New studies unveil latest information on hip care at AAOS meeting

American Academy of Orthopaedic SurgeonsFeb 19 2011

At today's 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS) three new studies unveil the latest in hip care.  

Who is More Likely to Need Revision Surgery 12 Years after Total Hip Replacement (THR)?

This study – and the first of its kind – analyzed Medicare beneficiaries who had elective primary THR for osteoarthritis between July 1, 1995 and June 30, 1996.  Study authors found the risk of revision was approximately two percent per year for the first 18 months post surgery and then approximately one percent per year for the remainder of the 12 year follow-up.

The risk of revision was higher in men than women and in patients 65-75 vs. patients over 75.  Patients operated on by surgeons who performed fewer than six THRs annually in the Medicare population had a higher risk of revision than those whose surgeons performed more than 12 hip replacements a year.  

"These first national, population-based estimates of the rate of revision following THR over 12 years confirm the risk associated with younger age, male sex and low surgeon volume," explained Dr. Jeffrey Katz, MD, Professor of Medicine and Orthopaedic Surgery at Harvard Medical School, Brigham Women's Hospital, Boston, MA.  "This research underscores the need to choose an experienced surgeon who commonly performs THR.  The research also demonstrates that older THR recipients have a lower number of revisions than younger patients.  Innovations to improve implant durability should be targeted to younger patients."

Hip Revisions in Patients Older than 80?

Orthopaedic surgeons are commonly faced with the decision whether or not to replace a total hip replacement (THR) in patients older than age 80.  After several years of use, the joint may become painful or swollen, due to loosening, wear, or infection. Or the function of the implant may decline, resulting in a limp, stiffness, or instability.

This new study evaluated two groups of patients who underwent revision surgery: 84 patients older than 80 and 241 patients younger than 80.  All revision surgeries were performed between 1996 and 2008 in the Geneva University Hospitals, Geneva, Switzerland.  Both age groups indicated general improvements following surgery.  The study found:

• Patients older than 80 reported substantial clinical improvement and satisfaction.
• In the older group, 84.2 percent reported no or only mild pain compared to 79.8 percent in the younger group.

However more complications and higher mortality rates were seen with patients older than 80:

• Medical complications were significantly more common in the older patient group with 23.8 percent vs. 6.2 percent.
  • Overall, the older group experienced significantly more dislocations in the first year (14.4 percent) as compared to the younger group (6.6 percent). However, this risk was substantially reduced in the recent years with use of specific devices.
  • Postoperative fractures were seen more in the older group with 9.5 percent as compared to 2.5 percent in the younger group.
  • Four patients from the older group died within 90 days of surgery.

"We encourage patients older than 80 to have revision surgery in terms of pain relief and function.  But we also tell them they need very good medical preparation before the operation," said Dr. Anne Lubbeke, MD, DSc, Division of Orthopaedics and Trauma Surgery, Geneva University Hospitals, Geneva, Switzerland.  "Patients should work with their primary physician to obtain a comprehensive checkup. And the anesthesiologist also will help evaluate their risk prior to surgery."

Ceramic-on-Ceramic THR Squeaking: Patient Characteristics

Squeaking is somewhat common in ceramic-on-ceramic THR as it is reported in less than 1 percent to 7 percent of ceramic procedures.  Seventy-four squeaking hips were identified in 2,406 ceramic-on-ceramic THRs performed between June 1997 and December 2008 at the Mater Hospital in Sydney, Australia.  

In this largest-study-to-date, researchers examined ceramic hip squeaking, finding that patients more likely to experience squeaking hips share similar qualities, such as:

• taller (mean height of approximately 5 feet 7 inches compared to 5 feet 6 inches with silent hips);
• heavier (mean weight of 176.8 pounds compared to 168.4 pounds with silent hips); and
• younger seniors (mean age of 60 vs. age 65 with silent hips).

Squeaking hips had a significantly higher range of internal and external rotation following surgery.  Patients with squeaking hips were significantly more active.

A squeaking hip was not associated with a significant difference in patient satisfaction or Harris hip score.  

"Fortunately the majority of this squeaking is benign and has not led to revision or failure in large numbers," commented Dr. William L. Walter, MBBS, PhD, Associate Professor, University of Notre Dame and UNSW at the Mater Hospital in Sydney, Australia.  "Ceramic-on-ceramic hip replacement remains a very successful procedure even with benign squeaking in some patients."

High Performance Hips:  More Durable Implants for Active Patients

Active patients of all ages are currently benefitting from improved functional capacity of current generation total hip replacement.  A teaching seminar presented at the AAOS Annual Meeting details these high performance hips, their advantages and how surgeons are working with patients to implant them.

Dr. Thomas Schmalzried, MD, Medical Director at the Joint Replacement Institute at the Saint Vincent Medical Center in Los Angeles, CA is co-leading the seminar.  He describes the four main characteristics of today's high-performance hips:

1. Durable implant fixation:  With these cementless implants, once the bone has grown into the device, it is unlikely the implant will ever loosen.
2. Improved biomechanics:  There is a wider range of implant shapes and sizes which provide the individual patient better fit and function.
3. Larger diameter bearings provide greater stability:  Increased impingement-free range of motion allows higher function and lower dislocation risk.
4. Lower wear bearing surfaces allow increased longevity:  Bearings with very low wear rates have a reduced risk of osteolysis (wear particles can trigger resorption of bone tissue and can lead to revision surgery).

"The greatest benefit of these higher performance hips for seniors is the improved biomechanics and increased stability," commented Dr. Schmalzried.  "Further, these advances in total hip replacement allow for earlier intervention in patients with hip arthritis.  There is no longer a need to wait so long before having a THR and patients can maintain an active lifestyle."

Details about hip replacements:

• In 2008, there were a total of 277,399 total hip replacements (THR) performed in the United States.  Most patients report increased functional improvement, pain relief and satisfaction.  However, due to wear and tear, approximately 10 percent of implants will fail and require revision to remove the old implants and replace them with new components.