Biomechanical comparison of bending and torsional properties in retrograde intramedullary nailing of humeral shaft fractures.

OBJECTIVE: To establish whether the bending and torsional stiffness of an implanted nail are influenced by nail design and nail-bolt interface, this study compared two implanted retrograde nail systems: the AO/ASIF unreamed humeral nail (UHN) and the Russell-Taylor (RT) nail. DESIGN: Pair randomization. SETTING: Mechanical laboratory testing. SPECIMENS: Twelve pairs of freshly harvested cadaveric humeri. METHODS: Transverse fractures were simulated with a standardized midshaft osteotomy and a three-millimeter gap. Both nails were proximally and distally interlocked. The RT nail has a single interlock at its base and tip. The UHN has double interlocking both proximally and distally. The screw hole design of the RT nail features slots, whereas the UHN has round screw holes. MAIN OUTCOME MEASURES: Anteroposterior and mediolateral bending stiffness and torsional stiffness. RESULTS: The RT nail showed higher bending stiffness in anteroposterior and mediolateral bending. Large differences were seen in the torsional characteristics: for the first 30 degrees, the RT nail showed a much lower resistance against torsion than the UHN. Analysis of variance of stiffness at four, six, and eight newton-meters showed statistical significance (p < 0.0001). Torsional stiffness, defined as the slope of a straight line approximated to between 75 and 100 percent of the maximum torque, was very similar in both nails. CONCLUSION: The torsional differences between the two nail systems are attributable to the nail-bolt interface of the RT nail. This dynamic system allows a clinically relevant degree of movement. The greater resistance to rotatory forces of the UHN is explained by the fact that the interlocking at its tip and base creates a static rather than a dynamic system.     

Fixation of three-part proximal humeral fractures: a biomechanical evaluation

OBJECTIVES: To examine the biomechanical stability of three constructs currently used for the management of three-part proximal humerus fractures. Tension band wires (TBW) with supplemental Enders nails, modified cloverleaf plate and screws, and intramedullary (IM) nailing with proximal and distal interlocks were tested to determine relative stability. DESIGN: A reproducible three-part fracture was made in fresh-frozen stripped proximal humeri. The fracture was stabilized using TBW/Enders nail (n = 6), plate/screws (n = 5), or IM nailing (n = 5). MAIN OUTCOME MEASUREMENTS: Mechanical testing was performed with a small preload followed by deflection of five millimeters at a rate of one millimeter per second in flexion, extension, and varus and valgus relative to the humeral shaft. A load-displacement curve was obtained. Torsional testing was performed in internal and external rotation, and torque-rotation curves were recorded. RESULTS: In cantilever bending, the plate/screws construct and the IM nail construct were superior to the TBW/Enders nail construct for all parameters except extension. There was no statistically significant difference between the IM nail and the plate/screws groups. Torsional stiffness testing revealed that the plate/screws and the IM nail were superior to the TBW/Enders nail construct. There was no statistical difference between the IM nail and the plate/screws groups. CONCLUSIONS: In a cadaveric model of three-part proximal humerus fractures stripped of soft tissue, plate/screws fixation and IM nailing provide greater torsional and bending stiffness than does fixation with TBW/Enders nail. There was no statistically significant difference in torsional or bending stiffness between IM nailing with interlocks and plate/screws fixation in this model.     

Biomechanical comparison of methods of fixation of a midshaft osteotomy of the humerus

Using paired humeri with a midshaft osteotomy, the biomechanical stiffness of four intramedullary internal fixation devices were compared with each other, a dynamic compression plate, and with the intact bone. In posterior and lateral bending and in torsion, flexible intramedullary pin fixed humeri (Enders and Hackethal) performed similarly and were less stiff than intact specimens were. Interlocking intermedullary nail constructs (Russell-Taylor and Seidel) also tested similarly to each other, and were stiffer than the flexible pins in all bending tests. Compared with the intact humerus, interlocking nails were stiffer in torsion, but in bending they more closely simulated the stiffness of the bone.     

