Eithne Comerford

Update on the aetiopathogenesis of canine cranial cruciate ligament disease.

Cranial cruciate ligament disease (CCLD) is the most common cause of hindlimb lameness in the dog, being associated with and eventually leading to stifle osteoarthritis. Canine cranial cruciate ligament disease is a gradual degeneration of the ligament extracellular matrix (ECM) leading to ligament rupture. The aetiopathogenesis of this condition is still poorly understood but several risk factors have been identified such as breed, bodyweight, gender and conformation. Recent developments in this area include the role of genetics, stifle joint conformation, ligament ECM metabolism, and inflammation associated with immune-mediated disease within the stifle joint. A genetic mode of inheritance has been demonstrated in the Newfoundland which is predisposed to CCLD. Increased cellular metabolism within the cranial cruciate ligament has been directly associated with increased craniocaudal stifle joint laxity in dog breeds at high risk of CCLD. Conformation abnormalities, such as a narrowed distal femoral intercondylar notch, in high risk breeds have been shown to be associated with alterations in cranial cruciate ligament ultrastructure. Increased production of inflammatory cytokines, such as cathepsins and interleukins, by the stifle synovial cells may occur secondary to or may be an inciting cause of ligament degeneration. Future research endeavours will focus on the association between immune-mediated response and fibrocartilaginous metaplasia and matrix degradation within the cranial cruciate ligament, and whether this can be altered in all susceptible dogs or only certain breeds.

The organisation of elastin and fibrillins 1 and 2 in the cruciate ligament complex

Although elastin fibres and oxytalan fibres (bundles of microfibrils) have important mechanical, biochemical and cell regulatory functions, neither their distribution nor their function in cruciate ligaments has been investigated. Twelve pairs of cruciate ligaments (CLs) were obtained from 10 adult dogs with no evidence of knee osteoarthritis. Elastic fibres were identified using Verhoeff’s and Miller’s staining. Fibrillins 1 and 2 were immunolocalised and imaged using confocal laser scanning microscopy. Hydrated, unfixed tissue was analysed using Nomarski differential interference microscopy (NDIC), allowing structural and mechanical analysis. Microfibrils and elastin fibres were widespread in both CLs, predominantly within ligament fascicles, parallel to collagen bundles. Although elastin fibres were sparse, microfibrils were abundant. We described abundant fibres composed of both fibrillin 1 and fibrillin 2, which had a similar pattern of distribution to oxytalan fibres. NDIC demonstrated complex interfascicular and interbundle anatomy in the CL complex. The distribution of elastin fibres is suggestive of a mechanical role in bundle reorganisation following ligament deformation. The presence and location of fibrillin 2 in oxytalan fibres in ligament differs from the solely fibrillin 1‐containing oxytalan fibres previously described in tendon and may demonstrate a fundamental difference between ligament and tendon.

Long-term use of gabapentin for musculoskeletal disease and trauma in three cats

Gabapentin has been widely used in human medicine to control acute and chronic pain. Although the exact mechanism of action has yet to be determined, its use in veterinary medicine is increasing. The clinical use of gabapentin for analgesia in cats has been reported in review articles and one case report. Managing chronic pain, particularly in the feline patient, poses a challenge to veterinary surgeons. This report details the long-term use of gabapentin for musculoskeletal pain or head trauma in three cats. All cats received gabapentin for several months at an average dose of 6.5 mg/kg q12h. Clinical signs suggestive of pain, such as aggression, avoiding human interaction and loss of appetite, were observed to decrease with the administration of gabapentin, used as part of an analgesia regime or as sole medication. Long-term follow-up with the owners of all cats indicated that satisfactory pain management was achieved, administration was easy and no obvious side effects during the period of administration occurred. We conclude that long-term treatment with gabapentin is of potential benefit in controlling pain in cases of head trauma, as well as musculoskeletal disease. It may provide a valuable adjunct for the management of chronic pain in cats and should be investigated further for its clinical use and safety.

