Surgical treatment of headshaking by removal of a paracondylar process fragment via modified hyovertebrotomy approach: A detailed anatomical and surgical description in an adult horse.

OBJECTIVE: To describe, in detail, the relevant anatomy and surgical approach to access the paracondylar process (PCP) and report its application in a clinical case of headshaking. ANIMAL: A seven-year-old, mixed breed mare. STUDY DESIGN: Experimental study/case report. METHODS: A seven-year-old mixed breed mare was presented for investigation of acute onset progressing violent headshaking, resulting in the horse falling on multiple occasions. The horse was highly reactive to palpation over the right PCP. Standing computed tomographic (CT) investigation and ultrasonographic examination of the head detected a fracture of the right PCP. Five equine heads of mixed breeds and sizes were dissected to demonstrate the relevant anatomy surrounding the PCP with regard to surgical access. A modified hyovertebrotomy approach was used to remove the fracture fragment under general anesthesia. RESULTS: The anatomy surrounding the PCP was described. The fragment was successfully removed resulting in gradual resolution of clinical signs. The horse recovered well postoperatively and was back into light levels of work with no signs of headshaking present two and a half years following surgery. CONCLUSION: The caudal meningeal artery and vein as well as the glossopharyngeal and hypoglossal nerves are adjacent to the PCP and must be avoided during dissections. The modified hyovertebrotomy approach allows safe surgical access to the PCP. Surgical excision of a PCP fragment can result in complete resolution of clinical signs of headshaking. Computed tomography and ultrasonography are valuable diagnostic tools to identify a fracture of the PCP.

Volumetric measurements of paranasal sinuses and examination of sinonasal communication in healthy Shetland ponies: anatomical and morphometric characteristics using computed tomography.

BACKGROUND: Despite clinical importance and frequent occurrence of sinus disease, little is known about the size of paranasal sinuses and their communication in ponies and small horses. To examine the shape and volume of the paranasal sinuses and evaluate the sinonasal communication, three-dimensional (3D) reconstructions of computed tomography (CT) datasets of 12 healthy adult Shetland ponies were performed and analysed. Linear measurements of head length and width were taken. Using semi-automatic segmentation, 3D-models of all sinus compartments were created. Volumetric measurement of the seven sinus compartments were conducted and statistical analysis was performed. Sinus volumes were compared between the left and right sinuses and the relation to age and head size was evaluated. RESULTS: Structure and shape of the paranasal sinus system in Shetland ponies was similar to that of large horses. All seven sinus compartments on each side of the head were identified (rostral maxillary sinus, ventral conchal sinus, caudal maxillary sinus, dorsal conchal sinus, middle conchal sinus, frontal sinus, sphenopalatine sinus). The existence of a bilateral cranial and a caudal system formed by a maxillary septum was visible in all 12 individuals. The volumetric sizes of the left and right sinuses did not differ significantly (p > 0.05). A positive correlation between the size of the paranasal sinuses and the head length was shown. A relation between sinus volumes and age could not be proved in adult ponies aged > six years. Communication between single sinus compartments was identified. Furthermore, communication with the nasal cavity over the nasomaxillary aperture (Apertura nasomaxillaris) and a common sinonasal channel (Canalis sinunasalis communis) as well as its splitting up into a rostral and a caudolateral channel could be seen. Examination of the sinonasal communication was challenging and only a descriptive evaluation was possible. CONCLUSIONS: Our findings concerning the size, shape and volumetric dimensions of Shetland pony CT images could help improve CT interpretation of abnormal clinical cases as well as aiding clinicians to develop and select appropriate instruments for medical inspection and treatments.

The difference in radiographic findings in the distal limbs of working Lipizzan horses, used for dressage or driving.

