Biomechanical effects of internal fixation with self-lock compression anti-rotation blade for Pauwels type III femoral neck fractures: a comparative finite element analysis.

BACKGROUND: Self-lock compression anti-rotation blade (SCAB) is a novel internal fixation implant for femoral neck fractures (FNF). We conducted this finite element analysis study to evaluate the biomechanical performances of SCAB combined with a cannulated screw for fixation of Pauwels type III FNF. METHODS: Three finite element models of Pauwels type III FNF treated with various internal fixations were established: a: the inverted triangular parallel cannulated screw (3CS) model, b: the biplane double-supported screw fixation (BDSF) model, c: the SCAB combined with a cannulated screw model. Displacement and Von Mises stress of femurs and internal fixations under increasing loads as well as the average stress on fracture surfaces and maximum displacements on the X and Z axis of proximal fracture fragments at maximum load were measured and compared. RESULT: The SCAB-based internal fixation exhibited superior biomechanical performances compared with 3CS and BDSF configurations, as the former resulted in lower parameters including displacement of the femur, Von Mises stress of internal fixation, stress on fracture surfaces as well as X and Z axis displacement of fracture fragments. CONCLUSION: Internal fixation using SCAB combined with a cannulated screw for Pauwels type III FNFs shows enough stability, with satisfied resistance to varus and shearing forces, which may provide a new option for the treatment of FNFs.

Bionic reconstruction of tension trabeculae in short-stem hip arthroplasty: a finite element analysis.

BACKGROUND: Short-stem hip arthroplasty (SHA) is characterized by metaphyseal load transfer that effectively preserves the bone stock, but still suffers from stress shielding in the proximal femur. We designed a tension screw to mimic tension trabeculae in the new bionic collum femoris preserving (BCFP) short stem for bionic reconstruction, aiming to restore the biomechanics of hip joint. METHODS: Native femur finite element model was constructed to investigate the biomechanics of hip joint based on computed tomography (CT) data. The maximum absolute principal stress/strain cloud chart allowed the direction of stress/strain to be assessed. Six BCFP models with different screw angles (5°, 10°, 15°, 20°, 25°, and 30°) and the Corail model were created. The stress/strain distribution and overall stiffness were compared between each of the BCFP and Corail implanted models. RESULTS: The native model visualized the transfer pathways of tensile and compressive stress. The BCFP stems showed significantly higher stress and strain distribution in the greater trochanteric region compared to conventional total hip arthroplasty (THA). In particular, the BCFP-5° stem demonstrated the highest average strain in both medial and lateral regions and the overall stiffness was closest to the intact femur. CONCLUSIONS: Stress transfer pathways of trabecular architecture provide biomechanical insight that serves as the basis for bionic reconstruction. The tension screw improves load transfer pattern in the proximal femur and prevents stress reduction in the greater trochanteric region. The BCFP-5° stem minimizes the stress shielding effect and presents a more bionic mechanical performance.

Outcomes of posterior malleolar fractures with intra-articular impacted fragment.

