Three-Year Clinical Outcomes after Minimally Invasive Sacroiliac Joint Arthrodesis Using Triangular Implants in Japan: A Pilot Study of Five Cases

INTRODUCTION: Sacroiliac joint (SIJ) arthrodesis using a minimally invasive technique, particularly the triangular implant system, is performed in patients with SIJ dysfunction in the United States and Europe. We report three-year clinical outcomes of the first minimally invasive SIJ arthrodesis procedures using the implants performed in Japan. METHODS: Five patients (one man and four women; age: 56.4±16.9 years) with SIJ pain who underwent SIJ arthrodesis using a triangular implant system in 2017 were included. In addition to operation time and blood loss, pain intensity (visual analog scale [VAS]) and functional impairment (Oswestry disability index [ODI]) were assessed preoperatively and at a 36-month follow-up. Implant loosening and osseous bridging across the joint were evaluated using computed tomography images, and patients' satisfaction with the surgery was also assessed at 12 and 36 months. RESULTS: The surgical time was 67.7±13.1 minutes, and blood loss was 7.4±6.9 mL. The mean VAS value improved significantly from 88.0±8.4 mm to 33.6±31.9 mm at 3 months and was maintained at 46.4±30.9 mm at 36 months (P<0.05). The mean ODI improved significantly from 76.4%±3.8% to 46.2%±21.9% at 6 months postoperatively (P<0.05) but had no significant improvements thereafter: 46.94±23.7% (12 months) and 66.4±8.6% (36 months). Three of five patients presented with at least one implant loosening on the sacrum side. No patient had osseous bridging across the joint. A total of 80% (4/5) of patients reported satisfaction with the surgery at 12 months and 60% (3/5) at 36 months. CONCLUSIONS: The mean VAS value and ODI significantly improved until 6 months after the surgery. However, the mean ODI was reaggravated at 36 months after the surgery. Osseous bridging across the joint was not observed in all patients. We should carefully keep an eye on further long-term results to evaluate the implant.