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Inferior Screw Placement Drastically Improves Revision THA Outcomes

In This Article

  • Total hip arthroplasty (THA) is a common procedure
  • The number of revision THAs is expected to increase and is complicated by associated bone loss
  • In revision THA, additional fixation using inferior screw placement can act as a "kickstand" that protects the acetabular component from abduction failure
  • A Massachusetts General Hospital study found that inferior screw placement was safe and effective, reducing acetabular component failure and the need for re-revision by up to 86%
  • Due to these significant findings, Mass General researchers were given the American Association of Hip and Knee Surgeons Surgical Techniques and Technology Award

In a recent study, Chief of the Hip & Knee Replacement Service at Massachusetts General Hospital and Medical Director of the Kaplan Joint Center at Newton-Wellesley Hospital, Hany Bedair, MDand joint replacement surgeon and Director of the Adult Reconstruction Surgery Fellowship at Mass General, Christopher Melnic, MD, and colleagues found that using inferior screw placement in revision total hip arthroplasty (rTHA) can reduce acetabular component failure and the need for re-revision by up to 86%.

"We showed a significant decrease in the revision rate for aseptic loosening of the acetabular components. The hope is that this creates a new standard of care on how to take care of complex revision total hips with associated acetabular bone loss," says Dr. Melnic.

The research team's manuscript won the American Association of Hip and Knee Surgeons (AAHKS) Surgical Techniques and Technology Award in 2023 and will be published in the Journal of Arthroplasty in 2024.

Bone Loss After Revision THA

More than 450,000 hip replacements are performed every year in the United States, and that rate is expected to rise as the U.S. population ages. Though complex, THA has a lot of success, with only about 2% of patients currently requiring revision surgery. But as the overall rate of THA rises, so will the incidence of revision.

A common reason for performing THA revision is to account for a gradual loosening of the implant, which can lead to bone loss. "rTHA is further complicated in the setting of acetabular bone loss," Dr. Melnic says. "Because successful treatment of these complex problems is predicated on achieving a stable construct, revision often necessitates the use of fixation in addition to the usual superior screw placement into the acetabular dome."

One option is the use of inferior screw fixation, which involves screws into the superior pubic ramus and/or the ischium in the inferior part of the pelvis. This inferior screw placement acts like a "kickstand" to protect against abduction failure of the acetabular component.

Study Supports Inferior Screw Fixation

The researchers conducted a study to assess the effectiveness of inferior screw placement during rTHA. They reviewed 250 patients (average age of 64.9 years) with Paprosky type II or III defects who underwent revision for acetabular bone loss between 2001 and 2021 at Mass General Brigham, the University of Pennsylvania, and the Rothman Orthopaedic Institute. Surgeons used inferior screw fixation in 56% of the patients and only superior screw fixation in the remaining patients.

At an average follow-up of 53.4 months, 16 patients (6.4%) had required re-revision for acetabular loosening. The difference between patients with inferior screws versus those with only superior screws was striking: The inferior screw group's re-revision rate was 2.1%, versus 11.8% for those with superior screw fixation alone.

The researchers had hypothesized that inferior screw placement would decrease acetabular failure rates, but the results were much more significant than they had anticipated.

"We're not talking about a 10% reduction. We're not talking about even a 50% reduction. We're talking about an 86% reduction, and that is a drastic difference when you place these screws. This is practice-changing," Dr. Melnic says.

The team plans to follow up with the patient cohort again in two years to see if these rates persist.

Preventing Neurovascular Injury From THA

Despite these remarkable results, Dr. Melnic understands that some orthopedic surgeons may hesitate to implement the new approach.

"Many surgeons are reluctant to use inferior screws in rTHA, given theoretical concerns regarding neurovascular injury of the major blood vessels and nerves that are located closely to where those screws need to be placed," he says. "But in our cohort, we had zero neurovascular injuries."

The surgeons who performed the surgeries in this study are all fellowship-trained members of high-volume centers and comfortable with complex procedures. But Dr. Melnic believes that all orthopedic surgeons can become proficient at inferior screw placement.

Improving Outcomes After Hip Replacement

Dr. Melnic says the number of fellowship-trained specialists seeing a high volume of complex cases at Mass General leaves the institution well-positioned to conduct research to improve outcomes for primary and revision joint replacement surgery.

"Mass General is a large tertiary referral center, so we see many complex joint problems from the local community, New England, and beyond," Dr. Melnic says. "We have a reputation of being able to tackle the most challenging problems and a great research support system, so we are on the leading edge of global efforts to improve the care of patients undergoing THA."

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