INTRODUCTION: An intra-articular impacted fragment (IAIF) could lead to articular incongruity and malreduction in ankle fractures with posterior malleolar fractures (PMFs). No studies have been conducted to determine whether the presence of IAIF affects the outcome of ankle fractures with PMF. The aim of our retrospective study was to evaluate the effect of IAIF on postoperative outcomes in PMF and analyze the relationship between area of IAIF and outcomes. MATERIALS AND METHODS: We conducted a retrospective study of patients with a posterior malleolar fractures between June 2012 and January 2019 with a minimum follow-up of 2 years. Results of the Olerud-Molander ankle score (OMAS), EuroQol-5D (EQ-5D) index, EQ-5D visual analog scale (VAS), AOFAS (American orthopedic foot and ankle society ankle-hindfoot scale), visual analog scale (VAS) pain score and overall patient satisfaction scale were recorded. Outcomes of the PMF with IAIF group and PMF without IAIF group were compared. Sub-group analysis was given emphasis on the AIAIF > 40 mm2 group and AIAIF < 40 mm2 group in PMF with IAIF. RESULTS: A total of 128 patients were included in the study, consisting of 86 patients with IAIF and 42 patients without IAIF. Regarding the osteoarthritis grade (> 1, ≤ 1), the differences werestatistically significant between the two groups (P = 0.044). The risk of articular malreduction was higher in the PMF with IAIF group than in the PMF without IAIF group (P = 0.035). Osteoarthritis grade (> 1, ≤ 1) was closely related to articular malreduction (P < 0.001). There were 51 patients in the AIAIF > 40 mm2 group and 35 patients in the AIAIF < 40 mm2 group of 86 patients in PMF with IAIF. There were statistically significant differences in trimalleolar fracture (P = 0.004), malreduction (P = 0.022), osteoarthritis grade (> 1, ≤ 1; P = 0.027), EQ-5D VAS score (P = 0.031), and AOFAS score (P = 0.047) between the subgroups. CONCLUSION: The incidence of IAIF is associated with the area of the posterior malleolar fragment. Articular malreduction can lead to post-traumatic osteoarthritis, while IAIF is an important element for the quality of reduction, which is more likely to lead to articular malreduction. IAIF should be reduced if AIAIF is over 40 mm2. Otherwise, the patient will suffer a poor prognosis and post-traumatic osteoarthritis. Therefore, ankle fractures with PMF should undergo a CT scan preoperatively in order for providers to optimal treatment protocols. LEVEL OF EVIDENCE: Level III.

Does segmental artery occlusion cause intravertebral cleft following osteoporotic vertebral fracture: a prospective magnetic resonance angiography study.

BACKGROUND: The avascular necrosis (AVN) hypothesis of intravertebral cleft (IVC) formation in osteoporotic vertebral fracture (OVCF) has received increasing attention. The aim of this article is to detect whether the segmental artery occlusion causes the IVC following OVCF. METHODS: Between December 2019 and April 2020, 44 OVCF patients with 46 fracture levels were prospectively enrolled and the vertebral segmental arteries were evaluated by magnetic resonance angiography (MRA). The artery conditions were divided into patent, narrow and occluded. The lesion segmental occlusion rate (LSOR) and the total occlusion rate (TOR) were calculated. The association of segmental artery occlusion and IVC formation was assessed. RESULTS: LOSR was 15.34% and TOR was 15.12%. The segmental arteries of the unfractured vertebrae had a higher occlusion rate at thoracolumbar levels than at non-thoracolumbar levels. There was no significant difference between the IVC group and the non-IVC group in the fractured levels artery occlusion rate (20.24 ± 28.08 vs 9.78 ± 19.56, P = 0.156) or the total segmental arteries occlusion rate (13.83 ± 12.04 vs 11.57 ± 9.25, P = 0.476). CONCLUSIONS: In patients with vertebral osteoporotic fracture, segmental artery occlusion is not associated with the development of intravertebral cleft.

Incidence and risk factors of acute kidney injury after femoral neck fracture in elderly patients: a retrospective case-control study.

BACKGROUND: Hip fracture is highly associated with disability and consequently, mortality in the elderly population. Postoperative acute kidney injury (AKI) is not unusual and is associated with considerable morbidity and mortality. We aimed to determine the incidences and potential risk factors for postoperative AKI in elderly patients with femoral neck fracture. METHODS: We retrospectively evaluated patients over 65 years of age who had been subjected to surgery for femoral neck fracture at Peking University People's Hospital from January 2015 to December 2019. Demographic characteristics and potential risk factors were collected. AKI was defined according to the Kidney Disease Improving Global Outcomes Guidelines (KDIGO). RESULTS: A total of 308 elderly patients with femoral neck fracture were included in the study. The overall incidence of postoperative AKI was 12% (37 cases). Through binary logistic regression analysis, adjusted for age, intraoperative blood loss and BMI, we identified that early postoperative albumin levels, hemoglobin changes and intraoperative hypotension are independent risk factors for postoperative AKI. The model considering the three factors can improve accuracy of predicting the possibility of developing AKI. The patients with AKI had a significantly higher mortality of 40.5% than those without AKI (24.0%, p < 0.001) CONCLUSION: The incidence of postoperative AKI in elderly patients with femoral neck fracture was 12%. Independent risk factors for postoperative AKI included hemoglobin changes, early postoperative hypoalbuminemia and intraoperative hypotension. At the same time, postoperative AKI significantly increased mortality in elderly patients with femoral neck fracture. Taking multiple possible factors into consideration can better predict the possibility of elderly patients developing AKI after surgery.

