Should cannulated screws be removed after a femoral neck fracture has healed, and how? A finite element analysis of the femur before and after cannulated screw removal

Wu, Lianghong; Sun, Jun; Fang, Nan; Peng, Miao; Gao, Shuo; Liu, Lifeng

doi:10.1007/s00264-022-05516-9

Cited by 4 publications

(7 citation statements)

References 27 publications

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“…It is hypothesized that the mechanical damage of the surrounding intraosseous blood system induced by the screw threads during screw removal may contribute to increasing the risk of aggravation or occurrence of AVN of the femoral neck. Previous studies have shown that incorrect screw removal and the consequent increase in femoral load may be correlated with the occurrence of AVN or refracture; however, these findings have so far only been shown in cohorts of adult patients 18–21 . In particular, in patients with AVN, the presence of particularly vulnerable vascular structures and the reduced number of vessels predisposes to a decreased blood supply to the femoral head during the process of removing hardware 22,23 .…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies have shown that incorrect screw removal and the consequent increase in femoral load may be correlated with the occurrence of AVN or refracture; however, these findings have so far only been shown in cohorts of adult patients. [18][19][20][21] In particular, in patients with AVN, the presence of particularly vulnerable vascular structures and the reduced number of vessels predisposes to a decreased blood supply to the femoral head during the process of removing hardware. 22,23 Several studies have reported similar findings indicating that the intraosseous vascular system can be damaged to varying degrees during implant insertion.…”

Section: Discussionmentioning

confidence: 99%

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The Duration of Hardware Retention After Radiologic Union of Surgically Treated Femoral Neck Fractures in Children May Predict the Aggravation or Occurrence of Avascular Necrosis of the Femoral Head or Neck After Hardware Removal

Wang,

Mei,

Guo

et al. 2023

Journal of Pediatric Orthopaedics

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Background: The incidence of aggravation or occurrence of avascular necrosis (AVN) following hardware removal in surgically treated pediatric femoral neck fractures who achieved radiologic consolidation is unknown. This study aimed to investigate the risk factors for this complication. Methods: Seventy-one pediatric (mean age: 9.8±3.9 y) were retrospectively analyzed. Risk factors (age, sex, laterality, severity of initial displacement, type of fracture, time from trauma to reduction, reduction and fixation method, quality of reduction, time required to achieve radiologic union, duration of hardware retention, presence of AVN before hardware removal and follow-up time) were recorded. The severity of AVN was assessed based on radiographs with Ratliff’s classification. Results: Following hardware removal, the aggravation/occurrence of AVN was detected in 11 hips (15.5%). Among the 5 hips (7%) with aggravation of AVN, 1 (1.4%) with type II AVN and 3 (4.2%) with type III AVN exhibited aggravation of type I AVN, while the remaining hip (1.4%; type I) showed enlargement of the involved AVN area. Six hips (8.5%) developed AVN following hardware removal: 2 (2.8%) were classified as type I and 4 (5.6%) as type III. Receiver operating characteristic curve analysis indicated that hardware retention >7 months after union is associated with a decreased rate of aggravation or occurrence of AVN of the femoral neck or head following hardware removal. Conclusions: The incidence of aggravation or occurrence of AVN following hardware removal in surgically treated pediatric femoral neck fractures is 15.5%; hardware retention >7 months after radiologic union may reduce the risk of aggravation or occurrence of AVN of the femoral neck or head postimplant removal. Level of evidence: Level III.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The Duration of Hardware Retention After Radiologic Union of Surgically Treated Femoral Neck Fractures in Children May Predict the Aggravation or Occurrence of Avascular Necrosis of the Femoral Head or Neck After Hardware Removal

Wang,

Mei,

Guo

et al. 2023

Journal of Pediatric Orthopaedics

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“…Finally, the surface underwent fitting, and a thorough deviation analysis was conducted. Based on the model in the published paper [ 10 , 11 ], we performed the CT gray value assignment method to optimize the simulation of the proximal femur bone. Following the completion of fitting the surfaced model, it underwent verification before being imported into SolidWorks 2017(Dassault, France).…”

Section: Methodsmentioning

confidence: 99%

“…In vitro experiments [ 9 ] indicated that removing hollow screws did not alter the maximum load of subsequent femoral neck fractures. Finite element experiments [ 10 ] further demonstrated that retained screws exhibited stress concentration and stress shielding effects. To our knowledge, there is currently limited research on mechanical experiments conducted after the removal of FNS.…”

