Spontaneously occurring fractures of the spine in skeletally immature animals

STUDY DESIGN

Twelve spontaneously occurring fractures of the spin in nine skeletally immature animals were investigated.

OBJECTIVES

These fractures were analyzed radiographically, morphologically, and histologically.

SUMMARY OF BACKGROUND DATA

The most commonly injured regions were the cervical and lumbar regions. Multiple-level fractures were noted in three specimens.

METHODS

Morphologic and histologic examination invariably detected fractures in cases of spinal cord injury without radiographic abnormality.

RESULTS

The end-plate physes and synchondroses were found to be the "weak links" for propagation of fractures. Radiographically benign-appearing ring apophyseal fractures were found histologically to propagate from the end-plate physis through the vertebral body via the contiguous neurocentral synchondroses.

CONCLUSIONS

The observed morphologic and histologic fracture patterns should provide a better understanding of the probable comparable pathoanatomy of spine and spinal cord injuries in children.

The "tear drop" (or avulsed) fracture of the anterior inferior angle of the axis

Fourteen cases of an anterior inferior angle fracture of the axis treated in the Orthopaedic Department of the University of Athens from January 1970 to December 1992 were analysed. The mean follow-up time was 8.5 years. The so-called "tear drop" fracture of the axis composes a special entity characterised by an avulsed fragment, of varying size, from the anterior inferior angle of the body of the axis as a result of hyperextension. This type of injury is not a frequent one, representing 3% of the cervical spine trauma in our Department. There were eight men and six women with a mean age of 47 years. Road traffic accident is by far the most common mode of aetiology. The stability of this lesion is questioned by certain authors, resulting in disagreement concerning the choice of treatment to be followed. All the patients in our series were treated conservatively, consisting at the beginning with Glisson traction and then the use of a simple cervical collar. The rotation of the detached fragment, its anterior displacement, the posterior displacement of the vertebral body as well as the presence of instability at the C1-3 levels were analysed. The high incidence of co-existing lesions at the same or at a more distal level is discussed. This study revealed that there was no significant displacement of the vertebral body, and thus disturbance of the posterior ligaments, rendering the fracture stable.(ABSTRACT TRUNCATED AT 250 WORDS)

[Morphology of the surgically treated dens fracture]

The peculiarities within the microarchitecture of the base of the dens have to be assumed as one of the underlying causes for type II and III fractures of the dens according to Anderson and D'Alonzo. As can be demonstrated in a section of the dens of a patient after primary osteosynthesis using two small fragment AO cancellous screws this leads to multiple local trabecular fractures and destruction of the cancellous microarchitecture. Further more compression by the screws results in a higher density of the bone mass in the region of fracture. Apart from the fact that two AO screws guarantee rotational stability, this type of osteosynthesis seems to favour intracorporal bony fusion by increased trabecular bone volume and induction of microcallus within the base of the dens. In a patient with a small intracortical transverse diameter of the dens the available space is completely filled by the screws threads. Partial penetration of the threads through the cortical bone seems to be of no clinical and biomechanical relevance and can be avoided using screws of smaller diameter.

Geometric changes in the cervical spinal canal during impact

SUMMARY OF BACKGROUND DATA

Although the extent of injury after cervical spine fracture can be visualized by imaging, the deformations that occur in the spinal canal during injury are unknown.

STUDY DESIGN

This study compared spinal canal occlusion and axial length changes occurring during a simulated compressive burst fracture with the residual deformations after the injury.

METHODS

Canal occlusion was measured from changes in pressure in a flexible tube with fluid flowing through it, placed in the canal space after removal of the cord in cadaver specimens. To measure canal axial length, cables were fixed in C1 and led through the foramen transversarium from C2-T1, then out through the base, where they were connected to the core rods of linearly variable differential transformers (LVDT). Axial compressive burst fractures were created in each of ten cadaveric cervical spine specimens using a drop-weight, while force, distraction, and occlusion were monitored throughout the injury event. Pre- and post-injury radiographs and computed tomography scans compared transient and post-injury spinal canal geometry changes.