Introduction: Lameness originating from the distal limb is common in sport horses and can vary depending on the dynamics of movement and the surface, with differences in shoeing exacerbating this variability. Driving horses work primarily on hard surfaces (pavement), whereas dressage horses work primarily on soft surfaces (riding arenas with sand). Driving horses are traditionally shod with small fixed studs made of hard metal, which are attached to the horseshoe at 4 points, while dressage horses are shod with a simple horseshoe. We investigated the hypothesis that there is a difference in the pathological radiographic findings of the distal limbs between driving and dressage horses. The variability in the stable management and training program was minimized by including horses from the same farm. Methods: Twenty horses in a driving training program and 20 horses in a dressage program were included in the study. Radiographs of the both front feet were obtained and quantitatively evaluated for radiographic changes by three surgery/diagnostic imaging specialists. Interrater reliability was measured, and multivariate analysis was performed to compare differences in pathological radiographic findings of the distal limbs between the two groups. Results: Kendal's concordance coefficient indicated an agreement among raters (Kw ≠ 0) for all observations. Radiographic signs of degenerative joint disease of the distal interphalangeal joint were more common in the group of driving horses compared to dressage horses. Conclusion: Our hypothesis was confirmed, as there were significant pathological differences between groups in distal articular margin of middle phalanx, joint space narrowing, and irregular joint surface of the middle phalanx.

Caudal foot placement superior to toe elevation for navicular palmaroproximal-palmarodistal-oblique image quality.

BACKGROUND: Palmaroproximal-palmarodistal oblique (PaPr-PaDiO) radiographs are regularly obtained for a full evaluation of the navicular bone (NB). Despite their routine use, different acquisition techniques are described. OBJECTIVES: To determine optimal foot placement and beam angle for obtaining PaPr-PaDiO views. STUDY DESIGN: In vitro experiment. METHODS: A convenience sample of 26 disarticulated forelimbs were placed in six different positions using a leg press to mimic the weight-bearing position. In each position, navicular PaPr-PaDiO images were obtained with eight different beam angles. The resulting 1248 radiographs were graded for their diagnostic quality and the compacta spongiosa demarcation of the NB. RESULTS: Diagnostic quality and compacta-spongiosa demarcation was graded higher for feet positioned caudally and angle between 40° and 45°. Elevation of the toe significantly decreased the NB palmar border angle (elevated mean: 40.66, SD: 4.46, non-elevated mean: 42.06, SD: 4.70) (P < .01), but seemed to have no obvious positive influence on radiographs. MAIN LIMITATIONS: Using disarticulated legs could only mimic positions but, using a press, weight-bearing positions were replicated as closely as possible. The use of a convenience sample makes the results of the study exploratory only. CONCLUSIONS: Caudal foot placement seems to improve the image quality of the navicular PaPr-PaDiO view. The widely used standard beam angle of 45° appears to be the favourable angle for acquisition with a varied range of -5°. Elevation of the toe, standard in most commercially available navicular skyline cassette holders, does not influence the obtained image quality.

Approaches to standardising the magnetic resonance image analysis of equine tendon lesions.

Background: Low-field magnetic resonance imaging (MRI) has gained increasing importance to monitor equine tendon lesions. Comparing results between studies and cases is hampered, because image analysis approaches vary strongly. This study aimed to improve reliability, comparability and time efficiency of quantitative MRI image analysis. Methods: Induced tendon lesions were studied over a 24-week period with 10 follow-up MRI examinations. Signal intensities (SIs) of tendons, tendon lesions, cortical bone and background, as well as lesion cross-sectional areas (CSAs) were measured. Lesion SI standardisation with different formulas was evaluated, using histological findings as reference. Different types of region of interest (ROI) for lesion SI measurement were compared. Lesion CSA measurement at different levels was evaluated, using the calculated total lesion volume as reference. Subjective lesion identification and manual CSA and SI measurements were compared to an automated, algorithm-based approach. Results: Lesion SI standardised using a quotient of lesion and background or cortical bone SI, correlated best with histologically determined lesion severity. Lesion SI in circular ROIs correlated strongly with lesion SI in free-hand whole-lesion ROIs. The level of the maximum lesion CSA shifted over time; the CSA maximum correlated strongly with lesion volume. In sequences with short acquisition time, algorithm-based automated lesion detection showed almost perfect agreement with subjective lesion identification. Automated measurement of CSA and SI was also feasible, with stronger correlation and better agreement with the manually obtained data for the SI than for the CSA. Conclusion: Our study may provide guidance for MRI image analysis of tendon healing. Reliable image analysis can be performed time-efficiently, particularly regarding lesion SI quantification.

