From the Guidelines
Hemiarthroplasty of the hip can be categorized into two main types: unipolar and bipolar hemiarthroplasty, which can be equally beneficial in patients with unstable femoral neck fractures, as suggested by the American Academy of Orthopaedic Surgeons in 2022 1. The main difference between these types lies in their design and articulation.
- Unipolar hemiarthroplasty features a single articulating surface that interfaces directly with the native acetabulum, which may cause more acetabular wear over time.
- Bipolar hemiarthroplasty, on the other hand, contains an additional articulation between the femoral head and an outer polyethylene-lined shell that interfaces with the acetabulum, theoretically reducing acetabular erosion and providing greater range of motion. Other types of hemiarthroplasty include cemented and uncemented designs, which differ in their method of fixation.
- Cemented hemiarthroplasties use bone cement for fixation and provide immediate stability, making them suitable for elderly patients with poor bone quality.
- Uncemented designs rely on biological fixation through bone ingrowth into porous surfaces and are typically used in younger, more active patients with good bone quality. The choice between these types depends on patient factors, including age, activity level, bone quality, and anticipated lifespan, with the goal of providing pain relief and functional improvement while minimizing complications, as implied by the moderate strength of recommendation from the American Academy of Orthopaedic Surgeons 1.
From the Research
Types of Hemiarthroplasty of the Hip
The different types of hemiarthroplasty of the hip include:
- Unipolar hemiarthroplasty: This type of hemiarthroplasty involves replacing the femoral head with a single artificial component that articulates with the natural acetabulum 2, 3, 4, 5.
- Bipolar hemiarthroplasty: This type of hemiarthroplasty involves replacing the femoral head with an artificial component that has a moving head within a outer shell, allowing for greater mobility and reducing the risk of acetabular wear 2, 3, 4, 5.
Comparison of Unipolar and Bipolar Hemiarthroplasty
Studies have compared the outcomes of unipolar and bipolar hemiarthroplasty, with some finding that bipolar hemiarthroplasty results in better functional outcomes and a lower risk of complications 3, 4, 5. However, other studies have found no significant difference between the two types of hemiarthroplasty 2, 4.
Surgical Approaches for Hemiarthroplasty
The surgical approach used for hemiarthroplasty can also vary, with the most common approaches being the direct lateral approach and the posterior approach 6. The choice of approach can affect the risk of dislocation and other complications, with some studies suggesting that the direct lateral approach may be associated with a lower risk of dislocation 6.