A rare complication of pelvic perforation by an excessive medial slide of the helical blade after treatment of an intertrochanteric fracture with proximal femoral nail anti-rotation: A case report and literature review.

Intertrochanteric fractures have become a severe public health problem in elderly patients. Proximal femoral nail anti-rotation (PFNA) is a commonly used intramedullary fixation device for unstable intertrochanteric fractures. Pelvic perforation by cephalic screw is a rare complication. We reported an 84-year-old female who fell at home and sustained an intertrochanteric fracture. The patient underwent surgery with PFNA as the intramedullary fixation device. Routine postoperative examination revealed medial migration of the helical blade that eventually caused pelvic perforation. We performed a cemented total hip arthroplasty as the savage procedure. At the latest follow-up of 12 months after total hip arthroplasty, the patient had no pain or loosening of the prosthesis in the left hip. Pelvic perforation should be considered when choosing PFNA as the intramedullary fixation device, especially in patients with severe osteoporosis wherein the helical blade can be easily inserted during the operation. The lack of devices to avoid oversliding of the helical blade in PFNA is an unreported cause of this complication and should be considered in such cases.

Morphological analysis of posterior malleolar fractures with intra-articular impacted fragment in computed tomography scans.

BACKGROUND: Intraarticular impacted fragment (IAIF) of posterior malleolar fractures has been reported by a few studies. However its location, morphology, and the correlation of posterior malleolar fractures have not been described in detail. The aim of this study was to describe the morphology of IAIF in posterior malleolar fractures, to analyze the related factors between IAIF and posterior malleolar fragments, and explore the treatment of IAIF. MATERIALS AND METHODS: Between January 2013 and December 2018, 108 consecutive patients with unilateral posterior malleolar fractures were managed in our hospital. Basic demographic and computed tomography (CT) data were collected and classified by Lauge-Hansen, OTA/AO, Haraguchi, and Mason classification. Additional radiographic data, including the length and area of posterior malleolar fragment, IAIF, and stable tibial plafond were measured. The location of IAIF was described, and involvement of the fibular notch and medial malleolus was also observed. Statistics were analyzed based on univariate analysis (Chi-square test, t-test, Mann-Whitney U test, Fisher's test) and Spearman's correlation test. RESULTS: Among the 108 cases of posterior malleolar fractures, 75 (69.4%) were with IAIF and 33 (30.6%) cases were without. There were 74 (68.5%) females and 34 (31.5%) males, and the average age of the patients was 49 years (18-89 years). The average LIFN/(LIFN + LSFN) [length of involving fibular notch/(length of involving fibular + length of stable notch fibular notch)] was 32.9% (11.6-64.9%). The APMF/(APMF + ASTP + AIAIF) [area of posterior malleolar fragment/(area of posterior malleolar fragment + area of IAIF + area of stable tibial plafond)] and AIAIF/APMF (area of IAIF/area of posterior malleolar fragment) were 13.1% (0.8-39.7%) and 52.6% (1.2-235.4%), respectively. Involvement of medial malleolus (fracture line extended to medial malleolus, P = 0.022), involvement of fibular notch (P = 0.021), LIFN/(LIFN + LSFN) (P = 0.037), LMPMF (P = 0.004), and APMF were significantly related to the occurrence of IAIF. CONCLUSION: Our research indicates a high incidence of IAIF in posterior malleolar fractures. All IAIFs were found in posterior malleolar, and the most common location was within the lateral area A. Posterior malleolar fracture lines that extend to medial malleolus or fibular notch herald the incidence of IAIF. LIFN/(LIFN + LSFN), LMPMF and APMF are also associated with the incidence of IAIF. CT scans are useful for posterior malleolar fractures to determine the occurrence of IAIF and make operational plans. Operation approach selection should be based on the morphology of posterior malleolar fragments and the location of IAIF. LEVEL OF EVIDENCE: Level III, retrospective case analysis.

