Abstract
Objective
Three‐dimensional (3D)‐CT data is currently insufficient for classifying femoral trochanter fractures. Fracture classification based on fracture stability analysis is helpful to evaluate the prognosis of patients after internal fixation. Currently, there is a lack of fracture classification methods based on 3D‐CT images and fracture stability analysis. The aim of this study was to propose a new six‐part classification method for intertrochanteric fractures of femur based on 3D‐CT images and fracture stability analysis to improve the diagnosis rate of unstable fractures.
Method
From January 2009 to December 2019, 320 patients receiving intramedullary nail surgery for femoral intertrochanteric fractures at Chengdu University's Affiliated Hospital were studied retrospectively. AO and six‐part classifications were undertaken according to the 3D‐CT image data of the patients, and the stability rates of two classifications were compared. According to the six‐part classification stability criteria, the patients were divided into a stable and an unstable fracture group. The perioperative and follow‐up indicators of the two groups were statistically analyzed, and the six‐part classification's inter‐observer and internal reliability was examined.
Results
There were 107 men and 213 females women the 320 patients, with an average age of 79.32 ± 11.26 years and an osteoporosis rate of 55.63% (178/320). The fracture stability rate of 39.69% (127/320) was studied using a six‐part classification method. The AO classification fracture stability rate was 42.50% (136/320), with no significant difference (χ 2 = 0.523, p = 0.470 > 0.05). There is no statistically significant difference between the two classification techniques in the examination of fracture stability (McNemer difference test p = 0.306 > 0.05; Kappa consistency test p < 0.001). According to the six‐part classification, fracture stability and instability group were divided into two groups. The following indicators were compared between the two groups: The surgery time (p = 0.280), fracture reduction quality (p = 0.062); function independent measurement (p = 0.075); timed up and go test (TUG) (p = 0.191), and Parker‐Palmer score (p = 0.146). Were as compared according to the six‐part classification of stable and unstable fracture groups. Perioperative blood loss (p < 0.001), the Harris score excellent and good rate (p = 0.043), fracture healing time (p < 0.001), and the entire weight‐bearing duration (p = 0.002) were statistically significant. The difference in femoral head height (FHH) (p = 0.046), the change in femoral neck shaft angle (p = 0.003), the change in medial cephalic nail length (p = 0.033), and the change in tip–apex distance (TAD) (p = 0.002) were statistically significant compared to the relevant markers of imaging stability. Fracture stability had a substantial influence on Harris ratings at 3, 6, and 12 months following surgery, according to repeated measures analysis of variance (F (1,126) = 32.604, p < 0.001). The effect of time on the Harris score was similarly significant (F (1.893,238.508) = 202.771, p < 0.001). The observer intra‐observer inter‐group correlation coefficient (ICC) value was 0.941 > 0.75, the inter‐observer ICC value was 0.921 > 0.75, and the intra‐observer and inter‐observer reliability were both good.
Conclusion
The six‐part classification of femoral intertrochanteric fractures based on 3D‐CT images has broader guiding relevance for femoral intertrochanteric fracture stability analysis. Clinicians will find this classification simpler and more consistent than the AO classification.
Keywords: AO Classification; Classification; Fracture, Intertrochanteric; Internal Fixation; Six‐Part Classification; Stability
In this study, a novel classification approach for the six‐part categorization of femoral intertrochanteric fractures was proposed based on 3D‐CT images and fracture stability analysis. AO and six‐part classifications were undertaken according to the 3D‐CT image data of the patients, and the stability rate of the two types of fractures was compared. According to the six‐part classification stability criteria, the patients were divided into a stable and an unstable fracture group. The perioperative and follow‐up indicators of the two groups were statistically analyzed. We examined the six‐part classification's inter‐observer and internal reliability.
Introduction
Femoral intertrochanteric fractures are among the most frequently occurring hip fractures. According to recent research, hip fractures affect around 7% of the senior population aged 75–84 years old within 10 years. 1 Intertrochanteric fractures account for up to 50% of hip fractures in China. 2 Conservative therapy for this type of fracture has a poor prognosis. The femoral intertrochanteric fracture is also known as the “final fracture in a person's life.” One year after an accident, the death rate is as high as 20%, which increases as patients age. 3 Surgical therapy should be started within 48 h after admission, according to the National Academy of Sciences Guidelines for the Diagnosis and Treatment of Femoral Intertrochanteric Fractures. 4 Dynamic hip screws or intramedullary nails can be used for stable fractures. 5 Intramedullary nail fixation is preferred for unstable fractures. 6 Intramedullary nail fixation is also preferred for reverse intertrochanteric fractures or subtrochanteric fractures. 7 Using imaging data to determine the stability of the fracture during preoperative preparation and surgical technique selection is a crucial element of selecting which internal fixation method to use. It might also be used to forecast the rate of internal fixation failure and assess the hip joint's function following surgery. 8 The AO and Evans–Jensen classification are now used to define and analyze the stability of intertrochanteric fractures. 9 However, these X‐ray‐based classification techniques primarily focus on the number of fractures and the orientation of fracture lines. As early as 1949, Professor Evans noted that the integrity of the medial wall (involvement of the lesser trochanter) was a major factor affecting the stability of coronal fractures. Some authors had reservations about this notion, arguing that a simple lesser trochanter fracture without involvement of the calcar femorale would not affect weight‐bearing function and would be considered a stable fracture. 10 Boyd and Griffin first considered the effect of a sagittal fracture on fracture stability in 1949, and this concept was eventually introduced into the Tronzo classification established in 1973, which clearly pointed out that the integrity of the posterior cortex (degree of greater trochanteric communities) is an important factor affecting sagittal stability, and intertrochanteric fractures are unstable. 11 Fractures of the lesser trochanter cause rupture of the medial cortex and loss of mechanical support, resulting in vara of the hip. Greater trochanter fractures further aggravate the sagittal instability, resulting in retrograde femoral head. Embden et al. 12 compared the reproducibility of the AO classification of femoral trochanteric fractures by Jensen classification, and then evaluated the consistency of the two classifications, the guidance for the selection of treatment methods, the reduction of fractures, and the location of internal fixation. Fifty fractures were observed by 10 observers. The inter‐observer agreement kappas of the AO classification and Jensen classification were 0.40 and 0.48, respectively, and the intra‐observer agreement kappas were 0.43 and 0.56, respectively. The consistency of fracture stability and endoplant selection before surgery was 0.39 and 0.65, and the consistency of endoplant selection, fracture reduction, and endoplant location after surgery was 0.17, 0.29 and 0.22, respectively. The reproducibility of the two classification methods was not satisfactory. The study suggests that the current definition of the stability of intertrochanteric fractures remains ambiguous, which might affect the choice of surgical modalities. There is still great debate on the classification of intertrochanteric fractures. The common types of intertrochanteric fractures are not reliable in terms of repeatability, which has a certain effect on the judgment of fracture stability, the selection of internal fixation, and the prognosis. As an orthopaedic surgeon, the fracture type is not something we can determine. However, we need to be familiar with the classification and trauma mechanism, understand the stability of the fracture, analyze the actual situation of the patient, and provide appropriate treatment. A thorough understanding of the classification of intertrochanteric fractures helps to predict fracture stability and avoid postoperative complications such as screw cutting and internal fixation rupture. 13 Meanwhile, a better classification of the intertrochanteric fracture remains to be discussed by orthopaedists.