Management of cranial cruciate ligament rupture in small dogs: A questionnaire study

OBJECTIVES To survey the current management of cranial cruciate ligament rupture in small dogs (<15 kg) by veterinarians. METHODS A questionnaire was distributed to veterinarians attending the British Veterinary Orthopaedic Association Spring meeting and British Small Animal Veterinary Association Annual Congress which took place in April 2010. Respondents were surveyed on their management of small dogs with cranial cruciate ligament rupture. RESULTS Immediate surgical management was chosen by 15.5% of the respondents. Following that, 77.6% of respondents suggested that case management would depend on severity of lameness (81%), age (72.6%), bodyweight (70.4%), degree of instability (64.8%), and duration of lameness (64.0%). Conservative management included non-steroidal anti-inflammatory drugs (91.1%), short leash walks (91.1%), weight loss (89.0%), hydrotherapy (53.6%), physiotherapy (41.9%), and cage rest (24.2%). Where surgical management was chosen, 71.4% would perform the procedure rather than refer it to another practice. Surgical techniques included extra-capsular stabilisation (63.4%), corrective osteotomies (32.9%), and intra-articular stabilisation (6.8%). The demographic characteristics of the responding veterinarians had no effect on their initial management of the case. General practice veterinarians were less likely to perform a corrective osteotomy than to refer the case, but were no less likely to perform an extracapsular technique. CLINICAL SIGNIFICANCE Conservative management is still widely used for treatment of cranial cruciate ligament rupture in dogs weighing less than 15 kg; this is in agreement with previous publications on the management of this condition in small dogs.

Postoperative Complications after Surgical Management of Incomplete Ossification of the Humeral Condyle in Dogs

Objective: To describe incidence and type of postoperative complications in the surgical management of incomplete ossification of the humeral condyle (IOHC) and identify any risk factors associated with development of these complications. Study Design: Case series. Methods: Clinical records of dogs (n=57) that had prophylactic transcondylar screw insertion for treatment of IOHC (79 elbows) at 6 UK referral centers were reviewed. Signalment, presentation, surgical management, postoperative care, and complications were recorded. Postoperative complications were divided into seroma, surgical site infections (SSI) and implant complications. Results: Spaniel breeds and entire males were overrepresented. The overall complication rate was 59.5%. Seroma (n=25) and SSI (24) were the most commonly encountered complications. Implant failure occurred in 2 dogs. Labrador retrievers were at greater risk of developing a postoperative complication than other breeds (P=.03). Increasing bodyweight was a significant risk factor for development of a SSI (P=.03). Placement of the transcondylar screw in lag fashion rather than as a positional screw reduced the incidence of postoperative SSI (P=.007). Conclusions: Surgical management of IOHC is associated with a high rate of postoperative complications. Placement of the transcondylar screw in lag fashion may limit postoperative complications and warrants further consideration.OBJECTIVE To describe incidence and type of postoperative complications in the surgical management of incomplete ossification of the humeral condyle (IOHC) and identify any risk factors associated with development of these complications. STUDY DESIGN Case series. METHODS Clinical records of dogs (n=57) that had prophylactic transcondylar screw insertion for treatment of IOHC (79 elbows) at 6 UK referral centers were reviewed. Signalment, presentation, surgical management, postoperative care, and complications were recorded. Postoperative complications were divided into seroma, surgical site infections (SSI) and implant complications. RESULTS Spaniel breeds and entire males were overrepresented. The overall complication rate was 59.5%. Seroma (n=25) and SSI (24) were the most commonly encountered complications. Implant failure occurred in 2 dogs. Labrador retrievers were at greater risk of developing a postoperative complication than other breeds (P=.03). Increasing bodyweight was a significant risk factor for development of a SSI (P=.03). Placement of the transcondylar screw in lag fashion rather than as a positional screw reduced the incidence of postoperative SSI (P=.007). CONCLUSIONS Surgical management of IOHC is associated with a high rate of postoperative complications. Placement of the transcondylar screw in lag fashion may limit postoperative complications and warrants further consideration.

