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- Discussion:
    - fissure or margin sector fracture w/ displacement less than 2 mm;
    - type I fractures may be difficult to identify;
    - fat pads are intracapsular but extrasynovial;
    - anterior fat pad is normally visible anterioir to coronoid fossa;
    - posterior fat pad sign is pathologic & should suggest need for further oblique views, including radial head capitellum view;
    - there is no mechanical block to motion;

- Radiographs:
   - type I frx are nondisplaced & may be missed on routine radiographs;
   - posterior fat pad sign is pathologic & should suggest further oblique views, including radial head-capitellum (RHC) view.

- Non Operative Treatment:
    - undisplaced frx, should be treated non-operatively;
    - these have excellent prognosis;
    - aspirate hemotoma & inject joint w/ local anesthetic with epinephrine.
    - patient is given a sling or splinted for a few days;
    - begin early ROM, usually w/in several days or as early as pain allows.
    - important to mobilized the joint early to avoid post traumatic stiffness;
          - active forearm rotation is started as soon as tolerated;
          - good to excellent function after 2-3 months;
          - may expect some loss of extension;
          - w/ concomitant post elbow dislocation, early ROM is recomended;
          - early motion is assoc w/ 90 % chance of good result;
    - early ROM, however, should be considered cautiosly when frx involves a large segment of the articular surface (1/3)
         - in the active individual, fractures involving > one third of articular surface
                should be treated w/ sling or splint support for minimum of two weeks;

- Non Union:
    - non-union occurs in about 5 % of Mason Type-I injuries;
    - rx of symptomatic non-union is radial head resection.
         - it is not helpful to remove only non union frx frag, as this tends to cause residual radial head to subluxate;

- Misc Complications:
    - include loss of elbow extension, mild loss of forearm rotation, and occasional aching with use.

- References:

Mason Type I Fractures of the Radial Head

Management of Mason type 1 radial head fractures: a regional survey and a review of literature.

Mason I fracture - a simple injury?

Long-term results and treatment modalities of conservatively treated Broberg-Morrey type 1 radial head fractures.

Minimally displaced radial head/neck fractures (Mason type-I, OTA types 21A2.2 and 21B2.1): are we "over treating" our patients?

Treatment of traumatic effusion in the elbow joint: a prospective, randomized study of 62 consecutive patients.