Orthopedics

Feature Article 

Complications Associated With Pelvic External Fixation

Christopher McDonald, BS; Reza Firoozabadi, MD; M. L. Routt Jr, MD; Conor Kleweno, MD

Abstract

An external fixator is an essential tool for treating unstable pelvic ring injuries but its use carries risks, including pin-site infections and injury to the lateral femoral cutaneous nerve (LFCN). Surgeons currently lack data regarding these risks for patient counseling. This study aimed to identify the incidence of and risk factors for superficial and deep pin-site infection and LFCN damage. Fifty-two patients who underwent pelvic external fixation with anterior pin placement as part of definitive treatment for unstable pelvic ring disruption were retrospectively evaluated to identify factors associated with the development of infection. Ten (19%) patients developed superficial pin-site infections, with none developing a deep infection. Five were treated with oral antibiotics alone, 5 with additional intravenous antibiotics, and 1 underwent superficial surgical debridement at the time of external fixator removal. Three (6%) patients had temporary symptoms consistent with irritation to their LFCN that all resolved by 3 months. One (2%) patient had residual mild and intermittent LFCN dysesthesias at the 6-month follow-up. Adjusted logistic regression models identified no specific factors that were associated with increased risk of infection. The incidence of superficial infections related to pelvic external fixation was 19%, which can usually be treated with antibiotics with low risk of deep infection. In addition, there remains a low risk of long-term LFCN damage. Patients should be counseled on these risks during the perioperative period. [Orthopedics. 2017; 40(6):e959–e963.]

Abstract

An external fixator is an essential tool for treating unstable pelvic ring injuries but its use carries risks, including pin-site infections and injury to the lateral femoral cutaneous nerve (LFCN). Surgeons currently lack data regarding these risks for patient counseling. This study aimed to identify the incidence of and risk factors for superficial and deep pin-site infection and LFCN damage. Fifty-two patients who underwent pelvic external fixation with anterior pin placement as part of definitive treatment for unstable pelvic ring disruption were retrospectively evaluated to identify factors associated with the development of infection. Ten (19%) patients developed superficial pin-site infections, with none developing a deep infection. Five were treated with oral antibiotics alone, 5 with additional intravenous antibiotics, and 1 underwent superficial surgical debridement at the time of external fixator removal. Three (6%) patients had temporary symptoms consistent with irritation to their LFCN that all resolved by 3 months. One (2%) patient had residual mild and intermittent LFCN dysesthesias at the 6-month follow-up. Adjusted logistic regression models identified no specific factors that were associated with increased risk of infection. The incidence of superficial infections related to pelvic external fixation was 19%, which can usually be treated with antibiotics with low risk of deep infection. In addition, there remains a low risk of long-term LFCN damage. Patients should be counseled on these risks during the perioperative period. [Orthopedics. 2017; 40(6):e959–e963.]

Unstable pelvic ring fractures are severe injuries that have a high rate of morbidity and mortality.1–4 The acute use of external fixation of unstable pelvic fractures is an essential treatment tool and has been shown to reduce morbidity and mortality rates to levels seen in stable pelvic fractures.5–7 In certain instances, the external fixator is used as the definitive treatment or as an adjunct to posterior fixation for the pelvic injury and is kept on the patient for 6 weeks or longer.

One common complication of external fixation is pin-site infection associated with the Schanz pins (DePuy Synthes, Paoli, Pennsylvania).8–13 Pin-site infection can lead to chronic osteomyelitis, requiring extended courses of antibiotics, surgical debridement, and bone grafting.14,15 In addition to risks from the infection, pin-site infections complicate patients' recovery by re-introducing instability into the fracture site and delaying mobility and rehabilitation. Little data are available on superficial or deep infection rates after pelvic external fixation. Specifically, no studies have attempted to identify risk factors for developing pin-site infections after pelvic external fixation.

