Abstract
The study describes preliminary experience of the use of external fixators for limb lengthening and deformity correction in combination with flexible intramedullary nailing in management of polyostotic fibrous dysplasia.
Patients and methods
The retrospective study included 8 patients (mean age 11.6 ± 3.38 years; range 7–17 years) with polyostotic fibrous dysplasia operated on using external circular frame and flexible intramedullary nailing. Mean follow-up was 2.6 years. Surgical technique consisted of percutaneous osteotomy of a segment and application of circular external frame. The intramedullary nailing was done using two bent nails. Hydroxyapatite-coated nails were applied in three patients; five patients had titanium nails. Amount of lengthening (cm and %), amount of deformity correction, duration of external fixator use, index of external fixation, “nail/medullary canal at narrowest site” ratio, “nail-medullary canal at osteotomy site” ratio were analyzed. Results and complications were assessed according to Lascombes's classification.
Results
The mean amount of lengthening was 4.5 cm (or 13.7 ± 6.0% per segment). This gave a mean external fixation index of 32.5 ± 13.97 days/cm. The mean ratio of IM nail diameter/medullary canal diameter at the narrowest site was 0.22 ± 0.07 (range, 0.125–0.3 mm). No migration of IM nails into medullary canal were noticed. But in one case there was external migration of Ti-nail. In a year after frame removal, the results of treatment were classified as grade I in 7 cases and IIb in one case.At the latest follow-up control, mechanical axis deviation was found within normal limits in six patients. Two patients had excessive MAD of 11 and 28 mm. In the first case a partial varus deformity recurrence occurred at middle shaft site where a large dysplastic zone was presented. In the second case, a specific shepherd's crook deformity developed and caused excessive MAD. Mean lower limb length discrepancy varied from 1 to 15 mm.
Conclusion
There are advantages of using elastic intramedullary nailing and external fixation in the treatment of limb length discrepancy and deformity of long bones in patients with PFD. This strategy ensures reduced external fixation time and high accuracy of alignment. Intramedullary nails left in situ, especially nails with HA-coating, seem to prevent deformity recurrence and stimulate remodeling in dysplastic fibrous zones.
Keywords: Flexible intramedullary nailing, External fixation, Fibrous dysplasia
1. Introduction
The surgical management of limb length discrepancy and deformity in polyostotic fibrous dysplasia (PFD) is a major challenge.1, 2, 3, 4 Along the varus deformity of proximal femur in monostotic and polyostotic FD, the limb length discrepancy and malalignment represent common findings in PFD requiring surgical intervention. Patients with PFD have underlying bone fragility due to combination of FD, metabolic issues and reduced every-day activity.1,2,5 Furthermore, the new bone formed after corrective osteotomy is dysplastic, thus deformity recurrence should be anticipated. Thus, the use of intramedullary devices left in situ for long time is strongly suggested for all lower extremity reconstructions.6,7 Unfortunately, repeated surgical procedures become less frequent only in adult age.
Limb length discrepancy is common in PFD and is specific for children with severe limb length discrepancy requiring lengthening procedures.1,8 Distraction osteogenesis result in extremely long bone union time due to more dysplastic bone prone to fractures at lengthening site.1,2,8 On the other hand, the weak bone does not ensure stability for external frame for long-time period necessary for lengthening. Theoretically, external fixation index can be reduced using combination of external fixation and rigid intramedullary nailing, but the fibrous zones may interfere with intramedullary nail insertion.8 The majority of FD lesions are richly supplied with blood vessels, and excessive blood loss may occur during preliminary reaming.2
The combination of flexible intramedullary nailing and external fixation in limb lengthening and deformity correction has advantages of enhanced bone formation, reduced time of external frame wearing and prevention of fractures following fixator removal in abnormal bone.9,10 The elastic feature of nails allows progressive correction of deformity with external frame ensuring lengthening and simultaneous anatomical alignment of the mechanical axis. The last has important role in preventing recurrent deformity and fracture in FD.8
The intramedullary nails left in situ in abnormal bone after reconstructive surgery with external fixators reduce the rate of deformity relapse in long-term.11, 12, 13 To the best of our knowledge, the results of elastic nails use in limb reconstruction in FD patients has never been published yet.
In this study we describe our preliminary experience of the use of external fixators for limb lengthening and simultaneous progressive deformity correction in combination with flexible intramedullary nailing in management of PFD.
2. Material and methods
The retrospective study included patients with polyostotic fibrous dysplasia operated on for lower limb length discrepancy and angular and torsional deformity using external circular frame and flexible intramedullary nailing.
