Motion Analysis after Minimally Invasive Sacroiliac Joint Fusion in Patients with Postpartum Sacroiliac Joint Dysfunction: an Observational Case-Control Study

Introduction: The Sacroiliac Joint (SIJ) can be an important and significant cause of low back pain. A dysfunctional SIJ is initially treated with conservative treatment options, although known to have limited effectiveness and durability. Therefore, surgical approaches such as minimally invasive sacroiliac joint fusion (MISJF) have emerged and outcomes appear to be promising in terms of pain reduction and improvement of self-reported mobility. To date, little is known about the effects of MISJF on balance and motion patterns reflective of daily life activities. Methods: A prospective, longitudinal study was conducted to analyze motion patterns in patients with postpartum SIJ dysfunction before and three months after MISJF, and compare these data with age-, BMI- and postpartum-matched controls. Motion was analyzed throughout the execution of three tasks; (1) normal gait, (2) alternated single leg stance (SLS), and (3) sit-to-stance (STS). Spatiotemporal parameters, center of pressure and mass, pelvic angles and other joint angels were measured using a twelvecamera, three-dimensional motion capture system and ground reaction force platforms. Results: Gait analysis revealed no improvement in any of the measured parameters when comparing pre- and postoperative. Patients had a shorter step and stride length and a slower walking speed compared to matched controls. During SLS, improvements in balance were observed after surgery in the patient group, reaching comparable values to the matched control group. Total execution time of an STS improved in patients following MISJF and was comparable to that of matched controls. Conclusion: This study suggests that motion patterns seem to improve after MISJF in patients with postpartum SIJ dysfunction. Most notable differences were an improved balance during SLS and a faster STS performance. Additional studies with longer follow-up and larger sample sizes should provide more detailed insights on motion analysis in patients with postpartum SIJ dysfunction following MISJF.