*3.3. Alumina-on-Alumina Total Hip Replacement for Femoral Neck Fracture*

Because internal fixation has a significantly greater failure probability, resulting in more pain for these patients, primary arthroplasty stands out as the best option for displaced Garden 3 and 4 femoral neck fractures (FFN). When a THA is performed, the surgeon

must consider implant dislocation as a possible complication, which is said to be more common after a hip fracture, with the posterior surgical approach, in elderly patients with soft-tissue laxity due to sarcopenia and thus poor muscular strength, and the attempt to regain the full range of motion before the injury [41,42]. Even with heads bigger than 28 and 22.2 mm, the ceramic-on-ceramic connection delivers little friction and wear. We believe that after the use of ceramic-on-ceramic bearings in THA, the risk of dislocations can be influenced because, while the risk of fracture should be higher, it will actually be lower after use of heads larger than 28 mm, as in this series: the prevalence of fibrotic response in the tissues surrounding an implant with a CoC articulation may provide a thicker and more resistant capsule in the long term. The periprosthetic retroacetabular bone should not be regarded as a source of stress shielding: the titanium shell is thought to function as a shock absorber between the high stiffness of the alumina and the likely porotic bone, addressing the problem of socket fixation described when a cup of bulky alumina was cemented into the acetabulum [36]. In Bystrom S et al. [42], the femoral head size was shown to be a significant risk factor for prosthesis luxation in a retrospective study of 42,987 primary operations: 22 mm heads performed as well as or better than 28 mm heads, while 28 mm heads led to revision four times more often than 32 mm heads. According to the Norwegian Arthroplasty Register, femoral head size is a risk factor for total hip luxation, with 28 mm heads leading to revision substantially more frequently than 32 mm heads, and 26 mm heads leading to revision significantly more frequently than 30 mm heads. The preoperative diagnosis, i.e., an FFN, was also a significant determinant in the luxation revision rate.

In Figure 3, the case of a young man who suffered an FFN after a traffic accident (fall from an electric scooter) is documented: a THA with 36 mm AMC-on-AMC articulation was implanted.

**Figure 3.** Male, 42 years old, displaced fracture of his left femoral neck: preoperative AP X-ray of the involved hip (**a**), and immediate postoperative X-ray (**b**) of the AMC-on-AMC THA with a 36 mm head and a stem with a modular neck.

(**a**) (**b**)
