A phantom based study on the effect of subject positioning on morphometric X-ray absorptiometry using the Lunar Expert-XL

Morphometric X-ray absorptiometry (MXA) relies on accurate measurement of vertical dimensions of vertebrae from a lateral perspective. Deviations resulting from scoliotic curvature or poor patient positioning produce distortions of visible vertebral dimensions and may lead to analysis error. This study utilized a phantom developed at this centre to assess the effect of vertebral malalignment on the accuracy of the MXA technique on the Lunar Expert-XL. Measured vertebral heights were found to be consistently underestimated by an average of 3.7%. Precision ranged from 0.79% for anterior height measurement to 1.03% for middle height measurement. Vertebral malalignment was investigated as the effect of rotation around the anteroposterior, lateral and superoinferior axes. Rotation around the lateral axis produced little discernible effect. However, superoinferior axial rotation showed a change of more than two standard deviations in the mid/posterior ratios of biconcave vertebrae at comparatively small angles of rotation. Anteroposterior axial rotation produced an increase in observed height at small angles of rotation, and a rapid decrease in vertebral height as rotation increased. The results suggest that whilst kyphosis or lordosis of up to at least 5.8 degrees has a minimal effect on MXA, scoliosis of 4.6 degrees or above produces a distinctive effect on the defining crush height ratios.

Cost-benefit value of microscopic examination of intervertebral discs

OBJECT

Given the virtual absence of histologically detected, clinically unsuspected disease in intervertebral disc specimens, some authors have advocated that histological examination be discontinued. However, the examination of intervertebral disc specimens remains common practice in most pathology laboratories. No cost-benefit analysis of this practice has been made; therefore, the authors' goal in this study was perform such an analysis.

METHODS

Using the University of Iowa surgical pathology database, 1109 patients who had undergone a laminectomy were identified retrospectively. These cases were classified into four categories based on the patients' preoperative clinical diagnosis and final histopathological diagnosis: insignificant clinical diagnosis/insignificant pathological diagnosis (ICIP), significant clinical diagnosis/insignificant pathological diagnosis (SCIP), significant clinical diagnosis/significant pathological diagnosis (SCSP), and insignificant clinical diagnosis/significant pathological diagnosis (ICSP). A significant clinical diagnosis was defined as one other than a benign, noninfectious indication for laminectomy. A significant pathological diagnosis was a diagnosis other than degenerative changes. The cost-benefit value of performing a histological examination in cases with significant or insignificant clinical diagnoses was examined. The cases were classified as: 1068 ICIP, 17 SCIP, 21 SCSP, and three ICSP. On chart review, in all three cases of ICSP an epidural abscess was identified perioperatively and the subsequent histological diagnosis did not affect patient care. The costs per case of identifying a significant pathological diagnosis with a significant and an insignificant clinical diagnosis were $44.79 and $8811, respectively.

CONCLUSIONS

Histological examination of intervertebral disc specimens is cost beneficial only if there is a significant preoperative clinical diagnosis.

Changes in the disc space after fractures of the thoracolumbar spine

We have studied the intervertebral discs adjacent to fractured vertebral bodies using MRI in 63 patients at a minimum of 18 months after injury. There were 75 thoracolumbar fractures of which 26 were treated conservatively and 37 by posterior reduction and fusion with an AO internal fixator. We identified six different types of disc using criteria based on the morphology and the intensity of the MRI signal. The inter- and intraobserver variability of this system was good. Most of the discs showed predominantly morphological changes with no variation in signal intensity. Some disc types were associated with progressive kyphosis in patients treated conservatively. In those managed by operation, recurrent kyphosis appeared to result from creeping of the disc in the central depression of the bony endplate rather than from disc degeneration. Changes in the disc space after posterior fixation should not be seen as a form of chronic instability but as a redistribution of the disc tissue in the changed morphology of the space after fractures of the endplate.