Heparin-induced thrombocytopenia and acute colonic pseudo-obstruction after therapeutic anticoagulation in a very elderly patient with hip fracture: a case report.

BACKGROUND: Hip fractures have become a severe public health problem, especially in very elderly patients. Most of them are treated with low molecular weight heparin as prophylaxis or treatment of venous thromboembolism. Heparin-induced thrombocytopenia is one of the complications induced by low molecular weight heparin, which may cause poor prognosis. However, there is not enough awareness for heparin-induced thrombocytopenia in very elderly trauma patients. CASE PRESENTATION: We report a case of hip fracture with heparin-induced thrombocytopenia in a very elderly patient. The patient developed heparin-induced thrombocytopenia, digestive hemorrhage and acute colonic pseudo-obstruction after the use of low molecular weight heparin, which eventually led to death. CONCLUSIONS: This is the first case report of digestive hemorrhage and acute colonic pseudo-obstruction in heparin-induced thrombocytopenia patients with major trauma. This case highlights the severity of HIT in very elderly patients with hip fractures using low molecular weight heparin, and the need for platelet monitoring in these patients. We indicate that there may be a correlation of pathogenesis between digestive hemorrhage and acute colonic pseudo-obstruction in heparin-induced thrombocytopenia patients.

Risk factors for cement leakage and nomogram for predicting the intradiscal cement leakage after the vertebra augmented surgery.

BACKGROUND: Vertebral augmentation is the first-line treatment for the osteoporosis vertebral compression fractures. Bone cement leakage is the most common complication of this surgery. This study aims to assess the risk factors for different types of cement leakage and provides a nomogram for predicting the cement intradiscal leakage. METHODS: We retrospectively reviewed 268 patients who underwent vertebral augmentation procedure between January 2015 and March 2019. The cement leakage risk factors were evaluated by univariate analysis. Different types of cement leakage risk factors were identified by the stepwise logistic analysis. We provided a nomogram for predicting the cement intradiscal leakage and used the concordance index to assess the prediction ability. RESULTS: A total of 295 levels of vertebrae were included, with a leakage rate of 32.5%. Univariate analysis showed delayed surgery and lower vertebral compression ratio were the independent risk factors of cement leakage. The stepwise logistic analysis revealed percutaneous vertebroplasty was a risk factor in vein cement leakage; delayed surgery, preoperative compression ratio, and upper endplate disruption were in intradiscal cement leakage; age, preoperative fracture severity, and intravertebral vacuum cleft were in perivertebral soft tissue cement leakage; no factor was in spinal canal cement leakage. The nomogram for intradiscal cement leakage had a precise prediction ability with an original concordance index of 0.75. CONCLUSIONS: Delayed surgery and more vertebral compression increase the risk of cement leakage. Different types of cement leakage have different risk factors. We provided a nomogram for precise predicting the intradiscal cement leakage.

WITHDRAWN: Fracture line morphology of greater tuberosity fragments of Neer 3 and 4 part proximal humerus fractures.

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Does isolated greater trochanter implication affect hip abducent strength and functions in intertrochanteric fracture?

BACKGROUND: A fracture in the isolated greater trochanter is an infrequent type of femoral intertrochanteric fracture. The gluteus medius and gluteus minimus are abducent muscle groups with attachments located on the greater trochanter. Thus, a fracture of the greater trochanter could cause avulsion injury of these attachment points and eventually affect the abducent function of the hip joint and cause chronic pain. Despite these prospects, the impact of a greater trochanter fracture on abducent strength and hip joint function have yet to be investigated. METHODS: Patients who were diagnosed with an isolated greater trochanter fracture (via computed tomography scan and X-ray) and underwent conservative treatment from June 2013 to October 2016 were included in the present study. Magnetic resonance imaging (MRI) was used to verify the morbidity of recessive fractures. Patients' Harris Hip Scores were determined at 3 months, 6 months, and 12 months and the abducent strength and range of motion of the hip joint on the injured side were analyzed and compared to those on the healthy side. RESULT: Among 32 patients, there were 7 individuals diagnosed with isolated greater trochanter fractures by MRI, and 25 individuals whose fractures were found to have extended into the intertrochanteric region, wherein the recessive intertrochanteric region fractures had no relationship with patients' age, gender, or weight. After 12 months of conservative treatment, 7 patients still complained of pain in the hip joint. The average Harris Hip Score was 87.84 ± 4.83, and the abducent range of the hip joint on the injured side (42.02 ± 13.93°) was not significantly different from that of the healthy side (46.24 ± 7.93°). The abducent strength of the hip joint of the injured side was 121.32 ± 41.06 N which was significantly lower than that of healthy side (137.44 ± 42.21 N). CONCLUSION: Results from this investigation suggest that an isolated greater trochanter fracture attenuates the abducent strength of the hip joint, which may be related to injuries of the ligaments and muscles around the greater trochanter. The surgical skills and methods of addressing isolated greater trochanter fractures merit further investigation.

