The Seidel nail revisited- an evaluation of recent design change

This study evaluated a recent design change of the distal locking mechanism of the Seidel nail. The distal expansion bolt has been modified to incorporate a swagged rotating collar. The torque requirement for distal locking was measured for the original and new bolt design using a composite bone humeral model. Ten of each screw type were tested. The torque requirement for distal locking was less in the original bolt design. However the torque transmission is smoother in the new bolt design making appreciation of adequate locking more reliable.     

Effect of fibular plate fixation on rotational stability of simulated distal tibial fractures treated with intramedullary nailing

BACKGROUND: The effect of an intact fibula on rotational stability after a distal tibial fracture has, to the best of our knowledge, not been clearly defined. We designed a cadaver study to clarify our clinical impression that fixation of the fibula with a plate increases rotational stability of distal tibial fractures fixed with a Russell-Taylor intramedullary nail. METHODS: Seven matched pairs of embalmed human cadaveric legs and sixteen fresh-frozen human cadaveric legs, including one matched pair, were tested. To simulate fractures, 5-mm transverse segmental defects were created at the same level in the tibia and fibula, 7 cm proximal to the ankle joint in each bone. The tibia was stabilized with a 9-mm Russell-Taylor intramedullary nail that was statically locked with two proximal and two distal screws. Each specimen was tested without fibular fixation as well as with fibular fixation with a six-hole semitubular plate. A biaxial mechanical testing machine was used in torque control mode with an initial axial load of 53 to 71 N applied to the tibial condyle. Angular displacement was measured in 0.56-N-m torque increments to a maximal torque of 4.52 N-m (40 in-lb). RESULTS: Initially, significantly less displacement (p < or = 0.05) was produced in the specimens with fibular plate fixation than in those without fibular plate fixation. The difference in angular displacement between the specimens treated with and without plate fixation was established at the first torque data point measured but did not increase as the torque was increased. No significant difference in the rotational stiffness was found between the specimens treated with and without plate fixation after measurement of the second torque data point (between 1.68 and 4.48 N-m). CONCLUSIONS: Fibular plate fixation increased the initial rotational stability after distal tibial fracture compared with that provided by tibial intramedullary nailing alone. However, there was no difference in rotational structural stiffness between the specimens treated with and without plate fixation as applied torque was increased.     

A mechanical study of gap motion in cadaveric femurs using short and long supracondylar nails

OBJECTIVE: To determine the relative stability achieved in unstable supracondylar femur fractures treated with long (36 cm) and short (20 cm) retrograde intramedullary nails using 1 or 2 proximal locking bolts. We hypothesized that longer nails would reduce fracture site motion compared with short nails and that 2 proximal locking bolts would improve stability compared with 1 proximal locking bolt. DESIGN: Nine pairs of matched human cadaveric femurs were instrumented with 20-cm and 36-cm retrograde intramedullary nails (all 12-mm diameter, Biomet, Warsaw, IN) following reaming to 13 mm. Transverse supracondylar gap (6 mm) osteotomies were created. The femurs were mounted and cyclically tested separately in coronal plane bending and sagittal plane bending on a materials testing system. Fracture site translation was measured using a digital caliper in the respective plane. SETTING: Orthopaedic biomaterials laboratory. RESULTS: With 2 proximal locking bolts, average sagittal translation was 7.2 mm and 1.8 mm, respectively, for the 20-cm and 36-cm nails. Coronal translation was 6.3 mm and 4.3 mm, respectively. With a single proximal locking bolt, average sagittal translation was 7.6 mm and 2.2 mm, respectively, for the 20-cm and 36-cm nails. Coronal translation was 13.6 mm and 4.4 mm, respectively. A statistically significant difference in fracture site translation was found in each pairing by Student t test (P < 0.005), except coronal translation with 2 proximal locking bolts (P = 0.056). Free-body analysis predicts higher local stresses at the proximal interlocks of the shorter nail. CONCLUSIONS: Longer nails provide improved initial fracture stability when compared with short retrograde nails for supracondylar femur fractures due to a more stable mechanical interaction between the femoral diaphysis and the nail. A second proximal locking bolt in the long nail provides no additional stability.     

