K. Nakajima et al., FACTORS RELATED TO THE SEVERITY OF MYELOPATHY IN ATLANTOAXIAL INSTABILITY, Spine (Philadelphia, Pa. 1976), 21(12), 1996, pp. 1440-1445
Study Design. This study retrospectively reviewed the factors seemingl
y associated with neurologic symptoms in 46 patients with atlantoaxial
instability. Objectives. This study revealed the most significant fac
tors related to the severity of myelopathy and surgical prognosis of a
tlantoaxial instability. Summary of Background Data. Spinal morphometr
y has been reported to provide a useful means of predicting the progno
sis of cervical spondylotic myelopathy after surgery. However, no quan
titative and statistical evaluation of this method has been reported i
n atlantoaxial instability. Furthermore, there is a poor correlation b
etween neurologic deficit and plain radiographic findings of atlantoax
ial instability. Methods. Four items of clinical information were inve
stigated, six parameters were measured on radiographs, and two morphom
etric parameters of the spinal cord were measured. These parameters we
re used as predictor variables. Three multiple regression analyses wer
e carried out, using pre- and post-treatment Japanese Orthopaedic Asso
ciation scores as criteria variables. Results. Pretreatment Japanese O
rthopaedic Association scores were found to correlate with the spinal
compression ratio, history of trauma, and the C1-C2 ratio. Postoperati
ve Japanese Orthopaedic Association scores correlated with preoperativ
e Japanese Orthopaedic Association scores, the C1-C2 ratio, and the co
mpression ratio, The multiple coefficient of determination was 93.2%.
The recovery rate correlated with the C1-C2 ratio and age. Conclusions
. Neurologic symptoms were found to be closely related to the morpholo
gy of the spinal cord. Compression ratio and the C1-C2 ratio were foun
d to be useful in understanding neurologic symptoms. The C1-C2 ratio s
eems to serve as an important predictor of the prognosis of atlantoaxi
al instability.