What is the neutral position for a sling in a surgical cervical humerus fracture?

Neutral Position for a Sling in Surgical Cervical Humerus Fracture

The neutral position for a sling in a surgical cervical humerus fracture is with the arm in neutral rotation (neither internally nor externally rotated), with slight abduction (approximately 20°) and slight internal rotation (approximately 20°) to minimize deforming forces on the fracture site.

Anatomical Considerations

When positioning a fractured humerus in a sling, the goal is to minimize deforming forces that could lead to malunion while promoting optimal healing. The neutral position helps to:

• Prevent varus deformity of the humeral head
• Balance muscular forces across the fracture site
• Provide accurate radiographic assessment
• Optimize functional outcomes

Evidence-Based Positioning Recommendations

Radiographic Assessment

Traditional radiographic assessment often uses the true anterior-posterior (AP) view with the patient's arm in a sling, typically resulting in internal rotation. However, research shows this can lead to misleading projections of the head shaft angle (HSA) 1:

• Internal rotation falsely suggests increased valgus angulation
• External rotation similarly distorts the true anatomical relationship
• Neutral rotation provides the most accurate assessment of fracture alignment

Biomechanical Considerations

Recent biomechanical studies demonstrate that specific arm positions can significantly affect deforming muscular forces across proximal humerus fractures 2:

• 20° glenohumeral abduction significantly decreases varus deformity caused by the subscapularis
• 20° internal rotation decreases deforming forces from both the subscapularis and supraspinatus
• This combined position (slight abduction with slight internal rotation) helps minimize fracture displacement

Clinical Outcomes

The N-brace trial provides preliminary evidence that neutral-rotation bracing may lead to superior outcomes compared to traditional simple sling positioning 3:

• Neutral rotation bracing showed trends toward:
  • Better functional scores (DASH, Oxford Shoulder Score, Constant-Murley)
  • Improved range of motion (elevation, external rotation, internal rotation)
  • Higher subjective shoulder values

Practical Application

When applying a sling for a patient with a surgically treated cervical humerus fracture:

1. Position the arm in neutral rotation (palm facing toward the body)
2. Provide approximately 20° of abduction (slight space between arm and torso)
3. Allow approximately 20° of internal rotation
4. Ensure the sling supports the entire forearm and elbow
5. Avoid excessive flexion at the elbow which can increase tension on the fracture site

Common Pitfalls to Avoid

• Excessive internal rotation: Traditional slings often place the arm in significant internal rotation, which can increase deforming forces and lead to malunion
• Lack of abduction: Keeping the arm directly against the torso increases tension on the supraspinatus and subscapularis
• Inconsistent positioning: Varying the arm position during follow-up radiographs can lead to inaccurate assessment of healing

Rehabilitation Considerations

Following the initial immobilization period:

• Early finger and hand motion is essential to prevent edema and stiffness 4
• Range-of-motion exercises including shoulder, elbow, wrist, and hand should begin within the first postoperative days as pain allows
• Above chest level activities should be restricted until fracture healing is evident

By maintaining the arm in a neutral position with slight abduction and internal rotation during the healing phase, you can minimize deforming forces on the fracture site and potentially improve functional outcomes.