K. Gerlach

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 Pavlovs 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.

Magnetic Resonance Imaging and Cross‐Sectional Anatomy of the Normal Bovine Tarsus

With 13 figures and 1 table

Magnetic resonance imaging of pulp in normal and diseased equine cheek teeth.

A retrospective analysis of 619 upper and lower cheek teeth from 62 horses was performed. Based on clinical findings, as well as radiographic and magnetic resonance (MR) imaging findings, the teeth were classified into five groups. There were 20 teeth with abnormal MR imaging signals as well as clinical alterations and 599 healthy teeth. Using MR imaging, the appearance of pulp in diseased and disease-free teeth was compared, and the appearance of abnormal pulp was studied. Subsequently, the ability of MR imaging to diagnose pulpitis and pulp necrosis in teeth with normal external appearance was investigated. In horses with clinically verified dental disease, abnormal MR imaging findings were confirmed in the pulp of all affected teeth. An enlarged blurred pulp image with a lower signal intensity was observed only in clinically diseased teeth and was a reliable criterion for diagnosing dental disease on MR imaging. On the other hand, partial or complete absence of pulp in all MR imaging sequences was observed in both diseased and nondiseased teeth. These data demonstrate that pulp changes in equine cheek teeth can be evaluated using MR imaging.

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.

Computed Tomography and Cross-sectional Anatomy of the Normal Dromedary Camel Tarsus (One Humped Camel)

The purpose of this study was to provide a detailed computed tomographic (CT) anatomic reference for the dromedary camel tarsus. Six cadaver pelvic limbs, obtained from three clinically and radiographically sound dromedary camels, were scanned in both soft tissue and bone windows starting from the calcaneal tuber towards the proximal metatarsus. Limbs were frozen at −20°C and sectioned transversely via an electric bone saw. The CT images were evaluated and correlated with their corresponding cryosections. The resulting images provided detailed anatomic features for bones, joints and soft tissue components of the tarsus and are intended to serve as a basic reference for the CT scanning of the dromedary camel tarsal pathology.

THE INFLUENCE OF TEMPERATURE AND AGE ON THE T1 RELAXATION TIME OF THE EQUINE DISTAL LIMB

The extent of fat suppression using short tau inversion recovery (STIR) imaging is variable between horses. Our aim was to determine if patients age and/or hoof temperature have an influence on the T(1) relaxation time of bone marrow in the equine distal limb, thereby affecting the suppression of fat signal. Magnetic resonance imaging was conducted on standing horses and cadaver samples using a low-field magnet (0.27 T). The hoof temperature was measured at the lateral side of the coronary band. A modified inversion recovery fast spin-echo (IR-FSE) sequence was used to measure the signal intensity for a range of inversion times (TIs) at six different regions of interest (ROI): (1) distal aspect of the proximal phalanx, (2) proximal aspect of the middle phalanx, (3) distal aspect of the middle phalanx, (4) navicular bone, (5) proximal aspect of the distal phalanx, and (6) distal aspect of the distal phalanx. The T(1) of the bone marrow in the equine distal limb was calculated from the results and was found to increase by 3.13 ± 0.08 (SE) ms/°C. There was no significant effect of age (2-16 years) but the T(1) values measured from the limbs of young (< 1 year) animals were considerably longer (32.6 ± 1.7 (SE) ms). Similar effects of temperature and age were found for all measured ROIs but there were significant differences in the mean values of T(1) , ranging from +7.7 (distal aspect of the distal phalanx) to -13.2 ms (distal aspect of the proximal phalanx).

Parapagus Conjoined Twin Calf: A Case Study – Focused on CT and Cardiac Abnormalities

Congenital duplication anomalies occasionally occur in both humans and animals. Although various forms of classification of these conjoined twins exist, each case should be considered as an individual. In the case study presented a Holstein Frisian calf, born alive after 281 days of normal gravidity was investigated by computed tomography (CT) and subsequent dissection. The calf could be classified as a parapagus dicephalus tetrabrachius. It exhibited two heads each of them with a complete cervical spine leading to a complete thoracic and lumbar spine and separate tails. Looking at the point of fusion, the twin was conjoined in the ventrolateral thoracic part of the body. The calf had two thoraces with four forelimbs and two pelvic limbs on a single pelvis. As two heads and thoraces were present, beginning at the oral cavity, two intestinal systems were observable leading to a fusion point at the ascending part of the duodenum been continued caudally as a single system. Within each thorax, two lungs and a heart were present. However, only the heart in the left thorax was normal shape, exhibiting a strong myocardium and increased size. In contrast, the heart within the right thorax was considerably smaller, round shaped, and it appeared to be spongy and not fully developed during the foetal period. Commonly, classification of conjoined twins is only based on the appearance of the skeletal system. However, in the case presented, the point of fusion of the skeletal system did not allow conclusions regarding the intestinal or cardiovascular system.