Detection of miR-22, miR-140 and Bone Morphogenetic Proteins (BMP)-2 Expression Levels in Synovial Fluid of Osteoarthritis Patients Before and After Arthroscopic Debridement.

BACKGROUND Osteoarthritis (OA) is a degenerative joint disease often present on the surface and edge of the joint and beneath cartilage forming new bone. Arthroscopy had been used for the treatment of knee OA. This study aimed to measure the expression of miR-22, miR-140, and BMP-2 in patients with OA before and after arthroscopy operation. MATERIAL AND METHODS The synovial fluid of 80 patients and 60 healthy volunteers were aspirated using a syringe before OA operation and again six months post-operation in patients with OA. The total RNA was extracted and analyzed by quantitative PCR. RESULTS The level of miR-22 was elevated in the progression of OA. The expression of miR-140 level in the synovial fluid was significantly reduced in the patients with OA and was negatively correlated with OA severity compared to controls. Expression of miR-22 and miR-120 returned to normal levels post-operatively. BMP-2 expression was reduced in patients with OA, and returned to normal levels post-operatively. Bioinformatics analysis showed that miR-22 and miR-140 closely target with 3'-UTR of BMP-2 in different positions. The correlation between BMP-2 and miR-22 was negative. The correlation between BMP-2 and miR-140 was positive. CONCLUSIONS The present study identified a change in miR-22, miR-140, and BMP-2 expression in the synovial fluid of patients with OA before and after arthroscopic debridement. Results provide a novel characterization of the pathogenesis and therefore underlying therapeutic target for OA.

A new anatomic locking plate for the treatment of posterolateral tibial plateau fractures.

BACKGROUND: Posterolateral tibial plateau fractures have become more common, and their treatment is of great importance to knee function. Additionally, there is no available literature detailing specialized anatomic locking plate for tibial plateau fractures. Therefore, the aim of the study was to evaluate the safety and clinical efficacy of an innovative anatomic locking plate for treatment of posterolateral tibial plateau fractures. METHODS: Between March 2014 and January 2016, 12 patients with posterolateral tibial plateau fracture underwent surgery with the anatomic locking plate for the posterolateral tibial plateau via the posterolateral approach. Relevant operational data for clinical evaluation were collected. RESULTS: The mean follow-up time was 26 months, and the mean age was 35 years for 12 patients. The mean interval between the time of injury and the surgery was 6.1 days. Radiological fracture union was evident in all patients at 12 weeks. During surgery, the blood loss ranged from 100 to 300 mL, and the duration ranged from 55 to 90 min. The Tegner-Lysholm functional score ranged from 85 to 97 at the final follow-up. Moreover, the final Rasmussen functional score ranged from 25 to 29, and Rasmussen anatomical score ranged from 13 to 18. CONCLUSIONS: The newly designed anatomic locking plate for the posterolateral tibial plateau provided adequate fixation along the posterolateral tibial plateau. It proved to be safe and effective in a small-sample-size population (12 patients) during a 12- to 34-month follow-up.

Incidence of venous thromboembolism and hemorrhage related safety studies of preoperative anticoagulation therapy in hip fracture patients undergoing surgical treatment: a case-control study.

