The effect of locked distal screws in retrograde nailing of osteoporotic distal femur fractures: a laboratory study using cadaver femurs

OBJECTIVES: To examine the effects of locked distal screws in retrograde nails used in unstable osteopenic distal femur fractures. DESIGN: Biomechanical testing of paired human cadaveric femurs. INTERVENTION: Seven matched pairs of embalmed, moderately osteopenic cadaver femurs were instrumented with 12-mm intramedullary nails in a statically locked, retrograde fashion. One femur of each pair had locked distal screws and the other femur had unlocked distal screws. A 2.5-cm gap of bone was cut nine centimeters from the distal condyles to simulate an unstable fracture. The locked distal screw nails were compared to unlocked distal screw nails for collapse of the fracture gap, medial-lateral and anterior-posterior translation of the nail within the fracture site, and fracture angulation. The femurs were axially loaded, cycled, and then loaded to failure. MAIN OUTCOME MEASURES: Motion at the fracture site with axial cyclic loading and site of failure when loaded to failure. RESULTS: After cycling, both locked distal screw and unlocked distal screw nails demonstrated several millimeters medial and anterior translation within the fracture site and approximately 1 mm collapse of the fracture gap. Although no statistically significant differences were found, the locked distal screw nails had less anterior and medial translation, angulation, and collapse of the fracture gap after cycling. Loads to failure were similar for both locked distal screw and unlocked distal screw nails. It was noted that proximal femur failure occurred at the level of the proximal screw hole in the nail at the subtrochanteric level in 7 (4 locked distal screws and 3 unlocked distal screw groups) of the 14 samples. Four other samples failed through the intertrochanteric region (2 locked distal screw and 2 unlocked distal screw groups) and the remainder within the distal fragment by fracture of the femur along the medial cortex. CONCLUSIONS: Although most differences in fixation stability were not significant, the locked distal screw nails exhibited less fracture collapse and anterior and medial translation of the nail at the fracture site than the unlocked distal screw nails. The degree of varus angulation after cyclic loading was also less for the locked distal screw nails. The length of the nail chosen should avoid having proximal locking screws distal to the lesser trochanter, thus averting proximal femur stress risers and fractures.     

交锁髓内钉断裂的原因分析及对策

探讨交锁髓内钉断裂的原因,提出预防的对策。方法：从１９９２年至１９９７年,对６４例复杂粉碎性股骨骨折作了交锁髓内钉固定。结果：５５例随访,平均２６个月。共发生４例交锁钉断裂,断钉率为６．３％。断钉发生在术后６～１４月,３例位于骨折远端第１枚横锁螺孔处,１例位于交锁钉中段。结论：作者认为断钉原因有：开放穿钉,过度分离骨膜,过早负重及功能锻炼不合适等。另外,股骨远端第１枚横锁螺钉离骨折端太近,应力集中。预防断裂的方法有尽量闭合穿钉,选择较粗较长的交锁钉,交锁螺钉应稍远离骨折端,避免过早负重及合适的功能锻炼等。     

Failure of intertrochanteric nailing due to distal nail jamming

Nail impingement against the anterior femoral cortex during nail insertion, or anterior cortex penetration, has been described in the literature as a worrying complication. We describe a previously unreported surgical failure due to a compromised dynamic distal locking caused by distal jamming of the nail. An 80-year-old male suffered a closed right intertrochanteric femoral fracture. Due to the presence of a long medial fragment, a 240 mm long titanium trochanteric nail was chosen to stabilize the fracture. Dynamic distal locking was performed by placing the distal screw at the inferior rim of the elliptical locking hole to allow compression of the fracture site during weight-bearing. Six-month X-ray follow-up revealed a broken nail and nonunion of the fracture due to failed dynamization of the distal locking screw. The nail was removed and replaced by a total arthroplasty. Due to the femoral anterior bow of the shaft, anterior cortical impingement of the distal tip of a nail may result in the failure of the nail to slide within the diaphyseal canal when using a medium-length nail preventing compression of the fracture. Dynamic distal locking can be ineffective if the ability of the distal nail to slide within the diaphyseal canal is hindered. This type of scenario can represent an opportunity for anterior nail impingement. Distal jamming of the nail can thus compromise dynamic compression at the fracture site during loading, thus inducing nonunion of the fracture, and leading to breakage of the osteosynthesis device. For these reasons, caution is recommended when using medium-length trochanteric nails for unstable trochanteric fractures.     

