Reverse Hip Replacement System Gains Greater Attention

Instability and dislocation are among the top complications that patients face with total hip replacement and are a priority consideration for orthopedic companies as they design new implant systems. Hip Innovation Technology (HIT) developed the Reverse Hip Replacement System (HRS) to address these issues specifically.

Zafer Termanini, M.D., an orthopedic surgeon, invented the Reverse HRS to maximize the benefits of current total hip replacement systems and provide additional solutions to solve unmet clinical needs. While the company was founded in 2011, the reverse hip system has received more attention in recent years due to published clinical data.

Adolph V. Lombardi Jr., M.D., President of JIS Orthopedics, did a live narration of a recorded surgery in the OrthoDome at the American Academy of Orthopaedic Surgeons Annual Meeting in February. He also shared five-year radiostereometric analysis (RSA) and Patient-Reported Outcome Measures (PROM) data compiled from patients who received a Reverse HRS.

“The presentation was well received,” Dr. Lombardi said. “The audience oohed and aahed and was surprised that technology like this was available.”

HIT’s novel system is a reverse geometry metal-on-polyethylene hip implant designed to improve stability, reduce prosthesis impingement and decrease the risk of dislocation. The Reverse HRS consists of a cementless acetabular component that features a unique central taper into which the ball sits. Unlike traditional hip replacement systems, the ball is placed on a trunnion within the acetabular cup instead of the femoral stem. The polyethylene liner is attached to a femoral cup, which then connects to the femoral stem, as opposed to the polyethylene liner being attached to the acetabular cup.

The Bone & Joint Open journal published clinical data on the Reverse HRS in 2023: “Radiostereometric analysis and clinical outcomes of a novel reverse total hip system at two years.” The study followed 11 women and 11 men with a mean age of 70.6 years at six, 12 and 24 months post-surgery. Results demonstrated that the Reverse HRS delivered strong fixation with a predicted low risk of revision at 10 years and migration below the level of RSA detection for the femoral and acetabular components. Patients surveyed reported high satisfaction, no symptoms consistent with soft-tissue impingement within the articulation and no symptoms associated with adverse reactions to metal debris.

“I’ve seen the RSA data for one year, two years and five years published by our colleagues in Canada,” Dr. Lombardi said. “It shows no significant motion of the femur or acetabulum, and no significant wear. I believe that is the gold standard to talk about regarding socket stability and polyethylene wear, and we have that initial data.”

While some orthopedic experts point to hip replacement systems built with dual mobility features as being a sufficient solution to reduce dislocation, Dr. Lombardi noted that the joint can still separate — something he has not seen with the Reverse HRS. “This is a novel concept that is, from my perspective, virtually non-dislocatable,” Dr. Lombardi said. “Even dual mobility has been shown to dislocate in patients with very complex spinopelvic relationships.”

HIT noted that it believes patients with spinopelvic movement disorders, aberrant variants of native femoral or acetabular version, or other factors that predispose them to implant malpositions may be ideal candidates for the Reverse HRS.

“Dislocation continues to be one of the most common complications of conventional total hip systems and one of the most frequent indications for patients requiring reoperation,” HIT’s CEO George Diamantoni said in a 2022 interview for BONEZONE.

HIT has extensively tested the implant in over 90 standard and unique preclinical experiments to assess the safety and clinical benefits anticipated by the system design. In 2022, the company received FDA Investigational Device Exemption (IDE) approval to conduct a pivotal clinical trial to determine the safety and effectiveness of the Reverse HRS in primary total hip replacement.

Clinical data from the trial will guide HIT’s pathway forward with the novel system. The company is assessing value-creation options in parallel with the trial.

“This concept is looked upon by many with scrutiny because it’s not what the hip looks like,” Dr. Lombardi said. “Surgeons felt the same way when the reverse shoulder was introduced. Now, about 75% of the shoulders done in the United States and 90% worldwide are performed with reverse systems. This leads me to believe that we have something here in the reverse hip.”