BACKGROUND: Venous thromboembolism is a common postoperative complication following orthopedic surgeries, with morbid and potentially fatal consequences. Perioperative low-molecular-weight heparin (LMWH) therapy can reduce the incidence of venous thromboembolism, but may also increase the risk of bleeding complications. Current literature reflects the need to balance the improved efficacy of early initiating prophylaxis with increased risk of perioperative bleeding. The purpose of this study was to compare the effectiveness and hemorrhage related safety of preoperative versus postoperative LMWH therapy for prevention of deep venous thrombosis (DVT) and pulmonary embolism (PE) in hip fracture patients. METHODS: We retrospectively evaluated 222 patients who underwent surgical treatment at Peking University People's Hospital between January 2009 and December 2010. Patients were allocated to two groups, receiving either preoperative or postoperative initiation of LMWH therapy for venous thromboembolism prophylaxis. Preoperative anticoagulation therapy was initiated 1-12 days prior to surgery (133 patients), and postoperative anticoagulation therapy was initiated 12 h after completion of surgery (89 patients). The preoperative group was further subdivided into four subgroups according to the time of initiation of therapy: 1-3 days before surgery (group A, 54 patients), 4-6 days before surgery (group B, 57 patients), 7-9 days before surgery (group C, 15 patients), and 10-12 days before surgery (group D, 7 patients). Occurrences of DVT, PE, adverse drug effects, intraoperative and postoperative bleeding were recorded, along with concentrations of preoperative and postoperative hemoglobin and length of hospital stay. The above parameters were compared between groups. RESULTS: Among recipients of preoperative anticoagulation therapy, two patients developed postoperative PE (1.5 %), one patient developed DVT (0.75 %). In the group receiving postoperative initiation of anticoagulation therapy, one patient each developed PE and DVT (1.1 %, 1.1 %). There was no difference in the occurrence of PE and DVT between the two groups (P>0.05, Chi-square tests). We identified the incidences of major bleeding, minor bleeding, and intraspinal hematoma after spinal anesthesia, which were 0 %/0 %, 3.76 %/3.37 %, and 0 %/0 %, respectively in preoperative and postoperative anticoagulation groups. There was no significant difference in the incidence of bleeding complications between patients receiving preoperatively initiated LMWH with patients receiving postoperatively initiated LMWH. Spinal anesthesia was administered to 168 patients, with no cases of postoperative intraspinal hematoma. CONCLUSIONS: Preoperative anticoagulation therapy with LMWH may not increase intraoperative or postoperative blood loss, or the rate of intraspinal hematoma after spinal anesthesia, but also does not significantly reduce the risk of postoperative DVT or PE, compared to postoperative initiation.

[Surgical treatment of internal fixation failure after clavicular fracture operation].

OBJECTIVE: To investigate the surgical treatment results of implant failure after clavicular fracture open reduction and internal fixation (ORIF). METHODS: Fifteen cases from Jan. 2005 to Jan. 2013 were treated surgically according to fracture classification, time of implant failure and implant type. The fracture union, shoulder function and pain were evaluated postoperatively. RESULTS: All the patients had full follow-up for 5 to 101 months (mean: 43.8 months). All the fractures were united well. The constant scores to assess the shoulder function were 82 to 100 (mean: 93.3 in the fracture side) and were 85 to 100 (mean: 96.7 in the uninjured side); statistically significant difference of the constant scores between the two sides was found (P=0.02). Eight cases did not have shoulder pain in the fracture side, while the other 7 cases had mild pain, The visual analogue scale (VAS) scores to evaluate shoulder pain were 1 to 3 in the fracture side, which were statistically different from those in the uninjured side (P=0.03). CONCLUSION: Implant instability causes early implant failure after clavicular fracture ORIF and re-fixation with stable implant is effective. Fracture nonunion leads to late implant failure, and bridging fixation using locking plate associated with bony autograft with iliac crest is a successful method to treat atrophy clavicular nonunion. Surgical treatment can bring good results.

A Novel Internal Fixation Design for the Treatment of AO/OTA-31A3.3 Intertrochanteric Fractures: Finite Element Analysis.

