Biomechanical evaluation of interlocking nail and locking compression plating for stabilization of ovine critical-sized segmental tibia defects.

Background: Segmental large volume bone loss resulting from fracture or osseous neoplasia is a major challenge to orthopedic surgeons and there is an ongoing quest to identify treatments that optimize healing. To advance treatment, large animal translational models-such as the ovine critical-sized tibia defect model-are instrumental for testing of novel scaffolds for bone regeneration. However, little standardization in the implants utilized for defect stabilization has been determined and current commercially available implants may be inadequate to replicate the strength of the native tibia. We hypothesize that a 10-mm interlocking nail (ILN) would be stiffer in axial, bending, and torsional loading than its 8-mm counterpart and would be stiffer in axial and torsional loading compared to a 4.5-mm broad locking compression plate (LCP). Methods: Tibias were harvested from 24 ovine hind limbs from skeletally mature ewes euthanized for reasons unrelated to this study and were randomized to treatment group. An ex vivo comparison of a novel 10-mm angle-stable non-tapered ILN was compared to a commercially available 8-mm angle-stable tapered ILN and a broad LCP in an ovine critical-sized (5-cm) tibia defect model. Axial stiffness, torsional stiffness, and bending stiffness were determined in control intact tibia and tibial constructs in the three treatment groups. Following implantation, radiography was performed in all limbs and tibia length and cortical and medullary cavity diameter were measured. Comparisons between groups were assessed with a one-way analysis of variance. Significance was set at P<0.05. Results: The 10-mm ILN in tibia containing a 5-cm ostectomy gap most closely replicated the structural properties of intact tibia compared with other constructs. The 10-mm ILN had significantly stronger torsional (P<0.001) and bending (P=0.002) stiffness than the 8-mm ILN, and was significantly stronger than the LCP in axial (P=0.04) and torsional (P=0.01) stiffness. Conclusions: A 10-mm ILN used to stabilize an ovine critically-sized tibia defect most closely mimicked the structural properties of the intact tibia when compared to a 8-mm ILN or broad LCP. Further in vivo testing will aid in determining which stabilization method is best suited for testing of novel tissue engineering and bone healing studies.

Enhanced bone formation in locally-optimised, low-stiffness additive manufactured titanium implants: An in silico and in vivo tibial advancement study.

A tibial tuberosity advancement (TTA), used to treat lameness in the canine stifle, provides a framework to investigate implant performance within an uneven loading environment due to the dominating patellar tendon. The purpose of this study was to reassess how we design orthopaedic implants in a load-bearing model to investigate potential for improved osseointegration capacity of fully-scaffolded mechanically-matched additive manufactured (AM) implants. While the mechanobiological nature of bone is well known, we have identified a lower limit in the literature where investigation into exceedingly soft scaffolds relative to trabecular bone ceases due to the trade-off in mechanical strength. We developed a finite element model of the sheep stifle to assess the stresses and strains of homogeneous and locally-optimised TTA implant designs. Using additive manufacturing, we printed three different low-stiffness Ti-6Al-4 V TTA implants: 0.8 GPa (Ti1), 0.6 GPa (Ti2) and an optimised design with a 0.3 GPa cortex and 0.1 GPa centre (Ti3), for implantation in a 12-week in vivo ovine pilot study. Static histomorphometry demonstrated uniform bone ingrowth in optimised low-modulus Ti3 samples compared to homogeneous designs (Ti1 and Ti2), and greater bone-implant contact. Mineralising surfaces were apparent in all implants, though mineral apposition rate was only consistent throughout Ti3. The greatest bone formation scores were seen in Ti3, followed by Ti2 and Ti1. Results from our study suggest lower stiffnesses and higher strain ranges improve early bone formation, and that by accounting for loading environments through rational design, implants can be optimised to improve uniform osseointegration. STATEMENT OF SIGNIFICANCE: The effect of different strain ranges on bone healing has been traditionally investigated and characterised through computational models, with much of the literature suggesting higher strain ranges being favourable. However, little has been done to incorporate strain-optimisation into porous orthopaedic implants due to the trade-off in mechanical strength required to induce these microenvironments. In this study, we used finite element analysis to optimise the design of additive manufactured (AM) titanium orthopaedic implants for different strain ranges, using a clinically-relevant surgical model. Our research suggests that there is potential for locally-optimised AM scaffolds in the use of orthopaedic devices to induce higher strains, which in turn encourages de novo bone formation and uniform osseointegration.