Fatigue performance of angle-stable tibial nail interlocking screws

Purpose

Tibial nail interlocking screw failure often occurs during delayed fracture consolidation or at early weight bearing of nailed unstable fractures, in general when high implant stress could not be reduced by other means. Is there a biomechanical improvement in long-term performance of angle stable locking screws compared to conventional locking screws for distal locking of intramedullary tibial nails?

Methods

Surrogate bones of human tibiae were cut in the distal third and distal locking of the 10 mm intramedullary tibial nail was performed with either two angle stable locking screws or two conventional locking screws in the mediolateral plane. Six specimens per group were mechanically tested under quasi-static and cyclic axial loading with constantly increasing force.

Results

Angle stable locking screw constructs exhibited significantly higher stiffness values (7,809 N/mm ± 647, mean ± SD) than conventional locking screw constructs (6,614 N/mm ± 859, p = 0.025). Angle stable locking screw constructs provided a longer fatigue life, expressed in a significantly higher number of cycles to failure (187,200 ± 18,100) compared to conventional locking screw constructs (128,700 ± 7,000, p = 0.004).

Conclusion

Fatigue performance of locking screws can be ameliorated by the use of angle stable locking screws, being especially important if the nail acts as load carrier and an improved stability during fracture healing is needed.     

Stress analysis of the distal locking screws for femoral interlocking nailing.

In femoral locked nailing, the distal locking screws are vulnerable to mechanical failure. Biomechanical studies have shown that the stress on these screws is substantially affected by the fit of the nail in the medullary canal. In this study, a "closed form" mathematical model based on elastic beam-column theory was developed to investigate how the nail-cortical contact, which was simulated by a linear elastic foundation, affected the stress on the distal locking screws. Providing data for the model was a construct of a fractured femur with an intramedullary locked nail loaded by an eccentric vertical load. The stress on the locking screw was analyzed as a function of the distance from the fracture to the locking screw in the distal fragment under two situations: with and without nail-cortical contact in the distal fragment. With nail-cortical contact, the screw stress decreased as the length of nail-cortical contact and the distance between the distal locking screw and the fracture site increased, but this stress contrarily increased when the nail reached the femoral region at which the screw length increased. The screw stress was much higher without nail-cortical contact than with contact and continued to increase as the nail was inserted further. The mathematical model developed here can be a convenient means of rapid stress evaluation and parametric analysis for locked femoral nailing. It may be used to improve the design of interlocking nails and surgical technique.     

The AO 8mm solid tibial nail is not defunct

The AO 8mm unreamed tibial nail (UTN) is an established implant that has in some publications been associated with high rate of distal locking screw breakage and failure. Larger reamed nails are now increasingly favoured. We have used the 8mm UTN employing all three available distal screws when appropriate and with a restricted initial weight-bearing regimen. Our experience has been satisfactory with 95% union rate and no adverse effect of distal locking screw breakage. This slender nail requires less frequent reaming which may be an advantage in at least some situations. We suggest that it should be considered an alternative to larger reamed nails and can perform satisfactorily with appropriate application.     

