The pathophysiology of disc degeneration: a critical review.

The pathophysiology of intervertebral disc degeneration has been extensively studied. Various factors have been suggested as influencing its aetiology, including mechanical factors, such as compressive loading, shear stress and vibration, as well as ageing, genetic, systemic and toxic factors, which can lead to degeneration of the disc through biochemical reactions. How are these factors linked? What is their individual importance? There is no clear evidence indicating whether ageing in the presence of repetitive injury or repetitive injury in the absence of ageing plays a greater role in the degenerative process. Mechanical factors can trigger biochemical reactions which, in turn, may promote the normal biological changes of ageing, which can also be accelerated by genetic factors. Degradation of the molecular structure of the disc during ageing renders it more susceptible to superimposed mechanical injuries. This review supports the theory that degeneration of the disc has a complex multifactorial aetiology. Which factors initiate the events in the degenerative cascade is a question that remains unanswered, but most evidence points to an age-related process influenced primarily by mechanical and genetic factors.

Pedicle morphology of the immature thoracolumbar spine.

STUDY DESIGN: Human vertebral morphologic data were compiled from anatomic skeletal collections from three museums. OBJECTIVES: To quantify the morphometric characteristics of the pedicles of the immature thoracolumbar spine. SUMMARY OF BACKGROUND DATA: Little is known of pedicle morphology of the immature spine as related to pedicle screw fixation. METHODS: A total of 75 anatomic skeletal specimens were acquired from C1 to L5 in the age range of 3 to 19 years. The data were collected and analyzed using a computerized video analysis system. Each vertebral pedicle was measured in the axial and sagittal planes. The measurements included the minimum pedicle width, the pedicle angle, the distance to anterior cortex, and anteroposterior and interpedicular spinal canal diameters. RESULTS: Wide variation in pedicle morphology between specimens at each vertebral level was found in the young population. In general, compared with the average adult data, a younger spine demonstrated a near uniform reduction in the linear pedicle dimensions at each vertebral level. Pedicles from the lower lumbar vertebrae attained dimensions acceptable for standard screw sizes at an earlier age than in the thoracic vertebrae. CONCLUSIONS: The data in this study indicates that pedicle screws may be used in the adolescent spine. However, care should taken to accurately ascertain pedicle size before surgery so that improper use of screws can be avoided. Growth of the pedicles in relation to the spinal canal indicates that the increase in pedicle size is lateral to the spinal canal.

Orthopaedic surgery and Food and Drug Administration off-label uses.

The use of a drug or device for a purpose other than that for which it was approved by the Food and Drug Administration has become an important method by which medical knowledge is expanded. Ethical and moral issues are raised whenever a drug or device is used in an unapproved manner. Physicians using devices in an off-label fashion must be aware of these issues and how they affect their patients. Reviewing an ethical checklist before embarking on the use of a device or drug in an off-label fashion can alert the physician to potential ethical and moral conflicts. The ethical physician always will place his or her patient's well-being and best interests above all else. Using this pledge as the cornerstone of all clinical decisions, the virtuous physician is able to offer the most innovative and new procedures without compromising his or her ethical or moral obligations to their patients.

The biomechanical effect of postoperative hypolordosis in instrumented lumbar fusion on instrumented and adjacent spinal segments.

