Osteochondromas in the forearm (radius and ulna) can result in deformity of the elbow, the wrist, and forearm rotation. Shortening of the ulna may also occur. Unlike the relationship between the tibia and fibula in the lower legs, the radius and ulna move relative to each other. Therefore, osteochondromas on these bones can severely limit normal function.
Osteochondromas in the ulna are usually sessile (broad stalk), while those in the radius are usually pedunculated (narrow stalk). Osteochondromas in the ulna often lead to a delayed growth of the ulna relative to the radius. The radius will grow longer than the ulna, but the ulna will tether the radius resulting in ulnar deviation and wrist deformity. The discrepant rate of growth can also result in subluxation and then dislocation of the elbow.
Osteochondromas in the radius can be divided into two types: those that protrude towards the ulna and those that do not. Those that do protrude towards the ulna impede rotation of the forearm, those that do not protrude towards the ulna do not affect rotation. Osteochondromas may also develop in the space between the radius and ulna (the interosseous space); these are referred to as “kissing osteochondromas.”
Surgical treatment involves first removing osteochondromas that affect forearm rotation (e.g. “kissing osteochondromas”). Deformity correction and lengthening follows. If there are no osteochondromas that affect forearm rotation, deformity correction and lengthening is the first step.
In simple cases, where shortening of the ulna relative to the radius is the only deformity, lengthening of the ulna is performed. If this is not addressed, other deformities (e.g. wrist deformity, elbow subluxation) will occur. We will perform the lengthening with a specialized circular external fixator called the Taylor spatial frame (TSF). The TSF allows simultaneous fixation of the radius to the ulna. Without this fixation, lengthening of the ulna will transport the radius towards the wrist. An osteotomy of the ulna is performed near the elbow and the TSF will slowly distract the ulna allowing new bone to form in the gap.
In more complex cases, the surgical plan includes correction of the wrist deformity and/or elbow dislocation. Once again, the TSF external fixator is applied. An osteotomy of the ulna is performed near the elbow and an osteotomy of the radius is performed near the wrist. The TSF can then simultaneously lengthen the ulna and correct radial tilt; this corrects the wrist deformity. If the elbow is dislocated, then the treatment is staged. The first step is to lengthen the ulna with the radius fixed to the ulna with a pin. This will transport the radius towards the wrist, usually resulting in correction of the elbow dislocation. If the elbow does not correct spontaneously, then a second-stage surgery is required to open the elbow joint and reduce the radial head. When there is both a wrist deformity and an elbow dislocation, elbow correction is performed first with reduction of the radial head; then, in a second-stage surgery, the wire connecting the radius and ulna is removed and an osteotomy of the radius at the wrist is performed to correct the wrist deformity; lengthening of the ulna follows.