Slight head extension: does it change the sagittal cervical curve?

Deed E. Harrison1, Donald D. Harrison2, Tadeusz J. Janik3, , Burt Holland4 and Leonard A. Siskin5

 (1)
     Elko, Nevada, USA
 (2)
     CBP Nonprofit, Inc, Harvest, Alabama, USA
 (3)
     Time Domain Corporation, Cummings Research Park, 7057 Old Madison Pike, Huntsville, Alabama 35806, USA
 (4)
     Department of Statistics, Temple University, Philadelphia, Pennsylvania, USA
 (5)
     Green Brook, New Jersey, USA
 

Abstract. It is commonly believed that slight flexion/extension of the head will reverse the cervical lordosis. The goal of the
present study was to determine whether slight head extension could result in a cervical kyphosis changing into a lordosis.
Forty consecutive volunteer subjects with a cervical kyphosis and with flexion in their resting head position had a neutral
lateral cervical radiograph followed immediately by a lateral cervical view taken in an extended head position to level the bite
line. Subjects were patients at a spine clinic in Elko, Nevada. All radiographs were digitized. Global and segmental angles of
the cervical curve were compared for any change in angle due to slight extension of the head. The average extension of the
head required to level the bite line was 13.9? This head extension was not substantially correlated with any segmental or
global angle of lordosis. Subjects were categorized into those requiring slight head extension (0?13.9? and those requiring a
significant head extension (>13.9?. In the slight head extension group, the average change in global angle between posterior
tangents on C2 and C7 was 6.9? and 80% of this change occurred in C1-C4. In the significant head extension group, the
average change in global angle between posterior tangents on C2 and C7 was 11.0? and the major portion of this change
occurred in C1-C4. Out of 40 subjects, only one subject, who was in the significant head extension group and had only a
minor segmental kyphosis, changed from kyphosis to lordosis. The results show that slight extension of the head does not
change a reversed cervical curve into a cervical lordosis as measured on lateral cervical radiographs. Only small extension
angle changes (mean sum=4.8? in the upper cervical segments (C2-C4) occur in head extension of 14?or less.