Preoperative digital planning versus postoperative outcomes in total hip arthroplasty using a calcar-guided short stem: frequent valgization can be avoided.

INTRODUCTION: Modern total hip arthroplasty is largely dependent on the successful preservation of hip geometry. Thus, a successful implementation of the preoperative planning is of great importance. The present study evaluates the accuracy of anatomic hip reconstruction predicted by 2D digital planning using a calcar-guided short stem of the newest generation. METHODS: A calcar-guided short stem was implanted in 109 patients in combination with a cementless cup using the modified anterolateral approach. Preoperative digital planning was performed including implant size, caput-collum-diaphyseal angle, offset, and leg length using mediCAD II software. A coordinate system and individual scale factors were implemented. Postoperative outcome was evaluated accordingly and was compared to the planning. RESULTS: Intraoperatively used stem sizes were within one unit of the planned stem sizes. The postoperative stem alignment showed a minor and insignificant (p = 0.159) mean valgization of 0.5° (SD 3.79°) compared to the planned caput-collum-diaphyseal angles. Compared to the planning, mean femoral offset gained 2.18 (SD 4.24) mm, while acetabular offset was reduced by 0.78 (SD 4.36) mm during implantation resulting in an increased global offset of 1.40 (SD 5.51) mm (p = 0.0094). Postoperative femoroacetabular height increased by a mean of 5.00 (SD 5.98) mm (p < 0.0001) compared to preoperative measures. DISCUSSION: Two-dimensional digital preoperative planning in calcar-guided short-stem total hip arthroplasty assures a satisfying implementation of the intended anatomy. Valgization, which has been frequently observed in previous short-stem designs, negatively affecting offset, can be avoided. However, surgeons have to be aware of a possible leg lengthening.

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

INTRODUCTION: The 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 METHODS: 216 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. RESULTS: Postoperative 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. CONCLUSIONS: Valgus 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.

One-stage bilateral versus unilateral short-stem total hip arthroplasty: comparison of migration patterns using "Ein-Bild-Roentgen-Analysis Femoral-Component-Analysis".

PURPOSE: The hypothesis of this study was that femoral implant migration would not differ between simultaneous bilateral or unilateral short-stem THA. METHOD: Implant migration of 202 femoral short-stems (100 unilateral and 102 one-stage bilateral cases) in 151 patients was assessed by "Ein-Bild-Roentgen-Analysis Femoral-Component-Analysis" in a two years follow-up (2.0-3.0 years). Migration patterns of unilateral and simultaneous cases were analysed and compared. RESULTS: There was no difference between the two groups regarding age, body mass index and gender. After two years mean subsidence of all 202 implants was 1.43 mm (-6.5 mm to 2.0 mm). After initial subsidence of 0.37 mm per month within the first six weeks, the mean monthly migration was reduced to 0.02 mm between one and two years post-operative. There was no statistical difference in mean migration between unilateral (1.34 mm) and simultaneous bilateral (1.51 mm) THA (p = 0.33). CONCLUSION: In summary, two years post-operative there was no difference in the amount of mean implant subsidence between unilateral compared to simultaneous bilateral short-stem THA. This suggests that regarding implant fixation simultaneous bilateral short-stem THA is as safe and successful as a solely unilateral intervention.

Influence of patient-related characteristics on early migration in calcar-guided short-stem total hip arthroplasty: a 2-year migration analysis using EBRA-FCA.

BACKGROUND: Short stems have gained popularity in recent years. Because of encouraging clinical results, indications have been expended from young to elderly and obese patients. However, long-term results are lacking. The purpose of this study was to evaluate the influence of gender, age, body weight, body mass index (BMI), and offset version on short-stem migration in correlation to the clinical outcome. METHODS: The implant migration of 202 metaphyseal-anchoring, calcar-guided short stems in 151 patients was assessed by "Einzel-Bild-Roentgen-Analyse" femoral component analysis (EBRA-FCA, femoral component analysis) in a 2-year follow-up. Full weight bearing was allowed directly after surgery. Patients were divided into groups regarding gender, age, body weight, BMI, and offset version. The Harris hip score (HHS) and satisfaction on visual analogue scale (VAS) were analyzed. RESULTS: After 2 years, mean axial subsidence of all 202 implants was 1.43 mm (standard deviation, SD 1.45 mm). A continuous reduction of initially pronounced subsidence over time could be observed. None of the stems had to be revised. Statistically significant increased rates of subsidence were seen in male (1.68 mm; SD 1.56 mm; p = 0.005) and heavy patients (1.54 mm; SD 1.48 mm; p = 0.022). No differences in implant migration were found regarding age, BMI, and different offset versions. HHS improved markedly from 45.8 (SD 15.9) to 98.1 (SD 4.7) while satisfaction on VAS improved from 1.8 (SD 2.2) to 9.7 (SD 0.9) after 2 years. CONCLUSIONS: The results suggest a migration pattern with initially pronounced subsidence followed by subsequent stabilization. Male and obese patients show a slightly increased initial subsidence without any signs of sustained micromovement. No correlation was found concerning clinical results and pronounced initial subsidence above the threshold of 1.5 mm. No aseptic loosening or other signs of implant failure were seen within the observation period of 2 years. TRIAL REGISTRATION: German Clinical Trials Register, DRKS00009834.

Reconstruction of femoro-acetabular offsets using a short-stem.

PURPOSE: Despite the fact that new and modern short-stems allow bone sparing and saving of soft-tissue and muscles, we still face the challenge of anatomically reconstructing the femoro-acetabular offset and leg length. Therefore a radiological and clinical analysis of a short-stem reconstruction of the femoro-acetabular offset and leg length was performed. METHODS: Using an antero-lateral approach, the optimys short-stem (Mathys Ltd, Bettlach, Switzerland) was implanted in 114 consecutive patients in combination with a cementless cup (Fitmore, Zimmer, Indiana, USA; vitamys RM Pressfit, Mathys Ltd, Bettlach, Switzerland). Pre- and postoperative X-rays were done in a standardized technique. In order to better analyse and compare X-ray data a special double coordinate system was developed for measuring femoral- and acetabular offset. Harris hip score was assessed before and six weeks after surgery. Visual analogue scale (VAS) satisfaction, leg length difference and the existence of gluteal muscle insufficiency were also examined. RESULTS: Postoperative femoral offset was significantly increased by a mean of 5.8 mm. At the same time cup implantation significantly decreased the acetabular offset by a mean of 3.7 mm, which resulted in an increased combined femoro-acetabular offset of 2.1 mm. Postoperatively, 81.7% of patients presented with equal leg length. The maximum discrepancy was 10 mm. Clinically, there were no signs of gluteal insufficiency. No luxation occurred during hospitalization. The Harris hip score improved from 47.3 before to 90.1 points already at six weeks after surgery while the mean VAS satisfaction was 9.1. CONCLUSION: The analysis showed that loss of femoro-acetabular offset can be reduced with an appropriate stem design. Consequently, a good reconstruction of anatomy and leg length can be achieved. In the early postoperative stage the clinical results are excellent.