Lumbar Plexopathy and Exploration Following an Oblique Lumbar Interbody Fusion (OLIF) iFactor-Associated Complication: A Case Report.

Background: Oblique lumbar interbody fusion (OLIF) is a minimally invasive surgical technique used for lumbar spine stabilisation, known for reducing the morbidity associated with traditional posterior lumbar fusion techniques. iFactor, a synthetic bone graft composed of P-15 osteogenic cell-binding peptide and anorganic bone mineral (ABM), is often used in such procedures for its reported high fusion rates and minimal complications. iFactor reports to only form bone when grafted into bone tissue, and not soft tissue. This case report presents a rare but significant complication requiring reoperation due to extruded iFactor putty. Case Presentation: A 65-year-old female smoker with a history of failed conservative management for back and right radicular leg pain underwent an OLIF procedure at the L4/5 intervertebral level. Postoperatively, she was well for the first 2 weeks but suddenly developed left leg and lower back pain. Delayed diagnosis of a rare complication was detected only after postoperative CT scans were analysed 6 months after surgery. Initial imaging suggested exogenous bone growth affecting the lumbar plexus. Management and Outcome: Diagnostic nerve blocks revealed that L3 and L4 roots were affected. Exploratory surgery importantly revealed that de novo bone had not encased the nerve roots but revealed a chalky paste appearance consistent with extruded iFactor putty. Following the surgery, the patient's symptoms improved considerably, emphasising the importance of accurate diagnosis and multidisciplinary team (MDT) involvement. Conclusion: This is a rare complication following OLIF, allowing extruded artificial graft to encase part of the lumbar plexus. This case supports the manufacturer's assertion that iFactor does not lead to exogenous bone growth. The surgical exploration revealed a chalk-like paste that was irritating the nerve plexus and highlights that surgical debridement of this substance under the psoas muscle is possible. This case also highlights that exploration of extruded bone grafts can be considered for patients presenting similarly after spinal fusion surgeries involving bone grafts.