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Objective:To compare the biomechanical differences of dynamic condylar screw (DCS), locking compression plate (LCP) combined with DCS and medial anatomic buttress plate (MABP) combined with DCS in the revision of medial defective intertrochanteric fractures by finite element analysis.Methods:The femoral CT imaging data provided by a healthy adult volunteer were used to reconstruct the solid three-dimensional model of femur by Mimics 21.0 and Geomagics Studio 12. Evans-Jensen II B intertrochanteric fracture was established by Ansys Workbench18.0. The three-dimensional models of proximal femoral nail antirotation (PFNA), DCS, LCP and MABP were reconstructed in Solidworks 2015. The PFNA was assembled with the fracture model, and then the PFNA was removed to establish the postoperative failure model of femoral intertrochanteric fracture and then simulated the fixation in the hip-preserving revision surgery of femoral intertrochanteric fractures: non-medial support reconstruction group (DCS); indirect medial support reconstruction group (DCS+LCP) and partial direct medial support reconstruction group (DCS+MABP). Finally, the forces on the hip joint of 70 kg normal people during standing (700 N), slow walking (1,400 N), brisk walking (1,750 N) and going up and down stairs (2,100 N) were simulated in Abaqus 6.14, the relative displacement and stress peak value of fracture end and stress distribution and stress peak value of internal fixation in different models were recorded.Results:At 700 N axial load, the relative displacement of fracture end fixed by DCS, DCS+LCP and DCS+MABP was 0.28, 0.13 and 0.09 mm; the peak stress of the fracture end was 49.01, 15.29 and 1.35 MPa; the peak stress of internal fixation was 230, 220 and 174 MPa, respectively. At 1,400 N axial load, the relative displacement of the fracture end of the three internal fixation methods was 0.56, 0.24 and 0.16 mm; the peak stress of fracture end was 108.49, 28.96 and 3.12 MPa; the peak stress of internal fixation was 469, 352 and 324 MPa, respectively. At 1,750 N axial load, the relative displacement of the fracture end of the three group was 0.70, 0.30 and 0.20 mm; the peak stress of the fracture end was 139.59, 37.57 and 4.17 MPa; the peak stress of internal fixation was 594, 421 and 393 MPa, respectively. At 2,100 N axial load, the relative displacement of the fracture end of the three internal fixation methods was 0.85, 0.35 and 0.23 mm; the peak stress of the fracture end was 170.05, 46.36 and 5.24 MPa; the peak stress of internal fixation was 724, 504 and 460 MPa, respectively.Conclusion:The partial direct reconstruction of medial support under the neck by DCS+MABP may have better biomechanical properties in the revision of medial defective intertrochanteric fractures.
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Advances in surgical techniques and internal fixation materials have been continuously improving treatment of intertrochanteric fractures, but postoperative failure of internal fixation is inevitable and its causes are still controversial. An advanced age, female and severe osteoporosis are believed to lead to an unstable fracture and a fall more likely, increasing the risk for failure of internal fixation. Unstable intertrochanteric fractures such as comminuted fracture of medial femur, basicervical fracture, reverse intertrochanteric fracture and lateral wall fracture are more likely to lead to internal fixation failure. Non-anatomical reduction, improper insertion point and poor position of a lag screw are also prone to internal fixation failure. Extramedullary fixation for unstable fractures may increase the risk of failure. Long waiting time for surgery, late weight-bearing and infection may also increase the risk of failure. Therefore, it is still crucial for a successful treatment to clarify the specific risk factors for internal fixation failure and make corresponding countermeasures to enhance the success rate of a primary operation. This paper summarizes the risk factors for postoperative failure of internal fixation for intertrochanteric fracture so as to provide guidance for clinical treatment.
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Objective:To compare the anti-rotation stability between different modes of augmentative plating for femoral shaft nonunion after intramedullary nailing.Methods:Fifteen artificial synthetic femurs were used to create models of femoral shaft nonunion with rotational instability after intramedullary nailing. They were randomly divided into 3 groups ( n=5). Control group 1 was fixated with lateral locking compression plate (LCP), control group 2 with anterior LCP, and the experimental group with anterior multi-dimensional cross locking plate (MDC-LP). After fixation, all the groups were subjected to a torsional loading test, with the torsional loading starting from 0 N·m till 10 N·m and a loading speed of 6°/min. The 3 model groups were compared in terms of torsional angle and stiffness. Results:Under the torsion loading, the torsional angles for control group 1, control group 2 and the experimental group were 9.69°±0.34°, 7.15°±0.20° and 1.59°±0.02°, respectively, showing significant differences ( P=0.002); the torsional angle for the experi mental group was significantly smaller than that for control group 1 ( P<0.05). The torsion stiffness for control group 1, control group 2 and the experimental group was respectively 1.02 N·m/° ±0.04 N·m/°, 1.39 N·m/° ± 0.04 N·m/° and 6.16 N·m/° ± 0.06 N·m/°, showing significant differences ( P=14 886.140, P<0.001); there was a significant difference between any 2 groups ( P< 0.05). Conclusions:In the management of femoral shaft nonunion after intramedullary nailing, anterior augmentative plating can provide better anti-torsional stability than lateral augmentative plating, and MDC-LP can also provide better anti-torsional stability than a conventional LCP because it leads to bicortical fixation of the screws.
