: As compared with the intact spine, laminectomy resulted in a modest increase in angular displacement at L6-L7 and a marked increase at L7-S1. Instrumentation significantly reduced motion at the operated level (L7-S1) with a concomitant increase at the adjacent level (L6-L7). CONCLUSION: The combination of a polyaxial pedicle screw-rod system and intervertebral spacer provides a versatile solution of surgical stabilization of the lumbosacral joint following surgical decompression in the canine lumbosacral spine. The increase in motion at L6-L7 may suggest the potential for adjacent level effects and clinical trials should be designed to address this question. CLINICAL RELEVANCE: These results support the feasibility of using this new implant system for the management of degenerative lumbosacral disease in dogs. The increase in motion at L6-L7 may suggest the potential for adjacent level effects and clinical trials should be designed to address this question.

Effect of a titanium cage as a stand-alone device on biomechanical stability in the lumbosacral spine of canine cadavers.

Degenerative lumbosacral stenosis is a common disease in dogs characterised by intervertebral disc herniation, loss of disc height and stenosis. Decompressive dorsal laminectomy and partial discectomy can cause spinal instability and worsen foraminal stenosis. Pedicle screw and rod fixation (PSRF) with an intervertebral body cage allows for distraction and restoration of disc height and restores foraminal apertures. The aim of this study was to evaluate the ex vivo biomechanical properties of a titanium intervertebral cage alone and in combination with PSRF in the lumbosacral spine of dogs. The range of motion, neutral zone, neutral zone stiffness and elastic zone stiffness of the lumbosacral joint (L7-S1) of nine canine cadavers were determined in flexion/extension, lateral bending and axial rotation for four conditions: (1) native (unmodified) spine; (2) dorsal laminectomy and discectomy; (3) stand-alone cage; and (4) cage in combination with PSRF. The intervertebral disc height decreased after dorsal laminectomy, but increased after insertion of the cage. Insertion of the stand-alone cage decreased the range of motion and neutral zone compared to the laminectomy-discectomy and increased neutral zone stiffness in all directions. The range of motion further decreased after PSRF. From a biomechanical point of view, the use of a stand-alone intervertebral cage is a potential alternative to dorsal fixation of the lumbosacral junction, since it increases spinal stability and restores disc height.