Another potential complication of external fixation specific to the pelvis is damage to the lateral femoral cutaneous nerve (LFCN) during surgery. Data on incidence of long-term damage to the LFCN remain limited.16

The purposes of this study were to identify the incidence of superficial and deep infections after pelvic external fixation and to examine which risk factors may increase the risk of postoperative pin-site infections. Secondarily, the study aimed to describe the incidence of LFCN injury.

Materials and Methods

This study was approved by the authors' institutional review board. A prospectively collected orthopedic trauma database at the authors' level I trauma center was retrospectively reviewed to identify patients who had undergone pelvic external fixation between January 2010 and December 2014. Included patients had presented with acute traumatic injuries to their pelvis deemed unstable by the treating surgeon and had an external fixator used as part of their treatment. Fractures were classified using both the AO/OTA system17 and the Young and Burgess classification.18

A total of 88 patients who underwent external fixation were identified, of which 20 had their external fixation removed and converted to an internal fixation during the course of their initial hospitalization without complication and were excluded from the study. Of the 68 remaining patients, 52 had their fixation done by anterior pin placement (starting at the anterior inferior iliac spine and directed into the sciatic buttress) and 16 had iliac crest pin placement. Pin placement was decided by the attending surgeon at the time of surgery.

Due to the small sample size of the 16 patients who underwent iliac crest pin placement, they were excluded from this study. Preoperative antibiotics were given with discontinuation within 24 hours, as per institutional protocol; 6 (12%) patients received an extended course of oral antibiotics that covered the entire duration of their external fixator (due to surgeon's preferred practice).

After operative fixation, patients were followed daily in the hospital until discharge. Furthermore, routine follow-up was scheduled for 2 weeks, 6 weeks, 3 months, 6 months, and 1 year postoperatively. However, only 5 patients were observed through the full postoperative year, with the rest lost to follow-up before that time. At each follow-up after the 2-week point, radiographs (anteroposterior/inlet/outlet) were taken of the pelvis and pin sites were examined for evidence of infection. Postoperative protocol for recommended pin-site care was the same among all patients and consisted of twice-daily cleanings with sterile saline, as per institutional protocol. Wounds were covered in sterile gauze until the wound was dry and then left open to air.

Superficial infections were diagnosed clinically as any evidence of progressive erythema, warmth, swelling, and/or drainage from the surrounding soft tissue with resultant administration of antibiotics without the diagnosis of osteomyelitis. Deep infections were defined as a pathology diagnosis of osteomyelitis or an extended course (12 weeks) of intravenous antibiotics for presumed osteomyelitis.

External fixators were used as part of the definitive treatment for the pelvic ring injury and were intended to be removed at approximately the 6-week point (unless early removal for infection). The external fixator was routinely removed in clinic unless the patient was unable to tolerate removal there. Numbness over the LFCN distribution was tested for during the physical examination at all of the patient's follow-up appointments, with any residual numbness or paresthesias noted in the patient's chart. This was distinct from incisional numbness present over the incision site and did not extend to the LFCN distribution. These examinations were performed by residents and confirmed by attendings, with full disrobing of the LFCN distribution.

STATA (StataCorp LLC, College Station, Texas) was used to organize the data and perform statistical analyses. Chi-square analyses and t tests were initially used to determine whether any risk factors were correlated with a statistically increased rate of infection without taking into account confounding from the other risk factors. To account for possible confounding of other risk factors on these correlations, a logistic regression was then run to isolate any risk factors that could independently be associated with an increased risk of infection. Statistical analysis was redone after removing these patients from the database, with no significant changes found in the results. Thus, there were no grounds for exclusion of these patients from the study.

Results

Of the 52 patients included for evaluation, 10 (19%) developed superficial pin-site infections during the course of their external fixation. No patients developed deep infections. Of the 10 patients who developed infections, 5 were treated with oral antibiotics, 1 had only intravenous antibiotics, and 4 had a combination of both oral and intravenous antibiotics. Two of the 10 patients required removal of their external fixation prior to 6 weeks due to the infection and 1 required revision of the fixation without needing premature removal.