The Effect of Anterior Cruciate Ligament Reconstruction with an Electropsun Scaffold on Tibiofemoral Contact Mechanics.

Surgical reconstruction of the torn ACL is performed to restore native contact mechanics. Drawbacks to traditional ACL repair techniques motivate the development of a tissue engineered ACL scaffold. Our group has developed a hierarchical electrospun polycaprolactone (PCL) scaffold that consists of rolled nanofiber bundles attached at each end with solvent-case blocks of PCL. The goal of this study was to compare ovine cadaver tibiofemoral contact mechanics after ACL reconstruction with the electrospun scaffold to a clinically applicable ACL reconstruction with a soft tissue graft and the ACL transected condition (ACLX). In the ACLX group and after ACL reconstruction with either the electrospun scaffold or soft tissue graft, pressure sensors were inserted under the menisci. Loads up to 890 N were applied at various flexion angles. The scaffold performed the best at restoring contact mechanics in the medial hemijoint to that of the native ACL. The scaffold was good at maintaining a medial-lateral balance of pressures as in the native joint whereas the ACLX shifted pressure off the lateral and on to the medial hemijoint. While the ACL scaffold didn't restore mechanics to that of the native condition, it improved contact mechanics compared to the standard graft replacement and ACLX condition.

Ventral femoral head and neck ostectomy: Standard versus novel K-wire guided technique using a premeasured ostectomy angle in canine cadavers.

OBJECTIVE: To assess the accuracy and efficiency of performing ventral FHO (vFHO) after measuring the ideal femoral head and neck ostectomy angle (iFHOA), with and without guidance of a K-wire. To compare the iFHOA to the previously accepted 45° angle to guide vFHOs. STUDY DESIGN: Randomized, controlled, ex vivo study. ANIMALS: Ten mixed-breed canine cadavers. METHODS: A routine un-guided and guided vFHO was performed on each cadaver. A single unmodified ostectomy was performed on all hips. The pre- and postoperative iFHOA and postoperative residual femoral neck were radiographically assessed. Subjective intraoperative palpation and postoperative radiographic ostectomy completeness (OC) scores were assigned. RESULTS: Subjective OC scores (p > .63) did not differ between techniques, and guided vFHOs were as good or better for 7/10 dogs assessed via intraoperative palpation, and 9/10 dogs assessed radiographically. Residual femoral neck measurements were similar in both groups (p > .75). The average iFHOA in this study was 38.5°, with no significant difference between limbs of the same cadaver (p = .34). Guided vFHO took longer (294.5 s, p = .002) than unguided vFHO (166.7 s). CONCLUSION: The mean iFHOA of 38.5° was less than the previously published 45° angulation for vFHOs. Subjectively, use of a K-wire guide improved soft tissue retraction, neck visualization, and confidence in cut angulation. CLINICAL SIGNIFICANCE: Preoperative iFHOA measurement may minimize the risk of inappropriate vFHO angles.

Investigation of a Prevascularized Bone Graft for Large Defects in the Ovine Tibia.