Stress fractures of the vertebral lamina and pelvis in Thoroughbred racehorses

Thirty-six Thoroughbred racehorses that died at California racetracks between October 1993 and July 1994 were evaluated for stress fractures in the caudal portion of the thoracic and lumbosacral regions of the spine and the pelvis. The lumbosacral spine and pelvis were collected, debrided of soft tissues and examined visually for the presence of an incomplete fracture line and focal periosteal proliferation, characteristic of a stress fracture. Sixty-one per cent of specimens had evidence of stress fracture in the caudal portion of the thoracic and lumbosacral regions of the spine and the pelvis. Vertebral lamina stress fractures were found in 50% of specimens and were positively associated with the severity of dorsal spinous process impingement and overall severity of articular process degenerative changes. Pelvic stress fractures affected 28 % of specimens and occurred more frequently in older horses. Pelvic stress fractures were positively associated with the severity of lumbar transverse process impingement and several ilial articular surface degenerative changes. A high prevalence of vertebral and pelvic stress fractures was noted in this sample of Thoroughbred racehorses that died because of unrelated injuries. Vertebral and pelvic stress fractures need to be considered in the clinical evaluation of horses with back problems or hindlimb lameness. Undiagnosed stress fractures of the vertebrae or pelvis could be a significant cause of poor performance and lameness in Thoroughbred racehorses.

Fractal properties of cancellous bone of the iliac crest in vertebral crush fracture

Fractal analysis is a method for describing complex shapes, including the cancellous structure of bone. It describes the surface texture and form of individual trabecular profiles and the overall cancellous structure. Sixty-four postmenopausal women with symptoms of back pain were referred for investigation for osteoporosis. The patients were divided into two groups for comparison: vertebral crush fracture (n = 31, mean age 68.58 +/- 6.47 years), and no vertebral crush fracture (n = 33, mean age 63.36 +/- 7.21 years). Cores of cancellous bone, 3 mm in diameter, were taken from the iliac crest and sectioned. A box-counting method implemented on an image analyzer was used to measure the fractal dimension. Three fractal dimensions describing trabecular surface texture (fractal 1), trabecular shape (fractal 2), and trabecular arrangement (fractal 3) were measured, indicating that cancellous bone has sectional self-similarity. Conventional histomorphometry was also performed on the samples. The results show that fractal 2 is significantly lower in the vertebral crush fracture group than in the nonfracture group (1.15 +/- 0.10 < 1.23 +/- 0.090, p < 0.0013). The histomorphometric analysis shows that bone surface total volume (p < 0.0002), trabecular number (p < 0.0001), and osteoid surface bone surface (p < 0.028) are significantly lower in the fracture group than the nonfracture group. Eroded surface/bone surface (p < 0.056) follows this trend, whereas trabecular separation (p < 0.001) is significantly higher in the fracture group than in the nonfracture group. Fractal 1 and fractal 3 were not significantly different between study groups. The fractal dimension detects changes in the cancellous architecture and gives information about iliac bone transformation in postmenopausal women with vertebral fracture.

[Quantitative morphology of vertebral body cortical bone. Building block for noninvasive calculation of fracture threshold in osteoporosis]

The vertebral bodies consist of two main structures, trabecular and cortical bone. The histological changes within the spine, especially in cortical bone, leading to osteoporotic fractures remain, however, poorly understood. Therefore, the complete front column of the spine was removed in 26 autopsy cases without skeletal diseases and in 11 cases with proven osteoporosis. A sagittal segment prepared through the center of all vertebral bodies was undecalcified embedded in plastic, ground to a 1-mm-thick block and stained using a modification of the von Kossa method. The analysis included measurement of the mean cortical thickness of both ventral and dorsal shell (from C3 to L5). The qualitative investigation of the structure of the cortical ring completed the analysis. The skeletally intact specimens had high cortical thickness values in the cervical spine (285 +/- 22 microns), a decrease in the thoracic spine (244 +/- 14 microns) and an increase in the lumbar spine (290 +/- 15 microns). The mean thickness of the ventral shell is in general higher than the thickness of the dorsal shell. The cortical thickness of the spine showed no gender-specific differences (P = n.s.). There was a slight decrease in the cortical thickness with age; however, this decrease and the correlation of cortical thickness to age was only significant below vertebral body T8 (r = 0.225 to 0.574; Pr < 0.05 to Pr < 0.005). Most interestingly, osteoporosis is characterized by a significant decrease in cortical thickness throughout the whole spine. This decrease in cortical thickness was more marked in the dorsal shell (P < 0.05) than in the ventral shell (ventral from C3 to T6 (P < 0.05) below T6 (P = n.s.). We therefore conclude that in osteoporosis, biomechanical competence is affected by both trabecular bone loss and decrease of cortical thickness. This suggests that, in addition to trabecular bone measurements, the cortical thickness is of special interest for diagnostic radiological examinations (CT) to yield clues about the risk of vertebral fractures.

