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Original Article |
1 Orthopaedic Surgery Service, Department of Surgery, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10021
2 Plastic Surgery Service, Department of Surgery, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10021
Correspondence: Address correspondence and reprint requests to: John H. Healey, MD; E-mail: healeyj{at}mskcc.org
| ABSTRACT |
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Methods: We present a series of 32 patients who underwent this procedure to reconstruct an extremity in our institution. There were 12 children and 20 adults.
Results: The residual distal fibula was significantly longer in adults as compared with children (P < .048). Among children, 3 of 11 undergoing the procedure developed ankle instability, in distinction to adults, none of whom developed this complication (P < .041). This reflects a disruption of normal ankle function that develops in skeletally immature patients with a short residual fibula but not in patients with a longer residual fibula (P < .008). When the sum of patient age in years and residual fibula length in centimeters was less than 16, 3 of 6 patients developed deformity, in contrast to no deformity developing in the remaining 23 when the sum was >16 (P < .004). Adults were more likely to develop pain than instability.
Conclusions: Our series suggests that children with an age-length sum <16 should be considered for prophylactic tibiofibular synostosis creation.
Key Words: Vascularized fibular graft Ankle instability Orthopedic tumors Children
| INTRODUCTION |
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The group involving tumors is characterized by certain specific features. Bone tumors occur frequently in children. Children are prone to secondary changes that result from removal of the fibula, including valgus deformity.1214 Children, being of small stature, have less tissue for donation, and the residual fibula is typically very small. This would potentially result in relatively greater ankle instability than in adults.
Few publications address this issue in the younger population.15,16 We believe that this is the largest series of its kind to date.1719 Only one other series has dealt with the specific clinical situation of vascularized fibula grafts to reconstruct defects from extremity tumor resections.20 In that series, patients were generally older, and ankle complications were not found. Additionally, a study on donor site morbidity highlighted the occurrence of ankle symptoms and gait analysis changes.21 These were all adults and, again, did not show ankle instability. In the largest known series on vascularized fibular grafts used to reconstruct defects in children left from resections of congenital pseudoarthrosis of the tibia,22 prophylactic donor site tibiofibular stabilization was performed in all donor ankles. Consequently, only one case of valgus ankle instability resulted. More recently, other studies have been conducted to attempt to quantify the risk of developing ankle instability at the donor site after a vascularized fibular graft procedure.2328 These studies provide compelling evidence for the occurrence of this complication after the procedure. However, because age and the degree of skeletal maturity were not well characterized, it is difficult to draw conclusions on the risk factors for development of ankle instability. We sought to compare the prevalence of ankle instability in children with that in adults and to formulate a treatment algorithm given the results of this study and the available literature on the pathogenesis of valgus ankle deformity after vascularized fibular harvest.
| METHODS |
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| RESULTS |
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Nine patients developed ankle complications. Six patients developed chronic pain that was self limiting. Three patients developed valgus ankle instability. There were four male and five female patients in this group, with an age range of 6 to 49 years. The more severe cases involving deformities occurred in patients in the younger age group. There were three cases of osteogenic sarcoma, two Ewings tumors, two giant cell tumors, one desmoid tumor, and one patient with chondrosarcoma. Patients without ankle donor site complications had the analogous distribution of diagnoses.
There were 12 children in this population1 died within a year of surgery, 1 had pain, and 3 developed ankle instability. Three of 11 children, as opposed to no adults, undergoing the procedure developed ankle instability. They were first noted to have ankle instability an average of 27.3 months (range, 2038 months) after their surgical procedures. Two of these required corrective surgery in the form of a fibular osteotomy and lengthening and tibiofibular synostosis. The incidence of ankle instability was significantly higher among children as compared with adults as assessed by Fishers exact test (P < .041).
