Mechanical comparison of straight and pre-bent interlocking nails used for the stabilization of a tibial gap fracture model.

OBJECTIVE: To compare the mechanical behavior of straight (STRT) and pre-bent (BENT) I-Loc angle-stable interlocking nails (AS-ILN) used for stabilization of canine mid-diaphyseal tibial fractures. STUDY DESIGN: In vitro experimental study. SAMPLE POPULATION: Tibial gap fracture models (n = 5/group). METHODS: Tibial models simulating a comminuted mid-diaphyseal fracture were stabilized with either a STRT or BENT I-Loc AS-ILN. Bent nails were contoured to match the 10° tibial recurvatum of a mid-size dog. Constructs were subjected to cyclic eccentric compressive loads followed by ramp load until failure. Construct compliance, maximum compressive load and resistive torque, yield load and angular deformation at 450 N were statistically compared using t-tests (p < .05). Failure modes were described. RESULTS: Compliance was 45% lower in BENT than STRT groups (p < .0001). Constructs in the BENT group sustained ~20% and 34% greater maximum and yield loads, respectively, than STRT constructs. Maximum resistive torques were similar between groups (p = .16). At 450 N, sagittal plane angular deformation increased from 0° to 4° in procurvatum (STRT group) and decreased from 10° to 8° in recurvatum (BENT group-p < .0001). Construct yield failure occurred at the nail isthmus in both groups. CONCLUSION: These results demonstrated that, in a tibial gap fracture model, pre-bending I-Loc AS-ILNs provided mechanical advantages by increasing their ability to resist bending resulting from eccentric compressive loads. CLINICAL SIGNIFICANCE: Pre-bending may reduce the occurrence of tibial nail yield failure. Surgeons should therefore consider pre-bending tibial I-Loc nails to match the bone anatomical recurvatum prior to implantation.

Prospective evaluation of the surgical stabilization and outcome of canine tibial plateau fractures in three cases.

OBJECTIVE: To report the surgical approaches and stabilization of lateral and medial tibial plateau fractures (TPF), as well as the long-term outcome following repair. STUDY DESIGN: Prospective series of three client-owned dogs. ANIMALS: Three dogs. METHODS: For the two lateral TPF cases (Unger type 41-B1), the surgical approach included separation of the lateral collateral ligament and long digital extensor tendon. The lateral meniscus was elevated to allow visualization of the tibial surface and assess fracture reduction. The first case was repaired using two 2.0 mm lag screws (with washers). The second case sustained a lateral TPF, fibular fracture and concurrent tubercle of Gerdy fracture. Both tibial fractures were stabilized using two 2.0 mm lag screws with washers and two 0.9 mm Kirschner wires (K-wires). A third case, diagnosed with an Unger type 41-B2 medial TPF, was treated using 0.9 mm K-wires and 22-gauge tension band. RESULTS: There were no major complications noted. One minor complication occurred (screw yield two weeks postoperatively). By 8 weeks, all patients reached clinical union with good limb function. Owners were contacted 9-36 months postoperatively. LOAD scores and examinations were performed for two of three patients; the third patient was not contactable after relocating out of state. Both cases with completed questionnaires had a LOAD score of 5/52. CONCLUSION: Tibial plateau fractures are rare in canine patients. While challenging, they can be successfully managed using a combination of lag screws, K-wires, and tension band. CLINICAL SIGNIFICANCE: Surgical stabilization of TPF is feasible and may reduce the risk of meniscal injury.

A comparison of the motor effects and analgesic efficacy following lumbar plexus block combined with sciatic nerve block or epidural in dogs undergoing tibial plateau leveling osteotomy.