The polyostotic fibrous dysplasia was defined as a presence of fibrous dysplasia in more than one skeletal site without extra-skeletal manifestations. The diagnosis has been established confidently on the basis of the medical history, physical examination and radiographs. Radiology revealed specific images of FD: ground-glass appearance, completely radiolucent lesions, or mixed sclerotic and cystic lesions, geographic pattern with sclerotic border, and expanded lesions with a thin shell, associated with bowing, looser zones and thin cortices in all patients.
Criteria of exclusion were monostotic FD, McCune-Albright syndrome, FD with extraskeletal features and Mazabraud syndrome. Subjects with shepherd's crook deformity undergone valgus osteotomies combined with only intramedullary nail were also excluded from the cohort.
Finally, eight patients (3 boys and 5 girls, mean age at time of realignment surgery 11.6 ± 3.38 years; age range 7–17 years) were included in this study. They underwent surgery in the period from 2007 to 2017 in the Ilizarov Scientific Center (Russia) and the Children's Hospital of the Lorraine University Hospital Centre (France). Mean follow-up is 2.6 years.
Four patients underwent previously surgical treatment as resection of dysplastic zone with bone grafting (3 cases) and elastic titanium intramedullary nailing. The first surgery was done at least two years before reconstructive surgery, at age of 4–10 years.
Surgical technique for lengthening and deformity correction consisted of percutaneous osteotomy of a segment and application of circular external frame. The intramedullary nailing was done using two bent nails (titanium or with hydroxyapatite composite coating). The insertion of nails was antegrade for tibial monofocal lengthening, retrograde for femoral lengthening and bipolar ante-retrograde for bifocal lengthening.14 Hydroxyapatite-coated nails with osteoinductive features were applied for intramedullary osteosynthesis in three patients.15 The other five patients had titanium nails. The technique to insert nails does not require preliminary reaming of long bone. No difficulties to pass nails through dysplastic zones were encountered.
In all patients, lengthening and deformity correction were progressive and started on the 5th-8th postoperative day. We never performed acute realignment. Ilizarov frame was used in 7 cases and CORA and ACA guided us for placement of hinges.16 Taylor Spatial Frame was applied in 1 patient where CORA was intergrated as origin (deformity correction reference point) in software-generated frame adjustments schedule.
For each case, these data were recorded: patient age at the onset of lengthening, amount of lengthening (cm and %), amount of deformity correction, duration of external fixator use, index of external fixation, nail-medullary canal at narrowest site ratio, nail-medullary canal at osteotomy site ratio (if applicable).
Results and complications were evaluated according to Lascombes's classification.17 Our major concern was intramedullary nail-related complications. The nail migrations into medullary canal during distraction phase or nail external migration after frame removal were especially searched for.
Preoperatively, after frame removal and at latest follow-up control we analyzed joint orientation angles and malalignment on the full-length standing radiographs of lower limbs: mechanical Lateral Proximal Femoral Angle (mLPFA), mechanical Lateral Distal Femoral Angle (mLDFA), mechanical Medial Proximal Tibial Angle (mMPTA), Lateral Distal Tibial Angle (LDTA), Mechanical Axis Deviation (MAD).16
AtteStat 12.0.5 software was used for the statistical analyses. The statistical values described the mean and standard deviation. This research was approved by the Ilizarov Center Review Board. The study complies with the Declaration of Helsinki statement on medical protocol and ethics. Patients or representatives of all patients enrolled in the study provided oral and written informed consent.
3. Results
The lengthened segment was femur in 4 cases (3 bifocal and 1 monofocal procedures), tibia in 3 cases (bifocal lengthening in all tibial procedures), and in one patient ipsilateral tibia and femur were operated simultaneously (polysegmental lengthening). The mean external fixation time was 118.1 ± 27.7 days. The mean amount of lengthening was 4.5 ± 2.2 cm (or 13.7 ± 6.0% per segment). This gave a mean external fixation index of 32.5 ± 13.97 days/cm. In five cases associated angular deformities have been simultaneously redressed (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5). The mean correction angle was 23.6 ± 13.7°. The Table 1 represents above-mentioned parameters for each patient.
Fig. 1.
Preoperative full-length standing radiographs of lower limbs (AP and lateral views) and photo of a 13-year-old boy.
Fig. 2.
Lengthening of the right femur with Ilizarov frame and HA-coated intramedullary nails, radiographs during lengthening and after frame removal.
Fig. 3.
In a year after frame removal at right femur, normal alignment remains.
Fig. 4.
Acute alignment procedure for left femur, radiographs with Ilizarov frame and after frame removal.
Fig. 5.
Radiographs of lower limbs in 2 years after right femur reconstruction and in 1 year after corrective osteotomy of left femur. Normal alignment of both lower limbs and functional recovery should be highlighted.
Table 1.
