Intramedullary nailing confers an increased risk of medial migration compared to dynamic hip screw fixation in unstable intertrochanteric hip fractures

IntroductionMedial migration of the femoral neck element (FNE) superomedially against gravity with respect to the intramedullary component of the cephalomedullary nail is a complication increasingly recognized to cause femoral head cut-out in intramedullary nailing of pertrochanteric hip fractures. Although cut-outs are common to both intra- and extramedullary fixation, especially in unstable pertrochanteric hip fractures, FNE medial migration in sliding hip screws continues to remain sparse despite increased awareness of the phenomenon. This study aims to investigate whether intramedullary nailing is biomechanically predisposed to FNE medial migration compared to extramedullary fixation with sliding hip screws to account for the discrepancy in reported FNE medial migration rates.Materials and methodsTwelve fourth-generation synthetic femurs (Sawbones) with unstable intertrochanteric fractures were divided into 2 groups (n=6 per group). Fracture fixation was performed using the Proximal Femoral Nail Antirotation (PFNA, Synthes) (n=6) in the first group, and the Dynamic Hip Screw (DHS, Synthes) (n=6) in the second group. Both groups were subjected to bidirectional cyclic loading (600N compression loading, 120N tensile loading) at 2 Hz for 5000 cycles. The medial migration distance (MMD) was recorded at the end of the testing cycles.ResultsThe mean MMD in the PFNA group was 4.56mm (SD 0.69mm) with consistent reproduction of medial migration across all constructs tested. This was significantly more compared to the MMD of 1.17mm (SD 0.69mm) in the DHS group (p<0.001).ConclusionIntramedullary nailing of unstable intertrochanteric hip fractures is inherently predisposed to FNE medial migration making it more susceptible to consequent cut-out compared to fixation with the DHS.     

Implant fracture of the TFNA femoral nail

BackgroundThe TFNA (Trochanteric Fixation Nail Advanced) Proximal Femoral Nailing System (DePuy Synthes) is frequently used for intramedullary fixation of proximal femoral fractures. The aim of this study was to evaluate all TFNA implant fractures at a UK trauma unit to ascertain any patient or surgical factors associated with implant failure.MethodsA retrospective study was carried out identifying all patients that sustained a TFNA implant fracture over a five-year period. Data was collected on demographic information, ASA, co-morbidities, mechanism of injury, fracture pattern according to the AO/OTA classification, procedure details and time to failure. Radiographs were assessed by two independent reviewers to identify tip-apex distance (TAD), calcar TAD, reduction quality and union status at time of implant failure.ResultsSix cases were identified, all with implant breakage at the aperture for the proximal screw. All femoral fractures were intertrochanteric reverse obliquity type (OA/OTA 31A3). Two were traumatic fragility fractures and the remainder atraumatic. Mean time from index surgery to revision was 441 days (104–963). Mean TAD was 20.5 mm (15–24) and mean calcar TAD 24 mm (18–32). All six cases displayed radiographic non-union at the time of implant fracture.ConclusionPathological fractures resulting in reverse obliquity type fracture patterns and subsequent non-union appear to be contributory factors to TFNA breakage at the proximal screw aperture. This may be further exacerbated by alterations to the nail design from previous generations. In these patients, close follow up with clinical and radiographic surveillance should be employed. Further biomechanical and clinical studies are required to compare this finding against other nail designs.     

Comparison of a sliding hip screw with a trochanteric lateral support plate to an intramedullary hip screw for fixation of unstable intertrochanteric hip fractures: a cadaver study

BACKGROUND: The lateral trochanteric support plate (LSP) was developed to prevent excessive sliding of unstable intertrochanteric femur fractures fixed with a sliding hip screw (SHS). This study compared the fracture stability and screw sliding characteristics of unstable intertrochanteric femur fractures fixed with either an SHS and LSP or an Intramedullary Hip Screw (IMHS). METHODS: Six matched pairs of cadaveric human femurs with simulated, unstable intertrochanteric femur fractures were stabilized with either an IMHS or a 135-degree SHS with an attached LSP. Inferior and lateral head displacements and lag screw sliding distances were measured for applied static loads of 750 N, before and after cycling. RESULTS: Four-part unstable intertrochanteric femur fractures showed comparable screw sliding characteristics and stability whether instrumented with an SHS and LSP or an IMHS. CONCLUSION: A sliding hip screw with an attached lateral support plate provides stability and ability to resist medial displacement of the femoral shaft similar to that seen with the IMHS.     