Computed Tomography of the Normal Bovine Tarsus

The objective of this study was to provide a detailed multiplanar computed tomographic (CT) anatomic reference for the bovine tarsus. The tarsal regions from twelve healthy adult cow cadavers were scanned in both soft and bone windows via a 16‐slice multidetector CT scanner. Tarsi were frozen at −20o C and sectioned to 10‐mm‐thick slices in transverse, dorsal and sagittal planes respecting the imaging protocol. The frozen sections were cleaned and then photographed. Anatomic structures were identified, labelled and compared with the corresponding CT images. The sagittal plane was indispensable for evaluation of bone contours, the dorsal plane was valuable in examination of the collateral ligaments, and both were beneficial for assessment of the tarsal joint articulations. CT images allowed excellent delineation between the cortex and medulla of bones, and the trabecular structure was clearly depicted. The tarsal soft tissues showed variable shades of grey, and the synovial fluid was the lowest attenuated structure. This study provided full assessment of the clinically relevant anatomic structures of the bovine tarsal joint. This technique may be of value when results from other diagnostic imaging techniques are indecisive. Images presented in this study should serve as a basic CT reference and assist in the interpretation of various bovine tarsal pathology.

Quantitative evaluation of bone scintigraphy of the spinous processes of the equine thoracic spine at different times after administering ⁹⁹mTc-hydroxymethylene-diphosphonate.

Scintigraphic examination of the thoracic spine is well documented. However, there is limited information about the effects of time on image quality in the period following injection of radionuclide. This study aimed to determine the optimal time point after injection of 99mTc-HDP (hydroxymethylene-diphosphonate) to achieve scintigraphic images with the best possible contrast and adequate count rates. Scintigraphic images of the thoracic spine of 21 horses were acquired two, four and six hours after administering 99mTc-HDP. Eight regions of interest were drawn in the images, four in the spinous processes and four in the adjacent soft tissue. The bone uptake, soft tissue uptake and the bone-to-soft tissue ratio were determined and compared between the different time points. Total count rates decreased with time after injection, but were at least as high as 150,000 counts per image at every time point after injection. The bone-to-soft tissue ratio was significantly higher for the images acquired after six hours compared to those acquired after two and four hours (P<0.01). Delayed scintigraphic examinations of the spinous processes of the equine thoracic spine achieved images with high contrast and sufficient count rates. Therefore, the scintigraphic examination of the equine thoracic spine is recommended to be done four to six hours after injecting 99mTc-HDP. However, additional studies should be performed to determine the effect of delayed image acquisition compared to images taken after three hours on the detectability of lesions in other parts of the thoracic spine and the soft tissue.

Normal Radiographic and Ultrasonographic Appearance of the Adult Dromedary Camel Tarsus (One Humped Camel)

Six cadaver pelvic limbs were obtained from clinically sound dromedary camels and examined radiographically and ultrasonographically using a 7.5 MHz convex transducer. Radiographic examination was performed in dorsoplantar, lateromedial, dorsolateral‐plantaromedial oblique and plantarolateral‐dorsomedial oblique projections, and the bony structures and articulations of the tarsal joint were outlined. The tarsus was ultrasonographically investigated in four planes (dorsal, medial, lateral and plantar), and each plane was scrutinized in four levels (calcaneal tuber, tibial malleoli, base of calcaneus and proximal end of metatarsus) in both transverse and longitudinal views. Limbs were examined grossly, frozen at −20°C and sectioned. Radiographic and ultrasonographic findings correlated well with the gross anatomy and frozen sections. The normal appearance of bony and soft structures of the tarsus described in this study provided basic reference data for ultrasonographic and radiographic investigations of tarsal disorders in the dromedary camel.