A large number of studies have shown that the medial functional area (internal wall) of the lesser trochanter under pressure and the functional area of the lateral wall where the greater trochanter area is located play an extremely important role in the stability of intertrochanteric fractures after internal fixation. The medial wall, particularly the lesser trochanter region, is obstructed or overlapped by the two‐dimensional (2D) X‐ray pictures. Thus, the damage to the femoral distance cannot be completely evaluated. CT plain scan data displays the region and damage involved in the fracture line more comprehensively than X‐ray data; however, it lacks an intuitive and three‐dimensional (3D) explanation of femoral intertrochanteric fractures. In previous studies, there is no clear conclusion on the accuracy of stability analysis in the classification of intertrochanteric fractures, and there is also an absence of related studies on whether stability analysis in classification can be used to evaluate hip function after internal fixation. This research is based on 320 instances of femoral intertrochanteric fractures admitted to Chengdu University's Affiliated Hospital between January 2009 and December 2019. The goal is to propose a new classification of six sections of femoral intertrochanteric fractures, with subtypes based on 3D‐CT imaging. The six‐part classification of intertrochanteric fractures was established, and we investigated the feasibility and credibility of this classification. First, we compared and contrasted the AO and six‐part fracture classifications. We considered whether there was there a distinction in stability analysis. Second, stable fractures and unstable fractures were divided according to the six‐part classification standard, and the two groups of perioperative and follow‐up observation indicators were compared to see if there was a difference in the evaluation index of imaging stability. Third, we examined the six‐part classification's inter‐observer and internal reliability, as well as its accuracy and repeatability.
Materials and Methods
The general the study design is as follows: (i) the six‐part classification of intertrochanteric fractures is established; (ii) the stability analysis of this classification method is compared with that of the AO classification; (iii) the perioperative period indexes of the stable group and unstable group are compared; (iv) the effectiveness and accuracy of the classification method are verified; and (v) the damaged area between the two types of classification is compared. This study was approved by the Ethics Committee of The Affiliated Hospital of Chengdu University.(Ethical code 2019LL30).
Criteria for Inclusion and Exclusion
Criteria for Inclusion
Criteria for inclusion in the study were (i) that the patient was diagnosed as having a femoral intertrochanteric fracture and had undergone intramedullary nail surgery (to control variables to study hip function after internal fixation, all the surgical methods selected in this study involved intramedullary nailing); (ii) closed fractures; (iii) time from injury to operation <3 weeks; (iv) the patient could walk before their injury; and (v) follow‐up time was >1 year, with complete imaging information available, including X‐ray and CT data.
Criteria for Exclusion
Criteria for inclusion in the study were (i) pathological fractures; (ii) fractures combined with femoral neck fractures; (iii) fractures combined with subtrochanteric fractures; (iv) open femoral intertrochanteric fractures; (v) old femoral intertrochanteric fractures; (vi) patients with Alzheimer's disease; (vii) patients with scoliosis; (viii) patients with gluteal muscle contracture; (ix) patients with intellectual disability; and (x) combined damage of important organs and other systems.
General Information
A total of 320 cases were included after being screened using the following criteria. There were 107 male and 213 female patients. Patient ages ranged from 42 to 99 years old, with an average age of 79.32 ± 11.26 years. On the left side, there were 193 fractures, and on the right side, there were 127. Body mass index (BMI) ranged from 15 to 32, with an average of 22.98 ± 3.95. The prevalence of osteoporosis was 55.63% (178/320). There were 40 cases of hypertension, 21 of coronary heart disease, 46 of diabetes, 15 of liver insufficiency, 13 of renal function, and 33 of urinary tract infection.
The Choice of Surgical Method
Whether extramedullary and intramedullary fixation should be used for internal fixation of intertrochanteric fractures of the femur has always been a focus of debate. 14 At present, the mainstream view is that the lack of internal wall support for unstable intertrochanteric fractures such as AO type 31‐A2.3 and 31‐A3 is likely to lead to complications such as hip pronation and head incision, regardless of extramedullary fixation methods such as dynamic hip screws or the latest proximal femoral anatomic locking plate. If the external wall is not complete, the incidence of proximal femoral displacement can reach 40%, resulting in internal fixation failure. 15 Currently, it is believed that only a small number of severe osteoporosis, femoral head necrosis or severe hip osteoarthritis, and pathological fracture or internal fixation failure cases are suitable for hip replacement treatment. 16 Since intramedullary fixation is suitable for all types of femoral intertrochanteric fractures, more and more physicians now prefer intramedullary nails. 17 Although it is generally believed that intramedullary nailing in more advantageous in the treatment of unstable intertrochanteric fractures, complications of intramedullary nailing are not uncommon, especially in patients with unstable intertrochanteric fractures, such as head screw or spiral blade displacement, hip varus, femoral neck shortening, and internal fixation fractures.
