Bending and torsional stiffness in cadaver humeri fixed with a self-locking expandable or interlocking nail system: a mechanical study

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

INTRODUCTION

Intramedullary 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 METHODS

In 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.

RESULTS

Experimental 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.

DISCUSSION

In 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.

Comparison of Expandable and Locked Intramedullary Nailing for Humeral Shaft Fractures

Introduction In this study, we clinically and radiologically investigated whether the application of expandable nails for surgical treatment of humeral shaft fractures has an advantage over locked intramedullary nails. Methods Patients treated with intramedullary fixation due to humeral shaft fractures in our clinic were investigated retrospectively. Patients with fractures of type 12A and 12B according to the AO classification in the middle 1/3 shaft region of the humerus were divided into two groups as those receiving fixation with expandable nails and with locked intramedullary nails. The union rate, union time, Q-DASH scores, duration of surgery, and complication rates were statistically compared between the two groups. Results The study included 38 patients with clinical follow-up from among 47 patients; 20 patients received fixation with locked intramedullary nails and 18 with expandable nails. The mean age of the patients was 56.92 (19-91) years and 53% (n=20) were men while 47% (n=18) were women. During statistical evaluation, a statistically significant difference was found between the groups for union (100% and 72.2%) and complication rates (6% and 13%). More union and lower complication rates were found in patients treated with locked intramedullary nails. In comparing the mean of surgical times (71.1 and 30.2 min), expandable nails had a shorter surgical time. However, there was no statistically significant difference between the union time and Q-DASH scores between the two groups. Conclusion Locked intramedullary nails are a better fixation method than expandable nails due to the low complication rate and high rate of union. However, due to shorter surgery time, expandable nailing is an alternative method in limited cases.

Mechanical Behavior of Elastic Self-Locking Nails for Intramedullary Fracture Fixation: A Numerical Analysis of Innovative Nail Designs

Intramedullary nails constitute a viable alternative to extramedullary fixation devices; their use is growing in recent years, especially with reference to self-locking nails. Different designs are available, and it is not trivial to foresee the respective in vivo performances and to provide clinical indications in relation to the type of bone and fracture. In this work a numerical methodology was set up and validated in order to compare the mechanical behavior of two new nailing device concepts with one already used in clinic. In detail, three different nails were studied: (1) the Marchetti-Vicenzi's nail (MV1), (2) a revised concept of this device (MV2), and (3) a new Terzini-Putame's nail (TP) concept. Firstly, the mechanical behavior of the MV1 device was assessed through experimental loading tests employing a 3D-printed component aimed at reproducing the bone geometry inside which the device is implanted. In the next step, the respective numerical model was created, based on a multibody approach including flexible parts, and this model was validated against the previously obtained experimental results. Finally, numerical models of the MV2 and TP concepts were implemented and compared with the MV1 nail, focusing the attention on the response of all devices to compression, tension, bending, and torsion. A stability index (SI) was defined to quantify the mechanical stability provided to the nail-bone assembly by the elastic self-locking mechanism for the various loading conditions. In addition, results in terms of nail-bone assembly stiffness, computed from force/moment vs. displacement/rotation curves, were presented and discussed. Findings revealed that numerical models were able to provide good estimates of load vs. displacement curves. The TP nail concept proved to be able to generate a significantly higher SI (27 N for MV1 vs. 380 N for TP) and a greater stiffening action (up to a stiffness difference for bending load that ranges from 370 Nmm/° for MV1 to 1,532 Nmm/° for TP) than the other two devices which showed similar performances. On the whole, a demonstration was given of information which can be obtained from numerical simulations of expandable fixation devices.

