[Long-term outcome of partial alloplastic replacement of the scaphoid bone].

The operative treatment of scaphoid nonunion with a small, sclerotic, or avascular proximal fragment and with accompanying radioscaphoid arthrosis is difficult and often disappointing. Excision of the proximal fragment, styloidectomy, partial replacement of the scaphoid, and insertion of a silicone-rubber lunate prosthesis has been recommended in these cases. From 1980 to 1984, eleven patients (all male, average age 42 [25 to 59] years) with conditions described above were treated by partial replacement of the scaphoid. In one patient, the prosthesis dislocated dorsally and was removed five months later. In another patient, increasing pain at the wrist necessitated a wrist fusion five years after implant replacement arthroplasty. Nine patients remained for evaluation with an average follow-up of 14 years, ranging from 12 to 16 years. Clinical and radiographic studies were performed according to the score proposed by Martini (see p. 153 of this issue). The overall results were satisfactory. The outcome was good in one case, satisfactory in six cases and poor in two cases. The best results could be observed in "subjective estimation" and in "work and sports". The worst results were found in the "X-ray" and "motility" evaluation. In all patients, radiographic and clinical symptoms of silicone synovialitis appeared approximately two years after surgery. This developed adjacent to the implant and later spread throughout the wrist. Simultaneously, carpal collapse and secondary arthrosis of the wrist developed. Only two patients complained of moderate wrist pain at the time of examination. None of the patients desired further treatment. This study shows that in advanced scaphoid nonunion partial replacement of the proximal fragment of the scaphoid with a silicone implant provides long-lasting pain relief and satisfactory hand function. However, progressive carpal collapse (SNAC) and radiocarpal arthrosis developing within four to five years cannot be prevented. Furthermore, severe silicone synovialitis was detected in all patients. Therefore, the procedure was abandoned after 1984.