Are quadrilateral surface buttress plates comparable to traditional forms of transverse acetabular fracture fixation?

Abstract

Background: Several construct options exist for transverse acetabular fracture fixation. Accepted techniques use a combination of column plates and lag screws. Quadrilateral surface buttress plates have been introduced as potential fixation options, but as a result of their novelty, biomechanical data regarding their stabilizing effects are nonexistent. Therefore, we aimed to determine if this fixation method confers similar stability to traditional forms of fixation.

Questions/purposes: We biomechanically compared two acetabular fixation plates with quadrilateral surface buttressing with traditional forms of fixation using lag screws and column plates.

Methods: Thirty-five synthetic hemipelves with a transverse transtectal acetabular fracture were allocated to one of five groups: anterior column plate+posterior column lag screw, posterior column plate+anterior column lag screw, anterior and posterior column lag screws only, infrapectineal plate+anterior column plate, and suprapectineal plate alone. Specimens were loaded for 1500 cycles up to 2.5x body weight and stiffness was calculated. Thereafter, constructs were destructively loaded and failure loads were recorded.

Results: After 1500 cycles, final stiffness was not different with the numbers available between the infrapectineal (568±43 N/mm) and suprapectineal groups (602±87 N/mm, p=0.988). Both quadrilateral plates were significantly stiffer than the posterior column buttress plate with supplemental lag screw fixation group (311±99 N/mm, p<0.006). No difference in stiffness was identified with the numbers available between the quadrilateral surface plating groups and the lag screw group (423±219 N/mm, p>0.223). The infrapectineal group failed at the highest loads (5.4±0.6 kN) and this was significant relative to the suprapectineal (4.4±0.3 kN; p=0.023), lag screw (2.9±0.8 kN; p<0.001), and anterior buttress plate with posterior column lag screw (4.0±0.6 kN; p=0.001) groups.

Conclusions: Quadrilateral surface buttress plates spanning the posterior and anterior columns are biomechanically comparable and, in some cases, superior to traditional forms of fixation in this synthetic hemipelvis model.

Clinical relevance: Quadrilateral surface buttress plates may present a viable alternative for the treatment of transtectal transverse acetabular fractures. Clinical studies are required to fully define the use of this new form of fixation for such fractures when accessed through the anterior intrapelvic approach.

Fig. 1A–D

The various fixation methods are shown: (A) a 10-hole anterior column pelvic reconstruction buttress plate with a posterior column lag screw; (B) an eight-hole posterior column pelvic reconstruction buttress plate with a posterior column lag screw; (C) a 10-hole anterior column pelvic reconstruction buttress plate supplemented with an infrapectineal quadrilateral surface buttress plate; and (D) a suprapectineal posterior column/quadrilateral surface buttress plate.

Fig. 2A–E

Photographs demonstrate the biomechanical test model. (A) Anterior and (B) lateral views of the anatomic hip orientation are shown. (C) The force vector acts in a mediosuperior direction to load the acetabulum. (D) For testing, each hemipelvis was mounted horizontally while maintaining the correct joint and applied force orientation. (E) The synthetic tissue surrogate is shown in the test frame.

Fig. 3A–D

Photographs demonstrate the failure mechanism in the (A–B) cadaveric and (C–D) Sawbones^® validation study. The failure mechanism (arrows) of the cadaveric specimens and synthetic tissue surrogates was identical with lag screw fixation.

Fig. 4

Load to failure results show (a) significantly lower failure load relative to the infrapectineal (IP) group (p < 0.023) and (b) significantly lower failure load relative to the suprapectineal (SP) group (p < 0.001). ANOVA effect size = 0.715. LS = lag screw; PBAL = posterior column buttress plate + anterior column lag screw; ABPL = anterior column buttress plate + posterior column lag screw.

Fig. 5A–D

Representative failure mechanisms (arrows) are shown for (A) posterior and (B) anterior column plating with supplemental lag screw fixation, (C) infrapectineal, and (D) suprapectineal fixation. The failure mechanism of the lag screw constructs is depicted in Fig. 3.