Types of Hip Arthroplasty Surgery

The term "arthroplasty" refers to the re-surfacing or replacement of part or all of the articular surfaces of an end-stage arthritic joint.

When it comes to arthroplasty procedures for the hip, there are a few major varieties that are currently employed. These procedures can range from a partial replacement, or "hemi-arthroplasty," to a full replacement, called a "total hip" arthroplasty. Additionally, there is another procedure that is becoming more and more popular among the younger, more active patient; it is known as the "hip re-surfacing" procedure.

Hip Hemi-Arthroplasty

• "Hip hemi-arthroplasty" refers to the partial replacement of the hip joint. This particular type of procedure is frequently performed for two primary reasons: arthritis and fractures. In either case, the procedures remains essentially the same.

  When performing a hemi-arthroplasty, the femoral head is excised (removed) and the femoral canal is reamed to accommodate a specific stem implant type. Once this has been done, the removed femoral head is "sized" and a corresponding "head" implant is chosen that will fit most normally in the patient's socket. The types are: (1) uni-polar head, (2) bi-polar head.

The Uni-polar, Endoprosthetic Head

• This type of head implant is frequently used in treating the elderly, geriatric hip fracture where the quickest and easiest method and implant are preferred. The uni-polar head is a one-piece head that can be size-matched to the removed femoral head of the patient.

  Geriatric fractures are typically experienced by patients whose health is already compromised, so quick surgical intervention is imperative. The hemi-arthroplasty with a one-piece uni-polar head and stem offers that speed option.

The Bi-polar, Bi-artioculate Head

• This type of head implant comes in a two-piece version that is made for movement of both parts in multiple planes within the hip socket. One part serves as the femoral head, while the other is sized-matched to the patient's socket for best fit and stability.

  Once snapped together, the bi-polar moves freely upon itself, in multiple planes, for free mobility within the patient's own socket. It is believed that this type of hip head implant is less wearing on the patient's host socket, and is frequently used in a younger patient in an effort to prolong any additional revision surgery.

The Total Hip Arthroplasty

• This type of arthroplasty is, by far, the most widely and frequently performed hip arthroplasty. It is performed as primary treatment for end-stage degenerative arthritis of the hip.

  Its parts consist of a femoral stem, an acetabluar component and a liner, which can made of one of several different materials.

  The "liner" can be made of high-density plastic, ceramic material or polished metal, depending on the type of hip used.

  In the case of metal-on-metal combinations, the femoral head implant is typically very large, approximating the patient's own head size. This ultimately articulates with a polished metal surfaced acetabular component, and is a very stable combination.

  The use of plastic or ceramic tends to require the use of smaller head implants so a sufficient thickness of liner can be placed between the opposing metal parts.

Cemented vs. Bio In-growth

• Hip arthroplasty implants must be secured to the patient's bone in one of two ways: cement the parts or use a press-fit bio in-growth material that stimulates the bone to literally "heal" to the implant surfaces.

  Today, it is rare to see an acetabular implant cemented into the patient's own socket, mainly because of the history of ultimate loosening of the cement and the increased potential for infection. The stem is frequently cemented in, although it is up to the surgeon's discretion to decide which type would be best suited to the patient.