Leg Pain After TKA Using Computer- or Robotic Assisted Navigation? It May be a Pin-Related Fracture

Elizabeth Hofheinz, M.P.H., M.Ed.

There is a rare and mostly uninvestigated issue of periprosthetic fractures through tracking pin sites while using computer-assisted navigation (CAN) and robotic-assisted (RA) surgery in total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA). To tackle this, a multicenter research team undertook a systematic review that included 17 clinical studies.

Their work, “Periprosthetic Fractures Through Tracking Pin Sites Following Computer Navigated and Robotic Total and Unicompartmental Knee Arthroplasty,” appears in the January 2021 edition of The Journal of Bone and Joint Surgery.

Co-author Ahmed Siddiqi, D.O. is an Adult Reconstruction Orthopedic Surgeon at the Orthopedic Institute of Central Jersey and an Assistant Professor at the Hackensack School of Medicine. He told OSN, “One of my junior residents during his trauma rotation treated a patient with a periprosthetic fracture through pin site from a recent navigated TKA procedure. Although this occurrence is very rare, it sparked an interest to see what the current literature reports on this unique complication. This is especially relevant as the number of robotic-assisted and technology-assisted joint replacement continues to increase nationally and globally.”

The researchers looked at 5 case series, 1 cohort study, and 11 case reports involving 29 pin-related fractures. The incidence: from 0.06% to 4.8%. The mean time from index arthroplasty to fracture: 9.5 weeks (range, 0 to 40 weeks). Most fractures occurred in the femoral diaphysis (59%).

The authors wrote, “Nineteen fractures (66%) were displaced and 10 (34%) were nondisplaced or occult. The majority of cases were atraumatic in nature or involved minor trauma and were typically preceded by persistent leg pain. A transcortical pin trajectory, large pin diameter (>4 mm), diaphyseal fixation, multiple placement attempts, and the use of non-self-drilling, non-self-tapping pins were the most commonly reported risk factors for pin-related periprosthetic fractures following CAN or RA TKA.”

“The most important findings were the patient and surgical risk factors associated with pin site fractures,” stated Dr. Siddiqi. “Although the complication is rare, it is important to be cognizant of patient factors that predispose patients to osteopenic bone. It is also important to be meticulous about pin site location (metaphysis) and to ensure the pin is not transcortical or bicortical in the diaphysis.”

Asked about further study, Dr. Siddiqi told OSN: “We are currently pursuing performing a multicenter study to further evaluate the incidence, prevalence, and other risk factors that need to be identified that place certain patients at higher risk for this devastating complication.”

“Although the use of technology-assisted total joint replacement is increasing, complications that are unique to robotic surgery and computer navigation are not benign. A conversation with patients is warranted to discuss the potential complications including pin site fracture. Patients should also be risk stratified before routinely performing technology-assisting knee arthroplasty on all patients.”