Background & Aims
We present a case of a painful total knee replacement without obvious cause. 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.
In this case, we performed a PNS trial targeting the inferiormedial genicular nerves. Pain decreased by 90%, indicating a successful trial. After lead removal in office at 1 week, we performed a minimally invasive 4 contact tined lead PNS procedure. Post procedure, activity is as tolerated.
Methods
This is a retrospective case report with follow up of 15 months. All the diagnoses and treatment were performed by a single orthopedic surgeon.
Results
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 15 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 a few hours periodically. 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. The patient states this procedure “has changed my life.”
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
PNS Abstract Bibliography list
[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.