Helical blade versus sliding hip screw for treatment of unstable intertrochanteric hip fractures: a biomechanical evaluation

OBJECTIVE: To compare the fixation stability in the femoral head with sliding hip screw versus helical blade designs for unstable, intertrochanteric hip fractures. METHODS: A simulated, unstable intertrochanteric hip fracture was created in six pairs of cadaveric femurs. One of each pair was treated using an intramedullary nail with a sliding hip screw (ITST) for femoral head fixation and the other was treated with a nail with a helical blade (TFN). Each specimen was cyclically loaded with 750N vertical loads applied for 10, 100, 1000 and 10,000 cycles. Measurements for femoral head displacement, fracture fragment opening and sliding were made. Specimens were then loaded to failure. RESULTS: There was significantly more permanent inferior femoral head displacement in the ITST samples compared to the TFN samples after each cyclic loading (all p values<0.05). There was significantly more permanent fracture site opening and inferior displacement in the ITST group compared with the TFN group at 1000 and 10,000 cycles (p<0.05). Final loads to failure were not significantly different (p=0.51) between the two treatment groups. Nine specimens demonstrated fracture extension into the anteromedial cortex and subtrochanteric region and three specimens, which had an ITST implant, demonstrated a splitting fracture of the femoral head. CONCLUSION: This study demonstrated that fixation of the femoral head with a helical blade was biomechanically superior to fixation with a standard sliding hip screw in a cadaveric, unstable intertrochanteric hip fracture model.     

Radiographic outcomes of intertrochanteric hip fractures treated with the trochanteric fixation nail

BACKGROUND: Intertrochanteric hip fractures have become more common as the elderly population continues to increase, and surgical stabilisation of these fractures remains a persistent challenge. The purpose of this study was to analyse the ability of a new helical blade device to stabilise intertrochanteric hip fractures, and to further determine which factors are important in implant stability. METHODS: Two hundred and fifty-five patients with an intertrochanteric hip fracture were treated with a trochanteric fixation nail (TFN), 97 of whom fit strict radiographic and follow-up criteria and were included in the study group. After adjusting for magnification and rotation, blade migration within the femoral head and telescoping of the blade along its axis were measured using a custom-designed grid system. Multivariate regression analyses were performed to determine which variables predicted blade migration and telescoping. RESULTS: Fifty-nine fractures were classified as stable, and the remaining 38 were unstable. Mean telescoping was 4.3 mm in the unstable group, compared to 2.6 mm in the stable group (p<0.05). Blade migration within the femoral head averaged 2.2 mm overall, with no difference between stable and unstable fractures. For both telescoping and blade migration, no significant change occurred after the 6-week time point in the stable or unstable group. Nail length, age, and gender did not have a significant effect on either blade migration or telescoping implant position change. Of the initial cohort of 255 patients, five cutouts and one nonunion occurred, three of which required subsequent procedures. CONCLUSIONS: Subtle migration ( approximately 2mm) of the tip of the blade within the femoral head occurred in all fractures, but this did not preclude maintenance of reduction and fracture healing, and was not predicted by fracture type, reduction quality, age, or gender. More telescoping occurred in unstable compared to stable fractures, but this averaged 4mm and did not affect stable fixation or fracture healing. All position changes occurred within the first 6 weeks postoperatively, with no subsequent detectable migration or telescoping. Clinical correlations will be needed in the future to determine the significance of small amounts of migration or differences in telescoping, but this device appears to provide effective fixation in both stable and unstable intertrochanteric hip fractures.     