OBJECTIVE: To compare motor effects and analgesic efficacy following an ultrasound-guided lateral approach to lumbar plexus blockade at L7 and sciatic nerve blockade (LPSNB) against epidural injection in dogs undergoing tibial plateau leveling osteotomy (TPLO). STUDY DESIGN: Prospective, randomized, blinded clinical trial. ANIMALS: A total of 27 healthy adult dogs undergoing unilateral TPLO surgery. METHODS: Dogs were allocated to either LPSNB (bupivacaine 2 mg kg-1, 0.75%) or epidural (morphine PF 0.1 mg kg-1 and bupivacaine 0.5 mg kg-1, 0.75%). Other aspects of clinical management were identical, including anesthetic drug protocol, area of presurgical clipping and bladder care. Time to perform the block, response to surgical stimuli, pain scores, rescue analgesia, time to stand and walk, motor score and time to first urination were recorded. One evaluator, unaware of treatment status, performed all evaluations. Student's t-test or Mann-Whitney U test was used to compare continuous variables between groups, and Fisher's exact test for categorical variables. RESULTS: Median (range) times to stand and walk were shorter for LPSNB [60 (40-120) minutes and 90 (60-150) minutes, respectively, p = 0.003] than for epidural [150 (120-240) minutes and 180 (120-360) minutes, respectively, p = 0.006]. Four dogs required rescue intraoperatively (three in epidural group, one in LPSNB group, p = 0.438). Pain scores over the 24 hour evaluation period were similar, and not significantly different, for each group. Time to spontaneous urination [LPSNB, 330 (240-360) minutes; epidural, 300 (120-1440) minutes, p = 1.0] did not differ between groups. CONCLUSIONS AND CLINICAL RELEVANCE: An ultrasound-guided lateral paravertebral approach to the lumbar plexus within the psoas compartment at L7, combined with sciatic nerve blockade, allows faster return to normal motor function, with similar pain control and impact on urination when compared with epidural in dogs after TPLO surgery.

Post-sterilization Dimensional Accuracy of Methacrylate Monomer Biocompatible Three-Dimensionally Printed Mock Surgical Guides.

OBJECTIVES: The aim of this study was to evaluate the post-sterilization dimensional accuracy of a standardized drilling guide, three-dimensionally printed using biocompatible methacrylate monomers. STUDY DESIGN: A mock surgical guide was designed and printed in five resins (n = 5/material) using a commercially available desktop stereolithography printer. Pre- and post-sterilization dimensions were measured for each sterilization method (steam, ethylene oxide, hydrogen peroxide gas), then statistically compared; p-value less than or equal 0.05 was considered significant. RESULTS: While all resins produced highly accurate replicas of the designed guide, the amber and black resins were unaffected by any sterilization method (p ≥ 0.9). For other materials, ethylene oxide produced the largest dimensional changes. However, mean post-sterilization dimensional changes for all materials and sterilization methods remained less than or equal to 0.05mm CONCLUSION: This study demonstrated that post-sterilization dimensional change of evaluated biomaterials was minimal, and less than previously reported. Additionally, amber and black resins may be preferred to reduce post-sterilization dimensional change, as they were unaffected by any sterilization method. Given the results of this study, surgeons should feel confident using the Form 3B printer to create patient surgical guides. Furthermore, bioresins may provide safer alternatives for patients compared with other three-dimensional printed materials.

Mechanical assessment of two hybrid plate designs for pancarpal canine arthrodesis under cyclic loading.

Pancarpal canine arthrodesis (PCA) sets immobilization of all three carpal joints via dorsal plating to result in bony fusion. Whereas the first version of the plate uses a round hole (RH) for the radiocarpal (RC) screw region, its modification into an oval hole (OH) in a later version improves versatility in surgical application. The aim of this study was to mechanically investigate the fatigue life of the PCA plate types implementing these two features-PCA-RH and PCA-OH. Ten PCA-RH and 20 PCA-OH stainless steel (316LVM) plates were assigned to three study groups (n = 10). All plates were pre-bent at 20° and fixed to a canine forelimb model with simulated radius, RC bone and third metacarpal bone. The OH plates were fixed with an RC screw inserted either most proximal (OH-P) or most distal (OH-D). All specimens were cyclically tested at 8 Hz under 320 N loading until failure. Fatigue life outcome measures were cycles to failure and failure mode. Cycles to failure were higher for RH plate fixation (695,264 ± 344,023) versus both OH-P (447,900 ± 176,208) and OH-D (391,822 ± 165,116) plate configurations, being significantly different between RH and OH-D, p = 0.03. No significant difference was detected between OH-P and OH-D configurations, p = 0.09. Despite potential surgical advantages, the shorter fatigue life of the PCA-OH plate design may mitigate its benefits compared to the plate design with a round radiocarpal screw hole. Moreover, the failure risk of plates with an oval hole is increased regardless from the screw position in this hole. Based on these findings, the PCA plate with the current oval radiocarpal screw hole configuration cannot be recommended for clinical use.