Mechanical study of the safe distance between distal femoral fracture site and distal locking screws in antegrade intramedullary nailing

OBJECTIVE: To determine the safe distance for distal femoral fractures relative to the distal locking screws in antegrade intramedullary femoral nailing using a currently available titanium alloy nail design. DESIGN: Cyclic (fatigue) mechanical testing study. SETTING: Biomechanics laboratory. INTERVENTION: Intramedullary nailing of left synthetic fiberglass composite femora with type 32/33-C fractures at 1, 2, 3, and 4 cm from the more proximal of the distal locking screws. MAIN OUTCOME MEASUREMENT: The number of loading cycles to failure of the nail. RESULTS: A load level of 700 N through the femoral mechanical axis was validated as adequate to cause fatigue failure within 200,000 cycles in slotted stainless- steel nails. In the nonslotted titanium alloy nails, this load level caused failure in only 1 of 3 nails with a fracture at 2 cm from the more proximal of the 2 distal locking screws and in 2 of 3 nails with a fracture at 1 cm from the more proximal of the 2 distal locking screws. All of the other nails did not fail >1 million cycles. CONCLUSIONS: Under laboratory conditions, it is safe to assume that an antegrade titanium alloy nail will survive 1 million compression/bending cycles when the fracture is > or = 3 cm from the more proximal of the 2 distal locking screws.     

Biomechanical characteristics of interlocking femoral nails in the treatment of complex femoral fractures

Interlocking intramedullary (IM) nails allow more comminuted and proximal or distal femoral fractures to be successfully treated than previously possible with routine IM nailing. Autopsy specimens were prepared to evaluate the effectiveness of different locking mechanisms on fracture site stability. Grosse-Kempf (GK) and Brooker-Wills (BW) IM nails were inserted in anatomic specimen femurs with transverse fractures and 1-, 2-, and 3-cm defects. The femurs were loaded in four-point bending, and bending stiffness was calculated. The femurs were also loaded in torsion, and the amount of slippage between the nail and bone (at 10 Nm of applied torque) was measured. The GK nail, fully interlocked, had the lowest amount of rotational slip, followed by the BW and the GK noninterlocked nail. Bending stiffness was not significantly different for these IM nails.     

Prevention of potential fracture between two implants using interlocking bipolar cut short GK nail and Enders nail

A technique to prevent a potential fracture occurring between the distal end of a cementless hip prosthesis and the proximal end of a dynamic compression screw (DCS) is described. The method involves bridging the two implants using a bipolar shortened femoral nail. The proximal connection is secured by telescoping the stem of the hip prosthesis into the shortened femoral nail, which is further improved by filling the gap between the stem and the femoral nail with an Enders nail. The distal connection is secured by placing the distal locking screw of the femoral nail through the distal femoral plate of the dynamic compression plate first before locking the nail to the distal femur. Further stabilisation and promotion of healing at the distal femur were achieved using cement and bone graft.     

TREATMENT OF HUMERAL SHAFT FRACTURES WITH THE SEIDEL INTRAMEDULLARY NAIL

Background: The use of intramedullary nails for the management of humeral shaft fractures has been controversial. Recently, the Seidel nail has become available. The purpose of this study was to review our initial experience with the Seidel nail. Methods: A retrospective clinical and radiographic review of 25 consecutive patients treated with Seidel intramedullary humeral nail was performed. The nail was used for non-union in 10 patients, delayed union in four, acute fracture in eight and pathological fracture in three. Eighteen of the 19 survivors were clinically reviewed at an average of 15 months (range 8–25). Pain, function, satisfaction, shoulder power, range of motion and clinical outcome were graded using the UCLA shoulder score. Results: Pain was present at the shoulder in four patients and at the fracture site in nine. Average shoulder abduction was 99° and nine patients could not abduct the shoulder past 90°. Sixty-six per cent of patients reviewed were graded as only fair or poor using the UCLA shoulder score. In three patients rotational control was not achieved with the distal locking device at the time of surgery. Complications included non-union in 10 patients and three intra-operative fractures. Conclusions: Non-union was more likely to occur if rotational control was not obtained, or if the patient had the nail inserted for a previous non-union. Use of the Seidel nail frequently leads to shoulder pain and dysfunction. The distal locking device is unreliable and predisposes to non-union. We do not recommend the continued use of the Seidel nail.     