Presence and size of synovial masses within the navicular bursa correlate well between magnetic resonance imaging and bursoscopy and have a guarded prognosis.

BACKGROUND: Focal hyperintense lesions within the navicular bursa emanating from the dorsal border of the deep digital flexor tendon (DDFT) can be recognised on T1-weighted magnetic resonance images (MRI) and have been attributed to lameness in horses. Removal of these lesions, also referred to as synovial masses, by navicular bursoscopy is currently recommended. OBJECTIVES: To investigate the correlation between MRI and navicular bursoscopic findings. It is hypothesised that the prognosis following surgery is proportional to the size of the DDFT lesion. STUDY DESIGN: Retrospective analysis of clinical records. METHODS: Horses undergoing standing low-field MRI and navicular bursoscopy with >1 year follow-up were included. A grading system was developed to classify the size of synovial mass(es) and lesion(s) of the DDFT on MRI and at surgery. Generalised estimating equations were used to evaluate the association between MRI findings and surgery and between outcome and severity of the tendon injury. RESULTS: Fifty-nine horses presenting over a 15-year period (2006-2021) fulfilled inclusion criteria. Ninety navicular bursae were examined both on MRI and endoscopically. There was strong correlation between the size of synovial masses and tendon lesions on MRI and bursoscopy (p < 0.001, OR: 25.61, 95% CI 8.71-75.29 and p < 0.001, OR: 7.34, 95% CI 2.70-19.92, respectively). Size of tendon lesion and synovial mass had no impact on prognosis (p = 0.3, OR: 1, 95% CI 1-1 and p = 0.1, OR: 1, 95% CI 1-1, respectively), which was guarded (30.5% return to previous level of exercise). MAIN LIMITATIONS: Performance data for conservatively treated horses with MRI-detected synovial masses was not considered, nor was the effect of navicular bursal effusion. Horses were not randomly assigned to treatment protocols. CONCLUSION: There is good correlation between MRI and bursoscopic findings of DDFT lesions and synovial masses within the navicular bursa, with no false positives. Size of the synovial masses and DDFT lesions does not influence prognosis following navicular bursoscopy.

Characterization of Equine Chronic Tendon Lesions in Low- and High-Field Magnetic Resonance Imaging.

In equine medicine, experience regarding MRI of chronic tendon lesions is limited, and evidence on the suitability of different sequences in 3 T high-field MRI is scarce. Therefore, macroscopically healthy and altered tendons were examined by histology and in 0.27 T low- and 3 T high-field MRI, focusing on T1-weighted (T1w) sequences to visualize chronic lesions. In high-field MRI, tendons were positioned parallel (horizontal) and perpendicular (vertical) to the magnetic field, acknowledging the possible impact of the magic angle effect. The images were evaluated qualitatively and signal intensities were measured for quantitative analysis. Qualitative evaluation was consistent with the quantitative results, yet there were differences in lesion detection between the sequences. The low-field T1w GRE sequence and high-field T1w FLASH sequence with vertically positioned tendons displayed all tendon lesions. However, the horizontally scanned high-field T1w SE sequence failed to detect chronic tendon lesions. The agreement regarding tendon signal intensities was higher between high-field sequences scanned in the same orientation (horizontal or vertical) than between the same types of sequence (SE or FLASH), demonstrating the impact of tendon positioning. Vertical scanning was superior for diagnosis of the tendon lesions, suggesting that the magic angle effect plays a major role in detecting chronic tendon disease.

