[Long-term effectiveness of Ni-Ti memory alloy tripod fixator in treatment of Kienböck disease].

Objective: To investigate the long-term effectiveness of Ni-Ti memory alloy tripod fixator in the treatment of Kienböck disease.

Methods: The clinical data of 22 patients with Kienböck disease who were treated with Ni-Ti memory alloy tripod fixator between January 2011 and September 2013 and followed up more than 10 years was retrospectively analyzed. There were 14 males and 8 females with an average age of 45 years (range, 20-64 years). The Lichtman staging was stage Ⅲb. According to AO/Association for the Study of Internal Fixation (AO/ASIF) classification, there were 6 cases of type B1, 2 cases of type B2, 10 cases of type B3, and 4 cases of type C2. The disease duration ranged from 18 to 50 months, with an average of 30.7 months. The operation time, intraoperative blood loss, and complications were recorded. Wrist height ratio and scapholunate angle were measured by wrist anteroposterior and lateral X-ray films before and after operation. The grip strength of bilateral hands was measured by Jamar dynamometer. The wrist pain was evaluated by visual analogue scale (VAS) score, and the wrist function was evaluated by Mayo score, and the radial deviation, ulnar deviation, dorsiflexion, and palmar flexion range of motion of wrist were measured.

Results: The operation time was 45-60 minutes, with an average of 52.21 minutes; the intraoperative blood loss was 50-60 mL, with an average of 58.63 mL. No nerve or blood vessel injury occurred during operation. All patients were followed up 10-13 years (mean, 11.3 years). X-ray films at 3 months after operation showed that the density of lunate bone was lower than that before operation. Satisfactory fusion of the scapho-trapezio-trapezoeid joint was achieved at 3-6 months after operation (mean, 4.5 months), and the wrist height ratio and the scapholunate angle after fusion significantly improved when compared with those before operation ( P<0.05). Wrist pain relieved, scaphoid rotation and dislocation improved, and no radiocarpal joint degeneration was found during follow-up, and no internal fixator loosening, breakage, or lunate bone necrosis occurred. At last follow-up, the wrist radial deviation, ulnar deviation, dorsiflexion, and palmar flexion range of motion, VAS score, and grip strength of the affected side significantly improved when compared with those before operation ( P<0.05); the grip strength of the affected side recovered to 99.00%±1.25% of the healthy side. Mayo score ranged from 72 to 93, with an average of 85; 14 cases were rated as excellent, 5 good, and 3 satisfactory, the excellent and good rate was 86.4%.

Conclusion: In the treatment of stage Ⅲb Kienböck's disease, the scapho-trapezio-trapezoeid joint usion using Ni-Ti memory alloy tripod fixator can effectively reduce pain, improve hand function, and prevent further deterioration, and achieve good long-term effectiveness.