European Journal of Orthodontics 13 (1991) 397-403
) 1991 European Orthodontics Society
The effect of orthognathic surgery on head posture Ceib Phillips, Michael D. Snow, Timothy A. "Purvey, and William R. Proffit Departments of Orthodontics, and Oral and Maxillofacial Surgery, University of North Carolina School of Dentistry, Chapel Hill, USA
SUMMARY Changes in resting head and neck posture were studied in 201 patients following five different orthognathic surgery procedures:
(1) (2) (3) (4) (5)
LeFort I osteotomy for superior repositioning (intrusion) of the maxilla (n=45); bilateral sagittal split ramus osteotomy for mandibular advancement (A7=78); mandibular setback (n= 19); combined maxillary intrusion and mandibular advancement (n=46); combined maxillary intrusion and mandibular setback (n=13).
Introduction
Since the work of Broca in the 1860's, head posture has been recognized as an important influence on craniofacial proportions. The relationships between posture and craniofacial development have been the subject of a number of recent studies (Solow et al., 1984; Kylamarkulaand Huggare, 1985; Cannon, 1985; Fjellvang and Solow, 1986; Solow and Siersbaek-Nielsen, 1986; Tallgren and Solow, 1987; Hellsing, 1987, 1989; Hellsing and Hagberg, 1990). Head extension has been correlated with increased cranial base angle and increased mandibular inclination to the cranial base and the maxillary plane, as well as increased antero-posterior dimensions and increased anterior face height (Solow and Tallgren, 1976, 1977; Posnick, 1978; Showfety el al., 1987). Impaired nasal respiration can result in head extension (Linder-Aronson, 1970, 1979; Vig et al., 1980). Solow and Kreiborg (1977) postulated a chain of events that could result in changes in dentofacial morphology:
obstruction of the airway, neuromuscular feedback producing postural change, soft tissue stretching, and differential forces on the dentition, i.e. the 'soft tissue stretching' hypothesis. Very few studies have approached the question of the relationship between head posture and morphology by observing longitudinally whether changes in morphology produced by a surgical procedure are associated with changes in posture, or whether changes in posture have any impact on post-surgical stability. Schellhase (1984) observed significant headflexionimmediately after maxillary intrusion in a sample of 32 patients. Wenzel and co-workers (1989a) reported significant head extension (jcd = 2.7 degrees) 1 year after mandibular setback with a bilateral vertical ramus osteotomy in a group of 52 patients. Head extension was statistically associated with the decrease in mandibular length in these patients (Wenzel et al., 19896) although the proportion of variation explained was quite small (r2 = 0.09). The purpose of this study was to determine whether a temporary or
Downloaded from by guest on May 30, 2015
Head and neck posture were measured on standardized serial cephalograms taken in natural head position prior to, immediately after, and 1 year after surgery for each subject. Immediately after surgery, there was flexion of the head as measured by the craniovertical and craniocervical angles in all of the groups except the mandibular setback group, which showed little change. By 1 year post-surgery, the mean craniovertical and craniocervical angles were approximately the same as before surgery in the groups with one-jaw surgery. Statistically significant head flexion at 1 year (P0.4 in all analyses), indicating that no significant bias was introduced by the combination of the two methods. The use of two methods to obtain the sitting natural head position cephalograms would be expected to increase the random variation in the measures and, therefore, to produce conservative statistical results. Since there was no reason to treat the presence of a bubble as a confounding factor, a twofactor repeated measures analysis of variance (Cole and Grizzle, 1966) using PROC GLM in SAS (1985) was performed on the presurgery,
399
CHANGES IN HEAD POSTURE
Results
immediate post-surgery, and 1-year values for each angle to test whether there was a significant time effect, surgical procedure effect, or a time by procedure interaction. Because the time by procedure interaction term was significant for all angles (P
) 1991 European Orthodontics Society
The effect of orthognathic surgery on head posture Ceib Phillips, Michael D. Snow, Timothy A. "Purvey, and William R. Proffit Departments of Orthodontics, and Oral and Maxillofacial Surgery, University of North Carolina School of Dentistry, Chapel Hill, USA
SUMMARY Changes in resting head and neck posture were studied in 201 patients following five different orthognathic surgery procedures:
(1) (2) (3) (4) (5)
LeFort I osteotomy for superior repositioning (intrusion) of the maxilla (n=45); bilateral sagittal split ramus osteotomy for mandibular advancement (A7=78); mandibular setback (n= 19); combined maxillary intrusion and mandibular advancement (n=46); combined maxillary intrusion and mandibular setback (n=13).
Introduction
Since the work of Broca in the 1860's, head posture has been recognized as an important influence on craniofacial proportions. The relationships between posture and craniofacial development have been the subject of a number of recent studies (Solow et al., 1984; Kylamarkulaand Huggare, 1985; Cannon, 1985; Fjellvang and Solow, 1986; Solow and Siersbaek-Nielsen, 1986; Tallgren and Solow, 1987; Hellsing, 1987, 1989; Hellsing and Hagberg, 1990). Head extension has been correlated with increased cranial base angle and increased mandibular inclination to the cranial base and the maxillary plane, as well as increased antero-posterior dimensions and increased anterior face height (Solow and Tallgren, 1976, 1977; Posnick, 1978; Showfety el al., 1987). Impaired nasal respiration can result in head extension (Linder-Aronson, 1970, 1979; Vig et al., 1980). Solow and Kreiborg (1977) postulated a chain of events that could result in changes in dentofacial morphology:
obstruction of the airway, neuromuscular feedback producing postural change, soft tissue stretching, and differential forces on the dentition, i.e. the 'soft tissue stretching' hypothesis. Very few studies have approached the question of the relationship between head posture and morphology by observing longitudinally whether changes in morphology produced by a surgical procedure are associated with changes in posture, or whether changes in posture have any impact on post-surgical stability. Schellhase (1984) observed significant headflexionimmediately after maxillary intrusion in a sample of 32 patients. Wenzel and co-workers (1989a) reported significant head extension (jcd = 2.7 degrees) 1 year after mandibular setback with a bilateral vertical ramus osteotomy in a group of 52 patients. Head extension was statistically associated with the decrease in mandibular length in these patients (Wenzel et al., 19896) although the proportion of variation explained was quite small (r2 = 0.09). The purpose of this study was to determine whether a temporary or
Downloaded from by guest on May 30, 2015
Head and neck posture were measured on standardized serial cephalograms taken in natural head position prior to, immediately after, and 1 year after surgery for each subject. Immediately after surgery, there was flexion of the head as measured by the craniovertical and craniocervical angles in all of the groups except the mandibular setback group, which showed little change. By 1 year post-surgery, the mean craniovertical and craniocervical angles were approximately the same as before surgery in the groups with one-jaw surgery. Statistically significant head flexion at 1 year (P0.4 in all analyses), indicating that no significant bias was introduced by the combination of the two methods. The use of two methods to obtain the sitting natural head position cephalograms would be expected to increase the random variation in the measures and, therefore, to produce conservative statistical results. Since there was no reason to treat the presence of a bubble as a confounding factor, a twofactor repeated measures analysis of variance (Cole and Grizzle, 1966) using PROC GLM in SAS (1985) was performed on the presurgery,
399
CHANGES IN HEAD POSTURE
Results
immediate post-surgery, and 1-year values for each angle to test whether there was a significant time effect, surgical procedure effect, or a time by procedure interaction. Because the time by procedure interaction term was significant for all angles (P