This unilateral anterior pin-site loosening was in the setting of osteopenia and noncompliance of weight-bearing restrictions by the patient in the early postoperative period, with loosening noted on postoperative day 10. The pin was revised with no further complications. The other 7 patients kept their fixation without needing revision or early removal. Patients were followed for a mean of 177 days (SD, 214 days) after fixation of their pelvic fracture.

Six (12%) patients received an extended course of oral antibiotics that covered the entire duration of their external fixator (due to surgeon's preferred practice) and none of these had an infection. Mean duration of fixator time for these 6 patients was 46 days (range, 26–69 days). Five patients were treated with oral antibiotics alone, 5 with additional intravenous antibiotics, and 1 underwent superficial surgical debridement at the time of external fixator removal.

Four (8%) patients reported paresthesias consistent with LFCN irritation postoperatively. Of these, 3 had their LFCN symptoms resolve after 3 months, and only 1 patient reported continued mild intermittent dysesthesia at the 6-month follow-up and was then lost to follow-up. No patients reported severe pain.

Patients' mean age was 46.5±17.8 years. Mean overall duration of external fixator treatment was 52.3±16.8 days. Patients who developed an infection retained their external fixation for a mean of 47.7±18.3 days, and patients who never developed an infection retained their external fixation for a mean of 53.7±16.4 days (P=.314).

Chi-square and t test analyses of the individual risk factors and incidences of postoperative infection found that a lower American Society of Anesthesiologists score conferred a statistically significant risk for postoperative infection before logistic regression was performed. No other risk factors demonstrated statistical significance for increased risk of infection (Table 1).

Contribution of Different Risk Factors to the Development of Pin-Site Infection Without Consideration of Confounding

Table 1:

Contribution of Different Risk Factors to the Development of Pin-Site Infection Without Consideration of Confounding

Clinically, age, American Society of Anesthesiologists score, tobacco use status, and body mass index were thought to have the highest likelihood of being risk factors for infection and were thus specifically examined by linear regression to account for confounding between any of these variables. Even after taking into account the possibility of confounding by linear regression, none of the examined variables showed statistical significance in presenting a risk for infection (Table 2). Notably, a lower American Society of Anesthesiologists score was no longer statistically significant after logistic regression was performed to account for possible confounding (P=.088). Age (P=.798), American Society of Anesthesiologists score (P=.088), and tobacco use status (P=.706) all had increased P values after logistic regression. Body mass index had a lower P value (.167) after regression but was still not statistically significant.

Logistic Regression Results for the Patients Most Likely to Be at Risk for Infection Accounting for Possible Confounding of Other Variables

Table 2:

Logistic Regression Results for the Patients Most Likely to Be at Risk for Infection Accounting for Possible Confounding of Other Variables

Discussion

External fixation remains an essential tool for both the immediate and definitive treatment of unstable pelvic ring injuries. Regardless of anatomic location, pin-site infection is one of the main risk factors ranging from cutaneous cellulitis to disseminated systemic infections. The reported rate of infection after the general use of an external fixator has been as high as 80% for superficial infections and as high as 7% for deep infections.9

The current authors reported a superficial infection rate of 19%, with a 0% rate of deep infection for pelvic external fixation. Previous studies have varied on the incidence of infection after definitive pelvic external fixation. Mason et al3 reported an infection rate of 50% for definitive external fixation, whereas Lindhal et al16 observed an overall infection rate of 24% (21% superficial and 3% deep). Burgess et al18 had an incidence of 22% for superficial infections and a range of incidence between 3.4% to 7.1% for deep infections. In addition, Papakostidis et al19 conducted a meta-analysis on pelvic ring fracture treatments and outcomes and reported a range of all types of infection from 0% to 33%, with a mean of 23%.

Overall, 3 (6%) of 52 patients required revision or early removal of their hardware. Thus, of the 10 patients who developed pin-site infections, 7 (70%) were able to maintain their fixation without any revision or early removal. Moreover, half of the patients with infections (5 of 10) were treated with oral antibiotics alone. There were six patients who had extended postoperative oral antibiotics due to specific physician preference, and this small cohort had an infection rate of 12%, which was comparable to the 19% infection rate reported for all patients in the study. This does contribute to an opportunity for confounding; however, when a logistic regression was run with this variable, no statistical significance was noted.