TREATMENT OF HUMERAL SHAFT FRACTURES: ANTEGRADE INTERLOCKING INTRAMEDULLARY NAILING WITH ADDITIONAL INTERLOCKING NEUTRALIZATION SCREWS THROUGH FRACTURE SITE

The aim of this study was to compare union time between two different nail designs for the treatment of humeral shaft fracture, i.e. antegrade interlocking intramedullary nail with and without additional interlocking neutralization screws. The retrospective study included 51 patients treated with antegrade humeral intramedullary nailing between January 2015 and December 2017. The inclusion criteria of the study were proximal and middle third humeral shaft fractures. Fifty-one patients met the inclusion criteria; 23 patients were treated with antegrade intramedullary nail with additional interlocking neutralization screws through fracture site (group A) and 28 patients were treated with antegrade intramedullary nail without additional interlocking neutralization screws (group B). Medical documentation and radiographic images taken preoperatively and postoperatively were reviewed. Radiological union was defined as cortical bridging of at least three of four cortices in two-plane radiographs, with disappearance of the fracture gap. There were no significant differences in union time between the groups (p>0.05). To our knowledge, this is the first report of antegrade interlocking humeral nailing with additional interlocking neutralization screws through fracture site. Hypothetical advantages of fracture gap reduction by additional interlocking neutralization screws to promote union were not confirmed by this first clinical trial.

Biomechanical comparison of humeral nails with different distal locking mechanisms: Insafelock nails versus conventional locking nails

Objective

The aim of this study was to compare the biomechanical resistance to rotational and axial forces of a conventional locking nail with a newly designed intramedullary humeral nail developed for humeral shaft fractures with a secure locking mechanism through the distal part of the nail.

Methods

InSafeLOCK humeral nail system (group 1, TST, Istanbul, Turkey) and Expert humeral nail system (group 2, DePuy Synthes, Bettlach, Switzerland) of the same size (9 × 300 mm) were examined. In total, 24 fourth-generation humerus sawbones were used in the experiment. Osteotomy was performed at the humerus shaft, and a defect was created by removing 1 cm of bone. After pre-loading 5000 cycles at a frequency of 2 Hz and a force of 50–250 N for axial loading and 5000 torsion torques between 0.5 Nm and 6.5 Nm at a 2 Hz frequency for torsional loading, the failure load values of each load were recorded. Distal interlocking was performed with an endopin in group 1, while a double cortex screw was used in group 2.

Results

All samples successfully passed the cyclic loading. The initial and final stiffness values were similar between the groups after axial loading (p = 0.873 and p = 0.522, respectively). The mean axial failure load values in groups 1 and 2 were 2627 ± 164 N and 7141 ± 1491 N, respectively. A significant difference was found in the axial failure load values (p = 0.004). Significant differences were observed between the initial and final torsional stiffness between the two groups (p = 0.004 and p = 0.004, respectively). No significant difference was found in the failure load values after torsional loading (11791 ± 2055 N.mm and 16997 ± 5440 N.mm) (p = 0.055).

Conclusion

These results provide a biomechanical demonstration of the adequate stability of both nails after axial and rotational loading. The reliability of the newly developed InSafeLOCK humeral nail system, which does not require fluoroscopic control and an additional incision for distal locking, supports its use in the clinic.

Biomechanical analysis of a novel plating for intra-articular distal humerus fractures: combined anteromedial and anterolateral plating

Purpose

The traditional strategy for fixing intra-articular distal humerus fractures is double plating placed in an orthogonal or parallel configuration, based on posterior approach. With a combined medial and lateral approach, a novel configuration of plating (combined anteromedial and anterolateral plating) has been used. In this study, we investigated the biomechanical properties of the novel plating by comparing it with orthogonal plating.

Methods

Based on the 3D morphology of a healthy subject’s humerus, the models of simple intra-articular distal humerus fractures were simulated. Two configurations of plating were applied to fix the models: the novel plating (with one plate anteromedially and the other anterolaterally on distal humerus), and orthogonal plating. Stresses, displacement, and stiffness were simulated and calculated under the conditions of axial compression, rotation torsion, bending torsion, and valgus torsion by using finite element analysis.