Measurement accuracy of foot conformation parameters on low-field magnetic resonance images in horses.

Foot imbalance and malalignment of the digits are common in horses. Angle and distance measurements performed on bones, joints and hoof wall on radiographs provide essential guidance for precise corrective trimming and shoeing. This study aimed to investigate, if selected standing low-field magnetic resonance (MR) images can be used to accurately measure dorsopalmar and lateromedial foot conformation parameters in comparison to the radiographic gold standard. Images of 100 horses referred for standing low-field MR examination were selected. Foot conformation angles and distances were measured and compared between radiographs and MR images. Measurements from most imaging sources were significantly different from each other. Moderate to high correlation of foot conformation angles between radiographs and MR images in the lateromedial and dorsopalmar planes was found, with exception of the proximal interphalangeal joint angle, where there was only moderate agreement between radiographs and the 5-plane MR pilot (0.47, P < .001) and between radiographs and the 3-plane MR pilot (0.4, P < .001), respectively. Measurement of foot conformation parameters from low-field MR images should be used with caution in clinical practice and acquisition of current foot radiographs immediately before or after MR examination should be considered to facilitate precise trimming and shoeing.

Retrospective analysis of oblique and straight distal sesamoidean ligament desmitis in 52 horses.

BACKGROUND: Injuries to the oblique (ODSL) or straight (SDSL) distal sesamoidean ligaments are a recognised cause of distal limb lameness in the horse. However, there are only limited publications addressing common diagnostic features and prognosis. OBJECTIVES: (a) Report findings on ultrasonography and standing low-field magnetic resonance imaging (sMRI) in horses with ODSL or SDSL injury; (b) Identify clinical variables associated with lesion type and (c) Identify factors associated with return to soundness in horses with ODSL or SDSL injury. STUDY DESIGN: Retrospective case series. METHODS: Horses with a primary diagnosis of ODSL or SDSL injury confirmed with a combination of diagnostic analgesia and detection of a lesion on imaging (ultrasonographic ± advanced imaging) were included. Return to soundness and performance follow-up data were obtained. RESULTS: Fifty-one horses were included. SDSL injuries were more common in the forelimb (13/21, 62%), while ODSL injuries had equal frequency in fore- (15/30, 50%) and hindlimbs (15/30, 50%). ODSL injuries were more likely than SDSL injuries to affect the proximal third of the ligament (OR =13; 95% CI 2.3-74.3; p = 0.004) and often presented with periligamentar swelling (20/30;67%) and focal pain (22/28;79%). Lesions were frequently detected using ultrasonography (35/42;83%) and sMRI examination (18/25;72%). Only 27/49 cases (55%) returned to soundness, with only 15/49 (31%) returning to intended use. There were no significant associations between outcome and clinical features or treatment. MAIN LIMITATIONS: There was no comparative "gold standard" to validate lesions such as high-field MRI or histopathology. CONCLUSIONS: In contrast to previous studies, ODSL and SDSL injuries were readily identified ultrasonographically using appropriate views, and with sMRI. Given the limited availability, cost and general anaesthetic risks associated with high-field MRI, more focus should be placed on optimising the ultrasonographic examination. Owners of affected horses should be informed of the guarded prognosis for return to full use.

Inter- and intra-observer agreement for grading radiographs of thoracolumbar spinous processes in healthy horses during a pre-purchase examination.

