Biomechanical study of different internal fixations in Pauwels type III femoral neck fracture - A finite elements analysis

ObjectiveTo evaluate biomechanical behavior of different internal fixation methods for the treatment of Pauwels Type III femoral neck fractures.MethodsThree internal fixators were developed to treat Pauwels Type III femoral neck fracture using finite elements: dynamic hip screw (DHS); DHS combined with anti-rotation screw; three cannulated screws in an inverted triangular configuration (ASNIS). Under the same conditions, vertical fracture displacement, and maximum and minimum principal, and Von Mises stresses were evaluated.ResultsThe vertical displacements evaluated were: 5.43 mm, 5.33 mm and 6.22 mm, rotational displacements values were 1.1 mm, 0.4 mm and 1.3 mm; maximum principle stress values obtained for the upper region of the femoral neck were 3.26 hPa, 2.77 hPa, and 4.5 hPa, minimum principal stress values obtained for the inferior region of the femoral neck were −1.97 hPa, −1.8 hPa and t −3.15 hPa; Von Mises peak stress values were 340.0 MPa, 315.5 MPa and 326.1 Mpa, for DHS, DHS with anti-rotation device, and ASNIS, respectively. Conclusion: The DHS combined with anti-rotation screw yielded better results in terms of rotational and vertical displacements, traction and compression distributions on fractures, and Von Mises stress, demonstrating mechanical superiority for Pauwels Type III fracture.     

Clinical and Biomechanical Effects of Femoral Neck Buttress Plate used for Vertical Femoral Neck Fractures

PurposeTo investigate both the biomechanical and clinical effect of an inferomedial femoral neck buttress plate (FNBP) used to augment a sliding hip screw (SHS) and anti-rotational screw (ARS) in the treatment of traumatic vertical femoral neck fractures.MethodsPart 1: Clinical - Retrospective review of patients under age 65 treated with open reduction of a vertical femoral neck fracture. Patients were divided into two groups: Group 1 patients (18 patients) had SHS/ARS fixation augmented with a FNBP, while Group 2 patients (18 patients) had SHS/ARS fixation alone and were matched for age and sex. Demographic data, OTA fracture classification, immediate post-operative and follow-up radiographs were analyzed for quality of reduction, femoral neck shortening (FNS), neck-shaft angle (NSA), avascular necrosis (AVN) and union.Part 2: Biomechanical - Pauwels III femoral neck osteotomy was created in five pairs of cadaveric specimens, then each fracture was reduced and stabilized with a SHS/ARS construct. Specimens were matched and split into Groups 1 and 2, similar to Part 1. Cadaveric specimens were axially loaded in cyclical fashion to analyze for construct stiffness, fracture displacement femoral neck shortening and changes in the neck shaft angle.ResultsPart 1: There were 18 matched patients (14 males and 4 females) in both Group 1 and Group 2. There were no statistically significant differences between the two groups with respect to Pauwels angle, femoral neck shortening, changes in neck-shaft angle, AVN or nonunion. One reoperation in Group 1 and four in Group 2.Part 2: All five cadaveric specimens in both groups survived the 10,000-cycle loading regimen. We were unable to detect any significant differences between the two groups with respect to construct stiffness, change in neck-shaft angle or amount of femoral neck shortening.ConclusionBased on the results of both clinical case series and biomechanical testing, an inferomedial neck buttress plate does not appear to offer long-term benefits with respect to maintenance of alignment or achieving union but may potentially help in obtaining the reduction.     

Comparison of oblique triangular configuration and inverted equilateral triangular configuration of three cannulated screws in treating unstable femoral neck fracture: A finite element analysis

