Threaded cup in total hip arthroplasty: a systematic review of long-term survivorship.

purposeThreaded cups in total hip arthroplasty (THA) have been introduced to overcome the complications associated with the cemented cups in use until then. Their structure allowed the cup to be screwed into the acetabulum after careful preparation, achieving strong primary stability. However, the materials available at the time did not provide certainties about the long-term durability of these implants. This systematic review aims to evaluate the long-term results of many threaded cups used over the years, focusing on survivorship, clinical outcomes, and complications. MATERIAL AND

methodsA systematic review was conducted adhering to the PRISMA guidelines. Relevant studies were searched in four databases: PubMed, Scopus, Embase, and Medline. The selected articles were evaluated according to the criteria of levels of evidence. The included studies were analyzed using the MINORS criteria for quality assessment. This paper was registered in the International Prospective Registry of Systematic Reviews (PROSPERO).

resultsThe review identified 28 studies and the reported implants were developed by different manufacturers. The threaded cups had different characteristics, belonging to different generations, but all had a minimum follow-up of at least 10 years, with a wide range in cup survivorship. The most frequent long-term complications were aseptic loosening and polyethylene wear, closely related to the available materials and the design of the implant. The different survivorship among the implants was due to the multiple variables in the implant structure and the post-operative indications reported in the studies.

conclusionThreaded cups were an important milestone in the evolution of implants in hip replacement. Although they have benefited from technological improvements over the past few decades, their use is still burdened by significant complications in the long term, and their shape makes revision more difficult compared to more modern and currently widespread implants that are hemispherical and threadless. Aseptical loosening and liner wear are the two main complications in the follow-up, so it is important to keep following these implants even after a long time and no complaints by the patient.