Hip Arthroplasty Analysis

The progresses in surgical and anesthesiologic techniques, the evolution of implant design and bearing surfaces led to the outstanding clinical success of total hip arthroplasty (THA) over recent years. The subsequent increased demand for THA all over the world has progressively expanded the population of eligible patients to younger and more active people, with increased expectations [1,2]. Hip biomechanics restoration was generally perceived as the keystone to obtain a high performing new articulation, and femoral offset (FO) plays a major role in this contest. FO is defined as the perpendicular distance between the center of the femoral head and a line drawn down the femoral shaft[3]. FO is strictly related to the abductor muscles moment
Modular neck stems were therefore introduced to accomplish the goal of precise hip geometry reconstruction. Modularity at the neck stem junction provides undoubted facilities for the hip surgeon, allowing intraoperative offset, version and leg-length adjustment independently of stem size. Modular neck solutions should theoretically improve proper FO restoration, which in turns should determine lower joint reaction forces, better soft-tissue tensioning and lower risk of neck to cup impingement with subsequent implant dislocation[4,9]. Although the effective ability of modular neck prostheses to really reconstruct hip geometry in a clinical setting is still under debate[10–13], the theoretical advantages of a near-normal FO should be the reduction of bearing surfaces wear, implant loosening and dislocation rates. On the other hand, the introduction of an additional modular junction implies a greater risk of implant failure, and several cases of modular neck failures and fretting corrosion at the neck-stem junction have been documented[14–21]. Besides, revision for fractured modular necks can be very troublesome, since the re-use of a damaged trunion should be ideally avoided, and revision of a well-fixed stem is not