内锁钉断裂的生物力学原因分析

从1992年3月至1997年12月,对64例复杂粉碎性股骨骨折作了内锁钉固定。55例得到随访,从3个月到90个月(平均26个月)。共发生4例内锁钉断裂,断钉率为6.3％。经梅花钉固定加植骨3例,记忆合金环抱接骨器固定加植骨1例,骨折均愈合,并且功能3例优良,1例差。断钉发生在术后6月至14月,3例位于骨折远端第一枚横锁螺孔处,1例位于内锁钉中段。断钉原因有:开放穿钉,过度分离骨膜,过早负重及功能锻炼不合适等。另外,股骨远端第一枚横锁螺钉离骨折端太近,此处应力过于集中。预防断裂的方法有尽量闭合穿钉,选择较粗较长的内锁钉,横穿内锁螺钉应稍远离骨折端、避免过早负重及合适的功能锻炼等。     

Implant failure in tibial nailing

Between 1991 and 1995 five hundred and twenty tibial diaphyseal fractures were treated with intramedullary nailing in Northern Ireland. We retrospectively reviewed three hundred and thirty eight patients in three out of the four fracture units in Northern Ireland. Within this group there were three hundred and forty fractures and we identified twenty five episodes of implant failure. This group of patients had a higher percentage of open injuries with a higher degree of comminution and had been treated with smaller diameter nails when compared with the group of patients, who had no implant failure. Failure occurred most frequently at the transverse proximal locking screw when a single screw was used. Fractures in the distal third of the tibia had a higher incidence of nail breakage. We would recommend early elective dynamisation and the use of statically locked larger diameter nails, especially in comminuted or distal third fractures.     

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.     

Intramedullary fixation of forearm fractures with new locked nail

Background:

Lack of availability of interlocked nails made plate osteosynthesis the first choice of treatment of forearm fractures inspite of more surgical exposure, periosteal stripping and big skin incision subsequent scar along with higher risk of refracture on implant removal. We hereby report the first 12 cases with 19 forearm bone fractures internally fixed by indegenous interlocked nail.

Materials and Methods:

Existing square nails were modified to have a broad proximal end of 5.5 mm with a hole for locking screw of 2.5 mm. The nail has a distal hole of 1/1.2/1.5 mm in 2.5/3/3.5 mm diameter nail, respectively. A new method of distal locking with a clip made of k wire is designed. The clip after insertion into the bone and hole in nail and opposite cortex snuggly fits the bone providing a secure locking system. Twelve skeletally mature patients, mean age 32 years (range 24-45 years) with 19 diaphyseal fractures of the forearm were treated with this indigenously made new nail. The patient were evaluated for fracture union, functional recovery and complications. The functional outcome was assessed by disabilities of arm, shoulder and hand questionnaire (DASH score).

Results:

Time to radiographic union ranged between 12 and 28 weeks, with a 100% union rate. Complications were minimal, with mild infection in open fracture (n=1) and delayed union (n=1) in patient with comminuted fracture of the ulna only. The clinical results were excellent. The DASH score ranged between 0 and 36 points.

Conclusion:

This new interlocking nail may be considered as an alternative to plate osteosynthesis for fractures of the forearm in adults. The advantages are benefit of closed reduction, smaller residual scar, reduced cost and early union with allowance of immediate movements.     

Technique for intraoperative determination of femoral rotation with a lateral femur nail (LFN,Synthes, Oberdorf,Switzerland)

Endomedullary femur nails with a head–neck implant offer an up to now unused point of reference for the determination of rotation during osteosynthesis. The lateral femur nail (LFN) or the long Proximal Femur Nail (long PFNA), for example, have recon screws or a blade placed at a 10° angle to the distal locking screw in the transversal plane. If the head–neck implant is inserted properly, the rotation of the femur can be measured with the C-arm taking the hole of the distal locking screw and the posterior condylar tangential line as reference lines. If the posterior condylar tangential line is parallel to the axes of the hole of the distal locking screw, then the rotation or anteversion of the femur is equal to the angle between the head–neck implant and the distal locking screw which is 10° with LFN or long PFNA. Differing rotation angles can be made visible by rotating the C-arm from the axial projection of the distal locking screw up to the posterior condylar tangential line. Three exemplary cases are presented. The recommended method was effective. The rotation of the femur can be measured intraoperatively with this technique and many revisions can be avoided.     

Infra-isthmal fracture is a risk factor for nonunion after femoral nailing: a case–control study

Background

The rates of nonunion after femoral nailing are currently reported to be 4.1–12.5 %. The purpose of this study was to identify the risk factors of noninfected nonunion after femoral nailing, focusing in particular on the effects of the length of the distal main fragment.

