Retrospective study of the early clinical experience with a precontoured angle-stable interlocking nail for fracture repair in dogs and cats

OBJECTIVE

To report indications, outcomes, and complications with a precontoured angle-stable interlocking nail (CAS-ILN).

ANIMALS

90 client-owned animals.

METHODS

Dogs and cats treated with the CAS-ILN between 2020 and 2022 were retrospectively reviewed. Collected data included body weight, fracture configuration, percentage of medullary canal filled, limb alignment, complications, and follow-up. Favorable outcomes were defined when full functional restoration was observed.

RESULTS

Thirty-eight dogs and 52 cats were included. Median body weight was 4.3 kg (range, 1.5 to 6.7 kg) for cats and 25 kg (range, 6.8 to 54 kg) for dogs. A total of 54 femurs, 31 tibias, and 5 humeri were treated, including 65 comminuted fractures and 26 metaphyseal fractures. The median percentage of medullary canal occupied by the nail was 76.5% (range, 53% to 97.6%). Radiographic postoperative bone alignment was good in 85.5% (59/69) and satisfactory in 10 cases. The median duration of follow-up (57/90) was 476 days (range, 56 to 1,057 days). In the perioperative period (0 to 12 weeks), lameness had resolved or was mild in all (51/52) but 1 case. In the long-term postoperative period (> 12 months), 97.1% (34/35) of cases showed restoration of full function and 1 case had an unacceptable function. An overall complication rate of 11.5% (7/61) was reported including 1 catastrophic and 6 major complications.

CLINICAL RELEVANCE

Long-term functional outcomes following the CAS-ILN were favorable in 97.1% (34/35) of cases. Complication rates were comparable to previous studies. The CAS-ILN appears to be an alternative surgical option for most long-bone fracture repairs.

Effect of the surface geometry of uncemented acetabular cups on primary stability in a model of uncemented total hip replacement in dogs

OBJECTIVE

To compare the in vitro stability of acetabular cups with peripherally reinforced fixation in a model of uncemented total hip replacement in dogs.

SAMPLE

63 polyurethane foam blocks and 3 acetabular implant designs: hemiellipsoidal (Model A) and 2 models with equatorial peripheral fins (Model B with 1 level and Model C with 2 levels of fins).

METHODS

2 loading patterns-edge loading and push-out tests-were performed until failure and peak forces were recorded. Implantation behavior was visually assessed and the required seating force was assessed using a force-displacement curve.

RESULTS

Model B showed significantly lower peak force than Model A in edge loading tests with standardized impaction. In the push-out test, Model A had a greater maximal force than Models B and C, with mean maximal forces of 213.7 N, 139.4 N, and 138.9 N, respectively. In the seating force test, Models B and C required a higher force for 2-mm deep implantation (362.0 N and 361.6 N, respectively) than Model A (194.4 N), and were associated with dorsal tilting of the components.

CLINICAL RELEVANCE

Our results suggest that cups with a peripheral design (B, C) have less primary stability than hemiellipsoidal cups (A). Furthermore, models with peripheral fins (B, C) appeared to have incomplete seating if a higher force was not used during implantation and, therefore, the risk of malpositioning was increased. These data indicate that hemiellipsoidal cups provide the same or better initial stability and require a lower impaction force.

Intra-articular replacement of the caudal cruciate ligament using a UHMWPE ligament under arthroscopic guidance in a dog: A case report

Background

As isolated ruptures of the caudal cruciate ligament (CdCL) are rare in dogs, there is no consensus on the indications and the gold-standard surgical technique for treatment.

Case Description

A 2-year-old Shepherd dog with an isolated rupture of the CdCL was treated with a new surgical technique for synthetic reconstruction. Three bone tunnels were drilled in the femur and the tibia under arthroscopic guidance to make sure the anatomical insertions of the physiological ligament were respected. An ultra-high molecular weight polyethylene (UHMWPE) implant was fixed with interference screws to reconstruct the CdCL. A synovial inflammation remained present on radiographs for 6 months after the surgery, together with a mild lameness. However, the dog fully recovered clinically and recovered a normal level of activity after 6 months. Liverpool osteoarthritis in dogs questionnaire results at 6 months and 1 year postoperatively were excellent.

Conclusion

The use of a UHMWPE implant fixed with interference screws to reconstruct the CdCL allowed a return to full function of the knee without complications, despite a persistent synovial inflammation and mild lameness for a 6-month period after the surgery. The success of this isolated surgical technique could lead to improvements in the surgical management of CdCL rupture, if these initial results are confirmed by a prospective study with a larger number of patients.

Ex-vivo biomechanical analysis of an original repair of canine calcaneal tendon rupture using a synthetic implant as mechanical support fixed by sutures in the proximal tendinous part and by an interference screw in the bone distal part

Background

Rupture of the common calcaneal tendon is the second most frequent tendon rupture in dogs and may lead to severe lameness and pain. Surgical repair consists of re-apposition of the damaged tendon ends using sutures, but this type of repair is not always possible especially if the tendon has retracted. Tendon augmentation with an ultra-high molecular weight polyethylene (UHMWPE) implant is a recent solution to support the sutures and allow the repair of the canine calcaneal tendon. However, its biomechanical fixation strength remains untested for this pathology.

Aim

To evaluate the biomechanical fixation strength of a UHMWPE implant for the repair of the canine calcaneal tendon.

Methods

Ex-vivo biomechanical study was carried out on eight cadaveric hindlimbs from four adult dogs. Hindlimbs were tested under two independent modalities: proximal tendinous fixation (PTF) and distal calcaneus fixation (DCF), using a testing machine. PTF was achieved by eight simple interrupted polypropylene sutures performed through the UHMWPE implant. The latter was sandwiched inside the gastrocnemius tendon, which had previously been incised over about 5 cm longitudinally, and through the tendon of the superficial digital flexor. DCF was performed using an interference screw, which locked the UHMWPE implant into a calcaneus tunnel drilled perpendicularly.

