Mechanical Factors Responsible for the Obstruction of the Gliding Mechanism of a Dynamic Hip Screw for Stabilizing Pertrochanteric Femoral Fractures

Sim, Ernst; Schmiedmayer, Heinz-Bodo; Lugner, Peter

doi:10.1097/00005373-200012000-00003

Cited by 9 publications

(7 citation statements)

References 18 publications

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“…32 Mechanical testing for fixation stability may use static or dynamic cyclic compression, and each has achieved individual support. [33][34][35] In the current study, static and dynamic cyclic compressions achieved consistent results. A femoral locked nail was superior to a tibial locked nail.…”

Section: E494supporting

confidence: 71%

Retrograde Nailing of a Femoral Supracondyle

Wu¹,

Tai²

2012

Orthopedics

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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.

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Section: E494supporting

confidence: 71%

Retrograde Nailing of a Femoral Supracondyle

Wu¹,

Tai²

2012

Orthopedics

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“…Assuming that the anchorage of the lag screws in the femoral head of both implants is similar, the difference must be caused by collapse or impaction of the fracture rather than migration of the screws. A different sliding mechanism of the hip screw through the nail 4,40,41 may play a role. One of the factors which influences this mechanism is the type of metal used: titanium (PFN) has a lower friction coefficient than stainless steel (GN).…”

Section: Discussionmentioning

confidence: 99%

Treatment of unstable trochanteric fractures

Schipper

Steyerberg

Castelein

et al. 2004

The Journal of Bone and Joint Surgery. British volume

230

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The proximal femoral nail (PFN) is a recently introduced intramedullary system, designed to improve treatment of unstable trochanteric fractures of the hip. In a multicentre prospective clinical study, the intra-operative use, complications and outcome of treatment using the PFN (n = 211) were compared with those using the gamma nail (GN) (n = 213). The intra-operative blood loss was lower with the PFN (220 ml v 287 ml, p = 0.001). Post-operatively, more lateral protrusion of the hip screws of the PFN (7.6%) was documented, compared with the gamma nail (1.6%, p = 0.02). Most local complications were related to suboptimal reduction of the fracture and/or positioning of the implant. Functional outcome and consolidation were equal for both implants. Generally, the results of treatment of unstable trochanteric fractures were comparable for the PFN and GN. The pitfalls and complications were similar, and mainly surgeon- or fracture-related, rather than implant-related.

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“…The clinical treatments of the femur fractures can be numerically assessed. Biomechanical studies on the lag screw positions usually evaluate only the positions of S, M, and I regions [7, 24] as shown in Figure 3 contrary to many clinical studies [5, 10–12]. There is no biomechanical or clinical study about how fracture types affect the cut-out risk in different lag screw positions according to our literature search.…”

Section: Discussionmentioning

confidence: 99%

“…However, which positions of the lag screw in the femoral head increase the cut-out risk and implant failure is still a controversial subject. Some researchers recommend the central placement [5], but others suggest the inferior and inferior posterior region in the lateral view [3, 6, 7]. Some authors believe that the cut-out risk in posterior (P) region is lower compared to the other region [4].…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Lag Screw Placements for the Treatment of Stable and Unstable Intertrochanteric Femoral Fractures regarding Trabecular Bone Failure

Çelik

Mutlu

Özkan

et al. 2016

Journal of Medical Engineering

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Background. In this study, the cut-out risk of Dynamic Hip Screw (DHS) was investigated in nine different positions of the lag screw for two fracture types by using Finite Element Analysis (FEA). Methods. Two types of fractures (31-A1.1 and A2.1 in AO classification) were generated in the femur model obtained from Computerized Tomography images. The DHS model was placed into the fractured femur model in nine different positions. Tip-Apex Distances were measured using SolidWorks. In FEA, the force applied to the femoral head was determined according to the maximum value being observed during walking. Results. The highest volume percentage exceeding the yield strength of trabecular bone was obtained in posterior-inferior region in both fracture types. The best placement region for the lag screw was found in the middle of both fracture types. There are compatible results between Tip-Apex Distances and the cut-out risk except for posterior-superior and superior region of 31-A2.1 fracture type. Conclusion. The position of the lag screw affects the risk of cut-out significantly. Also, Tip-Apex Distance is a good predictor of the cut-out risk. All in all, we can supposedly say that the density distribution of the trabecular bone is a more efficient factor compared to the positions of lag screw in the cut-out risk.

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Mechanical Factors Responsible for the Obstruction of the Gliding Mechanism of a Dynamic Hip Screw for Stabilizing Pertrochanteric Femoral Fractures

Abstract: Complete agreement was found between the results of the presented calculations and our own clinical experience in removed DHSs.

Cited by 9 publications

References 18 publications

Retrograde Nailing of a Femoral Supracondyle

Retrograde Nailing of a Femoral Supracondyle

Treatment of unstable trochanteric fractures

Comparison of the Lag Screw Placements for the Treatment of Stable and Unstable Intertrochanteric Femoral Fractures regarding Trabecular Bone Failure

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