BackgroundThe cross-sectional area of three parallel screws might affect the stability of the internal fixation of femoral neck fractures. The screws fixed in the oblique-triangle configuration (OTC) were assumed to have a larger cross-sectional area, but the biomechanical stability has not yet been validated. In this study, finite element analyses were performed to compare the biomechanical properties of the internal fixation fixed by the OTC and the traditional Inverted Equilateral Triangle Configuration (IETC).MethodPauwels type III fracture was established on the three-dimensional femoral model and three cannulated screws with the OTC and traditional IETC methods were applied. The oblique-triangle configuration with the largest area inscribed the femoral neck isthmus by the three screws was determined, the area and circumference of the cross-section formed by the OTC and IETC model were compared. Stress, strain, and displacement peaks of the two configuration models under different loads were compared. Twelve pairs of nodes on the fracture ends were selected and the displacement of the fracture ends was evaluated through the displacement between these nodes.ResultsThe area and circumference of the cross-section formed by the OTC were larger than those in the IETC model. The degree of stress dispersion around the screw holes in the OTC model was better than that of the IETC, but the stress distribution order of the three screws in the two models was consistent. The maximum stress, strain, displacement, and displacement of the fracture end in the OTC model were smaller than those in the IETC model. The stress, strain, displacement, and fracture end displacement peaks of the two fixed models gradually increase with the increase of loads.ConclusionThe oblique-triangle configuration showed superior mechanical properties than the IETC in finite element analyses. This study suggests that when three screws are fixed in parallel method, the larger the cross-sectional area of the screw configuration, the better stability of the internal fixation might be obtained. Furthermore, the biomechanical properties of various spatial configurations and screw holes of the three parallel screws need to be considered before clinical practice.     

Modified dynamic hip screw loaded with autologous bone graft for treating Pauwels type-3 vertical femoral neck fractures

IntroductionManagement of Pauwels type-3 vertical femoral neck fractures has been a challenging clinical problem as they experience high shear forces and thus a greater risk of treatment failure. There is no apparent consensus on the optimal implant type for these injuries. We developed a modified dynamic hip screw (DHS), which was designed to a cage in the lag screw, loaded with autologous bone graft for the treatment of Pauwels type-3 vertical femoral neck fractures.MethodsBetween February 2010 and January 2012, 17 consecutive patients with Pauwels type-3 vertical femoral neck fractures were treated with the modified DHS loaded with autologous bone graft. All patients were followed up for a minimum of 24 months (range, 24–36 months). Surgical details, operative and postoperative complications, the rates of nonunion and osteonecrosis and the Harris hip score were evaluated.ResultsThere were thirteen men and four women with a mean age of 37.2 years (range, 27–52 years). There were no intraoperative complications related to this technology. All fractures healed within 14.1 weeks (range, 12 to 20 weeks). One patient required total hip replacement because of avascular necrosis of the femoral head at 27 months after surgery. According to the Harris hip score, eleven patients (64.7%) had excellent results, four (23.5%) had good results, one (5.9%) had moderate and one (5.9%) had poor result.ConclusionsThe modified DHS loaded with autologous bone graft appears to be a reliable implant for the treatment of Pauwels type-3 vertical femoral neck fractures with fewer complications.     

How to choose the suitable FNS specification in young patients with femoral neck fracture: A finite element analysis

BackgroundConsensus regarding the optimal approach for the treatment of femoral neck fractures remains lacking. A new internal fixation femoral neck system (FNS) was developed and used in clinical practice. We aimed to investigate the biomechanical outcomes of different types of FNS in the treatment of unstable femoral neck fractures.MethodIn this study, we constructed three different types of unstable femoral neck fractures of Pauwels classification with angles of 50°, 60°, and 70°. We set up four test groups, namely, the one-hole plated FNS group, two-hole plated FNS group, inverted cannulated screw group and triangle cannulated screw group. Under 2100 N axial loads, displacements and the von Mises stress of the femur and internal fixation components were measured for each fracture group.ResultsWhen the Pauwels angle was 50°or 60°, the one-hole locking plated FNS was as superior as the two-hole plated FNS in terms of femur and internal fixation displacement, and the inverted cannulated screw had slightly better stability than the triangular cannulated screw. However, when the angle increases to 70°, the two-hole locking plate has the minimum displacement, followed by the triangular cannulated screw and inverted cannulated screw, which is the worst displacement for the single-hole locking plate. Regardless of the angle, the two sets of FNS have higher internal fixation stress than the two sets of cannulated screws, which is approximately 1.6-3.0 times that of the cannulated screw group.ConclusionFrom the perspective of biomechanics, we suggest that when the angle of the fracture line is less than 60°, both single-hole locking plated or double-hole locking plated FNS can be used to treat unstable femoral neck fractures. However, when the angle of the fracture line is greater than 70°, we recommend using a double-hole locking plated FNS. This result needs further verification in further clinical studies.     

