Distal Radius Osteotomy

Overview

An osteotomy is a surgical procedure to realign a bone in order to change the biomechanics of a joint, especially to change the force transmission through a joint.

These procedures must be performed accurately, not only to create the desired geometries but also to provide biological environments for rapid and effective healing.

More specifically, the distal radius osteotomy (DRO) is a corrective surgical procedure in which the distal radius is cut near the original fracture site and realigned to restore normal function.

Fractures of the Distal Radius

Fractures of the distal radius constitute about 15% of all fratures seen in the emergency room. The distal bone fragment may fail to realign to its proper anatomical position during healing, which can affect the alignment, kinematics, and load transfer across the wrist. Such malunions often lead to reduced strength, reduced range of motion, and pain.

The Traditional Technique

1. AP and lateral X-ray films of the deformed wrist are taken.
2. Osteotomy lines are drawn on the X-ray films to determine the size and shape of the bone graft needed to correct the wrist to accepted radiographic indices.
3. Intraoperatively, after the bone has been cut, fluoroscopic images are taken to determine the alignment of the distal bone fragment. This process is repeated until the desired orientation and position is obtained.
4. The defect gap is filled with a bone graft or bone substitute.
5. A fixation plate is contoured to the shape of the distal and proximal fragments, secured with bone screws.

This technique has three major limitations: poor planning of rotations in three dimensions; difficulty in achieving the desired lengthening, due to soft-tissue contracture; and a high dosage of fluoroscopic radiation to the patient and OR staff during the surgery.

Computer-Assisted Planning

Creating a preoperative plan involved five steps:

1. Initial Alignment Using the mirror image of the healthy arm, the entire ulna and the proximal radius of the affected wrist were aligned with the template.
   
2. Virtual Osteotomy A cutting plane was chosen by the surgeon and the isosurface model was cut into two models.
   
3. Aligning the Distal Radii The distal radial fragment of the deformed radius was aligned with the healthy distal radius.
   
4. Positioning the Fixation Plate Once the surgeon was satisfied with the new alignment of the deformed distal radius, the model of the fixation plate was placed on the models such that in vivo it would hold the bone fragments in place. In placing the fixation plate on the bones, it was important to verify that it lay flat on the bones and that none of the screw holes for the plate would protrude into any joints.
   
5. Saving the Plan The location of the two distal and proximal drill holes for the plate were saved. The locations of the distal holes before the cutting of the bone were determined by applying the inverse transformation of the distal fragment to the drill locations.

Computer Assisted Intraoperative Guidance

Intraoperatively, pilot holes are drilled into the bone and the bone is shaved to fit the plate.

When the through holes in the plate align with the pilot holes in the bone, the correct alignment has been achieved and the plate is in the correct position for fixation. The defect is subsequently filled with bone graft or bone substitute.

This is a radical departure from the traditional technique. Fixation-based surgery requires computer assistance in both planning and guidance, which requires additional preoperative time for the planning process. However, the operative time is no greater than that needed for the traditional technique, there is almost no use of intraoperative X-ray fluoroscopy, and exceptionally large defects can be corrected.

References

Further information on our DRO work can be found using the links below:

1. H. Croitoru, R. E. Ellis, C. F. Small, R. Prihar, and D. R. Pichora. Fixation-based surgery: A new technique for distal radius osteotomy. Journal of Computer Aided Surgery, 6:160-169, 2001.
2. H. Croitoru, R. E. Ellis, C. F. Small, and D. R. Pichora. Fixation-based surgery: A new technique for distal radius osteotomy. In Medical Image Computing and Computer-Assisted Intervention - MICCAI 2000, pages 1126-1135. Springer Lecture Notes in Computer Science #1935, 2000.