STUDY DESIGN: Change in lumbar lordosis was measured in patients that had undergone posterolateral lumbar fusions using transpedicular instrumentation. The biomechanical effects of postoperative lumbar malalignment were measured in cadaveric specimens. OBJECTIVES: To determine the extent of postoperative lumbar sagittal malalignment caused by an intraoperative kneeling position with 90 degrees of hip and knee flexion, and to assess its effect on the mechanical loading of the instrumented and adjacent segments. SUMMARY OF BACKGROUND DATA: The importance of maintaining the baseline lumbar lordosis after surgery has been stressed in the literature. However, there are few objective data to evaluate whether postoperative hypolordosis in the instrumented segments can increase the likelihood of junctional breakdown. METHODS: Segmental lordosis was measured on preoperative standing, intraoperative prone, and postoperative standing radiographs. In human cadaveric spines, a lordosis loss of up to 8 degrees was created across L4-S1 using calibrated transpedicular devices. Specimens were tested in extension and under axial loading in the upright posture. RESULTS: In patients who underwent L4-S1 fusions, the lordosis within the fusion decreased by 10 degrees intraoperatively and after surgery. Postoperative lordosis in the proximal (L2-L3 and L3-L4) segments increased by 2 degrees each, as compared with the preoperative measures. Hypolordosis in the instrumented segments increased the load across the posterior transpedicular devices, the posterior shear force, and the lamina strain at the adjacent level. CONCLUSIONS: Hypolordosis in the instrumented segments caused increased loading of the posterior column of the adjacent segments. These biomechanical effects may explain the degenerative changes at the junctional level that have been observed as long-term consequences of lumbar fusion.

Extradural synovial thoracic cyst.

SUMMARY OF BACKGROUND DATA. Case studies documenting the incidence of thoracic intraspinal, extradural synovial cysts are limited. The occurrence of synovial cysts is associated with varied symptoms that differ among cervical, thoracic, and lumbar regions. The clinical appearance may be similar to other spinal diseases. METHODS. This report describes symptoms exhibited by and care provided for a patient with extradural synovial thoracic cyst.

Reflex sympathetic dystrophy after operative procedures on the lumbar spine.

Between July 1987 and April 1991, reflex sympathetic dystrophy developed in eleven patients after a posterior operation on the lumbar spine. The average age of the patients was forty-four years (range, twenty-eight to sixty years). The preoperative diagnosis had been lumbar spondylolisthesis or lumbar instability, associated with degenerative disc disease or with osteoarthrosis of a facet joint. Ten patients had posterior stabilization with bilateral arthrodesis and interpedicular fixation, with use of plates or screws; the remaining patient had a posterior hemilaminotomy of the fourth and fifth lumbar vertebrae, partial discectomy, and foraminal decompression of the fifth lumbar-nerve root. After the operation, all patients had burning pain, vasomotor dysfunction, and dystrophic changes in the lower limb and foot; in four patients, the symptoms were bilateral. The symptoms began four days to twenty weeks after the operation. The patients were followed for nine months to four years. Treatment was most successful in four of six patients who had had at least one nerve-block of the sympathetic lumbar trunk in addition to physiotherapy.

The role of transpedicular fixation systems for stabilization of the lumbar spine.

Transpedicular fixation devices are extremely useful tools to achieve stabilization of the lumbosacral spine. The indications for the use of these systems are still evolving. These systems are able to obtain rigid fixation in vertebra lacking posterior elements, obtain solid sacral fixation, connect vertebra without distraction and maintain lordosis, fuse short spinal segments, and preserve motion segments. Stable, short segment constructs can be achieved even in the face of the most radical decompressions and vertebral resection. This technique is not, however, without risks. A thorough understanding of pedicle anatomy, pedicle screw insertion technique, fusion biology, and biomechanical considerations are paramount to achieve safe stabilization of the lumbosacral spine with this technique.

Factors influencing the penetration of wires into the neural canal during segmental wiring.

We evaluated the influence of the penetration of wires into the neural canal during segmental wiring in a three-part study. First we examined the anatomy of the thoracic spine, specifically the laminar and interlaminar dimensions, as well as the epidural space. In the second part, we evaluated the depth of penetration of wires into the spinal canal at the time of their passage during spinal segmental instrumentation, using direct laboratory measurements for three configurations of the wire: first with a straight wire, and then with two wires of varying curvature. The measurements were repeated after removal of a portion of the lamina. In the third and final part of the study, we assessed the relationship between the observed penetration of the wires and the depth of penetration as calculated using mathematical models for the three wire configurations. When a wire with the largest possible diameter of curvature was passed under the lamina, there was significantly less penetration using the curved-wire configuration. This was seen in calculated models, as well as in normal specimens of the thoracic spine that were obtained from cadavera. Little epidural space was found to be available for passage of the wire. In most instances, passage of the wire must result in contact with and displacement of the dural sac and its contents. To minimize the depth of penetration at any given spinal level, it is recommended that the wire be curved to the maximum degree that will allow it to pass under the lamina.(ABSTRACT TRUNCATED AT 250 WORDS)

Symptomatic spondylolisthesis in adults: four decades later.