A new modular nail for the diaphyseal fractures of the humerus

Over a period of 5 years, 63 traumatic and eight pathological diaphyseal humeral fractures were treated with a new modular humeral nail. The nail is cannulated, square in shape - with concave sides - and has two different extensions that can be used with either the antegrade or the retrograde approach. Adequate rotational and axial stability is provided without the need for distal locking screws in the majority of fractures, while the need for proximal locking screws during the antegrade procedure is abolished. This study aims to present the ‘Garnavos’ nail and the results of its use, along with proposals and guidelines that should be considered whenever intramedullary nailing is selected for the treatment of diaphyseal humeral fractures.     

Numerical evaluation of the mechanical properties of a novel expandable intramedullary nailing: A new alternative to standard interlocking nailing

Introduction: There has been a great effort in preventing the disadvantages of distal locking in intramedullary nailing to date. From this scope, a novel expandable nail fixation eliminating distal locking screws has been designed. The primary aim of this numerical parametric study is to investigate mechanical behavior of expandable nail fixation on the fractured femur model under different contact parameters which are effective in maintaining the nail position and to specify the appropriate values of these contact parameters for a safe fixation. The second aim is to compare mechanical behavior of the expandable nail fixation with the standard interlocking nail fixation.Materials and Methods: The expandable nail has three wedges which are responsible for distal fixation by compressing the medullary canal in the radial direction. 4th generation Sawbones femur model was used as bone model. A transverse osteotomy with 20 mm gap was created to simulate a subtrochanteric fracture. The fixations have been examined under axial compression with 1200 N and torsion with 7 Nm. In the parametric study, the tightening torque and static friction coefficient in wedge-canal contact were selected as contact parameters. The outputs were stiffnesses of the fixations, equivalent von-Mises stress distribution on the models, and load sharing between the canal and distal locking elements.Results: The results of the parametric study showed that the model with the tightening torque of 3 Nm and friction coefficient of 0.7 was the safest. The load borne by wedges is generally prone to increase with increased tightening torque and friction coefficient. The both fixations showed close stiffness and stress values.Conclusion: The tightening torque of the wedge locking mechanism is directly effective in maintaining the nail position constant in canal, and the safety of the fixation is better ensured with increased tightening torque but stress states on bone must be carefully evaluated. The expandable nail provided comparable results to standard interlocking nails with respect to the fixation stiffness, stress, and contact forces. The expandable nailing may be evaluated as an alternative in the fractures of long bones in the case that the numerical results are supported by future experimental studies.     

Evidence for Success with Locking Plates for Fragility Fractures

Fixation of fragility fractures with plates and screws often results in loss of fixation and need for revision surgery. Locking plates and screw were introduced to improve fixation of fragility fractures and have been in use for a decade. This review was conducted to compile evidence that locking plates and screws improve fixation of fragility fractures. A search of PubMed was performed to identify biomechanical studies as well as clinical series of fragility fractures treated with locking plates. Biomechanics papers had to use models of osteoporotic bone and had to directly compare locking plates with traditional plates. Clinical studies included case series in which locking plates were applied to elderly patients with fractures of the proximal humerus and periprosthetic distal femur fractures. Most studies are retrospective case series. Locking plates lead to greater stability and higher loads to failure than traditional plates. When applied to proximal humerus fractures, uncomplicated healing occurs in 85% of patients. Constant and Dash scores approach normal values. For distal femoral periprosthetic fractures, union rates of 75% are reported with a malunion rate of 10%. Early evidence suggests that locking plates improve results of treatment of proximal humerus fractures and distal femoral periprosthetic fractures in the elderly. Loss of fixation is associated with failure to achieve stability at the fracture site. Principles of fracture fixation in osteoporotic bone defined prior to the introduction of locking plates should still be applied.     

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

ObjectiveThe 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.MethodsInSafeLOCK 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.ResultsAll 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).ConclusionThese 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.     

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.     

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.     

