29/04/2025
Just out 🔥
A Nerve Root Decompression Position Identified by 3D CT Scan: The Modified Reversed Contralateral Axial Rotation Position for Patients with Lumbar Disc Prolapse
▶️ Background:
👉 Radiculopathy is a neuromechanical condition characterized by nerve root compression and foraminal constriction (https://pubmed.ncbi.nlm.nih.gov/30215025/). As a mechanical lesion, disc herniation is the major pathophysiology that tends to impact the nerve root. The dimensions of LIVF constantly change throughout daily activities (https://pubmed.ncbi.nlm.nih.gov/11317109/). Therefore, symptoms of nerve root compression can be exacerbated or attenuated by the posture of the lumbar spine. One of the conservative nerve root decompression approaches is a manual orthopaedic physiotherapy technique known as positional decompression (https://www.tandfonline.com/doi/abs/10.1179/106698101790819707).
📘 A brand-new study by Raffet and colleagues investigates the effectiveness of a specific trunk position, the modified reversed contralateral axial rotation (MRCAR) position, in reducing nerve root compression using 3D-CT imaging in 90 males aged between 20 and 40 years with unilateral lumbar disc prolapse and radiculopathy (https://pubmed.ncbi.nlm.nih.gov/40247336/, figure 1)
👉 The Modified Reversed Contralateral Axial Rotation (MRCAR) position is a multiplanar trunk posture designed to decompress impinged nerve roots in patients with unilateral lumbar disc prolapse and radiculopathy. It builds upon the concept of the "reverse rotation strain" position introduced by Cyriax in 1993, which involved lumbar axial rotation in the transverse plane (https://catalog.nlm.nih.gov/discovery/fulldisplay?docid=alma997430873406676&context=L&vid=01NLM_INST:01NLM_INST&lang=en&search_scope=MyInstitution&adaptor=Local%20Search%20Engine&tab=LibraryCatalog&query=lds56,contains,Orthopedics%20--%20methods,AND&mode=advanced&offset=20).
👉 The MRCAR position enhances this by integrating movements in three anatomical planes—transverse (axial rotation), frontal (side bending), and sagittal (flexion)—to maximize the opening of the lumbar intervertebral foramen (LIVF). This position is standardized to ensure consistent application and is intended for both diagnostic imaging and therapeutic intervention.
✅ Positioning Details (s.illustrations, figure 2):
👉 Starting Position: The patient lies on their side on the pain-free side to avoid exacerbating symptoms on the affected side.
👉 A hard wedge pillow (30 cm in height, 75 cm in length) is placed beneath the pelvic region, with the upper edge of the wedge just above the iliac crest. This elevates the pelvis, facilitating lumbar side bending toward the pain-free side.
👉 Trunk Orientation: The trunk is rotated into a semi-prone position, directed away from the painful side and opposite to the pelvis rotation. This contralateral axial rotation is critical for opening the LIVF on the affected side.
👉 The trunk is also laterally bent (side bending) toward the pain-free side, further enhancing foraminal dimensions.
👉 Limb Positioning: Uppermost limb (affected side): The hip and knee are fully extended, with the patient instructed to exert a gentle post-end-range push backward and downward to maximize the position’s effect (self-augmented maneuver).
👉 Lowermost limb (pain free side): The hip and knee are flexed to approximately 90°, which helps stabilize the pelvis and maintain the desired lumbar curvature.
👉 Arms: Both shoulders are abducted to 90°, with arms resting on the bed. The forearms hang off the bed with elbows flexed at 90°, ensuring a relaxed upper body posture that does not interfere with trunk rotation.
👉 Therapeutic Application: Patients are educated to adopt the MRCAR position four times daily for 20 minutes each session as a therapeutic intervention.
🤔 Biomechanical Rationale:
The MRCAR position leverages the combined effects of lumbar axial rotation, side bending, and flexion to increase the cross-sectional area (CSA) of the LIVF (s. figure 3). Previous studies have shown that (https://pubmed.ncbi.nlm.nih.gov/11317109/):
➖ Lumbar flexion increases LIVF width, height, and area by approximately
11.3%.
➖ Side bending toward the opposite side increases LIVF dimensions by about 8.0%.
➖ Axial rotation to the opposite side enhances LIVF height and area by roughly 6.5%.
👉 By integrating these movements, the MRCAR position creates a synergistic effect, significantly enlarging the LIVF and reducing pressure on compressed nerve roots. This decompression is supposed to alleviate mechanical stress, improve blood flow, and reduce inflammation, potentially mitigating radicular symptoms.
▶️ Methods:
🧍♂️ Participants: Ninety male patients (aged 20–40) with unilateral lumbar disc prolapse at L3/L4, L4/L5, or L5/S1 levels were divided into three groups (30 per group) based on prolapse level.
Imaging: 3D-CT scans were conducted in three sessions:
1️⃣ Baseline-Image 1: Supine position.
2️⃣ Image 2: MRCAR position (side-lying on the pain-free side with lumbar axial rotation, side bending, and flexion).
3️⃣ Image 3: MRCAR position after 48 hours of therapeutic use (4 times daily, 20 minutes each).
👉 Measurements: CSA of the LIVF and SLR test angles were measured after each imaging session.
👉 Intervention: Patients adopted the MRCAR position as a therapeutic maneuver for 48 hours between Images 2 and 3.
📊 Results:
👉 The MRCAR position significantly increased the CSA of the LIVF and SLR test angles in Image 2 compared to Baseline-Image 1 across all groups (p=0.001, large effect sizes except for a small effect on SLR in L3/L4 group).
👉 After 48 hours of therapeutic use (Image 3), both CSA and SLR angles further increased significantly compared to Image 2 and Baseline-Image 1 (p=0.001, large effect sizes)
👉 Descriptive statistics showed: CSA (cm²): Increased from 0.255 (L3/L4), 0.171 (L4/L5), 0.134 (L5/S1) at baseline to 0.691, 0.566, 0.441 respectively in Image 3.
👉 SLR (degrees): Increased from 41.06 (L3/L4), 35.20 (L4/L5), 29.26 (L5/S1) at baseline to 65.83, 69.63, 65.23 in Image 3. (s. figure 4)
▶️ Discussion:
✔️ The MRCAR position, combining lumbar axial rotation, side bending, and flexion, effectively opens the LIVF, reducing nerve root compression and improving nerve mobility, as evidenced by increased CSA and SLR angles.
✔️The findings align with prior studies showing that specific lumbar positions (e.g., flexion, side bending) increase LIVF dimensions, potentially relieving nerve compression.
✔️ The MRCAR position may counteract mechanisms of radiculopathy (e.g., mechanical compression, inflammation, ischemia) by enlarging the LIVF, improving blood flow, and reducing neural sensitivity.
✔️ Unlike positions promoting centralization (e.g., lumbar extension), MRCAR may be suitable for patients where extension worsens symptoms.
🚫 Limitations:
🚫 Only young male participants were included, limiting generalizability to females or older individuals.
🚫 Lack of a control group
🚫 Short-term (48-hour) intervention period; long-term clinical outcomes need further study.
🚫 Potential variability in achieving the MRCAR position.
‼️ RCTs include long-term clinical data are needed to evaluate its real clinical value.
💡Conclusion: The MRCAR position significantly increases LIVF CSA and SLR range, offering a real-time decompression effect on impinged nerve roots in patients with unilateral lumbar disc prolapse and radiculopathy. It holds potential as a non-surgical technique for conservative management, particularly for those unresponsive to other treatments.