BACKGROUND: There is wide variability in radiographic grading systems in thoracolumbar spinous processes in horses. The aim of this study was to determine the agreement of grading different parameters, and combinations of those, in radiographs of the spinous processes of the equine thoracolumbar spine in the scope of a pre-purchase examination. We hypothesized that agreement is variable and interpretation of these radiographs is difficult. METHODS: Radiographs of the thoracolumbar spine of healthy horses (N = 100) were assessed by three observers. Spinous processes were separately graded for interspinous space width, modelling, radiopacities, radiolucencies and isolated opacities dorsally. Inter- and intra-observer agreement was assessed for individual and combinations of parameters. RESULTS: Agreement (inter- and intra-observer) was good for the following parameters: interspinous space width, isolated opacities dorsally, beak-shaped formations craniodorsally and modelling cranioventrally. The agreement increased slightly for a sum of specific parameters such as radiopacities, modelling, dorsal abnormalities and related abnormalities involving increased opacity, modelling and osseous cyst-like lesions. Agreement for the total radiographic abnormalities per back was moderate. CONCLUSIONS: Grading of thoracolumbar radiographs in horses without back pain showed good inter- and intra-observer agreement for specific parameters and these should be used in future grading of spinous processes. Limitations should be considered in pre-purchase examinations.

An anatomical study of the dorsal and ventral nasal conchal bullae and middle nasal conchae in normal Shetland ponies: Computed tomographic anatomical and morphometric findings.

Equine paranasal sinuses are susceptible to inflammation. Insufficient drainage through the nasal passages and meatus may lead to the accumulation of inspissated purulent discharge. Particularly in ponies, these anatomical structures are suspected to be relatively small. To date, there are no reports considering the morphology of nasal conchal bullae in small horse breeds such as Shetland ponies. The aim of the present study was to evaluate the size of the conchal bullae and the medial nasal conchae of Shetland ponies and their relation to the skull dimension using computed tomography. Reconstructed images of healthy adult heads of Shetland ponies were used. Linear skull measurements as well as two cranial indices of the head dimensions were taken. Length, width and height of the dorsal and ventral conchal bullae and the medial nasal conchae were measured in relation to the skull and compared with the data of skulls of large breed horses. The anatomical proportions of pony heads were characterized by a smaller cranial index and a greater nasal index than those of large breed horses. Shetland ponies showed a longer cranial length compared with the nasal length. Heads are consistently smaller, and the relationship of the bullae to the head length was also smaller than those measured in large breed horses. A negative correlation between the head and bullae size was found. In conclusion, this study suggests that Shetland ponies have distinguishing proportions of the head. These findings are relevant for clinical examination and surgical treatment of equine sinus disease in those breeds.

Effect of Scan Plane and Arthrography on Visibility and Interobserver Agreement of the Equine Distal Sesamoidean Impar Ligament on Magnetic Resonance Images.

In magnetic resonance imaging (MRI) examinations, moderate to severe changes of the distal sesamoidean impar ligament (DSIL) were found in horses with lameness localized to their feet. Histologic abnormalities were detected more commonly in lame horses. Because of its heterogeneity and small thickness, evaluation of the DSIL in MRI can be challenging. The aim of the study was to determine the optimal sequence and the ideal transverse perpendicular angle for visualization of the DSIL before and after arthrography of the distal interphalangeal joint (DIPJ). Twenty-five cadaver forelimbs were examined with low-field MRI. Sagittal, frontal, and three different angled transverse planes were obtained before and after arthrography of the DIPJ. All planes were acquired in T1w (weighted) Gradient Recall Echo (GRE), T2∗w GRE, T2w Fast Spin Echo (FSE), and Short Tau Inversion Recovery (STIR) FSE and visualization of the DSIL was scored by two observers. Visualization of the DSIL was best on sagittal T2w FSE and STIR FSE images. All transverse planes were inferior compared with sagittal sequences. After arthrography of the DIPJ, visualization of the DSIL origin improved in sagittal T2w FSE sequences, and agreement between observers increased for sagittal T2w FSE and STIR FSE images. Sagittal T2w FSE and STIR FSE images allowed good visualization of the DSIL in low-field MRI. Visualization of the DSIL did not improve for altered angled transverse sequences but increased with arthrography of the DIPJ. Subjective influence between different observers was found but decreased with DIPJ arthrography.

