The idea that the upper cervical spine and the pelvis are functionally linked is not new to chiropractic. It is foundational in some techniques, and conceptually central to chiropractic is the idea that everything is connected when it comes to the body and nervous system. What has been harder to come by is a measurable parameter that lets that relationship be examined on a radiograph, discussed with colleagues outside the profession, and tested.
A new paper published in the Asia-Pacific Chiropractic Journal asks the question, “Is the C2 slope a reliable indicator of decompensated spinopelvic alignment? A Sacro Occipital Technique perspective.” Authored by Weiner and Blum, it draws on a body of spine surgery research that has quietly developed over the past several years, and asks what it might mean for chiropractic.
It is published as a clinical exposition, that is a reasoned argument built from existing literature, anatomy and clinical observation. It doesn’t present new patient data, or test the hypothesis it puts forward. Thus, it should be read as a well-constructed proposition worth investigating, a hypothesis paper not as a finding.
The parameter the spine surgeons identified
The C2 slope is measured on a lateral radiograph as the angle between a line drawn along the lower endplate of the second cervical vertebra and the horizontal. It a single, easily-taken angle/measurement at the top of the spine that appears to carry information about how the whole spinal column is balanced.
A related parameter, the C2 pelvic angle (C2PA), links the C2 position directly to the pelvis. Weiner and Blum report that when the C2PA exceeds approximately 13° to 16°, it becomes an indicator of what the surgical literature calls decompensated spinopelvic alignment. This essentially means the body has run out of ways to compensate for a postural imbalance. This then correlates with poorer patient-reported outcomes, including lower SF-36 scores (A qualify of life survey) and increased pain.
They cite several sources for this. Protopsaltis and colleagues, writing in Spine in 2020, established the C2 slope as a marker of cervical deformity correlating with patient-reported outcomes. Work by Ha and colleagues examined the C2PA in relation to proximal junctional kyphosis. Joseph and colleagues published a validation of an equation relating changes in C2 pelvic angle and C2 tilt to changes in pelvic tilt. Ouchida and colleagues examined the C2PA as a predictive measure for decompensated alignment and health-related quality of life.
Notably, the exposition paper cited a radiographic study of volunteers with both high and low pelvic incidence in which, despite extreme variation in pelvic parameters, C2 tilt remained within 1° of L1 pelvic angles. If that holds, it suggests the body defends the position of the upper cervical spine with considerable determination, adjusting everything below to preserve it.
And that is a finding that is quite interesting when applied to chiropractic.
Sacro Occipital Technique, developed by DeJarnette, has long held that the pelvis and the head are intimately connected. It’s also a point that the exposition paper supports. The C2 slope literature, they suggest, offers a contemporary and independently-derived parameter that speaks to the same relationship.
They also connect it to the Lovett Brother phenomenon, the proposal within parts of the profession that vertebral segments function in paired relationships, with C2 often considered functionally coupled with L4. They go on to point out that L4 plays an important role in pelvic alignment.
There are a few other notable factors the authors then draw together.
- The asymmetrical tonic neck reflex (ATNR) links head rotation, guided largely by C1–C2 motion, to contralateral limb extension and pelvic shifts. This establishes a developmental connection between upper cervical rotation and lower body positioning.
- The symmetrical tonic neck reflex (STNR) regulates muscular tone in response to cervical flexion and extension, coupling neck movement to sagittal pelvic positioning.
- The cervicocollic and vestibulospinal reflexes stabilise head position, and the authors propose that their neural input modulates lumbar and pelvic musculature, so that disruption at C2 may provoke compensatory pelvic tilt in service of postural equilibrium.
- They also discuss the spinal Galant reflex, active in infancy to facilitate pelvic mobility, which they suggest may influence hip and pelvic tilt if retained beyond early development, and a cervicolumbar pathway carrying proprioceptive input from cervical muscles and ligaments near C2 to the lower spine, providing feedforward control that lets the brain anticipate pelvic change from cervical posture.
The proposed mechanism is summarised in the paper this way: when C2 tilts forward, represented radiographically by an increased C2 slope, the body may compensate by tilting the pelvis posteriorly in order to maintain balance and preserve visual and vestibular postural reflexes.
The myodural bridge
The authors then turn to the myodural bridge (MDB) or the connective tissue interface between the dura mater and the suboccipital musculature. These muscles originate from the C2 spinous process and transmit force through fascia to the cervical dura.
Its primary function is thought to be the prevention of dural infolding during cervical extension, which in turn supports normal cerebrospinal fluid circulation. The paper argues that altered C2 angulation may generate abnormal mechanical stress on the cervical dura through these muscles, and associates increased tension with chronic cervicocephalic headache syndromes, altered CSF dynamics and increased intracranial pressure.
Because the dura anchors caudally to the coccyx via the filum terminale, the authors describe a continuous anatomical and mechanical linkage from the upper cervical spine to the sacral base — a structural corollary to the neurological argument, and one with obvious resonance for SOT practice
This section describes proposed mechanisms drawn from anatomical and physiological literature. It is a coherent hypothesis around how the effect could occur, rather than evidence of why it does.
If a patient’s pelvic distortion is a downstream compensation for an upper cervical subluxation, what happens when the pelvis is corrected and the practice member returns to upright posture? Will the neuromusculoskeletal system simply reestablish the preexisting compensatory pattern? Should chiropractors therefore routinely check and adjust C2 beforeinitiating pelvic correction.
The authors note that in SOT protocol, cervical adjustment already tends to precede weight-bearing assessment, and suggest the category system may in practice already accommodate this relationship. Their closing call is for clinical investigation into whether evaluating C2 alignment prior to pelvic category correction enhances the stability and longevity of adjustments.
There are obviously a few questions that require further research to answer, but the hypothesis put forward by this paper is a strong one. We look forward to seeing whether it holds up under investigation, and we would encourage the authors and others to pursue it. In the mean time, this paper is one that is definitely worth the read to get all the clinically-relevant details rather than the short form blog version!
If you would like to support research of this kind, you can donate to the Australian Spinal Research Foundation here. www.spinalresearch.com.au
Reference
Weiner G, Blum CL. Is the C2 slope a reliable indicator of decompensated spinopelvic alignment? A Sacro Occipital Technique perspective. Asia-Pacific Chiropractic Journal. 2026;7.1. Available at: https://www.apcj.site/WeinerC2slope.pdf
