Purpose: Dislocation after THA is a multifactorial challenge involving patient, surgical and implant variables. The extramedullary features of a hip implant—offset, neck length, height, version, and head/neck ratio—significantly impact the stability of the reconstruction. We report a significant difference in dislocation rate between two different femoral stems.

Methods: Between May, 1998 and October, 2003, 263 primary THAs were performed by a single surgeon, utilizing identical surgical technique. Acetabular fixation was cementless with 3 varieties of cups in 262 hips and cemented in one hip. 141 hips had a single cemented femoral component (C-Stem, DePuy, Warsaw, Indiana), and 122 hips had a single cementless design (S-ROM, DePuy, Warsaw, Indiana).

Results: Diagnosis, gender, and side were similar between the groups. Mean age of the cemented group was 68.9 years(R 33 to 92) and of the cementless group was 51.9 years (R 19 to 79). The 3 acetabular designs were equally distributed between groups. All hips were implanted with 28 mm heads. There were 12/141 (8.5%) dislocations in the cemented group, and 3/122 (2.5%) dislocations in the cementless group (p < 0.10).

Conclusions: Stability after THA is affected by design features of a femoral implant, including height, neck length, offset, and version. The use of a single stem in all patients may not adequately address individual biomechanic variability. Careful preoperative templating, and the availability of multiple stem designs within a single fixation philosophy, may facilitate matching of extramedullary features to an individual patient’s anatomy in order to optimize postoperative hip stability.

While cemented THA has been considered the gold-standard, cementless THA has become a common and even preferred approach for younger individuals and those with acceptable bone stock. Which technology provides superior results and in which patients, however, remains controversial, and has not been systematically studied.

The literature suggests that well-fixed cementless prostheses, and even composite beam cemented prostheses cause stress shielding and progressive osteopenia in the surrounding bone. This compromises and complicates subsequent surgery, particularly in young patients who are at risk for multiple revisions, and may increase the risk of periprosthetic fracture, component failure, and aseptic loosening.

In contrast, polished tapered stems, by behaving according to a taper-slip philosophy, favorably load bone, converting shear stress into radially directed hoop stresses, through the medium of the surrounding visco-elastic cement and its resulting ability to creep.

The C-Stem, (DePuy, Warsaw, Indiana, USA) a cemented triple tapered polished stem is the only stem with published data demonstrating positive remodeling of bone in as many as 20% of patients, and preservation of the critical proximal medial calcar bone. Additional anectdotal reports confirm these results.

The long-term results of cemented stems, which necessarily involve the surviving youngerst cohort in any series, are outstanding. The tapered polished stem technology may improve these historical results, and, by limiting periprosthetic stress shielding and osteopenia, may revolutionize the application of cemented THA in younger patients for whom preservation of bone stock through favorable bone loading is so critical to sustained success of the primary and subsequent revision surgeries.