An average follow-up of 40 years was obtained for 12 patients with spondylolisthesis treated at Hines Veterans Administration Hospital between 1944 and 1951. In each case, the slip had been Grade 1 and at the L5-S1 level. Five had been treated conservatively and seven surgically with a Hibbs fusion from L4 to S1. Of the conservatively managed patients, all functioned well during their working years, although one did have chronic, nondisabling, low-back pain. This same patient demonstrated radiographic evidence of progression to a Grade 2 spondylolisthesis. Among those undergoing surgery, the poor results were confined to those patients whose fusion attempts failed. Management for low-grade spondylolisthesis should be conservative where possible. When the low-back pain is disabling and surgery becomes necessary, failure to obtain a fusion portends a poor clinical result.

A comparative study of the clinical presentation of tarsal coalitions.

Twenty patients have received the radiographic diagnosis of tarsal coalition. Seven were talocalcaneal (35 per cent), seven were calcaneonavicular (35 per cent), and six were talonavicular (30 per cent). The average age at time of diagnosis was 19.3 years for talocalcaneal coalition, 14.7 years for calcaneonavicular coalition, and 15.2 years for talonavicular coalition. Bilateral involvement was seen in more than half of the talocalcaneal and talonavicular coalitions. Symptoms were more severe in talocalcaneal and calcaneonavicular coalitions. All patients in these two groups had pain. Talonavicular coalitions either were asymptomatic (picked up on radiographs taken for other complaints) or were associated with painful medial navicular masses. In our study, five of the six patients (81 per cent) had this mass. We report a surprisingly high number of talonavicular coalitions for such a small group. In studies based on the investigation of peroneal spastic flatfoot, this form of coalition is not as frequently encountered. This suggests that talonavicular coalitions may be much more common than the literature to date has suggested.

Analysis of the morphometric characteristics of the thoracic and lumbar pedicles.

A total of 2,905 pedicle measurements were made from T1-L5. Measurements were made from spinal computerized tomography (CT) scan examinations and individual vertebral specimen roentgenograms. Parameters considered were the pedicle isthmus width in the transverse and sagittal planes, pedicle angles in the transverse and sagittal planes, and the depth to the anterior cortex in a line parallel to the midline of the vertebral body and along the pedicle axis. There was no significant difference between data obtained from CT scans and specimen roentgenograms. Pedicles were widest at L5 and narrowest at T5 in the transverse plane. The widest pedicles in the sagittal plane were seen at T11, the narrowest at T1. Due to the oval shape of the pedicle, the sagittal plane width was generally larger than the transverse plane width. The largest pedicle angle in the transverse plane was at L5. The posterolateral to anterolateral pedicle axis orientation in the transverse plane, seen at other levels throughout the thoracolumbar spine, reversed at T12. In the sagittal plane, the pedicles angled caudally at L5 and cephaladly from L3-T1. The depth to the anterior cortex was significantly longer along the pedicle axis than along a line parallel to the midline of the vertebral body at all levels with the exception of T12 and T11.

Chemonucleolysis. A ten-year retrospective study.

An 11.8-year median follow-up evaluation of 42 "ideal" patients who had chemonucleolysis was obtained by examination, questionnaire, and roentgenograms. The excellent and good rating of this group was 81%, as compared to the total of 135 patients previously evaluated at 42 months and showing 85.2%. No complications were noted. Disc space rewidening, after initial narrowing, was observed in eight patients and 26% of all discs injected. While all who showed rewidening had excellent results, widening was not necessary to achieve an excellent rating. Marked narrowing and sclerosis of intervertebral margins were seen in many excellent and good clinical results. Chemonucleolysis represents a viable option as definitive treatment for a herniated nucleus pulposus in carefully selected patients.