Correcting rotational deformity following femoral nailing

Introduction

The incidence of rotational malalignment after femoral nailing has been reported to be at least 20%. If the deformity is recognised early, it can be corrected by changing the distal locking screw and rotating the bone prior to fracture union. It is common practice to use the same distal locking screw of the nail if this surgery is performed, however, there is a risk of the new drill hole “cutting out” into the old screw hole. The degree of rotational deformity that needs to be corrected to use the same distal locking hole without cut out of the screw has not been defined.

Method

Ten femora, five from cadavera and five synthetic (“Synbone”), were stabilised in a vice and then fitted with one distal transverse screw. The screw was then removed and a second distal transverse screw was inserted at the same level after variable amounts of rotation. The bone bridge between the drill holes was then measured and any cut out was noted.

Results

Both of the femora cut out when rotated 10°, and one when rotated 15°. The size of the bone bridge between drill holes in femora rotated by 20° was 3 mm. This bone bridge was increased to 4 mm when the femora were rotated by 25°, and 8 and 9 mm when rotated by 30°.

Conclusion

The amount of rotational deformity that needs to be corrected in order to use the same distal locking hole in a femoral nail is significant. In our study, this equates to a correction of at least 25°, but this is not a definitive value in practice. Particular attention must be paid to the location and size of the distal locking screw when correcting malrotation after femoral nailing, to ensure an adequate bone bridge between the two holes.     

Setscrew distal locking for intramedullary nails: a biomechanical study

OBJECTIVE: This biomechanical study was undertaken to examine the effectiveness of setscrew distal locking in a static intramedullary (IM) femoral nail on the stability of fixation of femoral shaft fractures. DESIGN: Fifteen fresh-frozen cadeveric femora were randomly separated into three groups of five bones and transversely sectioned immediately distal to the isthmus. After the insertion of the large-diameter nails, distal locking was obtained by conventional method in the first group. In the second group, set-screw design was used in which two transverse screws penetrated only the lateral cortex of the femur and compressed the nail in the intramedullary canal. No distal locking was used in the third group. INTERVENTION: All instrumented femurs were mounted on a servohydraulic testing machine and tested in both rotations (20 degrees) and axial compression (amplitude: 1,000 Newton). MAIN OUTCOME MEASUREMENT: Loading-versus-displacement data, acquired at a ten-Hertz sampling rate, were calibrated and used to calculate maximum torque, stiffness, and energy capacity to failure. Maximum displacement and axial stiffness also were determined. RESULTS: Mean maximum torque at 10 degrees for each group were 15.3+/-4.8 newton-meters for the interlocking group, 8.5 +/-1.2 newton-meters for the setscrew group, and 3.6+/-2.7 newton-meters for the nonlocked femora. At 20 degrees of rotational displacement, the torque measured 37.4+/-2.6 newton-meters; 15.0+/-4.0 newton-meters; and 5.3+/-3.1 newton-meters, respectively (p < 0.05). Mean torsional stiffness was 1.17+/-0.76 newton-meters per degree for the setscrew group and 1.34+/-0.83 newton-meters per degree for the interlocking group (p > 0.05). The setscrew design provided 87 percent of the torsional rigidity of the interlocking group. In the axial compression test, mean maximum shortening was 1.1+/-0.3 millimeters in the interlocking group and 1.4+/-0.6 millimeters in the setscrew group (p > 0.05). The mean stiffness on longitudinal compression provided by the interlocking screws and the setscrews was 918 and 860 newton-meters per millimeter, respectively. CONCLUSION: The distal setscrew design provides adequate distal fixation of intramedullary nail for patients in the postoperative rehabilitation period of the femoral shaft fractures treated with intramedullary nailing.     

