St. Jude Medical (NYSE:STJ) advised doctors and patients last week that it’s recalling some of its Eon and Eon Mini pain management implants after hundreds of the neurostimulation devices had to be taken out when their batteries failed too soon or because they overheated while recharging.

The July 26 letters detail problems with St. Jude Medical’s Eon Mini battery welds that led to 214 explantations out of nearly 35,000 implanted devices (that’s about 0.06%). They also explain 325 reports that the Eon Mini and Eon devices overheated during re-charging, with a total of 72 resulting explants and 3 cases in which patients received 1st- or 2nd-degree skin surface burns.

A St. Jude spokeswoman told MassDevice.com in an email that the latest recall notices are updates of prior warnings from May and December of last year.

Sign up to get our free newsletters delivered straight to your inbox

"St. Jude Medical has voluntarily issued updates to 2 previous product advisories related to our rechargeable neurostimulation systems – the Eon, Eon Mini and Brio implantable pulse generators – as part of the company’s ongoing commitment to patient safety and product quality," she wrote.

The recalls have led to at least 1 personal injury lawsuit filed by a patient alleging that her Eon Mini model 3788 was defective and had to be surgically removed when the battery failed after only 6 months.

St. Jude touts the Eon implant as having "market-leading battery capacity and the longest time between recharges" and claims the Eon Mini as "FDA-approved to operate at least 24 hours between recharges at 10 years at high settings," saying that’s "the longest battery life approval in the market and the only approval that provides a statement of time between recharges."

Early Eon Mini battery failure due to supplier’s manufacturing issue

The St. Paul, Minn.-based medical device company said it had received 214 reports as of June 30 that its Eon Mini model 3788 implantable pulse generators "lost the ability to communicate or recharge," due to cracked welds in the batteries, "resulting in loss of pain relief and subsequent explant."

"Prior analysis had indicated that moisture was the cause of weld cracking. However, with the occurrence of additional weld cracks, our investigation has determined that the current weld cracks are not attributed to moisture within the battery," wrote Mark Neal, vice president of quality for St. Jude’s neuromodulation division. "Thorough analysis of the cracked batteries and review of the battery manufacturing processes has identified a need to more frequently maintain and replace certain tools during the internal battery welding process by a St. Jude Medical supplier in order to assure complete alignment between the welding apparatus and the battery. It is important to note that the battery is contained within the hermetically-sealed IPG case and cannot leak electrolyte outside the IPG casing."

St. Jude said it’s taken steps to correct the problem with its battery supplier, Neal added, including "extensive testing of samples of batteries contained in IPGs in products beyond this recalled population" showing that the battery issue has been "mitigated."

"We will continue to investigate and eliminate all possible root causes, test battery lots, and monitor product performance to ensure integrity of this component," he wrote.

The medical device company is recommending that surgeons consult the serial numbers of any Eon Mini implants in their inventory or that have already been implanted. No action is necessary if the implants are from unaffected lots, Neal wrote, but any un-implanted devices on the list should be returned to the company for a free replacement.

Devices that are on the affected inventory list should not be automatically explanted, he wrote, but closely monitored for the duration between battery rechargings and for sudden power loss. St. Jude will provide a free replacement for any Eon Minis that require replacement due to weld failures within the inner battery, Neal wrote.

"The U.S. Food and Drug Administration has been notified of this action," he added. "Please accept our apologies for any inconvenience this issue may cause you or your patients. We will continue to monitor supplier and product performance for opportunities to improve our products, services and instructions for use, in order to continue providing the highest standards of health care instrumentation."

Overheating during recharge

The overheating during recharge occurred in about 0.4% of the Eon devices and 0.5% of the Eon Mini implants, resulting in a 0.1% explant rate for each product, Neal wrote in a separate letter to patients also dated July 26.

"Heat generation during charging is a result of energy dissipation that occurs when an electromagnetic field is used to inductively transfer energy between 2 objects," he wrote. "During a charging session, patients may feel an increase in temperature at the IPG implant site, but should not feel discomfort or pain.

"It should be noted that the stated rate of occurrence refers to the devices associated with the reported complaints. A greater percentage may be affected, as long term rates of heating occurrence for these devices are not known at this time," Neal added.

St. Jude recommends that patients who experience discomfort during recharging stop charging until the discomfort subsides, then adjust the position of the charging antenna. More frequent recharging for shorter durations may also help, Neal wrote, as will not inserting the antenna between the body and a chair or sofa that might trap heat.

If that doesn’t work, "please contact your SJM representative for evaluation," he wrote. "Regulatory authorities, including the U.S. Food & Drug Administration, have been notified of this action.”

The lawsuit

Late last year, Sheryl Cline filed a lawsuit in the U.S. District Court for Northern Georgia after the battery in her Eon Mini model 3788 failed 6 months after implantation, seeking $90,000 in medical expenses, compensatory damages and legal fees.

In June, Judge Amy Totenberg dismissed 1 count in the case, ruling that Cline failed to show that St. Jude broke FDA regulations, but allowed a 2nd breach of contract charge to proceed.

St. Jude Medical argued that the preemption doctrine enshrined by the U.S. Supreme Court in Riegel v Medtronic meant the case should be dismissed because the breach of contract claim parallels FDA rules. But Totenberg ruled that the limited warranty covering the Eon Mini’s battery "falls outside the scope of the ‘effectiveness’ review performed by the FDA," according to court documents.

"As such, this express warranty claim does not require a fact-finder to reach conclusions on the safety or effectiveness of the Model 3788 or its labeling. Therefore, the claim for breach of the warranty at issue here does not ‘relate to the safety or effectiveness of the device,’" Totenberg wrote. "Since this claim involves neither state-established ‘requirements’ nor FDA determinations of safety or effectiveness, it is not preempted by the [Medical Device Act].”

The discovery phase of the case is scheduled to end Nov. 26 this year.