More unbelievably, it also takes the scientists involved a lot of trigonometrical calculations for determining the safest hip positions. Thanks to Improbable Research for this ‘insightful’ article.
“Relative risk of impingement and joint instability during sexual activities after total hip arthroplasty (THA) has never been objectively investigated. Hip range of motion necessary to perform sexual positions is unknown. A motion capture study with two volunteers was performed. 12 common sexual positions were captured and relevant hip joint kinematics calculated. The recorded data was applied to prosthetic hip 3D models to evaluate impingement and joint instability during motion. To explore the effect of acetabular component positioning, nine acetabular cup positions were tested. Four sexual positions for women requiring intensive flexion (> 95°) caused prosthetic impingements (associated with posterior instability) at 6 cup positions. Bony impingements (associated with anterior instability) occurred during one sexual position for men requiring high degree of external rotation (> 40°) combined with extension and adduction at all cup positions. This study hence indicates that some sexual positions could be potentially at risk after THA, particularly for women.”
Artanim Foundation has the complete publication for this research.
Bonus: there’s even a video for it!