Three known NHL players have had the procedure in their cervical spine, most notably Jack Eichel in a decision that stirred controversy in Buffalo.

In mid-June during one of his first formal workouts of the summer, Flyers winger Joel Farabee was warming up with light weights on the bench press when he felt a pinching sensation in his neck area. The 22-year-old Farabee then saw a doctor in the Syracuse, N.Y., area and got some imaging done.

A week and a half later, Farabee underwent artificial disk replacement (ADR) surgery performed by Jon Yoon, a neurosurgeon at Penn Medicine. According to assistant general manager Brent Flahr, Farabee walked out of the surgery and said he felt “really good” afterward.

“That’s an incredible surgery,” Flyers general manager Chuck Fletcher said in June.

But roughly seven months earlier, that same surgery had never been performed on an NHL player, and the first procedure was marked with controversy. Center Jack Eichel sought to treat a herniated disk in his neck with ADR, while his former team, the Buffalo Sabres, demanded that he undergo a more traditional procedure called anterior cervical discectomy and fusion (ACDF). Eventually, the Sabres traded Eichel to the Vegas Golden Knights and he underwent ADR in November 2021.

So, what necessitates ADR, why would the Sabres be weary to allow their player to get it, and how likely is it that Farabee can have an impactful career with the Flyers afterward? The Inquirer spoke to Neel Anand, a professor of orthopedic surgery and director of spine trauma at Cedars-Sinai Spine Center in Los Angeles, to learn more about the procedure.

According to Anand, “life” alone can cause a herniated disk in a person’s spine. A spine is comprised of bones called vertebrae, and between each vertebra are rubbery disks that serve as cushions. A disk herniates when it cracks between two vertebrae, causing its interior gel-like material to leak out through its tougher exterior. Anand likened a disk to a car tire, both of which slowly degenerate over time.

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In some cases, a herniated disk does not result in any symptoms. In others, the injury irritates surrounding nerves and results in neck or back pain and numbness. It can also cause weakness in the arms and legs depending on where the herniated disk is located. In Farabee’s case, the herniated disk was in his cervical region, the first seven bones of the spine (more commonly known as the neck). Some herniated disks can improve with time, but some do not. As a result, those with a herniated disk may opt for surgery to address symptoms.

Removing the disk entirely would cause the spine to collapse, so something must be inserted in its place to stabilize the segment. The gold-standard surgery to remove a degenerative disk is ACDF, which has been around in the U.S. since the 1950s. This procedure removes the herniated disk and replaces it with either a bone graft or a metal device and a plate.

Anand said that ACDF is one of the “best spine procedures” he does, with a 95 to 98% good-to-excellent outcome. ACDF has historically been the most common type of cervical spine surgery in high-level athletes, especially football players, according to the Journal of Neurosurgery. In one study of 27 ACDFs performed on 26 professional athletes between 1982 and 2016, including five NHL players, 80% of them returned to play in an average of 9½ months.

However, of the 15 athletes who had retired by the conclusion of the study, the average career length after ACDF was 3.2 years. (The study did not investigate whether the procedure directly led to retirement after that time.) But regardless of whether a patient is a professional athlete, ACDF can have its shortcomings.

Typically, Anand said the spine is like the links of a chain, comprised of bones that move independently from one another. Each level of the spine is called a segment, which is comprised of two vertebrae and the disk in between. But when a person undergoes an ACDF procedure, that segment is fused and does not move, which can cause stress on other parts of the spine. Anand said it’s “un-physiological to stop a neck that moves a lot.”

“It moves more at the next level,” Anand added. “So you fuse [C4 and C5 vertebrae] or you fuse [C5 and C6 vertebrae], it’s an extra level above or below that moves more to compensate for the overall motion. So you’re stressing the next level out. And so we would get increased rates of what’s called adjacent segment degeneration to the next level.”

In a worst-case scenario, adjacent segment degeneration over time can necessitate a second surgery.

Unlike ACDF, disk replacement does not involve fusion and instead attempts to preserve motion in the affected area of the spine. The procedure replaces the degenerative disk with a metal device that mimics a natural disk. According to the Journal of Neurosurgery, the first artificial cervical device was implanted in 1966 and has gained more interest and development in the United States over the last 15 years.

The U.S. Food and Drug Administration approved the first ADR in the cervical spine in 2007. Through investigational device exemption trials, the FDA has approved eight cervical artificial disks. Although each of those trials was designed to prove noninferiority, according to the Global Spine Journal, practically all of the studies demonstrated some degree of statistical superiority favoring ADR over ACDF.

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The surgery takes 45 minutes to an hour to perform and the patient is typically able to go home on the same day.

“Usually within six weeks, that [disk] starts to incorporate, and it’s pretty good,” Anand said. “Very, very rarely, we see anything happen beyond six weeks.”

However, few long-term studies have been conducted on the activity level of patients after cervical ADR, especially among professional athletes in a collision sport like hockey.

Three known NHL players have had ADR in their cervical spine — Eichel, Chicago Blackhawks forward Tyler Johnson, and now Farabee. Each of the three procedures occurred within seven months of one another, starting with Eichel’s on Nov. 12, 2021.

As the first NHL player to have the procedure, Eichel has been lauded in some areas of the medical community for his fight for patient choice. Eichel returned to action on Feb. 16, played 34 games (14 goals, 11 assists) through the remainder of the season, and averaged 19 minutes, 24 seconds of ice time per game.

Two weeks after Eichel had his surgery, Johnson also underwent artificial disk replacement, eventually returning to play on March 3. Johnson, now 32, played 18 games through the end of the season following his procedure.

Farabee underwent ADR on June 24, and in a press release, the Flyers said he was expected to make a full recovery in three to four months. That timeline checks out, according to Anand.

“You can start exercising almost within two weeks,” Anand said. “But you want to give it that six weeks just to allow ... bone inflammation and all the inflammatory enzymes all settle down in about six weeks. After that, you go into more rehab, more intense focus training, and that’s right at three months.”

Despite the lack of ADR precedent among NHL players, Anand said that Farabee is likely to have a long, healthy career — and more importantly, a healthy life after hockey — following the procedure.

“The only thing that fusion did was hasten the degeneration of the next level, because you restricted the motion that was physiological by fusing or stabilizing someone,” Anand said. “By taking that away and giving him a motion device, we are now seeing that the adjacent segment surgery rate. ... All the trials looked at the amount of patients who had surgery again, and now we’ve got 10-year data, some going to 15. And every single trial, the secondary surgery is significantly less in the artificial disk group than in the fusion group.”