The new 3.5 mm quadrilateral surface plates are intended for use in acetabular fracture patterns amenable to an anterior surgical approach, which have an important component of quadrilateral surface comminution. They are typically used in conjunction with pelvic reconstruction plates. There are three plate sizes (short, standard, and long) available which are made of 316L stainless steel and are part of the 3.5 mm low-profile pelvic system. The standard and long plate versions have a connecting screw slot where triangulated buttress screws can be inserted for additional support (Fig 1). These interconnecting screws should be 2 mm longer than the actual length measured to ensure that the screw engages the serrated teeth of the plate at the quadrilateral surface. All plates are prebent to fit most quadrilateral surface anatomy, but minor contouring may still be necessary. Reconstruction plates are often placed on the pelvic brim or the endopelvic surface over the 3.5 mm quadrilateral surface plates to aid final plate fit and provide additional buttress function (Fig 2, Fig 3).

Case provided by Keith Mayo, Tacoma, USA: An elderly woman with steroid-dependent chronic obstructive pulmonary disease on home oxygen sustained an anterior column plus posterior hemitransverse acetabular fracture in a ground-level fall from her electric scooter.

Fig 1ad AP pelvis, Judet oblique, and coronal CT scan views of associated anterior column plus posterior hemitransverse acetabular fracture. This pattern is problematic for multiple reasons, including mild impaction of virtually the entire weight-bearing surface with additional separate impaction of the displaced anterior column, quadrilateral surface comminution, and severe osteoporosis.

Fig 2ab Intraoperative AP hip and iliac oblique image intensifier images of a portion of the reduction sequence utilizing distal/lateral traction through a Schanz screw, ball spike (picador) with disc and asymmetrical reduction clamp with disc. The remaining area of incompletely reduced articular surface was a free, thin osteochondral fragment retrieved through the anterior column fracture. It was reoriented and trapped between the lateral articular surface, displaced anterior column, and femoral head. Despite multiple attempts this position could not be further improved. Cancellous autologous bone graft was used to buttress this area through a small internal iliac fossa cortical window.

Fig 3ab AP hip and iliac oblique image intensifier views show initial quadrilateral surface plate placement with the aid of an asymmetrical clamp and subsequent introduction of overlying pelvic brim reconstruction plate. In this case a locking pelvic brim plate was chosen because of the severe osteoporosis.

Fig 4ac AP pelvis and Judet oblique x-rays 9 months postoperatively. The patient started full weight bearing at approximately 10 weeks postoperatively. The fractures healed without secondary displacement. The patient returned to preinjury (relatively limited) activity level with no significant residual pain complaints.

Note: In this case the quadrilateral surface plate has been useful both as an interim reduction aid and to augment prior stabilization constructs. In effect, it provides a "prosthetic" cortex for the quadrilateral surface as well as enhancing posterior column stability in a way not possible with typical anterior to posterior column lag or position screws alone.