Biomechanik der Verriegelungsmarknagelung bei Oberarmschaftfrakturen Vergleichsuntersuchungen zweier Marknagelsysteme und des Effekts der interfragmentären Kompression bei unaufgebohrtem Humerusnagel

In this biomechanical study the implanted Unreamed Humeral Nail (UHN) has been tested concerning bending and torsional stiffnesses. In literature other intramedullary implants have been criticized for insufficient rotatory stability especially in transverse and short oblique fractures of the humeral shaft. This study examined, whether the implanted UHN, as well as the UHN implanted with interfragmentary compression through a specific compression device, is able to augment torsional stiffness significantly. To evaluate bending and torsional stiffnesses, the UHN has been compared biomechanically to the Russell-Taylor humeral nail (RT) in paired mid-shaft osteotomized cadaveric humeri. Identic paired comparison has been performed with the UHN without and UHN with interfragmentary compression. In anterior-posterior, as well as medio-lateral direction stiffness under four-point-bending is significantly higher in stabilizing with the RT. Under torsional loading with moments of 4 Nm, 6 Nm and 8 Nm the UHN reached more than the double torsional stiffness. The RT, which is only dynamically interlocked, owns a high initial "play" between bolts and nail itself. Through additional interfragmentary compression stiffness of the UHN under four-point-bending in anterior-posterior, as well as medio-lateral direction augments significantly. Also under torsional loading with moments of 4 Nm, 6 Nm und 8 Nm torsional stiffness increases with interfragmentary compression significantly. In comparison to other biomechanical studies of different authorship it is clear, that this statically interlocked intramedullary nailing of the humeral shaft is superior to non-statically interlocked types of nailing concerning their stabilizing potency in torsion and serves especially for fracture types, which are critically under rotation, as transverse or short oblique humeral shaft fractures.     

Two-part surgical neck fractures of the proximal part of the humerus. A biomechanical evaluation of two fixation techniques

BACKGROUND: Successful internal fixation of fractures of the surgical neck of the humerus can be difficult to achieve because of osteopenia of the proximal aspect of the humerus. The purpose of this study was to compare the biomechanical stability of a proximal humeral intramedullary nail and a locking plate for the treatment of a comminuted two-part fracture of the surgical neck in a human cadaver model. METHODS: Twenty-four cadaveric humeri were instrumented with use of either a titanium proximal humeral nail (PHN) or a 3.5-mm locking compression plate for the proximal part of the humerus (LCP-PH). The specimens were matched by bone mineral density and were separated into four experimental groups with six humeri in each: PHN bending, LCP-PH bending, PHN torsion, or LCP-PH torsion. Comminuted fractures of the surgical neck were simulated by excising a 10-mm wedge of bone. Bending specimens were cyclically loaded from 0 to 7.5 Nm of varus bending moment at the fracture site. Torsion specimens were cyclically loaded to +/-2 Nm of axial torque. The mean and maximum displacement in bending, mean and maximum angular rotation in torsion, and stiffness of the bone-implant constructs were compared. RESULTS: In bending, the LCP-PH group demonstrated significantly less mean displacement of the distal fragment than did the PHN group over 5000 cycles (p = 0.002). In torsion, the LCP-PH group demonstrated significantly less mean angular rotation than did the PHN group over 5000 cycles (p = 0.04). A significant number of specimens in the PHN group failed prior to reaching 5000 cycles (p = 0.04). The LCP-PH implant created a significantly stiffer bone-implant construct than did the PHN implant (p = 0.007). CONCLUSIONS: The LCP proximal humeral plate demonstrated superior biomechanical characteristics compared with the proximal humeral nail when tested cyclically in both cantilevered varus bending and torsion. The rate of early failure of the proximal humeral nail could reflect the high moment transmitted to the locking proximal screw-bone interface in this implant. CLINICAL RELEVANCE: The high failure rate in torsion of the proximal humeral nail-bone construct is concerning, and, with relatively osteoporotic bone and early motion, the results could be poor.     

Expandable nail system for osteoporotic humeral shaft fractures: preliminary results

BACKGROUND: Conventional nails rely on interlocking screws for axial and rotational stability. Such screws have poor fixation in patients with poor bone quality (osteopenia). The Fixion nail does not depend on interlocking screws-axial and rotational stability is instead achieved by nail expansion. Therefore, this nail may be better suited for patients with poor bone quality who require humeral stabilization. METHODS: The system was used to manage 25 unstable humerus shaft fractures in osteoporotic bone. An antegrade approach was used in 18 patients and a retrograde approach was used in 7 patients. RESULTS: There were no intra- or postoperative complications. Postoperatively, all fractures were stable and had healed by week 16. The mean operative time was 35 +/- 10 minutes (+/- SD) including 1.5 +/- 0.5 minutes of fluoroscopy time. CONCLUSION: The results of this study show that use of this nailing system is associated with minimal complications, predictable fracture healing, and excellent functional outcomes in a cohort of elderly patients with poor bone quality and humeral shaft fractures requiring stabilization. Further confirmation by larger prospective trials is necessary.     