Accuracy of anatomic 3-dimensionally printed canine humeral models.

OBJECTIVE: To evaluate the accuracy of various three-dimensional print (3DP) technologies using morphometric measurements. STUDY DESIGN: Experimental. SAMPLE POPULATION: Cadaveric canine humeri and size-matched 3DP models. METHODS: Fiduciary radiopaque markers were affixed to canine humeri of three different sizes (4, 13, 29 kg) at predetermined anatomical landmarks. 3DP models were created using one of three printers; desktop printers Form 3L and Ultimaker 5S, and industrial printer Objet Connex (n = 5/group/printer). Marker based morphometric dimensions between cadavers and 3DP models were statistically compared using 2-factor repeated measures ANOVA followed by Tukey's post-hoc test (p < .05). RESULTS: Bone size and printer type both significantly affected 3DP accuracy, with size having the larger effect (p < .0001 and p < .02, respectively). Regardless of printing technology, model size was smaller than native bone in most cases. At the humeral condylar level, the best accuracy was seen in the medium-sized humerus with the Ultimaker printer ([0.09 mm], p < .03). Accuracy was reduced in the proximal humerus in all groups. CONCLUSION: Desktop printers were overall more accurate than the industrial printer. Although significant differences were identified between models of different sizes, the submillimetric magnitude of these differences is unlikely to be clinically relevant. CLINICAL SIGNIFICANCE: While preoperative planning using 3DP models is becoming mainstream, accurate representation of the actual bone is critical. This study demonstrates that common desktop printers are suitable for this purpose.

Post-traumatic Osteoarthritis in Rabbits Following Traumatic Injury and Surgical Reconstruction of the Knee.

Post-traumatic osteoarthritis (PTOA) of the knee is often attributed to anterior cruciate ligament (ACL) and meniscus injury. The development of PTOA, however, does not seem to depend on whether or not the damaged ACL is reconstructed. There has been a need to develop animal models to study the mechanisms of PTOA following reconstruction of a traumatized knee. Eighteen rabbits underwent closed-joint trauma to produce ACL rupture and meniscus damage. Then, for the first time, the traumatized knee was surgically repaired in this animal model. Upon euthanasia at 1-, 3- or 6-month post-trauma, joint stability, cartilage morphology and mechanical properties, as well as histology of the cartilage and subchondral bone were evaluated. Trauma-induced knee injury involved 72% mid-substance ACL rupture, 28% partial ACL tear and 56% concurrent medial meniscal damage. ACL reconstruction effectively restored joint stability by reducing joint laxity to a level similar to that in the contralateral intact knee. Compared to their contralateral controls, reconstructed limbs showed osteoarthritic changes to the cartilage and subchondral bone as early as 1-month post-trauma. The degeneration progressed over time up to 6-month. Overall, the medial compartments had more tissue damage than their corresponding lateral counterparts. Damage patterns to the ACL, the frequency of observed concurrent meniscal injury, and reductions in cartilage integrity and health were consistent with clinical observations of human patients who undergo ACL injury and reconstruction. Thus, we believe the combined closed-joint injury and surgical repair lapine model of PTOA, being first-ever and clinically relevant, shows promise to evaluate well-targeted therapeutics and other interventions for this chronic disease.

Mechanical Evaluation of Two Hybrid Locking Plate Designs for Canine Pancarpal Arthrodesis.