Patients who developed valgus instability were younger, with a mean age of 7.6 years (6, 7, and 10 years), as compared with those without instability (P < .000004), with a mean age of 29 years (range, 574 years). Among all children, this trend continued, with younger patients (mean age, 7.6 years; range, 610 years) developing instability and older children (mean, 9.8 years; range, 514 years) remaining stable (P < .28).
There was a significant association between ankle instability and residual fibula lengths. Patients with instability had mean residual fibula lengths of 6 cm (range, 57 cm), as opposed to those without instability (P < .008), with a residual length of 8.9 cm (range, 4.515 cm). Among all children, patients with unstable ankles had mean remnant distal fibula lengths of 6 cm (range, 57 cm), and those with stable ankles had mean lengths of 7.9 cm (range, 4.515 cm). This was not statistically significant (P < .16). Patients with residual fibula lengths of <7 cm had a greater tendency to develop instability in the ankle (P < .078).
This apparent relationship between age (and, hence, future growth), residual fibular length, and the frequency of valgus deformity was further investigated with an index incorporating age in years and length in centimeters (distal fibular donor index). When the sum of age and length was <16, then 3 of 6 patients developed deformity; when this was
16, none of the remaining 23 developed deformity (P < .004).
There was no significant association between harvested donor fibula lengths and instability. Donor fibula lengths among patients with instability (mean, 15.6 cm; range, 1319 cm) were not significantly different (P < .77) from those without instability (mean, 16.3 cm; range, 7.727 cm). Among all children, donor fibula lengths were not significantly different (P < .66) between those without instability (mean, 16.7 cm; range, 1427 cm) and those with instability (mean, 15.6 cm; range, 1319 cm).
Six patients developed pain without deformity (one child and five adults). The one child with pain had sustained a Salter-Harris type II fracture of the distal tibia. The patient was noted to be osteoporotic in the area, and this was ascribed to the chemotherapy the patient underwent for treatment of her osteogenic sarcoma. This was treated in a cast and resolved without incident. The other five patients were all adults. These experienced pain generally as aches in the calves. These were self-limiting and lasted on average 7.4 months from the time of surgery (range, 319 months). For purposes of statistical analysis of pain, this childs pain was not considered representative of the kind of pain the adults felt and was excluded from subsequent assessment.
Patients who developed pain without deformity tended to be older. Although all patients with pain without deformity were adults, this relationship was not significant (P < .13). These had a mean age of 33 years (range, 2049 years), as compared with those without pain (P < .30), who had a mean age of 26 years (range, 574 years).
There was a significant association between residual fibula lengths and pain. Patients with residual fibula lengths of >7 cm were more likely to develop pain in the ankle (P < .05). Patients with pain had mean residual fibula lengths of 10.2 cm (range, 815 cm), as opposed to those without pain (P < .21), who had residual lengths of 8.3 cm (range, 4.515 cm). Among all adults, patients with painful ankles had mean remnant distal fibula lengths of 10.2 cm (range, 815 cm), and those without pain had mean lengths of 9.0 cm (range, 615 cm). This was not statistically significant (P < .45).
Similarly, donor fibula length among patients with pain (mean, 13.5 cm; range, 7.720 cm) was not significantly different (P < .22) from that of those without pain (mean, 16.8 cm; range, 1127 cm). Among all adults, donor fibula lengths were not significantly different (P < .20) between those without pain (mean, 17 cm; range, 1126 cm) and those with pain (mean, 13.5 cm; range, 7.720 cm).
Radiological data were available in the three patients with valgus instability. Figures 2a
, 3a
, and 4c
show lateral tibial plafond valgus distortions of 28°, 38°, and 38°, respectively. Talar tilt measured 3°, 13°, and 2°, respectively. There was corresponding distortion of the ankle mortise. Consequently, there was a tendency for the ankles to deform in the direction of valgus and external rotation. This was not seen in stable ankles. Two patients underwent tibiofibular synostosis procedures and functioned well afterward, as shown in Figs. 2b
and 3b
. They both developed stable ankles without pain and had full activity after the procedure. The third patient is presently under observation (Fig. 4
).