Patient demographic and treatment data.
| Patient | Age | Procedure | IM nail | Amount of lengthening; cm | Amount of lengthening; % | Correction; ° | ExFix index; d/cm |
|---|---|---|---|---|---|---|---|
| St. | 13 | Femur bifocal | Ti | 5 | 15.2 | 47 | 29.6 |
| Ka. | 7 | Tibia bifocal | HA-Ti | 3.5 | 14.5 | 20 | 36.3 |
| Sa. | 7 | Femur monofocal | Ti | 3.1 | 10.2 | – | 48 |
| Pe. | 12 | Femur bifocal | HA-Ti | 8 | 18.1 | – | 15.5 |
| Ch. | 11 | Tibia bifocal | Ti | 1 | 3.2 | 15 | 55 |
| Il. | 17 | Femur monofocal + Tibia monofocal | Ti | 7 (4 + 3) | 12.5 + 8.3 | – | 15.6 |
| Ju. | 14 | Femur monofocal | Ti | 3.5 | 17,6 | 13 | 32 |
| Mi. | 12 | Tibia bifocal | HA-Ti | 5 | 23,5 | 23 | 27.8 |
The mean ratio of IM nail diameter/medullary canal diameter at the narrowest site was 0.22 ± 0.07 (range, 0.125–0.3 mm). At osteotomy site the mean ratio was 0.098 ± 0,022 for monofocal lengthening and 0,195 ± 0086 for bifocal lengthening with bipolar sliding FIN.
No migration of IM nails into medullary canal were noticed. But in one case, an external migration with irritation and local sepsis of soft tissues occurred in a patient where titanium nails were used. This complication required IM nail removal in 39 days after frame removal.
Regarding complications and results of treatment in a year after frame removal, they were classified as grade I in 7 cases and IIb in one case.
At the latest follow-up control over 2 years (Table 2), overall alignment in the frontal plane was assessed with mechanical axis deviation (MAD). It was found within normal limits in six patients (range 0–10 mm). Two patients had excessive MAD of 12 and 28 mm corresponding to medial deviation relative to knee joint center. In the first case a partial varus deformity recurrence occurred at middle femoral shaft with large dysplastic zone and resulted in MAD of 12 mm. In the second case, a specific shepherd's crook deformity developed and caused excessive MAD. Regarding alignment of lower limbs, analysis of joint orientation of the knee joint in the frontal plane demonstrated that all children had mLDFA and mMPTA within normal range. Mean lower limb length discrepancy varied from 1 to 15 mm.
Table 2.
Mean radiographic angular parameters, MAD.
| Parameters | Preop | After frame removal | Long-term FU | |
|---|---|---|---|---|
| mLPFA; ° | M | 92.3 | 95.3 | 95.1 |
| range | 43–145 | 46–157 | 48–155 | |
| Me | 100.8 | 93.5 | 94.8 | |
| SD | 31.1 | 32.7 | 31.5 | |
| mLDFA; ° | M | 89.6 | 89.2 | 90.1 |
| range | 82–95 | 88–94 | 88–96 | |
| Me | 89.6 | 89 | 90 | |
| SD | 4.11 | 4.9 | 2.7 | |
| mMPTA; ° | M | 85.9 | 89.6 | 89.9 |
| range | 80–95 | 85–94 | 85–94 | |
| Me | 88.3 | 89.3 | 89.6 | |
| SD | 7.8 | 4.9 | 3.6 | |
| mLDTA; ° | M | 84.9 | 89.1 | 88 |
| range | 78–94 | 84–90 | 84–90 | |
| Me | 85.5 | 89.9 | 88.2 | |
| SD | 5.4 | 4.9 | 4.8 | |
| MAD; mm | M | 16 | 8 | 8.9 |
| range | 6–49 | 0–10 | 0–28 | |
| Me | 9 | 5,7 | 6.3 | |
| SD | 15 | 4.1 | 8.4 | |
In three patients (two cases with HA-Ti nails and one case with Ti nails without osteoinductive coating) we noticed radiological signs of remodeling at dysplastic zone where intramedullary nails were placed. Initially completely radiolucent lesions became mixed sclerotic, newly formed bone tissue appeared in cystic lesions, cortices thickened. The shape of dysplastic sites has had less extended aspect (Fig. 6, Fig. 7).
Fig. 6.
Remodeling of dysplastic FD zones around HA-coated nail: a - AP and lateral view radiographs before IM nail insertion, b – radiographs after frame removal, c – in a year after frame removal, almost total substitution of dysplastic zones.
Fig. 7.
Remodeling of dysplastic FD zones around Ti-nails: a - AP and lateral view radiographs before reconstruction surgery (primary nailing for pathologic fracture), b – radiographs with new inserted nails, combined technique for lengthening and deformity correction, c – in a year after frame removal, subtotal substitution of dysplastic zones: radiolucent lesions became mixed sclerotic, cortices thickened.
