Biomechanical analysis of pelvic holding pathways and strategies for use of the steinmann pin in pelvic fracture reduction

Pelvic fracture is the most serious bone trauma and has the highest mortality and disability rate. Surgical treatment of pelvic fracture is very challenging for surgeons. Minimally invasive close reduction of pelvic fracture is considered the most difficult operation due to the complex pelvic morphology and abundant soft tissue anatomy, both of which increase the difficulty of pelvic fracture reduction. The most challenging aspect of such surgery is how to hold the pelvic bone and effectively transmit the reduction force to the bone. Therefore, a safe and effective pelvic holding pathway for reduction is necessary for pelvic fracture operations. Existing research on the pelvic holding pathway addresses anatomical position and dimension. Few studies have focused on biomechanical properties or on surgical techniques related to these pathways. This paper studies the three holding pathways that are most commonly used in clinical practice. The most effective force direction for each holding pathway is identified through finite element modeling. Pathway 1 is suitable for internal rotation operation and open/close-book operation of the pelvis; Pathway 2 is suitable for translation of the fractured pelvis toward the sacrum and internal pelvic rotation operations; Pathway 3 is suitable for pulling and lifting of the fractured pelvis against gravity and open/close-book operation of the pelvis. In addition, we find through our simulation that the use of a combined holding strategy can reduce the reduction force during the reduction process. We compared the performances of the 2-pin combined holding strategy (2P-CH) and the 3-pin combined strategy (3P-CH). During translational reduction, 2P-CH and 3P-CH showed little difference in pelvic reduction force. However, in rotational reduction, 3P-CH shows advantages. It has less reduction force and the least combined muscle resistance. It can also maximize the displacement of the iliac crest under the same conditions. The results of this study can be applied to surgical planning and to the development of robot-assisted surgery systems in selecting holding pathways and operation strategies for fractured pelvis.