Six‐Part Classification Method and Definition of Unstable Fractures
Following long‐term clinical practice and imaging studies, preoperative CT‐3D reconstruction technology is used to divide the 3D anatomical area where the femoral intertrochanteric fracture is located, according to the fracture line implicated, after long‐term clinical experience and imaging investigations. The intertrochanteric fracture is categorized, and a six‐part intertrochanteric classification is proposed.
The fracture involvement of the anatomical functional area of the femoral trochanter is classified as follows: the proximal part of the fracture line (femoral head and neck), the distal part of the fracture line, the greater trochanter, the lesser trochanter, the medial wall of the femur, and the lateral wall of the femur. According to the six‐part classification, the fracture line simply involves the greater trochanter or lesser trochanter, and the two, three, and four A types without serious damage to the lateral wall and medial wall functional area are stable fractures, according to the principle of anatomical functional area. Unstable fractures include the four‐part type B/C, five‐part, and six‐part fractures involving the greater and lesser trochanters with significant damage to the functional region of the lateral wall or (and) medial wall (Table 1). The typical imaging data for each subtype are shown in Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12.
TABLE 1.
Six‐part classification diagnostic criteria
| Six‐part classification | Fracture description |
|---|---|
| Two‐part fracture (Figures 1 and 2) | It is a two‐part fracture of the proximal and distal parts of the fracture when only a single fracture line involves the intertrochanteric line. |
| Three‐part fracture (Figures 3, 4, 5) |
(1) Subtype A: The greater trochanter is broken based on a two‐part fracture; however, the lateral wall is not damaged. (2) Subtype B: The lesser trochanter is broken based on a two‐part fracture; however, the medial wall is not damaged. |
| Four‐part fracture (Figures 6 and 7) |
(1) Subtype A: greater trochanter fracture + lesser trochanter fracture (2) Subtype B: greater trochanter fracture + lateral wall fracture (3) Subtype C: lesser trochanter fracture + medial wall fracture |
| Five‐part fracture (Figures 8, 9, 10) |
(1) Subtype A: greater trochanter fracture and lesser trochanter fracture, as well as lateral wall fracture (2) Subtype B: greater trochanter fracture and lesser trochanter fracture as well as medial wall fracture (3) Subtype C: lesser trochanter fracture and medial wall fracture as well as lateral wall fracture (4) Subtype D: greater trochanter fracture + lateral wall fracture, as well as medial wall fracture |
| Six‐part fractures (Figures 11 and 12) | The greater and lesser trochanters are severely damaged, as well as lateral and medial wall fractures |
FIGURE 1.
Schematic diagram of two‐part fracture. It is a two‐part fracture of the proximal and distal parts of the fracture when only a single fracture line involves the intertrochanteric line.
FIGURE 2.
X‐ray and three‐dimensional reconstruction of two‐part fracture.
FIGURE 3.
Schematic diagram of three‐part type A fracture (greater trochanter fracture). The greater trochanter is broken based on a two‐part fracture; however, the lateral wall is not damaged.
FIGURE 4.
Schematic diagram of a three‐part type B fracture (lesser trochanter fracture). The lesser trochanter is broken based on a two‐part fracture; however, the medial wall is not damaged.
FIGURE 5.
X‐ray and three‐dimensional reconstruction of a three‐part fracture.
FIGURE 6.
Schematic diagram of a four‐part fracture. Subtype A: greater trochanter fracture and lesser trochanter fracture. Subtype B: greater trochanter fracture and lateral wall fracture. Subtype C: lesser trochanter fracture and medial wall fracture.
FIGURE 7.
X‐ray and three‐dimensional reconstruction of a four‐part fracture.
FIGURE 8.
Schematic diagram of a five‐part type A fracture (lateral wall fracture), based on a subtype A of a four‐part as well as a lateral wall fracture.
FIGURE 9.
Schematic diagram of a five‐part type B fracture (posterior medial wall fracture), based on a subtype A of four‐part, as well as medial wall fracture.
FIGURE 10.
X‐ray and three‐dimensional reconstruction of a five‐part fracture.
FIGURE 11.
Schematic diagram of a six‐part fracture. Based on a four‐part fracture, the greater and lesser trochanters are severely damaged, as well as lateral and medial wall fractures.
FIGURE 12.
X‐ray and three‐dimensional reconstruction of a six‐part fracture.
Research Methods and Observation Indicators
First, the 320 patients with femoral intertrochanteric fractures who satisfied the inclusion and exclusion criteria and underwent closed reduction and intramedullary nailing were rebuilt using the patients’ preoperative CT data. The AO classification and six‐part classification were also provided based on the 3D‐CT imaging data. According to the stability definition standard, 320 patients is categorized to see if there is a difference in the fracture stability rate between the AO classification and the six‐part classification. Second, the 320 patients were categorized according to the different stability using the AO classification, as well as the different stability of the six‐part classification, and the statistical differences in the stability analysis of the two classification techniques were compared. Third, according to the six‐part classification criteria, 320 patients were divided into stable (two, three part, and four part A type) and unstable fracture (four part B/C type, five part, and six part) groups, and the perioperative and follow‐up observation indicators of the two groups were counted and analyzed to see if there were statistical differences. Fourth, simultaneously, statistical indicators of fracture stability in follow‐up imaging of the two groups of patients were tallied, and imaging stability indicators of the two groups of patients after intramedullary nailing were examined. Fifth, we examined the six‐part classification's inter‐observer and internal reliability. The above six‐part classification method was performed and validated by two top trauma orthopaedic surgeons who were trained in hip CT scan imaging. The consistency, stability, and dependability of data information collection are referred to as reliability. For evaluation, two indicators of inter‐observer dependability and internal reliability were used. The inter‐observer reliability is based on two trained observers transcribing the CT scan data of the same patient concurrently and then independently. Within 24 h, the same observers retested the intra‐observer reliability. The intra‐group correlation coefficient (ICC) was used to assess inter‐observer and internal dependability. 18 An ICC value > 0.75 indicates high dependability, 0.4–0.75 indicates medium reliability, and 0.4 indicates low reliability. We examined the typing method's accuracy and repeatability.
