Spinal and shoulder complex posture. II: thoracic alignment and shoulder complex position in normal

Transcription

1 27- Spinal and shoulder complex posture. II: thoracic alignment and shoulder complex position in normal and osteoporotic women Elsie Culham and Malcolm Peat School of Rehabilitation Therapy, Queen s University, Kingston, Ontario Thoracic spine and shoulder complex posture were measured in 57 women over the age of 50. On the basis of thoracic spine measures, the women were divided into normal posture (n 27), thoracic kyphosis (n 18) and thoracolumbar = = kyphosis (n 12) posture = groups. Analysis of variance was used to determine if shoulder complex postural measures differed in the three groups. In the sagittal plane, both abnormal posture groups had significantly greater forward angulation of the scapula and humeral extension compared with the normal posture group. In the transverse plane, scapular protraction and the angle between the scapular spine and clavicle were significantly greater in the thoracic kyphosis group compared with the other two groups. In the coronal plane, the abduction angle of the humerus was significantly less in the thoracic kyphosis group compared with the normal posture group. No difference was found in scapular position in this plane. Although differences were apparent between the posture groups, many of the clinical hypotheses regarding the effect of spinal posture on shoulder complex position were not substantiated by the results of this study. Introduction It is generally recognized that abnormal sagittal plane alignment of the cervical and thoracic spine can contribute to pain and dysfunction in the neck and shoulder region.l-6 Specifically, several authors have suggested that an exaggerated thoracic kyphosis alters the resting Address for correspondence: Elsie Culham, School of Rehabilitation Therapy, Louise D Acton Building, Queen s University, Kingston, Ontario K7L 3N6, Canada. position of the shouldered complex resulting in a forward- or round-shoulder posture.2,6,7 The scapula is described as following the contour of the thorax and is said to shift anterolaterally or to assume a more protracted position in subjects with increased thoracic kyphosis. In addition, the scapula is thought to rotate such that the glenoid cavity has an increased downward inclination.6-8 Kessler and Hertling7 stated that the freely hanging humerus assumes a more abducted position relative to the scapula and that tension is lost in the superior joint structures. An increase in the inter-

2 28 nally rotated position of the arms is said to occur due to the protracted position of the scapula.9 The consequences of the altered position are postulated to include lengthening or shortening of muscle, muscle weakness and changes in the direction of muscle pull as well as limitation of upper extremity range of motion.2,3 Rehabilitation efforts are often aimed at restoration of the normal position and function by stretching structures assumed to be contracted and strengthening musculature assumed weak due to prolonged stretch.l However, despite the various clinical observations regarding the detrimental effects of abnormal spinal posture on shoulder complex position, no studies could be found in which the claims were substantiated by objective measurement. The purpose of this part of the study was to determine if, and to what extent, shoulder complex position was affected by alignment of the thoracic spine in the sagittal plane. An older female population was chosen for study as previous research has demonstrated that postural changes are age related and are greater in females than males.11,12 In addition, the incidence of spinal osteoporosis, which is known to affect sagittal plane spinal alignment, is higher in women. 13~--15 Methodology A detailed description of the technique used to measure spinal and shoulder complex posture is found in part I* (Figure 1). Since the linear measures of scapular position were compared across subjects in this part of the study it was necessary to normalize these measures to account for differences in subject size. Both measures (Yabs and Zabs) were normalized by dividing by the length of the clavicle (three-dimensional distance between the landmarks on the medial and lateral ends of the clavicle). The resulting measures were labelled Ynor and Znor respectively. * Clinical Rehabilitation 1993; 7: Figure 1 Angular measures of shoulder complex position. (A) Sagittal plane. ScSg, forward angulation of the medial border of the scapula; HSg, flexion angle of the humerus relative to the vertical. (B) Coronal plane. ScCo, abduction angle of the scapula; CICo, elevation of the clavicle from medial to lateral; HCo. abduction angle of the humerus. (C) Transverse plane. ScTr, protraction angle of the scapula; CITR, retraction angle of the clavicle; HTr, internal rotation angle of the humerus.

