Biomechanical comparison of proximal interlocking screw constructs in different subtrochanteric fracture models

BackgroundDepending on the size of the proximal bone segment, either a standard locking construct or a recon locking construct can be used in intramedullary nailing for a subtrochanteric fracture. However, the most appropriate construct for a given size of proximal bone segment has not yet been determined. Therefore, this study aimed to identify the appropriate construct using biomechanical testing.MethodsFourteen intramedullary nails for each locking construct (standard and recon) were inserted into 28 synthetic femurs. Fourteen subtrochanteric fracture models were developed by creating parallel defects (2 cm in size) 2 cm distal to the lower edge of the lesser trochanter (low fracture group), and 14 fracture models were developed with identical defects situated 1 cm distal to the lower edge of the lesser trochanter (high fracture group). An axial load experiment was conducted to measure the stiffness and failure load for each proximal interlocking screw construct.ResultsThere were no statistically significant differences in the stiffness and failure load between the locking constructs in the low fracture group. However, the stiffness and failure load were significantly greater for the recon locking construct than for the standard locking construct in the high fracture group.ConclusionThe standard locking system allows for sufficient fixation strength when performing intramedullary nailing for subtrochanteric fractures located 2 cm distal to the lower edge of the lesser trochanter.     

Effect of fracture levels on the strength of bone-implant constructs in subtrochanteric fracture models fixed using short cephalomedullary nails: A finite element analysis

ObjectivesThis study was conducted to investigate the stress around nails and cortical bones in subtrochanteric (ST) fractures fixed using short cephalomedullary nails (CMNs) in finite element models (FEMs) and to determine the appropriate short CMN type for different fracture levels.MethodsThe following three types of short CMNs were used: type A, which is 170 mm in length and has 1 distal locking screw; type B, 200 mm in length and 1 distal screw; and type C, 200 mm in length and 2 distal screws. A total of 24 FEMs were tested on a transverse ST fracture at 8 levels [0, 10, 20, 25, 30, 35, 40 and 50 mm below the lower margin of lesser trochanter (LT)], and were fixed using 3 different CMN types. Finite element analysis was then performed to evaluate the stress around the cortical bones and the CMNs under the assumption of anatomical reduction and fracture gap of 1 mm.ResultsPeak von Mises stress (PVMS) was greatest on the cortical bone around the distal screw hole and was greater than the yield strength at fracture levels ≥ 35 mm below the LT in FEMs fixed with type A and B. In contrast, FEMs fixed with type C showed PVMS less than the yield strength at all fracture levels. The PVMS within the implant was greater than the yield strength at the junction of the nail with the distal screw and distal screw itself at fracture levels ≥ 35 mm below the LT in FEMs fixed using type A. Conversely, in FEMs fixed using type B and C, all PVMSs within the implant were less than the yield strength, regardless of the fracture level.ConclusionShort CMNs 170 or 200 mm in length with 1 distal screw may be used in a limited manner in high ST transverse fractures under the assumptions of anatomical reduction and fracture gap ≤ 1 mm. Meanwhile, short CMN 200 mm in length with 2 distal screws may be an available treatment option in most of ST transverse fractures regardless of the fracture level under the same set of assumptions.     

Biomechanical evaluation of the risk of secondary fracture around short versus long cephalomedullary nails

Introduction

For proximal femur fractures, long cephalomedullary nails (CMNs) are often selected to avoid a diaphyseal stress riser at the tip of a shorter nail. Secondary peri-implant fracture rates for long and short CMN have not been shown to differ clinically. This study biomechanically compares both CMN in a cadaveric model.

Methods

Ten matched pairs of cadaveric femora with short or long CMN were axially loaded and internally rotated to failure.

Results

Resulting fractures involved distal interlocking screws of the short and long CMN. Energy and rotation to failure were significantly greater for short CMN. Torque at failure trended higher for short CMN but not significantly. No statistical difference was detected in stiffness of the short and long CMN.

Discussion

A greater risk of secondary fracture is not indicated for short versus long CMN under torsional stress. Short CMN may be suitable in the younger patient.