The Following Perioperative and Follow‐Up Observation Indicators
The operation time, perioperative blood loss, and Harris hip score (HHS) of the patients were followed up on for 3, 6, and 12 months after surgery. The HHS score takes into account pain, mobility, function, and deformity. The total number of points is 100. The better the recuperation function, the higher the score. The Harris hip function score standard (out of 100 points) was used for evaluation, with excellent 91–100 points, acceptable 80–90 points, fair 70–79 points, and poor <70 points. The excellent and good rate is the total of the proportions of excellent and good. At the most recent follow‐up, AP & LAT position X‐rays of the proximal femur were obtained, and the modified Baumgaertner standard 19 was used to assess fracture reduction quality. We kept track of the fracture healing time: if the patient has no pressing or percussion discomfort, these are clinical indications of fracture healing. The X‐ray film employed the callus across the fracture end to reach 50% of the fracture end as an imaging sign of fracture healing while also meeting the clinical indicators and criteria. The time it took for imaging indications to appear was reported as fracture healing time. 20 Whole weight‐bearing times were recorded. At the most recent follow‐up, the functional independence measurement was employed to reflect the fundamental activities of daily life. 21 , 22 The table is divided into two sections: movement and cognition. The movement score (function independent measurement [FIM] sports subscale) is made up of four items: 1. Self‐care ability; 2. Sphincter control; 3. Moving and walking; 4. Communication and social cognition. The cognitive section (FIM cognitive subscale) comprises four items: communication and social cognition are made up of six major questions, with 18 sub‐items. The maximum score is 126 points: 126 points corresponds to total independence; 108–125 points corresponds to fundamental independence; 90–107 points corresponds to conditional independence or very light reliance; 72–89 points corresponds to mild dependence; and 54–71 points corresponds to moderate dependence; 36 to 53 points corresponds to severe dependency; and 18 points corresponds to total dependence.
For the timed up and go test (TUG), the patient is instructed to get up from a regular‐height chair, move 3 m at a typical walking speed, turn around, return, and sit down again, and record the time spent in the entire procedure. 23 Three measurements are taken and the results are averaged. The Parker–Palmer score (PPMS) covers three daily living components (1. Indoor, 2. Outdoor, 3. Daily life self‐care walking), indoor and outdoor, each with a maximum of three points and a total score of nine. The better the functional recovery, the higher the score. 24
Follow‐Up Imaging and Indications of Stability
The imaging data from the patient's initial postoperative and final follow‐up following fracture healing were measured and documented. 25 To measure the loss of reduction following the intramedullary nail, we calculated the height of the femoral head relative to the intramedullary nail. We drew two parallel lines perpendicular to the main nail, one intersecting the upper border of the main nail and the other intersecting the top of the femoral head. The distance between these two lines is defined as the femoral head height (FHH). The FHH change is the difference in the height of the femoral head between the first time after the procedure and the last time after the fracture has healed.
The medial cephalic nail length (Lmcn) change in distance between the main nail's medial head nail refers to the distance between the tip of the head nail and the medial edge of the proximal end of the main nail. The sliding distance of the head screw is represented by the change in Lmcn during the initial postoperative time and two periods following fracture healing. The tip–apex distance (TAD) change in apex distance 26 is measured using front and lateral X‐rays from the tip of the head nail to the apex of the femoral head (parallel to the intersection of the central line of the femoral neck and the subchondral bone). The sliding distance of the head nail relative to the tip of the femoral head after the procedure and after the fracture has healed is the degree of change in TAD (Figure 13).
FIGURE 13.
(1) Femoral head height, (2) femoral neck shaft angle, (3) Lmcn (medial cephalic nail length), and (4) tip–apex distance.
Statistical Methods
Statistical software (SPSS, version 22.0, Chicago, IL, USA) was used for sorting and analysis. The measurement data that follow the normal distribution and the variance are expressed as X ± S. The comparison uses one‐way analysis of variance, and the post‐comparison uses Tukey's multiple comparison; it does not follow the normal distribution or the variance and uses the Wilcoxon rank of two independent sample comparisons. Using repeated measures analysis of variance, repeated measures data were compared with Harris ratings at different time points of 3, 6, and 12 months. The Harris scores of the stable and unstable groups were evaluated using repeated measures analysis of variance at 3, 6, and 12 months to assess the effects of fracture stability over time on the Harris score following intramedullary nailing for intertrochanteric fractures.
Counting data is expressed as ratios and compared using chi‐square tests. ICC was used to evaluate the intra‐observer and inter‐observer reliability of the six components. The χ2‐test was used to compare the fracture stability rate between the two classification techniques, and the McNemer test and the Kappa test were used to examine the difference and consistency of the fracture stability rate analysis between the two classification methods. A kappa score 0.01–0.40 indicates low consistency, 0.41–0.60 is moderate consistency, 0.61–0.80 is strong consistency, and 0.81–1.0 is almost the same. The test level α is both 0.05.
Results
Comparison of Fracture Stability
Based on preoperative CT and 3D reconstruction data, 320 patients were divided into six‐part and AO classifications. Using the six‐part classification as the norm, there were 31 cases in two parts, 79 cases in three parts, 71 cases in four parts, 64 cases in five parts, and 75 cases in six parts. There were 127 stable fractures (two‐part, three‐part, and four‐part A) and 193 unstable fractures (four‐part B/C, five part, and six part). The fracture stability rate (127/320) was 39.69%. Using the AO classification as the standard, A1.1 had 12 cases, A1.2 had 28 cases, A1.3 had 34 cases, A2.1 had 62 cases, A2.2 had 27 cases, A2.3 had 28 cases, A3.1 had 24 cases, A3.2 had 42 cases, and A3.3 had 63 cases. There were 136 instances of stable fractures (A1.1/1.2/1.3; A2.1) and 184 cases of unstable fractures (A2.2/2.3; A3.1/3.2/3.3). The fracture stability rate (136/320) was 42.50%. The χ 2‐test (χ 2 = 0.523, p = 0.470 > 0.05) revealed no significant difference in the fracture stability rate between the two classification techniques (Table 2).
