Long-term follow-up on the use of vascularized fibular graft for the treatment of congenital pseudarthrosis of the tibia

Congenital pseudoarthrosis of the tibia (CPT) is one of the most difficult conditions to treat. The natural history is persistent instability and progressive deformity [1, 2]. CPT is known to accompany NF1 (neurofibromatosis type 1), also called von Recklinghausen disease. Treatment options vary, including both surgical and non-surgical approaches. Surgical techniques of vascularized fibular grafting (VFG), intramedullary stabilization and external fixation have been reported to be relatively successful in the treatment of CPT [3–9].

We previously reported the cases of 5 patients with CPT for whom good short-term results were obtained with the use of VFG [3]. However, long-term follow-up studies of VFG, particularly identifying limb-length discrepancy, residual angular deformity and the rates of refracture are necessary. All of those complications can compromise the functional outcome, even though pseudarthrosis may demonstrate bone consolidation [2, 10]. In this study, the long-term results of VFG were evaluated for 5 previously reported cases and for an additional 3 cases. We specifically emphasize a comparison between patients undergoing multiple operations and those with no prior surgery before VFG. The previous surgerical procedures were in the current series were all intramedullary stabilization with/without bone grafting, which was not accompanied by any method of microvascular bone transplantation.

Multiple previous operations had been performed before VFG in 5 patients in other institutions prior to attending our hospital. We have reported these patients in a study of short-term follow-up [3]. For these patients, the number of operations ranged from 3 to 8, the average number being 3.4. The previous surgical treatments were all utilizing intramedullary nails with/without bone grafting. The other 3 patients were added for the purpose of the current study, and they had undergone no previous treatments. We analyzed the term of bone consolidation, and complications comprising leg-length discrepancy, tibial deformity of angulation, occurrence of fractures and existence of ankle pain, in a comparison between patients with and without previous surgical treatment before VFG. Bone consolidation was analyzed by skilled orthopedic surgeons including some of the authors.

In a series of VFG for the treatment of CPT, bone consolidation was reported to be obtained in 94% of cases [4]. In the current study, all cases with VFG obtained bone consolidation, with an average bone consolidation term of 6.6 months without recurrence. In a previous report, gender may have been a significant factor in the length of term needed for bone consolidation, on the basis that 13 boys had an average bone consolidation term of 13 months, whereas 16 girls had an average bone consolidation term of 9 months [2]. In the current case, such a tendency was not observed. In our institute, because of good results of bone consolidation after VFG, VFG has been chosen as the primary treatment, with the Ilizarov bone transport method being an alternative choice. In a previous report, the Ilizarov bone transport method was reported as being useful in achieving primary healing in CPT, but complications of refracture and postoperative deformities may occur [11]. Further examination of long-term follow-up after the Ilizarov bone transport method is necessary.

As for VFG, it has been reported that age is an important factor in the result of VFG, with regard to bone consolidation. In a previous report, seven patients operated on at 10 years of age or older had successful outcomes, compared with 12 out of 22 who were 9 years of age or younger at the time of surgery [12]. According to the EPOS (European Paediatric Orthopaedic Society) Multicenter Study [6], there was a clear correlation between age at surgery and final outcome, with better results being achieved with increasing age. Therefore, it has been proposed that surgery should not be performed on patients younger than the age of 3 years and it is recommended that surgery be postponed until the age of 5 years [6]. Another study about bone consolidation in CPT also suggested that the best age for rapid bone consolidation is 3.5 years to 7.5 years old [4]. In the current study, one case aged 1.9 years old did not obtain bone consolidation with VFG. For that case, a second contralateral VFG was successful at the age of 7.3 years old. This fact may support the notion that an age younger than 3 or 3.5 years old is a negative factor with regard to bone consolidation in VFG.

Tibial deformities of limb-length discrepancy and angulation are common after treatment for CPT [2, 4]. Bone consolidation of pseudarthrosis is not sufficient for assessment as the end result. Occasionally, chronic lower-extremity dysfunction and clinical symptoms may result in amputation [7]. In the current series, a limb-length discrepancy of more than 5 cm was seen in 4 out of the 5 cases undergoing multiple operations but in none of the 3 cases with no prior surgery. The average leg-length discrepancy for the cases undergoing multiple operations was 7.5 cm, while that of cases with no prior surgery was 0.7 cm. The p value is 0.07, and the reason for there being no significant difference statistically may be because of the small number of these cases. Limb-length discrepancy has been reported in half the patients with intramedullary nails [7]. Such surgical procedures with a potential danger of damaging the growth plate may result in limb-length discrepancy. Therefore, the deformity may have been related to an earlier surgical procedure prior to VFG [12].

Angular deformities do not remodel and are often progressive after VFG [5, 13]. In the current study, a deformity of more than 20 degrees was seen in 4 out of the 8 cases. The relationship between the degree of angulation and multiple operations before VFG is not clear. Ankle pain was seen in 3 out of 8 cases. It seemed characteristic that these pains appeared long after the VFG (mean, 10.6 years), and late in the second decade (mean, 18.3 years old). These 3 cases had undergone multiple operations. Therefore, it should perhaps be noted that there was a tendency for previous unoperated cases to have ankle pain at long-term follow-up, even though there had been no pain of short-term follow-up. In a previous report, ankle pain after the surgical procedure for VFG is associated with multiple operations utilizing intramedullary nails, consistent with our results [14], and degenerative changes in the ankle because of the ankle valgus deformity and the intramedullary rod passing through the ankle joint is considered to be the cause of the ankle pain [14–16]. Refracture is not uncommon following consolidation of VFG [13, 17, 18]. In most cases, the first fracture is reported to occur before the age of 1 year [4]. In the current case, one out of the 8 cases had a stress fracture at the age of 7.4 years old, and casting healed the fracture.

In conclusion, the overall long-term follow-up results of VFG were excellent. However, residual limb-length discrepancy and ankle pain were prominent in cases undergoing multiple operations. In contrast, patients who underwent VFG as a primary operation had fewer such problems. Accordingly, VFG should be considered as a primary treatment option for CPT.