Is bone-cement augmentation of screw-anchor fixation systems superior in unstable femoral neck fractures? A biomechanical cadaveric study

Objectives

Improved fixation techniques with optional use of bone cements for implant augmentation have been developed to enhance stability and reduce complication rates after osteosynthesis of femoral neck fractures. This biomechanical study aimed to evaluate the effect of cement augmentation on implant anchorage and overall performance of screw-anchor fixation systems in unstable femoral neck fractures.

Biomechanical evaluation of different internal fixation methods based on finite element analysis for Pauwels type III femoral neck fracture

Background and objectiveThe best internal fixation method for the treatment of Pauwels type III femoral neck fractures (FNFs) remains to be demonstrated. Through finite element analysis, this study explored whether dynamic hip screw (DHS) combined with anti rotation screw or medial buttress plate can improve the stability of internal fixation, and the femoral neck system (FNS) with similar structure to DHS and the traditional cannulated screw (CSs) were added for comparison. To evaluate their respective biomechanical advantages and disadvantages in the treatment of Pauwels type III FNFs.MethodsSix groups of internal fixation models for the treatment of FNFs were established, including CSs, DHS, DHS combined with single anti-rotation screw (DHS + SS), and DHS combined with both anti-rotation screw (DHS + BS), DHS combined with medial buttress plate (DHS + MBP), new femoral neck internal fixation system (Femoral Neck System, FNS). Four finite element analysis models were established for each group, evaluation of femoral displacement and internal fixation stress during stair climbing and walking conditions, and the contact force of the hip joint was used in two cases, dynamic and static.ResultsThe fracture plane motion and peak stress of internal fixators were the lowest with DHS + BS and CSs fixation, and the two results are very close, The peak value of DHS combined with anti rotation screw or medial buttress plate is much lower than that of DHS, indicating that the fixation effect of the combined model is enhanced, and there is no significant difference between FNS and DHS + SS.ConclusionBoth the anti rotation screw and medial buttress plate can effectively reduce the movement of fracture section and share the shear force of DHS, FNS has the similar fixation stability to DHS + SS, DHS + BS has the biomechanical advantages of significantly reducing the risk of internal fixation failure and femoral yield. Therefore, the use of DHS + BS may be a more favorable choice in the case of Pauwels type III FNFs with higher fixation requirements.     

Revisiting Pauwels' classification of femoral neck fractures

Pauwels’ femoral neck fracture classification is based on the biomechanical principle that shear stress and varus force increase along more vertically oriented fractures, resulting in higher risk of fracture displacement and ultimately nonunion. This principle continues to guide construct selection for femoral neck fracture internal fixation and is the foundation for treating non-union with valgus osteotomy. However, with poor inter- and intra-rater reliability, dated treatment recommendations, and unreliable prognostic value, the Pauwels classification cannot be directly applied in its entirety to the management of femoral neck fractures in modern practice.     

Biomechanical properties of off-axis screw in Pauwels III femoral neck fracture fixation: Bicortical screw construct is superior to unicortical screw construct

ObjectivesThe purpose of this study is to determine the biomechanical properties of the bicortical off-axis screw fixation for stabilizing of Pauwels III femoral neck fractures compared with other fixation methods.MethodsEighteen synthetic femurs (Sawbones Pacific Research Laboratories, Vashon, WA) were divided into three groups. The osteotomy was made vertically to mimic the Pauwels type III femoral neck fracture. Group A (n = 6) was fixed with traditional inverted triangle cannulated screws. Group B (n = 6) was fixed with a unicortical off-axis screw and two parallel cannulated screws. Group C (n = 6) was fixed with a bicortical off-axis screw and two parallel cannulated screws. Each group was tested with a nondestructive axial compression test at a 7° of valgus followed with 1000 cycles of cyclic loading test from 100 N to 1000 N. Finally, a destructive axial compression test was applied until catastrophic failure.ResultsThe average axial stiffness from group A to group C was 856.5, 934, and 1340 N/mm, respectively. The average ultimate failure load from group A to group C was 2612.7, 2508.8, and 3706 N, respectively. Group C exhibited significantly greater axial stiffness and a higher ultimate failure load than the other two groups (P < 0.05). Regarding the interfragmental displacement, the values from group A to group C were 0.41, 0.83, 0.36, respectively, and group B exhibited significantly larger fracture gap formation after the cyclic loading test.ConclusionsThe results of this biomechanical study show statistically significant increases in axial stiffness and ultimate failure load for the off-axis screw placed in bicortical fashion. Once the off-axis screw was positioned unicortically, the largest fracture diastasis was observed as compared to the other two methods.     