Proteomic differences between native and tissue-engineered tendon and ligament.

Tendons and ligaments (T/Ls) play key roles in the musculoskeletal system, but they are susceptible to traumatic or age‐related rupture, leading to severe morbidity as well as increased susceptibility to degenerative joint diseases such as osteoarthritis. Tissue engineering represents an attractive therapeutic approach to treating T/L injury but it is hampered by our poor understanding of the defining characteristics of the two tissues. The present study aimed to determine differences in the proteomic profile between native T/Ls and tissue engineered (TE) T/L constructs. The canine long digital extensor tendon and anterior cruciate ligament were analyzed along with 3D TE fibrin‐based constructs created from their cells. Native tendon and ligament differed in their content of key structural proteins, with the ligament being more abundant in fibrocartilaginous proteins. 3D T/L TE constructs contained less extracellular matrix (ECM) proteins and had a greater proportion of cellular‐associated proteins than native tissue, corresponding to their low collagen and high DNA content. Constructs were able to recapitulate native T/L tissue characteristics particularly with regard to ECM proteins. However, 3D T/L TE constructs had similar ECM and cellular protein compositions indicating that cell source may not be an important factor for T/L tissue engineering.

Intra-articular morphine, bupivacaine or no treatment for postoperative analgesia following unilateral elbow joint arthroscopy.

OBJECTIVES To compare intra-articular morphine or bupivacaine against no treatment following unilateral elbow joint arthroscopy using force plate analysis and pain scoring. METHODS Thirty-one dogs were randomly allocated to receive 0·1 mg/kg intra-articular morphine, 0·5 mg/kg bupivacaine or no treatment following elbow arthroscopy. Force plate analysis, pain scoring and kinematic evaluation were performed before anaesthesia, 4 and 24 hours after surgery. Peak vertical force index, symmetry index, rate of loading, rate of unloading, stance time and range of motion were obtained from gait analysis. Pain scoring was performed every 4 hours and interventional analgesia (0·3 mg/kg methadone) was administered if necessary. RESULTS Of 29 dogs analysed, peak vertical force index (P<0·001), symmetry index (P=0·01) and rate of unloading (P=0·01) decreased significantly over time in each group; however, this was not affected by treatment. No significant differences were observed in stance time or rate of loading over time. Kinematic (range of motion) evaluation was not complete for all dogs. Pain scores increased significantly at both time points postoperatively in the no treatment group (P=0·007) and in morphine-treated dogs at 4 hours compared to baseline (P=0·03). For intra-articular bupivacaine significant increases in pain scores were not detected (P=0·28). CLINICAL SIGNIFICANCE No benefit to intra-articular bupivacaine or morphine was detected using peak vertical force index from force plate analysis. Bupivacaine prevented increases in pain scores at both time points as did morphine at the 24-hour evaluation, compared to no treatment.

Micromechanical properties of canine femoral articular cartilage following multiple freeze-thaw cycles