Results

Yield, failure load, and linear stiffness (mean ± SD) for the DCF modality were 920 ± 139 N, 1,007 ± 146 N, and 92 ± 15.21, respectively, which were greater than for the PTF modality (663 ± 92 N, 685 ± 84 N and 25.71 ± 5.74, respectively, p < 0.05). Failure modes were different between fixation modalities: for PTF it was suture breakage (n = 7/8), while for DCF it was implant damage and slippage (n = 8/8).

Conclusion

The biomechanical fixation strength of the UHMWPE implant was greater for DCF than that of PTF, and should be suitable for calcaneal tendon repair in dogs. The clinical prediction of rupture of this calcaneal tendon repair will occur at the level of the PTF.

Use of Ultrasonography in Diagnosis of Medial Compartment Disease of the Elbow in Dogs

OBJECTIVE

 The objective of this prospective study was to evaluate the use of ultrasonography in the diagnosis of medial coronoid process disease in unclear cases.

STUDY DESIGN

 Fifteen elbows (on thirteen dogs) for which radiography and computed tomography did not lead to a clear diagnosis of medial coronoid process disease were included. On each elbow, ultrasonography was performed with a high frequency linear transducer (12-18Hz). Then, arthroscopic examination of the joint was performed by a surgeon who was unaware of ultrasonographic findings to confirm medial coronoid process disease.

RESULTS

 At least one ultrasonographic lesion was detected in 13 out of 15 elbows. The main reported ultrasonographic lesions were joint effusion (10/15 elbows) and an abnormal shape of the medial coronoid process (irregular, ill-defined or fragmented) (9/15).

CONCLUSION

 Ultrasonography can be a helpful additional diagnostic tool to confirm medial coronoid process disease of the elbow joint before performing arthroscopy in unclear cases. Further studies will be needed to evaluate the use of higher frequency transducers and determine if it could improve the diagnostic value of ultrasonography.

Validation of a biomechanical testing protocol of craniodorsal hip luxation in feline cadavers and comparison of two ultra-high molecular weight polyethylene materials used for extra-articular hip stabilisation

OBJECTIVES

The aim of our study was to describe a biomechanical testing protocol to reproduce ex vivo craniodorsal hip luxation specific to the feline model, and evaluate the biomechanical properties of an intact hip joint compared with the fixation strength of two different techniques of extra-articular hip stabilisation.

METHODS

Eighteen hip joints (femur and hemipelvis) were harvested from nine mature feline cadavers. CT was performed for each hip joint so that a biomechanical base specific to each joint morphotype could be created using computer-aided design. The biomechanical bases were then produced using a three-dimensional printer to secure the hip joints during testing. A total of 34 biomechanical compression tests were performed. Eighteen compression tests were performed in the control group, of which two fractured. The remaining 16 hip joints were then randomly assigned either to group A (hip joints stabilised with an extra-articular ultra-high molecular weight polyethylene (UHMWPE) implant secured by an interference screw [n = 8]) or to group B (hip joints stabilised with a UHMWPE iliofemoral suture [n = 8]).

RESULTS

Mean ± SD yield, failure load and linear stiffness in the control group were 616 ± 168 N, 666 ± 158 N and 231 ± 50 N/mm, respectively. The relative fixation strength (% of intact joint) before hip luxation in groups A and B was 43.8% and 34.7%, respectively. No statistical difference was found between groups A and B for yield and failure load. However, the reoccurrence of craniodorsal hip luxation was higher in group B than in group A, in 5/8 and 0/8 tests, respectively. Moreover, in group A, the extra-articular UHMWPE implant induced caudodorsal hip luxation, reported as failure mode in 7/8 cases.

CONCLUSIONS AND RELEVANCE

This modified biomechanical protocol for testing craniodorsal hip luxation in a feline model was validated as repeatable and with acceptable variance. The extra-articular UHMWPE implant stabilisation technique proved to be more efficient in avoiding reoccurrence of craniodorsal hip luxation than UHMWPE iliofemoral suture.

Ex vivo postimplantation biomechanical properties of a press-fit cementless femoral stem with transfixation pin for canine total hip replacement

OBJECTIVE

To compare ex vivo postimplantation biomechanical characteristics of 3 implants for canine total hip replacement: a cementless press-fit femoral stem with a pin in the femoral neck (p-pfFS), a press-fit cementless femoral stem without this pin (pfFS), and a cemented femoral stem (cFS).

SAMPLE

18 cadaveric femurs from 9 dogs.

PROCEDURES

Femurs were assigned randomly to 3 groups, and biomechanical testing was performed by measuring vertical displacement during cyclic loading and resistance to failure with compression parallel to the longitudinal axis of the femur. Force-displacement curves were assessed for failure tests, and work necessary for failure was calculated.

RESULTS

No significant differences were observed in vertical displacement during cyclic loading (P = .263) or work necessary for failure (P = .079). Loads to failure for cFS and p-pfFS implants were significantly greater than that for the pfFS, but no significant difference in load to failure was observed between cFS and p-pfFS implants (P = .48).

CLINICAL RELEVANCE

Cementless femoral stems with a transfixation pin offer significantly greater immediate resistance to failure to compressive loads parallel to the longitudinal axis of the femur than standard cementless stems, and a level of stability comparable to that of cemented stems. p-pfFS implants may be valuable in total hip replacement, potentially reducing the risk of fracture during the early postoperative period prior to osteointegration.

Mechanical evaluation of a novel angle-stable interlocking nail in a gap fracture model

OBJECTIVE

To describe the mechanical characteristics of a novel angle-stable interlocking nail (NAS-ILN) and compare them to those of a locking compression plate (LCP) by using a gap-fracture model.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Synthetic bone models.