利用有限元探究内固定治疗股骨颈骨折的生物力学研究

目的:利用有限元分析研究不同内固定治疗Pauwels Ⅲ型股骨颈骨折的生物力学特点。方法:选取1名健康受试者的股骨CT数据进行三维重建,骨折造模,装配动力髋螺钉、锁定加压钢板、三枚空心钉、四枚空心钉和髓内钉,建立有限元模型,在股骨头顶端轴向加载1400 N应力。研究不同内固定的应力分布和位移分布、股骨的应力分布和位移分布,并比较内固定和股骨模型的应力峰值和位移峰值。结果:股骨和内固定应力较大区域均分布于股骨颈及股骨干部位,且在骨折线附近均出现应力增大的现象;内固定位移分布主要集中于股骨头内螺钉尖端位置,股骨位移集中于股骨头顶端,应力加载位置。四枚空心钉的应力最小,峰值为135.3 MPa;锁定加压钢板的应力最大,峰值为405.9 MPa,但锁定加压钢板的位移12.3 mm为最小峰值;三枚空心钉的位移18.8 mm为最大峰值;三枚空心钉固定时,股骨受力最小,应力峰值为36.8 MPa,但股骨位移最大,峰值为19.3 mm;锁定加压钢板固定时,股骨受力104.6 MPa为最大应力峰值而位移12.6mm为最小位移峰值。结论:锁定加压钢板在固定股骨颈骨折时稳定性最高,但股骨和内固定承受更大的压力和剪切力;动力髋螺钉固定短期内促进骨折愈合较有优势,但长期固定时髓内钉固定更佳。     

Evaluation of valgus intertrochanteric osteotomy in neglected fracture neck femur in young adults

BackgroundFemoral neck fractures in young adults have always presented a difficult problem with high rates of non-union and avascular necrosis. At our centre we have been using the traditional Pauwels intertrochanteric osteotomy for neglected un-united femoral neck fractures in young adults. We have made certain modifications in this procedure to suit our resources and so we evaluated the outcome of this procedure at our institute.MethodsThe study included fifty consecutive cases of neglected femoral neck fractures treated at our centre between February 1996 and October 2012. Patients in whom internal fixation had failed were excluded. The average age of the patients was 37 years (range: 17–55 years). Eleven of the patients were female & Thirty-nine were male. Fifteen patients belonged to Pauwels grade 1, Twenty-six patients belonged to grade 2, and nine belonged to grade 3. The interval between the injury and operation ranged from 1 to 12months (average: 4.3 months). The cases were operated on a normal table using a Watson Jones Approach. The fracture ends were freshened and fixed using a 6.5mm screw followed by a valgus osteotomy which was fixed by a double angle (120 degree) blade plate.ResultsA fracture union rate of 90% (45 cases) was achieved. Two of the healed cases developed avascular necrosis. Results were graded using Askin and Bryan's criteria. Overall, an excellent result was seen in 35 patients, good in 5, fair in 5 and poor in 5. Of the five patients having poor result (3 non-union, 1 implant breakage, 1 implant cut out), two refused revision surgery. In remaining three, one underwent total hip arthroplasty and in two revision osteotomy was performed.ConclusionWe believe that intertrochanteric osteotomy provides a good outcome for neglected femoral neck fractures. Performing the procedure on a routine table, with Watson Jones approach and fixing with double angle blade plate is a good option.     