Variation in the MRI signal intensity of naturally occurring equine superficial digital flexor tendinopathies over a 12-month period.

BACKGROUND: Signal intensity (SI) of equine tendinopathies in MRI differs between the superficial digital flexor tendon (SDFT) and the deep digital flexor tendon (DDFT). In DDFT lesions, short tau inversion recovery (STIR) SI decreases earlier than T2-weighted (T2w) SI, while the latter decreases earlier in SDFT lesions, but long-term results using STIR sequences are lacking. METHODS: Standing MRI of eight horses with naturally occurring SDFT lesions was performed at the day of treatment as well as 2, 6 and 12 months after treatment. RESULTS: After 12 months, six horses were sound and showed complete resolution of increased SI in T2w fast spin echo (FSE) images, but increased SI was found in STIR images in three horses and persisted in T1w and T2*w gradient recall echo images of all horses. In contrast, hyperintense areas were still visible in the SDFT in T2w FSE images in two horses presenting with re-injury. In the six horses without re-injury, percentage of cross-sectional areas affected and SI decreased over time in all sequences. CONCLUSIONS: This study suggests that SI in naturally occurring SDFT lesions decreases earlier in T2w FSE than in STIR images, in contrast to the DDFT.

In Vivo Magic Angle Magnetic Resonance Imaging for Cell Tracking in Equine Low-Field MRI.

The magic angle effect increases the MRI signal of healthy tendon tissue and could be used for more detailed evaluation of tendon structure. Furthermore, it could support the discrimination of hypointense artefacts induced by contrast agents such as superparamagnetic iron oxide used for cell tracking. However, magic angle MRI of the equine superficial digital flexor tendon has not been accomplished in vivo in standing low-field MRI so far. The aim of this in vivo study was to evaluate the practicability of this magic angle technique and its benefit for tracking superparamagnetic iron oxide-labelled multipotent mesenchymal stromal cells. Six horses with induced tendinopathy in their forelimb superficial digital flexor tendons were injected locally either with superparamagnetic iron oxide-labelled multipotent mesenchymal stromal cells or serum. MRI included standard and magic angle image series in T1- and T2∗-weighted sequences performed at regular intervals. Image analysis comprised blinded evaluation and quantitative assessment of signal-to-noise ratio. The magic angle technique enhanced the tendon signal-to-noise ratio (P < 0.001). Hypointense artefacts were observable in the cell-injected superficial digital flexor tendons over 24 weeks and artefact signal-to-noise ratio differed significantly from tendon signal-to-noise ratio in the magic angle images (P < 0.001). Magic angle imaging of the equine superficial digital flexor tendon is feasible in standing low-field MRI. The current data demonstrate that the technique improves discrimination of superparamagnetic iron oxide-induced artefacts from the surrounding tendon tissue.

Longitudinal Cell Tracking and Simultaneous Monitoring of Tissue Regeneration after Cell Treatment of Natural Tendon Disease by Low-Field Magnetic Resonance Imaging.

Treatment of tendon disease with multipotent mesenchymal stromal cells (MSC) is a promising option to improve tissue regeneration. To elucidate the mechanisms by which MSC support regeneration, longitudinal tracking of MSC labelled with superparamagnetic iron oxide (SPIO) by magnetic resonance imaging (MRI) could provide important insight. Nine equine patients suffering from tendon disease were treated with SPIO-labelled or nonlabelled allogeneic umbilical cord-derived MSC by local injection. Labelling of MSC was confirmed by microscopy and MRI. All animals were subjected to clinical, ultrasonographical, and low-field MRI examinations before and directly after MSC application as well as 2, 4, and 8 weeks after MSC application. Hypointense artefacts with characteristically low signal intensity were identified at the site of injection of SPIO-MSC in T1- and T2 (∗) -weighted gradient echo MRI sequences. They were visible in all 7 cases treated with SPIO-MSC directly after injection, but not in the control cases treated with nonlabelled MSC. Furthermore, hypointense artefacts remained traceable within the damaged tendon tissue during the whole follow-up period in 5 out of 7 cases. Tendon healing could be monitored at the same time. Clinical and ultrasonographical findings as well as T2-weighted MRI series indicated a gradual improvement of tendon function and structure.