In vivo bioreactors are a promising approach for engineering vascularized autologous bone grafts to repair large bone defects. In this pilot parametric study, we first developed a three-dimensional (3D) printed scaffold uniquely designed to accommodate inclusion of a vascular bundle and facilitate growth factor delivery for accelerated vascular invasion and ectopic bone formation. Second, we established a new sheep deep circumflex iliac artery (DCIA) model as an in vivo bioreactor for engineering a vascularized bone graft and evaluated the effect of implantation duration on ectopic bone formation. Third, after 8 weeks of implantation around the DCIA, we transplanted the prevascularized bone graft to a 5 cm segmental bone defect in the sheep tibia, using the custom 3D printed bone morphogenic protein 2 (BMP-2) loaded scaffold without prior in vivo bioreactor maturation as a control. Analysis by micro-computed tomography and histomorphometry found ectopic bone formation in BMP-2 loaded scaffolds implanted for 8 and 12 weeks in the iliac pouch, with greater bone formation occurring after 12 weeks. Grafts transplanted to the tibial defect supported bone growth, mainly on the periphery of the graft, but greater bone growth and less soft tissue invasion was observed in the avascular BMP-2 loaded scaffold implanted directly into the tibia without prior in vivo maturation. Histopathological evaluation noted considerably greater vascularity in the bone grafts that underwent in vivo maturation with an inserted vascular bundle compared with the avascular BMP-2 loaded graft. Our findings indicate that the use of an initial DCIA in vivo bioreactor maturation step is a promising approach to developing vascularized autologous bone grafts, although scaffolds with greater osteoinductivity should be further studied. Impact statement This translational pilot study aims at combining a tissue engineering scaffold strategy, in vivo prevascularization, and a modified transplantation technique to accelerate large segmental bone defect repair. First, we three-dimensional (3D) printed a 5 cm scaffold with a unique design to facilitate vascular bundle inclusion and osteoinductive growth factor delivery. Second, we established a new sheep deep circumflex iliac artery model as an in vivo bioreactor for prevascularizing the novel 3D printed osteoinductive scaffold. Subsequently, we transplanted the prevascularized bone graft to a clinically relevant 5 cm segmental bone defect in the sheep tibia for bone regeneration.

Osteoinductive 3D printed scaffold healed 5 cm segmental bone defects in the ovine metatarsus.

Autologous bone grafts are considered the gold standard grafting material for the treatment of nonunion, but in very large bone defects, traditional autograft alone is insufficient to induce repair. Recombinant human bone morphogenetic protein 2 (rhBMP-2) can stimulate bone regeneration and enhance the healing efficacy of bone grafts. The delivery of rhBMP-2 may even enable engineered synthetic scaffolds to be used in place of autologous bone grafts for the treatment of critical size defects, eliminating risks associated with autologous tissue harvest. We here demonstrate that an osteoinductive scaffold, fabricated by combining a 3D printed rigid polymer/ceramic composite scaffold with an rhBMP-2-eluting collagen sponge can treat extremely large-scale segmental defects in a pilot feasibility study using a new sheep metatarsus fracture model stabilized with an intramedullary nail. Bone regeneration after 24 weeks was evaluated by micro-computed tomography, mechanical testing, and histological characterization. Load-bearing cortical bridging was achieved in all animals, with increased bone volume observed in sheep that received osteoinductive scaffolds compared to sheep that received an rhBMP-2-eluting collagen sponge alone.

An assessment of mechanical properties and screw push-out for two 3.5-mm pearl-type locking plate systems.

