Prevention of chronic entrapment of the ring finger flexor profundus muscle in ulnar shaft fractures in children--a case report.

Two children with a passive extension lag of the ring fi nger following forearm fracture have been treated in our clinic during the last 10 years, one with acute entrapment and the second with chronic entrapment. We have also treated 8 children with imminent entrapment. A description of the acute case was published in 1992 (Hendel and Aner 1992). The chronic case involved a previously healthy 16-year-old boy who presented with passive extension lag of the ring fi nger. The lag was more remarkable in the ring fi nger, but was also noticeable to a lesser extent in the little and middle fi ngers. The lag was more pronounced when the wrist was placed in extension and neutral position and less obvious when fl exed (Figure). 9 years previously, the boy had had a forearm fracture which was treated by closed reduction and plaster. A ring fi nger extension lag gradually developed a few weeks after plaster removal. Plain radiographs revealed healed fractures of the radius and ulna. Exploration of the origin of the fl exor muscles was performed, reaching the proximal ulna through a volar approach. The FDP of the ring fi nger was seen to be adherent to fi tissue around the ulna at the junction of the muscle belly and the tendon. The entrapped muscle was carefully released from the ulna. Full range of motion of the digits was achieved immediately. After surgery, the patient wore a volar splint for 1 month, with the wrist in neutral position and the fi ngers fully extended, and underwent physical therapy. At the last follow-up, 2 years after surgery, the patient had full active and passive range of motion of the digits. Following the chronic case of entrapment, we started to follow all our cases of forearm fracture during plaster treatment and after plaster removal, by performing a passive stretch test