Hangman's fracture: arguments in favor of surgical therapy for type II and III according to Edwards and Levine

BACKGROUND

The optimal therapy for traumatic fractures of the neural arch of the axis, the so-called hangman's fractures, is still controversial. Indications for surgery depend on the type of hangman's fracture and/or additional injuries of the intervertebral disc or ligaments.

METHODS

Sixteen patients sustaining fractures of the neural arch of the axis were treated by the screw fixation technique evolved by Judet. The passive mobility of the cervical spine was analyzed postoperatively by the radiographic evaluation method of Dvorak and coworkers and Penning. The angulation and anterior translation of C2 on C3 was measured before and after surgery.

RESULTS

Follow-up investigations 3, 12, and in some cases 45 months later confirmed sufficient functional results especially regarding the mobility of the upper cervical spine. Comparison of pre- and postoperative angulation and anterior translation of C2 on C3 revealed a significant improvement especially in cases with type IIa fractures.

CONCLUSION

The stabilization technique of Judet facilitates an exact reconstruction of anatomical conditions thereby preserving the atlantoaxial rotational mobility. A negligible hypomobility of the C2-C3 segment was observed on average 18 months after surgery.

[Contribution of magnetic resonance to the differential diagnosis of a collapsed vertebra in a patient with multiple myeloma]

The only safe method to determine whether or not patients diagnosed of smoldering myeloma will progress to symptomatic multiple myeloma (MM) is periodic follow-up. In the last years, several studies have emphasized the efficacy of magnetic resonance imaging (MRI) to detect bone marrow involvement in these patients. However, the detection of a focal spinal lesion in elderly patients raises a diagnostic problem, sometimes difficult to solve, between a benign or malignant origin. We present the case of an elderly women with marked osteoporosis and smoldering myeloma who suddenly complained of pain in dorsal spine. MRI showed focal lesions in two dorsal vertebra consistent with myeloma involvement. However, there were no other signs of progression, the lesions were considered secondary to osteoporosis and calcitonin was administered. This resulted in the disappearance of the pain and the MRI abnormalities, which confirmed its benign etiology. The role and limitations of MRI to detect bone marrow involvement by MM in the evaluation of these patients is reviewed.

[Ventral spinal cord compression on the C1-C2 levels with injury of the craniocervical junction]

While CII vertebral dent fracture, neurological complications occur due to its 4 mm shift. The direct approach application (transoral--while the dent fracture or anterolateral--while hagman fracture occurrence) makes possible to achieve an adequate decompression of spinal cord and the vertebral channel reconstruction. Rigid occipitocervical spondilodesis achievement is guaranteed by the metallic loop application and the vertebral arches fixation. While conservative treatment of such a fracture the bones fragments reposition due to the sceletal pulling conduction constitutes the preliminary stage of external immobilization (SOMI or Halo) application.

Functional morphology of the spinal canal after endplate, wedge, and burst fractures

Changes in the canal diameter during physiological motions are important considerations in the treatment of patients who have a burst fracture with the presence of bony fragments, but without neurologic deficit. In this in vitro study, the changes in the soft-canal diameter of the thoracolumbar region, when intact and after different fractures, was investigated under several different loading conditions. The soft-canal diameter was clearly identified on the lateral radiographs by attaching a series of steel balls to the posterior longitudinal ligament and ligamentum flavum in the midsagittal plane. Endplate, wedge, and burst fractures were produced incrementally in 19 three-vertebrae human cadaveric spine specimens by high-speed impacts. After each injury, a series of functional lateral radiographs were taken. The minimal canal diameter (MCD) was obtained by digitizing the images of the steel balls on radiographs using a custom-designed computer program. In the intact specimens, the MCD at the disc level changed significantly in flexion, extension, and compression, when compared with the MCD in the unloaded neutral position. However, the changes were small. The MCD after endplate and wedge fractures changed in a similar way. However, after the burst fracture, the MCD at the bone fragment level increased remarkably by a distraction force. It also significantly improved by an anterior shear force in comparison to the corresponding MCD in the neutral position. However, this change was smaller than the change due to the distraction force.