     

长Gamma钉治疗股骨转子下骨折

目的评价应用长Gamma钉内固定治疗股骨转子下骨折的效果。方法16例股骨转子下骨折采用长Gamma钉内固定,C臂X线机透视下牵引复位,必要时做小切口钢丝环扎或钢缆捆绑复位。结果1例发生延迟愈合,其余病例术后半年随访时骨折均已愈合。肢体功能良好。结论股骨转子下骨折应用长Gamma钉内固定,手术创伤小,骨折愈合率高,符合生物力学的要求。     

Biomechanical analysis of peri‑implant fractures in short versus long cephalomedullary implants following pertrochanteric fracture consolidation

IntroductionPertrochanteric femur fracture fixation with use of cephalomedullary nails (CMN) has become increasingly popular in recent past. Known complications after fracture consolidation include peri‑implant fractures following the use of both short and long nails, with fracture lines around the tip of the nail or through the interlocking screw holes, resulting in secondary midshaft or supracondylar femur fractures, respectively. Limited research exists to help the surgeon decide on the use of short versus long nails, while both have their benefits. The aim of this biomechanical study is to investigate in direct comparison one of the newest generations short and long CMNs in a human anatomical model, in terms of construct stability and generation of secondary fracture pattern following pertrochanteric fracture consolidation.MethodsEight intact human anatomical femur pairs were assigned to two groups of eight specimens each for nailing using short or long CMNs. Each specimen was first biomechanically preloaded at 1 Hz over 2000 cycles in superimposed synchronous axial compression to 1800 N and internal rotation to 11.5 Nm. Following, internal rotation to failure was applied over an arc of 90° within one second under 700 N axial load. Torsional stiffness as well as torque at failure, angle at failure, and energy to failure were evaluated. Fracture patterns were analyzed.ResultsOutcomes in the study groups with short and long nails were 9.7 ± 2.4 Nm/° and 10.2 ± 2.9 Nm/° for torsional stiffness, 119.8 ± 37.2 Nm and 128±46.7 Nm for torque at failure, 13.5 ± 3.5° and 13.4 ± 2.6° for angle at failure, and 887.5 ± 416.9 Nm° and 928.3 ± 461.0 Nm° for energy to failure, respectively, with no significant differences between them, p ≥ 0.17. Fractures through the distal locking screw holes occurred in 5 and 6 femora instrumented with short and long nails, respectively. Fractures through the lateral entry site of the head element were detected in 3 specimens within each group. For short nails, fractures through the distal shaft region, not interfacing with the implant, were detected in 3 specimens.ConclusionFrom a biomechanical perspective, the risk of secondary peri‑implant fracture after intramedullary fixation of pertrochanteric fractures is similar when using short or long CMN. Moreover, for both nail versions the fracture pattern does not unexceptionally involve the distal locking screw hole.     

改良梅花型交锁髓内钉固定股骨粗隆下骨折的生物力学研究

目的比较自行设计的改良梅花型交锁髓内钉与国产Gamma钉固定股骨粗隆下骨折的即刻生物力学特性,探讨改良梅花型交锁髓内钉固定股骨粗隆下骨折的可行性。方法 8具成年健康男性股骨标本,按左右侧分为实验组和对照组,分别制作股骨粗隆下横形骨折模型。实验组采用长度350 mm的改良梅花型交锁髓内钉固定骨折,对照组采用长度350 mm国产Gamma钉固定骨折。分别检测抗轴向压缩、抗侧弯及抗扭转力学性能,并进行统计学分析。结果 1 000 N轴向载荷压力下的抗压刚度、1 000 N压力下的抗弯曲刚度及3 N/m下的抗扭转刚度:对照组分别为(2 359.4±200.8)N/mm、(614.7±60.2)N/m、(0.64±0.16)Nm/°,实验组分别为(2 178.1±129.5)N/mm、(439.1±48.2)N/m、(0.48±0.13)Nm/°。两组抗压、抗弯曲、抗扭转3项指标比较差异均无统计学意义(P>0.05)。结论改良梅花型交锁髓内钉具有较好的生物力学性能,可用于内固定治疗股骨粗隆下横形骨折。     

Treatment of subtrochanteric femoral fracture with long proximal femoral nail antirotation

