Orthopedics

Review Article 

Complications Following Internal Fixator in the Treatment of Pelvic Fracture

Yingchao Yin, MD; Ruipeng Zhang, MD; Shilun Li, MD; Ke Su, MD; Zhiyong Hou, MD; Yingze Zhang, MD

Abstract

The aim of this systematic review was to investigate the incidence of complications of the internal fixator in the treatment of anterior pelvic ring injury. The literature was comprehensively searched from 1980 to January 2017 to identify potential studies. Six studies involving 272 cases of anterior pelvic ring injury treated with the internal fixator were included in this meta-analysis. The rates of wound infection, heterotopic ossification, nerve paresthesia, pain, and fracture dislocation were 5.7%, 35.1%, 28.2%, 3.7%, and 3.0%, respectively. This new technique should be prudently used to treat pelvic fractures. [Orthopedics. 2019; 42(1):e7–e13.]

Abstract

The aim of this systematic review was to investigate the incidence of complications of the internal fixator in the treatment of anterior pelvic ring injury. The literature was comprehensively searched from 1980 to January 2017 to identify potential studies. Six studies involving 272 cases of anterior pelvic ring injury treated with the internal fixator were included in this meta-analysis. The rates of wound infection, heterotopic ossification, nerve paresthesia, pain, and fracture dislocation were 5.7%, 35.1%, 28.2%, 3.7%, and 3.0%, respectively. This new technique should be prudently used to treat pelvic fractures. [Orthopedics. 2019; 42(1):e7–e13.]

Fractures of the pelvic ring frequently involve disruption of the anterior and posterior bony and ligamentous structures. Anterior fixation has often been used in conjunction with posterior fixation to treat instability of the pelvic ring and has traditionally been performed with either plates or anterior external fixators.1 External fixation for high-energy pelvic ring injuries is effective in providing initial stabilization, minimizing fracture fragments movement, reducing pelvic volume, and causing a tamponade for pelvic venous hemorrhage and hematoma.2,3 However, the complications associated with external fixators include osteomyelitis, loss of reduction, pin tract infection, skin compression, and nerve damage.4 Moreover, the cumbersome inferoanterior–abdominal external fixator limits patient mobility, especially when sitting, being in a lateral position and rolling from side to side.5

To avoid these complications and this inconvenience, several novel techniques have been proposed by orthopedists to stabilize the anterior pelvic ring internally.6–9 Like pelvic external fixation, the internal fixator (INFIX) has 2 screws placed into each ilium,7,10–13 but the contoured rod that connects the screws is applied subcutaneously. The indications for this technique include obese patients with an anterior pelvic injury and other patients who are not suitable for the external fixator. The INFIX has been reported to have better biomechanical stability than an external fixator; eliminate open pin tracts, resulting in improved patient compliance and comfort; and have reduced need for nursing surveillance.14,15 The external fixator cannot achieve stability in severely overweight patients because of the amount of subcutaneous fat on the abdomen.16 The INFIX was originally designed as an alternative to external fixation for obese patients with pelvic fractures and has been widely used recently for patients with anterior pelvic ring injuries.7,17 However, a higher rate of lateral femoral cutaneous nerve (LFCN) irritation has been reported, and the device is not well tolerated by some patients.18–20

Complications have been reported for pelvic injuries treated with the INFIX, varying considerably from study to study.11–13,18–20 The purpose of this study was to perform a systematic review and meta-analysis of complications associated with the INFIX in the treatment of anterior pelvic ring injury.

Materials and Methods

Literature Search and Study Selection

Using the PubMed, Embase, and Cochrane databases, the authors performed a literature search from 1980 to January 2017. Although there was no protocol for this systematic review, every step was strictly performed according to the guidelines of the Cochrane Collaboration. The following terms were used to identify relevant studies: “pelvic fracture,” “pelvis fracture,” “pelvic injuries,” “pelvic ring fractures,” “pelvic ring injuries,” “INFIX,” “anterior subcutaneous pelvic fixation,” “subcutaneous frame internal fixator,” “anterior subcutaneous internal fixation,” “subcutaneous anterior pelvic fixator,” “subcutaneous connecting rod,” “supraacetabular spinal pedicle screw,” and “internal anterior fixator.” This search was performed in February 2017.

