1. 2025;28;S145-S156Functional Spinal Unit Approach for Orthobiologic Injections for Low Back Pain
   Narrative Review
   Annu Navani, MD, Swarnima Vardhan, MD, Abhinav Aggarwal, MD, Riya Navani, ., Jose Fabio Lana, MD, and Sudhir A. Diwan, MD.

BACKGROUND: Low back pain (LBP) is a common and complex health issue with a multifactorial origin, involving structures such as the lumbar intervertebral discs (IVDs), facet joints, muscles, ligaments, and nerve roots. Typically, traditional pain management approaches target isolated pain generators. However, recent advancements, particularly regenerative injection techniques, have shifted the focus toward a more comprehensive treatment model that addresses the entire functional spinal unit (FSU), providing a disease-modifying approach.

OBJECTIVES: The purpose of this narrative review is to provide a scoping overview of the concept of the FSU and evaluate the potential role of orthobiologics, such as platelet-rich plasma (PRP) and mesenchymal stem cells (MSCs), in treating back pain associated with various spinal conditions.

STUDY DESIGN: Narrative literature review.

METHODS: Relevant peer-reviewed manuscripts were identified through a comprehensive search of electronic databases, such as PubMed, Embase, and Google Scholar. Studies focusing on the anatomy, biomechanics, and pathology of the FSU, as well as those concerning the application of PRP and MSCs in spinal disorders, were included.

RESULTS: The FSU, the smallest structural unit of the spine, consists of 2 vertebrae, an IVD, facet joints, and associated supporting ligaments. The FSU is crucial for absorbing shock, distributing mechanical loads, protecting the spinal cord and nerve roots, and maintaining spinal stability and mobility. Orthobiologic therapies, including PRP and MSCs, have shown promise in modulating disease processes and promoting tissue repair in spinal conditions. Emerging evidence supports the efficacy of these therapies in reducing pain and improving functional outcomes by targeting multiple components of the FSU. A thorough understanding of the biomechanical processes and the dynamic distribution of mechanical load across its various structures is essential to recognizing that chronic LBP often arises from multiple pain generators rather than a single source. Therefore, an integrated treatment approach that addresses these multiple pain generators collectively, considering the FSU and the entire spine, is critical for optimizing patient outcomes. 

LIMITATIONS: Rather than being systematic, this narrative review is focused on providing an overview of the effects of orthobiologics in the treatment of chronic LBP using an FSU approach. The heterogeneity of study designs, variability in treatment protocols, and limited long-term data pose challenges in establishing standardized guidelines for orthobiologic therapies in LBP management.

CONCLUSIONS: Orthobiologic treatments offer a promising disease-modifying approach by addressing the entire FSU rather than isolated pain generators. Future research should focus on optimizing multitarget injection strategies, thereby standardizing treatment protocols. 

KEY WORDS: Low back pain, orthobiologics, platelet-rich plasma, functional spinal unit, mesenchymal stem cells