METHODS

Synthetic bone models simulating a 50 mm diaphyseal comminuted canine tibial fracture were treated with either a novel angle-stable interlocking nail (NAS-ILN) or a locking compression plate (LCP). Maximal axial deformation and load to failure in compression and 4-point bending, as well as maximal angular deformation, slack, and torque to failure in torsion, were statistically compared (P < .05).

RESULTS

In compression, the maximal axial deformation was lower for NAS-ILN (0.11 mm ± 0.03) than for LCP (1.10 mm ± 0.22) (P < .0001). The ultimate load to failure was higher for NAS-ILN (803.58 N ± 29.52) than for LCP (328.40 N ± 11.01) (P < .0001). In torsion, the maximal angular deformation did not differ between NAS-ILN (22.79° ± 1.48) and LCP (24.36° ± 1.45) (P = .09). The ultimate torque to failure was higher for NAS-ILN (22.45 Nm ± 0.24) than for LCP (19.10 Nm ± 1.36) (P = .001). No slack was observed with NAS-ILN. In 4-point bending, the maximal axial deformation was lower for NAS-ILN (3.19 mm ± 0.49) than for LCP (4.17 mm ± 0.34) (P = .003). The ultimate bending moment was higher for NAS-ILN (25.73 Nm, IQR [23.54-26.86] Nm) than for LCP (16.29 Nm, IQR [15.66-16.47] Nm) (P = .002).

CONCLUSION

The NAS-ILN showed greater stiffness in compression and 4-point bending, and a greater resistance to failure in compression, torsion, and 4-point bending, than LCP.

CLINICAL IMPACT

Based on these results, NAS-ILNs could be considered as alternative implants for the stabilization of comminuted fractures.

Transoral ventral tympanic bulla osteotomy in cats: 13 cases (2016-2019)

OBJECTIVE

To analyze the results of transoral ventral bulla osteotomy (TOVBO) in cats.

ANIMALS

13 client-owned cats treated by TOVBO between February 2016 and February 2019.

PROCEDURES

Medical records of cats with a diagnosis of middle ear disease (MED) that underwent TOVBO were reviewed. The procedure was similar to the one described for dogs. Short-term follow-up was obtained via clinical examination before discharge and at day 15 postoperatively. Long-term follow-up was performed via telephone interview.

RESULTS

13 cats (age range, 8 months to 12 years) underwent unilateral (n = 10) or bilateral (3) TOVBO (16) for the treatment of tympanic bulla (TB) infection (10), nasopharyngeal inflammatory polyps (5), or bullet retrieval from the TB (1). There were no intraoperative complications. One cat with a poor preoperative status died at postoperative day 3 from pneumonia. Eight cats experienced postoperative complications including head tilt (n = 2), Horner syndrome (3), loss of appetite (2), and temporary blindness (1). Collected samples confirmed the presence of nasopharyngeal inflammatory polyps (5), or otitis media (8). Six months after surgical intervention, 9 cats were free of MED signs.

CLINICAL RELEVANCE

This oral approach provided a good access to the TB in all cases. The complications observed after TOVBO were similar to those for VBO. In cats, TOVBO seems to be an acceptable and safe minimally invasive alternative to the other approaches of the TB to address MED.

Long-term outcome following synthetical reconstruction of the tarsal medial collateral ligament in a dog

Background: Tibiotarsal instabilities caused by partial or complete rupture of the medial collateral tarsal ligament (MCTL) are commonly treated by arthrodesis techniques with poor functional results and significant complication rates. Case description: This study describes a new surgical technique for synthetic reconstruction of the MCTL in an overweight dog (estimated body condition score 8/9) with an avulsion of the long head of the MCTL. Three bone tunnels were drilled in the distal tibia, the talus and the central tarsal bone, thus respecting the anatomical insertions of the physiological ligament. An Ultra-High Molecular Weight Polyethylene (UHMWPE) implant was fixed with interference screws to reconstruct the long and short heads of the MCTL. Premature weight-bearing was reported at two weeks postoperatively following early removal of the flexible restraint (bivalve resin boot), which had initially been prescribed for six weeks. At 11 weeks postoperatively, the tibiotarsal joint showed good valgus stability and the dog's gait was subnormal. At 12 and 16 months postoperatively, the dog regained full function of the operated limb although no weight loss was initiated as recommended. Conclusion: The use of a UHMWPE implant fixed with interference screws to reconstruct the MCTL allowed a return to full function of the tibiotarsal joint, without complications despite an early return to weight-bearing without external restraint. The success of this isolated surgical technique could lead to improvements in the surgical management of MCTL rupture if these initial results are confirmed by a prospective study with a larger number of patients.

Biomechanical cyclic loading test of a synthetic ligament fixation system used for intra-articular stabilization of deficient canine stifles

Background: Cranial cruciate ligament rupture (CCLr) is the most common cause of hindlimb lameness in dogs. Currently, surgical management of CCLr is mostly performed using tibial osteotomy techniques to modify the biomechanical conformation of the affected stifle. These surgical techniques have a significant complication rate, associated with persistent instability of the stifle which may lead to chronic postoperative pain. Over the last decade, studies have been published on various techniques of anatomical CCL reconstruction in veterinary practice, using physiological autografts or woven synthetic implants. Aim: The aim of this ex vivo biomechanical study is to investigate the ex vivo dynamic biomechanical behavior of a synthetic implant (ultra-high molecular weight polyethylene implant) fixed with interference screws for the treatment of cranial cruciate ligament rupture in dogs, according to a fatigue protocol (48h per test). Methods: Seven stifles from four skeletally mature canine cadavers were implanted with the synthetic implant. It was fixed with four interference screws inserted in transversal and oblique tunnels in both the distal femur and the proximal tibia. For each case, 100 000 cycles were performed at 0.58Hz, with traction loads ranging from 100N to 210N. Results: Neither screw-bone assembly rupture nor a pull-out issue were observed during the dynamic tests. The linear stiffness of the implants associated with a fixation system with four interference screws increased over time. The final displacement did not exceed 3mm for five of the seven specimens. Five of the seven synthetic implants yielded to a lengthening in functional range [0: 3 mm]. Linear stiffness was homogeneous among samples, showing a strong dynamic strength of the interference screw-based fixations of the UHMWPE implant in the femoral and tibial bones. Conclusion: This study completes the existing literature on the biomechanical evaluation of passive stifle stabilization techniques with a testing protocol focused on cyclic loading at a given force level instead of driven by displacement. These biomechanical results should revive interest in intra-articular reconstruction after rupture of the cranial cruciate ligament in dogs.

