• Ola Belfrage, Erik Weber, Martin Sundberg, and Gunnar Flivik.
• Department of Orthopedics, Skåne University Hospital and Clinical Sciences, Lund University, Lund, Sweden. ola.belfrage@med.lu.se.
• Arch Orthop Trauma Surg. 2022 Nov 1; 142 (11): 3489-3496.

IntroductionPrevious bone density studies have generally shown bone resorption around both cemented and uncemented total hip arthroplasty (THA) stems. This is presumed to be due to stress shielding. Short stems have been introduced partly to preserve bone in the proximal femur by a more physiological loading of the bone. The purpose of this study was to evaluate bone remodeling around a short, fully hydroxyapatite-coated titanium stem that comes in a collared and collarless version.Patients And MethodsA prospective cohort of 50 patients included in a study evaluating the Furlong Evolution stem has been followed for 5 years. Examination was done with dual energy X-ray absorptiometry (DXA) postoperatively, at 1, 2 and 5 years. Clinical outcome was followed with radiography and both general and hip specific outcome measures.ResultsThe two versions of the stem behaved similarly regarding bone remodeling. After an initial decrease up to 1 year, bone mineral density (BMD) increased in all Gruen zones up to 2 years and at 5 years bone stock was still preserved compared with postoperatively (net BMD + 1.2% (95% CI - 0.4 to 2.8)). Increase in BMD occurred mainly in the greater trochanter and distally around the stem with a decrease in the calcar area. Both versions showed excellent clinical outcome up to 5 years.ConclusionThis short stem seems to preserve proximal bone stock up to 5 years, exhibiting similar behaviour both with and without a collar.Trial Registration Number And Date Of RegistrationClinicalTrials.gov, (identifier: NCT01894854). July 10, 2013.© 2021. The Author(s).

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