U. Culemann et al., Three-dimensional movement analysis after internal fixation of pelvic ringfractures - A computer simulation, UNFALLCHIRU, 103(11), 2000, pp. 965-971
Several studies exist describing the biomechanical behavior of several exte
rnal or internal fixation techniques of the posterior and anterior pelvic r
ing. Recently, the traditional models using isolated anatomical sections or
fixed pelvic ring specimens for evaluation of linear or two-dimensional da
ta have been replaced by three-dimensional measurement systems and simulati
ons of muscle forces. These studies have contributed important information
to the understanding of the biomechanics of the intact and injured pelvic r
ing, however, a consequent movement analysis is still missing.
In the present study, 3-D data acquired during several series of testing im
plants for stabilization of the posterior pelvic ring (sacrum: sacral bars,
sacral plates, transiliosacral lag screws; S1 joint: anterior plates, tran
siliosacral lag screws), using a complete pelvic ring model with single leg
stance and static abductor muscle simulation,were converted into a commerc
ially available 3-D animation package. By use of simple graphical represent
ation of anatomical elements of the pos terior pelvic ring, reproducible an
d reliable movement patterns for different types of stabilization could be
identified,which demonstrated potential "weakness" of the fixation before f
ailure occurred. These movements were analyzed by "replay functions" and we
re comparable to observations during the original experiment. The following
movements were observed. Sacral fracture, transforaminal: (1) rotation of
the transiliosacral lag screws around its axis, even with a second screw in
to S1; (2) Sacral bars: shearing with compression of the cranial-posterior
fracture zone; (3) Sacral plates: minimal translation in the proximal fract
ure zone and distraction in the distal fracture line, effectively compensat
ed by an additional plate at the S3 level.
S1 joint disruption: (1) anterior plating (two plates), minimal translation
in the plane of the S1 joint; (2) transiliosacral lag screws, rotational m
ovement around the axis of the screws with only minimal movement at the S1
level. The provided information confirmed the observations and allowed a mo
re detailed and comfortable examination of movement patterns. A better unde
rstanding of potential "failure zones" might be useful to optimize the dime
nsions, design, and the positioning of implants for the pelvic girdle. For
further studies, more complex computer models including finite element tech
nology might be useful to add accessory information and could result in a d
ecreased need of living specimen testing.