Intramedullary versus extramedullar fixation of subtrochanteric fractures: A biomechanical study

We compared two different subtrochanteric fracture fixation techniques, an intramedullary hip screw system (IMHS) and an extramedullary dual sliding screw-plate system (MSP), to determine relative fixation stability. 6 matched pairs of osteosynthe-sized osteopenic cadaver femurs were axially loaded to 1000 N with concurrent, simulated abductor forces of 0%, 50% or 86% of the applied head force. The initial loading sequence was made with uniaxial dynamization-the lag screw of the MSP locked and distal locking of the IMHS nail. Femoral head displacement and medial femoral strain were measured for intact femur controls, after fixation of a 2-part reverse oblique subtrochanteric fracture and finally a 3-part reverse oblique subtrochanteric fracture with a lateral wedge defect. The samples were then loaded at 750 N for 10⁴ cycles with both devices uniaxially locked, followed by 10⁴ cycles with both devices fully biaxially dynamized (unlocked). For the 2-part subtrochanteric fracture pattern, both devices exhibited similar inferior displacements of the femoral head (average 2.0 mm) and medial femoral strain (-70% of intact). Increasing abductor forces decreased medial compressive strain but did not significantly affect head displacement. For the 3-part fracture model, the MSP demonstrated significantly less inferior displacement of the head (1.6 mm vs. 2.1 mm) and both devices demonstrated significantly decreased medial strain. After cycling, head displacement increased approximately 50% in both devices and medial strain increased slightly. After unlocking and cycling, the MSP group showed significant lateral displacement of the proximal fragment.

The IMHS and MSP devices provide similar stability for fixation of 2-part and 3-part reverse oblique subtrochanteric fractures. In a biaxially dynamized, 3-part reverse oblique fracture, displacement of the proximal fragment can occur with the MSP.     

A biomechanical evaluation of the Gamma nail.

We examined the effect of the Gamma nail on strain distribution in the proximal femur, using ten cadaver femora instrumented with six unidirectional strain gauges along the medial and lateral cortices. The femora were loaded to 1800 N and strains were determined with or without distal interlocking screws before and after experimentally created two-part and four-part fractures. Motion of the sliding screw and the nail was also determined. Strain patterns and screw motion were compared with previously obtained values for a sliding hip screw device (SHS). The Gamma nail was shown to transmit decreasing load to the calcar with decreasing fracture stability, such that virtually no strain on the bone was seen in four-part fractures with the posteromedial fragment removed; increasing compression was noted, however, at the proximal lateral cortex. Conversely, the SHS showed increased calcar compression with decreasing fracture stability. The insertion of distal interlocking screws did not change the pattern of proximal femoral strain. The Gamma nail imparts non-physiological strains to the proximal femur, probably because of its inherent stiffness. These strains may alter bone remodelling and interfere with healing. Distal interlocking screws may not be necessary for stable intertrochanteric fractures.     

RETRACTED ARTICLE: Outcomes of length-stable fixation of femoral neck fractures

Introduction  

The most common implants for treating unstable femoral neck fractures are sliding constructs, which allow postoperative collapse. Successful healing, typically, is a malunion with a shortened femoral neck. Functional sequelae resulting from altered femoral neck biomechanics have been increasingly reported. Re-operation rate due to nonunion, avascular necrosis, hardware cut-out and prominence is high with this treatment modality. We evaluated the outcomes of patients with femoral neck fractures treated with stable calcar pivot reduction, intraoperative compression across the fracture, and stabilization with length-stable implants.     

Biomechanical factors affecting fracture stability and femoral bursting in closed intramedullary nailing of femoral shaft fractures, with illustrative case presentations

Closed intramedullary nailing is an accepted method of treatment for femoral shaft fractures. Technical complications of the procedure include fracture instability, which may result in proximal nail migration, malrotation, delayed union, and occasionally femoral bursting during insertion of the nail, sometimes leading to fracture instability as well as shortening. This study defines the effect of starting hole position, fracture component length, reamed diameter, and nail type on the potential for femoral bursting and fracture instability. The most significant factor in the proximal femoral component was found to be the position of the starting hole. Anterior displacement by greater than 6 mm from the neutral axis of the medullary canal consistently caused high hoop stresses at the level of the fracture, which resulted in bursting of the proximal femoral component by lifting off the anterior cortex. Hoop stresses at the level of the fracture were less sensitive to lateral or medial placement of the starting hole. Distally, fracture stability was governed by femoral component length and reamed diameter. In the proximal and distal components, fracture stability and the potential for bursting were influenced by the particular nail used. This was due to significant differences in mechanical geometric properties between nails of different manufacturers. Case reports are presented to illustrate these biomechanical principles as they apply to clinical situations.     