Eligibility Criteria

Two authors (Y.Y., R.Z.) independently evaluated the titles and abstracts of the identified articles. The inclusion criteria were as follows: (1) target population— patients with anterior pelvic ring fracture; (2) intervention—treated with 2 single supraacetabular pedicle screws placed on each ilium and a subcutaneous curved rod connecting the screws; (3) article types— any but case reports, cadaveric studies, biomechanical studies, or techniques; and (4) language—English. The authors included the language restriction to enhance the quality of this meta-analysis. Duplicate or multiple publications of the same study were excluded.

Quality of Included Studies

The quality of the included studies was evaluated using the Methodological Index for Non-Randomized Studies, which is a validated tool for evaluating the quality of nonrandomized surgical studies.21 Two authors (Y.Y., R.Z.) assessed the quality of each article independently. All 6 studies included in this meta-analysis were non-comparative studies11,12,17–20; thus, only the first 8 items of the Methodological Index for Non-Randomized Studies were used, and the maximum score was 16. Studies that received at least 75% of the maximum Methodological Index for Non-Randomized Studies score were considered to be of high quality, consistent with previous research.22,23

Data Extraction

Two authors (S.L., K.S.) independently extracted all relevant data. The following data were extracted from each eligible study: first author, publication year, study design, number of patients, mean age, type of fracture, Injury Severity Score, follow-up time, weight-bearing time, removal time, and complications (Table 1).

Characteristics of the 6 Included Studiesa

Table 1:

Characteristics of the 6 Included Studies

Statistical Analysis

The incidence rate of every complication was estimated and pooled across studies to assess INFIX-treated anterior pelvic ring injury. Heterogeneity among studies was tested by Q-test statistics, with significance set at P<.10, and the I2 test, with a value greater than 50% representing substantial heterogeneity.24 A random effects model (DerSimonian–Laird) was used to calculate a pooled incidence rate in the case of significant heterogeneity (P<.10 or I2>50%); otherwise, a fixed effects model was used. For every complication, the outcome of the meta-analysis was summarized graphically using a forest plot. Sensitivity analyses were performed according to the size of the confidence interval of the individual study. All analyses were performed using Stata version 12.0 software (Stata Corporation, College Station, Texas).

Results

Literature Search

The initial literature search identified 70 relevant articles published from January 1995 to February 2017. Fifty-five articles remained after screening by reading titles and abstracts. After the case reports, biomechanical research, and some studies uncorrelated with the INFIX were excluded, 9 articles remained for full-text assessment. Three duplicate studies were excluded, leaving 6 studies (272 cases) (Figure 1). The quality assessment revealed that 1 study17 scored 14 and 5 studies11,12,18–20 scored 13.

Flow diagram of the literature search for the meta-analysis. Abbreviation: INFIX, internal fixator.

Figure 1:

Flow diagram of the literature search for the meta-analysis. Abbreviation: INFIX, internal fixator.

Pooled Complication Rates of the INFIX

The 6 studies included 272 patients with anterior pelvic ring fractures treated with the INFIX. The pooled complication rates using a random effects model (Der-Simonian–Laird) of wound infection, heterotopic ossification, nerve paresthesia, pain, and fracture dislocation were 5.7% (95% confidence interval [CI], 3% to 11%) (Figure 2), 35.1% (95% CI, 31.8% to 38.7%) (Figure 3), 28.2% (95% CI, 17.8% to 44.6%) (Figure 4), 3.7% (95% CI, 2.0% to 6.9%) (Figure 5), and 3.0% (95% CI, 1.6% to 5.5%) (Figure 6), respectively. The results of a meta-analysis of combinable data to analyze the complication rates for INFIX-treated anterior pelvic ring fracture are summarized in Table 2.

Forest plot of the complication rate meta-analysis for wound infection. The width of the horizontal line represents the 95% confidence interval (CI) of each study, and the square proportional represents the weight of each study. The rhombus represents the pooled rate and 95% CI.

Figure 2:

Forest plot of the complication rate meta-analysis for wound infection. The width of the horizontal line represents the 95% confidence interval (CI) of each study, and the square proportional represents the weight of each study. The rhombus represents the pooled rate and 95% CI.

Forest plot of the complication rate meta-analysis for heterotopic ossification. The width of the horizontal line represents the 95% confidence interval (CI) of each study, and the square proportional represents the weight of each study. The rhombus represents the pooled rate and 95% CI.

Figure 3:

Forest plot of the complication rate meta-analysis for heterotopic ossification. The width of the horizontal line represents the 95% confidence interval (CI) of each study, and the square proportional represents the weight of each study. The rhombus represents the pooled rate and 95% CI.

