Abstract
The proximal modular neck in total hip arthroplasty is not a new concept, but there has been a recent resurgence in interest with multiple companies offering proximal modularity. Proponents of neck modularity suggest that inherent advantages include improved soft tissue balancing and decreased risk of dislocation, particularly in cases with difficult anatomy. Favorable results have been reported in DDH and other cases with excessive femoral anteversion, for example. There are numerous theoretical and published negative aspects of proximal neck modularity that should be considered. Modular necks can be an additional source of corrosion and fretting, and specific systems have been recalled over such concerns. There are case reports of dissociation and fracture at the junction. Fracture appears to be a significant issue in some systems. Retroversion of the neck to reduce the chance of dislocation is not necessarily benign with respect to implant fixation and stability, with RSA data suggesting caution in the application of retroverted necks. Modular necks are difficult to dissociate when in-vivo, negating the long-term benefit of modular conversion. Finally, proximal neck modularity significantly increases the cost of the implant, without any documented improvement in long-term outcome.
Modular necks offer limited advantages with significant potential downside. On balance of the evidence, the routine use of modular necks in primary total hip arthroplasty is difficult to justify.
