Rule out infection, adverse local tissue reaction during investigation of THA instability
DALLAS — When a hip becomes unstable after total hip arthroplasty, the orthopedic surgeon should investigate it with a history and physical, appropriate imaging and laboratory tests prior to any surgery to remove the hip anteversion or revise the prosthesis, according to a presenter.
In a symposium at the American Hip and Knee Surgeons Annual Meeting about preventing and treating instability after THA moderated by Fares S. Haddad, MCh(Orth), FRCS, R. Michael Meneghini, MD, discussed investigation of early vs. late instability after THA and some treatment considerations.
“Instability after hip replacement, successful treatment of that instability requires three things: adequate evaluation of the causal factors, as Fares outlined; establishing an accurate etiology for that failure; and then treatment directed specifically at that etiology,” Meneghini said.
Late dislocators and patients whose hips dislocate after revision THA present the greatest investigational challenges, he said.
Infection or adverse local tissue reaction may be the cause of some extremely late dislocations, which underscores the need for a physical examination and history, and possibly a laboratory workup that includes erythrocyte sedimentation rate and C-reactive protein tests, according to Meneghini.
“Know the surgical approach that was done. That is obviously important. Understand the hip position when the dislocation occurred. Physical exam: Make sure you understand where the incisions are. Always investigate the abductor strength and integrity. That is critical,” he said.
A CT scan and the Trendelenburg sign can be helpful in these investigations, Meneghini said.
He highly recommended a cross-table lateral radiograph, “not a frog-lateral. A cross-table lateral with plain films is the gold standard to make sure you can evaluate the abduction of the acetabular component,” he said.
Although Meneghini now gets serum cobalt-chromium levels measured in THA dislocators, he emphasized the importance of an adequate, yet basic evaluation.
“We definitely feel strongly that you need to identify the etiology and the causal factor of that instability, and address it surgically,” Meneghini said. – by Susan M. Rapp
Meneghini RM. Symposium III: Prevention and treatment of instability following THA: A case-based symposium—Investigation of the unstable hip. Presented at: American Association of Hip and Knee Surgeons Annual Meeting; Nov. 2-5, 2017; Dallas.
Disclosure: Meneghini reports no relevant financial disclosures.