TABLE 2.
AO and six‐part classification stability analysis
| Classification methods | Stable fractures | Unstable fractures |
|---|---|---|
| Six‐part classification | A total of 127 cases (two parts, 31 cases; three parts, 79 cases; four parts A type, 17 cases) | A total of 193 cases (four parts B/C type, 54 cases; five parts, 64 cases; six parts, 75 cases) |
| AO classification | A total of 136 cases (A1.1, 12 cases; A1.2, 28 cases; A1.3, 34 cases; A2.1, 62 cases) | A total of 184 cases (A2.2, 27 cases; A2.3, 28 cases; A3.1, 24 cases; A3.2, 42 cases; A3.3, 63 cases) |
| χ 2 value | 0.523 | |
| p‐value | 0.470 | |
The difference and consistency test was completed using the AO and the six‐part classification (p = 0.306 > 0.05 for the McNemer test of difference). In the examination of fracture stability, the AO and the six‐part classification did not vary statistically. In regard to kappa test consistency, the kappa value = 0.607, p < 0.001. The two classification techniques were consistent in the diagnosis of fracture stability; kappa value > 0.6, and the consistency was acceptable (Table 3).
TABLE 3.
Consistency analysis of AO and six‐part classification stability
| Classification methods | Six‐part classification of stable fractures | Six‐part classification of unstable fractures | Total |
|---|---|---|---|
| AO classification stable fracture | 101 | 35 | 136 |
| AO classification unstable fracture | 26 | 158 | 184 |
| Total | 127 | 193 | 320 |
| Kappa value | 0.607 | ||
| p‐value | <0.001 | ||
Comparison of Perioperative Indexes
According to the six‐part classification, there were 127 instances in the stable fracture group and 193 cases in the unstable fracture group. Baseline indicators were compared between the two groups: (i) gender (χ 2 = 0.733, p = 0.392), (ii) age (t = 1.019, p = 0.309), (iii) BMI (t = −1.780, p = 0.076), and (iv) osteoporosis (χ 2 = 1.004, p = 0.316). There was no statistically significant difference in the above four indicators.
There was no statistically significant difference in five indicators during the perioperative period and follow‐up observation index: (i) operation time (t = −1.081, p = 0.280); (ii) fracture reduction quality (χ 2 = 5.547, p = 0.062); (iii) FIM (t = 1.787, p = 0.075); (iv) TUG (t = −1.311, p = 0.191); and (v) PPMS (t = 1.457, p = 0.146). At the same time, perioperative blood loss in the stable group was 119.01 ± 60.25 mL and in the unstable group was (149.84 ± 63.04) mL (t = −4.355, p < 0.001). The excellent and good rate of the Harris score was 93.70% (119/127) in the stable group. That of the unstable group was 86.01% (166/193) (χ 2 = 4.650, p = 0.043). The fracture healing time of the stable group was 94.23 ± 9.44 days and the unstable group was 100.66 ± 12.09 days (t = −5.059, P < 0.001). The whole weight‐bearing period was 85.01 ± 11.40 days in the stable group and 88.70 ± 9.33 days in the unstable group (t = −3.173, p = 0.002). The variations in the four indices listed above were statistically significant.
Compared with stability‐related indicators in imaging, (i) FHH change in the stable group was −3.73 ± 2.24 mm and −4.29 ± 2.53 mm in the unstable group (t = 2.002, p = 0.046); (ii) femoral neck shaft angle (FNSA) change in the stable group was −3.25 ± 1.72° and −3.80 ± 1.60° (t = 3.004, p = 0.003) in the unstable group; (iii) Lmcn (mm) in the stable group was 2.99 ± 1.36 mm and 3.35 ± 1.54 mm (t = −2.141, p = 0.033) in the unstable group; and (iv) TAD change in the stable group was −2.01 ± 1.01 mm and −2.39 ± 1.05 mm (t = 3.189, p = 0.002) in the unstable group. The differences in the above four indicators were statistically significant (Table 4).
TABLE 4.
Comparison of perioperative indexes between the stable and unstable group
| Index | Six‐part classification | |||
|---|---|---|---|---|
| Fracture stable group (two‐parts, three‐parts, four‐parts A type) | Fracture unstable group (four‐parts B/C type, Five‐parts, Six‐parts) | Statistics (t/χ 2value) | p‐value | |
| Baseline indicators | ||||
| Number of cases | 127 | 193 | ‐ | ‐ |
| (1) Gender (Male/Female) | 46/81 | 61/132 | 0.733 | 0.392 |
| (2) Age (years) | 80.11 ± 10.25 | 78.80 ± 11.88 | 1.019 | 0.309 |
| (3) BMI (kg/m2) | 22.49 ± 4.11 | 23.29 ± 3.84 | −1.780 | 0.076 |
| (4) Osteoporosis rate (%) | 59.06% (75/127) | 53.37% (103/193) | 1.004 | 0.316 |
| Perioperative period and follow‐up observation indicators | ||||
| (1) Operation time (min) | 99.43 ± 28.31 | 103.59 ± 36.75 | −1.081 | 0.280 |
| (2) Perioperative bleeding volume (mL) | 119.01 ± 60.25 | 149.84 ± 63.04 | −4.355 | <0.001 |
| (3) Harris score excellent and good rate (%) | 93.70% (119/127) | 86.01% (166/193) | 4.650 | 0.043 |
| (4) Fracture healing time (days) | 94.23 ± 9.44 | 100.66 ± 12.09 | −5.059 | <0.001 |
| (5) Time to complete bear the weight (days) | 85.01 ± 11.40 | 88.70 ± 9.33 | −3.173 | 0.002 |
| (6) Fracture reduction quality (excellent/good/acceptable) | 90/32/5 | 112/72/9 | 5.547 | 0.062 |
| (7) The last FIM (points) | 99.58 ± 15.74 | 96.22 ± 16.92 | 1.787 | 0.075 |
| (8) The last TUG (points) | 17.64 ± 5.21 | 18.52 ± 6.33 | −1.311 | 0.191 |
| (9) The last PPMS (points) | 6.98 ± 1.59 | 6.72 ± 1.52 | 1.457 | 0.146 |
| Imaging and stability related indicators | ||||
| (1) FHH change amount (mm) | −3.73 ± 2.24 | −4.29 ± 2.53 | 2.002 | 0.046 |
| (2) Change in FNSA (°) | −3.25 ± 1.72 | −3.80 ± 1.60 | 3.004 | 0.003 |
| (3) Lmcn (mm) | 2.99 ± 1.36 | 3.35 ± 1.54 | −2.141 | 0.033 |
| (4) TAD change amount (mm) | −2.01 ± 1.01 | −2.39 ± 1.05 | 3.189 | 0.002 |
Note: Bold values means there is a statistical difference.