Mechanical properties of different combinations of flexible nails in a model of a pediatric femoral fracture

Flexible nailing of pediatric femoral shaft fractures is based on the principle of using two C-shaped nails to create six points of fixation. However, clinical studies using various nail combinations demonstrate similar outcomes. This study aimed to compare the mechanical properties of different nail combinations by testing them in a model of a child's midshaft femoral fracture. The two C-shaped nails were compared with two straight nails and with paired S- and C-shaped nails. The constructs were tested in four-point bending and torsion. Graphs of the data were produced, from which the bending and torsional stiffness of the constructs was calculated. The results showed that there was no significant difference between the mechanical properties of the three different constructs. The conclusion is that any of the tested nail combinations can be used to treat a midshaft fracture of the femur in a child.     

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.     

A mechanical comparison between conventional and modified angular plates for proximal humeral fractures

The objective of this study is to present a modified angular blade plate for fixing 2-part and even 3-part fractures of the proximal humerus, as well as the results of the comparative mechanical test between the conventional angular blade plate and this new modified plate. The plates were tested in flexion and rotational trials in a wooden model that simulated a 2-part humeral fracture of the proximal extremity. The results (mean +/- SD) of bending strength and stiffness obtained after testing showed findings of 601 +/- 349 N and 0.5 +/- 0.2 N/mm, respectively, for the conventional plate and 4005 +/- 164 N and 3.9 +/- 0.7 N/mm, respectively, for the modified plate. The torsional stiffness test showed findings of 1.26 +/- 0.09 KN.mm degrees for the conventional plate and 1.74 +/- 0.21 KN.mm degrees for the modified plate. The test of torsional moment showed findings of 57.0 +/- 7.6 KN.mm for the conventional plate and 115.2 +/- 9.3 KN.mm for the modified plate. The test of angular displacement at the torsional moment showed findings of 50.8 degrees +/- 7.2 degrees for the conventional plate and 70.2 degrees +/- 2.6 degrees for the modified plate. The results of the mechanical trials of flexion and rotation were superior for the modified angular blade plate compared with the conventional angular blade plate.     

Expandable intramedullary nails for humeral fractures: a systematic review of clinical and radiological outcomes

The Fixion^? system (Disc-O-Tech Medical Technologies, Herzeliya, Israel), which is currently the only expandable nailing system available for use in the humerus, has a number of purported advantages over the standard locked humeral nail, including a reduction in operating and fluoroscopy time since locking screws are not required. A systematic review was undertaken of all published (AMED, CINAHL, EMBASE and Medline via the Ovid platform) and unpublished or grey literature research databases from inception until 1st December 2010. Demographic data, clinical and radiological outcomes, and complications were extracted from each study by two independent investigators, and each study underwent independent critical appraisal using the CASP appraisal tool. Thirteen studies were deemed eligible for review, identified from a total of 154 citations. These included a total of 176 patients with 180 fractured humeri treated with expandable nails. Overall, 7.8% of humeral fractures treated with an expandable nail went on to non-union. Intra- and post-operative device failure rate was found to be 1.1 and 2.8%, respectively. These data compare favourably to published data on the outcome of locked humeral nails. However, there were numerous methodological flaws in the current evidence base; there were no comparative studies, treatment groups were heterogeneous, and there was no blinding of assessors or patients. Initial data indicate that the expandable humeral nail may be an acceptable form of treatment for humeral fracture or impending fracture, but high-quality comparative studies are needed to confirm these findings.     

The effect of concurrent fibular fracture on the fixation of distal tibia fractures: a laboratory comparison of intramedullary nails with locked plates