Anatomical features of the canine C2-C3 spinal cord vascular environment

OBJECTIVE

Interarcuate branch (IAB) is a vascular structure, particularly developed in C2-3 intervertebral space, forming a dorsal bridge that connects ventral venous plexi in the vertebral canal. While precisely described in the human, the precise anatomical features of IABs have not been reported in the veterinary literature. The purpose of this study is to describe the features and relations of IABs in the C2-3 vertebral canal.

ANIMALS

10 dogs were enrolled; 5 dogs for necropsy and 5 dogs for histology.

PROCEDURES

The ventral venous plexi in the cervical spine of 5 dogs were injected with latex and underwent vertebral canal dissection for visual assessment of the IAB. Two out of 5 dogs were injected with the addition of barium sulfate and underwent a CT scan. The C2-3 regions of 5 small-breed dogs were harvested for histological examinations.

RESULTS

IABs arose from the ventral venous plexus at the level of the intervertebral vein; they originated from 2 separate branches located caudally and cranially to the intervertebral foramen, forming a ventrodorsal triangle surrounding the spinal nerve root. No dorsal anastomosis was observed on the CT scan nor at dissection but were observed histologically. A cervical fibrous sheath was observed all around the vertebral canal.

CLINICAL RELEVANCE

IABs are voluminous venous structures at the C2-3 intervertebral space in dogs and found within a split of the cervical fibrous sheath, which is adherent to the interarcuate ligament and the ligamentum flavum. This anatomical description is paramount when planning an approach to the C2-3 intervertebral space.

Modified Triple Tibial Osteotomy for Combined Cranial Cruciate Ligament Rupture, Tibial Deformities, or Patellar Luxation

Proximal tibial deformities or patellar luxation may occur concurrently with cranial cruciate ligament rupture. The objective of this study was to describe the management of those conditions with a modified triple tibial osteotomy (TTO) in nine dogs. Medical records of dogs who underwent a modified TTO were reviewed. The mean pre- and postoperative patellar tendon angles were 104.2° and 92.9°, respectively. The mean pre- and postoperative mechanical medial proximal tibial angles were 99.5° and 91.5°, respectively. Medial patellar luxation was present in five dogs (55.6%) and treated in all five dogs with a tibial crest transposition. Tibial torsion was grossly resolved in two dogs (22.2%). Perioperative distal tibial crest fracture was treated by pins and a figure-of-eight tension-band wire in five dogs (55.6%). One major (surgical site infection) and three minor postoperative complications were observed. At the last follow-up, seven dogs (77.8%) had no lameness, one dog (11.1%) had mild lameness, and one dog (11.1%) had moderate lameness. Radiographic evaluation showed good (2/9; 22.2%) to excellent (7/9; 77.8%) bone healing. The visual analog scale evaluation revealed good-to-excellent owner satisfaction. Cranial cruciate ligament rupture, tibial deformities, and medial patellar luxation are difficult to treat together. A modified TTO may be used to treat these conditions.

Comparison of the different supports used in veterinary medicine for pressure sore prevention

OBJECTIVES

To compare the pressure-relieving capacity of different supports used in veterinary medicine and to find the more common pressure sore locations in laterally recumbent dogs, so as to recommend protocols for decubitus ulcer prevention.

MATERIALS AND METHODS

We compared the support properties of: (1) blankets on the floor, (2) a standard mattress, (3) a veterinary memory foam mattress and (4) a human medicine memory foam mattress. Three cadaver dogs with different body condition scores but similar sizes were positioned on the different supports in lateral recumbency. Pressures were measured in each dog and at each support contact point over a 4-hour period using a TexiSense pressure mat.

RESULTS

Regardless of the body condition score and the support used, the skin overlying the scapula-humeral articulation, the greater trochanter and the thirteenth rib were the recurrent risk zones. In these risk zones, pressure-relieving mats led to lower pressures than did the standard mats or the blanket placed on the floor. The contact pressures appeared to depend on body condition score, with maximal pressures observed in thin dogs.

CLINICAL SIGNIFICANCE

It is important to use a pressure-relieving mat to reduce the risk of pressure sores, but static pressure-relieving mats are generally insufficient to maintain safe pressures in risk zones (<60 mmHg), particularly in thin patients, and so frequent changes in position are recommended.

Cellulose Nanofiber-Reinforced Chitosan Hydrogel Composites for Intervertebral Disc Tissue Repair

The development of non-cellularized composites of chitosan (CHI) hydrogels, filled with cellulose nanofibers (CNFs) of the type nanofibrillated cellulose, was proposed for the repair and regeneration of the intervertebral disc (IVD) annulus fibrosus (AF) tissue. With the achievement of CNF-filled CHI hydrogels, biomaterial-based implants were designed to restore damaged/degenerated discs. The structural, mechanical and biological properties of the developed hydrogel composites were investigated. The neutralization of weakly acidic aqueous CNF/CHI viscous suspensions in NaOH yielded composites of physical hydrogels in which the cellulose nanofibers reinforced the CHI matrix, as investigated by means of microtensile testing under controlled humidity. We assessed the suitability of the achieved biomaterials for intervertebral disc tissue engineering in ex vivo experiments using spine pig models. Cellulose nanofiber-filled chitosan hydrogels can be used as implants in AF tissue defects to restore IVD biomechanics and constitute contention patches against disc nucleus protrusion while serving as support for IVD regeneration.

