title: On the permanent hip-stabilizing effect of atmospheric pressure.
abstract: Hip joint dislocations related to total hip arthroplasty (THA) are a common complication especially in the early postoperative course. The surgical approach, the alignment of the prosthetic components, the range of motion and the muscle tone are known factors influencing the risk of dislocation. A further factor that is discussed until today is atmospheric pressure which is not taken into account in the present THA concepts. The aim of this study was to investigate the impact of atmospheric pressure on hip joint stability. Five joint models (Ø 28-44 mm), consisting of THA components were hermetically sealed with a rubber capsule, filled with a defined amount of fluid and exposed to varying ambient pressure. Displacement and pressure sensors were used to record the extent of dislocation related to intraarticular and ambient pressure. In 200 experiments spontaneous dislocations of the different sized joint models were reliably observed once the ambient pressure was lower than 6.0 kPa. Increasing the ambient pressure above 6.0 kPa immediately and persistently reduced the joint models until the ambient pressure was lowered again. Displacement always exceeded half the diameter of the joint model and was independent of gravity effects. This experimental study gives strong evidence that the hip joint is permanently stabilized by atmospheric pressure, confirming the theories of Weber and Weber (1836). On basis of these findings the use of larger prosthetic heads, capsular repair and the deployment of an intracapsular Redon drain are proposed to substantially decrease the risk of dislocation after THA.
authors.affiliation: Department of Orthopedic Surgery, University of Leipzig, Liebigstraße 20, D-04103 Leipzig, Germany. Electronic address: torsten.prietzel@medizin.uni-leipzig.de.
authors.forename: Torsten
authors.initials: T
authors.lastname: Prietzel
authors.affiliation: Institute of Anatomy, University of Leipzig, Liebigstraße 13, D-04103 Leipzig, Germany. Electronic address: niels.hammer@medizin.uni-leipzig.de.
authors.forename: Niels
authors.initials: N
authors.lastname: Hammer
authors.affiliation: Department of Orthopedic Surgery, University of Leipzig, Liebigstraße 20, D-04103 Leipzig, Germany. Electronic address: stefan.schleifenbaum@medizin.uni-leipzig.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schleifenbaum
authors.affiliation: Lausitz University of Applied Sciences, Großenhainer Straße 57, D-01968 Senftenberg, Germany. Electronic address: eric.kassebaum@hs-lausitz.de.
authors.forename: Eric
authors.initials: E
authors.lastname: Kaßebaum
authors.affiliation: Department of Spinal Surgery, Clinical Centre Bad Berka, Robert-Koch-Allee 9, D-99437 Bad Berka, Germany; Department of Orthopedic Surgery, University of Leipzig, Liebigstraße 20, D-04103 Leipzig, Germany. Electronic address: mkamal3000@hotmail.com.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Farag
authors.affiliation: Department of Orthopedic Surgery, University of Leipzig, Liebigstraße 20, D-04103 Leipzig, Germany. Electronic address: salis@medizin.uni-leipzig.de.
authors.forename: Georg
authors.initials: G
authors.lastname: von Salis-Soglio
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D001274:Atmospheric Pressure; D005270:Femur Head / Q000503:physiopathology; D006617:Hip Dislocation / Q000503:physiopathology* / Q000517:prevention & control*; D006621:Hip Joint / Q000502:physiology* / Q000601:surgery*; D006801:Humans; D008953:Models, Anatomic; D011184:Postoperative Period; D016059:Range of Motion, Articular / Q000502:physiology
keywords: Ambient pressure; Dislocation; Hip; Intraarticular pressure; Stability; Total hip arthroplasty