- Discussion
- roof arc concept was originally described by Matta in CORR 1986, and was based on analysis of 204 acetabular fractures with avg 3.7 year follow up;
- helps determine the amount of intact acetabular dome;
- is a useful method for determining need for surgery, however, it is
less predictive for
two column injuries &
posterior wall frx;
- radiographs need to be taken w/ the patient out of traction;
- Measurement:
- these are made on AP,
obturator and iliac oblique views;
- vertical line is drawn to the geometric center of the acetabulum;
- another line is drawn thru point where frx line intersects acetabulum & again to geometric center of the acetabulum;
- angle drawn in this way represents medial, anterior, or posterior roof arc as seen on AP,
obturator oblique, or iliac views, respectively;
- medial roof arc:
-
AP view;
- verticle line is drawn from roof of acetabulum to geometric center of the femoral head;
- second line is drawn from fracture to the geometric center;
- angle subtended by these lines forms the medial roof arc;
- this measurement applies to transverse acetabular fractures and if less than 45 deg, frx is unstable and requires ORIF;
- anterior roof arc:
-
obturator oblique view
- this measurement applies to anterior column fractures and if the roof arc is less than 25 deg, then the frx is unstable and requires fixation;
- posterior roof arc:
-
iliac oblique view
- this measurement applies to posterior column fractures and if less than 70 deg, then the frx is unstable and requires fixation;
Fractures of the acetabulum. A retrospective analysis.
Matta, J. M., Anderson, L. M., Epstein, H. C., and Hendricks, P.:
Clin. Orthop.. 205:230-240, Sept., 1986.
Abstract
The Effects of Simulated Transverse, Anterior Column, and Posterior Column Fractures of the Acetabulum on the Stability of the Hip Joint*
MS Vrahas MD et al.
JBJS Vol 81-A. July 1999.