Forest plot of the complication rate meta-analysis for nerve paresthesia. The width of the horizontal line represents the 95% confidence interval (CI) of each study, and the square proportional represents the weight of each study. The rhombus represents the pooled rate and 95% CI.

Figure 4:

Forest plot of the complication rate meta-analysis for nerve paresthesia. The width of the horizontal line represents the 95% confidence interval (CI) of each study, and the square proportional represents the weight of each study. The rhombus represents the pooled rate and 95% CI.

Forest plot of the complication rate meta-analysis for pain. The width of the horizontal line represents the 95% confidence interval (CI) of each study, and the square proportional represents the weight of each study. The rhombus represents the pooled rate and 95% CI.

Figure 5:

Forest plot of the complication rate meta-analysis for pain. The width of the horizontal line represents the 95% confidence interval (CI) of each study, and the square proportional represents the weight of each study. The rhombus represents the pooled rate and 95% CI.

Forest plot of the complication rate meta-analysis for fracture dislocation The width of the horizontal line represents the 95% confidence interval (CI) of each study, and the square proportional represents the weight of each study. The rhombus represents the pooled rate and 95% CI.

Figure 6:

Forest plot of the complication rate meta-analysis for fracture dislocation The width of the horizontal line represents the 95% confidence interval (CI) of each study, and the square proportional represents the weight of each study. The rhombus represents the pooled rate and 95% CI.

Meta-analysis of Complications of Anterior Pelvic Ring Fracture Treated by Internal Fixator

Table 2:

Meta-analysis of Complications of Anterior Pelvic Ring Fracture Treated by Internal Fixator

Sensitivity Analysis

The authors conducted a sensitivity analysis for the incidence of complications that presented with significant heterogeneity. The results indicated that the heterogeneity of wound infection and heterotopic ossification could be reduced by removing the study by Hoskins et al20 (Tables 35).

Sensitivity Analyses Based on Various Exclusion Criteria for Wound Infection

Table 3:

Sensitivity Analyses Based on Various Exclusion Criteria for Wound Infection

Sensitivity Analyses Based on Various Exclusion Criteria for Heterotopic Ossification

Table 4:

Sensitivity Analyses Based on Various Exclusion Criteria for Heterotopic Ossification

Sensitivity Analyses Based on Various Exclusion Criteria for Nerve Paresthesia

Table 5:

Sensitivity Analyses Based on Various Exclusion Criteria for Nerve Paresthesia

Discussion

This analysis of 272 patients from the literature is the first systematic review to pool the complication rates of anterior pelvic ring injuries treated by the INFIX. The systematic review included 6 studies. The authors conducted a complication rate meta-analysis to evaluate the efficacy of the INFIX in the treatment of pelvic injury. They estimated the rates of wound infection, heterotopic ossification, nerve paresthesia, pain, and fracture dislocation to be 5.7%, 35.1%, 28.2%, 3.7%, and 3.0%, respectively.

To maximize the accuracy of this meta-analysis, suitable articles were found via searches of the PubMed, Embase, and Cochrane databases. Studies were excluded according to the eligibility criteria, and the quality of the literature incorporated into the review was scored using the Methodological Index for Non-Randomized Studies. Furthermore, to ensure that the correct information was retrieved from each article, data were extracted by 2 of the authors (Y.Y., R.Z.) independently. Because the INFIX is a new technique, few randomized controlled trials exist. The paucity of eligible studies and patients treated with the INFIX leads to relatively larger heterogeneity. The sensitivity analysis showed that the heterogeneities of wound infection and heterotopic ossification were lower when the study by Hoskins et al20 was removed. One possible explanation was variation in the INFIX removal time (109 days) among the included studies (Table 1). More prospective research should be conducted to evaluate the INFIX more comprehensively.

