Mattia Loppini12, Umile Giuseppe Longo3 , Emanuele Caldarella4 , Antonello Della Rocca4 , Vincenzo Denaro3 , Guido Grappiolo4
- Hip Diseases and Joint Replacement Surgery Unit, Humanitas Clinical and Research Centre, Via Alessandro Manzoni 56, 20089, Rozzano, Milan, Italy. firstname.lastname@example.org.
- Humanitas University, Via Alessandro Manzoni 113, 20089, Rozzano, Milan, Italy. email@example.com.
- Department of Orthopaedic and Trauma Surgery, Campus Bio-Medico University, Via Alvaro del Portillo 200, 00128, Trigoria, Rome, Italy.
- Hip Diseases and Joint Replacement Surgery Unit, Humanitas Clinical and Research Centre, Via Alessandro Manzoni 56, 20089, Rozzano, Milan, Italy.
Background: The relevance of prosthetic component orientation to prevent dislocation and impingement following total hip arthroplasty (THA) has been widely accepted. We investigated the use of a non-computer-based surgery to address the reciprocal orientation of the acetabular and femoral components.
Methods: In the femur first technique, the cup is positioned relative to the stem. When the definitive antetorsion of femoral component is fixed, the cup is positioned in a compliant anteversion to the stem. Clinical and radiographic assessments were performed before and 3 months after THA. Radiographic assessment was performed in standing position with the EOS 2D/3D radiography system. 3D images were used to preoperative anterior pelvic plane (APP) angle, postoperative acetabular inclination (AI) and anteversion (AA), and postoperative stem antetorsion. Clinical assessment was performed with Harris Hip Score (HHS).
Results: Forty patients (40 hips) underwent primary THA with an average age of 61 years (range, 36-84). Average HHS increased from 43 ± 5 (range, 37-52) preoperatively to 97 ± 6 (range, 86-100) at the last follow-up (P < 0.0001). Average combined anteversion value of cup with liner and stem was 38° ± 9° (range, 12°-55°). Average AI value of cup with liner was 39° ± 6° (range, 30°-55°) in the group with standard stem and 45° ± 7° (range, 39°-58°) in the group with varized stem (P = 0.007). Relationship analysis showed no correlation between the combined anteversion values of the cup with liner and stem with APP angle values (r = 0.26, P = 0.87).
Conclusions: Femur first technique allows the surgeon to achieve a combined anteversion ranging from 25° to 50° with a cup inclination ranging from 30° to 50°. The cup is positioned according to the functional plane of the patient regardless the preoperative pelvic tilt.
Keywords: Acetabular inclination; Arthroplasty; Combined anteversion; Femur first; Hip.