Hybrid locking pancarpal arthrodesis plates were designed with either a round (RH) or an oval (OH) radiocarpal hole, the latter allowing varied screw positioning. Due to concerns about potential decreased structural properties of the OH design, our aim was to compare the mechanical behavior of the contrasting plates using combined finite element analysis (FEA) and mechanical testing. Pancarpal arthrodesis plates with RH or OH design were assigned to three fixation techniques (n = 6), prebent at 20°, and fixed to canine forelimb models with simulated radius and radiocarpal and 3rd metacarpal bones. OH plates were instrumented with a radiocarpal screw inserted either most proximal (OH-P) or most distal (OH-D). Specimens were axially loaded to 300 N over 10 ramped cycles at 0.5 Hz. Plate strains were measured with strain gauges placed at areas of highest deformations as predicted by FEA under identical loading conditions. FEA predicted the highest strains (µm/m) adjacent to the radiocarpal hole (2,500 [RH], 2,900 [OH-P/OH-D]) and plate bending point (2,250 [RH], 1,900 [OH-P/OH-D]). Experimentally, peak radiocarpal hole strains were not influenced by the OH screw position (3,329 ± 443 [OH-P], 3,222 ± 467 [OH-D]; P = 0.550) but were significantly higher compared to the RH design (2,123 ± 154; P < 0.001). Peak strains at the bending point were significantly lower for OH-P (1,792 ± 174) and OH-D (1,806 ± 194) versus RH configurations (2,158 ± 114) (P ≤ 0.006). OH plates demonstrated highest peak strains next to the radiocarpal hole and were associated with more heterogenous plate strain distribution. Structural weakening associated with radiocarpal OH plate design could result in decreased fixation strength and increased risk of plate fatigue failure.

Reconstruction of the cranial cruciate ligament using a semitendinosus autograft in a lapine model.

OBJECTIVE: To clarify and improve a cranial cruciate ligament (CrCL) deficient stifle stabilization technique using a semitendinosus tendon (ST) autograft fixed with an interference fit screw (IFS) in a closed-joint trauma lapine osteoarthritis (OA) model. STUDY DESIGN: Experimental OA model. ANIMALS: Forty-one Flemish Giant rabbits. METHODS: Following arthrotomy of traumatized lapine stifles, the ST insertion on the tibial plateau was exposed and the ST was transected near its origin. The graft was passed through tibial and femoral tunnels, manually tensioned and then secured in place with a custom IFS and periosteal sutures. Drawer was manually assessed during and immediately after surgery intraoperatively. Upon euthanasia, joint laxity was measured at 2, 10, or 22 weeks postoperatively and compared to that of the contralateral, intact stifles and stifles with a surgically transected CrCL. RESULTS: Minimal postoperative drawer was present in 34% of the rabbits and potentially correlated with meniscal injury and subsequent meniscectomy. CrCL reconstruction significantly reduced joint laxity to a level (3.6 ± 1.6 mm) similar to that (2.7 ± 0.8 mm) in contralateral intact stifles. CONCLUSION: Surgical replacement of a traumatically injured CrCL using a ST autograft fixed with an IFS replicated a common human surgical technique and effectively restored joint stability in the short, medium, and long terms of the study. CLINICAL SIGNIFICANCE: The study provides researchers a useful, clinically relevant, post-traumatic CrCL deficient rabbit model for the study of OA and investigations of interventions to mitigate or prevent long-term joint degeneration.

Canine Elbow Dysplasia: Medial Compartment Disease and Osteoarthritis.

Erosion of the articular cartilage of the medial compartment of the elbow (the humeroulnar articulation) secondary to incongruency associated with elbow dysplasia or traumatic injury has been termed, medial compartment disease. When nonsurgical strategies to manage osteoarthritis (OA) fail, surgical solutions may be warranted. Surgical strategies reduce pain through off-loading of the medial compartment by load-shifting osteotomies of the humerus or ulna. Other strategies involve replacement of portions or all of the articular surface of the medial compartment. With global elbow joint OA (medial and lateral compartment), a total elbow replacement may be required.

Clinical application of the small I-Loc interlocking nail in 30 feline fractures: A prospective study.

