Disease and its progression

INTRODUCTION

Background:

Musculoskeletal system is an organ system that includes bone and cartilage, muscles, tendons, ligaments and joints. Low back spine injuries can be fractures which affect the bone, herniation which affect the disk, sprain which affects ligaments or muscles. (Truumees, 2007). Common injuries of the spine are associated with falls from a height and motor vehicle accidents. When a force is exerted to the lumbar spine and exceeds the stability and strength of the spinal column it results in a fracture. (Nadalo, 2007). In trauma this can result in impingement of the nerves and can cause cauda equina syndrome. Cauda equina syndrome involves weakness in the legs, bladder paralysis and bowel. (Larson & Maiman, 1999).

According to Truumees 2007, there is a range of fractures that are linked with the spine. These range from compression fractures, where the bone collapses to when pieces of bone explode into the tissue known as burst fractures. Fracture dislocations are the worst as the bones break and slide away from each other, ligaments are torn as well. Normally these situations require surgery.

Primary imaging protocol for investigating spinal pathology comprises conventional radiography, CT, and MRI. (Kim, 2009).

Anatomy region:

The spinal cord extends from the foramen magnum to L1-L2 disc space. It is continuous with the medulla oblongata and terminates in the conus medullaris. Below this level the nerve roots running inferiorly are collectively called the cauda equina. The cauda equina runs within the spinal canal, which is bordered interiorly by the vertebral bodies and posterior by the dorsal bony arch, (Vaccaro, 2003).

The membranous layers covering the spinal cord are referred to as the meninges. The meninges consist of three layers; the Dura, arachnoid and pia mater. The Dura is attached interiorly to the posterior longitudinal ligament. The pia mater is composed of a superficial layer epi-pia and a deep layer pia-glia, (Clark & Letts, 2001).

The first changes evident in spinal cord anatomy following traumatic injury are punctate haemorrhages in the gray and white matter. The movement of the lumbar spine is largely confined to flexion and extension with a minor degree of rotation. The region between the superior articular process and the lamina is the pars interaticularis, (Nadalo, 2007).

Pathophysiology

As indicated above the fractures of the lumbar spine occur any time the combined forces of compression, distraction, and rotation exceed the strength of the spinal column. The predominant force determines the nature of the fracture dislocation. It is common that axial rotation occurs in the upper lumbar region. With great rotational forces, subluxation and a combined fracture occur and this results with the injury to the conus medullaris. Compression of the conus medullaris and nerve roots results in weakness and pain, (Clark & Letts, 2001).

Any injury that involves the spinal cord is serious. If the conus medullaris is injured patients will have problems with the bowel, bladder and sexual function. A group of individual nerves called cauda equina are found below the conus medullaris. Pressure on these nerves can cause long term leg weakness, bowel and bladder problems therefore is treated as an emergency, (Truumees, 2007).

Spinal intervertebral disc distribute the forces that travel through the whole spine. They lie between two adjacent vertebral bodies and act as shock absorbers. Disc herniation or raptures occur when the inner nucleus pulposus ruptures through the weakened annulus (outer layers) of the disc. Disc herniation in the lower back can be due to trauma. Symptoms include lower back pain, leg pain, numbness or weakening and tingling of one or both legs. In serious cases nerves to the bowel and bladder can be compressed leading to incontinence, (Knaub, 2007).

Compression from large central lumbar disc herniation at L4/5 and L5/S1 level is a common cause of cauda equina. Thickening of the ligamentum flavum and degenerative changes as a result of spinal stenosis is another cause of cauda equina. Spinal injury with fractures or subluxation is another less common cause. Compression can also be caused by spinal neoplasm of metastatic lesions, (Lavy, James, Wilson-MacDonald & Fairbank, 2009).

The symptoms are less predictive although they are associated with the impairment of the bladder, bowel and sexual function and to some extend perianal (saddle numbness). Cauda equina results from dysfunction of many sacral and lumbar nerve roots. It is also believed to be caused by interverbral disc herniation. Loss of perianal sensory and sphincter disturbance and this could be with or without urinary retention. Complete cauda equina has established urinary retention or overflow and incomplete cauda equina there is reduced urinary sensation, (Lavy, James, Wilson-MacDonald & Fairbank, 2009). With disc herniation, if the degenerative process progresses, small circumferential fissures develop in the fibrosus, which later coalesce to form radial, tear. Distinction between focal extrusion of disc material and a circumferential enlargement is important, as the former is typically treated surgically, whereas the later can be treated conservatively. Disc herniation refers to a focal, incomplete extension of the contents of the nucleus pulposus through an incomplete tear of the annulus fibrosus, (Lee, 2006).

