Analysis of risk factors for re-displacement of pediatric tibia fractures: A retrospective study of 196 cases

Abstract

Objective:

The aims of this study were (1) to analyze the factors that may cause loss of reduction (LOR) in pediatric tibia diaphysis and distal third fractures treated with closed reduction and casting (CRC) and (2) to determine the effectiveness of cast index (CI), gap index (GI), and three-point index (TPI) in prediction of LOR.

Methods:

The patients aged 0-16 years who were admitted to the emergency department between January 2014 and January 2018, with tibia diaphysis or distal third fractures and treated with CRC were included the study. A total of 196 pediatric patients (41 females, 155 males) were retrospectively evaluated. The radiographs on admission were analyzed in terms of fracture type, location of the fracture, presence/location of the fibula fracture as well as initial angulation in both planes, translation, and the time of definitive cast. On radiographs taken after closed reduction and final casting, angulation in the coronal and sagittal planes, amount of translation (%), CI, GI, and TPI were measured. Logistic regression analysis was used to evaluate the risk factors of re-displacement.

Results:

Of 196 patients, 46 developed re-displacement (23%). Age (P : 0.029), initial translation (P : 0.006), post-reduction translation (P : 0.001), and post-reduction AP angulation (P : 0.002) were found statistically significant. Mean CI and GI were higher in re-displacement group (P : 0.033, 0.036, respectively). According to multivariate logistic regression analysis post-reduction AP angulation, post-reduction translation, and cast index were found independent risk factors.

Conclusion:

One should carefully evaluate patients who underwent CRC due to tibia fracture with CI > 1.02, post-reduction AP angulation > 3.4°, and post-reduction translation > 24.3° in terms of occurrence of re-displacement.

Level of Evidence:

Level IV, Therapeutic Study

Highlights

• CRC is still considered a safe treatment method for pediatric tibial fractures.

• At the first application, the older the patient and the greater the initial translation, the more likely the fracture replace in the plaster.

• The risk of re-displacement increases as the post-reduction anteroposterior angulation and post-reduction translation increase.

• Patients with CI of > 1.02, post-reduction AP angulation of > 3.4°, and post-reduction translation of > 24.3% should be carefully evaluated for LOR.

Introduction

Tibia fractures are among the most common fractures in childhood that are seen approximately 40% in the diaphyseal and 50% in the distal third region.¹,² Treatment of diaphyseal tibia fractures in children varies according to the patient’s age, the pattern of the fracture, and the soft tissue condition.³ These fractures can often be reduced by closed means with the help of intact periosteal hinge, and satisfactory results can be obtained with cast treatment.⁴ The essential parameters of adequate fracture fixation with the cast are suitable molding and thin, uniform padding. The proper molding of the cast according to the direction which the fracture tends to displace is vital to prevent displacement, but Loss of Reduction (LOR) can be observed in the cast even after careful molding.⁴ Various indices have been developed to examine the quality of casting and molding in pediatric forearm fractures, and among them, Cast Index (CI), ⁵ Gap Index (GI),⁶ and three-point index (TPI)⁷ are the most commonly used. Although many studies have shown that they are essential in predicting reduction loss, their use alone may not be sufficient in predicting LOR.⁸-¹⁰

In retrospective evaluations of pediatric tibia fractures treated with Closed Reduction and Casting (CRC), it was suggested that the initial excessive displacement of the fracture, causative high-energy trauma, and accompanying fibula fracture might be the possible factors that affect LOR within the cast.^11–13 In addition, it is conceivable that the dissolution of soft tissue edema in the plaster and poorly made cast may also cause LOR. Although in children, fracture healing is rapid and axial deformities have a high capacity to remodel spontaneously; it has been shown that remodeling does not always wholly occur, especially in children older than 10 years.¹⁴ Therefore, the prevention of LOR of tibia fractures in the cast is essential for the success of the treatment, especially in older children.

To our knowledge, there is only one study investigating the role of Cast Index (CI), Gap Index (GI), and Three-Point Index (TPI) in prediction of LOR in conservatively treated pediatric tibia fractures.⁷ Our study aims to analyze the factors that may cause LOR in pediatric tibia diaphyseal and distal third fractures treated with CRC and to investigate the effectiveness of CI, GI, and TPI in predicting LOR. We hypothesized that reduction quality and CI are predictive factors for LOR in the cast. In all cases, casting was performed by using plaster of Paris.

