OPTAN: A NEW ANATOMICAL ADAPTED STEM SYSTEM FOR CEMENTED AND CEMENTLESS FIXATION.

Abstract

Introduction: The new anatomical adapted stem system OptanTM (Zimmer) is presented, showing the first mid-term-results for cemented and cementless fixation. Its cross-section in the proximal area corresponds with its antetorsion, anteversion and helitorsion, to the 3D-morphology of the proximal femur.

Material and Methods: 313 Optan stems (175 cemented, 148 cementless) were implanted in 306 patients (mean age 62.1 y. (20–74 y.), m/f-ratio 0,8). The clinical and radiological parameters for calculation of Harris Hip Score (HHS), Merle d’Aubigné (MD), WOMAC and periprosthetic bone reaction (Gruen et al.) were recorded. An implant migration analysis using two different biplanar radiographic digital measurement systems (DMA, UMA) was done also.

Results: The clinical results for latest follow up examination (5 and more y.p.o.) for cementless (cemented) Optan are: HHS mean (m) 97.6, standard deviation (SD) 7.32 (m 95.1, SD 9.85), MD m 17.6, SD 1.04 (m 17.1, SD 1.48), WOMAC m 1.44, SD 1.56 (m 1.75, SD 1.62). Cemented implantation shows a stable radiographic follow up regarding full cement mantle without any periprosthetic bone adaptations. The SD for the varus-valgus angle rises proportional to the thickness of the cement layer. Only little flattening of the calcar cortical bone (Z7b) could be seen in both, cemented and cementless Optan 2–3 years p.o.. No stem migration was evident in both fixation principles. No relevant osteolyses and cortical bone hypertrophies could be seen. 12 dislocations (closed reposition), 2 femoral fissures (all while cementless fixation), 2 septic loosenings and 1 aseptic loosening were documented till now. Radiographic results of cementless stem show a low rate (29,1%) of secondary endostal reactive line formation in the distal part of the stem (Z3,4,5) beginning 6–12 month postoperative, especially when drilling of femoral bone canal was done. When the distal part of the stem (Z3,5) was fixed directly to cortical bone little hypertrophy of the cortical bone gets relevant 4–5 years p.o. in a few cases.

Conclusions: Compared with other anatomical stems the cementless Optan shows excellent midterm results. The clinical results of the cemented fixation are not quite so good, this may be related to the older mean age of the patients with cemented stem fixation. Among other things, the development of the Optan-stem had the aim, to make an interoperative change of fixation technique easier. Using the same stem design the decision about the fixation type can be made intraoperatively in the last second.