Retrograde nailing of a femoral supracondyle

Because standard femoral supracondylar nails have certain disadvantages, they are often replaced by traditional femoral or tibial locked nails. The purpose of this study was to make a biomechanical comparison between both types of traditional locked nails to determine which technique was more suitable for treating unstable femoral supracondylar fractures. Fourteen left Sawbones femurs (Pacific Research Laboratories, Vashon, Washington) were osteotomized in the femoral supracondylar area. One centimeter of the medial cortex in the proximal fragment was obliquely removed to simulate an unstable fracture without shortening. Seven specimens were treated with traditional retrograde dynamic femoral locked nails, and the other 7 with traditional retrograde dynamic tibial locked nails. All specimens were tested with a servohydraulic materials testing machine to compare their relative stability. Static compression, dynamic cyclic compression, and static compression to failure were tested. An extensometer was used to measure the displacement of fragments. Displacement between the fragments increased following the increment in loads in both nails. The load-displacement curve was nearly linear up to 1000 N for both nails. The femoral nail had a greater stiffness compared with the tibial nail at 100 and 200 N (P=.02 and P=.04, respectively) in static compression and at 700 to 1000 N (P=.01 in each case) in dynamic cyclic compression, as well as larger loads in static compression to failure (8663 vs 7547 N, respectively; P<.001). Clinically, a traditional femoral locked nail may be more suitable to replace a standard femoral supracondylar nail in a retrograde fashion to treat an unstable femoral supracondylar fracture.     

Evaluation of the long intra-medullary hip screw

There have been many publications about second generation femoral nails, such as the Russell–Taylor nail (Smith & Nephew Richards, Memphis, TN, USA) and Long Gamma Nail (Howmedica, Rutherford, NJ, USA), but little work has been published on the Long Intra-medullary Hip Screw (IMHS, Smith & Nephew). We set out to evaluate the effectiveness of the Long IMHS as a device for the fixation of proximal femoral fractures. We retrospectively reviewed 30 patients who had a Long IMHS inserted for a sub-trochanteric or proximal femoral fracture. Of the 30 patients, three had died and six were lost to follow up, leaving 21, whom we reviewed.

Of the 21 patients reviewed the mean age was 67 years and the mean follow up was 31 weeks. Mean time to union was 15.65 weeks, with one non-union. There were three superficial wound infections. In one patient there was loosening of the distal locking screws, requiring removal and there was one case of intra-operative femoral shaft fracture.

We conclude that, the Long IMHS is an effective device for the treatment of sub-trochanteric and proximal femoral fractures with a high rate of union achieved and a low complication rate.     

Biomechanical evaluation of anatomic reduction versus medial displacement osteotomy in unstable intertrochanteric fractures

The biomechanical characteristics of anatomic reduction versus medial displacement osteotomy were compared for four-part intertrochanteric fractures experimentally produced in cadaver femurs. Eighteen pairs of femurs were assigned randomly to either the anatomic (A) or the medial displacement (MD) group and instrumented with multiple strain gauges. The femurs in the MD group were tested while intact and following four-part fracture with fixation. The femurs in the A group were first tested intact, followed by a stable two-part fracture with fixation, and then by a four-part fracture with fixation and perfect reduction of the posteromedial fragment (PMF) with a lag screw, partial reduction of the PMF, and with the PMF omitted. All fractures were fixed with a 135 degrees, four-hole, sliding hip screw. The strain distribution in the MD group changed significantly after fracture. The plate tensile strain increased by 360% while the compressive calcar strain decreased 85%. The plate tensile strain in the A group also increased significantly after four-part fracture when the PMF was perfectly reduced (160%), partially reduced (290%), or discarded (275%); the calcar compressive strains for these subgroups decreased approximately 50%. This laboratory study indicates that anatomic reduction of four-part intertrochanteric fractures with the sliding hip screw, regardless of the presence or position of the PMF, provides significantly higher compression across the calcar region and significantly lower tensile strain on the plate than fractures reduced by medial displacement osteotomy. The more physiologic strain distribution and the increased medial load transmission support the use of anatomic reduction for the treatment of unstable intertrochanteric fractures.     