Multiple studies have been conducted examining different approaches to pin-site care for reducing infection rates among patients receiving external fixation. A Cochrane review of 11 studies (572 patients) analyzed the effect of site cleansing compared with no cleansing; sterile antiseptic cleansing compared with sterile non-antiseptic cleansing; sterile cleansing method compared with non-sterile cleansing; dressing compared with no dressing; and comparisons of different types of dressing.11 The authors of this comprehensive review found no statistical difference in the prevalence of infection rates based on these different approaches to pin site care.11 A separate prospective randomized study of 610 pin sites also found no statistical significance in different approaches to pin-site care for reducing infection rates in patients receiving external fixation.8

One additional confounding variable could be the technique of pin placement. All pins placed were predrilled. However, the caliber of drill size used to pre-drill the pin-tract site was variable among surgeons, as was the depth of predrilling. Although this could be an independent confounding variable for loosening and infection, the depth of predrilling in particular would be difficult to control for and thus the current authors believe this variability is generalizable to other surgeons performing this procedure.

A low incidence of persistent LFCN injury (2%) was observed in the current study. This is similar to a previous report by Lindhal et al,16 who observed an incidence of 2% permanent nerve damage postoperatively. The current authors defined this as numbness and/or paresthesia in the distribution of the LFCN as it traverses and arborizes into the anterior and lateral thigh. Care was taken to differentiate this from incisional numbness at the previous pin-tract site. All physical examination evaluations of LFCN injury were confirmed by the attending surgeon and included testing for light touch directly on the patient's skin.

Alternatives to external fixation of anterior pelvic ring injuries include plate fixation, rami screws, and an internal anterior pelvic fixator (INFIX). The INFIX is the most similar to external fixators, with the primary differences being fixation closer to the bone, subcutaneous placement, and use of spine pedicle screws instead of terminally threaded Schanz pins. A main advantages of the INFIX are its subcutaneous placement and that it can be particularly useful for individuals who are obese.20 This technique is effective in treating unstable pelvic ring fractures.21 However, it is not without complications associated with its use including LFCN injury, heterotopic ossification, and femoral nerve palsy.22,23 In addition, a recent biomechanical study demonstrated that the INFIX has equivalent stiffness to traditional external fixation with polyaxial screws, although was stiffer when monoaxial screws were used.24

The main limitation of the current study was its retrospective nature, with its inherent bias. However, the use of logistic regression was included to remove possibilities of confounding variables. Furthermore, the number of patients who had an infection limited the authors' ability to identify risk factors. In addition, most patients did not complete 1 year or more of follow-up, which precludes the analysis of long-term complications of external fixation.

No previous studies have examined whether specific risk factors outside of surgical approach and postoperative care could predispose certain patients to infections. This study was designed to examine which, if any, of these risk factors may contribute to the development of pin-site infection after pelvic external fixation in unstable pelvic ring fractures. The authors did not identify any specific patient characteristics as independent risk factors for pin-site infection and thus conclude that it remains a viable treatment option for all patients. Due to the small number of patients in the current initial cohort who underwent iliac crest pin placement, the authors were unable to examine the risks of iliac crest placement compared with anterior pin placement. An extensive literature review did not yield any data examining this risk factor, and this should be investigated with a large cohort to adequately examine any risks regarding the location of pin placement.

Overall, in the current cohort, the authors found a 19% rate of anterior pelvic external fixation infection. Most pin-site infections can be treated with antibiotics alone with the risk of deep infection remaining low. Patients should be counseled on these risks of pin-site infections, as well as the risks LFCN injury.