Materials and Methods

The local ethical committee approved this retrospectively designed study. Between January 2014 and January 2018, patients aged 0-16 years who were admitted to the emergency department with tibia diaphyseal or distal third fractures (ICD-10 code; S.82.2 and S.82.3) which were treated with CRC were found using the hospital's digital archive. A total of 645 patients were identified. After exclusion of 293 patients recorded with an incorrect diagnostic code, 352 patients were evaluated. Mashru et al.³ described coronal and sagittal angulation up to 10°, translation less than 50% and shortening of less than 10 mm as an acceptable alignment in tibia fractures in children younger than 8 years of age. The acceptable angulation decreases to 5°in older children. Fractures that do not require reduction maneuvers according to these criteria, pathological fractures, fractures that underwent surgical fixation, patients without adequate follow-up, and patients without appropriate follow-up radiographs were excluded from the study. After applying exclusion criteria, a total of 196 pediatric patients with tibial fractures who underwent CRC were included in the study.

Fractures were reduced under sedation in the emergency room and followed with a long leg splint until the edema resolved. Patients with severe soft tissue injuries and excessive swelling were hospitalized and followed up for possible compartment syndrome occurrence, and the others were called for outpatient clinic follow-ups. After the edema resolved, a long leg cast was applied by an orthopedic resident who was at the second to fifth year of training. The patients were invited to the weekly outpatient follow-ups in order to check the position of fracture radiologically for the first 3 weeks of treatment. The cast treatment of the patients continued for an average of 6-8 weeks according to the fracture healing status.

The patients’ demographic data were scanned from hospital’s records and pre-reduction, post-reduction, and follow-up radio-graphs from the hospital’s digital archive. The radiographs of the patients at admission were analyzed in terms of fracture type (spiral, short oblique, transverse, comminuted), location of the fracture, presence, and location of the fibula fracture (within the 50 mm of tibial fracture or not), initial angulation in both planes and translation, and the time of definitive casting. On radiographs taken after closed reduction and final casting, angulation in the coronal and sagittal planes, amount of translation (%), CI, GI, and TPI were measured. The measurements were performed by the use of the Picture Archiving and Communication System. Re-manipulation, wedging, or continuation decisions on follow-up radiographs were made according to the criteria described by Mashru et al.³ The fractures that were out of acceptable limits in terms of angulation and shortening were accepted as LOR. The first and second authors performed the measurements and evaluations, the average values were recorded, and the intra-class correlation coefficient (ICC) values were calculated for inter-observer reliability evaluation of radiographic measurements which were interpreted as poor to excellent (Table 1). The descriptions and formulas used to measure these indices are summarized in Table 2 and depicted in Figures 1, 2 and 3.

Table 1.

Inter-observer reliability values of radiologic measurements

	ICC score	95% Confidence	interval Interpretation
Initial AP angulation	0.994	0.982-0.998	Excellent
Initial lateral angulation	0.998	0.993-0.999	Excellent
Initial translation	0.990	0.972-0.997	Excellent
Post-reduction AP angulation	0.990	0.970-0.997	Excellent
Post-reduction lateral angulation	0.997	0.991-0.999	Excellent
Post-reduction translation	0.993	0.980-0.993	Excellent
Cast index	0.758	0.279-0.919	Good
Gap index	0.622	0.125-0.879	Moderate
Three-point index	0.473	0.153-0.873	Poor

ICC, Intra-Class Correlation Coefficient; AP, Anteroposterior.

Table 2.

Descriptions and cut-off values of radiological indices

	Description	Cut-off value
Cast index5	Sagittal cast inner diameter (x)/coronal cast inner diameter (y) at the fracture level (x/y)	1.02
Gap index6	At the fracture level [medial skin-cast gap (b) + lateral skin-cast gap (a)/inner diameter of cast (x) in AP view] + [anterior skin-cast gap (c) + posterior skin-cast gap (d)/inner diameter of cast (y) in lateral view] (b + a)/x +(d + c)/y	0.17
Three-point index7	[In AP view, narrowest skin-cast gap 1 cm within fracture line (b) + narrowest gaps 3-7 cm proximal (a) + 3-7 cm distal to fracture line (c)/transverse projection of the fracture contact area (x) in AP view] + [In lateral view, narrowest skin-cast gap 1 cm within fracture line (e) + narrowest gaps 3-7 cm proximal (d) + 3-7 cm distal to fracture line (f)/ transverse projection of the fracture contact area (y) in lateral view] (a + b + c)/x +(d + e + f)/y

AP, Anteroposterior.