OBJECTIVE: To compare the fixation stability of intramedullary nails to that of locked plates for the treatment of distal metaphyseal tibia and fibula fractures. METHODS: A simulated, distal metaphyseal tibia fracture was created in 8 pairs of cadaveric tibia-fibula specimens. One of each pair was treated using an intramedullary nail (Trigen IM Nail System; SN Richards, Memphis, TN) and the other with a locked plate (Peri-Loc Periarticular Locked Plating System; SN Richards). Each specimen was vertically loaded to 250 N in central, anterior, posterior, medial, and lateral locations; loaded to 250 N in cantilever bending in anterior to posterior and posterior to anterior directions; and loaded to 250 N mm in torsion. Load-displacement curves were generated to determine the construct stiffness for each loading scenario, with comparisons made between the 2 treatment groups. Each specimen was then cyclically loaded with 750 N vertical loads applied for 10, 100, 1000, and 10,000 cycles. Measurements of fracture displacements were made and compared between treatment groups. A fibular osteotomy was then created in each specimen at the same level as the tibia fracture to simulate a same-level tibia-fibular fracture. Torsional stiffness assessment and cyclic vertical loading for 10, 100, 1000, and 10,000 cycles were repeated and fracture displacement measurements were again obtained. RESULTS: The locked plate construct was stiffer than the intramedullary nail construct for central, anterior, and posterior loading scenarios (P < 0.005, P < 0.03, and P < 0.02, respectively). The intramedullary nail construct was stiffer than the locked plate construct for both anterior to posterior and posterior to anterior cantilever bending (P < 0.03 and P < 0.02, respectively). No statistically significant difference in stiffness was noted between treatment groups for medial and lateral vertical loading or for torsional loading (P = 0.09, P = 0.32, and P = 0.84, respectively). There was no significant difference between treatment groups with respect to fracture displacement after cyclic vertical loading. After creation of the fibular osteotomy fracture, construct displacements after 1000 and 10,000 cycles significantly increased and torsional stiffness significantly decreased for both treatment groups. The locked plate constructs had significantly less displacement after cyclic loading of 1000 and 10,000 than the locked nail constructs (P < 0.001 and P < 0.0001, respectively). Locked plate constructs were stiffer in torsion after osteotomy than the intramedullary nail constructs (P < 0.05). CONCLUSION: This study demonstrated that, in the treatment of distal metaphyseal tibia fractures, locked plates provided more stable fixation than intramedullary nails in vertical loading but were less effective in cantilever bending. An intact fibula in the presence of a distal tibia fracture improved the fracture fixation stability for both treatment methods. In fracture patterns in which the fibula cannot be effectively stabilized, locked plates offer improved mechanical stability when compared with locked intramedullary nails.     

可膨胀自锁型髓内钉治疗肱骨干骨折

[目的]探讨闭合复位、可膨胀自锁型髓内钉固定在肱骨干骨折治疗中的临床效果.[方法]自2006年9月-2008年12月,应用可膨胀自锁型髓内钉治疗肱骨干骨折10例,其中男6例,女4例,年龄21～75岁,平均38.3岁.骨折按AO分类:12A1型3例,12A2型5例,12A3型2例,均采用闭合复位,顺行插钉.[结果]10例患者均获随访,时间9～22个月,平均随访时间14个月.10例患者均获得临床骨性愈合,平均愈合时间为11周.肘关节功能正常.肩关节功能按Neer疗效评分系统评定:优7例,良2例,可1例,优良率为90.0%.术后无感染、脂肪栓塞、骨折延迟愈合、不愈合、肢体短缩和旋转畸形等并发症的发生.[结论]可膨胀自锁型髓内钉治疗肱骨干骨折具有微创、操作简单、固定坚强、对骨折局部血供破坏小、取出方便等优点,是一种疗效满意的方法.     

Biomechanical comparison of flexible stainless steel and titanium nails with external fixation using a femur fracture model

There are several options available for surgical stabilization of pediatric femoral shaft fractures. The purpose of this study was to compare the stability afforded by Ender stainless steel nails, titanium elastic nails, and one-plane unilateral external fixators for the fixation using a synthetic adolescent midshaft femur fracture model. The anterior-posterior (sagittal plane) bending, lateral (coronal plane) bending, torsional, and axial stiffness values were calculated using 6 different fixation configurations. These included pairs of 3.5-mm-diameter Ender nails with and without distal locking, 3.5- and 4.0-mm-diameter titanium elastic nails as well as single- and double-stacked monolateral external fixators. Eight synthetic femur models, 4 each with simulated transverse and comminuted fracture patterns, were sequentially tested for stability afforded by the various fracture fixation configurations. External fixation exhibited significantly greater control of anterior-posterior angulation compared with all flexible-nailing systems. Although Ender nails were slightly superior to titanium nails in control of sagittal plane angulation, this was not statistically significant. Compared with the external fixation constructs, all 4 flexible nail constructs demonstrated higher torsional stability. For prevention of axial shortening, all fixation methods were similar for the transverse fracture pattern, whereas external fixation was superior to flexible nails in the comminuted fracture model. No significant benefit was demonstrated with double stacking of external fixators. These findings may help guide clinicians choose the optimal fixation method for treatment of pediatric femoral shaft fractures.     

