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Introduction: Traditional mallet broaching and stem seating in cementless total hip arthroplasty (THA) can result in femoral stem misalignment, potentially reducing implant longevity. This study aimed to compare the pullout strength of cementless THA femoral stems with different cross-sectional designs achieved through the powered impactor method versus the traditional mallet method. Methods: The authors utilized 24 polyurethane foam femurs and two femoral bone preservation stems with different proximal cross-sectional shapes (double taper: ACTIS®, size 5; flat taper: TRI-LOCK®, size 5). A single orthopedic surgeon broached each femur from size 0 to size 5 using either the powered impactor or mallet impaction methods. Broaching time and component implantation times were recorded. A load-to-failure pullout strength test was conducted, and the ultimate pullout load was recorded. Results: The broaching time for the TRI-LOCK® stem showed a statistically significant difference between the two impaction methods (powered: 37±7 seconds, mallet: 75±29 seconds, F[3, 20] = 4.56, p = 0.002), but no statistically significant difference was detected for the ACTIS® stem between the two impaction methods (powered: 47±22 seconds, mallet: 59±9 seconds, F[3, 20] = 4.56, p = 0.304). There was a statistically significant difference in pullout strength between the two impaction groups, and this strength was influenced by the implant cross-sectional shape (ACTIS®: 774±75N versus 679±22N, F(3,20) = 16.38, p = 0.018; TRI-LOCK®: 616±57N versus 859±85N, F(3, 20) = 16.38, p <0.001). Conclusions: The technique used for femoral bone preparation (powered impactor versus mallet) and the cross-sectional design of the cementless femoral stem are crucial factors that affect initial stem stability and operation time.
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Introduction: The specific aim of this retrospective study was to determine whether bone quality has any effect on the complication rates or overall survivorship between helical blades and lag screws in cephalomedullary nails used for intertrochanteric hip fractures. Methods: The authors reviewed clinical charts and radiographic studies of patients between January 2012 and August 2019. We reviewed radiographic images (pre-, intra-, and post-operative) to evaluate fracture fixation type, fracture reduction grade, and post-operative complications. We collected dual energy x-ray absorptiometry scan results (T-score) and serum alkaline phosphatase (ALP) isoenzyme activity values to evaluate patient bone quality. Results: We included 303 cases (helical: 197, screw: 106) in the study. Complications were found in 31 (16%) helical blade cases and 23 (22%) lag screw cases. No statistically significant difference was detected when comparing complication rates with patient bone quality between the two groups. These two groups had similar one-year implant survivorship with respect to T-score, the low ALP level group, and normal ALP level group. The helical blade had higher implant survivorship compared to lag screw in five-year survival rate with respect to osteoporotic group, high ALP level group, and normal ALP level group (osteoporotic: 77% vs 69%, high ALP: 73% vs 67%, normal ALP: 70% vs 64%). Conclusions: Similar complication rates were observed between helical blade and lag screw constructs in cephalomedullary femoral nails when accounting for patient bone quality. However, the helical blade design had a higher five-year survival rate.
RESUMEN
OBJECTIVE: To measure trabecular bone strain changes resulting from three increasing subchondral bone defects in the medial tibial plateau. DESIGN: Cadaveric biomechanical model. SETTING: Contact radiographs were made from coronal sections of human cadaveric proximal tibia under no load and loaded to 400 newtons (N). Digital images made from contact radiographs of unloaded specimens were compared to corresponding digital images of loaded specimens using in-house software that detects trabecular deformation and measure trabecular bone strain. INTERVENTION: Ten specimens were loaded intact and with three increasing circular subchondral bone defects and centered under the subchondral plates in the medial tibial plateau that were 10%, 20%, and 30% of the coronal width of the medial plateau. MAIN OUTCOME MEASURE: Maximum shear strain and minimum principal strain were measured at approximately 2,600 discrete points in the trabecular bone in the medial tibial plateau. RESULTS: Trabecular strain increased most dramatically as defects increased from the medium (20%) to the large (30%) defect. The regions of greatest strain elevation were between the physeal scar and joint line near the medial cortex. Small (10%) and medium (20%) defects resulted in modest strain elevations. CONCLUSIONS: Subchondral defects cause size-dependent elevations in trabecular bone strain in the medial tibial plateau. A size threshold may exist, above which the trabecular bone is subjected to rapidly increasing deformation under load.