3 29 Subjects Thoracic posture and shoulder complex position were measured in a total of 57 women between the ages of 50 and 85 years. Thirty-six of the subjects were recruited from the community. Two of these subjects were being treated for osteoporosis. Twenty-one women with a diagnosis of osteoporosis were recruited from an outpatient metabolic clinic of a local hospital. Fifteen of these subjects had radiographic evidence of vertebral fracture at at least one spinal level. Exclusion criteria included presence of a cardiac pacemaker, history of neurological disorder, history of surgery involving the spine and shoulder complex and a significant scoliosis of the spine. Subjects had to be medically stable and be able to assume and maintain a standing position for a minimum of 10 minutes without discomfort. The procedure was explained to the subjects and all gave informed consent prior to their participation in the study. Postural subgroups Subjects were classified into one of three postural groups on the basis of the values obtained for thoracic kyphosis and upper thoracic slope (Figure 2). The groups resulting from this classification were: 1) Thoracic kyphosis: 18 subjects had a thoracic kyphosis value of greater than 42 degrees, higher than any of the values found in normal young women in a pilot study. These individuals were placed in the thoracic kyphosis posture group. 2) Thoracolumbar kyphosis: this group included subjects in whom the location of the kyphotic curvature was low, at the thoracolumbar junction or in the lumbar region. Criteria for inclusion in this group included an upper thoracic slope of greater than or equal to 20 degrees and a kyphosis value of less than 35 degrees. Thoracolumbar kyphosis was evident in the osteoporotic subjects whose fractures primarily involved the lower thoracic or lumbar vertebrae, but was also seen in several of the women recruited from the com- met the criteria for munity. Twelve subjects thoracolumbar kyphosis and were included in this group. 3) Normal posture: thoracic posture was considered to be normal in the remaining 27 subjects who were subsequently placed in the normal posture group. The two abnormal posture groups are similar to the hollow round back and lower acute kyphosis postures described by Itoil6 for women with spinal osteoporosis. Descriptive statistics for age, height and weight of the subjects in the three postural groups are found in Table 1. Figure 2 Classification of spinal posture into three groups on the basis of values obtained for thoracic kyphosis and upper thoracic slope Table 1 Physical characteristics of subjects

4 30 Statistical analysis The mean values of age, height.. and mass as well as means of the spinal and shoulder com- across the three plex measures were compared postural groups using a one-way analysis of variance (ANOVA). In the case of a significant F-ratio a post hoc Scheffe test was completed to determine where the differences were. A level of p < 0.05 was chosen as the maximum level for statistical significance for all ANOVA analyses. Systat (Systat Inc., Evanston, IL) statistical software was used for all analyses. Results Posture subgroups Although the mean age was greater and the mean mass less in the thoracic kyphosis group than in the other two postural groups the differences were not statistically significant. Similarly, there were no significant differences in mean height among the three postural subgroups (p > 0.05). The spinal posture measures and results of statistical analyses are presented in Table 2. The mean kyphosis angle was much greater in the thoracic kyphosis group than in the other two 38.46; p < = postural groups (F 0.001). Upper thoracic slope was greatest in the thoracic kyphosis group followed by the thoracolumbar kyphosis group. The mean was significantly different for all comparisons. The lower thoracic slope was greatest in the thoracic kyphosis group and lowest in the thoracolumbar kyphosis group. The differ ; ence between groups was significant (F = p < 0.001). Post hoc analyses revealed that the difference was significant for all comparisons. Shoulder complex position Sagittal plane Results of analyses of sagittal plane measures are presented in Table 3. The medial border of the scapula was angled forward degrees on average in the normal posture group. This angle was significantly greater, and degrees in the thoracolumbar and thoracic kyphosis groups, respectively. The relative angle between the upper thoracic spine and the medial border of the scapula (ScSgR) was significantly increased in the thoracic kyphosis group compared with the other two postural groups. The humerus was flexed a mean of 1.85 degrees from the vertical in the normal posture group. This compared with a mean angle of 5 degrees extension in both the abnormal posture groups. There was no difference in the humeral angle relative to the medial border of the scapula among the three groups (p > 0.05). Transverse plane Results of analyses of transverse plane Table 2 Thoracic spine measures in postural groups All values in degrees. SD = standard deviation; UTS = slope of the upper thoracic spine measured from T1 downward; LTS = slope of the lower thoracic spine measured from T12 upward; K = thoracic kyphosis angle, derived by summing UTS and LTS.

