Three-dimensional digital geometry design of soft tissue implants for patients with Poland’s syndrome using Magics and Freeform® Modeling™

Abstract

Poland’s syndrome is a unilateral congenital defect displaying deformities of mostly the soft tissues and the skeleton. The syndrome commonly affects the right side of the thorax and is more often found in males. Many Poland’s syndrome patients display the absence of the pectoralis major muscle, although other muscles such as the pectoralis minor may also be affected. Poland’s syndrome is also associated with hand deformities. Poland's syndrome patients usually seek medical intervention to improve their aesthetic appearance. Most of the interventions are traumatic, invasive, surgical procedures. Less invasive and traumatic approaches are constantly being developed. Therefore, the main aim of this study was to design three-dimensional digital geometries of soft tissues for two Poland’s syndrome patients that can be used for the production of soft tissue implants in the manufacturing process. A female (Case Study 1) and a male (Case Study 2) Poland’s syndrome patient were included as two case studies. CT scanned digital imaging data sets were acquired of the two Poland’s syndrome patients and were processed in Mimics® software to create 3D digital geometries in STL file format. A number of manipulations and pixel-by-pixel editing steps were applied to isolate the regions of interest which were then imported into the programs Magics and Freeform® Modeling™. The program Freeform® Modeling™ was used to describe the extent of the aesthetic presentation of the deformity by determining the difference between the healthy and affected sides of the thorax in both patients. The angles between the vertical and oblique planes for both sides of the thorax were measured and the difference between these angles calculated. For the female the difference was 6.5º, while for the male it was 14º. The design phase followed two design routes to design soft tissue 3D digital geometries of the pectoralis muscle for each patient using the programs Magics and Freeform® Modeling™. The one route involved using a mirror image of the whole thorax (Technique A), while the other route involved firstly the isolation of the pectoralis muscle from the healthy side of the thorax and thereafter producing a mirror image (Technique B). Four different soft tissue 3D digital geometries of the pectoralis muscle resulted for each patient from these design routes. Three different analyses were performed to compare the outcomes of the different design routes and software programs. A deviation analysis was performed using Geomagic® Control™ to calculate the deviation between the design route outcomes and constructed digital test models. Most of the deviation test points for all techniques fell within the nominated tolerance region of >-5 and <+5 mm (more than 70% for the female more than 80% for the male). An implant mass property analysis using Freeform® Modeling™ revealed that the 3D digital geometries produced using Freeform® Modeling™ Technique A presented with surface areas and volumes closest to original healthy pectoralis muscle in the female, while for the male it was Freeform® Modeling™ Technique B. A body conformation analysis was performed to ascertain to what extent the different techniques used to produce the 3D digital geometries had the potential to reconstruct the soft tissue deformities, thus the resultant 3D digital geometries were compared with an original body conformation, as well as with an ideal body conformation. For both patients the four 3D digital geometries were relatively close to the ideal body conformation dimensions. In an attempt to compare the performance of Magics and Freeform® Modeling™, they were assessed, where possible, in terms of software functionality, hardware possibilities, and geometry development time and software/hardware costs. It could be concluded that, in this study, Freeform® Modeling™ appeared to be the better suited software program for the designing of 3D digital geometries of soft tissue implants.