Lunate bone excision and scaphocapitate arthrodesis in late stages of Kienböck’s disease: a long-term prospective study

Abstract Purpose This study aims to evaluate the outcomes of scaphocapitate arthrodesis with lunate excision in patients with stage IIIB and IIIC Kienböck’s disease. Method Between September 2013 and April 2024, 106 consecutive patients were screened, with 64 consenting to participate. Final analysis included 56 patients (32 stage IIIB and 24 stage IIIC) who underwent scaphocapitate arthrodesis with lunate excision, utilizing distal radius bone grafting stabilized by Herbert compression screws. Preoperative and postoperative assessments (6, 18, 36, and 84 months) included VAS score for pain, ROM, grip strength, MMWS, PRWE scores, and radiographic evaluations including RS angle, CHR, CUDR, and ulnar variance. Results The mean operative time was 75 ± 11 min, and the average follow-up was 86 ± 2.5 months. The union rate was 91% with a mean time to union of 10 ± 2 weeks. Preoperative mean VAS scores (63 ± 4 mm) significantly decreased to 25 ± 9 mm at 6 months and 12 ± 4 mm at 36 months (p = 0.001), with a slight increase to 22 ± 5 mm at 84 months. ROM improved from 46% ± 9% of the healthy side preoperatively to 59% ± 3.2% at 36 months (p = 0.001) but slightly decreased to 58% ± 3% at 84 months. Grip strength improved from 48% ± 8% preoperatively to 89% ± 6.4% at 36 months (p = 0.001) and remained stable at 88% ± 4% at 84 months. The mean MMWS increased from 46 ± 7 to 75 ± 5 (p = 0.001), while PRWE scores decreased from 68 ± 8 to 23 ± 6 (p = 0.001). The mean RS angle decreased from 59° ± 8° preoperatively to 50° ± 3° at 36 months (p = 0.001). There was no significant change in CHR (0.44 ± 0.04 to 0.46 ± 0.03, p = 0.251), while CUDR decreased from 31 ± 3 mm to 25 ± 2 mm (p = 0.021). Ulnar variance remained stable (p = 0.325). Degenerative changes were noted in 13 patients (23%) at the RS joint, with six showing Grade I, 5 Grade II, and 1 Grade III degeneration. Additionally, 5 patients (9%) exhibited changes at the STT joint, comprising three with Grade I and 2 with Grade II degeneration. Conclusion Scaphocapitate arthrodesis with lunate excision can improves pain, ROM, grip strength, and functional scores in patients with stage IIIB and IIIC Kienböck’s disease. Over time, improvements in VAS scores and functional metrics were notable, though there was a slight decline in pain relief and ROM at 84 months. These changes are critical to understanding the potential degenerative complications, particularly at the RS joint, where some patients developed osteoarthritis. Level of evidence Level II.