Small-animal PET/CT assessment of bone microdamage in ovariectomized rats.

UNLABELLED: Microdamage in bone contributes to bone fragility in postmenopausal women. Therefore, it is important to find a noninvasive method to detect microdamage in living bone. PET with (18)F-fluoride has been used for skeletal imaging in clinical studies. However, few studies are undertaken to investigate bone microdamage associated with osteoporosis in vivo using noninvasive means. The aim of our study was to analyze the impact of osteoporosis due to estrogen deficiency on the occurrence of microdamage by observing the change in the uptake of (18)F-fluoride in the tibiae of ovariectomized rats after fatigue loading with small-animal PET/CT. We also explored the feasibility of noninvasive detection of bone microdamage in vivo using a small-animal PET/CT scanner specially designed for rodent study. METHODS: Rats were randomized into 2 groups: ovariectomy and sham surgery. These rats were imaged using a dedicated small-animal PET scanner with (18)F-fluoride after the left tibiae were loaded cyclically under the axial compression. The fluoride uptake values were quantified in the tibial mid shafts, and the tibia was obtained for histomorphometric measurements of bone microdamage and osteocyte density. Bone mineral density at the fourth lumbar vertebra and right femur were measured using dual-energy x-ray absorptiometry. RESULTS: PET image intensity was significantly increased (P < 0.05) in the loaded tibia of the ovariectomy group, compared with that of the sham group. Histomorphometry showed that both crack density and crack length in the loaded tibia were significantly higher (P < 0.05) in ovariectomized rats than in sham rats. The PET image intensity in the loaded tibia was significantly positively correlated with crack length and crack density (which show in histomorphometric measurement) (P < 0.05). CONCLUSION: Both small-animal PET/CT and histomorphometric measurement provided evidence that bone microdamage is significantly increased after estrogen depletion. The strong correlation between these 2 measurements suggests that small-animal PET/CT is a useful noninvasive means to detect bone microdamage in vivo.

Assessment of ligamentous injury in patients with thoracolumbar burst fractures using MRI.

BACKGROUND: No consensus has been reached on the optimal radiographic evaluation of thoracolumbar burst fractures. The role of MRI in the treatment decision is not fully documented. The objectives was to measure the agreement of MRI in detecting posterior ligamentous complex (PLC) and posterior longitudinal ligament (PLL) injury, and to determine whether the findings by MRI is correlated with the results of plain radiography and computed tomography (CT) scanning as well as neurological examination and with the treatment planning. METHODS: Sixty-one patients with acute thoracolumbar burst fracture were retrospectively reviewed for the presence of supraspinous ligament (SSL), interspinous ligament (ISL) or posterior longitudinal ligament (PLL) injury. The overall interobserver agreement between the three different observers was assessed by a kappa coefficient for multiple raters. The status of ligaments was correlated with the neurological function as assessed by Frankel scale and fracture severity as defined by the Load Sharing Classification. These patients were surgically treated according to the Load Sharing Classification and followed up for at least 5 years. RESULTS: The kappa coefficients for ISL or SSL injury ranged 0.601 to 0.736, representing substantial to almost perfect agreement, whereas the kappa coefficients for PLL injury were 0.441 to 0.574, representing moderate agreement. No significant difference (P > 0.05) of Frankel scale or load sharing score was found between patients with and without ligamentous injuries. Satisfactory results were achieved in all patients regarding the clinical and radiological assessment. CONCLUSIONS: MRI is reliable for detecting the ligamentous injury, especially PLC injury in thoracolumbar burst fractures but the ligamentous injury as shown by MRI is not correlated with the neurological function or fracture severity. As MRI finding is of little value in treatment planning of thoracolumbar burst fractures, MRI examination is not necessary to be used routinely for excluding occult ligamentous injury.

A review of the management of thoracolumbar burst fractures.

BACKGROUND: Burst fractures account for more than half of all thoracolumbar fractures, which often cause a neurologic deficit and present a significant economic burden to the family and society. Accepted methods of treatment of thoracolumbar burst fractures include conservative therapy, posterior reduction and instrumentation, and anterior decompression and instrumentation. However, the management of thoracolumbar burst fractures has been the subject of much controversy. METHODS: Publications reporting clinical data relating to the thoracolumbar burst fractures were reviewed. These articles were determined via review of the results of PubMed searches and articles gathered through compilation of references from those articles. RESULTS: There exist different criteria for the choice of the management based on the severity of kyphotic deformity, canal compromise, vertebral height loss, and neurologic status. To our knowledge, none of the existing criteria for the treatment of thoracolumbar burst fractures are generally accepted. CONCLUSIONS: In thoracolumbar burst fractures without a neurologic deficit, there is no superiority of conservative therapy over operative therapy. When the neurologic involvement is significant, the choice of operative management is advised. Also, there is no obvious superiority of one approach over the other.

Interobserver and intraobserver reliability in the load sharing classification of the assessment of thoracolumbar burst fractures.

STUDY DESIGN: The Load Sharing Classification of spinal fractures was evaluated by 5 observers on 2 occasions. OBJECTIVE: To evaluate the interobserver and intraobserver reliability of the Load Sharing Classification of spinal fractures in the assessment of thoracolumbar burst fractures. SUMMARY OF BACKGROUND DATA: The Load Sharing Classification of spinal fractures provides a basis for the choice of operative approaches, but the reliability of this classification system has not been established. METHODS: The radiographic and computed tomography scan images of 45 consecutive patients with thoracolumbar burst fractures were reviewed by 5 observers on 2 different occasions 3 months apart. Interobserver reliability was assessed by comparison of the fracture classifications determined by the 5 observers. Intraobserver reliability was evaluated by comparison of the classifications determined by each observer on the first and second sessions. Ten paired interobserver and 5 intraobserver comparisons were then analyzed with use of kappa statistics. RESULTS: All 5 observers agreed on the final classification for 58% and 73% of the fractures on the first and second assessments, respectively. The average kappa coefficient for the 10 paired comparisons among the 5 observers was 0.79 (range 0.73-0.89) for the first assessment and 0.84 (range 0.81-0.95) for the second assessment. Interobserver agreement improved when the 3 components of the classification system were analyzed separately, reaching an almost perfect interobserver reliability with the average kappa values of 0.90 (range 0.82-0.97) for the first assessment and 0.92 (range 0.83-1) for the second assessment. The kappa values for the 5 intraobserver comparisons ranged from 0.73 to 0.87 (average 0.78), expressing at least substantial agreement; 2 observers showed almost perfect intraobserver reliability. For the 3 components of the classification system, all observers reached almost perfect intraobserver agreement with the kappa values of 0.83 to 0.97 (average, 0.89). CONCLUSIONS: Kappa statistics showed high levels of agreement when the Load Sharing Classification was used to assess thoracolumbar burst fractures. This system can be applied with excellent reliability.