Objective： Subtrochanteric femoral fractures are severe injuries. Although many treatment methods have been developed, controversy exists regarding the optimal management of these fractures. This study evaluated the clinical outcome of subtrochanteric femoral fractures fixed with long proximal femoral nail antirotation （PFNA-Iong）. Methods： Between October 2006 and February 2008, 25 patients with traumatic subtrochanteric fractures of the femur were treated with PFNA-long. Closed reduction and fixation were performed in 20 cases. In the remaining 5 cases, closed reduction was difficult, so limited open reduction was performed, with bone grafting in 4 cases and circumfer-ential wiring in 4 cases. Results： The average follow-up time was 16.1 months. All subtrochanteric femoral fractures healed uneventfully except one case of delayed union. The mean union time was 26.2 weeks. Technical difficulties with nail insertion were encountered in 3 cases. No implant failure was observed. Conclusion： PFNA-long is effective in treatment of subtrochanteric femoral fractures, with a high rate of bone union, minor soft tissue damage, early return to functional exercise and few implant-related complications.     

Trochanteric-entry long cephalomedullary nailing of subtrochanteric fractures caused by low-energy trauma

BACKGROUND: Subtrochanteric fractures of the femur that are caused by low-energy trauma are less common than other proximal femoral fractures, but they occur in a similar population of elderly individuals, who are often socially dependent and medically frail. Although a wide range of operative techniques have been used, cephalomedullary nailing theoretically provides the most minimally invasive and biomechanically stable means of treating these complex fractures. The purpose of the present review was to evaluate the functional outcome and perioperative complications associated with the use of a trochanteric-entry cephalomedullary nail to treat all low-energy subtrochanteric fractures that were seen at a single institution. METHODS: Over an eight-year period, we used the long Gamma nail to treat a consecutive series of 302 local patients who had sustained a subtrochanteric fracture during low-energy trauma. The mortality, prevalence of complications, and functional outcome were prospectively assessed during the first year after the injury. Survival analysis was used to assess the rates of reoperation and implant revision during the first year after surgery. RESULTS: At one year, seventy-four (24.5%) of the original 302 patients had died and seventeen (5.6%) had been lost to follow-up. The remaining 211 patients (69.9%) were evaluated with regard to the functional outcome and postoperative complications during the first year after the injury. As with other proximal femoral fractures in the elderly, there was an increased level of social dependence, an increase in the use of walking aids, and a reduction in mobility among survivors. Although eighty-eight (41.7%) of the 211 patients who were evaluated at one year after the injury had some degree of hip discomfort, only two described the pain as severe and disabling. Reoperation for the treatment of implant or fracture-related complications was required in twenty-seven (8.9%) of the 302 patients; however, only eighteen of these patients required nail revision, corresponding with a one-year nail-revision rate of 7.1% (95% confidence interval, 4.0% to 10.2%) on survival analysis. Of the 250 patients who survived for six months after the injury, five (2%) had a nonunion that was confirmed at the time of surgical exploration. Complications related to the proximal lag screw were seen in twelve of the original 302 patients, and a fracture distal to the tip of the nail occurred in five. Although superficial wound infection was relatively common, deep infection occurred in only five of the 302 patients. CONCLUSIONS: Subtrochanteric fractures caused by low-energy trauma are similar to other proximal femoral fractures, with a high mortality rate during the first year after the injury. Trochanteric-entry cephalomedullary nails are associated with an acceptable rate of perioperative complications and favorable functional outcomes. LEVEL OF EVIDENCE: Therapeutic Level IV.     

长Gamma 3型髓内钉内固定治疗股骨粗隆下骨折临床疗效分析

目的探讨长Gamma 3型髓内钉内固定治疗股骨粗隆下骨折的疗效。方法对60例股骨粗隆下骨折采用闭合复位或有限切开复位长Gamma 3型髓内钉内固定治疗。结果 60例均获随访10-24个月,平均18个月。骨折愈合时间9-15个月,平均10个月。末次随访时髋关节功能Harris评分：优16例,良35例,可9例,优良率85%。未发生拉力螺钉切割出股骨头、股骨干骨折、髋内翻畸形等严重并发症。结论采用长Gamma 3型髓内钉内固定治疗股骨粗隆下骨折创伤小,疗效好,便于术后早期功能锻炼,并发症发生率低。     