Abbreviations: FHH, femoral head height; FIM, function independent measurement; FNSA, femoral neck shaft angle; Lmcn, medial cephalic nail length; PPMS, Parker‐Palmer score; TAD, tip‐apex distance; TUG, time up and go test.
Repeated Measures Analysis of Variance in the Harris Score
The examination of studentized residuals and the Shapiro–Wilk test show that each batch of data follows the normal distribution (p > 0.05). There was no variability in the data of any group based on whether the studentized residuals exceeded ±3 times the standard deviation. Following the results of Mauchly's spherical distribution test, the interaction term fracture stability group * time χ 2 = 4.044, p = 0.132 > 0.05, fulfills the spherical distribution hypothesis. The interaction between fracture stability grouping and time was not statistically significant in the tests of within‐subjects effects table (F (2,252) = 1.606, p = 0.203 > 0.05). As a result, the primary effects of fracture stability and temporal variables must be examined independently.
The Major Effects of Fracture Stability Variables
There were just two degrees of fracture stability, and there was no need to verify whether it met the spherical hypothesis. The main effect of fracture stability grouping on the Harris score was statistically significant (F (1,126) = 32.604, p < 0.001). The fracture stability group's main effect analysis indicates that the Harris score was significantly different independent of the time point of the test. The stable fracture group was compared to the unstable fracture group. According to the pairwise comparisons table, the stable fracture group's Harris score was 3.016 points greater than the unstable fracture group's (95% confidence interval: 1.97–4.061). The difference was statistically significant (p < 0.001).
The Major Influence of the Time Element
Because the primary effect of time is a comparison of three levels, for the sphere test, χ 2 = 7.279, p = 0.026 < 0.05, which does not satisfy the sphere distribution hypothesis. Calibration was accomplished using the Greenhouse–Geisser technique. The influence of the time factor on the Harris score was statistically significant in the tests of within‐subjects effects table (F (1.893,238.508) = 202.771, p < 0.001), and the difference was statistically significant. According to pairwise comparison, the Harris score of 7.006 points (95%t confidence interval: 5.660–8.351) after 12 months following surgery was greater than that at 6 months after surgery data. The difference was statistically significant, with a p‐value of <0.001. The Harris score at 6 months after surgery was 5.737 points higher than the Harris score at 3 months after surgery (95% confidence interval: 4.1367.338), and the difference was statistically significant (p < 0.001) (Table 5). Figure 14 depicts the variations in Harris scores in the two groups at three different time points (Table 5).
TABLE 5.
Multi‐time repeated measures analysis of variance (Harris score)
| Six‐part classification | Time point | Fracture stable group | Fracture unstable group | Fracture unstable group Time factor is the main effect F‐value | p‐value |
|---|---|---|---|---|---|
| Harris score | 3 months after surgery | 76.49 ± 7.93 | 72.30 ± 9.38 | 202.771 | <0.001 |
| 6 months after surgery | 81.60 ± 6.28 | 78.66 ± 6.05 | |||
| 12 months after surgery | 88.09 ± 6.76 | 86.18 ± 6.43 | |||
| The main effect of fracture stability factor F‐value | 32.604 | ||||
| p‐value | <0.001 | ||||
FIGURE 14.
The trend of the estimated marginal means of Harris scores. Fracture stability had a substantial influence on Harris ratings at 3, 6, and 12 months following surgery, according to repeated measures analysis of variance. The effect of time on Harris score is similarly significant.
Evaluation of Consistency and Dependability
The same observers performed a six‐part classification on the 3D reconstruction data of the same group of 50 cases of femoral intertrochanteric fractures before and after repeated tests, and the intra‐group correlation coefficient (ICC) value was 0.941 > 0.75, indicating good intra‐observer reliability. Inter‐observer reliability was assessed by having two observers divide the 3D reconstruction data of the same group of 50 cases of femoral intertrochanteric fractures into six parts; the ICC value was 0.921 > 0.75, and the inter‐observer reliability was good.
Comparison of the Damaged Area between the Two Types of Classification
The six‐part classification and AO classification showed statistical differences in the description of the injury area of intertrochanteric fracture (χ 2 = 11.612, p = 0.041 < 0.05), especially for simple greater trochanteric fractures (six‐part classification 3.75%, 12/320; AO classification 7.19%, 23/320) and external wall damage (six‐part classification 16.88%, 54/320; AO classification 12.5%, 40/320), and also for simple lesser trochanteric fracture (six‐part classification 5.31%, 17/320; AO classification 7.50%, 24/320) and internal wall damage (six‐part classification 33.44%, 107/320; AO classification 29.38%, 94/320). There were statistical differences between the six‐part and AO classification in the description of the injury area of intertrochanteric fracture. The six‐part classification had a higher recognition rate of the medial wall loss affecting the stability than AO classification (33.44% > 29.38%), while the recognition rate of lateral wall loss affecting stability of the six‐part classification was higher than that of the AO classification (16.88% > 12.5%). Therefore, the six‐part classification was better for distinguishing between internal and external wall injuries and simple fractures of the greater and lesser trochanter (Table 6).
