Effect of changes of femoral offset on abductor and joint reaction forces in total hip arthroplasty
- 501 Downloads
Anatomical reconstruction in total hip arthroplasty (THA) allows for physiological muscle function, good functional outcome and implant longevity. Quantitative data on the effect of a loss or gain of femoral offset (FO) are scarce. The aim of this study was to quantitatively describe the effect of FO changes on abductor moment arms, muscle and joint reactions forces.
THA was virtually performed on 3D models built from preoperative CT scans of 15 patients undergoing THA. Virtual THA was performed with a perfectly anatomical reconstruction, a loss of 20% of FO (−FO), and a gain of 20% of FO (+FO). These models were combined with a generic musculoskeletal model (OpenSim) to predict moment arms, muscle and joint reaction forces during normal gait cycles.
In average, with −FO reconstructions, muscle moment arms decreased, while muscle and hip forces increased significantly (p < 0.001). We observed the opposite with +FO reconstructions. Gluteus medius was more affected than gluteus minimus. −FO had more effect than +FO. A change of 20% of FO induced an average change 8% of abductor moment arms, 16% of their forces, and 6% of the joint reaction force.
To our knowledge, this is the first report providing quantitative data on the effect of FO changes on muscle and joint forces during normal gait. A decrease of FO necessitates an increase of abductor muscle force to maintain normal gait, which in turn increases the joint reaction force. This effect underscores the importance of an accurate reconstruction of the femoral offset.
KeywordsHip Arthroplasty Femoral offset Patient-specific musculoskeletal modeling Muscle Moment arm Joint force
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
The study is based on previously published finite element models, which are derived from CT scans of 15 of our patients. The use of this numeric model has been approved by our IRB.
- 8.Sariali E, Mauprivez R, Khiami F et al (2012) Accuracy of the preoperative planning for cementless total hip arthroplasty. A randomised comparison between three-dimensional computerised planning and conventional templating. Orthop Traumatol Surg Res 98:151–158. doi: 10.1016/j.otsr.2011.09.023 CrossRefPubMedGoogle Scholar
- 17.Sherman MA, Seth A, Delp SL (2013) What is a moment arm? Calculating muscle effectiveness in biomechanical models using generalized coordinates. ASME Pap. (V07BT10A052)Google Scholar
- 27.Reinbolt JA, Seth A, Delp SL (2011) Simulation of human movement: applications using OpenSim. pp 186–198Google Scholar