5 31 measures are presented in Table 4. The mean retraction angle of the clavicle (CITr) was degrees in the normal posture group. This was not significantly different from a mean of and degrees in the thoracolumbar and thoracic kyphosis group respectively. The protraction angle of the scapula (ScTr) and the relative angle between the spine of the scapula and clavicle (CITrR) were significantly greater in the group with thoracic kyphosis compared with the other groups. The humeral angle in the transverse plane was the most variable of all the shoulder complex measures as indicated by the standard deviations. This angle was less in the thoracic kyphosis group, compared to the other two groups, but the difference was not statistically significant. Humeral rotation relative to the spine of the scapula was lower in the thoracic kyphosis group and higher in the thoracolumbar kyphosis group compared with the normal posture group. The difference between the two abnormal posture groups was significant. Coronal plane Results of analyses of coronal plane measures are presented in Table 5. The angle of the medial border of the scapula to the horizontal was degrees in the normal posture group. This angle was lower in the two abnormal posture groups but the difference was not significant (p < 0.05). The angle of elevation of the clavicle from medial to lateral was 7.13 degrees in the normal posture group. This angle was increased in both abnormal posture groups with the greatest difference occurring between the normal and thoracolumbar kyphosis groups. The humeral abduction angle was less in both with the nor- abnormal postural groups compared mal group. Post hoc analysis revealed that the difference was significant only between the thoracic kyphosis and normal group. The abduction angle of the humerus relative to the scapula (HCoR) was lowest for the thoracic kyphosis group. However, the difference among groups was not statistically significant. Linear measures Results of analysis of the linear measures are presented in Table 6. The normalized linear distance from Tl to the scapular centre along the y (Ynor) and z (Znor) axes were not significantly different in the postural groups. Table 3 Sagittal plane shoulder complex measures in postural groups All values in degrees. SD = standard deviation; ScSg = angle of forward tilt of the medial border of the scapula to the vertical; ScSgR = relative angle between the medial border of the scapula and the upper thoracic spine derived by subtracting ScSg from UTS; HSg = angle of the long axis of the humerus to the vertical, a positive value indicating flexion; HSgR = angle of the humerus relative to the medial border of the scapula.

6 32 Table 4 Transverse plane shoulder complex measures in postural groups All values in degrees. SD = standard deviation; ScTr = the protraction angle of the scapular spine relative to a coronal axis defined by a line connecting the roots of the right and left scapular spines; CITr = the retraction angle of the clavicle relative to the coronal axis as defined above; CITrR = the angle between the clavicle and the spine of the scapula in the transverse plane; HTr = the angle of internal rotation of the humerus; HTrR = internal rotation angle of the humerus relative to the spine of the scapula. Table 5 Coronal plane shoulder complex measures in postural groups All values in degrees. SD = standard deviation; ScCo = scapular abduction angle measured as the lateral angle formed between the medial border of the scapula and the horizontal; CICo = the medial to lateral angle of elevation of the clavicle; HCo = the abduction angle of the humerus relative to the vertical; HCoR = the abduction angle of the humerus relative to the medial border of the scapula.