股骨颈骨折治疗中支持带的生物力学特点

目的：研究股骨颈骨折治疗中支持带的生物力学特点。方法 ：通过1名75岁老年女性志愿者的CT数据,经过软件处理,构建完整股骨模型和骨折后3枚空心钉固定模型,并分为有支持带模型和无支持带模型,使用不同模型的Von-Mises力分布和模型位移差异分析其稳定性差异,研究支持带在股骨颈骨折治疗中的力学特点。结果：在完整股骨上,位移最明显部位出现在股骨头的负重区。有支持带模型位移为0.381 37 mm,无支持带模型位移为0.381 68 mm。Von-Mises力分布最集中的部位在股骨颈内下方,有支持带模型为11.80 MPa,无支持带模型为11.91 MPa。在骨折3枚空心钉内固定模型中,位移最明显部位同样出现在股骨头的负重区。有支持带模型位移为0.457 27 mm,无支持带模型位移为0.458 63 mm。Von-Mises力分布最集中位置在股骨颈内下方,有支持带模型为59.22 MPa,无支持带模型为59.14 MPa。对于空心钉,Von-Mises力峰值均出现在后上方空心钉,有支持带模型为107.48 MPa,无支持带模型为110.84 MPa。3枚螺钉中前上方螺钉Von-Mises力...     

Poor relation between biomechanical and clinical studies for the proximal femoral locking compression plate

Background and purpose — The proximal femur locking compression plate (PF-LCP) is a new concept in the treatment of hip fractures. When releasing new implants onto the market, biomechanical studies are conducted to evaluate performance of the implant. We investigated the relation between biomechanical and clinical studies on PF-LCP.

Methods — A systematic literature search of relevant biomechanical and clinical studies was conducted in PubMed on December 1, 2015. 7 biomechanical studies and 15 clinical studies were included.

Results — Even though the biomechanical studies showed equivalent or higher failure loads for femoral neck fracture, the clinical results were far worse, with a 37% complication rate. There were no biomechanical studies on pertrochanteric fractures. Biomechanical studies on subtrochanteric fractures showed that PF-LCP had a lower failure load than with proximal femoral nail, but higher than with angled blade plate. 4 clinical studies had complication rates less than 8% and 9 studies had complication rates between 15% and 53%.

Interpretation — There was no clear relation between biomechanical and clinical studies. Biomechanical studies are generally inherently different from clinical studies, as they examine the best possible theoretical use of the implant without considering the long-term outcome in a clinical setting. Properly designed clinical studies are mandatory when introducing new implants, and they cannot be replaced by biomechanical studies.     

Cement augmentation of implants—no general cure in osteoporotic fracture treatment. A biomechanical study on non‐displaced femoral neck fractures

Femoral neck fractures in the elderly are a common problem in orthopedics. Augmentation of screw fixation with bone cement can provide better stability of implants and lower the risk of secondary displacement. This study aimed to investigate whether cement augmentation of three cannulated screws in non‐displaced femoral neck fractures could increase implant fixation. A femoral neck fracture was simulated in six paired human cadaveric femora and stabilized with three 7.3 mm cannulated screws. Pairs were divided into two groups: conventional instrumentation versus additional cement augmentation of screw tips with 2 ml TraumacemV+ each. Biomechanical testing was performed by applying cyclic axial load until failure. Failure cycles, axial head displacement, screw angle changes, telescoping and screw cut‐out were evaluated. Failure (15 mm actuator displacement) occurred in the augmented group at 12,500 cycles (± 2,480) compared to 15,625 cycles (± 4,215) in the non‐augmented group (p = 0.041). When comparing 3 mm vertical displacement of the head no significant difference (p = 0.72) was detected between the survival curves of the two groups. At 8,500 load‐cycles (early onset failure) the augmented group demonstrated a change in screw angle of 2.85° (± 0.84) compared to 1.15° (± 0.93) in the non‐augmented group (p = 0.013). The results showed no biomechanical advantage with respect to secondary displacement following augmentation of three cannulated screws in a non‐displaced femoral neck fracture. Consequently, the indication for cement augmentation to enhance implant anchorage in osteoporotic bone has to be considered carefully taking into account fracture type, implant selection and biomechanical surrounding. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:314–319, 2016.     

