Three-Dimensional Assessment of Bilateral Symmetry of the Radius and Ulna for Planning Corrective Surgeries

Purpose The contralateral unaffected side is often used as a reference in planning a corrective osteotomy of a malunited distal radius. Two-dimensional radiographs have proven unreliable in assessing bilateral symmetry, so we assessed 3-dimensional configurations to assess bilateral symmetry. Methods We investigated bilateral symmetry using 3-dimensional imaging techniques. A total of 20 healthy volunteers without previous wrist injury underwent a volumetric computed tomography of both forearms. The left radius and ulna were segmented to create virtual 3-dimensional models of these bones. We selected a distal part and a larger proximal part from these bones and matched them with a mirrored computed tomographic image of the contralateral side. This allowed us to calculate the relative displacements (Delta x, Delta y, Delta z) and rotations (Delta phi x, Delta phi y, Delta phi z) for aligning the left bone with the right bone segments. We investigated the relation between longitudinal length differences in radiuses and ulnas. Results Relative differences of the radiuses were (Delta x, Delta y, Delta z): -0.81 +/- 1.22 mm, -0.01 +/- 0.64 mm, and 2.63 +/- 2.03 mm; and (Delta phi x, Delta phi y, Delta phi z): 0.13 degrees +/- 1.00 degrees, -0.6 degrees 0 +/- 1.35 degrees, and 0.53 degrees +/- 5.00 degrees. The same parameters for the ulna were (Delta x, Delta y, Delta z): -0.22 +/- 0.82 mm, 0.52 +/- 0.99 mm, 2.08 +/- 2.33 mm; and (Delta phi x, Delta phi y, Delta phi z): -0.56 degrees +/- 0.96 degrees, -0.71 degrees +/- 1.51 degrees, and -2.61 degrees +/- 5.58 degrees. There is a strong relation between absolute length differences (Delta z) between the radiuses and ulnas of individuals. Conclusions We observed substantial length and rotational differences around the longitudinal bone axis in healthy individuals. Surgical planning using the unaffected side as a reference may not be as useful as previously assumed. However, including the length difference of the adjacent forearm bones can be useful in improving length correction in computer-assisted planning of radius or ulna osteotomies and in other reconstructive surgery procedures. Clinical relevance Bilateral symmetry is important in reconstructive surgery procedures where the contralateral unaffected side is often used as a reference for planning and evaluation. (J Hand Surg 2012;37A:982-988. (C) 2012 Published by Elsevier Inc. on behalf of the American Society for Surgery of the Hand.)