Long-Term Safety and Efficacy of Single or Repeated Intra-Articular Injection of Allogeneic Neonatal Mesenchymal Stromal Cells for Managing Pain and Lameness in Moderate to Severe Canine Osteoarthritis Without Anti-inflammatory Pharmacological Support: Pilot Clinical Study

Objective: To explore the long-term safety and efficacy of canine allogeneic mesenchymal stromal cells (MSC) administered intra-articularly as single or repeated injections in appendicular joints of dogs affected by moderate to severe refractory osteoarthritis.

Study Design: 22 pet dogs were recruited into a non-randomized, open and monocentric study initially administering one cellular injection. A second injection was offered after 6 months to owners if the first injection did not produce expected results.

Materials and Methods: Anti-inflammatory treatment (if prescribed) was discontinued at last one week before the onset of treatment. Each injection consisted of at least 10 million viable neonatal allogeneic mesenchymal stromal cells obtained from fetal adnexa. Medical data was collected from veterinary clinical evaluations of joints up to 6 months post-injection and owner's assessment of their dog's mobility and well-being followed for a further 2 years when possible.

Results: Mild, immediate self-limiting inflammatory joint reactions were observed in 5/22 joints after the first injection, and in almost all dogs having a subsequent injection. No other MSC-related adverse medical events were reported, neither during the 6 months follow up visits, nor during the long-term (2-years) safety follow up. Veterinary clinical evaluation showed a significant and durable clinical improvement (up to 6 months) following MSC administration. Eight dogs (11 joints) were re-injected 6 months apart, sustaining clinical benefits up to 1 year. Owner's global satisfaction reached 75% at 2 years post-treatment

Conclusion: Our data suggest that a single or repeated intra-articular administration of neonatal MSC in dogs with moderate to severe OA is a safe procedure and confer clinical benefits over a 24-month period. When humoral response against MSC is investigated by flow cytometry, a positive mild and transient signal was detected in only one dog from the studied cohort, this dog having had a positive clinical outcome.

Injectable and Gellable Chitosan Formulations Filled with Cellulose Nanofibers for Intervertebral Disc Tissue Engineering

The development of non-cellularized injectable suspensions of viscous chitosan (CHI) solutions (1.7⁻3.3% (w/w)), filled with cellulose nanofibers (CNF) (0.02⁻0.6% (w/w)) of the type nanofibrillated cellulose, was proposed for viscosupplementation of the intervertebral disc nucleus pulposus tissue. The achievement of CNF/CHI formulations which can gel in situ at the disc injection site constitutes a minimally-invasive approach to restore damaged/degenerated discs. We studied physico-chemical aspects of the sol and gel states of the CNF/CHI formulations, including the rheological behavior in relation to injectability (sol state) and fiber mechanical reinforcement (gel state). CNF-CHI interactions could be evidenced by a double flow behavior due to the relaxation of the CHI polymer chains and those interacting with the CNFs. At high shear rates resembling the injection conditions with needles commonly used in surgical treatments, both the reference CHI viscous solutions and those filled with CNFs exhibited similar rheological behavior. The neutralization of the flowing and weakly acidic CNF/CHI suspensions yielded composite hydrogels in which the nanofibers reinforced the CHI matrix. We performed evaluations in relation to the biomedical application, such as the effect of the intradiscal injection of the CNF/CHI formulation in pig and rabbit spine models on disc biomechanics. We showed that the injectable formulations became hydrogels in situ after intradiscal gelation, due to CHI neutralization occurring in contact with the body fluids. No leakage of the injectate through the injection canal was observed and the gelled formulation restored the disc height and loss of mechanical properties, which is commonly related to disc degeneration.

Comparison of Early Measurements of the Distraction Index, Norberg Angle on Distracted View and the Official Radiographic Evaluation of the Hips of 215 Dogs from Two Guide Dog Training Schools

OBJECTIVES

 The main purpose of this article is to evaluate the correlation between the distraction index (DI) and Norberg angle values in distracted hips (distraction Norberg angle, DNA) at 4 months of age and the official hip score based on the Fédération Cynologique Internationale (FCI) grid at 12 months of age.

METHODS

 For dogs (n = 215) from two guide dog training organizations, the DI and DNA were measured by a single expert on distraction radiographs performed at 4 months of age. The FCI score was determined by the same expert at 12 months of age on a standard hip-extended view.Statistical analysis included receiver operating characteristic curve analysis and concordance correlation coefficient calculation.

RESULTS

 The mean DI was 0.48, the mean DNA was 86.5° and 59.5% of hips had an A FCI score. The concordance correlation coefficient of DI and DNA was 0.78. The DI threshold for D- and E-scored hips that was associated with the least misclassification was 0.58 (sensitivity [Se] = 0.6, specificity [Sp] = 0.82). The DNA threshold that was associated with the least misclassification was 85° (Se = 0.83, Sp = 0.68).

CLINICAL SIGNIFICANCE

 DNA has a fair correlation with DI at 4 months and reflects hip passive laxity. D and E FCI scores at 12 months cannot be reliably predicted from the 4 months value of DI or DNA but 96% of hips with DI < 0.58 at 4 months had an A, B or C FCI score at 12 months of age. Similarly, 98% of hips with DNA > 85° at 4 months had an A, B or C FCI score at 12 months of age.

Evolution of Radiographic Parameters of Canine Passive Hip Laxity at 4, 6 and 12 months: A Study of 306 Dogs

Objectives This article evaluates the variation in the distraction index (DI) and Norberg angle measurement with the femur in a neutral position and the hips distracted (distraction Norberg angle [DNA]) between 4, 6 and 12 months of age.

