Metallosis is the putative medical condition involving deposition and build-up of metal debris in the soft tissues of the body. 
Metallosis has been hypothesized to occur when metallic components in medical implants, specifically joint replacements, abrade against one another. Metallosis has also been observed in some patients either sensitive to the implant or for unknown reasons even in the absence of malpositioned prosthesis. Though rare, metallosis has been observed at an estimated incidence of 5% of metal joint implant patients over the last 40 years. Women may be at slightly higher risk than men. If metallosis occurs, it may involve the hip and knee joints, the shoulder, wrist, , elbow joints,  or spine.  In the spine, the wear debris and resulting inflammatory reaction may result in a mass often referred to as a "metalloma" in medical literature, which may lead to neurological impairment over time.  
The abrasion of metal components may cause metal ions to be solubilized. The hypothesis that the immune system identifies the metal ions as foreign bodies and inflames the area around the debris may be incorrect because of the small size of metal ions may prevent them from becoming haptens.  Poisoning from metallosis is rare, but cobaltism is an established health concern. The involvement of the immune system in this putative condition has also been theorized but has never been proven. 
Purported symptoms of metallosis generally include pain around the site of the implant, pseudotumors (a mass of inflamed cells that resembles a tumor but is actually collected fluids), and a noticeable rash that indicates necrosis.  The damaged and inflamed tissue can also contribute to loosening the implant or medical device. Metallosis can cause dislocation of non-cemented implants as the healthy tissue that would normally hold the implant in place is weakened or destroyed. Metallosis has been demonstrated to cause osteolysis.
Women, those who are small in stature, and the obese are at greater risk for metallosis because their body structure causes more tension on the implant, quickening the abrasion of the metal components and the subsequent build-up of metallic debris.
Physical effects and symptoms
Persons suffering from metallosis can experience any of the following symptoms:
- Extreme pain (even when not moving);
- Swelling and inflammation;
- Loosening of the implant;
- Bone deterioration;
- Aseptic fibrosis, local necrosis;
- Hip replacement failure;
- Metal toxicity from grinding metal components; and
- Necessary subsequent hip replacement revision or surgeries.
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As the grinding components cause metal flakes to shed from the system, the implant wears down. Metallosis results in numerous additional side effects:
- Feelings of malaise;
- Gastrointestinal problems;
- Emotional disturbance;
- Recurring infections;
- Problems in the nervous system (feelings of burning, tingling, or numbness of the extremities); and
- Cobalt poisoning (skin rashes, cardiomyopathy, problems with hearing, sight or cognition, tremors, and hypothyroidism).
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DePuy hip replacement recall
In August 2010, DePuy recalled its hip replacement systems ASR XL Acetabular Hip Replacement System and ASR Hip Resurfacing System due to failure rates and side effects including metallosis. The recalls triggered a large number of lawsuits against DePuy and its parent company Johnson & Johnson upon claims that the companies knew about the dangers of the implants before they went on the market in the United States.
- Tower, Stephen S (2010). "Arthroprosthetic Cobaltism: Neurological and Cardiac Manifestations in Two Patients with Metal-on-Metal Arthroplasty". The Journal of Bone and Joint Surgery. American Volume. 92 (17): 2847–2851. doi:10.2106/JBJS.J.00125. ISSN 0021-9355. PMID 21037026. Retrieved 9 July 2017.
- Romesburg, Jason W; Wasserman, Paul L; Schoppe, Candace H (2010). "Metallosis and Metal-Induced Synovitis Following Total Knee Arthroplasty: Review of Radiographic and CT Findings". Journal of Radiology Case Reports. 4 (9): 7–17. doi:10.3941/jrcr.v4i9.423. ISSN 1943-0922. PMC 3303397. PMID 22470753. Retrieved 9 July 2017.
- Cofield, Robert H. (Oct 1994). "Uncemented Total Shoulder Arthroplasty: A Review". Clinical Orthopaedics and Related Research. 307 (307): 86–93. PMID 7924051. Retrieved 9 July 2017.
- Groot, Diederik; Gosens, Taco; Leeuwen, Niels C.M.v.; Rhee, Marina v.; Teepen, Hans J.L.J.M. (2006). "Wear-Induced Osteolysis and Synovial Swelling in a Patient With a Metal–Polyethylene Wrist Prosthesis". The Journal of Hand Surgery. 31 (10): 1615–1618. doi:10.1016/j.jhsa.2006.09.009. ISSN 0363-5023. PMID 17145381. Retrieved 9 July 2017.
- Kudo, Hiroshi; Iwano, Kunio; Nishino, Junki (1994). "Cementless or hybrid total elbow arthroplasty with titanium-alloy implants". The Journal of Arthroplasty. 9 (3): 269–278. doi:10.1016/0883-5403(94)90081-7. ISSN 0883-5403. Retrieved 9 July 2017.
- Goldenberg Y, Tee JW, Salinas-La Rosa CM, Murphy M (May 2016). "Spinal metallosis: a systematic review". European Spine Journal. 25 (5): 1467–1473. PMID 26733018. Retrieved 23 October 2018.
- Tezer M, Kuzgun U, Hamzaoglu A, Ozturk C, Kabukcuoglu F, Sirvanci M (July 2005). "Intraspinal metalloma resulting in late paraparesis". Archives of Orthopaedic and Trauma Surgery. 125 (6): 417–421. PMID 16034644. Retrieved 23 October 2018.
- Fernandez-Baillo N, Sanchez-Marquez JM, Conde Gallego E, Martin Estaban A (2012). "Intraspinal metalloma causing lumbar stenosis after interbody fusion with cylindrical titanium cages" (PDF). Acta Orthop Belg. 78: 811–814. PMID 23409582. Retrieved 23 October 2018.
- Weissman, B N; Scott, R D; Brick, G W; Corson, J M (1991). "Radiographic detection of metal-induced synovitis as a complication of arthroplasty of the knee". The Journal of Bone and Joint Surgery. 73 (7): 1002–1007. doi:10.2106/00004623-199173070-00006. ISSN 0021-9355. Retrieved 9 July 2017.
- Sathappan, Sathappan S.; Wee, James; Ginat, Daniel; Meere, Patrick (2009). "Massive Wear and Metallosis of an Acetabular Cup System Presenting as Pseudodislocation". Orthopedics. 32 (6): 449–452. doi:10.3928/01477447-20090511-23. ISSN 0147-7447. PMID 19634809. Retrieved 9 July 2017.
- Chang, Jun-Dong; Lee, Sang-Soo; Hur, Mina; Seo, Eun-Min; Chung, Yung-Khee; Lee, Chang-Ju (2005). "Revision Total Hip Arthroplasty in Hip Joints With Metallosis". The Journal of Arthroplasty. 20 (5): 568–573. doi:10.1016/j.arth.2005.04.001. ISSN 0883-5403. PMID 16309990. Retrieved 9 July 2017.
- Metallosis of the Resurfaced Hip, Dr.James Pritchett, MD [Page 8 of PDF]