Quantification of Shear Stresses Within a Transtibial Prosthetic Socket.
BACKGROUND
There is a paucity of objectively recorded data delineating the pattern of weightbearing distribution within the prosthetic socket of patients with transtibial amputation. Our current knowledge is based primarily on information obtained from finite element analysis computer models.


METHODS
Four high-functioning transtibial amputees were fit with similar custom prosthetic sockets. Three load cells were incorporated into each socket at high stress contact areas predicted by computer modeling. Dynamic recording of prosthetic socket loading was accomplished during rising from a sitting position, stepping from a 2-leg stance to a 1-leg stance, and during the initiation of walking. By comparing the loads measured at each of the 3 critical locations, anterior/posterior shear, superior/inferior shear, and end weightbearing were recorded.


RESULTS
The same load pattern in all 4 subjects was found during each of the 3 functional activities. The load transmission at the distal end of the amputation residual limbs was negligible. Consistent forces were observed in both the anterior/posterior and superior/inferior planes. Correlation coefficients were used to compare the loads measured in each of the 4 subjects, which ranged from a low of .82 to a high of .98, where a value approaching 1.0 implies a linear relationship amongst subjects.


CONCLUSIONS
This experimental model appears to have accurately recorded loading within a transtibial prosthetic socket consistent with previously reported finite element analysis computer models.


CONCLUSIONS
This clinical model will allow objective measurement of weightbearing within the prosthetic socket of transtibial amputees and allow objective comparison of weightbearing distribution within the prosthetic sockets of patients who have undergone creation of different versions of a transtibial amputation residual limb and prosthetic socket designs.
Department of Orthopaedic Surgery, Loyola University Health System, Maywood, Illinois, USA.
Adam
A
Schiff
Biomechanics Laboratory, Hines Veterans Administration Medical Center, Hines, Illinois, USA.
Robery
R
Havey
Biomechanics Laboratory, Hines Veterans Administration Medical Center, Hines, Illinois, USA.
Gerard
G
Carandang
Private Practice, Santa Barbara, California, USA.
Amy
A
Wickman
Scheck & Siress Prosthetic Laboratory, Oak Park, Illinois, USA.
John
J
Angelico
Department of Orthopaedic Surgery, Loyola University Health System, Maywood, Illinois, USA Biomechanics Laboratory, Hines Veterans Administration Medical Center, Hines, Illinois, USA.
Avinash
A
Patwardhan
Department of Orthopaedic Surgery, Loyola University Health System, Maywood, Illinois, USA mpinzu1@lumc.edu.
Michael
M
Pinzur
amputation; prosthesis; weightbearing