This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.
In the absence of infection and aseptic loosening, significant postoperative pain persists in up to 20% of joint-replacement patients. In one study related to this predicament, investigators studied 3 groups of individuals: 1) those without a total joint replacement (TJR) and no self-reported pain, 2) patients with a well-functioning TJR and no self-reported pain (mean implant time of 1.5 years), and 3) patients with a painful TJR (self-reported pain of >8 on a 0 to10 VAS scale; mean implant time of 1.76 years)1.
Peripheral blood mononuclear cells were collected for use in a lymphocyte reactivity assay to detect anti-inflammatory (IL-1ra, IL-10, IL-13 and IL-11) and inflammatory cytokines or receptors (IL-1rII and TNFR1). In general, anti-inflammatory cytokine markers in patients with post-TJR pain were decreased compared to controls and to individuals with no pain following TJR, with IL-10 and IL-13 significantly decreased among painful TJR patients. TNFR1 was significantly elevated in those with painful TJRs, and IL-1rII was modestly elevated. The authors note that treating this “1-2 punch” of elevated proinflammatory cytokines and decreased anti-inflammatory cytokines may require “a complex pattern” of both inhibition of proinflammatory mechanisms as well as anti-inflammatory medications.
In a separate study, investigators used scanning electron microscopy (SEM) to try to determine whether implant corrosion was secondary to inflammatory cellular reactions or to the effects of electrocautery used in near proximity to metallic surfaces2. Twelve knee prostheses taken at necropsy were compared to an off-the-shelf cobalt-chromium knee implant intentionally exposed to Bovie and Aquamantys electrocautery sources. SEM data was collected using an identical method to that of the retrieved implants. Five of the 12 necropsy retrievals showed signs of inflammatory cell-induced corrosion. Compared to the necropsy-retrieved implants, the iron/carbon ratio of the Bovie electrocautery-damaged implant was significantly higher, suggesting that the mechanism by which immune cells corrode implants is different than the mechanism of electrocautery damage.
In a third study, which compared results of lymphocyte transformation testing (LTT) for metal sensitivity with histological and clinical findings in 27 cases of primary total knee arthroplasty (TKA), researchers found that LTT results alone were insufficient for the diagnosis of TKA pain-relief failure due to an immune reaction3. A positive LTT might not indicate that an immune reaction is the cause of pain and stiffness post-TKA.
It will take more research to determine whether there is a connection between surface pitting and chronic knee pain in metal-sensitive persons, whether the elevated macrophage response is an associated risk factor, and whether that is associated with metallic material response.
References
- Lauryn S, Caicedo M, Jacobs J, Hallab NJ. Do TJR Patients with High Self-Reported Pain Levels Exhibit Decreased Serum Anti-inflammatory Cytokine Markers? Abstract 0135 Orthopaedic Research Society 2019
- Sorrels JA, Heise G, Morrow B, Arnholt C, Kurtz S, Mihalko WM. Inflammatory Cell- Induced Corrosion and Electrocautery Damaged TKA Implants. Abstract 0131 Orthopaedic Research Society 2019
- Yang S, Dipane M, Lu CH, Schmalzried TP, McPherson EJ. Lymphocyte Transformation Testing (LTT) in Cases of Pain Following Total Knee Arthroplasty: Little Relationship to Histopathologic Findings and Revision Outcomes. J Bone Joint Surg Am. 2019 Feb 6;101(3):257-264. doi: 10.2106/JBJS.18.00134. PMID: 30730485