4. Discussion
Polyostotic fibrous dysplasia is a rare uncommon skeletal disorder in which bone and bone marrow are replaced by dysplastic fibro-osseous tissues.6,18,19 It arises from postzygotic mutations in the GNAS gene. 20,21
PFD is a complex condition causing deformities, fractures and related walking disability in adults and especially children. 2,7,22 The orthopedic issues requiring reconstructive surgery in patients with PFD are various. The proximal femur is very commonly involved and represents severe varus deformity. Due to fragility and underlying poor regeneration, the use of intramedullary devices for proximal valgus reconstructive osteotomies is strongly suggested.2, 3, 4
In PFD various multiple locations of dysplastic zones beyond the proximal femur, repeated fractures, impending fractures and secondary deformities cause limb length discrepancy and malalignment justifying limb reconstruction procedures aimed bone lengthening and deformity correction.1,2,8
The specificity of PFD imposes high degree of alignment accuracy as remodeling of residual angulation does not typically occur due to formation of dysplastic bone after lengthening.2 The other issue in reconstruction in PFD is represented by weakness and fragility of bone tissue complicating the use of external frame.2
Nevertheless, the bone lengthening in PFD has been the focus of a few studies. Tsuchiya et al. reported 6 cases of lengthening and deformity correction and 5 cases of only alignment procedures using external frames.1 In their lengthening group, the mean external fixation index was 51.1 days/cm. Eralp et al. having experience in limb lengthening in 5 patients with PFD also reported excessive mean external fixation index of 140.4 days/cm.8 Authors of both series emphasize that lengthening and simultaneous alignment of mechanical axis was effective in preventing recurrent angulation.
Eralp et al. suppose that external fixation time could be decreased by combination of external and internal fixation. But they anticipate technical difficulties of reaming and rigid nail inserting into a long bone with fibrous zones.8
We would like to emphasize that use of rigid nailing implies acute deformity correction, and this can interfere with required high accuracy of alignment in conditions of abnormal irregular bone. In contrast to that, the use of elastic intramedullary nails allows progressive deformity correction and simultaneous bone lengthening ensuring accuracy of lower limb alignment.13 The combined technique demonstrated advantage of reduced healing time in lengthening in congenital or acquired discrepancies.14 In our short series of 8 patients, the mean external fixation time was 32.5 days/cm (for a mean amount of lengthening of 4.5 cm) in combined technique application. Comparison of our findings with previously published data revealed significant advantage of combined technique in term of accelerated bone healing.
It should be highlighted, that there were no blocking or internal migration of intramedullary nails in distraction phase for mean “nail diameter/medullary canal diameter at the narrowest site” ratio of 0.22.
The necessity to leave an intramedullary implant in situ after deformity correction of abnormal bone is all-recognized. 11,12,23 This strategy reduces or avoids deformity recurrence in long-term follow-up. In our series alignment remained stable in 6 cases in long-term follow-up. Only in 1 patient we observed a partial varus deformity recurrence at dysplastic zone with intramedullary nail. In one more case, excessive mechanical axis deviation was related to involvement of proximal femur without intramedullary device.
Regarding bone remodeling, no proved conclusion can be drawn on the basis of this small series. But we observed radiologic dysplastic zone substitution with newly formed bone tissue around nails passing through fibrous tissue in three cases.
We suggest applying hydroxyapatite-coated intramedullary nails as their position into bone remained stable in 2 more years after surgery. In only one case of titanium nail application we observed its external migration in postoperative period.
The sample size of our study is relatively small and represents its weakness. The follow-up period should be continued. Further multicenter studies are needed to strengthen the findings and to study the effect of osteoinductive coating on the dysplastic zone remodeling.
5. Conclusion
There are advantages of using combined technique with elastic intramedullary nailing and external fixation in the treatment of limb length discrepancy and deformity of long bones in patients with PFD. This strategy ensures reduced external fixation time and high accuracy of alignment. Intramedullary nails left in situ, especially nails with HA-coating, seem to prevent deformity recurrence and stimulate remodeling in dysplastic fibrous zones.
Contributions
Dmitry Popkov, Arnold Popkov, Anna Aranovich, Pierre Lascombes, Pierre Journeau contributed to the design and implementation of the research, to the analysis of the results and to the writing of the manuscript. Dmitry Popkov, Alexandre Antonov, Pierre Lascombes and Pierre Journeau performed the measurements, were involved in planning and supervised the work, performed the analysis, drafted the manuscript and designed the figures.
Ethical approval
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This publication represents a part of the EPOS scientific committee activity. Also, the authors thank Natalia Popkova for her assistance in preparing the publication.
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