Methods

A case–control study was conducted with 105 patients, with a case (nonunion group)–control (control group) ratio of 1:2. The nonunion group (n = 35) comprised patients with consecutive symptomatic nonunions after femoral nailing who were treated in our institute; the control group (n = 70) were matched by age to the nonunion group. Type of fracture, soft tissue injury, length of femur and nail length, incidence of screw breakage, nail diameter, mean length of distal main fragment, and any episode of dynamization were retrospectively examined. Univariate and multivariate analyses were performed to elucidate the risk factors of nonunion after femoral nailing.

Results

Increased risk of nonunion after femoral nailing was associated with (1) open fracture, (2) screw breakage, (3) shorter length of a distal fragment, and (4) any episodes of dynamization. Receiver operating characteristic analysis showed that a distal fragment length of <43 % of the total femur length was the cutoff level for nonunion after nailing. The odds ratio for nonunion was 6.40 (95 % CI 2.70–15.2) when the length of the distal main fragment was <43 % of the femur length. Multivariate logistic analysis revealed that the risk of nonunion after femoral nailing increased (1) with breakage of locking screws (p = 0.0021), (2) with dynamization (p = 0.0029), (3) with a shorter distal fragment length (p = 0.0379), and (4) with an open fracture (p = 0.0397).

Conclusion

The elucidated risk factors of nonunion after femoral nailing were identified as open fracture, infra-isthmal femoral fracture, breakage of locking screw, and inappropriate dynamization. We believe that the surgeon should be consciously aware of the need for additional surgical fixation for the distal fragment when performing femoral nailing of infra-isthmal femoral fractures.     

Biomechanical performance of short and long cephalomedullary nail constructs for stabilizing different levels of subtrochanteric fracture

IntroductionThe aim of this study was to assess biomechanical performance of short and long Cephalomedullary nail constructs consisting of different number of distal screw for stabilizing different levels of subtrochanteric fracture.Materials and methodsThe femur obtained from computed tomography scanner was used to create a transverse fracture at 15 mm (level A), 35 mm (level B), and 55 mm (level C) below the lesser trochanter. Short and long Cephalomedullary nails were virtually inserted to the fractured femur. Four-node tetrahedral element was used to build up finite element (FE) models for biomechanical analysis. The analysis focused on post-operative stage of partial weight-bearing.ResultsStress on the implant localized at the surface between lag screw/nail and distal screw/nail. Short Cephalomedullary nail exhibited higher stress than long Cephalomedullary nail. The stress in short Cephalomedullary nail could be reduced by using two distal screws fixation and the fracture at level A produced less stress than that of level B and C. Either short or long nail with two distal screws is sufficient to withstand the stress magnitude produced from the physiologic load. When single dynamic distal screw was used, stress on implant, elastic strain at fracture gap, and bone stress reached the high values. Elastic strain of the fracture gap at level C were less than that of level A and B, but no statistically significant difference. There was no proximal cancellous bone damage observed from the FE analysis.ConclusionsLong Cephalomedullary nail with at least two distal locking screws remains a proper implant for subtrochanteric fracture fixation in overall locations. However, short Cephalomedullary nail with two distal screws may be a candidate for a high subtrochanteric fracture. Single dynamic screw insertion is strongly not recommended with either short or long nail regarding implant failure.     

Fracture strain and stability with additional locking screws in intramedullary nailing: a biomechanical study

BACKGROUND: We studied the effect of additional locking screws on fracture strain and stability in tibial intramedullary nailing. METHODS: We drilled an additional diaphyseal locking hole into 8-mm solid tibial nails 185 mm from the proximal end of the nail, and locked it proximally and distally. An osteotomy was produced 4.5 cm distal to the additional hole, and the construct loaded axially, in flexion, extension, and torsion. The nails were also tested for their fatigue strength. RESULTS: With the additional locking screw, strain increased proximally during loading in neutral and flexion. Strain decreased on loading in extension. The extra locking screw decreased strain close to the osteotomy site in all loading positions. A significant reduction in angular motion at the osteotomy site occurred with the addition of the extra locking screw. The nails survived the fatigue test, although the stress increased around the additional locking hole CONCLUSIONS: Nails with additional locking options, by altering strain and motion at the fracture site, may have the clinical potential to affect fracture healing.     

