Peripheral Nerve Stimulation- A Novel, Minimally Invasive Technique in Treating Painful TKRs- An Orthopedic Surgeon Perspective

Each year, over 700,000 total knee arthroplasties are performed in the United States each year.  Unfortunately, there is a notable rate of dissatisfaction post total knee replacement, with most of the suboptimal results due to continued or chronic pain.  It is believed to occur in up to 15- 30% of total knee patients.^{[1, 2, 3]} The options for a “painful total knee” are traditionally somewhat limited in the absence of known causes such as infection, malalignment, fracture, etc.  In today’s environment of pursuing a continued decline in the use of opioid medications, treatment of a painful total knee replacement with unknown etiology typically consists of long term nonnarcotic medical management, bracing, therapy, and occasional use of intraarticular and periarticular injections.  Revision total knee replacement is also a treatment modality.  Unfortunately, revision total joint replacement for chronic pain often have less than perfect outcomes.  Even with known causes for revision, the 10 year survival rates are between 75-80%, which is significantly lower than a primary total knee replacement.^[4]  We present an alternative treatment option for a painful total knee replacement without known, correctable etiology.

Purpose/Objectives:

We present a single case report of a novel treatment for a painful TKR performed by an orthopedic surgeon.

Method: Case Report

Results:

KG is a 76 yo female who presented 2 years post total knee replacement for left knee osteoarthritis.  The patient noted a routine post operative course without complications.  After a 6 month pain free interval, her pain recurred, worsened by weight bearing activities and at rest.  She had normal labs. Bone scans and CT scans which showed no evidence of loosening, malpositioning, or infection. She came to us for an additional opinion.  Exam revealed exquisite medial sided tenderness, range of motion of 0-115, and a stable knee.  XRs showed an acceptably aligned, well fixed TKR.

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Without a known structural cause, we recommended a peripheral nerve stimulator trial.  We performed a PNS trial targeting the proximal medial tibia, specifically the inferiormedial genicular nerve using fluoroscopy for placement. Her pain decreased by 90% over the next few days, indicating a successful trial.  After removal of the lead in office at 1 week, we performed a minimally invasive 4 contact tined lead PNS procedure.

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Prior to any neuromodulation, the patient describes her pain as a 8-10 on the Visual Analog Scale.  The patient experienced significant pain relief during her trial, in the 90% range.  Her pain has declined from a 5 on the VAS at one month to a 1-2 on the VAS, where it has remained. The patient is currently 4 months post procedure.  She has resumed pain free activities of daily living and has enjoyed a resumption of her desired activities, including walking, shopping, gardening, etc. The patient is using her device 12 hours daily.  She does not decrease her activity level while actively using the PNS device.  Additionally, her compliance is enhanced by the ability to connect her device independently.  She currently requires no medications.  She has avoided the need for a revision total knee arthroplasty.

Conclusions: We presented a single case of an alternative therapy performed by an orthopedic surgeon in a painful total knee arthroplasty with unknown cause. Of the current 700,000 TKRs each year, 15- 30% are still painful. When nonnarcotic treatments are the goal, other methods for pain relief need to be explored. Neuromodulation, specifically, peripheral nerve stimulation can offer a non pharmacologic alternative to traditional methods.

References: [1] Beswick, Andrew David, et al. "What proportion of patients report long-term pain after total hip or knee replacement for osteoarthritis? A systematic review of prospective studies in unselected patients." BMJ open 2.1 (2012): e000435.
[2] Pinto, Patrícia R., et al. "Persistent pain after total knee or hip arthroplasty: differential study of prevalence, nature, and impact." Journal of Pain Research (2013): 691-703.
[3] Wylde, Vikki, et al. "Chronic pain after total knee arthroplasty." EFORT open reviews 3.8 (2018): 461.
[4] Roman, Mihai Dan, et al. "Outcomes in revision total knee arthroplasty." Experimental and Therapeutic Medicine 23.1 (2022): 1-4.
[5] Chitneni, Ahish, et al. "Peripheral nerve stimulation of the saphenous and superior lateral genicular nerves for chronic pain after knee surgery." Orthopedic Reviews 13.2 (2021).
[6] Hasegawa, Masahiro, et al. "Prevalence of persistent pain after total knee arthroplasty and the impact of neuropathic pain." The Journal of Knee Surgery 32.10 (2019): 1020-1023.
[7] Helm, Standiford, et al. "Peripheral nerve stimulation for chronic pain: a systematic review of effectiveness and safety." Pain and Therapy 10 (2021): 985-1002.