RESULTS

In all cases, severe compressive injuries were produced. Three had an extension component in addition to compression of the vertebra and retropulsion of bone into the canal. The mean post-injury axial height loss measured from radiographs was only 35% of that measured transiently (3.1 mm post-injury, compared with 8.9 mm measured transiently), indicating significant recovery of axial height after impact. Post-injury and transient height loss were not significantly correlated (r2 = 0.230, P = 0.16) demonstrating that it is not a good measure of the extent of injury. Similarly, mean post injury canal area was 139% of the minimum area measured during impact, indicating recovery of canal space, and post-injury and transient values were not significantly correlated (r2 = 0.272, P = 0.12). Mean post-injury midsagittal diameter was 269% of the minimum transient diameter and showed a weak but significant correlation (r2 = 0.481, P = 0.03).

CONCLUSIONS

Two potential spinal cord injury-causing mechanisms in axial bursting injuries of the cervical spine are occlusion and shortening of the canal. Post-injury radiographic measurements significantly underestimate the actual transient injury that occurs during impact.

Normalization of spine densitometry

We investigated several transformations of bone mineral content (BMC) and area density (BMD), in particular volumetric density (BMAD), to ascertain the influence on (1) body size dependence, (2) diagnostic sensitivity, and (3) precision. These transformations were examined in a group of 657 normal postmenopausal women and 327 women with osteoporotic fracture. First, expression of results as BMAD removed some of the slight dependence on body size; 21% of the variation in BMC and 15% of the variation i BMD were associated with body weight, but only 8% with BMAD. Second, the Z scores compared with those for age-matched controls for BMD and BMC were -1.85 and -1.71, respectively; the Z score for BMAD was -1.64. Third, the precision error for BMC was reduced by expressing results as BMD (1.1 versus 0.5%); BMAD degraded precision slightly (0.7%). BMD appeared to be the optimal expression for bone densitometry because it provided the best diagnostic sensitivity and lowest precision error; there was a minimal influence of body size on BMD results. This study also showed that osteoporotic women, even in the first postmenopausal decade, had low spine BMD, small vertebral area, and low body weight. Such women may be particularly at risk of crush fracture.

The lateral atlanto-axial joints and their synovial folds: an in vitro study of soft tissue injuries and fractures

Thirty victims of blunt cervical trauma, who did not survive (acute death group), were studied at autopsy as were 11 patients who survived trauma for more than 1 month and ten controls without any known cervical trauma. All specimens were sagitally sectioned in 2-mm slices and carefully examined for injuries to the lateral parts of the atlanto-axial joints. In the acute death group, five cases showed a rupture of the joint capsule, three of these with a massive hemarthrosis. In 17 cases there was bruising around the second cervical spinal nerve. Bruising of the intra-articular synovial fold was present in 15 cases, the posterior synovial fold being most commonly affected. There were five intra-articular fractures of the lateral masses, in three cases combined with a dens fracture. In two cases a bone fragment from the fracture compressed and obliterated the lumen of the vertebral artery. The findings are discussed in relation to pain after cervical trauma.

Relationship of osteophytes to bone mineral density and spinal fracture in men

PURPOSE

To investigate the relationship of spinal osteophytes to vertebral bone mineral density (BMD) and to spinal fracture.

MATERIALS AND METHODS

This relationship was investigated in 203 men. Integral BMD was measured with dual x-ray absorptiometry, and both cortical and trabecular BMD were measured with quantitative computed tomography (QCT).

RESULTS

Trabecular BMD was found to decrease with age in subjects with and without large osteophytes, while cortical and integral BMD decreased with age only in subjects without large osteophytes. Trabecular BMD in men without fracture was significantly higher than in those with fracture (P < .05 for BMD measured with single-energy QCT), while there was no significant difference between these groups in cortical or integral BMD.

CONCLUSION

Measurement of trabecular BMD with QCT provides information useful in detection of age-related bone loss and of fracture in men with and without osteophytes.

