Outcome of extensive varus and valgus stem alignment in short-stem THA: clinical and radiological analysis using EBRA-FCA

Abstract

IntroductionThe principle of implanting a calcar-guided short stem consists of an individual alignment alongside the medial calcar providing the ability of reconstructing varus and valgus anatomy in a great variety. However, still, there are broad concerns about the safety of extensive varus and valgus positioning in regard to stability, bony alterations, and periprosthetic fractures.Materials and methods216 total hip arthroplasties using a calcar-guided short stem (optimys, Mathys Ltd.) in 162 patients were included. Depending on postoperative CCD angle, hips were divided into five groups (A–E). Varus- and valgus tilt and axial subsidence were assessed by “Einzel-Bild-Roentgen-Analyse”(EBRA-FCA, femoral component analysis) over a 2-year follow-up. The incidence of stress-shielding and cortical hypertrophy as well as clinical outcome [Harris Hip Score (HHS)] were reported.ResultsPostoperative CCD angles ranged from 117.9° to 145.6° and mean postoperative CCD angles in group A–E were 123.3°, 128.0°, 132.4°, 137.5°, and 142.5°, respectively. After 2 years, the mean varus/valgus tilt was −0.16°, 0.37°, 0.48°, 0.01°, and 0.86°, respectively (p = 0.502). Axial subsidence after 2 years was 1.20, 1.02, 1.44, 1.50, and 2.62 mm, respectively (p = 0.043). No periprosthetic fractures occurred and none of the stems had to be revised. Rates of stress-shielding and cortical hypertrophy as well as HHS showed no significant difference between the groups.ConclusionsValgus alignment results in increased subsidence but does not affect the clinical outcome. There is no difference in stress shielding and cortical hypertrophy between the groups. The authors recommend long term monitoring of valgus aligned stems.

The learning curve in short-stem THA: influence of the surgeon’s experience on intraoperative adjustments due to intraoperative radiography

“…Implantation is done in a “round-the-corner” technique, using individualized levels of osteotomy in order to align the stem in varus- or valgus position, according to the patient’s anatomy [ 4 ]. This results in a broad range of CCD angles to be reconstructed with these types of stems [ 2 , 7 ]. The implantation of a calcar-guided short stem, consequently, can be considered as less standardized but often more individualized compared to diaphyseal anchoring in conventional straight stems.…”

“…Furthermore, due to a pronounced metaphyseal anchoring mechanism of short stems, the achievement of a stable contact to the lateral cortical bone in the diaphysis, in addition to the metaphyseal ring fixation and the cortical support on the calcar, is critical for initial implant stability [ 7 ]. This suggests that the choice of stem size plays a decisive role in achieving primary stability.…”

“…Due to the curved design in calcar-guided short stems, an individual stem positioning is possible in a wide range of different varus and valgus alignments alongside the medial calcar [ 7 ]. However, the implantation technique differs from conventional THA and involves a learning curve.…”

Individualized Stem-positioning in Calcar-guided Short-stem Total Hip Arthroplasty

“…Given a preexisting varus anatomy, a high resection also results in a varus position of the implant, maintaining a large femoral offset. On the other hand, given a preexisting valgus anatomy, a low resection results in a valgus position, causing a small femoral offset 10 ( Figure 1 ; Figure 2 ).…”

Model-based roentgen stereophotogrammetric analysis using elementary geometrical shape models: 10 years results of an uncemented acetabular cup component

“…Gold standard method to assess the in vivo fixation of TJA components presents Roentgen Stereophotogrammetric Analysis (RSA) [ 15 , 16 ]. It is important to monitor TJA fixation within preclinical trials using gold standard methods, since worst case scenarios of clinical TJA failure – likewise the Boneloc cement disaster within the early 1990s – could be avoided [ 17 – 20 ] and the migration pattern of TJA is affected by the implant design and its fixation philosophy [ 21 , 22 ]. Using RSA, early implant migration within the first two postoperative years could be detected, which has been shown to correlate well with later aseptic loosening of femoral stems [ 23 ] and acetabular cups [ 24 , 25 ].…”