Direct Vertebral Rotation (DVR) in Orthopaedics

Definition

Background / Historical Context

Indication

• Adolescent Idiopathic Scoliosis (AIS) - primary indication
• All curve types where transverse plane (axial rotation) correction is desired
• Especially useful in rigid or severe curves where rod rotation alone fails
• Thoracic curves with prominent rib hump (cosmetic deformity driven by vertebral rotation)

Prerequisites

• Bilateral pedicle screws at every level to be fused in the thoracic spine (all-pedicle-screw construct)
• Neuromonitoring: baseline motor-evoked potentials (MEPs) before any maneuver
• Mean arterial pressure (MAP) ≥ 70 mmHg during correction (to maintain spinal cord perfusion)
• Screw derotators (SUK tubes / derotation handles) attached to pedicle screw heads

Technique (Campbell's TECHNIQUE 40.14)

Step-by-Step

1. Insert bilateral pedicle screws at every thoracic level to be fused.
2. Establish baseline MEPs and maintain MAP ≥ 70 mmHg throughout.
3. Identify the neutral vertebra - the least rotated vertebra distally. Begin derotation proximal to this level.
4. Attach screw derotators (derotation handles/SUK tubes) onto the pedicle screws of the juxta-apical vertebrae on both concave and convex sides.
5. Derotate the vertebrae: For a right thoracic curve, rotate the apical and juxta-apical vertebrae clockwise in the transverse plane (opposite to the direction of vertebral rotation in the thoracic curve).
6. This can be done:
   • En bloc: multiple levels rotated simultaneously
   • Segmental: each individual level derotated separately
7. Rod insertion: A pre-contoured rod (for sagittal plane correction) is placed on the concave side first.
8. Rod rotation maneuver (RRM) is performed first (translates apex toward midline, corrects coronal plane), then DVR is performed on top of it for transverse plane correction.
9. After derotation, tighten all set screws and check MEPs again.
10. Place convex rod, apply compression/distraction as needed for final balancing.

Mechanism of Action

• On the convex side: downward force applied to the screw (pushing the prominent transverse process/rib posteriorly down)
• On the concave side: upward lifting force applied
• Net result: the vertebral body rotates back toward neutral, reducing the rib hump

DVR vs. Simple Rod Derotation (Rod Rotation Maneuver)

Advantages of DVR

1. True 3D correction - addresses the transverse plane (axial rotation) which rod rotation alone cannot reliably correct
2. Significantly better rotational correction (42.5% vs. 2.4%)
3. Better coronal plane correction
4. Reduces the rib hump - the most visible cosmetic deformity in thoracic scoliosis
5. Can be performed en bloc or segmentally depending on curve flexibility
6. Applicable to rigid and severe curves

Disadvantages / Complications

1. Requires bilateral all-pedicle-screw construct - technically demanding
2. Longer operative time and greater blood loss
3. Higher stress on pedicle screws - risk of screw pullout or plow
4. Neurological risk if MAP drops or MEPs are not monitored
5. Some recent studies (2023) suggest DVR may not offer superior clinical/radiological results compared to Differential Rod Contouring (DRC) in all patients

Flowchart: DVR Technique

PATIENT WITH AIS (Thoracic Curve with Rotational Deformity)
                          |
                          ▼
         Decision for Posterior Spinal Fusion
                          |
                          ▼
    Insert BILATERAL PEDICLE SCREWS at all levels to be fused
                          |
                          ▼
    Establish Baseline MEPs + Maintain MAP ≥ 70 mmHg
                          |
                          ▼
    Identify NEUTRAL VERTEBRA (least rotated) — begin derotation proximal to this level
                          |
                          ▼
    Place PRE-CONTOURED ROD on concave side (sagittal contour)
                          |
                          ▼
    Perform ROD ROTATION MANEUVER (RRM) — corrects coronal plane
                          |
                          ▼
    Attach SCREW DEROTATORS (SUK tubes) to bilateral pedicle screws
    at apical + juxta-apical vertebrae
                          |
                          ▼
         ┌─────────────────────────────┐
         │    DIRECT VERTEBRAL         │
         │    ROTATION (DVR)           │
         │                             │
         │  Right thoracic curve →     │
         │  Rotate CLOCKWISE           │
         │  (opposite to vertebral     │
         │  rotation direction)        │
         │                             │
         │  En Bloc OR Segmental       │
         └─────────────────────────────┘
                          |
                          ▼
    Tighten all SET SCREWS
                          |
                          ▼
    Check MEPs (post-maneuver)
                          |
                          ▼
    Place CONVEX ROD — compression/distraction
                          |
                          ▼
    Final balancing + lock all screws
                          |
                          ▼
    POST-OP: Early mobilization (POD#1), pain control (PCA/gabapentin/ketorolac)
                          |
                          ▼
    RESULT: 3D Correction — Coronal + Sagittal + TRANSVERSE PLANE

Key Points for Exam