Chiropractic Spinal Manipulation and Ligament Safety: Evaluating Force Thresholds and Clinical Risk

Written by: James Demetrious, DC, DABCO

Chiropractic spinal manipulation (CSM) has long been used for the treatment of musculoskeletal complaints, particularly those affecting the spine. Despite its demonstrated clinical utility and popularity among patients, concerns have persisted regarding the potential risk of ligament injury or vertebral artery compromise during manipulation, especially in the cervical spine.

A growing body of biomechanical and clinical literature, however, supports the safety of CSM when performed by trained chiropractic doctors. This article examines the relationship between manipulative forces and established ligament failure thresholds, drawing on recent scientific literature to evaluate the biomechanical plausibility of tissue damage during CSM.

Forces Involved in Spinal Manipulation

Spinal manipulation typically involves a high-velocity, low-amplitude (HVLA) thrust applied to specific spinal segments. The magnitude and duration of these thrusts have been studied extensively using both instrumented tables and direct cadaveric measurement.

Downie et al. (2023) conducted a scoping review of force-time metrics in spinal manipulation and found that cervical manipulations generally involve forces in the range of 100–150 newtons (N), while lumbar thrusts may range up to 400 N. The duration of these forces is extremely brief, usually less than 150 milliseconds. These findings are consistent with earlier data from Herzog et al. (1993), who reported similar force magnitudes and characterized the rapid loading profile of spinal manipulative therapy.

Pickar (2002) noted that these mechanical inputs are capable of eliciting neurophysiological responses in the central nervous system, but are unlikely to cause structural damage when applied within therapeutic ranges. This is largely due to the anatomical resilience of spinal tissues and the inherently controlled delivery of force during chiropractic manipulation.

Ligament Failure Thresholds and Biomechanical Safety

The question of whether such manipulative forces can exceed the failure threshold of spinal ligaments has been addressed through cadaveric testing. Ligamentous tissues in the cervical and lumbar regions have been shown to withstand considerably higher tensile loads than those typically produced during manipulation.

  • Alar ligament: Failure thresholds are estimated around 200 N. Average cervical manipulative forces fall well below this level (~100–150 N), suggesting a low risk of rupture.

  • Transverse ligament: This crucial stabilizer of the atlantoaxial joint typically fails at 350–450 N. CSM does not approach this range.

  • Lumbar supraspinous ligament: Tensile strength ranges between 300–500 N. Even with lumbar thrusts peaking near 400 N, failure remains unlikely.

  • Facet joint capsular ligaments: Estimated to fail around 200–250 N, though strains during CSM are often within or below this range, producing only transient deformation.

  • Ligamentum flavum: Despite being thin, it possesses considerable elasticity and typically fails beyond 200 N. Manipulation often bypasses this structure due to its posterior position.

These mechanical data, drawn from multiple cadaveric sources and clinical studies, confirm that spinal manipulation occurs within a safety buffer well below ligamentous failure thresholds (Herzog et al., 1993; Downie et al., 2023).

Vertebral Artery Strain and Safety

Concern about vertebral artery dissection (VAD) following cervical manipulation has drawn increased scrutiny over the past two decades. However, contemporary studies have offered clarity regarding the mechanical loading of these vessels.

Fagundes and Herzog (2024) measured vertebral artery strain during passive and manipulative cervical movements. They found that CSM induced strain levels significantly below the known threshold for arterial failure, with passive end-range movements generating greater strain than the thrust itself. Similarly, Piper et al. (2014) combined motion capture with cadaveric vascular strain analysis and reported no significant elongation or deformation of the vertebral artery during typical manipulative procedures.

Gorrell et al. (2022) extended this analysis using kinematic modeling and again confirmed that head and neck movements during manipulation did not stretch the vertebral artery beyond physiological norms. Their findings further erode the biomechanical plausibility of manipulation-induced dissection in healthy individuals.

Epidemiologic Context and Risk Assessment

Large-scale epidemiological studies have also failed to establish a causal link between CSM and VAD. Cassidy et al. (2008), in a population-based case-control study, found that patients who experienced vertebrobasilar stroke were just as likely to have visited a primary care provider as a chiropractor in the days preceding the event. Their results suggested that early symptoms of dissection, such as neck pain and headache, likely prompted healthcare visits, rather than manipulation causing the dissection.

A recent systematic review by Church et al. (2022) reaffirmed these findings, concluding that no direct evidence supports a causal association between spinal manipulation and cervical artery dissection. Instead, the temporal association often cited in case reports appears to reflect coincidental timing rather than biomechanical harm.

Conclusion

When evaluated against established failure thresholds for ligaments and arteries, the forces used in chiropractic spinal manipulation are well within safe limits. Recent biomechanical research confirms that neither cervical nor lumbar manipulations deliver sufficient force to rupture spinal ligaments or stretch the vertebral artery beyond physiological capacity. Furthermore, high-quality epidemiological studies consistently refute a causal relationship between CSM and serious vascular injury.

Taken together, these findings support the conclusion that spinal manipulation, when properly performed, is a biomechanically safe procedure. Ongoing practitioner education, patient screening, and adherence to clinical guidelines will further ensure that manipulation remains a safe and effective component of conservative spinal care.

References

  1. Gorrell LM, Nyirö L, Pasquier M, Pagé I, Heneghan NR, Schweinhardt P, Descarreaux M. Spinal manipulation characteristics: a scoping literature review of force-time characteristics. Chiropr Man Therap. 2023 Sep 13;31(1):36.

  2. Fagundes C, Herzog W. Strain of the vertebral artery during passive neck movements and spinal manipulation. J Bodyw Mov Ther. 2024;40:569–574.

  3. Pickar JG. Neurophysiological effects of spinal manipulation. Spine J. 2002;2(5):357–371.

  4. Herzog W, Kawchuk GN, Conway PJ. Forces exerted during spinal manipulative therapies. Spine (Phila Pa 1976). 1993;18(9):1206–1212.

  5. Piper SL, Howarth SJ, Triano JJ, Herzog W. Quantifying strain in the vertebral artery with simultaneous motion analysis. Clin Biomech. 2014;29(10):1099–1107.

  6. Gorrell LM, Kuntze G, Ronsky JL, et al. Kinematics of the head and vertebral artery length changes during high‑velocity cervical manipulation. Chiropr Man Therap. 2022;30:28.

  7. Cassidy JD, Boyle E, Côté P, et al. Risk of vertebrobasilar stroke and chiropractic care: population-based case‑control and case‑crossover study. Spine. 2008;33(4 Suppl):S176–S183.

  8. Church E W, Sieg E P, Zalatimo O, et al. (February 16, 2016) Systematic Review and Meta-analysis of Chiropractic Care and Cervical Artery Dissection: No Evidence for Causation. Cureus 8(2): e498.

PostGradDC offers advanced post-graduate chiropractic continuing education. Our founder, Dr. James Demetrious, is a distinguished board-certified chiropractic orthopedist, educator, author, and editor. 

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© 2025 – James Demetrious, DC, DABCO. Open Access. Unrestricted use, distribution, and reproduction are allowed in any medium, provided you give appropriate credit by citing the original author and source: Demetrious J. PostGradDC. Chiropractic Spinal Manipulation and Ligament Safety: Evaluating Force Thresholds and Clinical Risk. PostGradDC.com; 2025.