The most common recipient vessel was the posterior tibial artery (n = 27) with its accompanying vein (n = 25). In two cases, the superficial venous system was used for flap drainage by means of the greater saphenous vein (Table 3). Vein grafts were necessary in two patients. Of note, all arterial anastomoses were performed using interrupted 9-0 nylon sutures. Venous anastomoses were typically performed with coupler devices, with the smallest size being 1.5 mm. The mean operative time was 407 minutes (range, 240 to 742 minutes) and the mean estimated blood loss was 273.9 ml (range, 40 to 1550 ml). No significant association between flap type and operative time (p = 0.08) or estimated blood loss (p = 0.78) was noted. Patients were followed postoperatively through a combination of serial clinical examinations and Doppler monitoring. After a 24-hour period of hourly monitoring, the frequency was decreased to every 4 hours until discharge. The postoperative protocol (i.e., dangling protocol) was the same as for adults and consisted of strict extremity elevation for 2 weeks followed by a gradual increase of the duration of extremity dangling during postoperative weeks 3 and 4.
Intraoperative complications were encountered in four patients (10 percent). Revision of the arterial anastomosis was necessary in three patients (7.5 percent) because of intraoperative development of arterial thrombosis. Arterial and venous thrombosis necessitated anastomotic revision of the arterial and venous limb in one patient (2.5 percent). Flow, however, was established in all patients with successful completion of the procedure. No case of intraoperative flap loss was encountered.
Postoperative complications were observed in 10 patients (25 percent). Emergent operative exploration was necessary in four patients (10 percent) because of arterial and venous thrombosis in one (2.5 percent) and three patients (7.5 percent), respectively. Flap loss was noted in two patients (5 percent), thus resulting in a flap survival rate of 95 percent. No significant association between flap loss/complications and patient age (p = 0.34), body mass index (p = 0.52), flap type (p = 0.21), or anatomical location of the defect (p = 0.24) was detected. Although no donor-site complications were encountered, recipient-site complications included pin-site infection (n = 1), delayed wound healing (n = 3), and superficial soft-tissue infection (n = 3) (Table 4). Of note, none of the patients that developed a postoperative infection required surgical intervention.
The mean postoperative length of hospital stay was 12.9 days (range, 4 to 41 days), with patients returning to full weight-bearing after a mean of 2.6 months (range, 1 to 8 months). Secondary procedures were performed in 10 patients (25 percent) and included flap debulking and scar revisions in seven (17.5 percent) and three patients (7.5 percent), respectively.
Subgroup analysis of patients younger than 12 years identified 17 patients with a mean age of 6.4 years (range, 1 to 11 years) and a mean body mass index of 18.8 kg/m2 (range, 15.5 to 31.9 kg/m2). Eleven muscle flaps (latissimus dorsi muscle flap, n = 11) and six fasciocutaneous flaps (parascapular flap, n = 3; anterolateral thigh flap, n = 2; and radial forearm flap, n = 1) were used for reconstruction. No vein grafts were necessary in this subgroup. The mean operative time was 454 minutes (range, 240 to 600 minutes) and the mean estimated blood loss was 115 ml (range, 40 to 250 ml). There were no intraoperative complications. However, emergent operative exploration was necessary in two patients in this subgroup (11.7 percent) because of venous thrombosis. Both flaps were salvaged successfully, with no flap losses being noted in this subgroup of patients. Postoperative complications were noted in two patients and consisted of superficial infection (n = 1) and delayed wound healing (n = 1). Mean length of stay was 10.6 days (range, 4 to 20 days), with a mean time to return to full weight-bearing of 1.9 months (range, 1 to 5 months).
The field of reconstructive microsurgery has undergone a tremendous transformation over the past four decades. The increased use of microsurgical techniques is evidenced by a transition away from being a “last-resort” treatment option as part of the “reconstructive ladder” to a more liberal use as part of the “reconstructive elevator.”18 This transition reflects improved surgical outcomes following microsurgical reconstruction.
Despite these favorable experiences, however, surgeons have been somewhat hesitant to offer free tissue transfer to pediatric patients because of a variety of concerns. Among these are small vessel size and a presumed increased tendency for vasospasm.5–7 In fact, Gilbert felt that a vessel diameter of 0.7 mm was the lower limit of safe vessel size for microsurgical anastomosis.19 This concern was corroborated by Canales et al., who deemed small vessel size to be responsible for two of 13 failed free flaps in their series.20 These reports along with lower flap success rates in pediatric patients, ranging from 55 to 88 percent, cemented the perception of an increased level of difficulty of microsurgical reconstruction in this population.9,10,20
Vessel size or behavior, however, was not found to cause clinically relevant problems in subsequent reports.11,21–23 In fact, it has been hypothesized that the inability of pediatric vessels to spasm is because of an incompletely developed muscularis layer in the vascular wall.21 Furthermore, progressive experience with microsurgical reconstruction in children eventually led not only to reliably high flap success rates, ranging from 95 to 100 percent, but also to the realization that the relative size of perforators and pedicle vessels is, in fact, larger than in adults.11,21,23–27 Our experience echoes these reports, as we found neither vessel size nor tendency to spasm to be a problem intraoperatively. Although we did not measure vessel size in our patients, the vessel dimensions encountered intraoperatively permitted for easy anastomosis.