OBJECTIVE: AO/OTA 31-A3.3 intertrochanteric fracture is the most unstable type of intertrochanteric fracture, with a high rate of postoperative complications and implant failure. We have designed a new intramedullary fixation, proximal femoral totally bionic nail (PFTBN), for the treatment of A3.3 intertrochanteric fracture. To test its biomechanical performance, we adopted the method of finite element analysis and compared PFTBN with proximal femoral nail antirotation (PFNA) and proximal femoral bionic nail (PFBN, another internal fixation we previously designed for stable intertrochanteric fractures). METHODS: Mimics, 3-matic, ANSYS, and other software were used to construct a highly precise and realistic 3D digital model of the human femur. An AO/OTA 31-A3.3 intertrochanteric fracture of the femur was constructed according to the 2018 classification of AO/OTA, and then assembled with PFNA, PFBN and PFTBN models, respectively. The stress distribution and displacement distribution of the three groups of constructs were tested under three times the body weight load and one-foot standing configuration. RESULTS: In terms of maximum stress and maximum displacement, the PFTBN group outperforms the PFBN group, and the PFBN group, in turn, surpasses the PFNA group. The maximum stress of PFTBN group was 408.5 Mpa, that of PFBN group was 525.4 MPa, and that of PFNA group was 764.3 Mpa. Comparatively, the maximum stress in the PFTBN group was reduced by 46.6% when contrasted with the PFNA group. Moreover, the stress dispersion within the PFTBN group was more evenly distributed than PFNA group. Regarding maximum displacement, the PFTBN group displayed the least displacement at 5.15 mm, followed by the PFBN group at 7.32 mm, and the PFNA group at 7.73 mm. Notably, the maximum displacement of the PFTBN group was 33.4% less than that observed in the PFNA group. Additionally, the relative displacement between the fragment and implant at the tip of pressure screw or helical blade was 0.22 mm in the PFTBN group, 0.34 mm in the PFBN group, and substantially higher 0.51 mm in the PFNA group. CONCLUSION: The "lever-reconstruction-balance" theory provides a new perspective for us to understand the mechanical conduction of the proximal femur. Compared with PFNA, in treating A3.3 intertrochanteric fractures PFTBN can better reconstruct the function of lateral wall, restore physiological mechanical conduction, increase postoperative stability, and finally reduce the risk of postoperative cut-out and implant failure. It might be a better alternative for the treatment of A3.3 intertrochanteric fracture.

[Effect of cement implantation and pressor agents in hip replacement on blood pressure].

OBJECTIVE: To discuss the change of blood pressure involved by pressor agents after the implantation of cement in hip replacement. METHODS: A total of 172 cases of femoral neck fracture underwent hip replacement in Department of Orthopedics and Trauma, Peking University People's Hospital between July 2008 and July 2013 were involved in this retrospective study. The blood pressure and usage of pressor agents were recorded before and after bone cement implantation. The data of blood pressure and usage of agents were collected according to anesthesia records. All the cases were divided into four groups by the application of pressor agents: Free of using agent group (Free-agent group), agents used before implantation of cement group (Pre-agent group), agents used after implantation of cement group (Post-agent group) and agent used before & after implantation of cement group (Pre and Post-agent group). Further statistic analysis was then performed. RESULTS: Free-agent group's mean systolic blood pressure decreased for (4.0 ± 10.3) mmHg. The decreasing was significant (t=3.660, P=0.000). Free-agent group's mean diastolic blood pressure decreased (1.3 ± 7.5) mmHg. The decreasing was not significant (t=2.286, P=0.149). Pre-agent group's mean systolic blood pressure decreased for (0.5 ± 20.2) mmHg. The decreasing was not significant (t=0.114, P=0.911). Pre-agent group's mean diastolic blood pressure increased (0.7 ± 10.2) mmHg. The increasing was not significant (t=-0.316, P=0.756). Post-agent group's mean systolic blood pressure decreased for (6.9 ± 15.0) mmHg. The decreasing was significant (t=3.195, P=0.002). Post-agent group's mean diastolic blood pressure decreased (3.6 ± 7.4) mmHg. The decreasing was significant (t=3.407,P=0.001). Pre & Post-agent group's mean systolic blood pressure decreased for (5.0 ± 12.2) mmHg. The decreasing was not significant (t=1.667, P=0.115). Pre & Post-agent group's mean diastolic blood pressure increased (1.3 ± 8.5) mmHg. The increasing was not significant (t=-0.656, P=0.521). CONCLUSION: Implantation of cement in hip replacement surgery causes blood pressure decreasing. The application of pressor agents before cement implantation can stabilize blood presure and shorten the period of hypotension.