Methods Radiographic data from dogs (n = 306) line-bred for favourable characteristics, including hip conformation, were reviewed. Dogs underwent stress radiographs, using a Vezzoni distractor, at 4, 6 and 12 months of age. The DI and DNA were calculated, and their evolution was studied for the total population and the sub-category of hips with a DI > 0.7.

Results For the total population, the DI showed a significant increase from 4 to 6 months and a significant decrease at 12 months. For the hips with a DI > 0.7 at 4 months, DI at 6 and 12 months showed a significant decrease (0.14 and 0.26, respectively, on average). For the total population, the DNA followed the same pattern as the DI, and the values are significantly associated (p < 0.001).

Clinical Significance The DI varies significantly from 4 to 12 months in dogs, and the time of radiographic evaluation of hip laxity may strongly influence the value of the DI. The DNA is strongly related to the DI, and its use as a more convenient indicator of hip laxity in dogs should be further investigated.

An in vitro biomechanical comparison between bone plate and interlocking nail

In order to compare the interfragmentary motion and bone strains in ostectomized canine femurs, stabilized with either an 8 mm interlocking nail system (IN) or a 10-hole 3.5 mm dynamic compression broad plate (DCP), ten pairs of adult canine femurs with a 25 mm mid-diaphyseal gap were used. The left femurs were implanted with a DCP and eight bi-cortical screws, and the right femurs were implanted with an IN and three screws. Eccentric axial loading and cranio-caudal bending were successively performed on every specimen. Employing an opto-electronic device, interfragmentary (axial, transverse and rotational) motion was measured during non-destructive tests. Bone strains were measured at three elective sites, with strain gauges in four pairs of the specimen. The mean values of axial and transverse motion were compared using a paired t-test within each group (P <0.05). Strain values were compared using a numerical scale and a qualitative analysis. Transverse motion was higher with DCP, whereas axial motion was higher with IN. Bone strain analysis demonstrated lower “stress protection” near the gap with IN. Those comparative results are interpretative: IN may be an interesting alternative implant for unstable diaphyseal femoral fracture repair in dogs.

Canine hip dysplasia radiographic screening. Prevalence of rotation of the pelvis along its length axis in 7,012 conventional hip extended radiographs

The prevalence of rotation of the pelvis along its length axis was noted, as was the number of rotations towards the right or left hand side of the dog, on 7,012 conventional hip extended radiographs, which were sent for official screening. 29.8% of the radiographs showed a rotation the pelvis. The rotation was statistically more frequent towards the left hand side of the dog. The number of rejected radiographs for too important pelvis rotation was only 5.2%. The consequences of the pelvis rotation on the Norberg-Olsson angle, on the dorsal femoral head coverage, and in the aspect of cranial acetabular edge have to be taken into account when scoring the dog for hip dysplasia.

Safe corridor for the implantation of thoracolumbar pedicle screws in growing pigs: A morphometric study

The pig spine is widely used as a large animal model for preclinical research in human medicine to test new spinal implants and surgical procedures. Among them, pedicle screw is one of the most common method of fixation of those implants. However, the pedicle of the porcine vertebra is not as well defined and not as large as the pedicle of the human vertebra. Therefore, the position of the screw should be adapted to the pig and not merely transposed based on the literature on humans. The purpose of this study is to determine the characteristics of the optimum implantation corridors for pedicle screws in the thoracolumbar spine of piglets of different ages using computed tomography (CT) and to determine the size and length of these corridors in pigs of different ages. CT scans from five groups of age: 6, 10, 14, 18, and 26 weeks were reviewed. For each thoracolumbar vertebrae, the pedicle width, pedicle axis length, and the pedicle angle was measured for the left and right pedicle. A total of 326 thoracic vertebrae and 126 lumbar vertebrae were included in the study. Pedicles are statistically larger but not longer for the lumbar vertebrae. An important variation of the pedicle angle is observed along the spine. In all pigs, an abrupt modification of the pedicle angle between T10 and T11 was observed, which corresponds to the level of the anticlinal vertebra which is the vertebra for which the spinous process is nearly perpendicular to the vertebral body. In conclusion, this study provides a quantitative database of pedicle screw implantation corridors in pigs of different ages. When using pedicle screws in experimental studies in pigs, these results should be considered for selecting the most suitable implants for the study but also to ensure a correct and safer screw position. Improving study procedures may limit postoperative complications and pain, thereby limiting the use of live animals.

Evaluation of the Effect of a Single Intra-articular Injection of Allogeneic Neonatal Mesenchymal Stromal Cells Compared to Oral Non-Steroidal Anti-inflammatory Treatment on the Postoperative Musculoskeletal Status and Gait of Dogs over a 6-Month Period after Tibial Plateau Leveling Osteotomy: A Pilot Study

OBJECTIVE

Compare the clinical and pressure walkway gait evolution of dogs after a tibial plateau leveling osteotomy (TPLO) for a cranial cruciate ligament rupture (CrCLR) and treatment with either a 1-month course of non-steroidal anti-inflammatory drugs (NSAIDs) or a single postoperative intra-articular (IA) injection of allogeneic neonatal mesenchymal stromal cells (MSCs).

STUDY DESIGN

Prospective, double-blinded, randomized, controlled, monocentric clinical study.

ANIMALS

Sixteen client-owned dogs.

MATERIALS AND METHODS

Dogs with unilateral CrCLR confirmed by arthroscopy were included. Allogeneic neonatal canine MSCs were obtained from fetal adnexa retrieved after C-section performed on healthy pregnant bitches. The dogs were randomly allocated to either the "MSCs group," receiving an IA injection of MSCs after TPLO, followed by placebo for 1 month, or the "NSAIDs group," receiving IA equivalent volume of MSCs vehicle after TPLO, followed by oral NSAID for 1 month. One of the three blinded evaluators assessed the dogs in each group before and after surgery (1, 3, and 6 months). Clinical score and gait and bone healing process were assessed. The data were statistically compared between the two groups for pre- and postoperative evaluations.