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| DISCUSSION |
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In our series, it was found that harvested donor fibular lengths were not significantly different between adults and children. The length of the residual fibula was, however, significantly longer in adults as compared with children (P < .048). Hence, the grafts, although not absolutely different, were relatively longer in children than in adults, with their attendant morbidity.
As many as 27% of children undergoing the procedure are at risk of developing ankle instability, as opposed to adults, who are at virtually no risk of developing this complication (P < .041). This is a reflection of the disruption of the normal ankle articulation that develops in skeletally immature patients with short residual fibulae but not in older patients or those with longer residual fibulae (P < .008). Patients who lack this lateral post are believed to be at increased risk of developing this deformity.26,37 That said, a review of the data in Table 1
shows that of the children in this series, three of eight with residual fibular lengths of
7 cm, two of six with lengths of <6 cm, and one of three with lengths <5 cm developed this complication. The absence of a strong direct relationship may be an artifact of the sample size, yet it suggests that other factors are involved in the pathogenesis of ankle instability. The simple sum of patient age and residual fibular length being <16 had the highest correlation with the development of deformity (P < .004).
The deformities noted were proximal migration of the fibula, anteromedial rotation of the proximal part of the remnant distal fibula, impaction of this tip onto the tibial diaphysis, and lateral tibial physeal lysis, as shown in Fig. 5
. There was also a suggestion of anteromedial arrest of the distal fibular physis. Ankle instability has not been demonstrated in adults after a vascularized fibular graft procedure. This is probably because of the limited potential for remodeling in the adult metaphysis. This is supported by a recent study that suggests that in adults, only 10% of the fibula length is needed distally to maintain stability.38 Children naturally have greater ligamentous laxity than adults. This would allow more instability than would otherwise be possible with the stiffer ligaments seen in adults. This instability could conceivably result in increased pressure and, ultimately, necrosis of the lateral tibial growth plate, as demonstrated in Fig. 5
. The valgus instability therefore evolves into a permanent deformity because of the relative overgrowth of the medial versus the lateral tibial physis. In addition, because of the propensity to develop the secondary changes demonstrated here in the talar dome, this is likely to evolve into a permanent state of valgus deformity in adulthood.26
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Pain as a complication has been described in the past.25,3941 In our series, this was a self-limiting phenomenon. Although pain occurred more frequently in adults, this trend was not significant. What was interesting was that pain occurred in patients in whom residual fibular lengths were >7 cm (P < .05). This suggests that the pain is not related to ankle instability, where, conceivably, residual fibular lengths should be shorter. Similar series on donor site morbidity show similar complications in adult tumor cases reconstructed with vascularized fibular grafts.42 This complication has been recorded up to 2 to 7 years after the procedure. In our series, the patients had pain for 3 to 19 months after the procedure.
In conclusion, the vascularized fibular graft is a key tool for the orthopedic oncologist and may need to be used in children, in whom bone tumors are more common and for whom biological reconstructive measures are preferred. Although excessive shortening of the remnant distal fibula during this procedure is not desirable, it may not be avoidable, given the requirements of the specific reconstructions. The vascularized fibular graft is a double-edged swordthis should be considered before surgery. A primary synostosis of the distal tibia and fibula might be advisable for patients when the sum of age and residual fibular lengths is <16. Otherwise, radiological and clinical surveillance is suggested for early diagnosis.
| FOOTNOTES |
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Received for publication March 15, 2004. Accepted for publication September 20, 2004.
| REFERENCES |
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This article has been cited by other articles:
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M. Ghert, N. Colterjohn, and M. Manfrini The Use of Free Vascularized Fibular Grafts in Skeletal Reconstruction for Bone Tumors in Children J. Am. Acad. Ortho. Surg., October 1, 2007; 15(10): 577 - 587. [Abstract] [Full Text] [PDF] |
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