[Minimal invasive internal fixation with U-shaped break-off pedicle screws for treatent of thoracolumbar fractures].

OBJECTIVE: To investigate the clinical outcome of minimal invasive internal fixation with U-shaped break-off pedicle screws through paraspinal muscle sparing approach to treat thoracolumbar fractures, and to discuss its advantages. METHODS: From August 2010 to June 2012, we had 40 thoracolumber fractures patients (27 males and 13 females). Their ages ranged from 22 to 60 years. Of the 40 cases, 4 were T11 fractures, 13 T12 fractures ,17 L1 fractures,6 L2 fractures. According to Denis classification,all of them were burst fractures, with vertebral canal compromise less than 1/3. According to AO classification they were type A or type B1 injuries. All the cases had no nerve injury. The patients were randomly divided into two groups. With Group A (20 cases) we took the method of minimal invasive internal fixation with U-shaped break-off pedicle screws to fix one level above and below the injured vertebra through the parespinal muscle sparing approach. With Group B (20 cases), we took the traditional posterior midline approach and open procedure. Then we compared the two groups by operation time, blood loss, drainage, Visual Analogue Scales and X-ray exposure. RESULTS: Minimal invasive group had obvious advatages in operation time, bleeding control and early pain relief of post-operation. The X-ray exposure and long-term follow-up outcome were almost the same. CONCLUSION: Through paraspinal muscle sparing approach minimal invasive internal fixtation with U-shaped break-off pedicle screws to treat thoracolumber has more advantages than traditional procedure in blood control and quick recovery. The method needs no special instruments and don't increase X-ray exposure.

[Surgical treatment of deltoid ligament injury associated with ankle fractures].

OBJECTIVE: To observe the clinical outcome after the surgical treatment of the deltoid ligament injury associated with ankle fractures. METHODS: From January 2005 to December 2009, 16 deltoid ligament ruptures associated with ankle fractures were repaired. According to the AO/OTA system, 2 cases belonged to fracture A, 8 to B, and 6 to C. Radiographs, American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scores and visual analogue scale (VAS) were used for the outcome measurements. RESULTS: The 16 patients were followed up for 30 to 84 months,with the mean follow-up of 47 months. All wounds healed at the first stage. The mean time of bone union was 12.8 weeks (range: 10-14 weeks). The mean AOFAS ankle-hindfoot score in the last follow-up was 93 points (range: 85-100 points). The mean score of VAS was 0.94 points (range: 0-2 points). CONCLUSION: Surgical treatment of ankle fractures associated with deltoid ligament rupture can achieve satisfactory outcomes, but it is important to decide the operation indication.

[Treatment of comminuted clavicle shaft fractures with provisional intra-medullary K-wire fixation and bridging plate internal fixation].

OBJECTIVE: To discuss the operation effect of comminuted clavicle shaft fractures with provisional intramedullary K-wire fixation and bridging plate internal fixation. METHODS: From Mar. 2008 to Jul. 2012, 22 cases of comminuted clavicle shaft fractures was treated with open reduction, and provisional intramedullary K-wire fixation and bridging plate internal fixation. The fracture healing was investigated through X-rays. The 22 cases were followed up to evaluate the function of the affected shoulder with Constant score. RESULTS: Through the follow-up for average 15 months, all the fractures healed and the average healed time was 14.6 weeks. The average Constant score of the affected shoulder was 95.3. There were 13 excellent cases, 7 good cases, and 2 fair cases. The fineness rate was 90.9% (20/22). Soft tissue problem resulting from plate tilting occurred in 2 cases. At last, they accepted second operation to remove the implant. CONCLUSION: Applying provisional intramedullary K-wire fixation and bridging plate internal fixation in comminuted clavicle shaft fractures, makes procedure simple, improves healing rate and decreases the complications.