Mechanische Einflussfaktoren der Marknagelung auf die femorale Antetorsion

INTRODUCTION: Antegrade or retrograde intramedullary nailing is a common and well established procedure for the treatment of femoral shaft fractures. One drawback of this technique is the high incidence of clinically relevant malalignment. Despite intra-operative and radiological improvements this problem has not yet been solved efficiently. The aim of this study was the evaluation of the mechanical influence on the antetorsion angle of intramedullary nails during and after interlocking in femoral shaft fractures. MATERIAL AND METHODS: A mechanical instrument was developed allowing a defined torque to be administered to the distal femur fragment. As an optical measurement system for the assessment of the antetorsion angle, a navigation system was applied. Initially the influence of the interlocking mechanism of the nail on the antetorsion deviation was investigated. The distal interlocking hole was fixed free handed or by using a navigation system. The multidirectional movement of the distal femur fragment was documented. Furthermore, the influence of the rotational stability on the antetorsion angle after mechanical stress of 4 NM was investigated by measuring the remaining rotational capacity of the distal femur fragment. RESULTS: The average remaining rotational capacity of the distal femur fragment was 5.8 degrees after locking the nail by hand. The navigated locking resulted in a deviation of only 2 degrees , a significant difference compared to the free-hand procedure. The rotational stability under stress showed an average of 15.4 degrees deviation of the distal fragment. Even after complete interlocking of the intramedullary nail a 14.2 degrees rotational deviation was observed. DISCUSSION: It could be shown that mechanical stability as well as the interlocking itself of femoral nails have a relevant impact on the antetorsional angle of the femur. Potential sources of error of the femoral antetorsion angle can be caused by the interlocking process as well as by forced rotation of the femur after interlocking. Clinical studies are needed to improve our findings, while the observed effects might have an essential influence on the incidence of femoral malalignment after osteosynthesis by intramedullary nailing of the femur.     

An intramedullary nail with multifunctional interlocking for all types of fracture in both femurs

Objective: A femoral compound interlocking intramedullary nail (FCIIN) was designed to treat all types of fractures between the trochanter and epicondyle of both femurs. It could substitute for femoral interlocking intramedullary nails (FIIN) at five points. Methods: According to the morphological characteristics of the femoral medullary canal, the nail is designed to accommodate a 1250 mm radius of radian and a 135° neck‐shaft angle. Three interlocking holes of 6.5 mm diameter are located at the proximal end of the FCIIN, making crossing of the screws possible. The hole is designed to be vertical (90°) or oblique (45° upper or lower). At the tip of the proximal interlocking screws, whose root diameter gradually increases from 3.5 mm to 6.5 mm, a self‐tapping cancellous screw is placed. There are two types of distal interlocking screws. One is a fine thread and the other a bolt screw. Two interlocking holes and a recess 4.5 mm in diameter are located at the distal end of the FCIIN. Under biomechanical destructive testing, the proximal interlocking screw device has satisfactory strength and reasonable structure. A total of 47 patients (31 males and 16 females, with an average age of 39.83 years) with femoral fractures were assessed in this study. Fourteen cases were diagnosed as intertrochanteric, 7 as subtrochanteric, 18 as femoral shaft, and 8 as supracondylar fractures. All 47 patients were treated with the FCIIN. Results: Of the 47 patients, anatomic reduction was achieved in 34, good reduction in 11, and forced line reduction in 2 cases. Reduction was excellent or good in 95.87% of the fractures. The removal time of the FCIIN was 12 to 21 months (average, 16.9 months). One patient with an intertrochanteric fracture who had a fixation failure combined with non‐union achieved healing with an external fixator at 18 months. Failure to insert the distal interlocking screws occurred in 5 patients but did not affect bone healing. Conclusion: The FCIIN is a useful device in the treatment of a variety of femoral fractures.     

Volar fixation for dorsally angulated extra-articular fractures of the distal radius: a biomechanical study

