Mechanical analysis of femoral neck fracture fixation with dynamic condylar screw in synthetic bone

Gang

2020

Preprint

Background This study purposed to compare the partial- threaded cannulated screws (PTCS) and the double-threaded cannulated screws (DTCS) in vertical shear femoral neck fractures both clinically and biomechanically. Methods Clinally, the radiographs of 81 patients with Pauwels Ⅲ femoral neck fractures, including 54 fractures fixed with PTCS and 27 fractures fixed with DTCS were analyzed. Complications consist of fixation failure (nail withdrawal, obvious fracture displacement, varus deformity or femoral neck shortening), bony nonunion and avascular necrosis (AVN) were determined. Biomechanically, twenty femur synthetic bones were equally divided and made to a vertical femoral neck fracture model, then fixed with three parallel PTCSs or DTCSs respectively. All specimens were tested for axial stiffness and a maximum load to failure with a loading rate of 2 mm/min. Results Clinically , 22 fractures in the PTCS group experienced fixation failure, including 19 nail withdrawal, 18 femoral neck shortening, 14 varus deformity and 8 obvious fracture displacement; while only 5 fractures showed up with fixation failure in the DTCS group, including 3 nail withdrawal, 4 femoral neck shortening, 4 varus deformity and 1 obvious fracture displacement. Additionally, 11 fractures in the PTCS group had nonunion while only 3 in the DTCS group and 9 fractures with AVN in the PTCS group while only 2 in the DTCS group. Biomechanically, The axial stiffness of DTCS was 152.89±22.74 N/mm, greater than PTCS (134.68±26.61), moreover, the failure load in DTCS was significantly greater than PTCS (1148.11±124.80 vs 795.88±162.50). Conclusion DTCS may exert more advantages than PTCS for vertical femoral neck fractures, including stronger fixation stability, lower rate of fixation failure and nonunion.

Section: Discussionmentioning

confidence: 99%

A comparative study of partial-threaded cannulated screws and double-threaded cannulated screws in the fixation of vertical femoral neck fractures

Gang

2020

Preprint

Journal of Orthopaedic Translation

Section: Discussionmentioning

confidence: 99%

“…Although the DCS provides strong stability at the fracture site [14], [15], it is infrequently used in the treatment of Pauwel's Type III femoral neck fractures because it promotes bone healing [23]. A Sawbone biomechanical study has showed that the DCS can stabilize Pauwel's Type III femoral neck fractures [15]. Although compared with the proximal femoral locking plate, the DCS offers less stability comfort for femoral neck Pauwel's Type III fractures; the proximal femoral locking plate fails to allow fracture compression at the fracture site, which may negatively affect femoral neck healing [14].…”

Section: Discussionmentioning

confidence: 99%

“…Dynamic condylar screw (DCS) can provide strong stability at the fracture site for the treatment of Type III femoral neck fractures [14], [15], and the proximal femoral medial plate can effectively resist shear force [16], [17]. The combination of the DCS and proximal femoral medial plate provides more stability at the fractures sites for femoral neck nonunion.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Treatment of femoral neck nonunion with a new fixation construct through the Watson-Jones approach

Chen

Chang

et al. 2019

ObjectiveThe aim of the study is to explore the clinical effect of a dynamic condylar screw (DCS) system, medial anatomical buttress plate (MABP), and autogenous iliac bone graft through the Watson-Jones approach in the treatment of femoral neck nonunion.MethodsThis prospective study included 15 patients (12 men and 3 women) with nonunion of femoral neck fracture, who were treated with the DCS and MABP with autogenous iliac bone graft through the Watson-Jones approach. The patients were followed up for an average of 16 months (range, 12–24 months).ResultsAll patients achieved bone healing with an average fracture healing time of 3.4 months (2.8–4.6 months). The Harris score significantly increased from 30 ± 3.9 before the operation to 87.6 ± 7.9 at the last follow-up, and the visual analogue scale significantly decreased from 4 ± 1.3 before the operation to 1 ± 1.7 at the last follow-up. The average limb shortening was reduced from 1.8 cm (range, 0–3.1 cm) before the revision operation to 0.5 cm (range, 0.1–1.3 cm) after the last follow-up. The neck-shaft angle of the injured side was restored from an average of 118° (range, 108–139°) before the revision operation to an average of 132° (range, 127–144°) at the last follow-up. No collapse of the femoral head, wound infections, screw backout, screw or plate breakages, or nerve injury was found.ConclusionTheDCS and MABP with autogenous iliac bone graft through the Watson-Jones approach is an effective option for the treatment of femoral neck nonunion or delayed healing.The translational potential of the articleThis article shows that the application of DCS and MABP provides a rigid fixation at the fracture site to promote bone graft integration and bone union. This new kind of technique could be one option of Hip conservation procedures, just special for young patients with femoral neck nonunion.

“…Pauwels III). 1,4–9 These fractures are inherently unstable and have high rates of complications including nonunion, reoperation, and avascular necrosis (AVN) of the femoral head; this latter complication can be as high as 86%. 4,6,10–13 While the current treatment for AVN of the femoral head is hip arthroplasty, this treatment is not ideal in the young adult.…”

Section: Introductionmentioning

confidence: 99%

A model to evaluate Pauwels type III femoral neck fractures

Magone

Owen

Kemker

et al. 2018

Proc Inst Mech Eng H

While many femoral neck fractures can be reliably treated with surgical intervention, Pauwels III femoral neck fractures in the young adult population continue to be a challenging injury, and there is no consensus on optimal treatment. As such, there are past and ongoing biomechanical studies to evaluate the fixation provided by different constructs for this inherently unstable fracture. While many investigations rely on cadavers to evaluate the biomechanical performance of a construct, significant inter-subject variability can confound the analysis. Biomechanical femur analogs are being used more frequently due to more consistent mechanical properties; however, they have not been stringently evaluated for morphology or suitability for instrumentation. This study sought to determine the variability among composite femoral analogs as well as consistently create a Pauwels III injury and instrument the analogs without the need for fluoroscopic guidance. In total, 24 fourth-generation composite femoral analogs were evaluated for femoral height, neck-shaft angle, anteversion, and cortical thickness. A method was developed to simulate a Pauwels III fracture and to prepare three different constructs: an inverted triangle of cannulated screws, a sliding hip screw, and a hybrid inverted triangle with cannulated screws and a sliding hip screw. Radiographs were utilized to evaluate the variation in implant position. All but one of the morphological parameters varied by <1%. The tip-to-apex distance for all sliding hip screw hardware was 18.8 ± 3.3 mm, and all relevant cannulated screw distances were within 5 mm of the adjacent cortex. All screws were parallel, on average, within 1.5° on anterior-posterior and lateral films. Fourth-generation composite femora were found to be morphologically consistent, and it is possible to consistently instrument the analogs without the use of fluoroscopy. This analog and hardware implantation model could serve as a screening model for new fracture repair constructs without the need for cadaveric tissues or radiologic technology.