[Arthrodesis of the carpometacarpal joint of the thumb using a cannulated screw].

Purpose of the Study: To present the results of surgical treatment of carpometacarpal joint arthritis of the thumb, using cannulated screw fixation which is stable and, after bony union, allows the patient to do also harder manual work
Material: In the years 2000 to 2005, this method was used for 20 operations in 18 patients (16 women and two men); one man and one woman had bilateral surgery. The right hand was operated on in seven cases and the left one in 13 cases. The average age of the patients was 61 years.
Methods: The procedure was performed from the dorsoradial approach, access to the joint was gained between the extensor pollicis brevis and abductor pollicis longus tendons, and care was taken to protect the superficial branch of the radial nerve. The articular surface of the trapezium bone and the first metacarpal base including osteophytes were resected and arthrodesis was carried out by means of a 4.5 mm cannulated screw. The final position of the thumb axis was at 40 degrees to 45 degrees palmar abduction, 20 degrees to 25 degrees extension and 10 degrees to 15 degrees pronation. A plaster hand splint was applied for 6 to 8 weeks post- operatively. The patients were capable of full use of the hand at 3 months after surgery.
Results: Evaluation included a pain scale of 1 to 5 grades, range of motion, reduction of muscle strength and fine motor function. All operative wounds healed by first intention, no infection or neurological complications were recorded. Primary union was achieved in 18 cases, two developed pseudoarthrosis. The patients reported improvement on the pain scale by 2 grades on average. However, in thumb opposition tasks, the range between the tip of the thumb and the fifth metacarpophalangeal joint decreased on average by 20 mm. Fourteen patients reported deterioration of fine motor function. All patients were satisfied with improved muscle strength enabling them to do more demanding physical work.
Discussion: The results of carpometacarpal joint arthrodesis by means of a cannulated screw are comparable with those of arthrodesis using other implants. The final thumb position is discussed as well as the use of suitable fixation material in order to prevent pseudoarthrosis. Issues such as the use of interpositioned tissue, shortening of the radial column and the resultant limited muscle strength in resection arthroplasty, and the choice of a most suitable implant and possibility of its failure in alloplasty are also discussed.
Conclusions: Arthrodesis with cannulated screw fixation is best for treatment of the carpometacarpal joint of the thumb with stage III rhizarthritis (Eaton classification). It results in an axis-stable thumb that is pain free and capable of physical activity and firm grip.