PURPOSE: To compare the biomechanical properties of 10 volar plate-fixation designs in 2 fracture models (dorsal wedge osteotomy, segmental resection osteotomy models). METHODS: Forty-eight radiuses were used in this study including 8 pairs. In 40 specimens a 15-mm dorsally based wedge osteotomy was performed and the volar cortex was fractured manually. They were arranged into 10 fixation groups with 5 different fixation designs (test 1). In the contralateral specimens of 8 paired radiuses a 10-mm segment of bone was excised (test 2). Four of the 10 fixation systems were chosen for these specimens. Cadaver hands and the proximal radiuses were potted in polymethylmethacrylate and tested with a servohydraulic materials testing machine with 300 N of axial compression load at 1 N/s initially and after each 1,000 cycles up to 5,000 cycles. After cyclic loading the specimens were loaded to failure in axial compression at 2 mm/min. The stiffness, failure peak load, and failure mode of each specimen were recorded. RESULTS: In test 1 in the wedge osteotomy specimens the T plate was the stiffest and the Synthes titanium plate was the least stiff; however, all specimens completed the 5,000 cycles of loading with no failures. There was no significant difference between the 10 fixation groups in failure peak load and only 7 of 40 failed at the distal portion of the hardware in the final load to failure testing. In test 2 the resection osteotomy specimens were less stiff and failed at a lower failure peak load compared with the wedge osteotomy specimens. Failure at the distal portion of the fixation system was seen in 7 of 8 specimens; nonlocking screws loosened and tines compressed the surrounding bone, resulting in tine-hole enlargement. CONCLUSIONS: All of the plate-fixation systems delivered sufficient stability to permit the simulated postoperative regimen of 1 week of immobilization followed by 5 weeks of early mobilization until expected union at 6 weeks after surgery. Based on these results a preferable volar fixation system would appear to benefit from the following: (1) sufficient plate strength to support the distal fragment from the volar side, (2) a locking system with sufficient strength to remain locked during the healing process, and (3) a distal design that does not affect the bone adversely. The anatomic reduction of the volar cortex in the wedge osteotomy specimens added stability to the construct.     

Rotational stability of a modified step-cut for use in intercalary allografts

BACKGROUND: Intercalary allografts are used for the reconstruction of major skeletal defects. Step-cuts help to provide rotational stability when intramedullary fixation is used. A modified step-cut is proposed to reduce rotation at the interface. This study compares the rotational stability of conventional and modified step-cuts. METHODS: In Phase I, seven pairs of human cadaveric femora were divided into a conventional step-cut group (left femora) and a modified step-cut group (right femora). All femora were cut transversely at the mid-diaphysis. In the conventional group, a 1-cm step-cut was created in the exact midsagittal plane in both the proximal and distal segments. In the modified group, a 1-cm step-cut was created in the parasagittal plane, leaving 2 mm of additional bone on both the proximal and the distal fragment. Phase II was identical except that in the modified step-cut group only 1 mm of additional bone was left. Smooth femoral nails were then placed after standard reaming. Specimens were tested by fixing the proximal segment and applying +/-2 N-m (17.7 in-lb) of torque to the distal segments with ten oscillation cycles. Maximum rotation was measured. The data were analyzed with the paired Student t test. RESULTS: The average rotation in Phase I was 23.3 degrees for the conventional step-cut group and 3.0 degrees for the 2-mm modified step-cut group; the difference was significant (p < 0.001). Four femora sustained an incomplete fracture during nail insertion. The average rotation in Phase II was 20.6 degrees for the conventional step-cut group and 0.5 degrees for the 1-mm modified step-cut group without any fractures; the difference was significant (p < 0.001). CONCLUSIONS: Step-cut modification that leaves more bone in the sagittal plane provides rigid fixation and significantly more stability than the conventional step-cut technique.     

A biomechanical comparison of proximal femoral nails and locking proximal anatomic femoral plates in femoral fracture fixation: A study on synthetic bones

Background:The incidence of fractures in the trochanteric area has risen with the increasing numbers of elderly people with osteoporosis. Although dynamic hip screw fixation is the gold standard for the treatment of stable intertrochanteric femur fractures, treatment of unstable intertrochanteric femur fractures still remains controversial. Intramedullary devices such as Gamma nail or proximal femoral nail and proximal anatomic femur plates are in use for the treatment of intertrochanteric femur fractures. There are still many investigations to find the optimal implant to treat these fractures with minimum complications. For this reason, we aimed to perform a biomechanical comparison of the proximal femoral nail and the locking proximal anatomic femoral plate in the treatment of unstable intertrochanteric fractures.Result:Nail and plate models were locked distally at the same level. Axial steady load with a 5 mm/m velocity was applied through the mechanical axis of femur bone models. Axial loading in the proximal femoral intramedullary nail group was 1.78-fold greater compared to the plate group. All bones that had the plate applied were fractured in the portion containing the distal locking screw.Conclusion:The proximal femoral intramedullary nail provides more stability and allows for earlier weight bearing than the locking plate when used for the treatment of unstable intertrochanteric fractures of the femur. Clinicians should be cautious for early weight bearing with locking plate for unstable intertrochanteric femur fractures.