Views: 12 Author: Site Editor Publish Time: 2022-08-12 Origin: Site
Periprosthetic fractures of the proximal femur are a serious problem in hip arthroplasty. The reported incidence is 3.5% 20 years after initial implantation and increases with the incidence of joint replacements. Intraoperative fractures are often associated with uncemented stems. More commonly, fractures occur in frail older adults who have fallen secondary to surgery. Although there are international differences in the use of cemented and uncemented stems, there is no clear evidence that one type of cemented stem is associated with a higher fracture risk than the other. The Vancouver classification system for periprosthetic femoral fractures has been widely adopted by surgeons and has been shown to be reliable.
The primary objective of this study was to determine the relationship between the Vancouver classification of cemented and uncemented stem fractures. The second objective was to investigate differences in baseline characteristics of patients with the two fracture types.
A series of patients with consecutive proximal periprosthetic fractures.
Only patients with primary hip periprosthetic fractures were included.
Patients with intraoperative fractures, revision hip fractures, and interprosthetic fractures were excluded.
Digital radiography and computed tomography based on electronic documentation and analysis.
Baseline details recorded included age, sex, body mass index, and decreased mobility prior to onset or caregiver dependence.
Time to first implantation, indication for arthroplasty (osteoarthritis or fracture), type of stem (cemented or uncemented), and type of arthroplasty (total or semiarthroplasty) were included.
Detailed imaging records included Vancouver classification, varus vertebral position, and Dorr classification.
Stem geometry (conical or compound for cemented stems, straight or wedge-shaped for uncemented stems) was recorded based on the radiographic appearance.
Determination of the Vancouver classification was based on imaging findings and intraoperative findings in surgical patients.
Statistical analyses were performed using continuous variables T-test and Fisher's exact test for categorical variables to compare baseline characteristics and Vancouver classification of patients in the cemented and uncemented stem groups.
All trials were two-sided with a significance level of 0.05. Statistical analysis was performed using GraphPad Prism version 8.0.0.
A total of 1181 patients were identified by querying the hospital database.
978 patients with non-periprosthetic proximal femur fractures were excluded.
Among the remaining 203 patients, 8 had intraoperative fractures, 6 had revision periprosthetic fractures, and 17 had periprosthetic fractures of the hip joint fixation device, which were further excluded.
A total of 172 patients were included after exclusion.
All fractures occurred after a fall. Femoral stem bone cement group fractures in 84 cases without cement
There were 88 fractures in the group.
There were significant differences between groups in age, time to first implantation, indications for arthroplasty for femoral neck fractures, primary hemiarthroplasty, varus stem placement, and body mass index.
In particular, in the cement group, the majority were hemiarthroplasty.
There were no significant differences between groups with respect to sex, Dorr classification, and decreased premorbid mobility or caregiver dependence.
In the cemented group, most stems were tapered and the rest were composite designs.
In the uncemented group, most stems were straight and the rest were wedge-shaped.
VancouverB2 fractures are classified into four distinct fracture patterns: the previously described comminuted "burst", clamshell, and helical patterns, and the newly observed "reverse" clamshell pattern. A representative X-ray appearance of the series and corresponding graphical depiction are shown (Figure 1).
Burst and spiral fractures were significantly associated with cemented stems, whereas flap fractures were significantly associated with uncemented stems.
The reverse clamshell pattern occurred similarly in both stems.
The association of the Vancouver classification subtypes, including the four B2 fracture types described above, with stem geometry reflects the general trend in fracture types.
To date, this is the largest study to directly compare the relationship between cemented and uncemented stem periprosthetic fractures and the Vancouver classification:
There was no significant difference in the correlation between cemented and uncemented stems in Vancouver type A, B, or C fractures. The incidence of VancouverB2 fractures was the same in both groups, indicating the same incidence of stable and unstable stems in periprosthetic fractures in both groups.
In contrast, Fenelon et al. analyzed periprosthetic fractures with cemented and uncemented stems. It is clear that the number of patients with fractures in Vancouver B2 and B3 is significantly higher.
Phillips et al. describe a highly comminuted "burst" pattern of conical cement stem segments and "crack" along the cement jacket, similar to an "axe head". This fracture was found to be significantly associated with cemented stems in this study.
The high comminuted nature of these fractures raises concerns about bone deactivation, and these fractures often require careful removal of cement and bypassing with a distal bearing stem.
Capello et al. described a "flip-flop" fracture associated with uncemented stems, and the findings reflect this finding. The fracture originates from the medial base of the greater trochanter, extends to the medial cortex, and preserves the lateral cortex, distal to the lesser trochanter. Enlargement of the talar region and subsidence of the stem are radiographic signs of stem instability. Previous studies have shown a significant association of this fracture with uncemented stems with anatomical and wedge-shaped designs, and this study supports this association.
Grammatopolous et al describe a series of helical fracture patterns in periprosthetic fractures with cemented stems, usually associated with isolated wedge fragments and severe comminution. The number of helical fractures in the cemented stem was significantly increased in this series, which may reflect the tendency of fractures around the tubular cemented stem to propagate in a manner similar to natural bone.
In a radiographic analysis of a large number of periprosthetic fractures, the research team observed a fracture pattern not previously described in the literature. The fracture originates from the medial calcar passing through the lateral cortex, leaving the medial cortex intact. This type of fracture is called a "reverse" clamshell fracture, which the study considered a common Vancouver B2 fracture.
This name was chosen for two reasons: first, it is a mirror image of the "flip", and second, it behaves like a reverse oblique proximal femoral fracture, with a similar supralateral displacement of the abductor pulling the proximal fragment . Similar fractures occurred with cemented and uncemented stems (Figure 2).
Although the purpose of this study was not to investigate treatment outcomes, in this study, reverse flip-flop fractures were typically revised with an arthroplasty of the distal load-bearing stem and fixation of the proximal fracture fragments with cerclage wires or plates.
An example of a patient treated with this approach is shown, showing the achievement of healing (Figure 3).
Figure 2 Reverse flip-top fracture pattern.
Figure 3 Arthroplasty and cerclage wire fixation for retrograde flap fractures.
According to the Vancouver classification system, periprosthetic fracture types have the same incidence of periprosthetic fractures in cemented and uncemented prostheses. Therefore, the incidence of stable and unstable stems after fracture was equal in the two groups. Identifying four distinct VancouverB2 fracture patterns, including the newly observed inverted flip-flop pattern, will help surgeons identify stem instability. Future studies are needed to investigate the relationship between fracture type and treatment strategy to determine the clinical significance of the findings of this study.
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