加长型PFNA治疗股骨转子下粉碎性骨折的临床研究

[目的]评价采用加长型股骨近端螺旋刀片抗旋髓内钉(proximal femoral nail anti-rotation,PFNA)治疗股骨转子下粉碎性骨折的临床疗效.[方法]2006年6月～2011年6月,本院采用AO/ASIF加长型PFNA治疗股骨转子下粉碎性骨折83例,男57例,女26例；年龄19 ～72岁,平均42.6岁,所有患者均为股骨单侧闭合性骨折,受伤至手术时间间隔为3～7d,平均4.1d.术后第1、2、3、6、9、12个月门诊随访,以后每年至少门诊复查1次.随访时所有患者均拍摄股骨中近段正、侧位X线片.临床疗效评价采用Harris髋关节功能评分标准.[结果]83例患者手术时间45 ～ 95 min,平均65.7 min；术中出血量50 ～150ml,平均86.4 ml,所有患者均为术后4～7d下地扶拐逐渐限量负重行走.83例患者均获得完整随访,随诊4,～36个月,平均18.3个月,所有患者术后未出现感染、下肢静脉血栓形成,未出现螺旋刀片切割股骨头及断钉现象,3例出现髋内翻短缩畸形；无骨折不愈合者,骨折愈合时间为3.3 ～5.7个月,平均3.6个月.按Harris髋功能评分标准:优56例,良24例,中3例,优良率96.39％( 80/83).[结论]加长型PFNA治疗具有微创、固定强度高、生物力学特性好等优点,在治疗股骨转子下粉碎性骨折时骨愈合率高、功能恢复快、并发症少.     

Implant failure of long proximal femoral nail antirotation in patient with subtrochanteric pathologic fracture

Pathologic or impending pathologic fracture is an unhappy clinical manifestation of skeletal metastasis. If possible, stabilization of metastatic bone lesion is recommended for pain relief and improving quality of remaining lives. The long proximal femoral nail antirotation (PFNA; Synthes^?, Switzerland) provides a stable construct for the fixation of pathologic or impending pathologic fracture of femoral metastatic lesion, especially petrochanteric or diaphyseal locations. Implant failure of this device is a rare complication. We report a case of implant failure of the long proximal femoral nail antirotation in patient with subtrochanteric pathologic fracture due to breast cancer with the literature review.     

短与长髓内钉治疗不稳定粗隆下骨折的有限元分析

[目的]对长、短型髓内钉治疗Seinsheimer V型不稳定骨折进行有限元分析,为临床提供生物力学证据。[方法]三维重建Sawbones股骨模型,制备包含四部分骨折块且有20 mm范围内侧缺损的粗隆下骨折模型。制作长、短髓内钉模型。将模型进行匹配、网格划分、赋值属性等有限元分析前处理。装配、定义接触面、边界条件、载荷设置,进行有限元分析。[结果]随着外力增加长钉以及短钉治疗下各组参考指标均呈线性增长,差异有统计学意义(P0.001)。2 000 N载荷下,短钉组近端骨块最小位移显著小于长钉组[(16.397±0.044) mm vs(17.210±0.044)mm,P0.001],短钉组近端骨块最大位移也显著小于长钉组[(28.578±0.020) mm vs(31.171±0.013) mm,P0.001。此外,短钉组近端骨折线缝隙显著小于长钉组[(1.396±0.074) mm vs(1.798±0.052) mm,P0.001],短钉组外侧骨折线缝隙显著小于长钉组[(0.525±0.012) mm vs(0.755±0.017) mm,P0.001]。[结论]短髓内钉较长髓内钉有更佳的控制骨折块移动和对骨折块的把持力,应做为股骨粗隆下骨折内固定的首选。     

Intramedullary nailing of subtrochanteric fractures in elderly patients: Comparative study of helical blade cephalomedullary nail versus reconstruction nail

