Biomechanics of the Sacroiliac Joint: Surgical Treatments

Fixation is one of the most common surgical techniques for the treatment of chronic pain originating from the sacroiliac joint (SIJ). Many studies have investigated the clinical outcomes and biomechanics of various SIJ surgical procedures. However, the biomechanical literature points to several issues that need to be further explored, especially for the devices used in minimally invasive surgery of the SIJ. This study (part II) aims to assess biomechanical literature to understand the existing information as it relates to efficacies of the surgical techniques and the gaps in the knowledge base. Part I reviewed basic anatomy and mechanics of the SIJ joint, including difference between males and females, and causes of pain emanating from these joints. A thorough literature review was performed pertaining to studies related to SIJ fixation techniques and the biomechanical outcomes of the surgical procedures. Fifty-five studies matched the search criteria and were considered for the review. These articles predominantly pertained to the biomechanical outcomes of the minimally invasive surgery with different instrumentation systems and surgical settings. The SIJ is one of the most overlooked sources of lower back pain. The joint is responsible for the pain in 15% to 30% of people suffering from lower back pain. Various studies have investigated the clinical outcomes of different surgical procedures intended to improve the pain and quality of life following surgery. The data show that these techniques are indeed effective. However, clinical studies have raised several issues, like optimal number and positioning of implants, unilateral versus bilateral placements, adjacent segment disease, implant designs, and optimal location of implants with respect to variations in bone density across the SIJ. Biomechanical studies using in vitro and in silico techniques have addressed some of these issues. Studies also point out the need for additional investigations for a better understanding of the underlying mechanics for the improved long-term surgical outcomes. Further long-term clinical follow-ups are essential as well. This review presents pertinent findings.