Mechanical comparison of standard interlocking,clawed, and expandable wedge locked nail fixations: An experimental and numerical study

IntroductionIntramedullary nailing has been used as a standard in the treatment of the long bone fractures with its clinical and mechanical advantages. However, using distal locking screws has been associated with longer operative times, higher radiation exposure rates, and complications like breakages of distal screw or nail at the screw hole level. Therefore, attempts to eliminate distal locking screws has been always present for intramedullary nail fixation. With a similar purpose, the present study has been carried out to compare mechanical behaviors of intramedullary nail fixations with different distal locking elements.Materials and MethodsIn this study, mechanical behaviors of standard interlocking and clawed nail fixations were compared experimentally in the first part. Six fourth generation Sawbones femurs, which have a simulated subtrochanteric fracture, were divided equally and were fixed with standard interlocking and clawed nails. During axial compression tests, experimental strain measurements were taken from all fixations. After validation of numerical models with using experimental strains and stiffnesses, mechanical behaviors of standard interlocking, clawed, and wedge locked nail fixations were compared numerically under axial compression loads. In numerical comparison, the stress-strain distributions were evaluated.ResultsExperimental results showed that although that there was no significant difference in stiffnesses, standard nail fixation bore two times higher loads than clawed nail fixations. Under loading, decrease in the distance between fracture surfaces was approximately seven times higher in the clawed nail fixation when compared to standard nail fixations. Numerical results showed that wedge locked nail fixation provided equivalent mechanical behavior to standard interlocking nail.DiscussionIn experiments of clawed nail fixation, the high decrease in the distance between fracture surfaces was evidence of the slippage of nail in the medullary canal. For a safe fixation, claws should be deployed when they are completely in contact with the cortical bone, they should be stuck into the bone in a fair amount, and the deployment in the distal third of the femur should be avoided. According to experimentally validated numerical analyses, wedge locked nail fixation may be an alternative for standard interlocking nail fixation if experimental studies support the present results.     

国产带瞄准器交锁髓内钉远端锁钉准确性研究

目的 分析瞄准器引导下交锁髓内钉远端锁钉困难的原因,以提高远端锁钉成功率.方法 自2000年2月至2006年6月拆除有瞄准器的国产股骨交锁髓内钉56根,胫骨交锁髓内钉80根;均采取静力型固定,远近端各2枚锁钉.观察其远端髓内钉钻痕的情况,以分析瞄准器的远端锁钉准确性.结果 本组研究发现瞄准器第一次锁钉的成功率不高,股骨髓内钉瞄准器第一次锁钉的成功率为36%,胫骨髓内钉瞄准器第一次锁钉的成功率为65%.结论 交锁髓内钉远端锁钉困难的原因是多方面的.要提高远端锁钉一次成功率,必须重视瞄准器定位孔偏移问题.     

What is the risk of stress risers for interprosthetic fractures of the femur? A biomechanical analysis

Purpose

Due to increasing life expectancy we see a rising number of joint replacements. Along with the proximal prosthesis in the femur, more and more people have a second implant on the distal ipsilateral side. This might be a retrograde nail or a locking plate to treat distal femur fractures or a constrained knee prosthesis in the case of severe arthrosis. All these constructs can lead to fractures between the implants. The goal of this study was to evaluate the risk of stress risers for interprosthetic fractures of the femur.