OBJECTIVE: To describe medium-term functional outcome after nail osteosynthesis in feline traumatology and report clinically relevant recommendations for I-Loc angle-stable interlocking nail use in cats. STUDY DESIGN: Prospective clinical study. SAMPLE POPULATION: Client-owned cats (n = 29). METHODS: Consecutive cases with femoral, tibial, or humeral fractures were included. Outcome measures included fracture and surgical procedure description, limb alignment, nail size vs body weight (BW), percentage of nail medullary canal (MC) fill, time to limb function at clinical union (CU), and complications. Descriptive statistics were reported and compared with historical data. RESULTS: Bone distribution was 53.3% femora, 30% tibiae, and 16.7% humeri. There were six epimetaphyseal and 24 diaphyseal fractures. Overall, 67% of fractures were comminuted. Open reduction and minimally invasive techniques were used in 73% and 27% of cases, respectively. Seventeen I-Loc 3 (cat mean BW 4.4 ± 2.2 kg) and 13 I-Loc 4 (cat mean BW 5.2 ± 1.2 kg) nails were placed with mean MC fill of ≤50%. Average time to CU was 7.2 weeks. At CU, lameness had resolved or was mild in every cat, and all cats ultimately regained full limb function. No major complications were encountered. CONCLUSION: Because of improved CU times, excellent functional outcomes, and low complication rate, our results provide evidence that I-Loc nails are safe and effective for feline traumatology. CLINICAL SIGNIFICANCE: The I-Loc may be advantageous for fixation of epimetaphyseal fractures. Because of feline bone specific dimensional constraints, I-Loc 3 is likely appropriate for all feline humeri and most tibiae, while I-Loc 4 is well sized for feline femora.

Evaluation of a Feline Bone Surrogate and In Vitro Mechanical Comparison of Small Interlocking Nail Systems in Mediolateral Bending.

OBJECTIVE: The aim of this study was to (1) evaluate bending structural properties of a machined short fibre epoxy (SFE) feline bone surrogate (FBS), (2) compare the bending behaviour of small angle-stable interlocking nails (I-Loc; Targon) and locking compression plates (LCP) and (3) evaluate the effect of implant removal on FBS bending strength. METHODS: Part 1: Feline cadaveric femurs (n = 10) and FBS (n = 4) underwent cyclic four-point bending and load to failure. Part 2: Fracture gap FBS constructs (n = 4/group) were stabilized in a bridging fashion with either I-Loc 3 and 4, Targon 2.5 and 3.0, LCP 2.0 and 2.4, then cyclically bent. Part 3: Intact FBS with pilot holes, simulating explantation, (n = 4/group) underwent destructive bending tests. Bending compliance, angular deformation and failure moment (FM) were statistically compared (p < 0.05). RESULTS: Native bone and FBS were similar for all outcome measures (p > 0.05). The smallest and largest bending compliance and angular deformation were seen in the I-Loc 4 and LCP 2.0 respectively (p < 0.05). While explanted Targon FBS had the lowest FM (p < 0.05), I-Loc and LCP constructs FM were not different (p > 0.05). CONCLUSION: The similar bending properties of short fibre epoxy made FBS and native feline femurs suggest that this model could be used for mechanical testing of implants designed for feline long bone osteosynthesis. The I-Loc constructs smaller angular deformation which also suggests that these implants represent a valid alternative to size-matched Targon and LCP for feline fracture osteosynthesis. The significantly lower FM of explanted Targon may increase the risk of secondary fracture following implant removal.

Mechanical comparison of two small interlocking nails in torsion using a feline bone surrogate.

