Long-Term Femoral Bone Remodeling After Cemented Hip Arthroplasty With the Müller Straight Stem in the Operated and Nonoperated Femora Justinas Stucinskas, MD,*yz Martin Clauss, MD,* Sarunas Tarasevicius, MD, PhD, y Hans Wingstrand, MD, z and Thomas Ilchmann, MD, PhD* Abstract: We investigated the cortical bone changes in 35 patients with total hip arthroplasty operated on only for osteoarthritis with more than 10 years of follow-up and with nonrevised femoral components and without radiologic signs of loosening. The mean follow-up was 16 ± 5 years. The thicknesses of femoral cortices were measured medially and laterally at 6 levels from the first postoperative and the last follow-up x-rays. A comparison with 10 patients who had a nonoperated contralateral hip was performed. We found a significant decrease in cortical thicknesses in total hip arthroplasty. The cortical thinning was significant at all periprosthetic levels but less expressed distally. Prosthetic femora were associated with greater cortical thinning as compared with the contralateral nonoperated femora, exceeding that caused by natural aging. Keywords: arthroplasty, femoral bone remodeling, cortical thinning. © 2011 Elsevier Inc. All rights reserved. Femoral bone loss in the prosthetic femur might be considered a risk factor for aseptic loosening and an indication for later revision [1-4]. There are different etiologies for femoral bone loss in patients with total hip arthroplasty (THA), that is, osteolysis, stress shielding, and osteopenia. Osteolysis is a known risk factor for loosening and revision surgery, whereas stress shielding or osteopenia is not recognized as indications for revision. Stress shielding and osteope- nia in the prosthetic femoral bone are of multifactorial origin and depend on age, preoperative diagnosis, stem type, stem size, sex, or physical activity [5]. Stress shielding and osteopenia might be misinter- preted as osteolysis due to, sometimes, similar radiologic appearance. Thus, knowledge about femoral remodeling and long-term detailed radiologic analysis are required to recognize and discriminate these changes from osteolysis and to avoid possibly unnec- essary revision surgery. The cemented Müller straight stem is widely used in orthopedic practice, but only few clinical or radiologic results are published [6-8]. The reported Müller straight stem survival for aseptic loosening was 96% after 10 years [9] and 86% after 20 years [6]. “Shape- closed” stem design and related cementing technique are associated with a thin and even an incomplete cement mantle [10-13]. Shape-closed design represents a press-fit fixation of THA femora in the anterior- posterior view with a self-centering effect distally. Thus, it is of interest to note how shape-closed cemented fixation would affect long-term radiologic changes in THA femoral bone. As in THA femora, cortical thinning is observed in the nonoperated femora, too [14], and it has been ques- tioned whether the effect of the implant can be discriminated from age-related changes. Poss et al [14] reported that age-related expansion of the femur and cortical atrophy continue after THA, similar to that reported in natural age–related studies. However, the authors investigated 2 different types of stems in patients with various preoperative diagnoses that might affect their results. We found no information in the literature focusing on radiologic long-term changes in the cortical bone after THA with the same type of cemented stem in osteoarthritic patients and comparing those with the nonoperated contralateral femur. From the *Department of Orthopedic Surgery, Kantonsspital Liestal, Liestal, Switzerland; yDepartment of Orthopedics, Lithuanian University of Health Sciences, Kaunas, Lithuania; and zDepartment of Orthopedics, Lund University and Lund University Hospital, Lund, Sweden. Submitted May 22, 2011; accepted September 21, 2011. The Conflict of Interest statement associated with this article can be found at doi:10.1016/j.arth.2011.09.011. Reprint requests: Justinas Stucinskas, MD, Department of Ortho- pedics, Lithuanian University of Health Sciences, Eiveniu 2, LT-50009 Kaunas, Lithuania. © 2011 Elsevier Inc. All rights reserved. 0883-5403/0000-0000$36.00/0 doi:10.1016/j.arth.2011.09.011 1 The Journal of Arthroplasty Vol. 00 No. 0 2011