IMAGING INVESTIGATION

Imaging of the spine can be performed by conventional radiography (CR), ultrasound (US), computerised tomography (CT), digital subtraction angiography (DSA) or magnetic resonance imaging (MRI). With conventional radiography, anteroposterior (AP), lateral and oblique projections of the vertebral column should be obtained. CR provide valuable information regarding bony structures of the spinal column, facet joints, disc spaces, and foramina while limited information regarding the paraspinal soft tissues can be obtained. The spinal cord is well seen with US in the first few months of life, (Browner, 2003).

Multislice CT demonstrates the vertebral column, vascular structures and disc very well together with better visualisation of the spinal cord and paraspinal soft tissues while conventional CT demonstrates the vertebral body and posterior elements very well with only limited visualisation of the soft tissue and spinal cord. DSA is still the gold standard for imaging and interventional procedures of spinal vascular structures. DSA is time consuming, invasive technique that has the disadvantages of high levels of radiation. MRI imaging has become the modality of choice for imaging of the spinal cord, thecal sac, nerve roots, epidural space, vascular structures, neural foramina, vertebral body, intervertebral discs, facet joints, spinal ligaments and paraspinal soft tissue, (Goethem, Hauwe & Parizel, 2007).

Trauma patients with pain in the lumbar sacral region require lateral and AP radiologic views. If these studies are negative but clinical symptoms are impressive, further imaging by CT is indicated. CT is helpful in characterising complex injuries such as fracture dislocations and in distinguishing burst fractures from anterior compression fractures. Acute onset of radicular symptoms after acute trauma may warrant CTM or MRI to exclude acute intervertebral disc herniation, (Browner, 2003).

Diagnostic value including image appearances

PLAIN FILM RAD OF THE LUMBAR SPINE:

Radiographic evaluation starts with the AP and lateral radiographs. When clinically inappropriate a horizontal beam with the patient recumbent is taken instead of the lateral position. Initial evaluation of the overall alignment of the thoracolumbar junction and lumbar spine is clearly assessed with a lateral radiography taken in the supine position. Many fractures demonstrate not only a comminution of the vertebral body but also a local area of kyphosis. Oblique projections should be obtained only when the AP and lateral radiographs are inconsistent with the clinical evaluation. The patient's condition must also allow the rotation into the oblique position. The oblique projections provide excellent visualisation of the pars interaticularis and the facet joints, (Browner, 2003). When viewed in an oblique projection, the outline of the facets and the pars interaticularis appear like the neck of a Scottie dog, (Nadalo, 2007). Soft tissue swelling may indicate a fracture even if the fracture is not directly visualized. Structures that are best seen on the oblique views include the transverse process and pedicle on the dependent side and the pars interaticularis.

Plain X ray is advantageous as it is readily available and inexpensive. It also provide a rapid assessment of a specific spinal region and depending on the patient ability, weight bearing and dynamic views maybe obtained. Conventional radiography is useful in confirming normal osseous structures, vertebral alignment and structural integrity of the spine, (Devlin, 2003).

On the contrary plain x ray has low sensitivity and specificity in identifying symptomatic spinal pathology. It cannot visualise neural structures and other soft tissue lesions (disc herniation). It is limited in the diagnosis of early stage tumour or infection because significant bone destruction must occur before a radiographic abnormality is detectable, (Devlin, 2003).

CT OF THE SPINE

CT allows images to be obtained in any plane to demonstrate the pathology in question. Multi-planar computed tomography is CT with routinely obtained sagittal and coronal reformatted images. Multi-planar CT including three dimensional CT is currently the imaging technique of choice for spinal injury. The value of CT is in the axial image, which demonstrates the neural canal and the relationship of the fracture fragments to the canal. Axial data obtained in the supine patient are converted electronically into images displayed in the sagittal and coronal planes, without requiring movement of the patient. (Browner, 2003)

Thin-section axial CT scanning with a bone algorithm is the single most sensitive means by which to diagnose fractures of the lumbar spine. Routine helical CT scans of the lumbar spine are valuable because multi-section CT scanners can generate high-resolution spinal images, even during a primary multi-systemic evaluation for trauma. Good-quality CT images can be used to identify more lumbar spine injuries than conventional radiographic studies, (Oskouian, & Johnson, 2002).

CT is known to be the best for bone anatomy assessment and the use of multiple cross sectional images which can be reconstructed to provide images in orthogonal planes is an added advantage. It is the main substitute when MRI is contraindicated, (Devlin, 2003).

The disadvantages of CT follow the exposure to ionizing radiation. It provides poor delineation of neural elements and adjacent structures. Ligaments, disc, dural sac, and nerve roots appear as different shades of gray. Significant pathology can be missed. Sagittal images are not routinely reconstructed at many institutions, (Devlin, 2003).

