Bone Loss: Major Obstacle to Hip Replacement RevisionHip Joint replacements are becoming common place these days. Last year, there were 300,000 total hip arthroplasty (THA) procedures done in the United States. Younger, more active patients are getting their hips replaced. And that means an anticipated higher number of revision (re-do or second) surgeries. Surgeons planning a second or revision surgery after the first total hip replacement must consider many factors. The biggest and most important one is bone loss.
But before we explore the ways around this problem, let's look at the reasons primary (first or original) hip replacements fail. There are four major reasons for implant failure that require revision surgery: 1) aseptic (without infection) loosening, 2) hip instability (partial or complete dislocation), 3) osteolysis (bone loss) around the implant, and 4) periprosthetic (around the implant) infection.
As you can see from the list, bone loss is a big problem that must be addressed whenever a second surgery is planned. In fact, it's not just bone loss but also bone quality or density (called bone stock) that must be considered. And there are different patterns of bone loss from patient to patient. So, it's never a one-surgery-fits-all kind of problem.
Each patient must be carefully evaluated before surgery (pre-operatively). X-rays and CT scans provide the surgeon with details needed in the planning process. Is there infection that must be dealt with? What's the patient's general health? (Is the patient healthy enough to have another major surgery)? How much bone loss was caused by the first surgery? Is there already a leg-length difference that could get worse with a second (revision) procedure where more bone will have to be removed?
Other factors the surgeon must look at include the presence of cement and/or hardware (metal plates, screws, wires) that must be removed; location of blood vessels, nerves, and ureters (tube from the kidneys to the bladder) in relation to the acetabulum (hip socket); scar tissue from previous surgeries; and damage from radiation for cancer in the pelvis.
To aid surgeons in evaluating and treating patients with bone loss of the acetabulum (hip socket), orthopedic surgeons from three large medical centers wrote an article addressing all of these issues. They presented (with X-rays and drawings) the many different types and patterns of bone loss surgeons may encounter. Classification methods to describe bone loss of the acetabulum and articular (hip joint) surface are also provided.
In this article, the surgeons gave detailed descriptions of reconstruction methods. Some of the procedures involve different ways to perform osteotomies (removing portions of bone) to alter the angle of the bone or to lengthen the femur (thigh bone). An osteotomy can help make up for significant leg length differences.
Bone grafting techniques (e.g., impaction grafting, structural allograft, morcellized bone graft) used in the reconstruction of the hip are discussed. Long-term results from other studies are reviewed to help surgeons identify ways to aid their own patients in gaining the best results for the longest period of time.
Types of acetabular sockets (or cups) are examined using X-rays, pictures, and intraoperative photos and ways to secure the implants are presented. Cases discussed involve patients with such severe bone loss that sometimes the new hip implant has to be custom made to fit the patient.
In severe cases like these, the surgeon has to find inventive and creative ways to attach the implant. When the bone quality is so poor or the defect so large that there's no place to firmly anchor the component part, a special triflange component is used. This device, made to bridge large gaps in the bone, is a featured topic.
And to add to the surgeon's challenge, cost considerations, the ability of the patient's body to create bone ingrowth around the implant to secure it, and the long-term effects of stiff metal interfacing with living bone must all be reviewed and evaluated.
In summary, sometimes patients need a revision of their original (primary) hip joint replacement. This is a complex and challenging procedure for the surgeon, especially when any of the factors affecting the bone discussed here are present.
Every effort to manage patient pain is made using conservative means before considering revision surgery. When the problem is infection, other treatment should be tried first (e.g., antibiotics, debridement). When weakness is causing pain and difficulty walking, physical therapy should be provided. But in the end, when all other efforts to salvage the joint fail, revision surgery may be necessary. And that's when the information in this article will be of great value to the surgeon.
Neil P. Sheth, MD. Acetabular Bone Loss in Revision Total Hip Arthroplasty: Evaluation and Management. In Journal of the American Academy of Orthopaedic Surgeons. March 2013. Vol. 21. No. 3. Pp. 128-139.
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