References

  1. Naam NH, Brown WH, Hurd R, Burdge RE, Kaminski DL. Major pelvic fractures. Arch Surg. 1983; 118(5):610–616. doi:10.1001/archsurg.1983.01390050076015 [CrossRef]
  2. Poole GV, Ward EF, Muakkassa FF, Hsu HS, Griswold JA, Rhodes RS. Pelvic fracture from major blunt trauma: outcome is determined by associated injuries. Ann Surg. 1991; 213(6):532–538. doi:10.1097/00000658-199106000-00002 [CrossRef]
  3. Mason WT, Khan SN, James CL, Chesser TJ, Ward AJ. Complications of temporary and definitive external fixation of pelvic ring injuries. Injury. 2005; 36(5):599–604. doi:10.1016/j.injury.2004.11.016 [CrossRef]
  4. Sen RK, Gopinathan NR, Tamuk T, Kumar R, Krishnan V, Sament R. Predictors of early outcome in unstable pelvic fractures. Chin J Traumatol. 2013; 16(2):94–98.
  5. Majeed SA. External fixation of the injured pelvis: the functional outcome. J Bone Joint Surg Br. 1990; 72(4):612–614.
  6. Gylling SF, Ward RE, Holcroft JW, Bray TJ, Chapman MW. Immediate external fixation of unstable pelvic fractures. Am J Surg. 1985; 150(6):721–724. doi:10.1016/0002-9610(85)90416-7 [CrossRef]
  7. Riemer BL, Butterfield SL, Diamond DL, et al. Acute mortality associated with injuries to the pelvic ring: the role of early patient mobilization and external fixation. J Trauma. 1993; 35(5):671–675. doi:10.1097/00005373-199311000-00003 [CrossRef]
  8. Cavusoglu AT, Er MS, Inal S, Ozsoy MH, Dincel VE, Sakaogullari A. Pin site care during circular external fixation using two different protocols. J Orthop Trauma. 2009; 23(10):724–730. doi:10.1097/BOT.0b013e3181abbc31 [CrossRef]
  9. Green SA. Complications of external skeletal fixation. Clin Orthop Relat Res. 1983; 180:109–116.
  10. Kellam JF. The role of external fixation in pelvic disruptions. Clin Orthop Relat Res. 1989; 241:66–82.
  11. Lethaby A, Temple J, Santy-Tomlinson J. Pin site care for preventing infections associated with external bone fixators and pins. Cochrane Database Syst Rev.2013; 12:CD004551.
  12. Sisk TD. External fixation: historic review, advantages, disadvantages, complications, and indications. Clin Orthop Relat Res. 1983; 180:15–22.
  13. Stewart MC, Little RE, Highland TR. Osteomyelitis of the ilium secondary to external pelvic fixation. J Trauma. 1986; 26(3):284–286. doi:10.1097/00005373-198603000-00014 [CrossRef]
  14. Parameswaran AD, Roberts CS, Seligson D, Voor M. Pin tract infection with contemporary external fixation: how much of a problem?J Orthop Trauma. 2003; 17(7):503–537. doi:10.1097/00005131-200308000-00005 [CrossRef]
  15. Green SA, Ripley MJ. Chronic osteomyelitis in pin tracks. J Bone Joint Surg Am. 1984; 66(7):1092–1098. doi:10.2106/00004623-198466070-00017 [CrossRef]
  16. Lindahl J, Hirvensalo E, Böstman O, Santavirta S. Failure of reduction with an external fixator in the management of injuries of the pelvic ring: long-term evaluation of 110 patients. J Bone Joint Surg Br. 1999; 81(6):955–962. doi:10.1302/0301-620X.81B6.8571 [CrossRef]
  17. Marsh JL, Slongo TF, Agel J, et al. Fracture and dislocation classification compendium—2007: Orthopaedic Trauma Association classification, database and outcomes committee. J Orthop Trauma. 2007; 21(10) (suppl) :S1–S133. doi:10.1097/00005131-200711101-00001 [CrossRef]
  18. Burgess AR, Eastridge BJ, Young JW, et al. Pelvic ring disruptions: effective classification system and treatment protocols. J Trauma. 1990; 30(7):848–856. doi:10.1097/00005373-199007000-00015 [CrossRef]
  19. Papakostidis C, Kanakaris NK, Kontakis G, Giannoudis PV. Pelvic ring disruptions: treatment modalities and analysis of outcomes. Int Orthop. 2009; 33(2):329–338. doi:10.1007/s00264-008-0555-6 [CrossRef]
  20. Vaidya R, Colen R, Vigdorchik J, Tonnos F, Sethi A. Treatment of unstable pelvic ring injuries with an internal anterior fixator and posterior fixation: initial clinical series. J Orthop Trauma. 2012; 26(1):1–8. doi:10.1097/BOT.0b013e318233b8a7 [CrossRef]
  21. Cole PA, Gauger EM, Anavian J, Ly TV, Morgan RA, Heddings AA. Anterior pelvic external fixator versus subcutaneous internal fixator in the treatment of anterior ring pelvic fractures. J Orthop Trauma. 2012; 26(5):269–277. doi:10.1097/BOT.0b013e3182410577 [CrossRef]
  22. Vaidya R, Kubiak EN, Bergin PF, et al. Complications of anterior subcutaneous internal fixation for unstable pelvis fractures: a multicenter study. Clin Orthop Relat Res. 2012; 470(8):2124–2131. doi:10.1007/s11999-011-2233-z [CrossRef]
  23. Hesse D, Kandmir U, Solberg B, et al. Femoral nerve palsy after pelvic fracture treated with INFIX: a case series. J Orthop Trauma. 2015; 29(3):138–143. doi:10.1097/BOT.0000000000000193 [CrossRef]
  24. Eagan M, Kim H, Manson TT, et al. Internal anterior fixators for pelvic ring injuries: do monaxial pedicle screws provide more stiffness than polyaxial pedicle screws?Injury. 2015; 46(6):996–1000. doi:10.1016/j.injury.2015.01.040 [CrossRef]

