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Item type:Publication, Access status: with files , Design of surgical impaction instruments matters(Elsevier, 2025-11-12); ; ; ; Background: Femoral stem impaction in total hip arthroplasty is commonly performed by mallet blows on a metal impactor attached to the stem. Factors including the surgeon, the impactor, and the patient can influence the impaction. A wide range of impactors, varying in design and thus in mass and stiffness, are available. However, little is known about their influence on the force transmission and, consequently, about the proportion of the mallet force that ultimately reaches the implant. This study aimed to investigate the force transmission through the impactor for different impactor designs, while investigating different patient-specific femur-tissue systems in situ and in silico. Methods: The mallet and impactor forces of 9 consecutive blows on seated femoral stems were measured for 2 different approaches on each of 4 cadavers. The mallet-implant force transmission was calculated using a phenomenological model for 2 different impactor designs. Results: The attenuated force in the impactor achieved approximately 65% to 75% of the corresponding mallet peak force, regardless of cadaver or surgical approach. Measuring the force distant from the tip resulted in an overestimation of the transferred forces. Depending on impactor design just 24% to 47% of the applied mallet peak force reached the implant itself. Conclusions: The force transmission for overcritical mallet blows can be regarded as independent from patient- and approach-specific boundary conditions and primarily dependent on the impactor design. Surgeons must be aware of this relationship and exercise caution when using other or novel instruments to prevent intraoperative complications.Publicationtype: Journal Article30 32 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Dynamic response of soft tissue can be disregarded during femoral stem impaction(Elsevier, 2025-04-20); ; ; ; Background: In cementless total hip arthroplasty stems are inserted into the bone by mallet blows. Surgeons are not instructed to adjust the force of their blows to differences among patients especially with regard to weight. Whether this is linked to complications is yet unknown. This study investigated factors that could affect the mechanical behavior of the femur-tissue system. Methods: Four cadavers were subject to two total hip arthroplasties by the same surgeon – one side via a lateral approach and the contralateral side via a direct anterior approach. A mass-spring-damper model was used to replicate the mechanical response of the femur-tissue system of the cadavers and make them comparable. Findings: The mechanical response in terms of mass-spring-damper parameters differed between the approaches (lateral: 16.5 kg, 29.7 N/mm, 467.1 Ns/m; direct anterior: 11.5 kg, 41.7 N/mm, 553.0 Ns/m). Interpretation: Common metal-on-metal mallet blows in surgery are very short and mostly excite high frequencies that are clearly above the natural frequency of the femur-tissue system. Those overcritical force impulses make the stem slide into the femur before the bone can even start moving. Hence, the individual mechanical behavior of the femur-tissue system can be disregarded provided that the force is applied with very short blows. This needs to be considered for any attempt to replace the mallet in the operation theater (e.g. automated surgical impaction tools) or to modify the mallet (e.g. alternative tip material). Furthermore, it may provide guidance on the fixation of femurs in in vitro testing to mimic surgical reality.Publicationtype: Journal Article44 28