Abstract
Introduction
The benefits of femoral head-neck modularity in hip surgery have been recognized for decades. However, reports of head/neck taper fretting & corrosion has led to research being conducted, yet the clinical effect of these processes remains unclear. Whilst femoral head size, material and the characteristics of the taper have been a focus of research, potential contributing variables such as in vivo head-neck assembly technique on the performance of these connections is not clear. We performed an observational study to investigate variation in femoral head-neck taper assembly during surgery, with the initial focus being the number of head impactions.
Methods
From May 2013 to October 2014, nineteen surgeons who specialized in hip surgery from a wide demographic (North America, Europe and Asia) participated in a video review on current surgical practice in total hip arthroplasty (THA). The surgeons were unaware of any specific parameter, including taper assembly, which would subsequently be analyzed. Twenty-seven THA surgeries were reviewed against a specific set of questions relating to factors in the modular femoral head-neck assembly process. The focus of the current study was the number of impaction blows to seat the modular femoral head on the implanted stem.
Results
Variation occurred in the number of observed impactions used to assemble the components with an impaction range from 1 to 11 (Figure 1). The two most favored number of impaction strikes were a single strike (37% of reviewed cases) and three strikes (22% of reviewed cases). Further variability was observed between individual surgeon cases where number of strikes was different in each observed case. This occurred on two occasions with two different surgeons. The impaction number was found to be independent of the side operated on (left or right) and also with the surgeons region of origin. However, a higher proportion of European surgeons favored 1–3 impactions (92% of European cases) compared to their North American (28.5% of North American Cases) and Asian (42.8% of Asian cases) counterparts. The impaction number variation was also independent of the material of the femoral head, with both metal and ceramic heads demonstrating this observed variation (Figure 2).
Discussion
This observational review into the current surgical practice of femoral head assembly has shown that there is clear variation in this aspect of the THR surgery. The number of impactions is not correlated to head material, but may be related to the surgeon's training or local practice environment.
Conclusion
This observational review into the current surgical practice of femoral head assembly has shown a level of variation in the way the modular junction is assembled through impaction. Further investigation into other aspects involved in femoral head assembly is required to understand the potential impact that these surgical practice variations may have on the functional performance of the modular taper junctions in THR.