OBJECTIVE: To compare mechanical properties (stiffness, yield load, failure load, and deformation at failure) of 2 pearl-type locking plate system (PLS) constructs (PLS 1 and PLS 2) in a simulated fracture gap model and to compare screw push-out forces of the 2 PLSs with and without plate contouring. SAMPLE: 40 PLS constructs. PROCEDURES: Mechanical properties of uncontoured PLS 1 (n = 8) and PLS 2 (8) constructs were evaluated in synthetic bone-plate models under axial compression. Screw push-out forces were evaluated in 6 uncontoured and 6 contoured PLSs of each type. Variables of interest were compared between PLS groups and between contoured and uncontoured plates by statistical methods. RESULTS: Yield and failure loads were higher in the PLS 1 group than in the PLS 2 group, but stiffness did not differ significantly between groups. All constructs failed by plate bending, with greater deformation in the PLS 2 group. Push-out force to screw-plate uncoupling was higher in the PLS 2 group than in the PLS 1 group for uncontoured and contoured plates. Locking mechanism failure of PLS 1 specimens was through screw-thread stripping. The PLS 2 specimens failed by node deformation followed by screwhead stripping. CONCLUSIONS AND CLINICAL RELEVANCE: Distinct mechanical differences were identified between the 2 PLSs. The clinical relevance of these differences is unknown. Further research including cyclic fatigue testing is needed to reveal more clinically pertinent information.

Gait and electromyographic alterations due to early onset of injury and eventual rupture of the cranial cruciate ligament in dogs: A pilot study.

OBJECTIVE: Identify relevant electromyography (EMG), kinematic, and kinetic changes resulting from monopolar radiofrequency energy (MRFE)-induced cranial cruciate ligament (CCL) injury and eventual rupture in dogs. STUDY DESIGN: Experimental, repeated measures. ANIMALS: Five purpose-bred female dogs free of orthopedic and neurologic disease. METHODS: Surface EMG, joint kinematics, and ground reaction forces were assessed at a trot in the pelvic limbs at baseline, at 2 and 4 weeks after unilateral MRFE-induced CCL injury, and at 4, 8, and 16 weeks after CCL rupture (CCLR). RESULTS: After MRFE-induced injury, average hip joint range of motion (ROM) during stance decreased within the untreated pelvic limb. After CCLR, stifle flexion angles decreased within the treated limb at 8 weeks and within the untreated pelvic limb at all time points, whereas average tarsal joint ROM decreased in the treated limb and increased in the untreated limb. Peak vertical ground reaction force and impulse decreased within the treated limb. Qualitative alterations of many EMG values were noted after MRFE-induced injury and CCLR, although significant differences between limbs or from baseline values were not detected. CONCLUSION: Monopolar radiofrequency energy-induced injury altered contralateral hip kinematics, suggesting early regional compensatory gait alterations. After CCLR, additional compensatory gait patterns occurred in both pelvic limbs. CLINICAL IMPACT: The qualitative analysis of trial-averaged EMG data in this small population supports a relationship between neuromuscular function and induced CCL injury leading to rupture.

Postamputation Orthopedic Surgery in Canine Amputees: Owner Satisfaction and Outcome.

Surgical management of postamputation orthopedic disease (PAOD) in canine amputees has rarely been documented, and no reports describing outcome of stifle surgery in canine amputees are available. The objective of this multisite retrospective case series was to describe cases and evaluate satisfaction with and outcome of postamputation orthopedic surgery in canine amputees. Data was obtained through medical records and owner survey responses; data included signalment, amputation cause, diagnosis, surgical treatment, timeframes, and outcome assessment. Outcome was categorized as acceptable or unacceptable, and complications were classified as catastrophic, major, or minor. Eleven thoracic limb amputees and 6 pelvic limb amputees with surgically treated PAOD were identified. Surgically treated PAOD was reported at a median of 9.7 months (range 0.5-110 months) after amputation. All 17 amputees were treated for pelvic limb disease, predominantly for cranial cruciate ligament disease that occurred in 11 of 17 dogs. Major complications following orthopedic surgeries performed in 3 thoracic limb amputees consisted of infection (n = 2) and uncontrolled pain (n = 1). No major complications were reported following orthopedic surgeries performed in pelvic limb amputees. Acceptable mid-to-long-term outcome was achieved in 16 of the 17 canine amputees. Surgical treatment of pelvic limb disease did not appear to be associated with a high number of major complications in this case series. These findings suggest that orthopedic surgery, specifically stifle surgery, in canine amputees might be considered a feasible treatment option. Although there are inherent methodological limitations of retrospective studies and owner surveys, our case series provides new information that might help guide surgical treatment decisions in canine amputees suffering from orthopedic disease. Prospective studies using objective outcome measures evaluating surgical management of PAOD are necessary to confirm the provided information.

