Coding for a total hip arthroplasty using resurfacing implants was last addressed in the October 2005 AAOS Bulletin. At that time, the AAOS Coding, Coverage, and Reimbursement Committee recommended using the hemiarthroplasty code when only the femoral side of the joint was replaced.

But what code or codes should be reported when both the femoral head and acetabulum are treated with resurfacing implants? A discussion of these procedures and the current CPT codes available for consideration can help answer that question.

Background on hip arthroplasty
Arthroplasty (literally “formation of joint”) is a surgical procedure in which the arthritic joint surface is replaced or the joint is remodeled or realigned by osteotomy or some other procedure. For example, in an interpositional arthroplasty, some type of tissue such as skin, muscle, fascia, or tendon is used to separate inflamed joint surfaces. Alternatively, in an excisional arthroplasty, the joint surface and bone are removed, leaving scar tissue to form in the gap between the two articulating parts.

For the last 45 years, the most successful and common form of arthroplasty has been the surgical replacement of an arthritic, inflamed, destroyed, injured, or necrotic joint or joint surface with a prosthesis. For example a hip joint that is affected by osteoarthritis may be replaced entirely (total hip arthroplasty) with a prosthetic hip joint. Both the acetabulum (hip socket) and the proximal part of the femur (femoral head) would be replaced. Such a procedure relieves pain, restores range of motion, and improves walking ability, thus leading to the improvement of muscle strength and overall function.

In the United States, metal-on-metal hip arthroplasty dates back to the 1960s, followed a decade later by metal-on-polyethylene (“poly”) total hip resurfacing. Outside the United States, metal-on-metal hip resurfacing has a 10- to 15-year track record with better results than early metal-on-poly articulations. As a result, there is renewed enthusiasm for hip resurfacing in the United States with improved bearing surfaces.

Benefits of hip resurfacing
Total hip resurfacing offers potential advantages to selected patients—especially young, active, high-demand patients. Among the proposed benefits of resurfacing are the following:

• bone retention for future revisions
• less stress shielding
• fewer dislocations than conventional total hip arthroplasties
• fewer postoperative activity restrictions, based on physician preference

Hip resurfacing procedures fall into two categories. In a partial resurfacing arthroplasty, a shell or “cap” is implanted over the femoral head. A total resurfacing arthroplasty involves both the implantation of the femoral head shell and the insertion of an acetabular cup.

Total hip resurfacing vs. total hip replacement
Total hip resurfacing is similar to a total hip replacement and is correctly classified as a total hip arthroplasty. The femoral head is reshaped and resurfaced or “capped” with a metal or ceramic mushroom-like implant. This cap may or may not include a stem and is usually cemented in place. The acetabulum is prepared as it would be in a traditional total hip replacement and the socket is “press fitted” (no screws are used) into the acetabulum. Most hip surgeons believe that this procedure preserves more bone than a traditional hip replacement surgery, especially on the femoral side—an advantage in case of a future revision surgery.

As a variation of a total hip replacement, resurfacing conserves both the femoral neck and part of the femoral head. Only the worn out or arthritic surfaces of the hip joint are replaced.

Coding resurfacing procedures
CPT code 27125 is described as a “Hemiarthroplasty, hip, partial (eg, femoral stem prosthesis, bipolar arthroplasty).” It is to be used for hip reconstruction procedures that are generally elective. It must be distinguished from CPT code 27236, which is used only for hip fractures that are treated with either a hemiarthroplasty (unipolar or bipolar) or open reduction with internal fixation (ORIF). (See Table 1.)

Although osteonecrosis of the femoral head is more commonly treated with a total hip arthroplasty, CPT code 27125 would be used when a femoral component hemiarthroplasty procedure is performed for osteonecrosis of the femoral head. CPT code 27125 is also the appropriate code for a femoral head resurfacing procedure, when only the head of the femur is replaced (a femoral component hemiarthroplasty). The code describes a partial “arthroplasty” procedure and is appropriately used for the femoral head resurfacing or a partial arthroplasty procedure.

CPT code 27130 describes an “Arthroplasty, acetabular and proximal femoral prosthetic replacement (total hip arthroplasty), with or with-out autograft or allograft.” This code accurately describes both total hip arthroplasty and total hip resurfacing pro-

cedures. It does not specify the amount of acetabular bone or proximal femoral bone replaced by prosthetic components or the type of bearing surface(s) used in the procedures.

CPT code 27130 is the correct code to use for every procedure that involves replacement of both hip joint surfaces (femoral and acetabular articular surfaces) with prosthetic implants, whether the implants are metal-on-polyethylene, metal-on-metal, ceramic-on-ceramic, or some other combination. As noted previously, metal-on-metal bearing surfaces have been used for decades, and the bearing surface has no relationship to the selection of CPT code. Whenever both joint surfaces are replaced with prosthetic implants, CPT code 27130 should be used.

Mary LeGrand, RN, MA, CCS-P, CPC is a coding specialist with KarenZupko and Associates. M. Bradford Henley, MD, MBA; Frank R. Voss, MD; Kevin J. Bozic, MD, MBA; Robert L. Barrack, MD; and Thomas P. Schmalzried, MD, are or have served on the AAOS Coding, Coverage, and Reimbursement Committee.