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BACKGROUND: The medial support nail restored the triangular stable structure of the proximal femur through the reconstruction of the medial femoral support. The early finite element analysis and biomechanics showed that the stability of the nail was better than that of the commonly used proximal femoral nail antirotation, but the specific performance in the model of severe osteoporosis was unknown. OBJECTIVE: To compare the biomechanical differences between medial support nail and proximal femoral nail antirotation in the treatment of severe osteoporotic intertrochanteric fractures without medical support. METHODS: The medial unsupported intertrochanteric fracture model was made of artificial bone with severe osteoporosis. Axial and torsional failure experiments were conducted after the medial support nail and the proximal femoral nail antirotation were respectively fixed, and the axial stiffness and torsional stiffness of the two under axial and torsional loads were recorded. RESULTS AND CONCLUSION: (1) Axial failure experiment showed that the ultimate load yield load and axial stiffness of the medial support nail group were all greater than those of the proximal femoral nail antirotation group, but there was no significant difference between the two groups (P > 0.05). (2) The torsional failure experiment showed that the torsional stiffness of the medial support nail group was higher than that of the proximal femoral nail antirotation group (P > 0.05). (3) The findings confirmed that the mechanical stability of the medial support nail, especially torsion resistance, is better than that of the proximal femoral nail antirotation, which may be a good choice for the treatment of severe osteoporotic intertrochanteric fracture.
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Objective To explore the feasibility and effectiveness of peer-assisted learning (PAL) in the clinical probation teaching of orthopaedics in excellent doctors classes. Methods Forty students in the 2014 excellent doctors class in Inner Mongolia Medical University were selected and randomly divided into the experimental group and the control group. The experimental group adopted the PAL teaching mode, and the control group received the ordinary teaching mode . At the end of the internship , theoretical knowledge and practical skills tests were conducted, and self-evaluation and course evaluation were completed in the form of questionnaires. Results The scores of the experimental group in theoretical knowledge and practical skills were higher than those of the control group, and the differences are statistically significant [theoretical scores (97.2±0.7) vs. (90.2±1.3); practical operation scores (98.5±2.4) vs. (89.2±1.5); case analysis (98.1 ±0.8) vs. (92.3 ±2.8), P<0.05]. Students in the experimental group were generally satisfied with their mastering of the basic theoretical knowledges and clinical practice skills of orthopaedics. Conclusion The application of the PAL model in clinical probation teaching not only stimulates students' enthusiasm for learning, but also enhances their eagerness in self-learning;it helps students master the basic theoretical knowledge and clinical skills better in clinical probation.
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Objective To explore the indication and the functional advantages of the high-flexion posterior stabilized (PS) rotating-platform mobile-bearing (RP-MB) total knee system. Methods A prospective randomized, controlled trial was performed. Osteoarthritis was the indicators for total knee arthroplasty.From Feb. 2009 to Apr. 2009, 75 patients (94 knees) were randomly assigned to to receive either a highflexion PS, RP-MB total knee system(PFC sigma RPF) or a standard one (PFC sigma RP). There were no statistical difference in the baselines, the preoperative scores of the Hospital for Special Surgery (HSS) and the knee range of motion (ROM) of both groups. The functional status were assessed with Hospital for Special Surgery and the ROM of the knee at the postoperative 1, 6, 12, 18 months. The satisfaction rates were assessed at the postoperative 18 months. The radiographic measurements were t assessed at the postoperative 3days and 3, 6, 12, 18 months. Results A total of 70 participants (87 knees) completed the 18-month followup. At the time of the final follow-up, the average Hospital for Special Surgery knee score was 92.4±5.0points in the standard group and 94.7±7.0 points in the high-flex ion group. The difference was not statistically significant(P ＞0.05). The average maximal flexion was 131.9±14 degrees in the high-flexion group and 123.0±15.3 degrees in the standard group. There was a statistical difference. But it was not enough to confirm our hypothesis that the difference should be higher than 10 degrees. Moreover, the satisfaction rate were 100% in both groups, and no statistical significant difference was found. Conclusion No significant differences were found between standard and high-flexion posterior-stabilized rotating-platform mobile-bearing total knee prostheses in terms of clinical outcomes or range of motion.