Results

In all the conditions, the maximal von Mises stresses of the novel plating are similar to those of orthogonal plating, and the patterns of stress distribution are similar between these two configurations. However, the impact of high stresses was weaker on the novel plating. The maximal displacement of the novel plating is smaller than that of orthogonal plating. The stiffness of the novel plating is superior to that of orthogonal plating, with the improvements of 19.4%, 122.7%, 25.0%, and 54.2% in axial compression, rotation torsion, bending torsion, and valgus torsion, respectively.

Conclusions

The novel plating is stronger than orthogonal plating without increasing stress magnitude when fixing simple intra-articular distal humerus fractures, which makes it a feasible alternative. Further biomechanical and clinical studies are needed for a decisive conclusion.

Restoration of Humeral Bone Stock Two Years After Internal Fixation of a Periprosthetic Fracture with a Loose Stem: A Report of Two Cases

CASE

We describe 2 patients who sustained a periprosthetic humeral fracture with a loosened long-stemmed Coonrad-Morrey total elbow prosthesis. As noted in the literature, the success rate for a major revision with use of strut grafts is around 70%; therefore, both cases were managed without revision of the prosthesis. A submuscular locking plate was placed following typical fracture fixation principles. Screws that interfered with the humeral stem and the distal flange stabilized both the distal fragment and the humeral stem.

CONCLUSION

At 2 years postoperatively, both fractures had healed, with increased endosteal bone stock. In each case, the prosthesis was successfully salvaged, and radiographic reconstitution of the implant-bone interface was noted after 2 years.

Intramedullary nailing of humeral diaphyseal fractures. Is distal locking really necessary?

Purpose:

Distal interlocking is regarded as an inherent part of the antegrade humeral nailing technique, but it exposes both the patient and surgeon to radiation, is time consuming, and has a potential risk of damaging neurovascular structures. We have presented our technique of diaphyseal humeral nailing without any distal interlocking in this paper.

Materials and Methods:

We have presented a series of 64 consecutive patients (33 male and 31 female, mean age: 41.5 years) with humeral shaft fractures treated with antegrade rigid intramedullary nailing without distal interlocking following a strict intra and postoperative protocol. According to the AO classification, there were 36 type A fractures, 22 type B, and 6 type C. Nails were inserted unreamed or by using limited proximal reaming and they were fitted as snuggly as possible into the medullary canal. After impaction of the nail into the fossa, we carefully tested rotational stability of fixation by checking any potential external rotation when the arm was slightly turned externally and left to the gravity forces. We were ready to add distal screws, but that was not required in these cases. Follow-up assessment included fracture union, complications and failures, and the final clinical outcome at minimum 2-year follow-up using the parameters of the constant score.

Results:

All fractures, except two, united between the 4^th and 5^th postoperative month. In one case, nail was exchanged with plate, and, in another, a larger nail was used at a second surgery. Shoulder function according to constant score, at a minimum of 2-year follow-up, was excellent or very good in 93.7% of the patients.

Conclusions:

Provided that some technical issues are followed, the method reduces intraoperative time and radiation exposure and avoids potential damage to neurovascular structures.

Short, locked humeral nailing via Neviaser portal: an anatomic study

OBJECTIVE

Supraspinatus tendon trauma may contribute to residual shoulder pain after nail fixation for proximal humeral fractures. Some have proposed a more medial starting point for humeral nail insertion to avoid cuff tendon footprint damage. We hypothesized that percutaneous nail insertion via Neviaser portal would not only be possible, but would avoid tendon trauma, while sacrificing articular cartilage.

MATERIALS AND METHODS

Under c-arm guidance and in percutaneous fashion, we nailed 16 consecutive complete (head and neck, etc, intact) specimen right proximal humeri with locked short humeral nails (Aequalis) via Neviaser portal. Each shoulder was dissected to study the damage to the rotator cuff and long head of the biceps tendons as well as to the articular surfaces. We measured the humeral-thoracic abduction arc before the damaged articular surface contacted the superior glenoid. There were 5 male specimens and 11 female specimens with a mean age of 83 years at the time of death.