Early experience with the gamma interlocking nail for peritrochanteric fractures of the proximal femur.

Surgical fixation, early weight-bearing, and bony union remain a challenge in the treatment of peritrochanteric femur fractures, especially if the fractures are comminuted or unstable. Preliminary experience with the Gamma locking nail, a short intramedullary nail connected to a sliding compression screw augmented with distal locking screws, is presented. In a consecutive series of 29 patients, all fractures were adequately reduced and immediate weight-bearing was begun regardless of fracture configuration (13/27 fractures classified as unstable). Twenty-seven patients were reviewed at 6 months. At follow-up, all patients continued to be ambulatory and all fractures healed. Major complications included screw migration in the femoral head (two patients), difficulty in securely placing the distal screws (eight patients), and a femoral shaft fracture through the distal locking screws following a fall. The technical problems inherent in the device and its instrumentation are discussed. In this early experience, the Gamma nail appears to allow for early patient ambulation regardless of the fracture configuration with excellent clinical results.     

A critical analysis of the eccentric starting point for trochanteric intramedullary femoral nailing

OBJECTIVES: Antegrade femoral intramedullary nailing through a greater trochanteric insertion site has been proposed for the treatment of subtrochanteric fractures. The currently available trochanteric nails have dissimilar characteristics, and the most appropriate insertion site for satisfactory subtrochanteric fracture alignment has not been determined. This study is an analysis of 5 different trochanteric femoral nails and 3 different insertion sites using a cadaveric model of a reverse obliquity subtrochanteric femur fracture to determine the optimal trochanteric entry site. SETTING: OSHA-approved cadaveric laboratory with an OEC 9800 (General Electric Company, Fairfield, CT) fluoroscopic C-arm. METHODS: Twenty-one embalmed human cadaveric femurs were stripped of soft tissues. Three different starting points on the anteroposterior radiograph were used: at the tip of the greater trochanter, and 2 to 3 mm medial and lateral to the tip. A reverse obliquity subtrochanteric fracture was created. The Trochanteric Antegrade Nail (TAN), Gamma nail (2nd and 3rd generations), Trochanteric Fixation Nail (TFN), and the Holland Nail were then inserted. The proximal bend and radius of curvature were calculated for each nail. Varus and valgus angulation as well as lateral gapping were measured on radiographs; also calculated were the mean, range, and standard deviation. Statistical analysis was performed on angulation and gapping at the fracture site by using Fisher least significant differences analysis, based on a 2-way ANOVA test. RESULTS: The Holland nail had a proximal bend of 10 degrees and a radius of 300 cm. TAN was 5 degrees and 350 cm, TFN was 6 degrees and 150 cm, Gamma 2 was 4 degrees and 300 cm, and Gamma 3 was 4 degrees and 200 cm. The tip starting point led to the most neutral alignment regardless of nail. The lateral starting point led to varus with all nails. The medial starting point led to valgus of >6 degrees with the Holland and TFN; Gamma and TAN had better alignment with <4 degrees of valgus. Gapping of the lateral cortex was greatest with a lateral starting point. CONCLUSIONS: An analysis of 5 trochanteric intramedullary nails with different proximal bends and 3 different starting points in the greater trochanter showed that the tip of the trochanter is close to the "universal" starting point. In this cadaveric subtrochanteric fracture model, the tip starting point led to the most neutral alignment regardless of nail used. The lateral starting point led to varus and gapping of the lateral cortex with all nails. CLINICAL RELEVANCE: Subtrochanteric fractures treated with a trochanteric antegrade nail should have an acceptable reduction before nail insertion. The tip of the trochanter, or even slightly medial, on anteroposterior fluoroscopy is recommended as the universal starting point for these nails. However, slight deviations from this point and nail geometry can cause fracture site malalignment. A lateral starting point led to varus alignment and should be avoided.     