IntroductionIntramedullary nailing (IMN), which is a common method for treating subtrochanteric fractures, is conducted as cephalomedullary (CMN) or reconstruction (RCN) nailing. Numerous studies have reported the effectiveness of CMN, which requires a shorter surgery time and provides stronger fixation strength with blade-type devices. However, the radiographic and clinical outcomes of the use of CMN and RCN in elderly patients aged ≥65 years have not been compared yet. This study aimed to investigate whether CMN offers superior outcomes over RCN in the treatment of subtrochanteric fractures in elderly patients.Materials and methodsThis retrospective study included 60 elderly patients (17 men and 43 women; mean age: 74.9 years) diagnosed with subtrochanteric fractures and treated with IMN with helical blade CMN (CMN group: 30 patients) or RCN (RCN group: 30 patients) between January 2013 and December 2018 with at least 1 year of follow-up period. Radiologic outcomes were evaluated based on the postoperative state of alignment and the achievement and timing of bony union at the final follow-up. Clinical outcomes were evaluated using the Merle d'Aubigné–Postel score. Radiologic and clinical outcomes in the two groups were compared and analyzed, and the occurrence of complications was examined.ResultsThe difference in malalignment between the two groups was not significant; however, the RCN group achieved more effective reduction. At the final follow-up, bony union was achieved within 18.9 weeks, on average, in 28 patients in the CMN group and within 21.6 weeks, on average, in 27 patients in the RCN group. Twenty patients in the CMN group and 26 in the RCN group showed good or better results according to the Merle d'Aubigné–Postel score. No significant differences were found for any of the parameters.ConclusionsIn the treatment of difficult subtrochanteric fractures in elderly patients, RCN can provide excellent reduction and strong fixation similar to CMN and can result in outstanding clinical and radiologic outcomes.     

股骨重建钉在股骨粗隆下骨折手术中的应用

[目的]探讨股骨重建钉（RIN）治疗股骨粗隆下骨折（SFF）的手术方法及临床疗效。[方法]1998年6月-2005年5月，采用RIN技术对4JD例SFF患者进行固定，其中男27例，女13例；年龄22．．75岁。平均43．5岁。依据Seinsheimer分类：Ⅱ型5例，Ⅲ型13例，Ⅳ型21例，Ⅴ型1例。高能量损伤33例，低能量损伤7例。开放性骨折3例。[结果]4JD例随访8个月-2a6个月，平均1a8个月。X线片观察骨折愈合时间4．2月（3．2-6．5月）。按照韩一生评分标准，优26例，良12例，可2例，优良率95％。无感染、内固定失效、畸形愈合及股骨头缺血性坏死等并发症。[结论]RIN技术是治疗SFF的一种有效方法，具有固定可靠、并发症少、骨折愈合率高等优点。精细的手术操作是手术成功的关键。     

Expert tibia nail for subtrochanteric femoral fracture to prevent thermal injury

IntroductionSubtrochanteric femoral fractures are relatively uncommon, accounting for 7–15% of all hip fractures and treatment of these fractures are considered challenge for orthopaedic surgeons. Although several treatment options are reported with up to 90% of satisfactory results, the choice of the appropriate implant is still a matter of debate. Some authors reported thermal injury after reaming for intramedullary nail fixation in patients with narrow medullary canal.Presentation of caseA 21-year-old female patient was admitted to our hospital because of right subtrochanteric femoral fracture. The narrowest diameter of medullary canal of her femur was about 7 mm but she refused open reduction and internal fixation with plate due to large scar formation. We used expert tibia nail instead of femoral intramedullary nail to prevent thermal injury.DiscussionSubtrochanteric femoral fractures are difficult to treat because of their biomechanical and anatomical characteristics. Although several implants are reported for the surgical treatment of these fractures, intramedullary nails have been advocated due to their biological and biomechanical advantages. However, under certain circumstances with associated injury or anatomic difference we might consider another treatment options.ConclusionExpert tibia nail may be considered one of the treatment options for subtrochanteric femoral fracture with narrow medullary canal. We also emphasize the importance of preoperative evaluation of the medullary canal size for these risky fractures.     

