The use of Dual Mobility cups in primary Total Hip Arthroplasty: a bicentric, retrospective study of 196 implants

Abstract

Background Dual Mobility is based on two concentric joints: a head within a retentive polyethylene liner, which moves freely inside the acetabular cup. This paper aims to present our experience with the use of dual mobility in primary hip replacement, evaluating the patient’s outcome after surgery. Methods We conducted a retrospective bi-centre study, including all patients operated with a dual mobility hip replacement at “Centro Medico de Caracas” (Caracas, Venezuela) and “Guglielmo da Saliceto Hospital” (Piacenza, Italy), between August 2014 and August 2020 (6 years). Dualis® dual mobility cementless cup was used in all surgeries, coupled with different stems. Outcome assessment after hip replacements was determined with the Harris Hip Score at 3 months post surgery., then we registered any complications in the first two postoperative years. Results The total cohort was composed of 196 THAs: 35.4% male, 64.6% female (64.6%), mean age 63.6 years. We used 3 different stems: Korus (Gruppo Bioimpianti S.r.l.) (78.1%), Fin (Gruppo Bioimpianti S.r.l.) (3.1%) and Corail (DePuy Synthes) (18.9%). The femoral head was composed of ceramic (93.9%) or metal (6.1%); the size was always 28 mm. The average Harris Hip Score was 34.3 ± 15.8 (min 4 - max 69) preoperative, and 91.2 ± 6.7 (min 61 - max 100) at 3 months follow-up. The HHS grading was “Poor” in 1.0% cases, “Fair” in 6.1% cases, “Good” in 27.0% cases and “Excellent” in 65.8% cases. The outcome was significantly better in young patients: mean HHS of the 98 younger patients is 95.9 ± 2.8, while that of the 98 older patients is 86.5 ± 6.2 (p value < 0.001). We registered an overall dislocation rate of 0%, while we reported 8 revisions (4.1%), due to periprosthetic fracture (4), aseptic loosening (1, infection (1), component breakage (1) and pain (1). The coupling Dualis-Korus reported a failure rate of 3.3% (5/153), Dualis-Fin 16.7% (1/6) while Dualis-Corail 5.4% (2/37). Conclusion The dual mobility system is an effective solution within primary hip replacement: it reduces wear and loosening forces, increasing joint range and prosthesis stability, with a very low incidence of dislocation. In younger patients, and arthritic ones, even the best results can be expected.