7 33 Table 6 Linear shoulder complex measures in postural groups All values in cm. SD = standard deviation; YNor = the linear distance in centimetres from T1 to the centre of the three scapular landmarks along the y axis, normalized by dividing by the length of the clavicle; ZNor = linear distance from T1 to the centre of the three scapular landmarks, normalized by dividing by the length of the clavicle. Discussion It has been hypothesized that changes in sagittal plane posture, specifically thoracic kyphosis and forward-head posture, result in changes in the resting position of the shoulder complex. The results of this study indicate that an increase in anteroposterior curvature of the spine, regardless of the level at which it occurs, causes an increase in upper thoracic slope which could contribute to a forward head position. However, it is also evident from the results that the position of the skeletal components of the shoulder complex was dependent on the location of the curve. It is not surprising that changes in sagittal plane spinal posture affected the sagittal plane shoulder complex position measures, although no clinical reports regarding the effect of postural changes on the shoulder complex position in this plane have been found. Forward angulation of the medial border of the scapula was greater in both of the with the nor- abnormal posture groups compared mal posture group. However, the relative angle between the medial border of the scapula and the upper thoracic spine was increased only in the subjects with an increase in thoracic kyphosis angle. These findings can be explained by the location of the kyphotic curve and the resulting effect on the shape of the thorax. In subjects with a thoracolumbar curve the scapula angled forward to approximately the same degree as the upper thorax and the relative angle between the upper thoracic spine and medial border of the scapula (ScSgR) was not significantly altered. When the curvature is in the thoracic region the ribs become prominent dorsally and the anteroposterior diameter of the thorax appears to be increased. The prominent dorsal ribs may prevent the scapula from tilting forward to the same degree as the upper thoracic spine resulting in the marked increase in the relative angle between the upper thoracic spine and scapular medial border (ScSgR) in these individuals. This could potentially result in a gradual elongation of structures having attachment to both the cervical spine and the scapula. For example, this abnormal and irritation at the site posture may lead to pain of insertion of the levator scapula as described by Cailliet.s The fibres of the upper trapezius and rhomboid muscles and the suprascapular nerve might be similarly affected. The humerus was in more extension in both the abnormal posture groups compared with the normal group, but there was no significant difference in the angle of the humerus relative to the scapula (HSgR) in this plane. This indicates that the humerus moved with the scapula or the humerus extended as the forward angulation of the scapula increased. Both abnormal postures resulted in an increase in upper thoracic slope. Extension of the arms may be a compensatory movement to help offset the anterior displacement of the upper thorax and maintain balance. The protraction angle of the scapula (ScTr) in the transverse plane was significantly greater in the subjects with an increase in curvature of the

8 34 thoracic spine. This finding can also be explained by the increased prominence of the ribs dorsally and the increased anteroposterior diameter of the thorax evident in subjects with a mid-thoracic curves The angulation of the scapula and/or the clavicle must increase to accommodate the greater anteroposterior thoracic diameter. The results are in agreement with the clinical literature describing increased scapular protraction with thoracic kyphosis.7,9,17 The relative angle between the scapular spine and clavicle (CITrR) was also greatest in subjects with thoracic kyphosis again suggesting an accommodation to an increased anteroposterior diameter of the thorax. The results of this study suggest that protracted scapulae or round shoulder posture does not necessarily accompany a forward head position as suggested in the literature. 7.9,17 Subjects in both the thoracolumbar and thoracic kyphosis posture groups had an increase in upper thoracic slope and a clinically apparent forward head position compared with the normal posture subjects. However, subjects with a thoracolumbar kyphosis did not have protracted scapulae. The position of the scapula in the transverse plane appears to be affected more by the anteroposterior depth of the thorax than by sagittal plane posture of the spine. It would appear, therefore, to be incorrect to equate a particular shoulder complex position with a forward head posture. The relative angle between the humerus and was less scapula in the transverse plane (HTrR) in the thoracic kyphosis group compared with the other two posture groups, indicating external rotation of the humerus relative to the scapula. This finding does not support the concept of increasing internal rotation of the humerus as kyphosis increases. The relative external rotation of the humerus may be compensatory to protraction of the scapula in order to maintain an upper extremity position more conducive to function. The angle of the scapula in the coronal plane was less in the two abnormal posture groups compared with the normal posture group, indicating a tendency towards scapular adduction. However, the differences in the mean angles were small and not statistically significant. Thus, there is little evidence from this study to indicate that scapular adduction (downward rotation of the glenoid) accompanies an increase in thoracic curvature as proposed by previous authors.7,9 Downward scapular rotation as a cause of elongation of levator scapula and irritation at its site of insertion proposed by Cailliet5 also appears doubtful based on these findings. The mean elevation angle of the clavicle was greater in both the abnormal posture groups. Subjects in both of these groups had an increase in upper thoracic slope. As this slope increases the sternum and medial end of the clavicle would tend to become depressed possibly resulting in the observed increase in the angle of elevation from medial to lateral in the abnormal posture groups. The humerus was less abducted in the thoracic kyphosis group compared with the other two groups. The abduction angle of the humerus to the scapula (HCoR) was also less in this group though the difference was not statistically significant. Thus, there was no evidence from this study to support the hypothesis that the humerus abducts relative to the downwardly rotated scapula in subjects with kyphotic posture as proposed by Kessler and Hertling.7 The trend would appear to be the reverse with adduction of the humerus relative to the scapula occurring in subjects with increasing thoracic kyphosis. The linear distance from Tl to the scapular centre was not significantly different in the three postural groups. There is no evidence from this study, therefore, to support the theory that the scapula moves laterally on the chest wall in subjects with kyphosis leading to elongation of the rhomboid and middle and lower trapezius muscies.4,10 The stretch-weakness of the middle and lower trapezius muscle in persons with kyphosis and forward shoulders as proposed by Kendall and McCreary O and, thus, the need for strengthening of the scapular retractors in persons with kyphosis should be questioned in light of these findings. Although mean values of Znor indicated that the scapula was depressed on the thorax in the thoracic kyphosis subjects and elevated in the thoracolumbar group compared with the normals this difference was not statistically significant. Conclusions The resting position of the shoulder complex was altered in the abnormal posture groups compared with those identified as having normal