An investigation of shock wave therapy and low-intensity pulsed ultrasound on fracture healing under reduced loading conditions in an ovine model.

The use of shock wave therapy (SWT) and low-intensity pulsed ultrasound (LIPUS) as countermeasures to the inhibited fracture healing experienced during mechanical unloading was investigated by administering treatment to the fracture sites of mature, female, Rambouillet Columbian ewes exposed to partial mechanical unloading or full gravitational loading. The amount of fracture healing experienced by the treatment groups was compared to controls in which identical surgical and testing protocols were administered except for SWT or LIPUS treatment. All groups were euthanized after a 28-day healing period. In vivo mechanical measurements demonstrated no significant alteration in fixation plate strains between treatments within either partial unloading group. Similarly, DXA BMD and 4-point bending stiffness were not significantly altered following either treatment. µCT analyses demonstrated lower callus bone volume for treated animals (SWT and LIPUS, p < 0.01) in the full gravity group but not between reduced loading groups. Callus osteoblast numbers as well as mineralized surface and bone formation rate were significantly elevated to the level of the full gravity groups in the reduced loading groups following both SWT and LIPUS. Although no increase in 4-week mechanical strength was observed, it is possible that an increase in the overall rate of fracture healing (i.e., callus strength) may be experienced at longer time points under partial loading conditions given the increase in osteoblast numbers and bone formation parameters following SWT and LIPUS. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:921-929, 2018.

The effect of polydioxanone hemicerclage suture on the occurrence of fracture during tibial tuberosity advancement with an elongated bi-directional hinged osteotomy.

OBJECTIVE: To investigate the effect of hemicerclage suture on the occurrence of fractures during advancement of an elongated bi-directional hinged osteotomy (EBHO) for tibial tuberosity advancement (TTA) in dogs. STUDY DESIGN: Experimental ex vivo study. ANIMALS: Canine cadavers (n = 14) METHODS: A uniform EBHO was performed in 28 cadaveric hind limbs (n = 28) from 14 skeletally mature, medium-sized, mixed breed dogs. Paired limbs were randomly assigned with or without hemicerclage suture. The osteotomy was slowly spread (TTA) at a rate 1.5 mm every 15 seconds to a maximum distance of 24 mm or until a fracture was detected as an audible crack, visible propagation of the distal osteotomy or transverse fracture of the cortical bridge. The occurrence of fractures was compared between limbs with hemicerclage and without hemicerclage (control) suture using a chi-square analysis. The advancement distance at the time of fracture was compared using a paired t test. A P value <.05 was considered significant. RESULTS: The cumulative occurrence of intraoperative fracture was significantly greater without hemicerclage than with hemicerclage at advancements of 12, 15, 18, and 24 mm. The mean (SD) spreading distance at the time of fracture was significantly less without hemicerclage at 16.85 (4.10) mm with a range of 12-24 mm, than with hemicerclage at 20.62 (2.39) mm with a range of 18-24 mm (P = .029). CONCLUSION: The occurrence of immediate intraoperative fracture during advancement of an EBHO of the tibial tuberosity is less when a hemicerclage suture is placed.

Comparison of owner satisfaction between stifle joint orthoses and tibial plateau leveling osteotomy for the management of cranial cruciate ligament disease in dogs.

