Several authors have made efforts to define the position of the axillary nerve within deltoid muscle and to calculate the so called safe area for this nerve but it still remains a matter of debate. The primary aim of the study was to investigate the acromio-axillary (AA) distance and its correlation with upper arm length. The secondary aim was to re-define the safe area for axillary nerve within deltoid muscle. Sixty shoulders of thirty adult human cadavers were dissected using standard methods. The distance from the anterior and posterior edge of acromion to the upper border of the course of the axillary nerve was measured and recorded as anterior and posterior AA distance respectively. Correlation analysis was done between the upper arm length and AA distance for each limb. The ratios between anterior and posterior AA distance and upper arm length were calculated and mentioned as anterior index and posterior index, respectively. The mean of anterior and posterior AA distance was 5.22 cm and 4.17 cm, respectively. The mean of upper arm length was 29.30 cm. The means of anterior index and posterior indices were 0.18 and 0.14, respectively. There was a significant correlation between upper arm length and both the anterior and posterior AA distance. The axillary nerve was found to lie at variable distance from the acromion. The minimum AA distance was found to be 3.50 cm. So this should be considered as the maximum permissible length of the deltoid split. Upper arm length has strong correlation with both anterior and posterior AA distances. The ideal safe area for the axillary nerve was found to be a quadrangular area above it and the size of which depends on the length of the upper arm.
Acromion ; Adult ; Arm ; Cadaver* ; Deltoid Muscle* ; Extremities ; Humans ; Shoulder

The location of the radial nerve (RN) is described with various bony landmarks, but such may be disturbed in the setting of fracture and dislocation of bone. Alternative soft tissue landmarks would be helpful to locate the nerve in such setting. To recognize certain anatomic landmarks to identify, locate and protect RN from any iatrogenic injury during surgical intervention such as open reduction and internal fixation. Forty arms belonging to 20 adult cadavers were used for this study. We measured the distance of RN from the point of confluence of triceps aponeurosis (TA), tip of the acromion and tip of the lateral epicondyle along the long axis of the humerus. These distances were correlated with the upper arm length (UAL). The average UAL was 32.64±0.64 cm. The distance of the RN from the point of confluence of TA (tricepso-radial distance, TRD), tip of acromion (acromion-radial distance) and tip of lateral epicondyle of humerus (condylo-radial distance, CRD) was 3.59±0.16 cm, 14.27±0.59 cm, and 17.14±1.29 cm respectively. No correlation was found with UAL. Statistically, TRD showed the least variability and CRD showed maximum variability. The minimum TRD was found to be 3.00 cm. So this should be considered as the maximum permissible length of the triceps split. The point of confluence of the TA appears to be the most stable and reliable anatomic landmark for localization of the RN during the posterior approach to the humerus.