Trunnions have undergone many changes since modularity was expanded to hip arthroplasty surgery in the 1980s. We investigated variances in trunnion design, materials, and manufacturing processes in addition to what it takes, for the average surgeon, to obtain such information. We designed a product questionnaire intended for the manufacturers to investigate the most important characteristics of currently utilized trunnions. We inquired about size of the cone, angle of engagement, length, and postmanufacturing processing. We carefully reviewed the manufacturer's website, phoned their customer service, and attempted contact with the hip engineering team. Last, we e-mailed the questionnaire to their hip product specialist. A total of eleven companies were contacted. Out of the eleven manufacturers, only five partially answered our questionnaire and the remaining six did not answer at all. A total of 28 primary hip implant systems were reviewed. Six different trunnion designs were identified: Type 1 (<12 mm/<14 mm), articul/eze mini 12/14, eurocone 12/14, V40, 11/13, and 12/14. Six trunnion alloys were available: Ti-alloy (proprietary), Ti-6AI-4V, cobalt-chromium-molybdenum (CoCrMo), Ti-Mo-Zr-Fe, Ti-6AI-7Nb, and high-nitrogen stainless steel. Only 14 out of 28 stems (50 %) had a trunnion dimension of 12 mm/14 mm; however, different types of trunnions were identified as 12/14. Two manufacturers provided trunnion angles. No company provided trunnion length, manufacturing tolerances, or manufacturing processing information. This study revealed minimal information from some of the companies about trunnion design. Improved availability of information about modular junctions in medical devices is recommended.