OBJECTIVE To compare owner satisfaction between custom-made stifle joint orthoses and tibial plateau leveling osteotomy (TPLO) for the management of medium- and large-breed dogs with cranial cruciate ligament disease (CCLD). DESIGN Owner survey. SAMPLE 819 and 203 owners of dogs with CCLD that were managed with a custom-made stifle joint orthosis or TPLO, respectively. PROCEDURES Client databases of an orthosis provider and veterinary teaching hospital were reviewed to identify potential survey respondents. An online survey was developed to evaluate owner-reported outcomes, complications, and satisfaction associated with the nonsurgical (orthosis group) and surgical (TPLO group) interventions. Survey responses were compared between groups. RESULTS The response rate was 25% (203/819) and 37% (76/203) for the orthosis and TPLO groups, respectively. The proportion of owners who reported that their dogs had mild or no lameness and rated the intervention as excellent, very good, or good was significantly greater for the TPLO group than for the orthosis group. However, ≥ 85% of respondents in both groups reported that they would choose the selected treatment again. Of 151 respondents from the orthosis group, 70 (46%) reported skin lesions associated with the device, 16 (11%) reported that the dog subsequently underwent surgery, and 10 (7%) reported that the dog never tolerated the device. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated high owner satisfaction rates for both interventions. Owners considering nonsurgical management with an orthosis should be advised about potential complications such as persistent lameness, skin lesions, patient intolerance of the device, and the need for subsequent surgery.

Hemiepiphysiodesis for the correction of proximal tibial valgus in growing dogs.

OBJECTIVES: To describe the use of hemiepiphysiodesis for the treatment of proximal tibial deformities in immature dogs and evaluate the effect on the mechanical medial proximal tibial angle (mMPTA). METHODS: Skeletally immature dogs with proximal tibial deformities from three institutions treated with hemiepiphysiodesis between March 2006 and January 2015 were included. All dogs were required to have an mMPTA outside the previously published reference range (93.3 ± 1.78°) preoperatively. Dogs were required to have radiographs or computed tomography performed preoperatively and at least eight weeks postoperatively. RESULTS: A total of 19 dogs (n = 31 limbs) fulfilled the inclusion criteria. The mean mMPTA was 102.5° ± 5.3° preoperatively and 92.4° ± 7.2° at the final re-evaluation. The mean difference in mMPTA was -10 ± 5.1° (range, -1 to -19°; p <0.001). Overcorrection was observed in 16 limbs and mMPTA remained above the reference range in nine limbs. Rebound growth was observed in eight limbs where implant removal was performed. CLINICAL SIGNIFICANCE: Hemiepiphysiodesis for the treatment of proximal tibial valgus is a technique that allows for reduction in mMPTA and should be considered as an early treatment for immature animals that are presented with proximal tibial deformities. Serial radiographs to monitor for overcorrection should be performed. Implant removal should be considered if overcorrection occurs, taking into consideration that rebound growth may be observed.

Computational characterization of fracture healing under reduced gravity loading conditions.

The literature is deficient with regard to how the localized mechanical environment of skeletal tissue is altered during reduced gravitational loading and how these alterations affect fracture healing. Thus, a finite element model of the ovine hindlimb was created to characterize the local mechanical environment responsible for the inhibited fracture healing observed under experimental simulated hypogravity conditions. Following convergence and verification studies, hydrostatic pressure and strain within a diaphyseal fracture of the metatarsus were evaluated for models under both 1 and 0.25 g loading environments and compared to results of a related in vivo study. Results of the study suggest that reductions in hydrostatic pressure and strain of the healing fracture for animals exposed to reduced gravitational loading conditions contributed to an inhibited healing process, with animals exposed to the simulated hypogravity environment subsequently initiating an intramembranous bone formation process rather than the typical endochondral ossification healing process experienced by animals healing in a 1 g gravitational environment. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1206-1215, 2016.

Microsphere-based gradient implants for osteochondral regeneration: a long-term study in sheep.