Completely dislocated hangman's fracture with a locked C2-3 facet. Case report

The authors report a rare case of a hangman's fracture involving complete dislocation of C-2 onto C-3, accompanied by a C2-3 locked facet and asymptomatic bilateral vertebral artery injuries. The patient, a 25-year-old man who sustained a neck injury in an industrial accident, presented with a mild central spinal cord syndrome. His initial lateral cervical radiograph showed complete anterior dislocation of the C-2 body onto C-3, bilateral neural arch fractures, and a unilateral locked facet. The mechanism was likely flexion and compression. The grossly unstable spine and the locked facet were treated by posterior decompression, reduction, and C1-3 fixation. The patient recovered in several days and is without neurological deficit.

[Traumatic ascending ischemic injury of the spinal cord]

We report five cases that the paraplegic level showed ascending from the segment of spinal injury upward to the higher level. In T10-11 fracture-dislocation, the paraplegic level ascended gradually to C2-3 in case 1 within 10 days and death due to breathing paralysis. In case 2, the paraplegic level ascended to cervical cord with loss of strength in both arms within 14 days. The remaining 3 cases were Ti2(in 2 cases) and L3(1 case) fracture. Their paraplegic level ascended to T8(2 cases) and T9(1 case). There were lower motor neuron paralysis in all cases. Observation on spinal cord specimen of case 1 showed thrombosis of dorsal vessels at T9-10 segment and multiple thrombosis were found in anterior spinal vessels, central spinal vessels and intramedullar small vessels upward to C3 and downward to S1 segments. The whole cord underwent ischemic necrosis.

Idiopathic avascular necrosis of a vertebral body. Case report and literature review

STUDY DESIGN

Case report and literature review.

OBJECTIVES

To review the English literature pertaining to idiopathic avascular necrosis of a vertebral body. As an illustrative example, the case of a 60-year-old woman with idiopathic avascular necrosis of L4 is presented.

SUMMARY OF BACKGROUND DATA

Avascular necrosis of a vertebral body is an uncommon entity. Avascular necrosis has been described in the context of other underlying lesions, such as with malignancy, infection, radiation therapy, and systemic steroid treatment. The intravertebral vacuum cleft phenomenon seen on plain films has been strongly associated with vertebral body avascular necrosis.

METHODS

Literature and chart review was carried out. Vertebral body avascular necrosis was initially identified with imaging studies and confirmed with biopsy. A comprehensive preoperative evaluation did not identify a specific cause of avascular necrosis. The patient underwent vertebral body resection with fibula allograft struts.

CONCLUSIONS

Although vertebral body collapse in an osteoporotic individual is relatively common, a case is reported of vertebral body collapse and subsequent necrosis without evidence of underlying disease at 48-month follow-up. The current findings support the diagnosis of idiopathic avascular necrosis of L4.

The intravertebral vacuum phenomenon ("vertebral osteonecrosis"). Migration of intradiscal gas in a fractured vertebral body?

STUDY DESIGN

Retrospective cohort.

OBJECTIVES

To compare the prevalence of the association between contiguous intervertebral disc and vertebral collapses with or without an intravertebral vacuum phenomenon.

SUMMARY OF BACKGROUND DATA

The mechanism of occasional gas accumulation within some vertebral collapses is poorly known. The current hypothesis is that this phenomenon is indicative of bone ischemia. In fact, avascular necrosis as the main pathologic event remains speculative, and should not explain per se the presence of gas within a vertebral body.

METHODS

Comparison of the prevalence of intervertebral disc vacuum phenomenon adjacent to the affected vertebral body in 23 cases of intravertebral vacuum phenomenon in 19 patients (intravertebral vacuum phenomenon group) and in 708 osteoporotic collapses without intravertebral vacuum phenomenon in 199 patients (control group).