Use of a modified IMHS for unstable intertrochanteric fractures

The treatment of unstable intertrochanteric fractures in elderly osteopenic patients, especially those who cannot follow limited weight bearing instructions, is controversial. Recent publications indicate concern with excessive sliding of telescoping nail or sliding screw devices when used in these unstable intertrochanteric fractures. In our experience with the use of intramedullary hip screw (IMHS) in these fracture patterns, we have observed excessive sliding and collapse of the fracture in some patients. We modified the keyed centering sleeve by threading its internal distal third and substituted the compression screw with a custom bolt to obtain restricted sliding or rigid fixation depending on the gap between the lag screw and custom bolt. We used this modified system in static configuration to treat five patients who had an unstable intertrochanteric fracture of the femur. The length of the involved limb measured at the time of consolidation showed no shortening. In view of these results, intertrochanteric hip fractures that are unstable in patients with poor bone-stock can be fixed using the modified IMHS in a static or controlled sliding configuration. Received: 4 February 2002/Accepted: 18 March 2002     

Intramedullary fixation of unstable intertrochanteric hip fractures: one or two lag screws

OBJECTIVE: To compare the screw sliding characteristics and biomechanical stability of four-part intertrochanteric hip fractures stabilized with an intramedullary nail using either one large-diameter lag screw (intramedullary hip screw [IMHS]; Smith & Nephew, Memphis, TN) or two small-diameter lag screws (trochanteric antegrade nail [TAN]; Smith & Nephew, Memphis, TN). DESIGN: Laboratory investigation using eight matched pairs of cadaveric human femurs with simulated, unstable intertrochanteric hip fractures. INTERVENTION: One femur of each matched pair was stabilized with an IMHS intramedullary nail, and the other was stabilized with a TAN intramedullary nail. Femurs were statically, then cyclically loaded on a servohydraulic materials testing machine. Finally, all specimens were loaded to failure. MAIN OUTCOME MEASURES: Screw sliding and inferior and lateral head displacements were measured for applied static loads from 500N to 1250N. The same measurements were obtained before and after cyclically loading the specimens at 1250N. Ultimate failure strength of the implant constructs also was determined. RESULTS: There was no significant difference between the TAN and IMHS in static or cyclical loading with respect to screw sliding or inferior and lateral head displacements. There was a statistically significant difference (P < 0.02) in failure strength, with the IMHS construct failing at an average of 2162N and the TAN construct failing at an average of 3238N. CONCLUSION: The two constructs showed equivalent rigidity and stability in all parameters assessed in elastic and cyclical tests. The TAN had a greater ultimate failure load.     

A comparison of the Brooker-Wills and Russell-Taylor nails for treatment of patients who have fractures of the femoral shaft

Seventy-three fractures of the femoral shaft (seventy patients) were randomized to treatment with interlocked nailing with either the Brooker-Wills femoral nail (thirty-nine fractures) or the Russell-Taylor femoral nail (thirty-four fractures). Sixty-one patients (sixty-four fractures) were prospectively followed from admission until healing of the fracture. Specific attention was paid to recording operative details, including technical difficulties associated with insertion of the nails. Technical difficulties were encountered in insertion of the proximal screw, distal screw, and nail, and in deployment of the fins. Insertion of the Russell-Taylor nail was associated with less technical difficulty, operative time, and estimated loss of blood. The two nails differ in their biomechanical properties, methods of fixation, and instrumentation. These differences did not affect the clinical outcome; the fractures in both groups of patients healed with excellent functional results.     

Hybrid screw fixation for femoral neck fractures: Does it prevent mechanical failure?