BACKGROUND: The microfracture technique for cartilage repair has limited ability to regenerate hyaline cartilage. AIM: The current study made a direct comparison between microfracture and an osteochondral approach with microsphere-based gradient plugs. MATERIALS & METHODS: The PLGA-based scaffolds had opposing gradients of chondroitin sulfate and ß-tricalcium phosphate. A 1-year repair study in sheep was conducted. RESULTS: The repair tissues in the microfracture were mostly fibrous and had scattered fissures with degenerative changes. Cartilage regenerated with the gradient plugs had equal or superior mechanical properties; had lacunated cells and stable matrix as in hyaline cartilage. CONCLUSION: This first report of gradient scaffolds in a long-term, large animal, osteochondral defect demonstrated potential for equal or better cartilage repair than microfracture.

Implantable microelectromechanical sensors for diagnostic monitoring and post-surgical prediction of bone fracture healing.

The relationship between modern clinical diagnostic data, such as from radiographs or computed tomography, and the temporal biomechanical integrity of bone fracture healing has not been well-established. A diagnostic tool that could quantitatively describe the biomechanical stability of the fracture site in order to predict the course of healing would represent a paradigm shift in the way fracture healing is evaluated. This paper describes the development and evaluation of a wireless, biocompatible, implantable, microelectromechanical system (bioMEMS) sensor, and its implementation in a large animal (ovine) model, that utilized both normal and delayed healing variants. The in vivo data indicated that the bioMEMS sensor was capable of detecting statistically significant differences (p-value <0.04) between the two fracture healing groups as early as 21 days post-fracture. In addition, post-sacrifice micro-computed tomography, and histology data demonstrated that the two model variants represented significantly different fracture healing outcomes, providing explicit supporting evidence that the sensor has the ability to predict differential healing cascades. These data verify that the bioMEMS sensor can be used as a diagnostic tool for detecting the in vivo course of fracture healing in the acute post-treatment period.

Piezoelectric surgery -a novel technique for laminectomy.

OBJECTIVE: Piezoelectric surgery is a novel technology that allows for the osteotomy of mineralized tissue with less risk of damaging underlying soft tissue structures. This selective cutting increases the safety of osteotomies performed in close vicinity to delicate structures such as dura mater, blood vessels, and neural tissue. This study aimed to develop and describe the technique of piezoelectric surgery for dorsal laminectomy and to assess its clinical safety in normal sheep. METHODS: A piezoelectric, dorsal laminectomy technique was developed using ovine cadavers. Following technique development, six live sheep underwent a piezoelectric (n = 6) two-level dorsal laminectomy at L2-L3 and L4-L5 (PiezoL2-3,4-5), and another 30 live sheep underwent a three-level laminectomy at L1, L3, and L5 (PiezoL1,3,5) for a total of 102 laminectomy sites. Surgery time and postoperative complications were recorded. RESULTS: Dorsal laminectomy was safely and accurately performed in 35/36 study sheep using a Piezoelectric surgical instrument. No dural tears were noted in any animal. Non-ambulatory paraparesis in one study sheep (PiezoL1,3,5) led to euthanasia at 48 hr and only mild epidural hematoma was noted on necropsy. No other major postoperative complications were observed in any of the animals. Subjectively, PiezoL was easy to perform and with a rapid learning curve. Mean surgery time was 105 min (range: 75-165 min; median: 97.5) for PiezoL2-3,4-5 and 93 minutes (range 55-100 min; median: 67.5) for PiezoL1,3,5. CONCLUSIONS: Based on our study, PiezoL is considered a safe and viable technique for performing ovine dorsal laminectomy in the preclinical research setting.

Partial gravity unloading inhibits bone healing responses in a large animal model.