Figure 1.

Depicition and calculation of cast index (x/y) and gap index [(c + d)/x +(a + b)/y].

Figure 2.

Measurements of cast index (x/y) and gap index [(c + d)/x +(a + b)/y].

Figure 3.

Measurement of TPI in tibia fracture without fibula fracture (in cases, the fibula is fractured, points a and c are selected on the lateral side of the leg).

Statistical analysis

The Statistical Package for Social Sciences version 17 for Windows was used for the statistical analysis (SPSS Inc., Chicago, IL, USA). Continuous data were first evaluated using the Shapiro–Wilk test for normality. The data with normal distribution were compared using the Student's T-test. If the continuous data were non-normally distributed, the comparison was made with the Mann–Whitney U-test. Categorical data were evaluated using Fisher’s exact test or chi-squared test. Binary logistic regression was performed to investigate possible risk factors for LOR. Factors below P < 0.05 in univariate analyses were included in multiple models. ICC scores were calculated to assess the inter-observer reliability of radiological measurements. ICC values less than 0.5, between 0.5 and 0.75, between 0.75 and 0.9, and greater than 0.90 were accepted classified as poor, moderate, good, and excellent reliability, respectively.¹⁵ MedCalc Statistical Software version 15.8 (MedCalc Software bvba, Ostend, Belgium; https://www.medcalc.org; 2015) was used for the Receiver Operating Characteristic (ROC) curve analysis. Statistical significance was set at P < 0.05.

Results

Descriptive data of patients were given in Table 3. One hundred and ninety-six patients consisting of 41 (%21) female and 155 (%79) male were evaluated, and the mean age of patients was 8.9 ± 3.1 (3-14) in the LOR group and 7.7 ± 3.4 (1-15) in no LOR group (P = 0.029). No nonunion was observed in any of the patients. LOR was observed in 46 (23%) of 196 patients. Re-manipulation and cast change were applied to 18 (39%) of these patients and 15 (32%) had cast wedging. Three patients (7%) had to be operated on. The acute intervention was not performed on 10 (22%) patients, and they were closely followed radiologically and clinically. Since no further LOR developed in the follow-up, they were left to natural remodeling with minimal LOR.

Table 3.

Pre-casting risk factors

	Re-displacement	No redisplacement	P
	(n: 46)	(n: 150)
	Mean ± SD (min-max)	Mean ± SD (min-max)
Age (months)	8.9 ± 3.1 (3-14)	7.7 ± 3.4 (1-15)	0.029
Gender (n)
Girl	6	35	0.095
Boy	40	115
Fracture location
Diaphisis	26	74	0.247
Distal third	20	76
Fracture type (n)
spiral/oblique/transverse/comminuted (n)	26/14/4/2	66/41/36/7	0.148
Fibula fracture (n)
Present	24	64	0.167
Absent	22	86
Fibula fracture (n)
Within 5 cm	23	59	0.638
> 5 cm	2	5
Initial AP angulation (°)	6.3 ± 4.9 (0-20)	5.5 ± 5.4 (0-29)	0.164
Initial lateral angulation (°)	5.7 ± 4.8 (0-20)	4.8 ± 4.7 (0-26)	0.179
Initial translation (%)	34.2 ± 25.8 (0-100)	24.9 ± 22.3 (0-100)	0.006
Time to casting (day)	3.7 ± 3.4 (0-13)	3.6 ± 3.6 (0-21)	0.867

AP, Anteroposterior.

There was no statistically significant difference between LOR and no LOR groups in terms of gender, fracture location, fracture type, presence and location of fibula fracture, initial Anteroposterior (AP) lateral angulation, and time to the final casting. Among the pre-casting risk factors, only age and initial translation percentages were statistically significantly different between the two groups (p = 0.029 and 0.006, respectively) (Table 3). Among the residual angulations and displacements after reduction and casting, post-reduction translation and post-reduction AP angulation were found to be statistically significantly different between the two groups (P = 0.001 and P = 0.002, respectively) (Table 4).

Table 4.

Post casting risk factors

	Re-displacement	No re-displacement
	(n: 46)	(n: 150)	P
	Mean ± SD (min-max)	Mean ± SD (min-max)
Post-reduction AP angulation	4.4 ± 3.2 (0-13)	2.7 ± 2.1 (0-10)	0.002
Post-reduction lateral angulation	2.7 ± 2.8 (0-13)	2.7 ± 2.7 (0-12.9)	0.843
Post-reduction translation (%)	28.1 ± 16.9 (0-70.5)	18.2 ± 13.2 (0-57.2)	0.001
Cast index
<1.02	12	75	0.003
>1.02	34	75
Gap index
<0.17	15	75	0.028
>0.17	31	75
Three-point index
<1.11	12	53	0.162
>1.11	34	97

AP, Anteroposterior; SD, Standart Deviation; min, Minimum; max, Maximum.