RESULTS

There were no differences in sex and age between the two groups, and all the patients in the intravertebral vacuum phenomenon group had signs of underlying osteoporosis. A vacuum phenomenon in at least one intervertebral disc adjacent to the collapses on radiographs, conventional tomography, computed tomography, or magnetic resonance imaging was found in 19 cases (83%) in the intravertebral vacuum phenomenon group, compared with 13% in the control group (P < 0.0001). Considering plain radiographs only, this association was found in 50% of the intravertebral vacuum phenomenon group and in 9.7% of the control group (P < 0.0001). The intervertebral and intravertebral gaseous collections were connected through a fractured endplate in six cases.

CONCLUSIONS

The high prevalence of the association of contiguous intervertebral and intravertebral vacuum phenomenon could have implications in the pathogenesis of the intravertebral vacuum phenomenon. We hypothesize that the intravertebral vacuum phenomenon could simply be the result of migration of an intradiscal-gaseous collection through the fractured endplate of some osteoporotic collapses.

Osteoporosis clinical trials endpoints: candidate variables and clinimetric properties

We reviewed evidence on endpoints used in osteoporosis clinical trials to assist in the development of a set of endpoints to be included in all trials. A MEDLINE search was conducted using the Cochrane Collaboration strategy for each endpoint. Additional published literature was obtained from content experts. A proposed list of endpoints was developed after consultation with experts in the field. Each endpoint was evaluated with respect to validity, reproducibility, redundancy, and feasibility. We classified the endpoints into 2 major categories: clinical health status outcomes and intermediate endpoints, and for each endpoint we present current evidence from the literature as pertains to defined methodologic criteria. Multiple endpoints have been used in osteoporosis clinical trials, and an agreement on a core set of measures needs to be evidence based with an emphasis on validity, reproducibility, and feasibility and to satisfy clinical credibility.

Traumatic vertical atlantoaxial instability in a case of atlanto-occipital coalition

STUDY DESIGN

This is a report of a woman with an atlanto-occipital coalition who experienced a traumatic vertical atlantoaxial facet dislocation and severe associated neurologic injury.

OBJECTIVE

To describe the radiographic and pathoanatomic characteristics of the injury process.

SUMMARY OF BACKGROUND DATA

Severe injuries of the occipito-atlantoaxial complex are uncommon and only rarely are associated with patient survival. This is the first report of this particular injury.

METHODS

Plain radiography and tomography demonstrated the facet dislocation and instability of the injury. Surgical exploration for repair of the torn dura mater and bony arthrodesis demonstrated the gross pathoanatomy.

RESULTS

The patient's vertical atlantoaxial instability was stabilized, her dura mater reconstructed, and her necrologic status has improved to allow mobilization with a cane.

CONCLUSION

Vertical atlantoaxial instability has not been described previously. From the somewhat subtle radiographic findings, one might underestimate the severity of the neurologic damage. Aggressive work-up and management of this injury is suggested to avoid potential further necrologic sequelae.

Cervical spine fractures in the elderly

BACKGROUND

Cervical spine fractures in the elderly are relatively common. The management of such injuries may be complicated by underlying medical debility and osteopenia as well as reduced tolerance to halo immobilization.

METHODS

Over a 1-year period, 43 cervical spine fractures were treated at our institution. Ten (23%) were in persons 70 years of age or older. This retrospective analysis describe the clinical features, treatment, and outcome of these 10 elderly patients. All fractures in this patient population involved the atlantoaxial complex, including five combination C1-C2 fractures. Six patients were treated with early halo immobilization and three were initially managed with a rigid cervical collar. Three patients required posterior cervical fusion.

RESULTS

Of the six patients undergoing halo immobilization, five progressed to osseous union. Three patients were immobilized in a Philadelphia collar resulting in one osseous union, one nonunion, and one death. Three patients underwent posterior cervical fusion with subsequent osseous union in all three.

CONCLUSIONS

Although external immobilization with a halo device is our treatment of choice for most C1 and C2 fractures in elderly patients, a Philadelphia collar is useful in select cases when halo immobilization or early surgical fusion is contraindicated. Posterior cervical fusion can be safely and effectively performed in elderly patients and should be strongly considered for initial therapy in the elderly with fracture types unlikely to progress to osseous union with external immobilization alone.

