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Journal of the Anatomical Society of India

A Study of Angle of Humeral Torsion

Author(s): Shah R K, Trivdei B D, Patel J P, Shah G V, Nirvan A B

Vol. 55, No. 2 (2006-07 - 2006-12)

Shah R K, Trivdei B D, Patel J P, Shah G V, Nirvan A B
Smt. N H L Municipal Medical College, Ahmedabad


A study of angle of the humeral torsion has been carried out on 500 normal adult human humeri collected from Gujarat population. The average angle of the humeral torsion is 67.57° with a range of variation from 38° to 98°. In present study the mean angle of torsion on the left side (67.31°) was only slightly less than that on the right side (67.85°). The difference is not statistically significant. Torsion is inversely proportional to the mid shaft circumference but has no correlation with the length of the bone. The observations are compared with the findings of other workers on different races, and discussed in light of literature.

Keyword: Humerus, Angle of torsion, Length, Mid shaft circumference.


Torsion is defined as a state of longitudinal twisting or spiraling of shaft of a long bone and can be measured as the difference between joint axis of proximal and distal ends of the bones. In man, the biologic necessity of humeral torsion has resulted from the development of upper extremities as prehensile appendages, functioning frontally to the trunk axis and thereby assisting in the maintenance of an upright posture. Associated with this evolved posture, torsion occurs between proximal and distal extremities of the humerus, with humeral head facing postero-medially in anatomical position. The arc of humeral torsion is described by the rotation of the humeral head from the posterior position to the normal postero-medial position.

Studies reveal that there are two components to humeral torsion as stated: (a) Primary torsion, which is determined by developmental patterns, characteristic of various species and is present in the embryo. (b) Secondary torsion, which results from the pull of muscular forces, functions etc. The internal rotators exert their force on the shaft distal to epiphysis and the external rotators within the proximal epiphysis, it is stated that these forces working in opposite directions are responsible for addition of secondary torsion. Various aspects of the humeral torsion have been studied by several workers in different parts of the world.

The present study has been undertaken to study the angle of torsion in 500 humeri and the variation on the two sides, and to determine its correlation, if any, with the length, side and thickness of the bone.

Materials and Methods:

For this study five hundred humeri belonging to skeletons of unknown age, sex, and stature were collected from various Medical Colleges of Gujarat.

Out of 500 humeri, 242 were of right side and 258 were of left side.The angle of humeral torsion was measured by a method described by Krahl & Evans (1945). The mechanical axis of the head was taken as the line joining the two points namely center of the articular surface of head where transverse diameter of articular surface is maximum and at the greater tuberosity approximately between the insertions of supraspinatus and of the infraspinatus muscles. A pin was stuck with plasticin along the line of these two points (Fig 1). For the distal end axis, a point was marked on the anterior surface of capitulum along the center of its vertical diameter. Similarly a second point was marked on the trochlea. A pin was stuck with plasticin along the line of these two points (Fig. 2). The angle formed by the crossing of these two reference lines was then measured with the Torsiometer (Fig. 3). This angle is called the torsion angle.

An osteometric board is used to measure the length of the humerus. The mid shaft circumference was taken with the help of the millimeter graph paper at the level of the apex of the deltoid V.


The mean angle of torsion was 67.57° ± 9.99°. On the right side it was 67.84° ± 10.49°, where as on the left side it was found to be 67.31 ± 9.50°. The angle on both the sides fluctuated greatly with maximum angle on right side was 98° and that on left side was 94°(Table 1). Mid shaft circumference measured at the apex of the deltoid V was found at 5.66 on right side and 5.61 cms on left side. The range found for both sides doesn’t differ much. On the right side the largest and lowest angles of torsion (98° and 39°) were found with bones having mid shaft circumference of 4.6 cms and 6.3 cms respectively. Similarly on left side the largest and lowest angles of torsion (94° and 38°) were found in bones with mid shaft circumference of 5.3 cms and 5.0 cms respectively. On comparing the mid shaft circumference with the angle of humeral torsion, the coefficient correlation was –0.5247 indicating a moderately negative relationship. As shown in Table 1 the mean humeral length is very near to each other on right and left sides. Comparing the length with the angle of humeral torsion didn’t find any correlation between them.

Fig. 1
Photo 1 showing a pin fixed along the reference line employed for the upper end of Humerus

Fig. 2
Photo 2 showing a pin fixed along the reference line employed for the lower end of the Humerus.

Fig. 3
Photo 3 showing the measurement of angle of Humeral Torsion

Table I: Showing data of torsion angle, length and mid shaft circumference on left and right side

  Torsion Angle Length (cms) Circumference of shaft
Rt. Lt. Rt. Lt. Rt. Lt.
Maximum 98° 94° 36.5 35.1 6.9 7.0
Minimum 39° 38 ° 21.5 24.9 4.4 4.5
Mean 67.84° 67.31° 30.5 30.28 5.66 5.61
S. D. 10.49° 9.50° 2.06 1.78 0.49 0.46


Torsion and rotation are two different phenomenons. The angle made by the crossing of the axes of the two opposite ends, when measured obtusely includes 90 degree rotation, which the entire upper limb undergoes during its development in the embryo. The true value of the angle of the humeral torsion is obtained by subtracting 90 degrees from the obtuse angle.

On comparison with the series of other workers there was variation in the average means among the results. It is observed that maximum value of mean was 107 degrees (Symeonides et al 1995) and minimum was 35 degrees (Mehta and Chaturvedi, 1971). It has been observed that the variations in means of angle of torsion and large number of bones go hand in hand.