RESULTS

Fourteen dogs (nine in the MSCs group, five in the NSAIDs group) completed the present study. No significant difference was observed between the groups preoperatively. No local or systemic adverse effect was observed after MSCs injection at any time point considered. At 1 month after surgery, bone healing scores were significantly higher in the MSCs group. At 1, 3, and 6 months after surgery, no significant difference was observed between the two groups for clinical scores and gait evaluation.

CONCLUSION

A single IA injection of allogeneic neonatal MSCs could be a safe and valuable postoperative alternative to NSAIDs for dogs requiring TPLO surgery, particularly for dogs intolerant to this class of drugs.

Evaluation of a new method to determine the tibial tuberosity advancement distance required to reduce the patellar tendon-tibial plateau angle to 90° with the modified Maquet technique in dogs

OBJECTIVE To assess use of a new radiographic method to determine the distance by which the tibial tuberosity should be advanced to reduce the patellar tendon-tibial plateau angle (PTA) to 90° by means of the modified Maquet technique (MMT) in dogs. SAMPLE 24 pelvic limbs from 12 adult medium-sized to large-breed canine cadavers. PROCEDURES Radiographs of stifle joints at 135° extension in true lateral position were used to determine tibial tuberosity advancement distances for use in the MMT. A method was devised to incorporate the planned osteotomy axis; distal patellar translations of 0, 3, 5, or 10 mm; and advancement cage implant application level along the osteotomy site in advancement planning measurements. Concordance correlation coefficients (CCCs) were calculated to compare these adjusted advancement measurements with true advancement measurements obtained for the same joints in another study after treatment by MMT. Intraobserver, interobserver, and total agreement for selected measurements were determined by assessment of CCCs for results obtained by 3 blinded observers. RESULTS Agreement between true advancement measurements and measurements obtained with osteotomy axis and cage position method calculations that incorporated a 5-mm distal patellar translation distance was excellent (CCC, 0.96). Intraobserver and interobserver agreements for the planning measurements evaluated were good to excellent (CCC, 0.83 to 0.96). CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the osteotomy axis and cage position method incorporating a 5-mm distal patellar translation distance has the potential to improve success rates for achieving a PTA of 90° in medium-sized to large-breed dogs undergoing MMT for treatment of cranial cruciate ligament rupture. Further research is warranted.

Comparison of desired radiographic advancement distance and true advancement distance required for patellar tendon-tibial plateau angle reduction to the ideal 90° in dogs by use of the modified Maquet technique

OBJECTIVE To evaluate the validity of 2 radiographic methods for measurement of the tibial tuberosity advancement distance required to achieve a reduction in patellar tendon-tibial plateau angle (PTA) to the ideal 90° in dogs by use of the modified Maquet technique (MMT). SAMPLE 24 stifle joints harvested from 12 canine cadavers. PROCEDURES Radiographs of stifle joints placed at 135° in the true lateral position were used to measure the required tibial tuberosity advancement distance with the conventional (A^M) and correction (A^E) methods. The MMT was used to successively advance the tibial crest to A^M and A^E. Postoperative PTA was measured on a mediolateral radiograph for each advancement measurement method. If none of the measurements were close to 90°, the advancement distance was modified until the PTA was equal to 90° within 0.1°, and the true advancement distance (TA) was measured. Results were used to determine the optimal commercially available size of cage implant that would be used in a clinical situation. RESULTS Median A^M and A^E were 10.6 mm and 11.5 mm, respectively. Mean PTAs for the conventional and correction methods were 93.4° and 92.3°, respectively, and differed significantly from 90°. Median TA was 13.5 mm. The A^M and A^E led to the same cage size recommendations as for TA for only 1 and 4 stifle joints, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Both radiographic methods of measuring the distance required to advance the tibial tuberosity in dogs led to an under-reduction in postoperative PTA when the MMT was used. A new, more accurate radiographic method needs to be developed.

Chitosan solutions as injectable systems for dermal filler applications: Rheological characterization and biological evidence

A new generation of dermal filler for wrinkle filler based on chitosan was compared to current hyaluronic acid-based dermal fillers by using a new rheological performance criterion based on viscosity during injection related to Newtonian viscosity. In addition an in vivo evaluation was performed for preclinical evidence of chitosan use as dermal filler. In this way, biocompatibility and dermis reconstruction was evaluated on a pig model.

Thoracolumbar partial lateral corpectomy for the treatment of chronic intervertebral disc disease in 107 dogs

Background

The purpose of this retrospective study was to assess short-and medium-term outcomes in dogs with chronic ventral thoracolumbar intervertebral disc disease (IVDD) treated by thoracolumbar partial lateral corpectomy (TLPLC).

Dogs surgically treated for chronic ventral IVDD by TLPLC were included. For each dog, neurological status evolution and complications were reported. Factors that could have influenced neurological recovery were statistically tested.

Results

A total of 107 dogs were included in the study. Before surgery, 67.3 % of the dogs were able to walk, 24.3 % were grade 3, and 8.4 % were grade 4. The median hospitalization time was 3 days, and 82.2 % of the dogs were able to walk at discharge. The medium-term neurological grade was reached at a median time of 2 months. At the medium-term follow-up (median 12 months), 74.3 % of the dogs were neurologically improved, 22.9 % were stable, and 2.8 % were worsened. A total of 91.4 % of dogs were ambulatory, with 58.6 % of dogs having a normal gait. Preoperative neurological grade was significantly associated with the neurological status 24 h after the surgery and at discharge. Dogs with a higher preoperative neurological grade had a better chance of improving but lower odds of walking at 24 h after the surgery and at discharge compared with dogs with a lower preoperative grade. Spinal compression recurrence at the same surgical site was confirmed in 8 cases.

