Abstract
Between October 2001 and December 2010, 143 patients with developmental dysplasia underwent hip replacement surgery using a conical stem with modular necks (MODULUS) and titanium (Delta PF) and trabecular titanium cups system (Delta TT primary cups) (Lima Corporate, Villanova di San Daniele del Friuli, Italy), with ZTA/ZTA bearing (Ceramtec, Germany). 30 (21.0%) patients had both hips replaced, for a total of 173 implants. Mean age at the time of surgery was 55 years (range 22–81 years).
Dysplasia evaluation was based on the Crowe score (6): 66 (38.1%) hips were classified as 1, 50 (28.9%) as 2, 33 (19.1%) as 3 and 24 (13.9%) as 4.
Mean follow-up was 87 months (range 36–146 months); average Harris Hip Score increased from 42 (range 23–65) preoperatively to 92 (range 76–100) at the last follow-up. Stem revision was required in two cases. Cup revision was necessary in one case, for failed osteointegration.
A postero-lateral approach was used in all cases, with patients lying in a lateral decubitus position. Shortening femoral osteotomy was performed in 5 (2.9%) cases for implant reduction due to excessive tension: oblique osteotomy was employed in 3 cases, using the stem as a fixation device, while subtraction Z-osteotomy with two Dall-Miles cables was used in the other 2 cases. Supra-acetabular bone grafting was performed in 3 cases. In all cases, the cup was implanted at the level of the paleo-acetabulum or in the area between the paleo- and neo-acetabulum.
Head diameters were 28 mm in 54 (31.2%) cases, 32mm in 84 (48.6%) cases and 36mm in 35 (20.2%) cases.
The association of Modulus stem and Delta TT cups showed good long-term clinical and radiographic results, with a Kaplan-Meier survivorship of 98.8% at 12 years (95% CI, 97.1%-100%).