Jefferson fractures: the role of magnification artifact in assessing transverse ligament integrity

Thirty-five consecutive odontoid views were taken using a standardized technique. A 10-mm radiographic marker was positioned lateral to the tip of the C-1 transverse process. Data from three independent readers showed an 18% magnification error inherent to anteroposterior open-mouth odontoid radiographs. Integrity of the transverse ligament after Jefferson fractures has been inferred from the separation of the lateral masses measured on the odontoid view. Spence's anatomic study showed that lateral mass separation of > 6.9 mm implied rupture, but radiograph magnification was not taken into account. Transverse ligament rupture should not be inferred with lateral mass separation of < 8.1 mm.

Interpretation of lumbar spine densitometry in women with fractures

Identification of postmenopausal women at risk of developing osteoporotic fractures is a major clinical problem. In this study the use of projected planar lumbar bone density values for individual fracture risk assessment was questioned. Osteodensitometry (DXA) results from 415 normal women, 62 women with previous vertebral compressions, and 76 women with previous low-energy fractures were analyzed, together with their body size and lumbar vertebral body size variables. The following were found: (1) Lumbar vertebral projected bone mineral areal density (BMD) and bone mineral content (BMC) of normal women correlated with body size variables (p < 0.001). (2) Lumbar vertebral body size variables also correlated with body size variables (p < 0.001). Logistic regression analysis of measured and derived physical variables from women without and with vertebral compression fractures (n = 477) showed: (3) The best compression fracture discriminator, significantly better than BMD, was BMC divided by (Hmax/165 cm)1.5 x (D/4.35 cm)1.5, where Hmax is the body height (cm) at the menopause, and D the mean lumbar vertebral diameter of the three mid-lumbar vertebral bodies (cm). This parameter was termed BMCcorr.. ROC analysis showed: (4) At a BMCcorr. true positive ratio of 80% the corresponding uncorrected BMC or BMD true positive ratio was only 60%. The corresponding false positive ratio was 6%. Lumbar osteodensitometry could not be used to identify women with a history of peripheral low-energy fractures. (5) BMCcorr. did not, unlike BMC and BMD, correlate with body size and vertebral size variables. (6) Likewise, an observed correlation between BMC and lean body mass in a subpopulation of 116 normal women was abolished when BMCcorr. replaced BMC.(ABSTRACT TRUNCATED AT 250 WORDS)

Fractures of C1 and C2 in an infant gazelle: a model of the human fracture pattern

Spontaneously occurring fractures of the anterior and posterior synchondroses of C1 and the superior facet of C2 of an immature mammal were analyzed. The posterior C1 injury showed comminution, with involvement of both sides of the synchondrosis. Just below the anterior C1 fracture was an incomplete, comminuted fracture of the C2 superior facet. These fractures, especially the C1 injury, appear similar to the radiographic injury patterns in skeletally immature humans. Presumably the histologic failure patterns in the child would also be similar.

Inadvertent intraspinal placement of a Foley catheter in severe craniofacial injury with associated atlanto-occipital dislocation: case report

A case of fatal, inadvertent, intraspinal placement of a Foley urinary catheter is presented. The patient suffered a severe craniofacial injury with life-threatening epistaxis requiring emergent tamponade with two Foley catheters plus gauze packing. There was an associated atlanto-occipital dislocation. The mechanism of production is discussed, and guidelines to avoid this complication are outlined.

Contrast-enhanced MRI of healed pathologic vertebral compression fracture mimicking active disease in a patient treated for lymphoma

Despite the valuable contribution of MRI, the distinction between benign and malignant compression fractures of the spine is sometimes difficult, and cannot with certainty be based on T1- and T2-weighted signal criteria alone, or on the configuration of the compression fracture. This case report demonstrates that in certain instances neither can gadolinium enhancement specifically make this determination in cases of treated malignancy of the spinal column. Because treated neoplasia having benign histologic characteristics may continue to enhance with IV gadolinium, biopsy evaluation must be undertaken in this setting in order to prove the diagnosis.