RESULTS

We successfully inserted 15 of 16 humeral nails through this percutaneous approach. No supraspinatus tendon or long head of the biceps tendon was damaged. All nails passed entirely through supraspinatus muscle belly. Thirteen of 15 starting points were entirely on articular surface. Mean arc of abduction before superior glenoid contact was 76 degrees (range, 50 degrees-130 degrees). Mean distance from the edge of the articular surface to the most lateral part of the nail insertion was 11 mm (0-25 mm).

CONCLUSIONS

Short, locked humeral nail insertion is possible in percutaneous fashion via Neviaser portal without tendon injury. However, successful insertion comes at the cost of articular cartilage damage.

Treatment of lower extremity long bone nonunion with expandable intramedullary nailing and autologous bone grafting

BACKGROUND

Nonunion of long bones in lower limbs is a common complication of orthopedic trauma that can be extremely debilitating. This retrospective study describes our experience using expandable intramedullary nails and autologous bone grafting in treating lower limb long bone nonunion with bone defects.

METHODS

Nineteen patients (mean age 38.9 years, range 18-61) with lower limb long bone nonunion and defects caused by femoral or tibial fracture types were as follows: A2 (3 femoral, 1 tibial), A3 (1 femoral, 2 tibial), B2 (3 femoral, 4 tibial), and B3 (1 femoral, 4 tibial). Expandable intramedullary nailing and autologous bone (iliac and/or fibular) grafting were used for the treatment. Postoperative bone healing as determined by analysis of standard anteroposterior and lateral X-ray films every 4 weeks. Complications were noted.

RESULTS

The average number of previous surgeries was 1.9 (range 1-4). The mean duration from original injury to treatment was 17.6 months (range 9-40 months). Femoral shaft nonunion healed on average of 26.5 weeks (range 16-60 weeks) after surgery, while tibial shaft nonunion healed on average of 23.6 weeks (range 12-40 weeks) after surgery. Class I healing occurred in all but two patients who experienced chronic postoperative osteomyelitis and delayed wound healing, respectively. Two patients complained of postoperative donor site pain.

CONCLUSIONS

The use of expandable intramedullary nails and autologous bone grafts was an effective method for repair of nonunion of lower limb fractures combining with bone defects with minimal complications.

Biomechanical comparison of expandable and locked intramedullary femoral nails

OBJECTIVES

The expandable intramedullary (IM) nail does not require locking and fluoroscopy use is minimized. However, the lack of cross-locking screws may adversely affect the fixation's rotational stability. The purpose of our study was to compare the rotational stability afforded by an expandable nail with that of a standard locked nail.

METHODS

In a cadaver model of a diaphyseal femoral fracture (OTA type 32-A3), we compared first-generation expandable IM nails with standard locked IM nails in osteoporotic and nonosteoporotic femora (10 pairs each) and second-generation expandable nails with standard locked IM nails only in nonosteoporotic femora (10 pairs). To simulate torsional loads during walking, we applied an external rotation moment of -1 to 10 Nm at 1 Hz to each construct for 5000 cycles. Failure was defined as 15 degrees of rotation at the fracture site. We used McNemar's test to check for significant (P < 0.05) differences in failure between groups.

RESULTS

Of the first-generation expandable nails, 90% failed (9/10 in osteoporotic and 9/10 in nonosteoporotic femora) within the first 1000 cycles. Of the respective locked nails, significantly fewer failed in nonosteoporotic femora than in osteoporotic femora (0/10 and 3/10, respectively). Of the second-generation nails, 8/10 failed within 100 cycles of testing. Of the comparative locked nails, none failed at 5000 cycles.

CONCLUSIONS

We concluded that the expandable IM femoral nail, when tested in purely axial rotation, has poor rotational stability compared with the standard locked IM femoral nail.

Are inflatable nails an alternative to interlocked nails in tibial fractures?

