A partial shoulder replacement, known medically as hemiarthroplasty, is a surgical procedure designed to restore function in a damaged shoulder joint. This operation replaces only the damaged “ball” portion (the head of the humerus) with a prosthetic implant, leaving the natural “socket” or glenoid intact. For patients considering this surgery, the longevity of the implant is a primary concern when seeking a long-term solution for painful conditions like severe fractures or advanced arthritis.
Understanding Hemiarthroplasty
Hemiarthroplasty replaces the humeral head (the top of the upper arm bone) with a metal component, often featuring a stem extending into the bone. This partial replacement differs significantly from a total shoulder arthroplasty, which replaces both the ball and the socket with prosthetic parts. Surgeons select hemiarthroplasty when the glenoid socket is healthy or when patient factors, such as advanced age or a severe fracture, make a total replacement less suitable.
The preservation of the natural glenoid socket is a defining characteristic and potential advantage. While a total replacement uses a plastic socket component that can wear out, hemiarthroplasty relies on the patient’s existing cartilage on the socket side. This approach is often chosen for conditions like a severe proximal humerus fracture or avascular necrosis, where the blood supply to the humeral head is compromised but the glenoid is largely spared.
Typical Lifespan and Survival Rates
The longevity of a partial shoulder replacement is estimated using long-term clinical data on implant survival. In this context, “survival” refers to the time the implant remains functional without needing revision surgery. Pooled data from national joint registries provide reliable estimates for this duration.
The 10-year survival rate for humeral hemiarthroplasty is generally reported to be between 85.5% and 90.4%, depending on the underlying condition treated. This suggests that the majority of these implants are still functioning well a decade after the initial surgery. Ten-year survival rates for partial shoulder replacements tend to be slightly lower than those for total shoulder replacements, which are often reported in the 92% to 95% range.
Looking at longer-term survival, the rates naturally decrease, though reliable data becomes less common. Some studies estimate the overall 15-year survival rate without any complication, including persistent pain, to be around 61.5%. The long-term prognosis is heavily influenced by the initial reason for surgery, with patients treated for avascular necrosis often showing better 10-year survival rates compared to those treated for fracture sequelae.
Patient and Surgical Variables Affecting Duration
Several factors specific to the patient and the surgical technique influence the implant’s working life. A major factor is the patient’s age at the time of surgery, as younger, more active individuals place greater mechanical stress on the joint, leading to earlier wear and potential failure. Patients under the age of 60 often have a higher risk of requiring a future revision procedure.
The quality of the patient’s remaining glenoid socket is also a major predictor of longevity. Since the prosthetic ball articulates directly with the natural socket cartilage, the progression of arthritis or the development of glenoid erosion can shorten the implant’s lifespan. The risk of glenoid erosion (the wearing away of the socket bone) is a primary long-term concern with hemiarthroplasty.
Surgical precision is another variable, particularly the proper positioning and fixation of the humeral component. Errors in surgical technique, such as improper sizing or alignment, can lead to instability or abnormal wear patterns on the socket, contributing to earlier implant failure. The surgeon’s experience level has been shown to correlate with better outcomes and a potentially longer-lasting replacement.
Recognizing Implant Failure and Revision Procedures
The end of a partial shoulder replacement’s functional lifespan is typically signaled by a return of symptoms. The most common signs of a failing hemiarthroplasty include new or worsening chronic joint pain, often due to glenoid erosion or loosening of the implant stem within the bone. Patients may also experience a noticeable decrease in range of motion, a feeling of instability, or new sounds like clicking, popping, or grinding when moving the shoulder.
When these symptoms become debilitating, a second surgery, known as a revision procedure, is often necessary. For a failed hemiarthroplasty, the next step is frequently a conversion to a total shoulder arthroplasty, where a plastic component is placed into the socket to replace the eroded cartilage. Alternatively, in cases of severe rotator cuff damage or significant bone loss, the revision may involve converting the implant to a Reverse Total Shoulder Arthroplasty. Revision surgery offers a pathway to renewed pain relief and function.