Ring fracture of the base of the skull and atlanto-occipital avulsion due to anteroflexion on motorcycle riders in a head-on collision accident

This report concerns a head-on collision accident of a motorcycle at a very high speed (c. 80-100 Km/h) against a bonnet-type automobile, in which both the motorcyclist and pillion rider were injured at the base of the skull by violent anteroflexion of the head due to the force of inertia. A difference in their injuries was: the motorcyclist sustained a 'ring' fracture and the pillion rider an atlanto-occipital avulsion; dural tear. Anteroflexion without impact on the occiput such as described above seems to be a rare causal mechanism of the 'ring' fracture. In addition, the mode of action of the accelerating forces to the heads of the victims along with their physiques may explain the mechanism which caused the different injuries in this accident.

Prevalence and incidence of vertebral deformities

There is a need to identify vertebral fractures from radiographs taken at a single point in time, but considerable controversy surrounds the methods to be used. We extended a data set to comprise baseline radiographs of the thoracic and lumbar spine on an age-stratified random sample of 762 Rochester, Minnesota, women and used revised methods to define vertebral deformities morphometrically. Changes in the method of measuring vertebral heights, changes in the source of normal values for vertebral measurements and changes in the criteria for assessing vertebral deformity had little impact on estimated prevalence and incidence in this population. The prevalence of any vertebral deformity was estimated at 25.3 per 100 Rochester women aged 50 years and over (95% CI, 22.3-28.2), while the incidence of a new deformity in this group was estimated at 17.8 per 1000 person-years (95% CI, 16.0-19.7). Projected nationally, these data suggest that over 500,000 white women in the United States develop vertebral deformities for the first time each year and that over 7 million white women aged 50 years and over might be affected at any given time. These estimates are limited by the absence of a reliable 'gold standard' with which to determine false positive and false negative rates associated with this or any other morphometric method. Information on the health consequences of vertebral deformities of various sorts would be most helpful in choosing between alternative approaches to defining them.

Kinematics of the lumbar spine following pedicle screw plate fixation

This investigation was conducted to determine the kinematic response of the lumbar spine instrumented with transpedicular screws and plates. Seven unembalmed human cadaveric lumbar spines were used. Retroreflective targets were inserted into the bony landmarks of each vertebral body, facet column, and spinous process. The specimen was quasistatically loaded until failure (initial cycle) using an electrohydraulic testing device at a rate of 2.5 mm/sec. After radiography, the specimen was again loaded (injury cycle) to the failure compression determined in the previous cycle. Transpedicular screws then were inserted bilaterally at one level proximal and distal to injury. The stabilized cycle of loading was conducted using the procedure adopted in the injury cycle. Comparative analysis of the localized kinematic data between the stabilized and injured columns indicated a reduction in motion between fixated levels, increasing the rigidity of the column. At levels proximal and distal to fixation, however, motion increased, indicating added flexibility. These alterations in the motion, observed during single-cycle loading, may be further accentuated in vivo, leading to hypermobility and degeneration of the spine.

Multiple myeloma occurring in early stage primary biliary cirrhosis

B-cell neoplasms are not infrequently associated with autoimmune diseases. A 60-year-old man with multiple myeloma developing in an early stage primary biliary cirrhosis was reported. Initially, he had hypergammaglobulinemia with monoclonal gammopathy (IgG-kappa type), elevation of serum IgG and IgM, and positive serum antimitochondrial antibodies. There were compression fractures of the lumbar vertebrae, where bone marrow aspiration revealed proliferating myeloma cells. Liver biopsy revealed destruction of bile duct surrounded by an inflammatory infiltrate, which was consistent with stage I primary biliary cirrhosis. The association suggested the role of immunoregulatory abnormalities in the development of multiple myeloma.

