Radiologic landmark accuracy for optimum coronal placement of total disc arthroplasty in the lumbar spine

OBJECTIVE: This study was performed to determine which of the radiographic markers visible on an anteroposterior (AP) radiograph of the spine-the vertebral body, the pedicles, and the spinous process-provided the most accurate guide to correctly placing an intervertebral disc replacement in the coronal midline. METHOD: The coronal midline was defined as the perpendicular bisector of a line drawn between the midpoints of the two facet joints. Axial CT images were reconstructed from 35 abdominal and renal computed tomograms to compare how consistently the midpoints of the above structures fell on the coronal midline. RESULTS: The mean distance (SD) from the vertebral body midpoint, the interpedicular midpoint, and the spinous process midpoint from the coronal midline, respectively, were 0.55 mm (SD 0.45 mm), 0.19 mm (SD 0.40 mm), and 1.30 mm (SD 1.30 mm). Sixteen percent of the distances from the coronal midline to the spinous process midpoint were greater than or equal to 3 mm compared with 0% of the distances to the interpedicular midpoint or the vertebral body midpoint. CONCLUSIONS: We concluded that the interpedicular midpoint is the most accurate guide to the coronal midline. We recommend that this landmark be used in preference to the spinous processes or the midpoint of the vertebral bodies when placing the implant in intervertebral disc arthroplasty.     

The optimum concentration for epidural fentanyl

A randomised, double-blind study comparing a variety of different concentrations of fentanyl with and without 1:200 000 adrenaline is described. It was shown that the quality and duration of analgesia with epidural fentanyl was concentration-dependent below 10 micrograms/ml, but that the addition of adrenaline abolished this phenomenon. The rate of failure to achieve any analgesia was very high with the more dilute solutions, but adrenaline reversed this problem. In general the incidences of side effects were related to the concentrations of fentanyl used and apart from itching, the incidences of these side effects were reduced by the addition of adrenaline.     

The spine in osteogenesis imperfecta

The natural history and treatment of spinal deformity is presented in light of the radiographic severity of the disease. The radiographic findings are grouped according to the changes over time and are prognostically significant for ambulation, spinal deformity, and life span.     

The spine in diastrophic dysplasia

Diastrophic dysplasia is an autosomal recessive disorder of the skeleton, characterized by disproportionate short stature, generalized joint deformities, club feet, deformed ear pinnae, and, frequently, spinal deformity and cleft palate. Diastrophic dysplasia is more common in Finland than elsewhere. We studied 101 patients with an age range from newborns to 79 years to find out the frequency and type of spinal deformities, the early signs of progressive cases, and to follow the natural history of the disease. In the follow-up study, 17 patients were under 10 years, 21 under 21 years, and 63 over 21 years of age. One-third of the patients had cervical kyphosis; in the most severe case the kyphosis was 180 degrees and led to quadriplegia during anesthesia. In three patients, cervical kyphosis resolved spontaneously before the age of 5 years. The overall frequency of scoliosis was 37%; 49% in women and 22% in men. Only 13 patients had curves greater than 50 degrees; these curves constituted distinct rotation at the apex from the early evolution of the curve. The early signs of severe curves were detectable at the age of 2 to 4 years. Only two patients were operated on because of scoliosis; one with fusion in situ and the other instrumented with the pediatric Cotrel-Dubousset instrumentation. Three patients had a brace, which did not prevent the progression of the curve. Symptoms referring to a narrow spinal canal were registered in four patients, two of which were operated on; a lumbar posterior decompressive procedure was made at adult age.     

The cervical spine in hemophilia

Fifty-three patients with known hemophilia A or B were retrospectively reviewed to determine the incidence of cervical spine involvement. Twenty-five were examined prospectively, including a detailed history and physical examination and cervical spine roentgenograms consisting of an AP and lateral flexion-extension series. All roentgenograms were reviewed by a board-certified radiologist. The mean age of patients in both groups was 25.4 years (range, eight to 54 years). In the retrospective review, no patients were noted to have complaints referable to the cervical spine, although five patients had prior trauma to the cervical spine. In the prospective study, 8 of 25 patients complained of intermittent neck discomfort and 9 of 25 had restricted lateral rotation and/or lateral flexion. No patient had radicular symptoms or objective neurologic deficits. Roentgenograms showed abnormalities in 13 of 25 patients. Ten patients (aged 19 to 54 years; mean, 32 years) showed cystic changes or endplate irregularity within one or more vertebral bodies. Two patients, aged 15 to 19 years, had an increased atlanto-dens interval of 5 mm (normal, 3 mm). No odontoid erosion was noted. No correlation was found between the severity of peripheral involvement and the cervical spine roentgenograms. Occult instability of the cervical spine is discussed, along with ramifications for patients with hemophilia.     

The aging of the spine

Summary In the strictest sense of the word, the so-called aging process of the spine develops as a natural age-related response to the dislocation of the tissues, which occurs from adulthood. These often clinically subtle degenerative changes are able to alter the mechanical properties and the anatomical structures of the spine. This dysfunction may entail a destabilization and sometimes lead to spinal instability. The various degenerative injuries to the elements stabilizing the spine, including the vertebra, the spinal motion segment and muscles, may cause segment injuries that are likely to affect the flexibility and the stability of the spine, thereby altering its curvatures. Destabilization worsens progressively as the anatomic structures keep deteriorating. Degenerative lesions and destabilization can endure and experience à transition into degenerative spondylolisthesis and scoliosis. But more often than not a spinal ankylosis—i.e. amending of the degenerative process by restabilization-can be established. Spinal ankylosis can develop in the aftermath of a destabilization but in most cases it does not develop secondary to any destabilization.     

The lumbar spine in backward bending

Cadaveric lumbar motion segments were loaded to simulate backward bending (extension) movements of the lumbar spine. The motion segments' resistance was measured initially, and after the spinous processes and apophyseal joints had been cut through in turn. Compression tests were then performed on the discs while they were wedged in full extension. The results showed that extension is resisted mainly by the disc and spinous processes, and that, in hyperextension, damage usually occurs first in the spinous processes (or the soft tissue squashed between them). However, if the spinous processes are particularly widely spaced, then the apophyseal joints can become damaged first. The protection offered the disc by the neural arch is greater in young people, and after the disc height has been reduced by creep loading. The disc can be damaged in hyperextension if the spine is subjected to high compressive forces at the same time. A sudden application of compressive force can cause an anterior disc prolapse, while a cyclic (fatigue) compressive force can increase the posterior bulging of the lamellas in the posterior annulus.