[Low-field magnetic resonance imaging of penetrating hoof injuries in 10 horses]. / Niederfeld-magnetresonanztomographische Untersuchung durchdringender Hufverletzungen bei 10 Pferden.

OBJECTIVE: The aim of the present study was to verify the diagnostic validity of low-field magnetic-resonance-imaging (MRI) findings in septic diseases of the foot region following penetrating sole injuries caused by nails. MATERIALS AND METHODS: MRI examinations were performed in 10 horses with injuries in the foot region. The diagnostic findings were validated by conventional methods (clinical, surgical, radiological, sonographic, and computed tomographic findings and/or post-mortem histological examination). RESULTS: Navicular bone involvement was revealed most accurately, with a high degree of predictability, and was best detected by fat-suppressed T2 or short-TI inversion recovery (STIR) sequences. MRI examinations of defects in the deep digital flexor tendon showed a high level of sensitivity, but these findings were less specific than changes to the navicular bone. They could be best reproduced in transverse T2-weighted fast spin echo sequences (T2w FSE). The penetration tract was recognisable in all cases and in all planes, and the T2w FSE proved to be very suitable for diagnosis. Septic bursitis was revealed least accurately by MRI. Bursal disease was best recognised in the sagittal plane. CONCLUSION AND CLINICAL RELEVANCE: MRI is a reliable method for confirming the diagnosis of diseases in the foot region after injuries caused by foreign bodies, particularly nails. A transverse T2w FSE is best suited for demonstrating a penetration tract and tendon damage. Visualisation of the penetration tract and secondary reactions of the navicular bone are crucial for diagnosing bursitis. Fat-suppressed sequences can clearly show bone involvement when the penetration tract has not reached the bone. The cases described illustrate that MRI is an appropriate method for evaluating puncture wounds in the foot region. Only MRI allows for intravital assessment of various structures within the hoof capsule. This information is essential for deciding upon targeted therapy while avoiding unnecessary therapies.

Long-Term Cell Tracking Following Local Injection of Mesenchymal Stromal Cells in the Equine Model of Induced Tendon Disease.

Tendon disease has been treated with multipotent mesenchymal stromal cells (MSCs) in the equine large-animal model with promising success. The aim of this study was to gain more insight into the fate and biodistribution of MSCs after local application into tendon lesions by long-term cell tracking in this large-animal model. Superficial digital flexor tendon lesions were induced in all limbs in six horses and injected with 10106 Molday ION Rhodamine B-labeled MSCs suspended in serum or serum alone. Follow-up was performed using low-field magnetic resonance imaging (MRI), flow cytometry, and histology. Cell tracking based on the hypointense artifacts induced by the superparamagnetic iron oxide (SPIO) labeling agent in MRI as well as based on Rhodamine B fluorescence was feasible. However, Prussian blue staining for assessment of histology was not entirely specific for SPIO. Labeled cells could be traced at their injection site by MRI as well as histology for the whole follow-up period of 24 weeks. Although the numbers of labeled cells within the injected tendon lesions decreased over time, part of the applied cells appeared to remain viable and integrated within the injured tissue. Furthermore, small numbers of labeled cells were identified in peripheral blood within the first 24 h after cell injection and could also be found until week 24 within the contralateral control tendon lesions that had been injected with serum. The present findings unveil details on MSC biodistribution and persistence after their local application, which are of clinical relevance with regard to MSC safety and mechanisms of action.

Freeze-thaw cycles enhance decellularization of large tendons.

