A Precise and Reliable Method of Determining Lesion Size in Osteonecrosis of the Femoral Head Using Volumes.

BACKGROUND: To ascertain whether volumetric measurements to characterize lesion size in osteonecrosis of the femoral head using magnetic resonance imaging (MRI) and 3D software are more precise than other previously described methods. METHODS: Twenty-four patients were included in the study. Two musculoskeletal radiologists independently analyzed radiographs and MRIs using the methods described by Kerboul et al [9], Koo and Kim [10], and Cherian et al [11]. Volumetric measurements were calculated from the MRIs using 3D imaging software. Inter-rater reliability was calculated for all 4 methods using the interclass correlation coefficient (ICC). Levene's test was used to compare the variance across methods, serving as a measure of precision of each method. RESULTS: An ICC value of 0.81 was calculated for the volumetric measurements. The ICC values of the Kerboul et al, Koo and Kim, and Cherian et al methods were 0.94, 0.61, and 0.49, respectively. Levene's test for homogeneity of variance using absolute deviations showed the variance was not equal across methods (P < .01). The variance and the corresponding 95% confidence interval were calculated showing that the variance for the volumetric measurements was the smallest among the 4 methods examined, indicating that the volumetric measurements are more precise in characterizing lesion size as compared to the other methods. CONCLUSION: Volumetric measurements of lesion size using 3D MRI imaging software to assess osteonecrosis of the femoral head are more precise than previously described methods and have excellent interobserver reliability. A 3D MRI assessment of volume of osteonecrosis in the femoral head may be useful in clinical decision-making.

Characteristics of Cervical Spine Motion in Different Types of Cervical Alignment: Kinematic MRI Study.

STUDY DESIGN: Retrospective study. OBJECTIVE: To evaluate how each type of sagittal cervical alignment affects the motion of the upper and subaxial cervical spine using kinematic magnetic resonance imaging. SUMMARY OF BACKGROUND DATA: The sagittal malalignment of the cervical spine from degeneration in the subaxial cervical spine reflects a disruption in the kinematic properties of the cervical spine and affects the motion of adjacent segments. Changes in the sagittal parameters and kinematics of the upper cervical spine and upper thoracic spine due to the kyphosis are unknown. METHODS: Kinematic magnetic resonance imaging of the cervical spine in neutral position from 311 patients, including 90 lordotic, 90 straight, 90 global kyphotic, and 41 segmental kyphotic were analyzed. The lordotic angle at the upper and lower cervical spine, and T1 slope were measured in the neutral position and again in flexion and extension for dynamic analysis. RESULTS: The number of levels with significant disk degeneration was higher in the global kyphosis group. In the global kyphosis group, neutral sagittal parameters showed some characteristics of compensation to the malalignment. Compared with the lordotic group, patients with global kyphosis demonstrated significantly higher lordotic angle of the upper cervical spine and more horizontal T1 slope. The dynamic evaluation showed greater range of motion of the entire cervical spine and subaxial cervical spine in younger patients. However, we still found greater range of motion of the occipito-atlanto-axial complex in global kyphosis, even when controlling for age and number of levels with significant disk degeneration. CONCLUSION: Sagittal malalignment of the cervical spine affects all parts of the cervical motion complex. The global kyphotic alignment of subaxial cervical spine affects the kinematic properties of the occipito-atlanto-axial complex and upper thoracic spine to compensate for the alteration of cervical alignment. These differences are not seen in straight and segmental kyphosis. LEVEL OF EVIDENCE: Level 3.