Conclusion

Even if TLPLC leads to several intra and postoperative complications, this technique is a viable surgical option to treat chronic ventral IVDD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13620-015-0056-z) contains supplementary material, which is available to authorized users.

Pedicle Screw Fixation Study in Immature Porcine Spines to Improve Pullout Resistance during Animal Testing

The porcine model is frequently used during development and validation of new spinal devices, because of its likeness to the human spine. These spinal devices are frequently composed of pedicle screws with a reputation for stable fixation but which can suffer pullouts during preclinical implantation on young animals, leading to high morbidity. With a view to identifying the best choices to optimize pedicle screw fixation in the porcine model, this study evaluates ex vivo the impact of weight (age) of the animal, the level of the vertebrae (lumbar or thoracic) and the type of screw anchorage (mono- or bi-cortical) on pedicle screw pullouts. Among the 80 pig vertebrae (90- and 140-day-old) tested in this study, the average screw pullout forces ranged between 419.9N and 1341.2N. In addition, statistical differences were found between test groups, pointing out the influence of the three parameters stated above. We found that the the more caudally the screws are positioned (lumbar level), the greater their pullout resistance is, moreover, screw stability increases with the age, and finally, the screws implanted with a mono-cortical anchorage sustained lower pullout forces than those implanted with a bi-cortical anchorage. We conclude that the best anchorage can be obtained with older animals, using a lumbar fixation and long screws traversing the vertebra and inducing bi-cortical anchorage. In very young animals, pedicle screw fixations need to be bi-cortical and more numerous to prevent pullout.

Meniscal biomechanical alterations in an ACLT rabbit model of early osteoarthritis

OBJECTIVE

The purpose of this study was to analyze the early biomechanical alterations of menisci during the early stage of osteoarthritis (OA) development and to correlate them with the chemical composition and matrix alteration. A particular focus was paid to pathological changes in glycosaminoglycan (GAG) content and collagen fiber architecture.

DESIGN

Menisci (n = 24) were removed from rabbits' knee joints 6 weeks following surgical anterior cruciate ligament transection (ACLT). Both the anterior and posterior regions of medial and lateral menisci were characterized using indentation tests, Raman microspectroscopy (RM), biphotonic confocal microscopy (BCM) and histology.

RESULTS

Mechanical and matrix alterations occurred in both regions of medial and lateral menisci. A significant decrease in the mechanical properties was observed in OA menisci, with a mean reduced modulus from 2.3 to 1.1 MPa. Microstructural observations revealed less organized and less compact collagen bundles in operated menisci than in contralateral menisci, as well as a loss of fiber tension. GAG content was increased in OA menisci, especially in the damaged areas. Neither changes in the secondary structure of collagen nor mineralization were detected through RM at this stage of OA.

CONCLUSION

ACLT led to a disorganization of the collagen framework at the early stage of OA development, which decreases the mechanical resistance of the menisci. GAG content increases in response to this degradation. All of these results demonstrate the strong correlation between matrix and mechanical alterations.

Intra-articular administration of xenogeneic neonatal Mesenchymal Stromal Cells early after meniscal injury down-regulates metalloproteinase gene expression in synovium and prevents cartilage degradation in a rabbit model of osteoarthritis

OBJECTIVE

The anti-inflammatory and anti-catabolic effects of neonatal Mesenchymal Stromal Cell (MSC) were investigated in a xenogeneic model of mild osteoarthritis (OA). The paracrine properties of MSC on synoviocytes were further investigated in vitro.

STUDY DESIGN

OA was induced by medial meniscal release (MMR) in 30 rabbit knees. A single early (day 3) or delayed (day 15) intra-articular (IA) injection of MSC isolated from equine Umbilical Cord Wharton's jelly (UC-MSC) was performed. Rabbits were euthanized on days 15 or 56. OA grading was performed and gene expression of inflammatory cytokines and metalloproteinases was measured in synovial tissue. Paracrine effects of UC-MSC were investigated using UC-conditioned vs control medium on rabbit primary synoviocytes stimulated with interleukin 1 beta in vitro.

RESULTS

No adverse local or systemic responses were observed clinically after xenogeneic UC-MSC injection. At study end point, cartilage fibrillation was lower in early treatment than in delayed treatment group. Cellular infiltrate was observed in the synovium of both UC-MSC groups. OA synovium exhibited a reduced expression of metalloproteinases-1, -3, -13 in the early cell-treated group at d56. In vitro, UC-conditioned medium exerted anti-inflammatory and anti-catabolic effects on synoviocytes exposed to pro-inflammatory stimulus.

CONCLUSIONS

Early IA injection of equine UC-MSC was effective in preventing OA signs in rabbit knees following MMR. UC-MSC target the synovium and modulate the gene expression pattern of synoviocytes to promote an anti-catabolic environment. This confirms the synovium is a major target and mediator of MSC therapy, modulating the expression of matrix-degrading enzymes.

Coil optimization for low-field MRI: a dedicated process for small animal preclinical studies

We demonstrate a method for the fast in vivo quantification of small volumes, down to 25 µL, using low-field magnetic resonance imaging (MRI) coils. The coils were designed so as to maximize the signal-to-noise ratio (SNR) in the images. For this we developed an analytical model for describing the variations of the SNR with coil design and with size/shape suited to the object under observation. Based on the conclusions drawn from the model, the coil parameters were chosen in order to reach an SNR close to the maximum. For the validation of the model, coils were finally characterized in terms of quality factor using saline phantoms. The coil design procedure is illustrated here with two examples: first, the quantification of about 200 µL of intradermal injected gel on rabbits with a single loop surface coil and second, the imaging of the intervertebral disks in rat tails using a small volume coil to detect possible lesions. Such studies would not have been feasible for the clinical low-field MRI system at our disposal using any of the commercially available medium-sized manufactured coils. As a result of this simple optimization procedure, a wide range of applications is accessible even at low magnetic fields, leading to new opportunities for low-cost, though efficient, preclinical studies.