Tissue material properties are crucial to understanding their mechanical function, both in healthy and diseased states. However, in certain circumstances logistical limitations can prevent testing on fresh samples necessitating one or more freeze-thaw cycles. To date, the nature and extent to which the material properties of articular cartilage are altered by repetitive freezing have not been explored. Therefore, the aim of this study is to quantify how articular cartilage mechanical properties, measured by nanoindentation, are affected by multiple freeze-thaw cycles. Canine cartilage plugs (n = 11) from medial and lateral femoral condyles were submerged in phosphate buffered saline, stored at 3–5 °C and tested using nanoindentation within 12 h. Samples were then frozen at −20 °C and later thawed at 3–5 °C for 3 h before material properties were re-tested and samples re-frozen under the same conditions. This process was repeated for all 11 samples over three freeze-thaw cycles. Overall mean and standard deviation of shear storage modulus decreased from 1.76 ± 0.78 to 1.21 ± 0.77 MPa (p = 0.91), shear loss modulus from 0.42 ± 0.19 to 0.39 ± 0.17 MPa (p=0.70) and elastic modulus from 5.13 ± 2.28 to 3.52 ± 2.24 MPa (p = 0.20) between fresh and three freeze-thaw cycles respectively. The loss factor increased from 0.31 ± 0.38 to 0.71 ± 1.40 (p = 0.18) between fresh and three freeze-thaw cycles. Inter-sample variability spanned as much as 10.47 MPa across freezing cycles and this high-level of biological variability across samples likely explains why overall mean “whole-joint” trends do not reach statistical significance across the storage conditions tested. As a result multiple freeze-thaw cycles cannot be explicitly or statistically linked to mechanical changes within the cartilage. However, the changes in material properties observed herein may be sufficient in magnitude to impact on a variety of clinical and scientific studies of cartilage, and should be considered when planning experimental protocols.

Restricted differentiation potential of progenitor cell populations obtained from the equine superficial digital flexor tendon (SDFT).

The aim of this study was to characterize stem and progenitor cell populations from the equine superficial digital flexor tendon, an energy‐storing tendon with similarities to the human Achilles tendon, which is frequently injured. Using published methods for the isolation of tendon‐derived stem/progenitor cells by low‐density plating we found that isolated cells possessed clonogenicity but were unable to fully differentiate towards mesenchymal lineages using trilineage differentiation assays. In particular, adipogenic differentiation appeared to be restricted, as assessed by Oil Red O staining of stem/progenitor cells cultured in adipogenic medium. We then assessed whether differential adhesion to fibronectin substrates could be used to isolate a population of cells with broader differentiation potential. However we found little difference in the stem and tenogenic gene expression profile of these cells as compared to tenocytes, although the expression of thrombospondin‐4 was significantly reduced in hypoxic conditions. Tendon‐derived stem/progenitor cells isolated by differential adhesion to fibronectin had a similar differentiation potential to cells isolated by low density plating, and when grown in either normoxic or hypoxic conditions. In summary, we have found a restricted differentiation potential of cells isolated from the equine superficial digital flexor tendon despite evidence for stem/progenitor‐like characteristics.

Mechanical performance in axial compression of a titanium polyaxial locking plate system in a fracture gap model.

OBJECTIVE To evaluate the bending strength of the VetLOX® polyaxial locking plate system. MATERIALS AND METHODS Thirty-five 3.5 mm 12-hole titanium VetLOX® plates were used to stabilize seven different construct designs in a 1 cm fracture gap simulation model. Each construct was subjected to axial compression. Mean bending stiffness (BS) and yield load (YL) of each construct design were analysed using a one-way ANOVA and Tukey post-hoc analysis. Screw angulation was measured on reconstructed computed tomography (CT) images. RESULTS Reducing plate working length for fixed-angle constructs significantly increased BS (p <0.01) and YL (p <0.01). For a constant plate working length, increasing screw number did not significantly affect BS (p = 1.0) or YL (p = 0.86). Screw angulation measurement technique was validated by intra-class correlation coefficients (ICC) (ICC >0.9 for inter- and intra-observer measurements). An average screw angle of 13.2° did not significantly affect mechanical performance although incomplete screw head-plate engagement was noted on some reconstructed CT images when angulation exceeded 10°. Prefabricated screw-head inserts did not significantly increase mechanical performance. A 4 mm bone-plate stand-off distance significantly reduced BS and YL by 63% and 69% respectively. CLINICAL RELEVANCE The VetLOX® system allows the benefits of polyaxial screw insertion whilst maintaining comparable bending properties to fixed angle insertion. The authors recommend accurate plate contouring to reduce the risk of plate bending.