In light of similar success rates being achieved after microsurgical reconstruction in pediatric and adult patients, one additional aspect specific to pediatric patients is noteworthy, namely, the absence of vasculopathy secondary to longstanding medical conditions such as diabetes mellitus, atherosclerosis, or hypertension. In fact, the absence of any preexisting medical conditions in our patients underscores this important issue. Furthermore, venous insufficiency and the effects of smoking, which may have detrimental effects in adults, are typically not encountered is children.23,28
We therefore believe that vessel size should not represent a critical parameter in the decision-making process anymore. The advent of supermicrosurgical techniques and increased knowledge of flap anatomy and physiology have even made perforator-based pediatric lower extremity reconstruction using the free-style approach a reliable mode of reconstruction.29 Successful free flap transfer in infants as young as 10 to 15 weeks has been reported.30,31
Similar to lower extremity reconstruction in adults, posttraumatic defects represent a distinct clinical entity that is associated with an increased level of difficulty because of the unpredictable extent of vascular injury and distorted anatomy. Ensuring that soft and pliable vessels without evidence of traumatic injury are chosen as recipient vessels is therefore a much more critical factor for reconstructive success than vessel size. The most common recipient vessel used in the present study was the posterior tibial bundle. This is not surprising, as the posterior tibial vessels are much less susceptible to trauma because of their rather deep location in the lower leg. In contrast, a much higher incidence of vascular damage to the anterior tibial artery has been reported,2 an observation corroborated by our study findings given that the anterior tibial vessels were used in only 20 percent of cases.
The absence of preexisting medical conditions not only facilitates microsurgical anastomosis because of the presence of pristine vessels but is also believed to be responsible for the lower rate of donor-site complications seen in pediatric patients.27 The absence of donor-site complications noted in the present study echoes findings of previous reports.26,28
A commonly discussed aspect of pediatric lower extremity reconstruction is flap choice. The most commonly used flap in our patient population was the latissimus dorsi muscle flap. This is not surprising in light of the fact that the latissimus dorsi muscle and rectus abdominis muscle flaps are reported to be the most commonly used vehicles in pediatric microsurgical reconstruction.9,12,27,32 Reasons include consistent anatomy and familiarity with flap harvest. As with adult reconstruction, however, the focus has switched from flap survival to concerns related to donor-site morbidity in the pediatric population. A change in flap choice in pediatric reconstruction parallels this trend, with fasciocutaneous and perforator-based flaps being increasingly advocated.22,26,29 Our practice reflects this trend given the more frequent use of fasciocutaneous flaps (Figs. 1 and 2). An additional advantage of fasciocutaneous flaps is that they facilitate secondary procedures, such as secondary bone grafting. Although this practice may be associated with an increased rate of secondary debulking procedures, ranging from 17.5 percent in the present study to 36.4 percent as reported by Acar et al., we believe that it ultimately is in the patients’ best interest, as problems such as the functional contraction that is occasionally seen after free muscle transfer are not seen with fasciocutaneous flaps.17,27
As discussed, most clinical studies focusing on microsurgical reconstruction in children are characterized by significant heterogeneity regarding defect location and defect cause, thus making it rather difficult to draw conclusions regarding distinct patient populations, such as patients presenting with traumatic lower extremity defects.4,13,14,33 Although surgical outcomes of pediatric patients undergoing reconstruction of traumatic lower extremity defects are presented in several clinical studies, few reports have focused exclusively on microsurgical reconstruction of traumatic lower extremity defects in children.5,8,9,17 Given the rare occurrence of pediatric lower extremity trauma mandating free flap transfer, it is not surprising that the study population in these reports is rather small, ranging from 11 to 42 patients.5,17 Thus, our experience of 40 patients is among the largest reported series to date. With a flap success rate of 95 percent that compares favorably with reported flap loss rates ranging from 5.5 to 12 percent,8,9 and a postoperative complication rate of 25 percent that is lower than reported rates of up to 62 percent,9 we firmly believe that the contemporary reconstructive microsurgeon should not be concerned about offering microsurgical reconstruction to pediatric patients.
In summary, posttraumatic lower extremity defects in the pediatric population should be approached in a similar analytical manner as in adults, consisting of a thorough analysis of the defect followed by determination of an appropriate reconstructive plan. Concerns related to age, vessel size, or vessel behavior should not factor in to the equation. Microsurgical reconstruction of traumatic lower extremity defects in the pediatric population is safe, as evidenced by a flap survival rate of 95 percent. Furthermore, donor-site complications seem to be lower than rates reported in adults. We now favor fasciocutaneous over muscle flaps given their lower functional donor-site morbidity, ease of secondary procedures, and ability to prevent the development of functional contractures.
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