This systematic review revealed a high complication rate, especially heterotopic ossification (35.1%) and nerve paresthesia (28.2%), associated with the INFIX in the treatment of anterior pelvic fracture. However, Hoskins et al20 reported a much higher rate (57%) of nerve paresthesia in their research. They inserted a pedicle screw that was 10 mM in diameter, which is larger than the 7- to 8.5-mM screw used by Vaidya et al,17 into the anterior inferior iliac spine. The relatively large screw may be a reason for the traction neurapraxia, as the incision and blunt dissection were similar to those of Scheyerer et al,13 who reported no nerve symptoms when using a smaller screw. Studies should be conducted to evaluate the optimum screw diameter to maintain pelvic fracture stability. Hoskins et al20 reported that all of the nerve symptoms improved after INFIX removal. Previous studies reported a high rate of asymptomatic heterotopic ossification20,25 that did not interfere with hip function or lead to any symptoms. Despite this, prophylactic treatment, such as nonsteroidal anti-inflammatory drugs or radiation, should be considered to prevent heterotopic ossification.26 The INFIX was proposed to reduce the risk of pin tract infection and to decrease the need for nursing surveillance, particularly in obese patients.6,7 However, the contoured rod must be placed subcutaneously at the front of the abdominal cavity. Furthermore, the subcutaneous INFIX should be removed once union of the fracture is complete. Secondary surgery increases the risk of lateral LFCN injury and the financial burden for patients. Finally, the INFIX technique can only maintain the stability of the pelvic ring; the anterior pelvic anatomic shape cannot be obtained through closed reduction. Because this is a new technique, there is a steep learning curve for surgeons.

The INFIX was used to treat either vertically (Young–Burgess type VS) or rotationally (Young–Burgess type LC, APC) unstable pelvic fractures (Table 1). Of the 6 included studies, only 2 studies described the full weight-bearing time. In 2012, Vaidya et al17 performed a multicenter study in which patients were permitted to perform toe-touch weight bearing on the side of posterior injury starting at 8 to 12 weeks, with non–weight bearing being indicated if bilateral posterior pelvis injury occurred. In a study conducted in 2017,18 all 83 patients, except 2 with spinal cord injury and 2 with pathological fracture, were permitted to be full weight bearing by 12 weeks postoperatively.

The current study had some limitations, which are inherent to a meta-analysis. First, the INFIX is a new technique that has been recently described.6,7,27 Therefore, once biomechanical studies,5,16,28,29 case reports,27,30,31 technical notes,13 and duplicated studies7,25,32 were excluded, few articles remained. Second, most of the studies found in the literature were retrospective in nature. Retrospective designs are prone to data inaccuracy as well as missing information, which subjects them to many biases (ie, selection bias and detection bias). Invariably, this diminishes their quality; thus, the quality of this review was affected. Although this systematic review reports a more accurate complication rate for INFIX-treated anterior pelvic ring fractures, prospective investigations are required. Because of the small number of studies included, publication bias could not be detected.

Conclusion

Minimally invasive internal fixation with subcutaneous screws and a rod for anterior pelvic ring fractures is an alternative to anterior external fixation. The subcutaneous technique makes the INFIX well suited to obese patients or other patients who cannot endure the inconvenience of an external fixation device. A higher complication rate, especially LFCN palsy and heterotopic ossification, has been reported. The pedicle screw size may lead to LFCN palsy. If neurological symptoms occur, it is advisable to remove the INFIX as soon as possible after fracture union. Prophylactic treatment, such as nonsteroidal anti-inflammatory drugs or radiation, should be considered to prevent heterotopic ossification. This new technique should be used prudently to treat pelvic fractures. Further anatomical studies should be conducted to reduce the incidence of LFCN and heterotopic ossification.

References

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Characteristics of the 6 Included Studiesa

Study (Year)Study DesignNo. of PatientsMean Age, yFracture TypeMean Injury Severity ScoreMean Follow-upWeight-bearing TimeMean Removal TimeComplications
Merriman et al11 (2012)RS13---29 wk (range, 5–76 wk)--Superficial wound breakdown without infection (n=1)
Vaidya et al17 (2012)RS9139.25 LC1 14 LC2 15 LC3 16 APC2 14 APC3 20 VS 7 CM-15 mo (range, 6–40 mo)8–12 wk-Early revisions resulting from technical error (n=6) Infection (n=3) Irritation of the lateral femoral cutaneous nerve (n=27) Asymptomatic heterotopic ossification (n=32) Loss of reduction (n=3)
Müller et al12 (2013)RS3645.2±3.2925 type C1.3 2 type C2 7 type C3.3 1 type C1.1 1 type C3.225.17±1.7253.48±5.1 mo (range, 18–101 mo)-9.4 mo (range, 27 d-40.2 mo), 30 patientsNonunion malalignment in both the posterior and the anterior pelvic region (n=1) Loosening of the posterior iliolumbar instrumentation (n=1) Infection (n=2) Heterotopic ossification (n=9)
Hoskins et al20 (2016)PS213912 LC1 6 LC2 2 APC3 1 APC223 (range, 5–43)342 d-109 d, 19 patientsWound infection (n=3) Lateral femoral cutaneous nerve neuropathic pain (n=1) Lateral femoral cutaneous nerve palsy (n=12) Asymptomatic heterotopic ossification (n=9) Symptomatic due to the bar (n=1)
Zhang et al19 (2016)RS2839.83 APC2 8 LC1 11 LC2 6 VS-8.7 mo (range, 6–12 mo)-Within 6 mo after surgery in 12 casesFemoral cutaneous nerve injuries (n=12)
Vaidya et al18 (2017)RS8341.7±15.918 VS 7 LC1 18 LC2 15 LC3 1 APC1 8 APC2 10 APC3 6 CM22.75±11.2 (median, 21; range, 5–57)35±12.4 mo (range, 12–80.33 mo)12 wk after operation (spinal cord injury [n=2] and 2 who had pathological fractures)5.3±5.4 mo (range, 0.3–49.5 mo)Infection (n=3) Implant failure (n=1) Implantation too deep (n=2) Lateral femoral cutaneous nerve irritation (n=7) Pain associated with the device (n=3) Asymptomatic heterotopic ossification (n=27) Discomfort clearly caused by the device (n=3)

