Spinal Decompression Force Calculator
Estimates the traction force needed to decompress spinal segments, accounting for body weight, spinal region, table friction, and patient position. Results are for educational purposes only — always follow a licensed clinician's protocol.
Typical split-table: 0.4–0.6 | Frictionless (motorised): 0
0° = horizontal; positive = head-end elevated (lumbar) or declined (cervical)
Formulas Used
1. Segment Weight:
Wseg = BW × g × fseg
where fseg = 0.45 (lumbar, lower body) or 0.07 (cervical, head)
2. Normal Force on Table:
N = Wseg × cos(θ)
3. Friction Force (lumbar only):
Ffriction = μ × N = μ × Wseg × cos(θ)
4. Total Traction Force:
Ftraction = Wseg × cos(θ) + Ffriction
= Wseg × cos(θ) × (1 + μ) [lumbar]
= Wseg × cos(θ) [cervical, μ = 0]
5. Clinical Starting Dose:
Fstart = 0.50 × Ftraction
Assumptions & References
- Lower body (below L1) accounts for approximately 45% of total body weight (De Leva, 1996 — anthropometric segment data).
- Head accounts for approximately 7% of total body weight (Winter, 2009 — Biomechanics of Human Movement).
- Friction coefficient for a standard split traction table is typically 0.4–0.6; motorised/frictionless tables use μ ≈ 0.
- Lumbar traction guidelines recommend an initial force of 25–50% of body weight, progressing to 50% (Saunders, 2004 — Lumbar Traction: A Clinical Perspective).
- Cervical traction typically begins at 3–5 kgf and progresses to 8–15 kgf depending on pathology (Joghataei et al., 2004).
- Intradiscal pressure reduction of 30–50% at therapeutic traction forces reported by Nachemson & Elfström (1970) and Ramos & Martin (1994).
- Contraindications (not assessed here): malignancy, fracture, osteoporosis, pregnancy, aortic aneurysm, acute inflammation.
- This calculator does not replace clinical assessment or a licensed physiotherapist's / chiropractor's prescription.