In the pursuit of biological permanence in cementless total hip arthroplasty (THA), the orthopedic industry has relentlessly advanced acetabular cup technology. Over the past decade, there has been a massive clinical migration toward “ultraporous” implant surfaces. Manufactured from advanced titanium or tantalum, these three-dimensional matrices are engineered to provide maximum frictional resistance, locking the cup into the reamed acetabulum to achieve impeccable early mechanical stability.
However, this enhanced friction introduces a frustrating and dangerous intraoperative paradox. The intense “grab” of an ultraporous surface often prematurely arrests the cup’s progression during impaction, making full, perfect seating against the native bone extraordinarily difficult. This friction-induced hang-up routinely leaves an empty void at the direct apex of the acetabulum, known radiographically as a “Zone 2 polar gap”.
