A nerve root decompression position identified by 3D CT scan: the modified reversed contralateral position

Key points

1. 01MRCAR position combines lumbar axial rotation, side bending, and flexion simultaneously, opening the foramen from multiple planes at once
2. 02Foraminal cross-sectional area increased significantly both immediately on assuming the position and further after 48 hours of use, with large effect sizes across all disc levels (L3/L4, L4/L5, L5/S1)
3. 03Straight leg raise angle also improved significantly after 48 hours, indicating reduced nerve root tension and improved nerve mobility
4. 04Effect sizes were large (Cohen's d > 0.8) for most comparisons, except SLR in the L3/L4 group at the immediate time point (Cohen's d = 0.34)
5. 05The position may be a useful conservative option for patients who do not respond to standard physiotherapy, and can be self-applied as a home exercise

How it was conducted

Design

Three-group experimental study with repeated 3D-CT scan imaging at baseline, immediately after positioning, and after 48 hours of therapeutic use

Participants

90 males aged 20-40 years with unilateral lumbar disc prolapse (grade 2 paracentral or foraminal, 2-3 mm) and radiculopathy, 30 per group by disc level

Groups

Group A: L3/L4 prolapse; Group B: L4/L5 prolapse; Group C: L5/S1 prolapse

Intervention

Modified reversed contralateral axial rotation (MRCAR) position: side-lying on pain-free side over wedge pillow, trunk rotated away from painful side, used 4 times daily for 20 minutes over 48 hours

Primary outcomes

Cross-sectional area (CSA) of the lumbar intervertebral foramen (cm2) on 3D-CT scan and straight leg raise (SLR) angle (degrees)

Analysis

Mixed-design MANOVA with post-hoc pairwise comparisons and Cohen's d effect sizes; significance level 0.05

What they found

• CSA of LIVF at L3/L4: baseline 0.255 cm2, immediately after positioning 0.369 cm2, after 48 h 0.691 cm2 (all pairwise comparisons p = 0.001, Cohen's d: Image 1 vs 2 = 1.515, Image 1 vs 3 = 3.935, Image 2 vs 3 = 2.737)
• CSA of LIVF at L4/L5: baseline 0.171 cm2, immediately 0.296 cm2, after 48 h 0.566 cm2 (p = 0.001; Cohen's d: Image 1 vs 2 = 1.022, Image 1 vs 3 = 2.073, Image 2 vs 3 = 1.241)
• CSA of LIVF at L5/S1: baseline 0.134 cm2, immediately 0.202 cm2, after 48 h 0.441 cm2 (p = 0.001; Cohen's d: Image 1 vs 2 = 0.816, Image 1 vs 3 = 2.344, Image 2 vs 3 = 1.732)
• SLR angle at L3/L4: baseline 41.06 degrees, immediately 44.80 degrees, after 48 h 65.83 degrees (p = 0.001; Cohen's d Image 1 vs 2 = 0.342 [small], Image 1 vs 3 = 2.32, Image 2 vs 3 = 1.893)
• SLR angle at L4/L5: baseline 35.20 degrees, immediately 41.53 degrees, after 48 h 69.63 degrees (p = 0.001; Cohen's d Image 1 vs 2 = 1.016, Image 1 vs 3 = 4.605, Image 2 vs 3 = 3.596)
• SLR angle at L5/S1: baseline 29.26 degrees, immediately 35.93 degrees, after 48 h 65.23 degrees (p = 0.001; Cohen's d Image 1 vs 2 = 0.982, Image 1 vs 3 = 5.190, Image 2 vs 3 = 4.311)

Limitations

• Only young males (20-40 years) were studied; results may not apply to older patients, females, or those with different spinal pathologies
• No asymptomatic control group was included due to ethical concerns about repeated CT radiation exposure in healthy individuals
• Outcomes were measured only over 48 hours, so long-term clinical efficacy and durability of the decompression effect are unknown
• Potential inter-operator variability in achieving the standardized MRCAR position could affect reproducibility in clinical practice

Why it matters

For patients

Patients with lumbar disc prolapse causing leg pain may benefit from trying this specific lying position as a home exercise, particularly if standard treatments have not provided relief, though long-term benefit is not yet proven.

For clinicians

The MRCAR position is a standardized, reproducible manual therapy technique that produced measurable foraminal decompression on 3D-CT imaging and improved SLR range within 48 hours, making it a candidate for inclusion in conservative management of lumbar radiculopathy.

For readers

This is the first in-vivo 3D-CT imaging study to confirm that a combination trunk position can immediately enlarge the lumbar intervertebral foramen and reduce nerve root tension, providing an objective anatomical basis for positional decompression therapy.