Mehta and Chaturvedi (1971) examined 200 bones and the mean average calculated was at 68 degrees. The range of variation was from 35 degrees to 88 degrees. In our series it was found to be 67.57 degrees. The range of variation in present study was 38 degrees to 98 degrees. The average mean of present series was more towards that of Mehta and Chaturvedi (1971) even though the method used by both authors to determine the angle of humeral torsion was entirely different. It also very near to the mean of 69 degrees of Salado Indians (Matthew et al. 1893) Ayer and Upshons (1943) stated the mean angle in south Indians at 62 degrees, while Kate (1968) found the average angle at 55 degrees in central India. A comparison of torsion angle reported by different workers show that there is a considerable racial variation (Table 3).

Among all the investigators who have studied torsion in different races, highest average degree of torsion is found to occur in white races. It would be interesting to note that with lower degree of torsion the incidence of recurrent anterior dislocation may be less common in Indians but so far no clinical data is available to support this hypothesis.

Many workers (Debevoise et al 1971, Kronberg et al 1990, Syndmonides et al 1995) have found positive relationship between increased humeral torsion and recurrent anterior dislocation of shoulder (RADS), in which there was significant increase in the angle of humeral torsion in patients with RADS as compared to persons without any history of RADS or shoulder trauma. However, Randelli et al (1986) reported no difference in torsion between normal shoulders and those with RADS. Kronberg et al (1990) suggested that increased torsion of humeral head might predispose to anterior dislocation by putting the head in a position of risk in the abducted and external rotated position. Symeonides et al (1995) also indicated that less force is needed for the first dislocation in shoulders with reduced or absent retroversion. The success of rotational humeral osteotomy for RADS to decrease the angle of torsion helps to confirm this (Kronberg et al1990, Symeonides et al 1995, Weber 1969, Weber et al 1984).

Table 2: Showing large sample test to assess the significance of the difference in the means of right and left side.

Side Means in
of mean
RT Humeri 242      
Mean 67.84 0.53 0.89 Not
S.D. 10.49      
LT Humeri 258      
Mean 67.31      
S.D. 9.50      

Table 3: Comparison of torsion angle as measured by different workers in different races

Authors Series Torsion Angle (Mean)
Broca (1881) Whites 74 degree
Mathews et al. (1893) Salado-Indians 69 degree
Mathews et al. (1893) Indian Tribes 63 degree
Martin (1928) Australian 45.5 degree
Martin (1928) Paltacalo-Indian 48.5 degree
Martin (1928) Feugians 53.9 degree
Martin (1928) Peruvians 60.2 degree
Martin (1928) Swiss 74 degree
Chillida (1943) Urgentine aborigines 61 degree
Ayer & Upshon (1943) Indians (South) 62.1 degree
Krahl & Evans (1945) Whites 74.4 degree
Krahl & Evans (1945) American Blacks 72.6 degree
Kate (1969) Indians (Central) 55 degree
Mehta et al. (1971) Indians (Rajasthan) 68.5 degree
Kronberg et al (1988) Swedish 59 degree
Fuchs et al. (1991) Germans 62.8 degree
Robertson et al. (2000) Americans 71 degree
Present Study (02-05) Indians (Gujarat) 67.57 degree

In present study the mean angle of torsion on the left side was only slightly less than that on the right side. The difference is not statistically significant. This fact was confirmed by applying large sample test which did not found the difference significant. Similar results have been reported by Kate (1969) reasoning that out of total average adult torsion 87% is completed at birth and intrinsic factors are play a greater role.

Greater right side torsion have been documented by Krahl & Evans (1945), Debevoise et al (1971) and Mehta & Chaturvedi (1971) working on American whites and Indian population. On the other hand Krahl & Evans’ (1945) study on American negros shows greater angle on left side than on the right side. Broca (1881) who has done the most extensive study of humeral torsion in 600 humeri of various races also found in nearly whole series the torsion is greater in the left humerus than in the right. Similar results have also been reported by other European workers. These findings also point that there is also a hereditary racial trait as suggested by Briffault (1927).

Present study shows that the circumference of the shaft is inversely proportional to the angle of torsion (Fig. 4). Lambert (1892) and Rouffiac (1924) reported that the angle of torsion is inversely proportional to the thickness of the bone when the diameter is taken at the level of apex of the “deltoid V”. Krahl & Evans (1945) were not able to substantiate this finding in white races in his study on 135 humeri but he found that greater degree of torsion occurred in thinner bones in American negros. In study of Mehta and Chaturvedi (1971) the torsion angle was found to be directly proportional to the circumference of the shaft.

Present study on comparison of length with torsion could not found any correlation between the two. Lambert (1892) reported that short humeri have a greater torsion than the long one, a finding we could not confirm in our study. Krahl & Evans (1945) study on white and black races and Mehta & Chaturvedi’s (1971) study on Indian population are also in line with our results.


It is very difficult to give a constant angle of humeral torsion as range of distribution is very wide. There was no significant difference in mean values of angle of humeral torsion on right and left side bones. However, the question whether there is any difference of torsion on two sides in a particular person cannot be answered from present study. The circumference of the shaft is inversely proportional to the torsion angle whereas no correlation was found to exist between length of the bone and angle of torsion.

Fig. 4: Showing that the circumference of the humeral shaft is inversely proportional to the torsion angle. Each point on the graph represents the average circumference for all humeri having the same torsion angle.


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