The reduction in mechanical loading associated with space travel results in dramatic decreases in the bone mineral density (BMD) and mechanical strength of skeletal tissue resulting in increased fracture risk during spaceflight missions. Previous rodent studies have highlighted distinct bone healing differences in animals in gravitational environments versus those during spaceflight. While these data have demonstrated that microgravity has deleterious effects on fracture healing, the direct translation of these results to human skeletal repair remains problematic due to substantial differences between rodent and human bone. Thus, the objective of this study was to investigate the effects of partial gravitational unloading on long-bone fracture healing in a previously-developed large animal Haversian bone model. In vivo measurements demonstrated significantly higher orthopedic plate strains (i.e. load burden) in the Partial Unloading (PU) Group as compared to the Full Loading (FL) Group following the 28-day healing period due to inhibited healing in the reduced loading environment. DEXA BMD in the metatarsus of the PU Group decreased 17.6% (p<0.01) at the time of the ostectomy surgery. Four-point bending stiffness of the PU Group was 4.4 times lower than that of the FL Group (p<0.01), while µCT and histomorphometry demonstrated reduced periosteal callus area (p<0.05), mineralizing surface (p<0.05), mineral apposition rate (p<0.001), bone formation rate (p<0.001), and periosteal/endosteal osteoblast numbers (p<0.001/p<0.01, respectively) as well as increased periosteal osteoclast number (p<0.05). These data provide strong evidence that the mechanical environment dramatically affects the fracture healing cascade, and likely has a negative impact on Haversian system healing during spaceflight.

Arthroscopic biceps ulnar release procedure (BURP): technique description and in vitro assessment of the association of visual control and surgeon experience to regional damage and tenotomy completeness.

OBJECTIVES: (1) Describe arthroscopic BURP surgical technique, (2) assess association of visual control and surgeon experience to tenotomy completeness and regional iatrogenic tissue damage. STUDY DESIGN: Cadaveric study. SAMPLE POPULATION: Canine cadavers weighing >20 kg (n = 16; 32 elbows). METHODS: Phase 1 = dissection/anatomic description/procedural refinement (n = 6). Phase 2 = technique description (n = 6). Phase 3 = association of surgeon experience and procedural visual control to tenotomy completion and regional iatrogenic damage (n = 20). Elbows were randomly assigned via coin toss to an experienced- or inexperienced-arthroscopist. Using conventional medial portals, surgeons sought to identify the medial collateral ligament (MCL) and ulnar insertion of the biceps tendon (uBT) before attempting complete tenotomy. Upon procedural completion, surgeons assigned a standardized "visual control score" (VCS) describing viewing that governed procedure and predicted % uBT release, MCL, and median nerve damage. Post-procedural dissection determined actual tenotomy completion and iatrogenic tissue damage. RESULTS: Complete BURP was achieved in 16 of 19 elbows. VCS was associated with tenotomy completeness (P < .01). "Blind" BURP was incomplete in both elbows in which it was attempted. Perception of complete BURP was associated with complete release (P < .01). MCL damage occurred in 10% of elbows. Surgeon experience did not influence VCS, regional damage, or BURP completeness. CONCLUSION: In canine cadavers, arthroscopic BURP can be consistently performed using conventional arthroscopic instruments and portals by both experienced and inexperienced arthroscopists when visual control guides the tenotomy into the distal aspect of the tendon.

In vitro incidence of fibular penetration with and without the use of a jig during tibial plateau leveling osteotomy.

OBJECTIVE: To determine the incidence of fibular penetration during placement of the Synthes® locking TPLO plate with and without the use of a jig. STUDY DESIGN: Cadaveric, experimental study. SAMPLE POPULATION: Cadaveric paired pelvic limbs (n = 8) from skeletally mature dogs. METHODS: Limbs were assigned to 1 of 2 groups (jig-less-TPLO = no jig used; jig-TPLO = jig used). Synthes® locking TPLO plates were applied using proximal screws of excessive length to facilitate identification of fibular penetration. Screw tip locations were identified by dissection and frequency of fibular penetration was compared between groups. RESULTS: None of the jig-TPLO limbs and 6 (75%) of jig-less-TPLO limbs had fibular penetration, a difference that was statistically significant. Fibular penetration was most frequently associated with the most proximal screw. CONCLUSIONS: A significantly higher incidence of fibular penetration occurs when Synthes® locking TPLO is performed without use of a jig.