There was a statistically significant difference between the two groups in terms of mean CI (P = 0.033) and GI (P = 0.036), but the difference in respect of mean TPI (P = 0.473) was not statistically significant (Table 5). ROC curve analysis was performed for the radiological indices, age, initial translation, post-reduction AP angulation, and translation (Table 6). The cut-off value of CI was 1.02 (area under curve: 0.604, sensitivity: 73.9, and specificity: 52.7), cut-off value of GI was 0.17 (area under curve: 0.603, sensitivity: 67.4, and specificity: 51.3) and cut-off value of TPI was 1.11 (area under curve: 0.534, sensitivity: 73.9, and specificity: 35.3).

Table 5.

Data of radiological indices

	Re-displacement	No re-displacement
	(n: 46)	(n: 150)	p
	Mean ± SD (min-max)	Mean ± SD (min-max)
Cast index	1.06 ± 0.99 (0.89-1.42)	1.03 ± 0.8 (0.75-1.52)	0.033
Gap index	0.19 ± 0.06 (0.07-0.34)	0.17 ± 0.07 (0.05-0.45)	0.036
Three-point index	1.48 ± 0.67 (0.48-4.28)	1.45 ± 0.88 (0.28-8)	0.473

Table 6.

Multivariate logistic regression analyses of risk factors for re-displacement

	P	Odds ratio	95% Confidence interval
Age (increased)	0.527	1.040	0.921-1.173
Gender (girl)	0.586	0.750	0.266-2.111
Initial translation	0.761	1.003	0.984-1.022
Post-reduction AP angulation	0.001	1.289	1.108-1.501
Post-reduction translation	0.003	1.046	1.015-1.078
Cast index	0.031	112.708	1.545-8223.088
Gap index	0.275	24.537	0.079-7656.079

AP, Anteroposterior.

According to the result of binary logistic regression analysis, post-reduction AP angulation of >3.4°[odds ratio: 1.289 (1.108-1.501, 95% CI)], post-reduction translation of > 24.3% [odds ratio: 1.046 (1.015-1.078, 95% CI)], and CI of > 1.02 [odds ratio: 112.708 (1.545-8223.1, 95% CI)] were independent risk factors for the occurrence of LOR (Table 6).

Discussion

Pediatric tibia fractures can be successfully treated with CRC if the initial or post-reduction alignments are within acceptable limits.¹-³ Many factors related to injury or casting may cause LOR of the fracture in the cast during follow-up.⁴ In our study, factors that may cause LOR were investigated, and among these, post-reduction AP angulation and translation and CI were found to be independent risk factors of reduction loss. According to the results of the study, our hypothesis was partially confirmed.

In low-energy pediatric tibia fractures, an uninjured periosteal hinge helps the reduction and maintains fracture stability after the reduction. Therefore, in these fractures, there is less displacement in each plane initially, and displacement within the cast is less common. In high-energy fractures, soft tissue injury and swelling are more common, and it is more appropriate to rest the leg in a long leg splint until the edema resolves.¹⁶ In addition, the most crucial thing during casting is to use a thin layer of cotton and mold the cast properly. The cast must be molded in the opposite direction of the fracture to be displaced. In tibia fractures with the intact fibula, the valgus mold has to be applied to prevent varus deformity, and when the fibula is broken, the varus mold must be performed.⁴

In pediatric tibia fractures treated with CRC, 20-44% LOR has been reported requiring re-reduction, wedging, or operation.^11–17 Canavese et al.¹⁵ reported that 33% LOR developed in 54 children with tibial fractures treated conservatively. However, only one of these patients was operated on. In our study, LOR was observed in 23% (46/196) of patients, consistent with the literature, and only three patients had to be operated on. In this treatment method, it should be told to the patient’s parents that the casting period may take a long time, complications such as pressure sores and joint stiffness may develop due to the cast, and that re-manipulations may be required due to the LOR. Nowadays, after the popularization of titanium elastic nails, more pediatric tibia fractures are treated surgically.¹⁸ Internal fixation of the fractures reduces the risk of LOR. However, complications such as nail irritation, delayed union, nonunion, and infection may be seen after internal fixation.^14,16,18 The rapid healing potential and high remodeling capacity of pediatric bones should always be kept in mind.