OBJECTIVE: To compare the torsional behavior of two small angle-stable interlocking nails (I-Loc and Targon) with that of locking compression plates (LCP). To evaluate the effect of implant removal on the torsional strength of feline bone surrogates. STUDY DESIGN: Experimental. SAMPLE POPULATION: Fracture gap constructs and intact explanted bone surrogates. METHODS: Fracture gap constructs were stabilized with one of six implants (I-Loc 3 and 4, Targon 2.5 and 3.0, LCP 2.0 and 2.4) and then cyclically tested in torsion (n = 4/group). To simulate implant removal, intact surrogates with implant-specific pilot holes were then twisted to failure (n = 4/group). Torsional compliance (TC; °/Nm), angular deformation (AD; °), and failure torque (FT ; Nm) were statistically compared (P < .05). RESULTS: The I-Loc 4 had the smallest TC and AD of all constructs (P < .05). The largest TC (P < .05) was seen with the LCP 2.0. The Targon 2.5 had the largest AD (P < .05) secondary to locking interface slippage. Targon surrogates FT were the lowest of all groups (P < .05). Conversely, there was no difference between the FT of the I-Loc, LCP, and intact surrogates (P > .05). CONCLUSION: We showed that I-Loc nails provided greater torsional stability than size-matched Targon nails and LCPs. Conversely, Targon 2.5 locking interface slippage may jeopardize that construct's stability. Furthermore, the significantly reduced bone surrogate torsional strength provided evidence that the large Targon bolt holes increased the risk of postexplantation iatrogenic fracture. CLINICAL SIGNIFICANCE: Our results provide evidence to conclude that the small I-Loc nails may be valid alternatives to other osteosynthesis options for feline fracture repair.

Interlocking Nails and Minimally Invasive Osteosynthesis.

Reviews of clinical outcomes led to the foundation of a new approach in fracture management known as biological osteosynthesis. As intramedullary rods featuring cannulations and locking devices at both extremities, interlocking nails are well suited for bridging osteosynthesis. Unique biological and mechanical benefits make them ideal for minimally invasive nail osteosynthesis and an attractive, effective alternative to plating, particularly in revisions of failed plate osteosynthesis. Thanks to a new angle-stable locking design, interlocking nailing indications have been expanded to osteosynthesis of epi-metaphyseal fractures, including those with articular involvement and angular deformities such as distal femoral varus and associated patellar luxations.

Minimally invasive percutaneous medial plate rod osteosynthesis for treatment of bicondylar humeral fractures in dogs: Surgical technique and case report.

OBJECTIVE: To describe a minimally invasive surgical technique for the treatment of comminuted humeral bicondylar (also known as T-Y) fractures in dogs and report outcome in 3 cases. STUDY DESIGN: Surgical technique description and case report. ANIMALS: Three consecutive dogs with traumatic comminuted humeral T-Y fractures. METHODS: Dogs that presented with a traumatic humeral T-Y fracture were prospectively included. The condylar component of the fractures was reduced first by using a combination of percutaneous forceps and K-wires. A transcondylar screw was applied, and epicondylar pins were preplaced medially and laterally. The metaphyseal component of the fracture was then reduced and stabilized with the pins. Finally, a bone plate was applied percutaneously along the medial humeral surface. Intraoperative fluoroscopy was used throughout surgery in all cases. Postoperative alignment in the frontal and sagittal planes was compared to the contralateral limbs. Time to clinical union, clinical outcome, and complications were recorded. RESULTS: Three dogs were included. Body weight ranged from 5.9 to 40 kg. Incomplete ossification of the humeral condyle was identified as the primary pathology leading to the fracture in 2 cases. All cases experienced uncomplicated healing with good to excellent functional recovery. CONCLUSION: The reported technique was associated with good outcomes without complications in 3 cases. CLINICAL SIGNIFICANCE: This study provides evidence that minimally invasive plate osteosynthesis represents an alternative to open reduction and internal fixation in the treatment of comminuted humeral T-Y fractures.

Tibial fracture repair with angle-stable interlocking nailing in 2 calves.

OBJECTIVE: To report tibial fracture repairs with I-Loc angle-stable interlocking nails (AS-ILN) in 2 calves. STUDY DESIGN: Clinical case reports. ANIMALS: One 5-day-old Holstein calf and one 3-month-old beefalo calf. METHODS: In a 50-kg Holstein calf, a proximal juxtametaphyseal comminuted tibial fracture with tibial tuberosity slab fracture was repaired with an 8-160-mm I-Loc nail and 2 cortical lag screws. In an 89-kg beefalo calf, a long oblique middiaphyseal tibial fracture was repaired with an 8-185-mm I-Loc nail and 5 double loop cerclage wires. In each case, an I-Loc AS-ILN was selected because unique biomechanical challenges precluded treatment with traditional osteosynthesis methods, such as external coaptation or plate fixation. RESULTS: No complications were diagnosed, and clinical union was documented 4 weeks after surgery in both cases. Axial growth continued in both calves, with no evidence of angular limb deformity at 7- and 6-month follow-up. CONCLUSION: This is the first report describing the use of the I-Loc nail in a bovine species. This application led to uncomplicated healing of tibial fractures and continued growth in both young calves described here. CLINICAL SIGNIFICANCE: Interlocking nailing may provide an effective and safe alternative for osteosynthesis of tibial fractures in young calves. Insertion of the AS-ILN across the center of the proximal tibial physis of a rapidly growing calf does not seem to alter its growth potential.

