Alignment of trans-tibial prostheses based on roll-over shape principles.
The authors examined the roll-over shape alignment hypothesis, which states that prosthetic feet are aligned by matching their roll-over shapes with an "ideal" shape. The "ideal" shape was considered to be the roll-over shape of the able-bodied foot-ankle system. An alignment algorithm and computational alignment system were developed to set trans-tibial alignments based on this hypothesis. Three prosthetic feet with considerably different roll-over shapes were either aligned using the alignment system or not aligned (i.e. used previous foot's alignment), and then were aligned by a team of prosthetists. No significant differences were found between roll-over shapes aligned by the computational alignment system and those based on standard clinical techniques (p = 0.944). Significant differences were found between the "no alignment" shapes and the prosthetist alignment shapes (p = 0.006), and between the "no alignment" shapes and the computational alignment system shapes (p = 0.024). The results of the experiment support the hypothesis that the goal of alignment is to match the prosthetic foot's roll-over shape, as closely as possible, with an "ideal" shape. The hypothesis is also supported by its ability to explain the results of previous studies. Using an "ideal" roll-over shape or surface as a goal for prosthetic alignment could lead to a priori alignment, eliminating the need for alignment hardware in some cases. Being able to build the alignment into a prosthesis without special hardware could be beneficial in low-income countries and in the fabrication of lightweight prostheses for the elderly.
Department of Physical Medicine and Rehabilitation, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA.
A H
AH
Hansen
M R
MR
Meier
M
M
Sam
D S
DS
Childress
M L
ML
Edwards
D000328:Adult; D000368:Aged; D000465:Algorithms; D000671:Amputation, Surgical; D000704:Analysis of Variance; D001186:Artificial Limbs; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007866:Leg; D008297:Male; D008875:Middle Aged; D011336:Probability; D011474:Prosthesis Design; D017755:Prosthesis Fitting / Q000379:methods; D013314:Stress, Mechanical; D013977:Tibia / Q000601:surgery*; D016474:Weight-Bearing