The use of right and left pectoralis minor muscle measurements obtained from thoracic CT images in the determination of hand dominance

This study aims to examine the place of the concept of handedness (hand preference) in the practice of forensic medicine and forensic sciences, and to investigate the role of upper extremity muscle measurements — specifically, the morphometry of the pectoralis minor muscle — in determining hand preference. Handedness is considered an important parameter for clarifying the origin of suspicious death cases such as homicide, suicide, or accidents, and for identifying the hand preference of the perpetrator or victim in incidents involving defensive wounds, firearm injuries, and injuries caused by sharp or penetrating objects. Moreover, determining hand preference has practical value in areas such as forensic document examination, disability assessment, and offender profiling. Although many hypotheses have been proposed regarding the biological basis of handedness, no single decisive factor has yet been identified to fully explain this phenomenon. Studies indicate that, in addition to genetic predisposition, factors such as intrauterine stress, hormonal exposure, neurodevelopmental processes, and sociocultural influences also play a role. In the literature, handedness has generally been evaluated through anthropological bone measurements, radiological imaging methods (fMRI, PET), motor performance tests (such as grip strength and finger tapping tests), and questionnaire-based scales (Edinburgh Handedness Inventory, Annett Scale). However, data on handedness derived from muscle volume and area measurements remain limited. The pectoralis minor muscle, in particular, plays a functional role in shoulder girdle movements and scapular positioning, and due to its anatomical location, it is easily accessible. Nevertheless, there are no radiological studies investigating the correlation between its morphometry and hand preference. In this thesis, the possible relationship between hand dominance and the length, width, area, and volume measurements of the right and left pectoralis minor muscles was examined. Of the 140 cases included in the study, 42.14% (n=59) were female and 57.86% (n=81) were male. Fifty cases (35.7%) consisted of patients diagnosed with cancer, while the remaining 90 cases (64.3%) included patients with conditions such as COPD, asthma, interstitial lung diseases, and trauma. Among the 140 participants, 130 (92.9%) were found to be right-hand dominant, and 10 (7.1%) were left-hand dominant. Correlation analyses revealed a high level of positive and significant correlations between all measurements of the right and left pectoralis minor muscles. This finding indicates that bilateral muscle development is structurally symmetrical, that the pectoralis minor muscle exhibits bilateral morphometric integrity, and that there is structural balance between the measurements. The overall mean age of the cases, which were within the 18–64 age range, was found to be 47.61 years. The mean right pectoralis minor muscle volume was approximately 16,598 mm³, while the mean left muscle volume was approximately 17,036 mm³. Examination of the relationship between age and muscle volume revealed a weak negative correlation, suggesting that muscle volume decreases with age; however, this was not statistically significant. Analyses according to sex showed that male individuals had statistically significantly higher values than female individuals in almost all measurements of both the right and left pectoralis minor muscles. Comparisons according to disease group (cancer vs. others) revealed no statistically significant differences in pectoralis minor muscle measurements. In evaluations regarding dominant hand use, a significant difference was observed only in the variable of left pectoralis minor muscle width (p=0.048), which was found to be higher in individuals who were left-hand dominant. In conclusion, investigating the contribution of pectoralis minor muscle morphometry to the determination of handedness may provide a new supportive parameter in forensic medical practice. The findings of this study are expected to contribute to the forensic science literature and to serve as a basis for future similar research.