9 35 thoracic posture. The shoulder complex position was dependent on where the curve was located; thoracic versus thoracolumbar region. The effect of posture on the resting position of the shoulder complex may be related more to the resulting changes in the shape of the thoracic cage rather than to the sagittal plane curvature alone. References 1 Nicholas JA, Wilson PD. Osteoporosis of the aged spine. Clin Orthop 1963; 26: Bowling RW, Rockar PA, Erhard R. Examination of the shoulder complex. Phys Ther 1986; 66: Braun BL, Amundson LR. Quantitative assessment of head and shoulder posture. Arch Phys Med Rehabil 1989; 70: Darnell MW. A proposed chronology of events for forward head posture. J Craniomandib Pract 1983; 1: Cailliet R. Soft tissue pain and disability. Philadelphia: F.A. Davis Company, Cailliet R. Neck and arm pain. Philadelphia: F.A. Davis Company, Kessler RM, Hertling D. Management of common musculoskeletal disorders: physical therapy principles and methods. Philadelphia: Harper and Row, 1983: Kendall HO, Kendall FP, Boynton DA. Posture and pain. Baltimore: Williams and Wilkins, Cailliet R. Shoulder pain. Philadelphia: F.A. Davis Company, Kendall FP, McCreary EK. Muscles: testing and function. Baltimore: Williams and Wilkins, Milne JS, Lauder IJ. Age effects in kyphosis and lordosis in adults. Ann Hum Biol 1: 1974; Fon GT, Pitt MJ, Thies AC. Thoracic kyphosis: range in normal subjects. Am J Roentgenol 1980; 134: Albanese AA, Edelson AH, Lorenze EJ, Woodhull ML, Wein EH. Problems of bone health in elderly: ten year study. N Y State J Med 1975; 75: Riggs BL, Wahner HW, Dunn WL, Mazess RB, Offord KP, Melton LJ, III. Differential changes in bone mineral density of the appendicular and axial skeleton with aging: relationship to spinal osteoporosis. J Clin Invest 1981; 67: Aloia JF, Vaswani A, Ellis K, Yuen K, Cohn SH. A model for involutional bone loss. J Lab Clin Med 1985; 106: Itoi E. Roentgenographic analysis of posture in spinal osteoporotics. Spine 1991; 16: Ayub E. Posture and the upper quarter. In: Donatelli R ed. Clinics in physical therapy: physical therapy of the shoulder. New York: Churchill Livingstone, 1987 :