A biomechanical study of intrapeduncular screw fixation in the lumbosacral spine.

This laboratory experiment was undertaken to identify factors contributing to intrapeduncular screw fixation in the vertebra. Testing was performed in axial pull-out and cyclic loading modes using multiple screw designs inserted to various depths into fresh human lumbosacral vertebra. The degree of osteoporosis played a major role in pull-out strength. Larger diameter, full-threaded screws inserted deep enough to engage the anterior vertebral cortex resulted in the most secure fixation. In the sacrum, the second sacral pedicle was the weakest location of insertion. Screws aimed laterally into the ala at 45 degrees or medially into the first sacral pedicle resisted larger axial pull-out loads than those inserted straight anteriorly into the ala. Methyl methacrylate was found to restore secure fixation in previously-loosened screws and pressurization of cement doubled the pull-out force. In cyclic load tests, deeper-inserted screws were found to withstand a greater number of cycles before loosening. Measurements of pedicle outer cortical diameters were found in many specimens to be smaller than both the 4.5-mm and 6.5-mm diameter screws.

Femoral neck fractures in the geriatric population: the influence of perioperative health upon the selection of surgical treatment.

The use of a primary prosthetic replacement such as an Austin-Moore hemi-arthroplasty in patients sustaining fractures of the femoral neck has been associated with increased post-operative medical morbidity and mortality. A retrospective review was performed using the medical records of patients greater than 59 years of age who sustained femoral neck fractures and were treated with either internal fixation or primary hemi-arthroplastic replacement at Loyola University Medical Center between 1969 and 1979. Peri-operative data were reviewed and evaluated using computer-aided statistical analysis. Comparing the two forms of surgical treatment, statistically significant factors associated with primary hemi-arthroplastic replacement included: pre-injury nursing home residence, pre-injury ambulation requiring assistance, age greater than 79 years, slight elevation in serum creatinine values, abnormal electrocardiograms in patients over 77 years of age, time from injury to surgery of four or more days, and the use of spinal anesthesia (P less than 0.05). Factors associated with internal fixation were: patient age of 79 years or less, independent ambulation, non-nursing home residence, normal lab values, normal EKGs, less than four days from injury to surgery, and the use of general anesthesia. Within the limits imposed by a retrospective review in this specific patient population, there appears to be a tendency for older, less healthy patients to have been treated with primary hemi-arthroplasty. Possibly the previously reported increased post-operative medical morbidity and mortality associated with this procedure, as compared with internal fixation, may be a result of biased patient selection, and not a fault of the procedure.

Metastatic tumors of the foot: case report and literature review.

Metastatic lesions to the bones of the foot occurred in three elderly patients. Biopsy established the diagnosis in a 90-year-old woman. In a 72-year-old man and a 79-year-old man, the diagnosis was possible from roentgenographic features. In the latter, biopsy of an additional osseous metastatic site established the diagnosis. A thorough review of the literature has yielded 72 previously reported cases of metastasis to the foot. Only 38 of these cases were histologically confirmed. Primary tumors of the colon, kidney, and lung are the most common sources of metastasis to the bones of the foot. Metastatic disease should be considered in elderly patients presenting with foot pain and osteolytic lesions, especially when there is a history of a previously diagnosed malignancy. The generally poor prognosis indicates that treatment should be clearly designed to relieve pain.

Assessment of the accuracy of three techniques to predict leg length discrepancy.

Three techniques to predict leg length discrepancy were applied to a series of 50 patients with leg length inequality. The methods of Green and Anderson, the Moseley Chart, and a program written by the authors, designed to be run on a relatively inexpensive programmable calculator, were used.The data processed on the calculator produced slightly more accurate results than the Moseley Chart, though not statistically significant. The Green and Anderson technique resulted in the largest errors.