The study population will be implanted with the ExploR® Modular Radial Head.

Inclusion Criteria:

The inclusion criteria will be the same as the indications stated in the FDA cleared (510(k) K040611) and (510(k) K051385) labeling for the device.

1. Replacement of the radial head for degenerative or post-traumatic disabilities presenting pain, crepitation, and decreased motion at the radio-humeral and/or proximal radio-ulnar joint with:

   1. Joint destruction and/or subluxation visible on x-ray
   2. Resistance to conservative treatment
2. Primary replacement after fracture of the radial head
3. Symptomatic sequelae after radial head resection
4. Revision following failed radial head arthroplasty

The device is intended for single use with or without bone cement.

Modular Radial Head replacement prostheses have received FDA clearance for cemented and non-cemented application.

Patient selection factors to be considered include: 1) need to obtain pain relief and improve function, 2) ability and willingness of the patient to follow instructions, including control of weight and activity levels, 3) a good nutritional state of the patient, and 4) the patient must have reached full skeletal maturity.

Exclusion Criteria:

The exclusion criteria will be the same as the contraindications stated in the FDA cleared labeling (510(k) K040611) and (510(k) K051385) for the device. These contraindications include:

Absolute contraindications:

1. Infection
2. Sepsis
3. Osteomyelitis

Relative contraindications:

1. Uncooperative patient or patient with neurologic disorders who is incapable or unwilling to follow directions
2. Osteoporosis
3. Metabolic disorders which may impair bone function
4. Osteomalacia
5. Distant foci of infections which may spread to the implant site
6. Rapid joint destruction, marked bone loss or bone resorption apparent on roentgenogram.