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° 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. Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. Each author certifies that his or her institution has approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.     

Antegrade versus retrograde titanium elastic nail fixation of pediatric distal-third femoral-shaft fractures: a mechanical study

OBJECTIVES: To determine whether the stability of elastic stable intramedullary nail (ESIN) constructs differ in terms of antegrade versus retrograde insertion for the fixation of pediatric distal-third transverse femoral-shaft fractures. METHODS: Ten synthetic composite adolescent-sized femur models and 20 flexible titanium (Ti) intramedullary (IM) nails were divided into antegrade and retrograde groups. A simulated transverse fracture was created in each of 10 models in the distal-third region of the shaft (more precisely near the distal fifth). The fractures were then stabilized with ESIN. The specimens were subjected to four-point bending and then axial torsion. Flexural forces were applied to the medial aspect of the model across the fracture site at a rate of 0.05 mm/s to a maximum displacement of 3.7 mm (7 degrees). Torsional moments were applied to the distal aspect of the model in internal and external rotation at a rate of 0.75 degrees/s to a maximum of 10 degrees. Loads and stiffnesses were determined between consistent displacement limits; differences were compared using t tests (alpha = 0.05, two tailed). RESULTS: Flexural stiffness was significantly greater in the retrograde group (350 +/- 72 N/mm) compared with antegrade (195 +/- 95 N/mm; P = 0.02). A 66-kg load placed across the fracture displaced the site 3.7 mm for the antegrade group, whereas the retrograde group required a load 89% greater (125 kg). Although torsional stiffness tended to be greater in the antegrade group, the differences were not statistically significant (P = 0.2). CONCLUSIONS: Although the recommendation for distal-third femur fractures is antegrade nail insertion, this study demonstrates that given satisfactory cortical starting points in the distal fragment, retrograde insertion provides greater stability. These mechanical testing data are the first to address this specific fracture scenario and may aid surgical decision making.     

Expandable intramedullary nails in lower limb trauma: a systematic review of clinical and radiological outcomes

This study systematically reviews the evidence-base for the use of expandable nails in the treatment of acute diaphyseal fractures of the lower limb. Both electronic and hand searches were undertaken of the published and grey literature to 1 December 2011. A total of 154 citations were identified, of which 15 were deemed suitable and assessed with the Critical Appraisals Skills Programme tool. A total of 625 nailing procedures were performed in 620 patients: 279 femoral and 346 tibial nails. The expandable nail was found to be significantly quicker to insert than interlocked nails (p < 0.05), and the total incidence of non-union or other complication was 13 and 14 % for expandable femoral and tibial nails, respectively. Notable complications with the expandable nail included fracture propagation on nail inflation in 2.5 % and post-operative shortening in 3.3 %. Device failure secondary to problems with the expansion mechanism was seen in 2.9 %. The rate of non-union and infection following expandable nailing was 3.1 and 1.4 %, respectively. Despite promising initial results, there remains a paucity of good quality studies to support the use of expandable nails over interlocked nails for the treatment of acute diaphyseal fractures of the lower limb.     

Compression-locked nailing of the humerus: a mechanical analysis

BACKGROUND: In the treatment of humeral fractures, reamed nailing and compression have been reported to give higher stability. In this cadaver study, we compared the Unreamed Humeral Nail (UHN) with the (reamed) Telescopic Locking Nail (TLN) to find out whether any differences exist concerning bending and rotational stability, both with and without compression. METHODS: Nails were tested in a paired set-up with 8 pairs of fresh frozen cadaveric humeri. The nail-bone constructs were submitted to axial distraction to test compression, four-point bending and torsion. After creating a bone defect simulating an unstable fracture, bending and torsional tests were run again RESULTS: After cyclic loading, distraction under compression with the TLN was significantly less than with the UHN: 0.10 (SD 0.06) vs. 0.31 (SD 0.18) mm (difference = -67%, 95% CI = -84% to -37%; p = 0.01). In bending, the constructs with TLN under compression were stiffer than those with the UHN: 0.96 (SD 0.25) vs. 0.80 (SD 0.25) kN/mm (difference = 0.16, 95% CI = 0.07 to 0.25; p = 0.01). In torsion and with a bone defect, no significant differences were found. INTERPRETATION: Both nails are capable of resisting physiological forces acting on the humerus. The constructs with the TLN under compression are more stable in bending. Compression with an axial set screw is the more stable option.     

