Sex and Laterality Differences in Medullary Humerus Morphology

Abstract

Percutaneous osseointegrated (OI) prosthetic limb attachment holds promise for transhumeral amputees. Understanding humeral medullary morphology is necessary for informed design of upper extremity OI systems, and is beneficial to the field of megaprosthetic reconstruction of the distal humerus where diaphyseal fixation is desired. The purpose of this study was to quantify the sex and laterality differences in humerus morphology, specifically over the diaphysis. Three‐dimensional surface reconstructions of 58 pairs of cadaveric humeri (43 male, 15 female) were generated from CT data. Measures describing periosteal and medullary morphology were collected relative to an anatomic coordinate system. Sex and laterality differences in biomechanical length (BML) were observed (P ≤ 0.001 and 0.022, respectively). Head radius was larger in males than females (P ≤ 0.001). Retroversion was increased in right humeri relative to left (P ≤ 0.001). Canal orientation exhibited a conformational shift from anteversion to retroversion distally at approximately 65% BML. Right humeri exhibited larger medullary diameters than left in the 1st and 2nd principal directions (P ≤ 0.024). Males displayed larger diameter medullary canals proximally (P ≤ 0.029) and an increased rate of divergence of the endosteal cortex in the proximal diaphysis (P ≤ 0.009). Females exhibited higher canal aspect ratios at mid‐shaft (P ≤ 0.014) and lower mean cortical thickness (P ≤ 0.001). Human humeral diaphysis morphology exhibits sex and laterality differences, which are dependent on position along the diaphysis. Understanding humeral morphology is necessary to achieve adequate primary stability and bone apposition in design of endoprosthetic stems for percutaneous OI implants, and distal humerus replacement. Anat Rec, 302:1709–1717, 2019. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association for Anatomy

Cortical and medullary morphology of the tibia

“…Medullary diameter dictates the minimum endoprosthesis size in the absence of cortical bone removal necessitated for canal preparation for the implant. Average medullary diameter varies dramatically from 13.4 mm at 64% BML to 53.8 mm at 10% BML, indicating that the size range necessary for a generic conical or cylindrical transtibial OI endoprosthesis is much larger than that for the humerus (Drew et al, 2019).…”

“…An a priori power analysis was calculated in G*Power (v3.1, Heinrich Heine Universität Düsseldorf, Germany) based on a similar study of humeral morphology (Drew et al, 2019). A total of 14 comparisons were made to capture sex differences and intraspecimen variability.…”

“…Biomechanical length (BML) was defined as the distance between the average heights of the proximal (tibial plateau, origin) and distal (tibial plafond) articular surfaces. This represents the functional biomechanical distance between the proximal and distal joints of the bone similar to how it was defined in the humerus (Drew et al, 2019). The tibial shaft axis (TSA) was defined using the inertial axis of the medullary canal starting from one medial–lateral proximal plateau width down the shaft from the origin, terminating at 50% BML.…”

“…Most morphologic research on percutaneous OI system design has been conducted for transfemoral devices (Nebergall et al, 2012; Webster et al, 2017) and transhumeral (Drew, Tashjian, Henninger, & Bachus, 2019), ignoring the most frequent major extremity amputation: transtibial (Johannesson et al, 2009; Ziegler‐Graham, MacKenzie, Ephraim, Travison, & Brookmeyer, 2008). Current tibial devices were originally designed for use in other anatomic locations.…”

Virtual implantation technique to estimate endoprosthetic contact of percutaneous osseointegrated devices in the tibia

“…Each region presents its own challenges and may require unique approaches. Unlike the humerus where we see a consistent medullary flare as you move proximally [16], the tibia has a distal convergence, diaphyseal straight region, and proximal flaring [15]. The previous approaches that allow for a single, scaled endoprosthesis for any residual limb length are likely not the best for the changing nature of the tibia.…”