Methods to score vertebral deformities in patients with rheumatoid arthritis

The objective was to compare four different scoring methods for vertebral deformities: the semiquantitative Kleerekoper score and three quantitative scores (according to Minne, Melton and Raymakers) in patients with rheumatoid arthritis (RA). Lateral radiographs of the thoracic and lumbar vertebral column were scored in 52 RA patients treated with corticosteroids (Cs) and 52 RA patients not Cs treated (matched for age and gender). Clinically manifest vertebral fractures were defined as a vertebral deformity leading to the prescription of therapy: bedrest and/or analgesies. The number of Cs-treated RA patients with vertebral deformities was only increased according to the Kleerekoper score (relative risk 2.31; 95% confidence interval 1.36-3.90). The total number of vertebral deformities was increased in Cs-treated RA patients according to the method of Kleerekoper. Minne and Raymakers, but not according to Melton. The Spinal Deformity Index was increased in the Cs-treated RA patients according to Minne (P < 0.05), but not according to Raymakers. In both patient groups, the number of patients with clinically manifest vertebral fractures was much lower than that of vertebral deformities, e.g. in the Cs-treated patients 13% vs 35.79% (depending on the scoring method used). All eight patients with clinically manifest vertebral fractures had severe height loss (25% or more) in at least one vertebra. Vertebral deformities seem to occur more often in Cs-treated patients than in those not Cs-treated. However, differences exist in the number of patients with vertebral deformities and in the total number of vertebral deformities between different scoring methods. This emphasizes the need for a gold standard or consensus for defining vertebral deformities, in which, in our opinion, a Spinal Deformity Index has to be included. Clinically manifest vertebral fractures are predominantly characterized by severe vertebral deformities on X-rays.

Neurological deficit in a consecutive series of vertebral fracture patients with bony fragments within spinal canal

The wide spread availability of computerized tomography has added a new dimension to the anatomical evaluation of vertebral fractures. This diagnostic modality has shown that in these fractures, the protrusion of bone spicules into the spinal canal is often encountered. The clinical significance of this finding and its relation to the need of establishing indications for surgery in these patients is controversial. The neurological outcome of patients with postraumatic bony encroachment of the spinal canal is not well documented in the literature, and therefore the adequate therapeutic approach is neither clear nor is it unanimous. Whether treatment should be aggressively surgical with decompression and/or segmental fusion, or conservative, the goal has to be prevention of secondary injury to the spinal cord. This presentation is a mean 4 year follow up study of 38 consecutive patients with spinal fractures and spinal canal narrowing, who were treated conservatively. The results demonstrate that the initial neurological findings have a very significant prognostic value for the neurological outcome, regardless of the spinal segment involved, the type of injury and spinal canal narrowing as demonstrated by computerized tomograms. We conclude that in trauma patients with vertebral fractures and spicules in the spinal canal without evidence of an initial neurological deficit, a favorable neurological prognosis can be predicted, following conservative management.

Age-related changes in vertebral height ratios and vertebral fracture

Because no gold standard for the definition of vertebral fracture exists, there has been controversy about whether mild vertebral deformities are truly fractures or simply normal variation in vertebral size and shape. The aim of this study was to assess the associations of mild variations of vertebral height ratios to definite vertebral fractures. In 479 Japanese women (aged 53.9 +/- 9.1 years) who visited our institute for a medical checkup, we performed lateral lumbar radiographs and morphometric parameters were derived by measuring the anterior (Ha), middle (Hm) and posterior (Hp) height of each vertebral body from T12 to L4. Vertebral height ratios, Ha/Hp, Hm/Hp or Hp/Hp' of adjacent vertebrae that were more than 3 SD different from vertebra-specific means of normative data were considered to indicate fractures. Forty-five women were diagnosed with at least one fracture. After excluding the subjects with vertebral fracture, we examined the associations of the variations in vertebral height ratios with age, anthropometric parameters and lumbar bone mineral density (BMD) measured by dual-energy X-ray absorptiometry. Vertebral height ratios, especially Hm/Hp in postmenopausal women, tended to decrease with age and were positively associated with BMD. No significant correlation was observed between anthropometric parameters and vertebral height ratios. Aged-related decrease in vertebral height ratios (Ha/Hp and Hm/Hp, each averaged from T12 to L4) was significant even after the correction for BMD. Mean values of height ratios of non-fractured vertebrae adjusted for age and BMD were significantly lower in postmenopausal women with vertebral fracture than in those without vertebral fracture. Logistic regression analysis showed that BMD and height ratios of non-fractured vertebrae were independent predictors of vertebral fracture risk. The results suggest that older women, and women with at least one obvious (3 SD) fracture, tend to have mild deformities which do not qualify using the 3 SD definition. These mild deformities may represent real consequences of osteoporosis, because they are more pronounced among women with obvious fracture.