IntroductionTraditionally, femoral neck fracture fixation has been performed using three partially threaded cancellous screws. However, fracture collapse with femoral neck shortening, and varus deformation frequently occurs due to posterior medial comminution and lack of calcar support. We hypothesize replacing the inferior neck/calcar screw with a fully threaded, length stable, screw will provide improved biomechanical stability, decrease femoral neck shortening and varus collapse.MethodsTen matched cadaveric pairs (20 femurs) were randomly assigned to two screw fixation groups. Group 1 (Hybrid) utilized one fully threaded calcar screw & two partially threaded superior screws. Group 2 (PT) utilized all partially threaded screws. Specimens underwent standardized femoral neck osteotomies, 45° from the horizontal, with 5 mm posteromedial wedge removed to simulate posteromedial comminution. Screws were placed using fluoroscopic guidance. Specimens were biomechanically tested using two loading sequences: 1) Axial load applied up to 700 N, followed by cyclic loading at 2 Hz with loads of 700 to 1,400 N for 10,000 cycles. 2) All surviving constructs were cyclically loaded to failure in stepwise incremental manner with max load of 4,000 N. Paired t-tests used to compare stiffness, cycles to failure, and max load to failure (defined as 15 mm load actuator displacement).ResultsConstruct stiffness was 2848 ± 344 N/mm in PT vs. 2767 ± 665 for Hybrid (P = 0.628). Load to failure demonstrated, hybrid superiority with max cycles to failure (3797 ± 400 cycles) vs. (2981 ± 856 cycles in PT) (p = 0.010), and max load prior to failure (3290 ± 196 N) vs. (2891 ± 421 N in PT) (p = 0.010). No significant difference in bone mineral density was noted in any of the specimens.ConclusionsOur study is the first to assess the biomechanical effects of hybrid fixation for femoral neck fractures. Hybrid screw configuration resulted in significantly stronger constructs, with higher axial load and increased cycles prior to failure. The advantageous mechanical properties demonstrated using a fully threaded inferior calcar screw provides a length stable construct which may prevent the common complication of excessive femoral neck shortening, varus collapse and poor functional outcome.     

Cephalomedullary fixation for intertrochanteric fractures: an operative technical tip

Intertrochanteric fracture is the most common hip fractures in elderly population. Cephalomedullary fixation, including proximal femoral nail antirotation (PFNA) and gamma nail, is commonly used in the treatment of intertrochanteric fractures. One of difficulties encountered in operation is insertion of the guide wire to femoral head. The guide wire would always bend and flow superiorly away from femoral calcar, and the lag screw and helical blade will follow the track and get into superior part of femoral head, not into femoral calcar. Here, we are presenting a surgical technique to direct the guide wire to right track. When guide wire just passed the tack hole of the nail, the rod of nail was slightly tapped down further to allow the superior border of the tack hole to touch the guide wire. Therefore, the superior border of the tack hole can be used as presser to prevent the wire from deviating upward. Through this way, the lag screw and helical blade get a good purchase that docked at femoral calcar. After that, the rod of nail was pulled back a little to make the wire in the middle of the tack hole, which can facilitate the insertion of the PFNA blade or lag screw. Our experience demonstrated that this surgical technique reduced the intraoperative risk for patients.     

Initial femoral stem position in cementless bipolar hemiarthroplasty for femoral neck fracture in elderly patients is associated with early implant subsidence: A radiographic analysis

BackgroundBipolar hemiarthroplasty is a well-established treatment for displaced femoral neck fracture in elderly patients. Implant subsidence is a potential complication with cementless femoral stems, and smaller canal fill ratio has been reported as a radiographic risk factor. We aimed to determine the risk factors for subsidence, particularly the initial implant position relative to the resected medial calcar of proximal femur.MethodsWe retrospectively reviewed all cementless bipolar hemiarthroplasties performed using a single proximally hydroxyapatite-coated femoral stem in patients with a minimum radiographic follow-up of 12 weeks between January 2017 and December 2018. The amount of subsidence (significant subsidence defined as ≥ 5 mm), canal fill ratio, and implant position relative to the point of resected medial calcar (position A: medial and superior to calcar; position B: lateral and superior to calcar; position C: lateral and inferior to calcar) were measured and analyzed.ResultsOne-hundred eighty patients were identified (mean age: 80.9 years). Significant subsidence was observed in 52 patients (28.9%). On multivariate analysis, older age, lower canal fill ratio, implant position B, C, and less medial overhang of stem were independent risk factors for early implant subsidence. The risk ratio of position B and C to position A was 5.13 (95% confidence interval, 2.23-11.80).ConclusionIn our analysis, older age and lower canal fill ratio were associated with increased risk of subsidence, whereas implant with position A and more medial overhang were less prone to subsidence with the tapered proximally hydroxyapatite-coated implant.