MRI OF SPECIFIC ACUTE SPINE INJURY:

MRI is unique in its ability to detect acute injury to the spinal cord. Fat appears bright on T1 images and less bright on T2 images. T1 images are good for evaluating structures that contain fat, haemorrhage or proteinaceous fluid as they demonstrate high signal. T2 images are weighted towards water. Water appears bright on T2 images and dark on T1 images. T2 images are most useful in contrasting normal and abnormal anatomy, (Devlin, 2003).

Atlas 2008, suggest that cord odema appears isointense in relation to the normal spinal cord on T1-weighted spin echo images but becomes brighter than normal spinal cord on T2-weighted image sequences. MRI signals have the ability to identify the histopathology of acute spinal cord injury. MRI depicts normal ligaments as regions of low signal intensity because of lack of mobile hydrogen. Disruption of the ligament is seen on MRI scans as an abrupt interruption of the low signal, ligament attenuation or stretching of ligament, association of a torn ligament with an attached avulsed bone fragment, (Browner, 2003).

The focus is usually on spinal structures when interpreting spine MRI examinations and only the routine sagittal and axial images are used. Coronal scout images are acquired for localisation purpose before each routine lumbar spine MRI examination. This routine usually includes the hip joints and proximal femurs, (Lavelle & Bell, 2007).

Acute intervertebral disc herniation may accompany fractures or dislocations or may occur as an isolated lesion. If the disc impinges on the spinal cord or roots, a neurologic injury may result. MRI demonstration of a single-level acute intervertebral disc herniation is crucial in surgical management in spinal trauma to optimise neurologic recovery, (Browner, 2003).

Lumbar spine MRI can demonstrate many vertebral fractures and most abnormalities of alignment. MRI is superior to CT in the identification of indirect signs of a fracture such as pre-cervical edema or haemorrhage, epidural bleeding, and sprains of the paraspinal and intra-spinal ligaments. Associated injuries to intracranial structures are evaluated better by using MRIs than by using CT images, (Jarvik, Bowen & Ross, 2001).

MRI avoids ionizing radiation and provides imaging in orthogonal planes which makes it advantageous over other modalities. It can be used to visualise an entire spinal region and avoids missed pathology at transition zones between adjacent spinal regions. It also provides exquisite soft tissue detail and excellent visualisation of intrathecal neural elements. MRI is sensitive to marrow abnormalities, (Atlas, 2008).

Contrary MRI does not define osseous anatomy as well as CT. Implanted devices are contraindications to MRI and claustrophobic patients may have difficulty because of the small diameter of the imaging machine, (Devlin, 2003).

Contribution to management and treatment of the disease (including consideration of patient issues and the wider context of healthcare provision)

Treatment and Management:

The principal treatment for unstable lumbar spine fractures is surgical fixation with spinal canal decompression as needed. A posterior approach involves pedicular fixation in which 2 segments are fused. The procedure results in both fracture reduction and fixation. The injured vertebra is grafted through the pedicle. Clearance of bone fragments from within the spinal canal is an important goal for most surgical approaches to lumbar spine fractures. Patients with complete paraplegia can be expected to remain unchanged.

As for cauda equina syndrome surgical decompression is recommended after confirmation by MRI imaging of reversible cause of pressure. (Lavy, James, Wilson-MacDonald & Fairbank, 2009).

Research/Developments within diagnostic imaging (contributing to the above)

New MR imaging techniques such as diffusion (DWI), perfusion (PWI), functional imaging (FMRI) and magnetic resonance spectroscopy (MRS) provide more specific, detailed and physiological information about the spine and spinal cord and also enable quantitative evaluation. Contrast enhanced (high dose) spinal MRA is a very promising technique, particularly for screening examinations of the spinal veins and arteries. (Goethem, Hauwe & Parizel, 2007).

The improvements in CT technology, introduced with spiral CT and the newer multi-detector array systems create the potential for CT to provide screening of the thoracic and lumbar spine as part of a routine thoracic cavity and abdominal-pelvic CT study in a multiple trauma patient. Single-slice or spiral CT used in conjunction with scout AP and lateral radiographs may ultimately provide more accurate identification of lumbosacral injuries than is achieved with conventional radiography, (Browner, 2003).

The development of the multi-slice CT technology with 0.5 second gantry rotation allows up to eight axial images to be acquired per second is expected to expand to more images per second in the near future. Addition of more detector arrays is anticipated to lead to further increases in the speed of image acquisition and improvements in image quality, (Browner, 2003).

Bone scan using RNI and additional tests will include Bone densitometry. Dual energy x-ray absorptiometry (DEXA) is used to assess bone mass

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