Review Question - QID 211490

This patient sustained a both-bone forearm fracture that was fixed with a long, straight plate which did not account for the native radial bow. This is the most likely reason for his limited pronosupination.

Open reduction with internal fixation of both-bone forearm fractures has generally demonstrated a high rate of union and excellent functional results. However, restoration of the radial bow is a critical. A lack of radial bow will limit pronosupination. To avoid this problem, the surgeon could have used a shorter plate or a plate with an anatomic radial bow, which many modern forearm plating systems now account for. The assessment and calculation for radial bow is highlighted in Illustration A. Other factors which may contribute to limited pronosupination include heterotopic ossification and scarring, though the former is not seen on radiographs.

Matthews et al. evaluated the impact of radial bow on pronosupination in a cadaveric both-bone forearm fracture model. The authors found that with a 10-degree deviation from the anatomic radial contour, there was no loss of pronosupination. However when this was increased to a 20-degree angulation, there was a significant loss of forearm pronosupination. The authors underscored the importance of restoration of radial bow in fixation of both-bone forearm fractures.

Schemitsch and Richards evaluated the outcomes in 55 adult patients following both-bone forearm fracture fixation. They reported good-excellent outcomes in 84% of cases. The authors found that bone grafting did not affect union (54/55 achieved union), but noted that restoration of the radial bow affected functional outcome and grip strength. The authors stressed the importance of restoration of radial bow.

Figure A is an AP radiograph of the forearm following ORIF of a both-bone forearm fracture with a long straight plate which fails to restore the anatomic radial bow. Figure B is a lateral radiograph of the same patient demonstrating fracture fixation with a long straight plate. Illustration A demonstrates the method for determining radial bow. A line from the sigmoid notch to the bicipital tuberosity is drawn (Y). A perpendicular line is drawn from Y to the point on the radial with maximal bow (a) (This number is usually 7%). The point of this intersection to the bicipital tuberosity is marked (x). The location of maximal bow is x/y (This number is usually 60%).

Incorrect Answers:
Answer 1: The patient is non-tender and has returned to activities. He does not have any clinical or radiographic evidence of fracture nonunion.
Answer 2: The patient has full active range of motion of his digits and wrist, which would indicate that the PIN is functional.
Answer 3: The ECU can be interposed at the DRUJ, particularly in radial shaft fractures in which the DRUJ is unstable after fracture fixation. However, this patient does not have DRUJ instability. Furthermore, there is no evidence of DRUJ diastasis on X-Ray.
Answer 4: The radiographs are negative for any evidence of heterotopic ossification, though this is another potential source of limited motion following ORIF of both-bone forearm fractures.