Recently developed inflatable nails avoid reaming and interlocking screws in tibial fractures and reflect a new principle for stabilization of long bone fractures. We asked if the bending stiffness, rotational rigidity, or play (looseness of rotation) differed between an inflatable versus large-diameter reamed interlocked nails, and whether the maximal torque to failure of the two bone-implant constructs differed. In a cadaveric model, we compared the biomechanical properties with those of an interlocked nail in eight pairs of fractured tibial bones. Bending stiffness, rotational rigidity, play (looseness in rotation), and torsional strength within 20 degrees rotation were investigated using a biaxial servohydraulic testing system. For all biomechanical variables, we found a large interindividual variance between the pairs attributable to bone quality (osteoporosis) for both fixation methods. The inflatable nail had a higher bending stiffness, with a mean difference of 58 N/mm, and a lower torsional strength, with a mean difference of 13.5 Nm, compared with the locked nail. During torsional testing we noted slippage between the inflatable nail and bone. We observed no differences in play or rotational rigidity. Given the lower torsional strength we recommend caution with weightbearing until there are signs of fracture consolidation.

A new intramedullary nailing device for the treatment of femoral shaft fractures: a biomechanical study

BACKGROUND

The treatment of choice for early mobilization of femoral fractures is surgery, which traditionally employs plates and screws or intramedullary nails. We examined the biomechanical properties of a new femoral nail system. The new intramedullary propping nailing system, made of a stainless-steel alloy, consists of a nail shaft, inner rod, tensile screw, end cape and two interlocked screws.

METHODS

Intramedullary propping nailing biomechanics was compared with that of the Grosse and Kempf nail when securing transverse fractures in 10 pairs of cadaveric femurs. The axial compressive, bending, torsional stiffness, and strain values were calculated.

FINDINGS

The intramedullary propping nailing system had torsional stiffness (0.50 Nm/ degrees ) and bending stiffness (699.74 and 670.84 N/mm of lateral and frontal bending, respectively) comparable with the Grosse and Kempf nail (0.35 Nm/ degrees , 644.85 and 606.32 N/mm of lateral and frontal bending, respectively). Intramedullary propping nailing system produced a significantly higher compressive stiffness (1.67 and 1.50 x 10(6) N/mm, respectively) than the Grosse and Kempf nail in the medial and anterior aspects (0.86 and 1.32x10(6)N/mm, respectively). Although no significance was found in comparison with Grosse and Kempf of the strain of each aspect, intramedullary propping nailing system yielded a significantly better-distributed strain (F=1.007, P=0.401).

INTERPRETATION

Biomechanically, the intramedullary propping nailing system is safe and able to provide good abutment of the nail to the bone. The intramedullary propping nailing system produces a more extensive and tight contact between the nail and bone than the application of Grosse and Kempf nail.

Extreme complications of Fixion nail in treatment of long bone fractures

The authors present their experience related to extreme complications in treatment of diaphyseal fractures of the long bones with application of the Fixion expansion intramedullary nail in a total of 48 surgeries. We have encountered six (12.5%) extreme complications in the management of fractures of 3 humeral, 2 tibial, and 1 femoral bones during its application procedure and postoperative follow-up. Of six cases, two with humeral and tibial fractures developed nonunion and rotational instability because of failure of inflation of the Fixion nail. One of the Fixion nail in humerus was broken spontaneously, and one of the Fixion nail deflated at the follow-up and pseudoarthrosis developed in this patient. In a patient with osteogenesis imperfecta, during the inflation of the nail for the treatment of femur fracture, a new longitudinal fracture occurred and conventional non-locking intramedullary nail was inserted. In a patient with a tibia fracture that was treated with the Fixion nail, new fracture occurred due to its bending after weight bearing in the postoperative period. The Fixion nail application is a new technique for the intramedullar fixation of long bones. It is considered as an effective method for the selective fracture types of long bones. Application may need special training. Since the Fixion has not got rotational stability and rigidity as conventional nailing systems, bending and breaking of the nail may occur during postoperative period in patients with over obesity and hyperactivity. In patients with osteogenesis imperfecta, it may not be the first choice as a nailing system.

Biomechanical Evaluation of an Expandable Nail for the Fixation of Midshaft Fractures

BACKGROUND

The objective of this study was to compare the torsional stability of diaphyseal long bone fractures fixed with either a Fixion nail (DiscOTech, Monroe Township, NJ) or a standard locked Zimmer M/DN locked nail (Zimmer, Warsaw, IN).