Section: Introductionmentioning

confidence: 99%

Biomechanical changes in the proximal femur before and after removal of femoral neck system

Nan,

Liu,

Zhang

et al. 2024

J Orthop Surg Res

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Background As an innovative internal fixation system, FNS (femoral neck system) is increasingly being utilized by surgeons for the treatment of femoral neck fractures. At present, there have been numerous finite element analysis experiments studying the immediate stability of FNS and CSS in treating femoral neck fractures. However, there is scarce mechanical analysis available regarding the effects post internal fixation removal. This study aimed to investigate the alterations in mechanical parameters of the proximal femur before and after the removal of FNS (femoral neck system), and to assess potential distinctions in indicators following the extraction of CSS (Cannulated Screws). Methods A proximal femur model was reconstructed using finite element numerical techniques. The models for CSS and FNS were formulated utilizing characteristics and parametric definitions. The internal fixation was combined with a normal proximal femur model to simulate the healing state after fracture surgery. Within the framework of static analysis, consistent stress burdens were applied across the entirety of the models. The total deformation and equivalent stress of the proximal femur were recorded before and after the removal of internal fixation. Results Under the standing condition, the total deformation of the model before and after removing CSS was 0.99 mm and 1.10 mm, respectively, indicating an increase of 12%. The total deformation of the model before and after removing FNS was 0.65 mm and 0.76 mm, respectively, indicating an increase of 17%. The equivalent stress for CSS and FNS were 55.21 MPa and 250.67 MPa, respectively. The average equivalent stress on the cross-section of the femoral neck before and after removal of CSS was 7.76 MPa and 6.11 MPa, respectively. The average equivalent stress on the cross-section of the femoral neck before and after removal of FNS was 9.89 MPa and 8.79 MPa, respectively. Conclusions The retention of internal fixation may contribute to improved stability of the proximal femur. However, there still existed risks of stress concentration in internal fixation and stress shielding in the proximal femur. Compared to CSS, the removal of FNS results in larger bone tunnels and insufficient model stability. Further clinical interventions are recommended to address this issue.

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“…This approach has a minimal effect on the stress concentration at the proximal femur and the average stress on the femoral head. [35] Intertrochanteric fractures (ITFS) are among the most common fractures occurring in older people with osteoporosis. [36] As life expectancy continues to increase, the prevalence of ITFS also increases.…”

Section: The Importance Of the Calcar Femorale Reconstruction In The ...mentioning

confidence: 99%

Structural characteristics, biomechanics and clinical significance of calcar femorale: A review

Zhou,

Jia,

Lian

2024

Medicine

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The calcar femorale, first identified by Merkel in 1874, plays a pivotal role in the weight-bearing capacity of the proximal femur, and its structural integrity is crucial for the efficient distribution of mechanical loads. Originating at the vertical ridge where the pubofemoral ligament anchors, this bony prominence extends laterally behind the neutral axis from the medial to lateral aspects. Its presence is not merely an anatomical curiosity but significantly influences the biomechanics of the hip joint by providing additional strength and support against compressive forces encountered during activities such as walking or jumping. Despite its clear description in orthopedic texts, misconceptions persist about its exact function and importance. This article delves into the nuanced anatomy and biomechanical properties of the calcar femorale, offering a detailed literature-based examination that demonstrates its relevance in clinical practice. The review highlights how the robustness of the calcar femorale contributes to the prevention of femoral neck fractures as well as the stabilization of hip prostheses. Furthermore, the indispensable role of the calcar femorale in surgical outcomes is discussed, especially in the context of fracture repair and joint replacement, thus illustrating its enduring significance in contemporary medical applications.

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Should cannulated screws be removed after a femoral neck fracture has healed, and how? A finite element analysis of the femur before and after cannulated screw removal

Cited by 4 publications

References 27 publications

The Duration of Hardware Retention After Radiologic Union of Surgically Treated Femoral Neck Fractures in Children May Predict the Aggravation or Occurrence of Avascular Necrosis of the Femoral Head or Neck After Hardware Removal

The Duration of Hardware Retention After Radiologic Union of Surgically Treated Femoral Neck Fractures in Children May Predict the Aggravation or Occurrence of Avascular Necrosis of the Femoral Head or Neck After Hardware Removal

Biomechanical changes in the proximal femur before and after removal of femoral neck system

Structural characteristics, biomechanics and clinical significance of calcar femorale: A review

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