Role of trabecular morphology in the etiology of age-related vertebral fractures

Osteoporotic compression fractures of the spine differ from most other age-related fractures in that they usually are associated with minimal trauma and with loads no greater than those encountered during normal activities of daily living. With aging and osteoporosis, there is progressive resorption of bone, resulting in reductions in bone density, thinning of trabeculae, and loss of trabecular contiguity. These changes in trabecular bone structure are associated with losses in bone strength which are disproportionate to the reductions in bone mass alone. To explain this disproportionate loss of bone strength, the prevailing opinion is that density reductions in the vertebral centrum are accompanied by a reduction in the number of trabeculae, by preferential resorption of horizontal trabeculae, and by hypertrophy of the remaining vertical trabeculae. To evaluate this view of vertebral morphology, we performed three-dimensional stereological analysis of trabecular bone extracted from midsagittal sections of first lumbar vertebral bodies from 12 donors spanning an age of 27-81 years. We found that both the number (R2 = 0.63, P < 0.01) and thickness (R2 = 0.91, P < 0.01) of trabeculae decreased linearly with density (as expressed by bone volume fraction) whereas the spacing between the trabeculae (R2 = 0.61, P < 0.01) increased reciprocally. There were more vertical trabeculae with transverse trabeculae at all densities, and the number of vertical trabeculae changed with density at twice the rate of the number of transverse trabeculae (P < 0.001). These data do not support the prevailing view that there is preferential resorption of horizontal trabeculae or hypertrophy of the remaining vertical trabeculae.(ABSTRACT TRUNCATED AT 250 WORDS)

Architecture and vertebral fracture

Bone strength is determined by mass density, structural arrangement, and the presence of microdamage. This presentation focuses on trabecular microstructure as an element of bone strength, particularly in the syndrome of vertebral compression fracture. The base material comes from transilial biopsies from 90 patients with the crush fracture syndrome and from 34 normal volunteers who underwent transilial biopsy. Trabecular connectivity was compared in these two groups. Patients and normals were then matched for trabecular bone volume (BV/TV). To highlight measures of trabecular connectivity, three general methods for examining trabecular connectivity were applied to the 23 patient-control pairs matched for BV/TV. The conventional method of Parfitt showed that trabecular number was decreased by 11%, trabecular separation was increased by 9%, and trabecular thickness was increased by 9% in patients compared with controls. The method of counting trabecular nodes and trabecular free ends showed that in the patients, free ends were decreased by 37% and nodes were decreased by 37%. The marrow space star volume (the average volume of marrow measured from radii placed at random points within the marrow and extending to trabecular surface) was 36% greater in the patients. All three methods are measures of trabecular connectivity (the density of connections between trabeculae). All three demonstrated less trabecular connectivity in the patients versus controls for identical BV/TV. Patients with vertebral fractures had fewer trabecular elements rather than global thinning of trabeculae. Differences in measures or connectivity were not accompanied by significant differences in any of the measures of bone remodeling dynamics, as examined by tetracycline labels.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of the bone mineral density of the os calcis as an indication of vertebral fracture in women with lumbar osteoarthritis

In women with lumbar osteoarthritis, measurement of the os calcis bone mineral density (BMD) using dual-energy X-ray absorptiometry (DEXA) as an indication of vertebral fracture was evaluated. The in vivo precision of the method was 1.28%. Age- and sex-matched control curves were evaluated using a control of 193 females. The correlation between spine BMD and os calcis BMD was significant (r = 0.65, p << 0.001). For the osteoporotic women without osteoarthritis (n = 34), there was no significant difference in the spine and the os calcis Z-scores (-1.99SD and -1.83SD respectively). Whereas for osteoporotic women with osteoarthritis (n = 30) the spine Z-score was -0.49SD the os calcis Z-score was -1.92SD. The difference was significant (p < 0.001). Receiver operating characteristic (ROC) curves demonstrate the superiority of the os calcis as a measurement site over the lumbar spine, in correlation with existing crush fractures in the presence of osteoarthritis. It is concluded that when lumbar osteoarthritis occurs measurement of the os calcis BMD using DEXA is clinically useful for the estimation of bone mass.