METHODS

Two fracture models were used to evaluate the bone-implant constructs. A transverse osteotomy was created in all tibiae, and a spiral fracture was created in all humeri. Paired specimens were randomly assigned to receive either a Fixion or Zimmer M/DN locked nail. Each implanted construct was cyclically loaded in torsion, and construct stiffness for each fracture type and each bone computed from the resulting load-displacement curves.

RESULTS

Performance of the Fixon nail in the tibial transverse model was variable: 2 of 10 implanted constructs failed during testing, and average construct stiffness was significantly greater for the Zimmer nail. No significant difference was found between the stiffness of the Zimmer M/DN and Fixion implanted humeral constructs either with or without the interlock.

CONCLUSIONS

Fracture type significantly affected the performance of the Fixion nail. Our results suggest that the Fixion nail is most suitable for use in fractures where torsional loads across the fracture site are shared between the nail and the bony ends of the fracture, as in a spiral fracture.

Intramedullary Nailing of Humeral Head and Humeral Shaft Fractures

There is an increasing interest in intramedullary nailing for humeral fractures. Starting with diaphyseal fractures, now also proximal metaphyseal fractures of the humerus can be nailed with satisfying results. Basic ideas for humeral nailing are less invasive approaches to the humerus, less soft tissue damage, e.g. lower rates of radial nerve palsy, closed reduction and the biomechanical aspects of a central implant with elastic fixation properties. Nailing of diaphyseal humeral shaft fractures is an equivalent alternative to plating; nailing of proximal metaphyseal humeral fractures is still new and needs more reliable scientific data to clear its advantages compared to other fixation techniques. Nailing of distal metaphyseal humeral fractures is no serious option at the moment. Angular stable interlocking systems show better fixation qualities for proximal fractures or fracture components. Although in very osteoporotic bone cutouts are registered. Static interlocking is advisable. High torsional stability of the fracture fixation has to be achieved, since significant torsional load occurs during the usual movement of the upper limbs. As there is an important learning curve, possible complications of intramedullary nailing have to be kept in mind and avoided by a careful operation technique.

Expandable intramedullary nailing for tibial and femoral fractures: a preliminary analysis of perioperative complications

OBJECTIVE

To report the results of using the expandable nailing system in the treatment of femoral and tibial shaft fractures.

DESIGN

Prospective, cohort series.

SETTING

Two level-1 university trauma centers.

PARTICIPANTS

Forty-eight patients with acute, traumatic diaphyseal fractures of the tibia or femur.

INTERVENTION

Internal fixation of lower extremity long bone fractures using expandable intramedullary nailing.

MAIN OUTCOME MEASUREMENTS

Perioperative complications and time to healing.

RESULTS

Forty-nine long bone fractures were treated: 22 femoral fractures (OTA classification: 4 type A1, 6 A2, 7 A3, 1 B1, and 4 B2) and 27 tibial fractures (OTA classification: 4 type A1, 11 A2, 9 A3, 0 B1, and 3 B2). There were 13 open fractures and 37 closed fractures. Healing occurred in 37 (75%) fractures without additional interventions. There were 2 tibial delayed unions and 1 femoral and 1 tibial nonunion. Five tibial shaft fractures and 6 femoral fractures shortened by 1.0 cm or more postoperatively. In 3 tibias and 4 femurs, shortening occurred after fractures judged to be length-stable became unstable because of fracture propagation during nail expansion. Five tibias and 3 femurs were converted to standard locked nails because of shortening. The average time to healing, excluding nonunion, was 15 weeks in the tibia and 16 weeks in the femur. The expandable nail resulted in an unplanned reoperation in 12 cases (25%).

CONCLUSION

We found a high complication rate because of shortening, which was independent of fracture classification. Consequently, we cannot recommend the use of an unlocked, expandable nail in diaphyseal fractures of the femur or tibia.