Biomechanical evaluation of compression buttress screw and medial plate fixation for the treatment of vertical femoral neck fractures

ObjectiveTo compare the biomechanical properties of compression buttress screw (CBS) fixation with three plate fixation methods for the treatment of vertical femoral neck fractures (FNFs).MethodsA total of forty synthetic femoral models with simulated Pauwels type III fractures (angle of 70°) were equally assigned to one of four fixation groups: CBS fixation, anteromedial plate fixation (AMP), medial buttress plate fixation (MBP) and medial buttress plate fixation without proximal screw (MBPw). Within each group, half of the specimens were randomly assigned to two loading settings, an axial compression loading test and a hip-flexion torsion test.ResultsThere were no significant differences in axial load to failure, axial stiffness, torsional strength, or torsional stiffness when comparing CBS with MBP (p>0.05). In the axial compression loading test, both CBS and MBP showed higher load to failure and axial stiffness than MBPw (p<0.05). In torsional testing, AMP exhibited superior torsional strength and torsional stiffness than both MBPw and MBP (all p<0.05) and a higher torsional strength than CBS fixation (p<0.05). There were no significant differences in torsional stiffness between the CBS and AMP fixation groups (p>0.05).ConclusionThe biomechanical parameters of CBS fixation are comparable to that of AMP and MBP, and demonstrate superior axial stiffness than MBPw fixation. Although the CBS method for surgical fixation of vertical FNF holds promise as a less invasive surgical technique than plate fixation with similar biomechanical assessments, further clinical evaluation is warranted.     

Vertical shear fractures of the femoral neck. A biomechanical study.

A biomechanical cadaver study was performed to compare the strength and stability of three cannulated cancellous lag screws with a sliding hip screw for fixation of a vertically oriented fracture of the femoral neck (Pauwels Type III). Using eight matched pairs of human cadaveric femurs, vertically oriented femoral neck osteotomies were created, reduced, and randomized to one of the two fixation methods. The constructs were tested with incremental axial loading from 100 N to 1200 N and cyclical loading at 1000 N for 10,000 cycles; fracture displacements and ultimate load to failure were determined. The specimens stabilized using a sliding hip screw showed less inferior femoral head displacement, less shearing displacement at the osteotomy site, and a much greater load to failure than did those stabilized with multiple cancellous lag screws. These results support the use of a sliding hip screw for treatment of vertically oriented fractures of the femoral neck.     

Biomechanical effect of anterior talofibular ligament injury in Weber B lateral malleolus fractures after lateral plate fixation: A finite element analysis

ObjectiveTo determine the biomechanical effect of anterior talofibular ligament injury in Weber B lateral malleolus fractures after lateral plate fixation.MethodA three-dimensional model was established based on CT images from a healthy volunteer. The simulation of lateral malleolus fracture, and the modeling and assembly of plate were completed by referring to characteristics of Weber B lateral malleolus fractures, as well as the technical characteristics of open reduction and internal fixation of lateral plate. Operating conditions were set up for groups A−D. The proximal end of the model was restrained in all four groups, 200 N of upward force and 100 N of backward force were applied at anterior of talus head in order to simulate the dorsiflexion of ankle joint. Biomechanical differences of the lateral plate were observed under various conditions of different ligament ruptures.ResultsThe maximum stress value of group A was the smallest, approximately 78.47 N, while that of group C was the largest, approximately 238.83 N. The maximum stress value of group B was about 91.69 N; and that of group D was about 184.08N. Importantly, location of the maximum stress in group D (CUT ATaF) was displaced from the posterior edge to the anterior edge of the plate, which was different from those of the other three groups.ConclusionsThe anterior talofibular ligament injury may be a major contributing factor to the stress of lateral plate fixation following Weber B lateral malleolus fracture. It should be considered as an essential risk factor for evaluation of the stability in these fractures.     

