Risk assessment of aviators with a total hip arthroplasty ========================================================= * Max Talbot * M Gear * J Young * D Milner * A Bunting * A Bozzo * Hip * AVIATION MEDICINE * ORTHOPAEDIC & TRAUMA SURGERY Military pilots occasionally return to flight status following a total hip arthroplasty (THA), but a structured approach to evaluate the operational risk associated with this condition has not been established.1 2 All-cause revision rates provided by national arthroplasty registries are not good indicators of operational risk. For example, aseptic loosening does not present an acute threat to flight operations. We propose a novel approach to evaluate the operational risk of aircrew with a THA. Periprosthetic fractures and hip dislocations are the main causes of operational risk for aircrew with a THA. Until recently, their incidence was difficult to predict but nomograms now allow individualised forecasts for the first 5 years after the index procedure.3 4 The projected injury rates can be combined with aviation risk matrices to evaluate individual aircrew.5 Synthetic cases will illustrate our approach and highlight that superficially similar aircrew can have widely different levels of operational risk. Take, for instance, two healthy 50-year-old female maritime helicopter pilots who require a THA. Both have a BMI of 25 and normal bone mineral density. Pilot A has primary osteoarthritis, but Pilot B has avascular necrosis. Pilot A receives an uncemented THA with a 32 mm ceramic head, a collared stem, and a neutral highly crosslinked polyethylene (XLPE) liner through an anterior approach. Pilot B gets the same implant, but through a posterior approach. We would advise against a return to full duties in the first year after surgery because this period has the highest incidence of complications. In addition, patients need extended rehabilitation to meet military operational fitness standards. Therefore, the rate of injury after the first postoperative year is the most appropriate measure of operational risk. The nomograms allow us to estimate that Pilot A has a 0.3% yearly risk of fracture and dislocation (combined) after the first year, which makes her ‘green’ on the Canadian Armed Forces aeromedical risk matrix (table 1).3 4 In contrast, Pilot B has an estimated 0.8% annual risk of fracture and dislocation, making her ‘yellow’ on the risk matrix (table 2).3 4 The risk to flight safety is probably less than these estimates suggest, as fractures and dislocations are unlikely to occur in the cockpit. However, they could occur during pre-flight activities and compromise the mission. View this table: [Table 1](http://militaryhealth.bmj.com/content/171/1/86/T1) Table 1 The Canadian Armed Forces aeromedical risk matrix risk applied to Pilot A View this table: [Table 2](http://militaryhealth.bmj.com/content/171/1/86/T2) Table 2 The Canadian Armed Forces aeromedical risk matrix risk applied to Pilot B Our approach has limitations. The models underlying these estimates are based on a single large institutional arthroplasty registry and need to be validated on external data sets. In addition, the risks associated with extreme aviation events (eg, ditching) are not captured by the nomograms. Despite these limitations, we believe that the new nomograms are currently the best method to evaluate the risk of acute injury in aircrew with a THA. Artificial intelligence may soon provide even more precise risk estimates by analysing imaging in addition to clinical features. We encourage continued research in this promising field in order to improve personalised risk assessments for aircrew with a THA. ## Ethics statements ### Patient consent for publication Not applicable. ### Ethics approval Not applicable. ## Footnotes * Contributors MT devised the project and wrote the first draft. All authors contributed to analysis and interpretation of data. All authors critically revised the manuscript. All authors approved the final manuscript. * Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors. * Disclaimer This article reflects the personal views of the authors. It does not represent the official policy or position of the Department of National Defence, the Canadian Armed Forces, the Royal Canadian Medical Service, or McGill University Health Centre. AI or AI-assisted technologies were not used in the writing process. * Competing interests This manuscript received no external financial or material support. Unrelated to this manuscript: AB received an MSTS Sarcoma Strong Mentored Research Grant and a CIHR Doctoral Fellowship. MG occasionally works for Transport Canada as an Aviation Medicine Officer. * Provenance and peer review Not commissioned; internally peer reviewed. * Received August 19, 2023. * Accepted September 11, 2023. * © Author(s) (or their employer(s)) 2025. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ Group. [http://creativecommons.org/licenses/by-nc/4.0/](http://creativecommons.org/licenses/by-nc/4.0/) This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: [http://creativecommons.org/licenses/by-nc/4.0/](http://creativecommons.org/licenses/by-nc/4.0/). ## References 1. Clark DA, Mason KT, Belmont P. Incidence and outcomes of total hip arthroplasty among U.S Army aviators. Mil Med 2001;166:132–4. [PubMed](http://militaryhealth.bmj.com/lookup/external-ref?access_num=11272710&link_type=MED&atom=%2Fjramc%2F171%2F1%2F86.atom) 2. Tormes FR, Webster DE. Return to flight status following total hip replacement: a case report. Aviat Space Environ Med 2002;73:709–12. [PubMed](http://militaryhealth.bmj.com/lookup/external-ref?access_num=12137111&link_type=MED&atom=%2Fjramc%2F171%2F1%2F86.atom) 3. Wyles CC, Maradit-Kremers H, Fruth KM, et al. Frank Stinchfield award: creation of a patient-specific total hip Arthroplasty Periprosthetic fracture risk Calculator. J Arthroplasty 2023;38:S2–10. [doi:10.1016/j.arth.2023.03.031](http://dx.doi.org/10.1016/j.arth.2023.03.031) 4. Wyles CC, Maradit-Kremers H, Larson DR, et al. Creation of a total hip Arthroplasty patient-specific dislocation risk Calculator. Journal of Bone and Joint Surgery 2022;104:1068–80. [doi:10.2106/JBJS.21.01171](http://dx.doi.org/10.2106/JBJS.21.01171) 5. Gray G, Bron D, Davenport ED, et al. Assessing Aeromedical risk: a three-dimensional risk matrix approach. Heart 2019;105(Suppl 1):s9–16. [doi:10.1136/heartjnl-2018-313052](http://dx.doi.org/10.1136/heartjnl-2018-313052) [Abstract/FREE Full Text](http://militaryhealth.bmj.com/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6ODoiaGVhcnRqbmwiO3M6NToicmVzaWQiO3M6MTQ6IjEwNS9TdXBwbF8xL3M5IjtzOjQ6ImF0b20iO3M6MjA6Ii9qcmFtYy8xNzEvMS84Ni5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=)