Summary

Radial Head Fractures are the most common elbow fracture in adults (33%). They usually result from a Fall on Outstretched Hand (FOOSH) with the elbow extended and forearm pronated. Management is dictated by the Mason Classification and the presence of a Mechanical Block to rotation. While Mason I (undisplaced) fractures are treated with immediate mobilization to prevent stiffness, displaced fractures (Mason II/III) may require Open Reduction Internal Fixation (ORIF) or Arthroplasty (Replacement). The Radial Head is a secondary constraint to Valgus instability; therefore, if the Medial Collateral Ligament (MCL) is torn, the Radial Head cannot be excised without causing catastrophic instability. [1,2,3]

Key Facts

• Mechanism: Axial load on pronated forearm.
• The "Safe Zone": A 90-degree arc of the radial head that does not articulate with the proximal ulna. Hardware must be placed here to avoid impingement.
• Terrible Triad: Radial Head Fracture + Coronoid Fracture + Elbow Dislocation.
• Essex-Lopresti: Radial Head Fracture + Interosseous Membrane (IOM) rupture + DRUJ dislocation.

Clinical Pearls

"Aspirate to Differentiate": Pain prevents patients from moving, mimicking a block. Steps: 1. Aspirate the joint (remove blood). 2. Inject 10ml Lidocaine. 3. Re-examine. If they can rotate fully, it's a Mason I (treat conservatively). If there's a hard stop, it's a Mechanical Block (needs surgery).

"Check the Wrist": Always palpate the Distal Radio-Ulnar Joint (DRUJ). Tenderness here suggests an Essex-Lopresti injury. If you excise the radial head in these patients, the radius migrates proximally, destroying the wrist.

"The Soft Spot": The best place to aspirate or inject is the center of the triangle formed by the Olecranon, Radial Head, and Lateral Epicondyle.

                 RADIAL HEAD FRACTURE
                        ↓
            DISPLACED? MECHANICAL BLOCK?
            ┌───────────┴────────────┐
           NO                       YES
        (Mason I)            (Mason II/III/IV)
           ↓                         ↓
      NON-OPERATIVE             RECONSTRUCTABLE?
    (Sling <1 week)           ┌──────┴───────┐
     (Early ROM)             YES             NO
                              ↓              ↓
                            ORIF          LIGAMENTS (MCL/IOM)?
                       (Screw/Plate)      ┌──────┴───────┐
                                       INTACT          TORN
                                         ↓               ↓
                                      EXCISION      REPLACEMENT
                                   (Low demand)    (Metal Head)

Note: In Terrible Triad, the order is: 1. Fix Coronoid. 2. Fix/Replace Radial Head. 3. Repair LCL.

1. Conservative (Non-Operative)

• Indication: Mason I. Mason II with no block (and cooperative patient).
• Protocol:
  • Sling for comfort (3-5 days ONLY).
  • Active mobilization immediately.
  • No passive stretching (can cause heterotopic ossification).
  • Check X-ray at 1 week.
• Outcome: Good. Mild loss of extension (5-10 degrees) is common but functional.

2. Surgical Fixation (ORIF)

• Indication: Mason II with block. Simple Mason III.
• Technique:
  • Safe Zone: Between Radial Styloid and Lister's Tubercle lines. Does not articulate with Ulna. Plates must go here.
  • Implants: Headless compression screws (buried) or Low-profile plates.
  • Approach: Kocher (Posterolateral).

3. Radial Head Arthroplasty (Replacement)

• Indication: Comminuted Mason III/IV where fixation is impossible.
• Why not Excision?: If MCL is torn (Type IV), excision leads to valgus instability and proximal radial migration. Only replace, don't remove.
• Implants: Metallic (Cobalt Chrome). Press-fit or Cemented. Modular heads allow sizing.

4. Excision

• Indication: Comminuted fracture in low-demand elderly patient with intact MCL/IOM.
• Risk: Wrist pain (proximal migration). Valgus drift.

Mason (1954)

• Original description.
• Principles of early motion for undisplaced fractures remain standard of care.

Ring et al. (2002) - ORIF outcome

• Showed that ORIF of comminuted ( >3 fragments) radial head fractures has a high failure rate (loosening, non-union).
• Conclusion: If >3 fragments, move straight to Arthroplasty. Don't try to be a hero with 10 screws.

Kaan et al. (2010) - Implant survival

• Radial head arthroplasty has good long term survival (85% at 10 years).
• Better outcomes with metallic heads than Silastic (silicone) heads which fragmented (synovitis).

What is the plan?

We need to check if the bone is blocking movement. I will put some numbing medicine into your elbow joint. Once the pain is gone, I will ask you to turn your hand. If you can turn it fully, we don't need surgery. If it gets "stuck" on a bone chip, we need to go in and fix it.

Do I need a sling?

Only for a few days. The elbow gets stiff very quickly. You must start moving it as soon as you can tolerate.

Will my arm be straight again?

Most people lose the last little bit of straightening (5-10 degrees). You won't notice it day-to-day (you can still eat, comb hair, etc), but it might not lock out straight like the other side.

What are the risks of surgery?

Stiffness is the main one. There is also a small nerve (PIN) that lifts your fingers which runs very close to the incision. We are very careful with it, but temporary weakness can occur.

Q1: Define the "Safe Zone" for radial head plating. A: It is a 90-degree arc of the radial head that does not articulate with the sigmoid notch of the ulna during rotation. It corresponds to the area between the radial styloid and Lister's tubercle (with the forearm neutral). Hardware placed here will not impinge.

Q2: What is the "Terrible Triad" and the order of fixation? A: Radial Head Fracture, Coronoid Fracture, Elbow Dislocation.

• Fixation Order:
  1. Fix/Replace Radial Head (restores lateral column).
  2. Fix Coronoid (restores anterior stability).
  3. Repair LCL (restores varus stability).
  4. MCL usually heals without repair if joint is congruent.

Q3: Why perform an aspiration test? A: To distinguish between a mechanical block (bone fragment) and a functional block (pain/spasm). If ROM returns after Lidocaine injection, surgery can be avoided.

(End of Topic)