Quick answer: A hemiarthroplasty, or partial shoulder replacement, replaces only the ball of the shoulder and leaves your natural socket in place. It works best when the socket cartilage is still healthy, as in avascular necrosis or arthritis limited to the ball [3]. For arthritis that involves both sides of the joint, total shoulder replacement generally gives better pain relief [1, 2, 6]. A pyrocarbon hemiarthroplasty uses a head made of pyrolytic carbon, which is designed to be gentler on the natural socket than metal; early and mid-term results are encouraging, but longer follow-up is still needed [4, 5].
What Is a Hemiarthroplasty?
The shoulder is a ball-and-socket joint. In a total shoulder replacement both surfaces are replaced. In a hemiarthroplasty, only the ball (humeral head) is replaced with an implant, and the patient's own socket (glenoid) is kept.
The main advantage is that there is no plastic socket component that can wear or loosen over time. The main concern is that the natural socket can gradually wear against the implant, which can bring pain back [1, 2].
When Does a Hemiarthroplasty Make Sense?
- Avascular necrosis, when the ball has collapsed but the socket cartilage is preserved [3]
- Arthritis limited to the ball of the shoulder
- Some fractures of the top of the arm bone
- Younger, active patients who want to avoid a plastic socket component, after a careful discussion of the trade-offs
For osteoarthritis that has worn both the ball and the socket, a meta-analysis found that total shoulder replacement produced better pain relief and function than hemiarthroplasty [1], and a systematic review of younger patients reached a similar conclusion [2]. This is why the AAOS guideline favors total shoulder replacement for most patients with glenohumeral osteoarthritis [6].
What Is Pyrocarbon?
Pyrolytic carbon (pyrocarbon) is a very smooth material whose stiffness is closer to bone than metal. Used for the humeral head, it is designed to cause less wear on the natural socket cartilage than a traditional metal head.
What the research shows so far:
- A systematic review of pyrocarbon hemiarthroplasty found improvements in motion and patient-reported outcomes, a revision rate of about 8%, and some socket wear on X-rays at a minimum of two years [4].
- A five-year study of pyrocarbon hemiarthroplasty for arthritis and osteonecrosis reported its radiographic and clinical outcomes in detail [5].
- Longer-term studies are still needed to show how well pyrocarbon protects the socket over decades [4].
If It Wears Out
If the socket wears or pain returns, a hemiarthroplasty can usually be converted to a total or reverse shoulder replacement. In the pyrocarbon review, most revisions were conversions of this kind [4].
Choosing the Right Replacement
The right implant depends on the condition of your socket and rotator cuff, your age, activity level and goals. Dr. Joshi performs anatomic, reverse, hemiarthroplasty and pyrocarbon hemiarthroplasty and reviews these options with each patient. See Hemiarthroplasty & Pyrocarbon, Understanding Anatomic Total Shoulder Replacement and Types of Shoulder Replacement.
References
- Bryant D, Litchfield R, Sandow M, et al. A comparison of pain, strength, range of motion, and functional outcomes after hemiarthroplasty and total shoulder arthroplasty in patients with osteoarthritis of the shoulder. A systematic review and meta-analysis. J Bone Joint Surg Am. 2005;87(9):1947-56. PubMed 16140808 · doi.org/10.2106/JBJS.D.02854
- Sayegh ET, Mascarenhas R, Chalmers PN, et al. Surgical Treatment Options for Glenohumeral Arthritis in Young Patients: A Systematic Review and Meta-analysis. Arthroscopy. 2015;31(6):1156-1166.e8. PubMed 25543246 · doi.org/10.1016/j.arthro.2014.11.012
- Ristow JJ, Ellison CM, Mickschl DJ, et al. Outcomes of shoulder replacement in humeral head avascular necrosis. J Shoulder Elbow Surg. 2019;28(1):9-14. PubMed 30224207 · doi.org/10.1016/j.jse.2018.06.031
- Park CN, Zhang GX, Chang J, et al. Pyrocarbon hemiarthroplasty of the shoulder: a systematic review and meta-analysis of clinical results. J Shoulder Elbow Surg. 2023;32(6):1323-1332. PubMed 36610477 · doi.org/10.1016/j.jse.2022.12.005
- Griswold BG, Berger JM, Davis BP, et al. Five-Year Radiographic and Clinical Outcomes of Pyrocarbon Hemiarthroplasty for Glenohumeral Arthritis and Osteonecrosis. J Bone Joint Surg Am. 2025;107(24):2751-2762. PubMed 41231915 · doi.org/10.2106/JBJS.25.00163
- American Academy of Orthopaedic Surgeons. Management of Glenohumeral Joint Osteoarthritis: Evidence-Based Clinical Practice Guideline. 2020. www.aaos.org/globalassets/quality-and-pr