Biomechanical Comparison of Intrapelvic and Extrapelvic Fixation for Acetabular Fractures Involving the Quadrilateral Plate

Elderly patients represent the fastest growing and most difficult to treat population sustaining acetabular fractures. When treated surgically, isolated extrapelvic or combined intrapelvic-extrapelvic constructs may be used. No biomechanical or clinical study has compared the merits of these 2 techniques in cadaveric models. This research aims to biomechanically quantify the additional benefit of intrapelvic fixation to a standard extrapelvic fixation construct.Ten cadaveric pelves underwent standardized anterior column and quadrilateral plate fracture creation. One hemipelvis from each subject received isolated extrapelvic fixation, whereas the other received adjunctive intrapelvic fixation. Specimens were then subjected to a 50% of body weight (BW) nondestructive stiffness test followed by loading to failure. For the 50% BW test, displacement at 50% BW and stiffness were calculated. For the load to failure test, stiffness, elastic energy, and plastic energy were calculated. Yield point, force at clinical failure (defined at 2 mm of displacement), and maximum force were also identified. A Wilcoxon matched-pairs t test was used to compare fixation groups.The addition of an intrapelvic plate improved construct performance for all test parameters. A statistically significant difference (P < 0.05) was reached for yield force, maximum force, and plastic energy.These findings demonstrate that the addition of intrapelvic plating may offer distinct advantages in prevention of catastrophic construct failure in situations in which significant lateral to medial force is applied to the greater trochanter such as patient falling.