Geometric Morphometrics: Does the Appearance of the Septal Aperture Depend on the Shape of Ulnar Processes?

Abstract

Many theories have been suggested to explain the etiology of septal apertures (SA) of the humerus. The influence of genes, the size of ulnar processes, joint laxity, and bone robusticity, have been discussed; however, the problem has not yet been solved. The main aim of this study was to examine the influence of ulnar and humeri shape on septal aperture formation, using geometric morphometric analyses. Skeletal material from an early-mediaeval cemetery located in Western Poland was used. The material comprised two groups: (1) ulnae and humeri with septal apertures, (2) ulnae and humeri without septal apertures. From a CT image, three-dimensional reconstructions were obtained for all bones. Then, 25 landmarks were distributed on each proximal end of the ulnae and 30 landmarks on the distal ends of the humeri. Shape differences between ulnae in joints with and without SA were significant for the left and right sides of the body. The shapes of the left and right distal ends of humeri with SA differed significantly from those without SA. Similar results were obtained for the right side of the body. Ulnae from joints with SA were characterized by a more pronounced olecranon process, a smaller articulated coronoid process and a more tightly curved trochlear notch than ulnae from joints without SA. Humeri with SA included wider and deeper olecranon fossae and smaller and less curved articular surfaces. These results partly coincide with the results of other research indicating the influence of olecranon processes on lamina perforation. Anat Rec, 298:2030-2038, 2015. V C 2015 Key words: supratrochlear foramen; intercondylar foramen; nonmetrical features; humeroulnar joint; elbow jointThe septal aperture of the humerus (SA) (also called the intercondylar foramen or supratrochlear foramen) is a perforation in the bony lamina that separates the olecranon and coronoid fossae in the distal part of the bone (Mays, 2008;Paraskevas et al., 2012). The septal aperture was first described by Meckel (1825 after Meckel et al., 1970.

The mechanical hypothesis of septal aperture formation tested in an early medieval population from Ostrów Lednicki (Poland)

“…Contrastingly, the forearms from Ostr ow Lednicki showed a correlation between development of the olecranon process, which is the site of attachment of the triceps brachii, and SA formation. Additional geometric morphometric analyses of the ulnar processes in Ostr ow Lednicki confirmed our results by demonstrating that the olecranon process is more pronounced and the coronoid process less pronounced in joints with SA (Kubicka et al 2015). However, our small sample size limits the potential for interpretation of the results, mandating caution before unambiguous conclusions can be drawn.…”

“…The marked variation in the frequency of SA among different human populations has been claimed as evidence for its inherited aetiology Mays, 2008). The relationships between SA and bone robusticity, the size and shape of ulnar processes (Benfer & McKern, 1966;Benfer & Tappen, 1968;Silveira et al 2007;Kubicka et al 2015;Myszka, 2015;Ndou & Schepartz, 2016), osteoarthritis (Myszka & Trzci nski, 2015), and osteoporosis (Papaloucas et al 2011) have also been discussed. Some authors identify genes as factors in SA formation.…”

Septal Aperture of the Humerus: Etiology and Frequency Rates in Two European Populations

“…However, data collected from Mays () indicates that there is no evidence that humeri with a SA are less robust than those without. In the study completed by Kubicka et al (), it was determined that there was partial shape difference in ulnae between those with and without an aperture, thus supporting the mechanical theory. This was also concluded in Mays (); however, it is emphasized that these results should be taken with caution and need to be further supported with additional research.…”

Bilateral asymmetry of the humerus in Neandertals, Australian aborigines and medieval humans

“…Analyses based on cross‐sectional geometry can provide information about the influence of mechanical loading on skeletal robusticity; however, more sophisticated visualization of differences in the whole shape of the cross section would be helpful in interpreting the various functional roles played by a given area (e.g., Kubicka, Lubiatowski, Długosz, Romanowski, & Piontek, ; Kubicka, Myszka, & Piontek, ). According to Ruff et al (), a relationship exists between mechanical loading and bone morphology due to bone remodelling in response to biomechanical loading.…”