Several casting indices determine the quality of cast application with formulas created due to measurements made on AP and lateral radiographs.⁵-⁷ The CI is measured by the ratio of internal cast diameters in the coronal and sagittal plane, determines the cast molding’s quality, and distinguishes between the correct and poorly molded cast.⁵ In the present study, a significant relationship has been found between CI and LOR. Ozturk et al.¹³ could not find a relationship between the CI and LOR. Shalabh et al.¹⁹ evaluated a small group of adult patients treated with CRC and found no significant difference in CI between groups with and without LOR. Although the cut-off values for the CI were found to be close in all three studies, the results differed from each other. In our study, after multivariate regression analysis, the CI was found to be an important independent risk factor for LOR. Among the three indices, CI was found to have the highest specificity and sensitivity (Figure 4).

Figure 4.

ROC analysis of radiographic indices.

During the GI measurement, the distances between the skin and plaster were also calculated in addition to the ratio of inside plaster diameter in the fracture line.⁶ Thus, it can be evaluated whether both molding and the plaster are made appropriately. Ozturk et al.¹³ showed a statistically significant difference in mean GI value between the groups with and without LOR. Shalabh et al.¹⁹ did not find the GI significant in predicting the LOR. In our study, the relationship between GI and LOR was significant. There may be a difference between the initial GI measurements and the measurements made after the edema was resolved in patients who underwent casting immediately after injury. This difference may cause the reliability of the GI to be questioned. In our daily practice, the final casting of high-energy tibia fractures is performed at the outpatient clinics, and in a recent study, the meantime to definitive casting was 5.5 ± 2.4 (0-13) days. Therefore, our GI measurements are reliable and would not change over time.

Alemdaroglu et al.⁷ described the three-point index in distal radius fractures, and Ozturk et al.¹³ were first to investigate it in pediatric tibia fractures treated with casting. TPI uses the three-point fixation principle, and the critical gaps used in TPI measurement are selected from the points where the plaster is closest to the skin, and it is most resistant to displacement forces to maintain reduction.⁷ Ozturk et al.¹³ claimed that TPI has a predictive ability for LOR than CI and GI in pediatric tibial fractures. In our study, no statistically significant difference was found between the two groups in terms of TPI. Many studies have been shown as a good measure for predicting displacement in distal radius fractures in children.⁷-⁹ However, the complexity of calculating TPI makes one think that it is more suitable for clinical research than daily practice. Additionally, inter-observer reliability of TPI measurement was found to be poor in our study.

In children, isolated tibia fractures in which the fibula remains intact constitute 75% of all tibia fractures.¹⁷,²⁰ Although fibula fracture is thought to increase instability in tibia fractures, Yang et al.¹⁷ suggested that when the fibula remains intact, both the reduction of the tibia and the maintenance of the reduction in the plaster are more complicated. Briggs et al.²⁰ reported that in isolated tibia fractures, no LOR occurs in transverse tibia fractures, whereas varus deformity may develop in spiral and oblique fractures. Our study observed that neither the presence of the fibula fracture nor the distance to the tibia fracture affects LOR (p = 0.148, p = 0.167, respectively). In addition, the relationship between fracture type and reduction loss was not found to be statistically significant.

As a result of high-energy traumas, more soft tissue and periosteum are damaged, and more angulation and displacement can be seen in each plane. Ho et al.¹¹ reported that 13/75 adolescents with tibia fractures treated with CRC required cast change or wedging, and three patients required surgery. They also showed a statistically significant difference between groups that needed and did not need further intervention in initial AP angulation, lateral angulation, translation, and post-reduction AP angulation and translation. No significant relationship was found between initial coronal and sagittal angulations and LOR in our study. Ozturk et al.¹³ suggested that translation deformity is more associated with periosteal damage, and the risk of LOR increases as translation increases. In our study, both initial translation and post-reduction translation were risk factors for LOR.

Our study has limitations. The most important limitation is that it was designed retrospectively.

In conclusion, although LOR in pediatric tibia fractures treated with CRC is a very complex subject to be reduced to a few risk factors, patients with CI of > 1.02, post-reduction AP angulation of > 3.4°, and post-reduction translation of > 24.3% should be carefully evaluated for LOR.

Funding Statement

The authors declared that this study has received no financial support.