The use of decellularized tendon tissue as a scaffold for tendon tissue engineering provides great opportunities for future clinical and current research applications. The aim of this study was to assess the effect of repetitive freeze-thaw cycles and two different detergents, t-octyl-phenoxypolyethoxyethanol (Triton X-100) and sodium dodecyl sulfate (SDS), on decellularization effectiveness and cytocompatibility in large tendons. Freshly collected equine superficial and deep digital flexor tendons were subjected to decellularization according to four different protocols (1 and 2: freeze-thaw cycles combined with either Triton X-100 or SDS; 3 and 4: Triton X-100 or SDS). Decellularization effectiveness was assessed based on the reduction of vital cell counts, histologically visible nuclei, and DNA content. Transmission electron microscopy was performed to evaluate cellular and extracellular matrix integrity. Further, cytocompatibility of scaffolds that had been decellularized according to the protocols including freeze-thaw cycles (protocols 1 and 2) was assessed by seeding the scaffolds with superparamagnetic iron oxide labeled mesenchymal stromal cells and monitoring the cells histologically and by magnetic resonance imaging for two weeks. Decellularization was significantly more effective when using the protocols including freeze-thaw cycles, leaving only roughly 1% residual nuclei and 20% residual DNA, whereas samples that had not undergone additional freeze-thaw cycles contained roughly 20% residual nuclei and 40% residual DNA. No morphological extracellular matrix alterations due to decellularization could be observed. Scaffolds prepared by both protocols including freeze-thaw cycles were cytocompatible, but the cell distribution into the scaffold tended to be better in scaffolds that had been decellularized using freeze-thaw cycles combined with Triton X-100 instead of SDS.

Morphometrical dimensions of the sheep thoracolumbar vertebrae as seen on digitised CT images.

The sheep spine is widely used as a model for preclinical research in human medicine to test new spinal implants and surgical procedures. Therefore, precise morphometric data are needed. The present study aimed to provide computed tomographic (CT) morphometry of sheep thoracolumbar spine. Five adult normal Merino sheep were included in this study. Sheep were anaesthetised and positioned in sternal recumbency. Subsequently, transverse and sagittal images were obtained using a multi-detector-row helical CT scanner. Measurements of the vertebral bodies, pedicles, intervertebral disc and transverse processes were performed with dedicated software. Vertebral bodies and the spinal canal were wider than they were deep, most obviously in the lumbar vertebrae. The intervertebral discs were as much as 57.4% thicker in the lumbar than in the thoracic spine. The pedicles were higher and longer than they were wide over the entire thoracolumbar spine. In conclusion, the generated data can serve as a CT reference for the ovine thoracolumbar spine and may be helpful in using sheep spine as a model for human spinal research.

Is sheep lumbar spine a suitable alternative model for human spinal researches? Morphometrical comparison study.

Sheep are commonly used as a model for human spinal orthopaedic research due to their similarity in morphological and biomechanical features. This study aimed to document the volumes of vertebral bodies and compare the generated results as well as morphometry of the sheep lumbar spine to human published data. For this purpose, computed tomography scans were carried out on five adult Merino sheep under general anaesthesia. Transverse 5 mm thick images were acquired from L1 to L6 using a multi-detector-row helical CT scanner. Volume measurements were performed with dedicated software. Four spinal indices and Pavlov's ratio were calculated. Thereafter, the generated data were compared to published literature on humans. The mean vertebral body volume showed an increase towards the caudal vertebrae, but there were no significant differences between the vertebral levels (P>0.05). Compared to humans, sheep vertebral body volumes were 48.6% smaller. The comparison of absolute values between both species revealed that sheep had smaller, longer and narrower vertebral bodies, thinner intervertebral discs, narrower spinal canal, longer transverse processes, shorter dorsal spinous processes and narrower, higher pedicles with more lateral angulations. The comparison of the spinal indices showed a good similarity to human in terms of the vertebral endplates and spinal canal. The results of this study may be helpful for using the sheep as a model for human orthopaedic spinal research if anatomical differences are taken into account.