In vivo trabecular microcracks in human vertebral bone

Human vertebral cancellous bone from white males (N = 19), black males (N = 16), white females (N = 12), and black females (N = 17) was examined histologically for the presence, numerical density, and morphology of in vivo microscopic cracking (microdamage). Two patterns of microcracks, linear and cross-hatched, were observed. Linear microcracks were observed in both the central portion and near surfaces of trabeculae. Those inside trabeculae were usually single microcracks approximately 50 microns in length and were found in both cement lines and in interstitial bone matrix. Linear microcracks near the trabecular surface were usually multiple parallel cracks approximately 80 microns in length. Microcracks with a cross-hatched appearance were less prevalent. They were observed primarily in vertically oriented trabeculae and were often surrounded by an area of diffuse staining. Two-way ANOVA revealed no differences in microcrack density (Cr.Dn; #/mm2) between males and females [mean (SD) 5.13 (5.02) vs. 5.41 (6.26), respectively], but whites had significantly higher microcrack density than blacks [7.00 (5.71) vs. 3.63 (4.98), respectively, p < 0.05]. White males had a significantly higher microcrack density than black males [7.60 (5.56) vs. 2.21 (1.78), respectively, p < 0.05]. Although not statistically significant, white females also had higher microcrack density than black females. In contrast to what has been reported in the femur, regression analysis found no statistically significant relationship between microcrack density in the spine and age for any of the four race-gender groups. However, significant power relationships were found between microcrack density and bone area fraction for all groups except for black females. The difference between axial and appendicular bone remodeling rates, and their implications for microdamage accumulation, are discussed.

Circumferential growth plate fracture of the thoracolumbar spine from child abuse

We report a unique fracture dislocation of the immature spine associated with child abuse and paraplegia. Because it occurs through growth centers, this fracture may be initially difficult to identify without special studies. The fracture patterns were isolated injuries in both children and were best shown with computer tomography. Mechanisms of injury are proposed and should suggest child abuse as a cause. Experience with these initial cases has suggested a treatment approach based on the mechanism of injury. There is no indirect means of reduction for this fracture and anterior open reduction is the treatment of choice.

Computed tomographic scans of minimally displaced type II odontoid fractures

OBJECTIVE

To determine the computed tomography (CT) appearance of minimally displaced type II odontoid fractures and the optimal protocols to evaluate these fractures by CT.

MATERIALS AND METHODS

The CT scans of five patients with minimally displaced type II odontoid fractures and 71 patients without odontoid pathology were reviewed for signs of fracture. A phantom consisting of a cadaver specimen with a type II odontoid fracture was evaluated with several protocols on four CT scanners. The protocols differed in slice thickness and reconstruction algorithm. Helical scanning was also performed, and parasagittal and coronal reformations were created from each image set.

MAIN RESULTS

Multiple cortical disruptions longer than 1 mm were demonstrated on the scans of all five patients with type II odontoid fractures. Only three of the 71 patients without odontoid fractures had multiple cortical disruptions, and none were longer than 1 mm. In the phantom study, thinner sections demonstrated cortical disruptions better than thicker sections. Similarly, images reconstructed with a bone reconstruction algorithm demonstrated the cortical disruptions better than images reconstructed with a soft-tissue reconstruction algorithm. Helical scans (1 mm thick) adequately demonstrated the reduced Type II odontoid fracture. Parasagittal and coronal reformations failed to demonstrate a fracture line through the base of the odontoid process on all image sets.

CONCLUSIONS

Cortical disruptions greater than 1 mm and multiple cortical disruptions may be the only findings of odontoid fractures and should suggest the diagnosis. Evaluation of potential type II odontoid fractures is improved as CT section thickness is reduced (down to 1 mm) and is also improved by use of a bone reconstruction algorithm. The apparent absence of a fracture line through the base of the odontoid process on parasagittal or coronal reformations does not rule out the diagnosis.