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Osteonecrosis of the femoral head, nonunion and potential risk factors in Pauwels grade-3 femoral neck fractures

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ABSTRACT

The present study was to analyze clinical outcome of Pauwels grade-3 femoral neck fractures treated by different surgical techniques. Potential risk factors associated with nonunion and osteonecrosis of the femoral head (ONFH) were investigated as well. The retrospective study comprised of 67 sequential patients treated between January 2008 and December 2011. Patients with Pauwels grade-3 femoral neck fractures were treated by operative reduction and internal fixation. Cannulated screws (CS) were used in 46 patients, dynamic hip screw plus CS (DHS+CS) in 14, and locking compression plate (LCP) for proximal femur in 7. Reduction quality was assessed according to Haidukewych criteria. Postoperative radiographic examinations were conducted to observe fracture healing. Fracture displacement, comminution, fashion of internal fixation, and the sliding effect were analyzed, regarding the incidence of nonunion and ONFH. All patients had a follow-up of 21.6 ± 6.0 months on average. The phenomenon of sliding effect was observed in 16 cases (23.9%). In terms of reduction quality, 64 cases were graded as excellent, 2 were good, and 1 was poor. ONFH was presented in 15 cases (22.4%) and nonunion was found in 8 (11.9%), with 1 patient had ONFH and nonunion concomitantly. Profound hip contour was preserved in 45 cases (67.2%). The fashion of internal fixation yielded different results regarding ONFH and nonunion, whereas the effects of fracture displacement, comminution, and the sliding effect were not significant. ONFH and nonunion were common complications following Pauwels grade-3 femoral neck fractures. Higher incidence of ONFH in DHS+CS and of nonunion in the LCP group should be noted.

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Schematic diagram of Pauwels angle. When the angle of the integrated projection of fracture line and horizontal line is >50°, the force between the fracture fragments mainly consists of shearing force (S), which is unfavorable to fracture healing.
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Figure 1: Schematic diagram of Pauwels angle. When the angle of the integrated projection of fracture line and horizontal line is >50°, the force between the fracture fragments mainly consists of shearing force (S), which is unfavorable to fracture healing.

Mentions: The Pauwels’ classification of femoral neck fracture was introduced in 1935. The Pauwels classification categories femoral neck fractures into 3 grades according to the fracture angle, namely, the angle <30° as Pauwels grade 1, the angle between 30° and 50° as Pauwels grade 2, and the angle >50° as Pauwels grade 3 (Fig. 1).[8] Another method to category femoral neck fracture is Garden classification, which has 4 grades based on fracture displacement. Different from the Garden method with the greatest popularity, Pauwels’ classification is mainly based on morphological fracture line and does not consider other factors such as the displacement of fractured fragments. As a result, it is not used as widely as Garden's classification method. However, in the aspect of the biomechanics of fracture healing, Pauwels’ classification is of great value.[9,10] In Pauwels grade-1 femoral neck fracture, compression is predominant. However, in Pauwels grade 3, the shearing force dominates the microenvironment and is associated with a significant varus force, which usually results in fracture displacement and varus collapse. Given the implants cannot overcome the shearing until fracture healing, nonunion and implant failure is inevitable. The shearing force also harms the restoration of blood supply to the femoral head, yielding higher incidence of osteonecrosis of the femoral head (ONFH).


Osteonecrosis of the femoral head, nonunion and potential risk factors in Pauwels grade-3 femoral neck fractures
Schematic diagram of Pauwels angle. When the angle of the integrated projection of fracture line and horizontal line is >50°, the force between the fracture fragments mainly consists of shearing force (S), which is unfavorable to fracture healing.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4998436&req=5

Figure 1: Schematic diagram of Pauwels angle. When the angle of the integrated projection of fracture line and horizontal line is >50°, the force between the fracture fragments mainly consists of shearing force (S), which is unfavorable to fracture healing.
Mentions: The Pauwels’ classification of femoral neck fracture was introduced in 1935. The Pauwels classification categories femoral neck fractures into 3 grades according to the fracture angle, namely, the angle <30° as Pauwels grade 1, the angle between 30° and 50° as Pauwels grade 2, and the angle >50° as Pauwels grade 3 (Fig. 1).[8] Another method to category femoral neck fracture is Garden classification, which has 4 grades based on fracture displacement. Different from the Garden method with the greatest popularity, Pauwels’ classification is mainly based on morphological fracture line and does not consider other factors such as the displacement of fractured fragments. As a result, it is not used as widely as Garden's classification method. However, in the aspect of the biomechanics of fracture healing, Pauwels’ classification is of great value.[9,10] In Pauwels grade-1 femoral neck fracture, compression is predominant. However, in Pauwels grade 3, the shearing force dominates the microenvironment and is associated with a significant varus force, which usually results in fracture displacement and varus collapse. Given the implants cannot overcome the shearing until fracture healing, nonunion and implant failure is inevitable. The shearing force also harms the restoration of blood supply to the femoral head, yielding higher incidence of osteonecrosis of the femoral head (ONFH).

View Article: PubMed Central - PubMed

ABSTRACT

The present study was to analyze clinical outcome of Pauwels grade-3 femoral neck fractures treated by different surgical techniques. Potential risk factors associated with nonunion and osteonecrosis of the femoral head (ONFH) were investigated as well. The retrospective study comprised of 67 sequential patients treated between January 2008 and December 2011. Patients with Pauwels grade-3 femoral neck fractures were treated by operative reduction and internal fixation. Cannulated screws (CS) were used in 46 patients, dynamic hip screw plus CS (DHS+CS) in 14, and locking compression plate (LCP) for proximal femur in 7. Reduction quality was assessed according to Haidukewych criteria. Postoperative radiographic examinations were conducted to observe fracture healing. Fracture displacement, comminution, fashion of internal fixation, and the sliding effect were analyzed, regarding the incidence of nonunion and ONFH. All patients had a follow-up of 21.6&#8202;&plusmn;&#8202;6.0 months on average. The phenomenon of sliding effect was observed in 16 cases (23.9%). In terms of reduction quality, 64 cases were graded as excellent, 2 were good, and 1 was poor. ONFH was presented in 15 cases (22.4%) and nonunion was found in 8 (11.9%), with 1 patient had ONFH and nonunion concomitantly. Profound hip contour was preserved in 45 cases (67.2%). The fashion of internal fixation yielded different results regarding ONFH and nonunion, whereas the effects of fracture displacement, comminution, and the sliding effect were not significant. ONFH and nonunion were common complications following Pauwels grade-3 femoral neck fractures. Higher incidence of ONFH in DHS+CS and of nonunion in the LCP group should be noted.

No MeSH data available.


Related in: MedlinePlus