Location of distal pronator quadratus repair in distal radius fractures: A cadaveric biomechanical study

Background: We aimed to biomechanically evaluate the distal pronator quadratus and compare two locations of distal transection on the strength of the subsequent repair.Methods: Eighteen fresh-frozen cadaveric specimens were dissected to the pronator quadratus muscle. Specimens were randomly allocated for transection of the pronator quadratus at the myotendinous junction (red group) or parallel to the myotendinous junction at the midsection of the distal tendinous zone (white group). For both groups, repair of the muscle was performed using two figure-of-8 sutures. The radius and ulna were positioned in 90 degrees of wrist extension. The proximal muscular pronator quadratus was fixed in a cryo-clamp. Load-to-failure testing of the repair was performed at 1 mm/s with maximum amount of force applied to the pronator quadratus recorded for each specimen.Findings: The pronator quadratus had a mean width, height, and area of 31.41 +/- 5.74 mm, 53.79 +/- 7.46 mm, and 1604.27 +/- 429.20 mm2 respectively. The pronator quadratus distal tendinous zone had a mean width, height, and area of 29.71 +/- 5.83 mm, 12.22 +/- 2.79 mm, 282.94 +/- 148.30 mm2 respectively. There was no significant difference between the two groups for pronator quadratus height, width, total area, or tendinous zone height, width, or total area. The average load to failure for the white group was significantly higher than that of the red group (29.46 +/- 4.24 N vs. 13.78 N +/- 6.66 N).Interpretation: Incision and repair of the pronator quadratus in the distal tendinous region is stronger than incision and repair at the red myotendinous junction of the distal PQ.