Vertebral fractures in newborn calves

A prospective study on vertebral fractures in newborn calves is described. Vertebral fractures were found in 7.0% of necropsied calves of the Danish Holstein-Friesian (SDM) and Red Danish Dairy (RDM) breeds. Cases were not found in submitted calves of the Jersey breed or beef breeds. At least in beef breeds this was probably due to the low number necropsied. The rate of vertebral fractures in SDM and RDM breeds and between males and females were similar. Most cases occurred in calves born by heifers, and manual traction force had been applied in all cases. All fractures which in most cases consisted of a simple epiphysiolysis were located at the thoraco-lumbar area, and especially the posterior epiphysis of T13 was afflicted.

Temporal variations in iliac trabecular bone formation in vertebral osteoporosis

The histologic heterogeneity of osteoporosis relative to normal controls has attracted great interest. There has been controversy as to whether patients with high turnover osteoporosis may convert to a normal or low turnover form, and vice versa. We have studied 44 patients over 12 years by dynamic histomorphometry and 85Sr kinetics+calcium balance performed within 60 days in 20 patients (Group 1) and 75-808 days apart in the remainder (Group 2). In the first group, the histologic tissue level bone formation rate (BFR/BV or BFR/BS) was predictive of the 85Sr measurements of bone formation (r = 0.66 P < 0.01). There was no statistically significant correlation in Group 2 and the regression coefficients were significantly different (P = 0.01). Periodic regression was used to determine if seasonal changes were responsible for this loss of correlation; none was found that was of statistical significance. No systematic changes with time in bone formation were found in Group 2 during the period of observation; nor were consistent secular changes detected when the data for both groups were examined according to procedure date. In conclusion, bone formation may change with time in postmenopausal osteoporosis. Evidence that these changes are systematic was not found and this has implications for the design of treatment studies.

[Bone injuries in gunshot wounds of the neck]

Some typical bone injuries by shots to the back of the neck are reported. Significant Findings in skeletal remains could be detected even after two decades.

Vertebral structure and strength in vivo and in vitro

The incidence of vertebral fragility fractures has increased 2-4-fold during the past 30 years and the rate of increase is the same for both men and women. To arrest or reverse this increase, thorough understanding of normal, age-related changes in bone structure and strength is crucial. The human vertebral body is constructed to provide maximum strength with minimum bone mass. The strength is the sum of bone size, cortical thickness, trabecular architecture, and bone mass. With age, all these factors change due to the remodeling process, but the decline in bone strength is much more pronounced than the decline in mass. In individuals with very low bone mass, this discrepancy between mass and strength is even more marked. Structural studies have all shown a disruption of the trabecular network with age--mainly caused by perforation of horizontal supporting struts. These changes begin in the vertebral center. Later, a decline in cortical thickness is disclosed. The biomechanical consequence of this is a 4-6-fold decrease in vertebral strength during normal aging. As the structural changes cannot be reversed, it is difficult to increase bone strength by therapeutic regimens. Focus should therefore be placed on prevention. Three avenues are suggested: (1) to use the vast amount of existing biological data in a computer model to increase the understanding of the relationship among bone structure, mass, and strength, and to help identify the intervention regimens offering the best prospects of success; (2) to investigate characteristics of load-bearing trabecular bone that does not fracture; and (3) to focus more on life-style factors.

[An anatomic study of transpedicular posterior fixation of spine and its clinical application]

Intact anatomic specimens of spinal column from T8-L5 were obtained and the height and width of vertebral pedicles, the distance between the pedicle to the upper and lower borders of the vertebral body, the angle of inclination of the coronal surface of vertebral pedicles, and other parameters were measured. Simulating pedicle screw implant in operation, K-wires were inserted into the pedicles and after taking X-ray films the pedicles were sectioned transversely. A series of morphologic parameters of the pedicles were obtained. The distances between the two K-wires' entry and exit points, and between the two pedicles of the same or the adjacent vertebra were measured. The relationships of the sites of determining the pedicle screw site was evaluated also from roentgenograms. Twenty two patients of thoracolumbar fracture were treated. The vertebral body height, kyphotic deformity and the displacement were corrected obviously. After operation the neural functions from incomplete paraplegia were recovered. Several problems about the pedicle screw implant technique were discussed.