Is Humeral Segmental Defect Replacement Device A Stronger Construct than Locked IM Nailing?

Intramedullary (IM) nailing is currently the most common method for treating patients with impending pathologic humeral fractures; however, this treatment is associated with known complications primarily owing to violation of the rotator cuff during insertion. A better option is needed. To determine if a humeral segmental replacement prosthesis would provide a stronger construct compared with an IM nail in this setting, we compared the mechanical properties of these two devices in a cadaver model simulating an impending pathologic fracture. In each of nine matched pairs of fresh human humeri one was randomly selected to undergo a 50% lateral middiaphyseal defect simulating an impending pathologic fracture and subsequent fixation with an IM nail and bone cement. The contralateral humerus underwent fixation using a humeral segmental defect prosthesis. We determined T-scores using DEXA. Each specimen subsequently was tested in torsion to failure. Peak torque and peak rotation at failure were greater for the prosthesis specimens whereas torsional stiffness was greater for the IM nail specimens. We found a linear relationship between peak torque and T-score for each device with the slopes of the lines suggesting the construct with the prosthesis can withstand greater forces than the IM nail and the differences between devices were greater in weaker bones.     

Biomechanical evaluation of retrograde docking nailing to a total hip arthroplasty stem in a periprosthetic femur fracture model

IntroductionSlotted nails allow a connection to a total hip arthroplasty (THA) stem and act as intramedullary load carrier. This study compares construct stiffness, cycles to failure and failure load between a retrograde slotted femur nail construct docked to a THA stem and a lateral locking plate in a human periprosthetic femur fracture model.Materials and methodsIn seven pairs of fresh-frozen human anatomic femora with cemented THA, a transverse osteotomy was set simulating a Vancouver type B1 fracture. The femora were instrumented pairwise with either a retrograde slotted nail coupled to the prosthesis stem, or a locking plate plus a locking attachment plate. Four-point mediolateral bending, torsional and axial bending construct stiffness was investigated via non-destructive tests. Cyclic testing under progressively increasing physiologic loading was performed at 2 Hz until catastrophic construct failure.ResultsMediolateral bending stiffness did not differ significantly between the two groups (P=0.17) but exhibited a biphasic profile with significantly increased stiffness in both groups (P<0.01). Nail constructs provided a significantly lower torsional stiffness (0.49 ± 0.66 Nm/°) than plate constructs (1.70 ± 0.86 Nm/°), P=0.03. Axial bending stiffness did not differ significantly between the groups (Nail: 605 ± 511 N/mm; Plate: 381 ± 428 N/mm), P=0.61. Cycles to failure and failure load were significantly higher for the plate constructs (25’700 ± 8’341; 3’070 ± 1334 N) compared with the nail constructs (20’729 ± 7’949; 2’573 ± 1295 N), P=0.04.ConclusionThe docking nail construct provides an intramedullary fixation with connection to the prosthesis stem; however, it is biomechanically weaker in stable fractures compared to the plate construct.     

可膨胀股骨近端钉和DHS治疗股骨转子间骨折疗效比较

目的 比较可膨胀股骨近端钉和DHS在治疗股骨转子间骨折中的优缺点,探讨股骨转子间骨折内固定选择的策略.方法 总结自1997年5月至2006年11月在浙江省人民医院骨科接受股骨转子间骨折可膨胀股骨近端钉和DHS固定手术病例总计223例.DHS(Dylmac Hip Screw)固定组(DHS A组)165例,可膨胀股骨近端钉组(Proximal Femoral Nail PFN,B组)58例.比较两组在手术时间、术中出血量、术中X线暴露次数、术后引流量、骨折临床愈合时间、术后功能评分、手术并发症等方面的结果.结果 A组和B组在手术时间、术中出血量、术中X线暴露次数、术后引流量、骨折临床愈合时间、术后功能评分等方面等方面差异有统计学意义(P＜0.01).B组较A组手术时间缩短、术中出血量和术后引流量减少、骨折临床愈合时间缩短、术后功能恢复改善,但术中X线暴露次数明显增加.两组手术并发症的差异有统计学意义(P＜0.05).结论:可膨胀股骨近端钉在治疗股骨转子间骨折中具有一定的优势.