Hemiarthroplasty is when the surgeon places an implant on only one side of the joint. For instance, a shoulder hemiarthroplasty would replace only the humeral side and would not place an implant on the glenoid (opposing) side. The benefit to this type of procedure is that there is less damage done to the joint.
Hemiarthroplasty prostheses utilizing a stem were originally intended for fracture repair and their use as an implant for focal arthritis and cartilage damage is being reconsidered by some thought leaders. Hemiarthroplasty is typically indicated when there is little to no damage on the opposing side. Several studies have shown that hemiarthroplasty is an effective treatment in the hip, toe, and shoulder when it is implanted anatomically. These include some of the longest surviving unrevised implants reported to date (e.g., 46 years and 30 years for the hip and knee respectively).
Resurfacing arthroplasty is a type of hemiarthroplasty procedure that surgeons perform when they only need to restore one articular surface of a joint. The implant is quite different from the typical hemiarthroplasty prosthesis as it does not have a long stem placed into the bone canal. Resurfacing is the "next generation" of arthroplasty in that patients do not necessarily need to have a stemmed prosthesis/implant if the joint is damaged on the articular surface. This operation removes less bone and typically leaves more options if future surgery is required. The Arthrosurface HemiCAP system is considered to be the next generation in cartilage resurfacing procedures for the middle aged.
Clinical outcome analyses that have examined the safety and efficacy of hemiarthroplasty devices have led reviewers to conclude that hemiarthroplasties can provide consistent and predictable pain relief as part of an interim treatment for specific patient populations. Additionally, the relative absence of complications (particularly osteolysis), plastic component loosening and the ease of conversion to a primary prosthetic are also cited.