Characterization of the torsional structural properties of feline femurs and surrogate bone models for mechanical testing of orthopedic implants.

OBJECTIVE: To characterize the torsional structural properties of the feline femur and design a bone model surrogate for mechanical testing of feline orthopedic implants. STUDY DESIGN: Experimental. SAMPLE POPULATION: Paired feline femurs (n = 30) and bone models (8 materials, n = 4/group). METHODS: Femurs were cyclically tested nondestructively in torsion and then loaded to failure. A generic femoral model was then designed from native femur dimensions and tested similarly by using 1 of 8 materials that were 3-dimensionally printed or machined. Outcome measures consisting of torsional compliance, angular deformation (AD), and torque to failure were compared by using Student's t test (P < .05). Failure modes are reported as descriptive statistics. RESULTS: Torsional compliance (1.6 ± 0.3°/Nm, 2.0 ± 0.1°/Nm), AD (3.1 ± 0.6°, 3.8 ± 0.2°) and torque to failure (7.8 ±1.2 Nm, 8.1 ± 1.3 Nm) did not differ between feline femurs and short-fiber epoxy (SFE) models. Conversely, most printed materials displayed excessive TC and failed by plastic deformation (AD > 15-fold that of native femurs) rather than by fracture. Feline bone and SFE both failed by spiral fractures. CONCLUSION: None of the outcome measures differed between the 4th generation SFE model and cadaveric femurs, but differences were identified between feline bone and printed materials. CLINICAL IMPACT: Machined SFE can be used to create a surrogate bone model with torsional structural properties similar to those of feline femurs. In contrast, common printable materials appear unsuitable to produce a realistic feline bone surrogate.

Minimally invasive percutaneous medial plate-rod osteosynthesis for treatment of humeral shaft fractures in dog and cats: Surgical technique and prospective evaluation.

OBJECTIVE: To describe and prospectively report outcomes associated with a novel minimally invasive percutaneous osteosynthesis (MIPO) technique for the treatment of humeral fractures in dogs and cats. STUDY DESIGN: Prospective clinical case series. ANIMALS: Eleven dogs and 4 cats with traumatic nonarticular humeral fractures. METHODS: Dogs and cats that presented with traumatic humeral fractures were enrolled in the study. After closed reduction, the fracture was stabilized by using a plate-rod combination applied via remote medial incisions. Postoperative alignment in the frontal and sagittal planes was statistically compared with the contralateral limbs. Time to clinical union and complications were also recorded. RESULTS: Eleven dogs and 4 cats were included in this study. Body weight ranged from 4.5 to 33.6 kg in dogs and from 2.2 to 3.6 kg in cats. A veterinary cuttable plate (6/11 dogs and 3/4 cats) or locking compression plate was used in a plate-rod configuration (11/11 dogs and 2/4 cats) or alone (2/4 cats). Rod-to-medullary-cavity ratio was 30%. Plate-span ratio was 5.8 (range, 2-13.5). No significant differences were found in frontal or sagittal plane alignment. Healing time in cases that completed on-time follow-up (12/15) was 36 ± 14 days (range, 20-69). No major complications were recorded. CONCLUSION: The reported technique was associated with good outcomes in a large variety of fracture configurations and animal sizes, with no complications. CLINICAL SIGNIFICANCE: This report provides evidence that MIPO is a compelling alternative to open reduction and internal fixation in the treatment of various humeral fractures.