加长型第三代Gamma钉与加长型PFNA内固定治疗股骨粗隆下骨折的比较研究

目的探讨加长型第3代Gamma钉(pTGN)与加长型股骨近端防旋髓内钉(PFNA-long)内固定治疗股骨粗隆下骨折的手术创伤,并发症及手术效果。方法 86例股骨粗隆下骨折根据手术方法分为pTGN组(41例)和PFNA-long组(45例),对两组手术创伤、围手术期并发症和术后功能恢复情况进行比较。结果所有患者获平均21.5个月随访。两组平均术中失血量、透视时间和切开复位率比较差异有统计学意义(P<0.05),PFNA-long组较pTGN组术中出血量少,透视时间短,但切开复位率较pTGN组高。两组平均手术时间、住院时间和末次随访Harris评分比较差异无统计学意义(P>0.05)。结论两种内固定方法治疗股骨粗隆下骨折均可以减少手术后再创伤,并发症较少,内固定有效可行。     

Biomechanical comparison of a 2 and 3 proximal screw-configured antegrade piriformis intramedullary nail with a trochanteric reconstruction nail in an unstable subtrochanteric fracture model

OBJECTIVE: The objective of this study was to test the stiffness and ultimate load to failure of new intramedullary (IM) nail proximal screw configurations as compared to a trochanteric reconstruction nail. METHODS: Twenty-one synthetic composite femurs were mounted on a Material Testing System and tested in axial compression 5 times. The femurs had an 1 of 2 IM nail types inserted with 1 of 3 proximal screw configurations: a 3-screw configuration with 2 transverse screws and a screw angled into the femoral neck; a 2-screw design with a single transverse screw and a single screw angled into the femoral neck; 2 parallel screws angled into the femoral neck. There were 7 specimens in each group. An unstable fracture (OTA/AO 32-C3.2) was created. and the stiffness of these constructs was tested in compression 5 times. Each construct was then loaded to failure in compression. RESULTS: The 3-screw construct provided more axial stiffness (214 N/mm +/- 75) than either the 2-screw construct (123 N/mm +/- 32) or the trochanteric reconstruction nail (127 N/mm +/- 21) (P = 0.017 and 0.035 for 3-screw vs. 2-screw and recon respectively, P = 0.45 for 2-screw vs. recon). Load-to-failure testing demonstrated similarity among the different screw configurations (3-screw = 2230 N +/- 265, 2-screw = 2283 N +/- 260, Reconstruction nail = 2121 N +/- 156) (P = 1.0 all groups). CONCLUSIONS: The proximal 3-screw configuration provided more stiffness than either the 2-screw configuration or trochanteric reconstruction nail. The 2-screw configuration performed equally to a standard trochanteric reconstruction nail in stiffness testing. The ultimate loads to failure for the 3 tested constructs were not significantly different.     

股骨近端防旋髓内钉结合重建钢板治疗股骨转子下骨折不愈合

[目的]探讨股骨近端防旋髓内钉(proximal femoral nail antirotation,PFNA)结合重建钢板治疗股骨转子下骨折不愈合的临床疗效。[方法]2006年5月~2015年5月,采用PFNA结合重建钢板治疗股骨转子下骨折不愈合患者15例。男10例,女5例;年龄45~65岁,平均(57.53±6.85)岁。初次致伤原因:交通事故伤8例,摔伤4例,重物砸伤3例。受伤至该次入院前接受手术治疗1次12例,2次3例。骨折距该次入院时间为11~23个月,平均(15.80±3.88)个月。术后定期依据X线片检查以及Harris髋关节功能评分标准评价髋关节功能。[结果]所有患者均顺利接受手术,术后切口均Ⅰ期愈合,均无严重早期并发症。15例均获得随访,随访时间13~42个月,平均(26.27±9.08)个月。X线片示所有患者均达骨性愈合,无畸形愈合,愈合时间10~31周,平均(18.60±5.97)周,无内固定松动或者移位。颈干角由术前(123.53±9.56)°增加至末次随访时(134.13±2.70)°,差异有统计学意义(P0.05)。Harris髋关节评分由术前(39.07±14.82)分增加至末次随访时(86.07±7.82)分,差异有统计学意义(P0.05)。治疗结果评定为优7例,良6例,可2例,优良率86.67%。[结论]采用PFNA结合重建钢板治疗股骨转子下骨折不愈合,可增加内侧骨皮质的稳定性,避免畸形愈合的发生,临床效果满意。