TABLE 6.
Comparison of the injury area of each part of 320 intertrochanteric fractures in AO and six parts
| Classification methods | Simple greater trochanteric fracture | External wall instability | Simple lesser trochanteric fracture | Internal wall instability | Simple greater and lesser trochanteric fractures | External and internal wall instability | Total |
|---|---|---|---|---|---|---|---|
| Six‐part classification | 12 | 54 | 17 | 107 | 18 | 112 | 320 |
| AO classification | 23 | 40 | 24 | 94 | 32 | 107 | 320 |
| χ 2 value | 11.612 | ||||||
| p‐value | 0.041 | ||||||
Discussion
The main findings of this study are as follows. First, there was no statistically significant difference between the AO and six‐part classification techniques in the examination of fracture stability. Second, perioperative blood loss, the Harris score excellent and good rate, fracture healing time, and the entire weight‐bearing duration were statistically significant. The difference in FHH, the change in FNSA, the change in Lmcn, and the change in TAD were statistically significant when compared to the relevant markers of imaging stability. Third, according to repeated measures analysis of variance, fracture stability had a substantial influence on Harris ratings at 3, 6, and 12 months following surgery. The effect of time on the Harris score was similarly significant. Fourth, inter‐observer and intra‐observer reliability were both good. Finally, compared with AO classification, the six‐part classification is better for distinguishing between internal and external wall injuries and simple fractures of the greater and lesser trochanter.
The Benefits of the Six‐Part Classification in Evaluating Fracture Stability
Mechanism for the Establishment of Six‐Part Classification
Previous research has revealed that the stability of femoral intertrochanteric fractures is affected by five factors: the type of fracture, osteoporosis, fixation method selection, fracture reduction, and internal fixation location (TAD apex distance). 27 , 28 This research attempted to establish a six‐part classification of femoral intertrochanteric fractures. For the stability study of femoral intertrochanteric fractures, this classification technique has a broader significance. It also has some predictive value for assessing and predicting hip joint function following intramedullary nailing.
Comparison of Stable Fracture Rate and Injury Area between AO and Six‐Part Classification
AO/OTA classification is the currently recognized defining technique for analyzing intertrochanteric fracture stability. Types A1.1/1.2/1.3 and A2.1 are fracture stable. This sort of fracture might be associated with decreased trochanter bone, but there is no evident damage to the medial wall's stability, and the coronal surface is stable. Fracture instability types A2.2/2.3 and A3.1/3.2/3.3 include larger trochanter, intertrochanteric comminuted fracture, medial and lateral wall fractures, inverted intersub fractures, intertrochanteric transverse fractures, and fractures beneath the trochanter. The destruction of the load‐bearing line produced by fracture comminution, significant damage to the medial wall, loss of medial support, and proclivity to collapse and varus deformity all contribute to the instability of this kind of fracture. 28 At the same time, the fracture stability of the AO classification relies on whether the medial wall is stable, and the description of the lateral wall has certain flaws. There is a paucity of relevant research on the AO classification for the evaluation of the prognosis of the hip joint, particularly the study of fracture stability through the AO classification for the postoperative evaluation of intertrochanteric fracture intramedullary nailing. The advantage of the proposed six‐part classification method is that its stability analysis is based on the recovery of hip function after intramedullary nailing. At the same time, based on the 3D‐CT data, the types were classified according to the different injury conditions of the intertrochanteric functional area. The classification of functional areas includes six parts: the proximal fracture line (head and neck of the femur), the distal fracture line, the greater trochanter, the lesser trochanter, the medial wall of the femur, and the lateral wall of the femur. The damage of the inner wall and lateral wall functional area was used as the basis for classification. This classification has more comprehensive significance for the stability analysis of femoral intertrochanteric fractures and also has certain guiding significance for the evaluation and prediction of hip function after intramedullary nail surgery.
AO/OTA, Evans, Evans‐Jensen, Boyd‐Griffin, Ramandier, Ender, Decoulx‐Lavarde, Kyle, Ottolenghi, Gotfried, Kijima, Tronzo, Tan, and more kinds of femoral intertrochanteric fractures exist. 29 Cavaignac et al. investigated the consistency of AO classification and Evans–Jensen classification using X‐ray, CT plain scan, and CT‐3D imaging methods and discovered that none of the imaging examinations mentioned above can improve the reliability of the two types of diagnosis. 30 The six‐part classification is based on 3D‐CT data using functional regions to identify simple trochanteric fractures and to learn more about medial and lateral wall damage that affects stability from the 3D imaging. The six‐part classification is divided into sections based on the distinct functional regions implicated in the fracture line, as well as the harm to the medial and lateral walls. The six‐part classification is divided into sections based on the various functional areas implicated in the fracture line, with damage to the medial and lateral wall functional regions serving as an essential foundation for classification.
Comparison of Clinical and Imaging Results between Stable and Unstable Groups
This study investigated whether there was a difference in postoperative hip function between the stable fracture group and the unstable fracture group and analyzed the stability of the postoperative fracture from imaging features, all under the same premise of osteoporosis, the same choice of internal fixation methods, and the same quality of fracture reduction. This study found that the six‐part classification of stable (two, three, four‐part A type, five part, and six part) and unstable (four‐part B/C type, five part, and six part) are functionally independent in operation time, fracture reduction quality, and last follow‐up sex measurement (FIM), walking timing test (TUG), and PPMS compared to no significant difference. However, the stable fracture type's perioperative blood loss, Harris score excellent and good rate, fracture healing duration, and full weight‐bearing time are better than those of the unstable fracture type. FHH, FNSA, Lmcn, and apex distance (TAD) were better for the stable fracture type than the insecure type. The Harris score after 3, 6, and 12 months following the procedure revealed that the stable fracture type was superior to the unstable type in repeated measures analysis of variance. As a result, the stable types were two‐part fractures, three‐part fracture, and four‐part A type fractures. The unstable types are four‐part B/C type fractures, five‐part fractures, and six‐part fractures.