Methods

Thirty human cadaveric femurs were divided into five groups: (1) femurs with a prosthesis on the proximal side only, (2) hip prosthesis on the proximal end and a distal femur nail, (3) femurs with both a hip prosthesis and a constrained knee prosthesis, (4) femurs with a hip prosthesis on the proximal side and a 4.5-mm distal femur locking plate; the locking plate was 230 mm in length, with ten holes in the shaft, and (5) femurs with a proximal hip prosthesis and a 4.5-mm distal femur locking plate; the locking plate was 342 mm in length, with 16 holes in the shaft.

Results

Femurs with a hip prosthesis and knee prosthesis showed significantly higher required fracture force compared to femurs with a hip prosthesis and a distal retrograde nail. Femurs with a distal locking plate of either length showed a higher required fracture force than those with the retrograde nail.

Conclusions

The highest risk for a fracture in the femur with an existing hip prosthesis comes with a retrograde nail. A distal locking plate for the treatment of supracondylar fractures leads to a higher required fracture force. The implantation of a constrained knee prosthesis that is not loosened on the ipsilateral side does not increase the risk for a fracture.     

交锁髓内钉在四肢长管状骨骨折中的失误与处理

目的:探讨交锁髓内钉技术的临床疗效及并发症的主要原因和治疗效果。方法:1999年6月-2004年6月采用交锁髓内钉技术治疗四肢长管状骨骨折420例,男310例,女110例;其中股骨干骨折180例,胫腓骨双骨折160例,肱骨干骨折10例,股骨粗隆间骨折60例,股骨髁上骨折10例。年龄20~87岁,平均56岁。发生并发症30例,术中骨折端劈裂2例,钢丝捆扎后完成交锁;异位再骨折2例和术后再骨折2例,更换较长的髓内钉;髓内钉卡在髓腔内进退困难1例,捶击髓内钉尾端拔出髓腔;横向交锁失误12例,其中10例在术中发现退出锁钉重新完成交锁,2例在术后发现应用石膏外固定6周;术后发生主钉断裂2例,二次手术更换较粗的主钉;骨折端不稳定出现反常活动3例,应用石膏外固定6~8周;导针与钻头相嵌顿2例,通过捶击拔出钻头退出导针;腹壁软组织损伤4例进行理疗。结果:本组400例得到6~12个月的随访,骨折全部愈合。膝关节屈曲受限(<90°)4例,肩关节外展上举受限(<90°)1例。结论:交锁髓内钉技术治疗四肢长管状骨骨折临床疗效良好;粗劣的操作技术是发生并发症的主要原因;积极处理并发症可避免功能障碍的发生。     

Modern Retrograde Intramedullary Nails Versus Periarticular Locked Plates for Supracondylar Femur Fractures After Total Knee Arthroplasty

This study purpose is to analyze outcomes of modern intramedullary (IM) nails with a locked distal screw versus periarticular locking plates for peri-prosthetic supracondylar femur fractures in TKA. Ninety-five consecutive fractures in 91 patients were retrospectively reviewed. Fixation included 29 knees with a retrograde IM nail and 66 periarticular locked plates. Six patients died and 4 were lost to follow-up. There were 2 (9%) nonunions in the IM nail group and 12 non-unions/delayed-unions (19%) in the locked plate group (P = 0.34). A mean of 5.0 distal screws was used in locked plates versus 3.8 distal screws in the IM nails (P < 0.001). Despite a greater quantity of screws in the distal fragment, the failure rate of locked plating was twice that of IM nail fixation.     

Treatment of femoral shaft fractures with a titanium intramedullary nail

Ninety-nine femoral shaft fractures were treated with locked intramedullary nails made from titanium alloy. One of the distal interlocking screws failed in six fractures (6%) and both screws failed in two fractures (2%). Delayed union was associated with all of the eight fractures that had locking screw failure. Young, heavier patients who had nails of small diameter had an increased risk of screw failure. Additional surgery was needed when both screws failed. The authors still use this nail, but currently prefer to ream the medullary canal more so that larger nails can be inserted. Decisions concerning weightbearing are made on an individual basis for each patient, and currently full weightbearing is delayed for young, active, and heavy patients. Two distal interlocking screws should be inserted for treatment of femoral shaft fracture when a Ti locked intramedullary nail is used.