Versorgung pertrochant?rer Femurfrakturen

Biomechanical considerations are relevant in the treatment of peritrochanteric fractures. Concomitant diseases and osteoporosis place high demands on the primary stability of the operative treatment. In the situation of unstable fractures (AO/ASIF 31-A2 and A3), even normal activities of life can easily exceed the critical limits of stability, which can result in implant failure. Both intramedullary and extramedullary implants are used successfully in the treatment of even unstable fractures. Different variations in the implant design and anchorage of the load carrier of the femoral neck are available and may have different biomechanical characteristics. Biomechanical tests show that new developments of implants can increase stability. Nevertheless, accurate reduction and operative technique is essential to ensure uneventful fracture healing. Although some supportive measures are very promising, such as augmentation, further research is required to increase stability in the unstable and osteoporotic fracture situation.     

The Influence of Dorr Type and Femoral Fixation on Outcomes Following Total Hip Arthroplasty for Acute Femoral Neck Fractures: A Multicenter Study

BackgroundThe American Academy of Orthopaedic Surgeons guidelines report moderate evidence for cementing femoral stems for hip fractures, mainly derived from hemiarthroplasty literature. This is the first large, nonregistry study examining the influence of femoral fixation, implant type, patient characteristics, and radiographic factors on outcomes after total hip arthroplasty (THA) for acute femoral neck fractures.MethodsA multicenter retrospective study was performed of 709 THA cases (199 cemented, 510 cementless) for femoral neck fractures from 2006 to 2020 at three large academic institutions. Demographics, perioperative characteristics, and radiographs were reviewed. Kaplan-Meier survivorship curves were generated for multiple outcomes. Univariate and multivariate analyses were performed with P ≤ .05 denoting significance.ResultsCementless stems had a higher all-cause aseptic femoral revision rate (5.1 versus 0.5%, P = .002) and periprosthetic femoral fracture rate (4.3 versus 0%, P = .001). Each successive Dorr type had a higher fracture rate with cementless implants: 2.3%, 3.7%, and 15.9% in Dorr A, B, and C, respectively (P < .001). Logistic regression analyses confirmed that cementless stems (P = .02) and Dorr C bone (P = .001) are associated with periprosthetic fractures; collared implants and prophylactic cables did not protect against fractures. There was no difference in rates of dislocation, septic revision, or mortality between groups.ConclusionCementless stems during THA for femoral neck fractures have a higher aseptic femoral revision rate, specifically for periprosthetic fractures. Dorr C bone was particularly prone with an alarmingly high fracture rate. All fractures occurred in cementless cases, suggesting that cemented stems may minimize this complication.Level of EvidenceIII.     

股骨颈骨折2枚空心螺钉内固定的力学稳定性研究

目的:分析2枚和3枚空心螺钉固定不同骨折线方向的股骨颈骨折的力学稳定性,为2枚空心螺钉临床应用及其适应证的选择提供理论依据。方法:采集15具国人股骨尸体标本,构建3种Pauwels角(30°、50°和70°)的股骨颈骨折模型,分别行3枚及2枚空心螺钉内固定,采用生物力学检测仪分别测定抗张位移、竖向位移、剪切位移、综合位移、缝隙距、扭矩和刚度值,评价2枚和3枚空心螺钉内固定的力学稳定性。结果:Pauwels角为30°和50°时,2枚空心螺钉内固定的抗张位移、竖向位移、剪切位移、综合位移、缝隙距、扭矩和刚度值与3枚空心螺钉内固定相比较,差异无统计学意义(P0.05);当Pauwels角为70°时,采用3枚空心螺钉内固定后,其力学稳定性优于2枚螺钉内固定,差异有统计学意义(P0.05),同时发现Pauwels角为70°时,即使采用3枚空心螺钉内固定,其力学稳定性明显较Pauwels角为30°和50°时差。结论:Pauwels角为30°和50°时,2枚空心螺钉内固定与3枚空心螺钉内固定的力学稳定性相同,2枚空心螺钉内固定已能较好地维持股骨颈骨折的稳定。而当Pauwels角为70°时,3枚空心螺钉内固定力学稳定性则优于2枚空心螺钉内固定,但其力学稳定性较Pauwels角为30°和50°时弱,手术时需采用角稳定系统或者加用抗滑螺钉以增强骨折内固定的稳定性。