Advantages of six‐part classification: Analysis of fracture stability based on hip function after intramedullary nailing. At the same time, it is categorized according to the distinct injuries of the intertrochanteric functional region based on 3D‐CT data. The proximal section of the fracture line (femoral head and neck), the distal part of the fracture line, the greater trochanter, the lesser trochanter, and the medial and lateral wall of the femur are all classified as functional regions. The integrity of the lesser trochanter and the femoral talus is critical for stability. 28 The greater trochanter is a cancellous bone structure that serves primarily as an attachment site for the hip abductor muscle group and is not engaged in weight‐bearing. The greater trochanter fracture mostly affects the abductor muscle's attachment site but has little effect on its stability. When the head and neck bone block is internally fastened and implanted, the lateral cortex of the proximal femur must be punctured. Fractures of the anterior and lateral walls between the trochanters will result in loss of support for the head and neck bone mass. This anatomical functional region is critical for the proximal femur's stability. When intramedullary fixation is chosen after the present medial cortex has been damaged, the tension will be centered on the metal main nail and the lateral cortex. When extramedullary fixation is used, the external transfer stress of the head and neck bone extends to the lateral wall. If the anatomical functional region of the lateral wall is significantly injured at this point, the head and neck bone will lose cortical support from the femoral shaft and the internal fixation will fail. Increase significantly, and its stability is substantially reduced. 31
Results of the Conformance Test in Six‐Part Classification
AO classification and Evans–Jensen classification are now the most widely utilized categories in clinical practice. These two conventional categories have flaws: In clinical diagnosis and therapy, fracture classification based on traditional X‐ray films frequently relies on 2D imaging. Typing accuracy has been severely affected by overlapping, artifacts, exposure, and image technology, making its dependability debatable. Schipper's study discovered that the primary AO classification of femoral intertrochanteric fractures had a Kappa value of 0.78, whereas the subtype had a value of 0.48. The findings revealed that the subtype of AO classification was untrustworthy. 32 According to Fung's research, the reliability of the AO classification is somewhat greater than that of the Evans–Jensen classification. To achieve a more accurate fracture judgment, it is advised to utilize two classifications to classify fractures. 33 Pervez and Van evaluated the dependability of the AO classification with the Evans–Jensen classification based on X‐ray films and discovered that both were unreliable. 34 Due to the limited use of intraoperative medial surgical approaches and the interference of the adductor muscle group in the lesser trochanter area, it is not possible to view the fracture directly in femoral intertrochanteric fractures, making it difficult for intraoperative findings to become the “gold standard.” The reliability and coincidence rate of the fracture classification system might be used to assess the fracture. De Boeck used AO classification based on X‐ray film and revealed that the diagnosis was unreliable. 35 The classification of femoral intertrochanteric fractures based on X‐ray and CT scans is inadequate in terms of real fracture morphological details and diagnostic accuracy, particularly for the medial and posterior fractures. The explanation is overly simplistic, resulting in inter‐observer and intra‐observer errors. Consistency is lacking. In this study, the ICC was used in this study to describe the inter‐observer and intra‐observer reliability of the six methods of classification. The ICC technique might assess both quantitative and categorical data dependability. It might be used to assess and quantify inter‐observer and retest reliability. The ICC of the six‐part classification is 0.941, and the ICC is 0.921, both of which are significantly higher than 0.75. The intra‐observer and inter‐observer reliability are both high, as are the operability and repeatability. The six‐part classification is more intuitive and straightforward than the old classification, with clearer classification norms, strong distinction across subtypes, ease of memorization, and ease of promotion in clinical application.
The Deficiencies and Prospect of this Research
Based on 3D‐CT data, the six‐part classification analyzes the stability of the fracture and is helpful to evaluate the prognosis of intertrochanteric fractures after internal fixation. This classification is more specific for the greater and lesser trochanter injuries and the stability of the greater and lesser trochanter regions, which is conducive to the analysis of fracture stability.
This study is a retrospective analysis, and it is not possible to evaluate whether surgery can be guided according to the classification to achieve the effect of improving the prognosis of patients. Further research should be conducted in the future. This study did not compare the advantages of this classification with other classification methods. The purpose of this study was to verify the significance of this classification method for stability research through the difference in prognosis between the stable group and the unstable group. In further studies, we hope to verify the differences between this classification and other classifications, especially AO, Evans–Jensen, and Wada classification systems. The investigations of hip joint function and imaging of fracture stability markers in the six‐part stable and unstable groups after intramedullary nailing are retrospective. This is a single‐center study with a limited sample size, and experimental results might contain errors. Long‐term research can gather cases from many centers and enhance the sample size to prevent experimental mistakes. The follow‐up time for fracture stability and hip joint function following intramedullary nailing was rather short in this study.
Conclusion
The six‐part classification based on 3D‐CT images has high accuracy in the stability analysis of intertrochanteric fractures. Clinicians will find this classification simpler and more consistent than the AO classification.
Conflict of Interest Statement
All authors declare that they have no conflicts of interest.
Ethics Statement
This study was approved by the Ethics Committee of The Affiliated Hospital of Chengdu University (Ethical code 2019LL30). All patients agreed to participate in the study. Written consent was obtained from all participants prior to this study.
Author Contributions
ZhengHao Wang was responsible for the experimental design and article writing. KaiNan Li and Chao Peng were responsible for experimental design and data collection.
Funding Information
This study was funded by Key Projects at the Affiliated Hospital of Chengdu University (Y2021012) and Sichuan Medical Association Project (Q21001).
Consent for Publication
Not applicable.
Acknowledgments
Not applicable. All experiments were performed in accordance with relevant guidelines and regulations. All methods were carried out in accordance with relevant guidelines and regulations. All experimental protocols were approved by the licensing committee. This study informed consent was obtained from all subjects and their legal guardians.
Contributor Information
KaiNan Li, Email: wzh435302004@126.com.
Chao Peng, Email: cy33427@163.com.
Data Availability Statement
All data generated or analyzed during this study are included in this published article.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
All data generated or analyzed during this study are included in this published article.