Meta-analysis of Complications of Anterior Pelvic Ring Fracture Treated by Internal Fixator

ComplicationNo. of Relevant StudiesHeterogeneity (I2; P)Tau-squaredEstimate (95% Confidence Interval)Incidence Range
Wound infection567.3%; .0160.3450.057 (0.030–0.110)3.3%–14.3%
Heterotopic ossification370.1%; .0350.0050.351 (0.318–0.387)32.5%–42.9%
Nerve paresthesia597.4%; .0000.2390.282 (0.178–0.446)8.4%–61.9%
Pain20%; .79400.037 (0.020–0.069)3.6%–4.8%
Fracture dislocation20%; .34000.030 (0.016–0.055)1.2%–3.3%

Sensitivity Analyses Based on Various Exclusion Criteria for Wound Infection

Excluded Study (Year)No. of EventsTotal No. of PatientsHeterogeneity (I2; P)Estimate (95% Confidence Interval)
Merriman et al11 (2012)1123175.3%; .0070.055 (0.027–0.114)
Vaidya et al17 (2012)915365.6%; .0330.068 (0.031–0.147)
Müller et al12 (2013)1020875.5%; .0070.058 (0.025–0.130)
Hoskins et al20 (2016)92230%; .7370.039 (0.026–0.058)
Vaidya et al18 (2017)916169.5%; .0200.066 (0.029–0.150)

Sensitivity Analyses Based on Various Exclusion Criteria for Heterotopic Ossification

Excluded Study (Year)No. of EventsTotal No. of PatientsHeterogeneity (I2; P)Estimate (95% Confidence Interval)
Vaidya et al17 (2012)3610482.0%; .0190.366 (0.280–0.478)
Hoskins et al20 (2016)5917461.3%; .1080.339 (0.314–0.366)
Vaidya et al18 (2017)4111266.0%; .0870.377 (0.313–0.454)

Sensitivity Analyses Based on Various Exclusion Criteria for Nerve Paresthesia

Excluded Study (Year)No. of EventsTotal No. of PatientsHeterogeneity (I2; P)Estimate (95% Confidence Interval)
Vaidya et al17 (2012)4016898.0%; .0000.270 (0.135–0.541)
Müller et al12 (2013)5822398.0%; .0000.284 (0.167–0.482)
Hoskins et al20 (2016)5523897.0%; .0000.231 (0.145–0.368)
Zhang et al19 (2016)5523197.9%; .0000.247 (0.142–0.431)
Vaidya et al18 (2017)6017695.6%; .0000.368 (0.262–0.516)
Authors

The authors are from the Department of Orthopaedic Surgery (YY, RZ, SL, ZH, YZ), The Third Hospital of Hebei Medical University, and the Orthopaedic Surgery Department (KS), Cangzhou Central Hospital, Shijiazhuang, Hebei Province, China.

The authors have no relevant financial relationships to disclose.

This study was supported by the National Natural Science Foundation of China (grant 81572162).

Correspondence should be addressed to: Zhiyong Hou, MD, Department of Orthopaedic Surgery, The Third Hospital of Hebei Medical University, No. 139 Ziqiang Rd, Qiaoxi District, Shijiazhuang, 050051, Hebei Province, China ( drzyhou@gmail.com).

Received: November 21, 2017
Accepted: March 19, 2018
Posted Online: November 07, 2018

10.3928/01477447-20181102-06

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