Contribution of Different Risk Factors to the Development of Pin-Site Infection Without Consideration of Confounding

FactorInfectionP

Yes (n=10)No (n=42)
Age, mean±SD, y40.8±17.648.5±17.3.233
Length of stay, mean±SD, d23.4±9.523.5±22.7.979
American Society of Anesthesiologists score, mean±SD2.0±0.672.7±0.92.011
Injury Severity Score, mean±SD35.2±14.235.9±13.2.172
Body mass index, mean±SD, kg/m229.7±7.126.3±6.1.182
Sex.068
  Male30%67.9%
  Female70%32.1%
Tobacco use.633
  Yes30%31.8%
  No70%61.9%
Admitted to intensive care unit.325
  Yes50%33.3%
  No50%66.7%

Logistic Regression Results for the Patients Most Likely to Be at Risk for Infection Accounting for Possible Confounding of Other Variables

Potential Risk FactorCoefficientStandard Errorz ScoreP95% Confidence Interval
Age0.0060.0250.26.798−0.043 to 0.056
American Society of Anesthesiologists score0.9120.5341.71.088−0.134 to 1.960
Tobacco use−0.3080.815−0.38.706−1.904 to 1.290
Body mass index−0.0790.057−1.38.167−0.192 to 0.033
Authors

The authors are from the Department of Orthopaedics and Sports Medicine (CM, RF, CK), Harborview Medical Center, University of Washington, Seattle, Washington; and the Department of Orthopedics (MLR), McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, Texas.

Mr McDonald, Dr Routt, and Dr Kleweno have no relevant financial relationships to disclose. Dr Firoozabadi is a paid consultant for Smith & Nephew.

Correspondence should be addressed to: Conor Kleweno, MD, Department of Orthopaedics and Sports Medicine, Harborview Medical Center, University of Washington, 325 9th Ave, Box 359798, Seattle, WA 98104 ( ckleweno@uw.edu).

Received: February 02, 2017
Accepted: July 31, 2017
Posted Online: September 22, 2017

10.3928/01477447-20170918-02

Advertisement

Sign up to receive

Journal E-contents
Advertisement