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Prophylactic Bypass Grafting and Long-Term Bracing in the Management of Anterolateral Bowing of the Tibia and Neurofibromatosis-1
Onder Ofluoglu, MD1; Richard S. Davidson, MDb; John P. Dormans, MDb
1 Lütfi Kirdar Egitim ve Arastirma Hastanesi, 2. Ortopedi ve Travmatoloji Klinigi, Denizer Cad. E-5 Karayolu Cevizli, Istanbul 34890, Turkey. E-mail address: oofluoglu@gmail.com
b Department of Orthopaedic Surgery, The Children's Hospital of Philadelphia, 34th and Civic Center Boulevard, 2nd Floor, Wood Building, Philadelphia, PA 19104-4399. E-mail address for R.S. Davidson: davidson.richard.s@gmail.com. E-mail address for J.P. Dormans: dormans@email.chop.edu
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Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
Investigation performed at the Department of Orthopaedic Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania

The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2008 Oct 01;90(10):2126-2134. doi: 10.2106/JBJS.G.00272
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Abstract

Background: Congenital anterolateral bowing of the tibia is a pre-pseudarthrosis stage of congenital pseudarthrosis of the tibia and is associated with a substantial risk of fracture and pseudarthrosis. We evaluated the results of prophylactic bypass grafting performed in combination with bracing to prevent fracture and pseudarthrosis.

Methods: This retrospective series included ten patients with pre-pseudarthrosis of the tibia treated, between 1991 and 2002, with prophylactic bypass grafting with an allograft fibula placed posteromedially in a stress-bearing fashion. The average patient age was 2.3 years at the time of diagnosis, 3.6 years at the time of surgery, and ten years at the time of final follow-up. The mean duration of follow-up was seventy-eight months. Brace protection was recommended at the time of diagnosis and was continued after the operation until maturity. Despite the bracing, a low-energy fracture developed and partially healed prior to the bypass grafting in one patient. The remaining nine patients had no fractures prior to the bypass grafting. At the time of final follow-up, the patients were examined clinically and radiographically for the presence of a fracture or pseudarthrosis and for residual deformity, including malalignment, ankle and knee joint abnormalities, and leg length discrepancy.

Results: No patient had either a fracture or a pseudarthrosis of the tibia at the time of follow-up. All grafts united to the tibia at both ends. Complications included an allograft fracture in three patients, which healed in all; allograft resorption in one patient; and pseudarthrosis of the ipsilateral host fibula in one patient. At the time of final follow-up, a mean of 9 mm (range, 0 to 37 mm) of leg length discrepancy was found. A corrective osteotomy was done for four patients (three because of ankle valgus and one because of diaphyseal deformity).

Conclusions: In this small series of ten patients with congenital anterolateral bowing of the tibia treated with bypass strut grafting and long-term bracing, there were no cases of pseudarthrosis of the tibia. Distal tibial deformity may persist throughout the growth period and require operative correction in patients treated with this procedure.

Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

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    References

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Richard S Davidson, MD
    Posted on November 22, 2008
    Dr. Davidson and colleagures respond to Dr. El-Rosasy
    ChildrenÂ’s Hospital of Philadelphia

    We thanks Dr. El-Rosasy for raising certain questions regarding our paper (1).

    While Dr El-Rosasy is correct that Lloyd-Roberts stated in his introduction that “the results were not wholly satisfactory” a reading of the entire paper is warranted. Lloyd-Roberts’s comment referred to his overall experience with this rare condition and not his reported three cases with strut grafting.[2] Lloyd-Roberts reported seven patients. In the first four, two were not treated and went on to fracture and pseudoarthrosis. The third fractured while waiting for the grafting operation. The fourth was treated only with tibial graft “shavings” and not a strut graft. Only three of the seven cases were treated with strut grafting and all three of these went on to heal without development of fracture or pseudoarthrosis, leading him to conclude that, “We believe this operation to be justified….”. In his conclusion, Lloyd-Roberts states that “1. The danger of fracture and subsequent pseudoarthrosis is emphasized…. And 2. With the object of preventing fracture, early and urgent bone grafting is advocated.” [2]

    Dr. El-Rosasy states in his letter that in a review of the English literature there are “several reports of patients with congenital tibial dysplasia who not only did not develop fractures, but in whom the tibia became nearly normal….” However, he fails to discuss the type of deformity. While he refers to an editorial by Nicoll published in 1965 in which Dr Nicoll states that the bypass technique has not been “proven to be truly prophylactic”(3) he failed to comment on one of the main points of the editorial which is summarized by the quote, “one outstanding lesson…that there are at least two types with totally different patterns of behavior ranging from relatively benign at one end to exceedingly vicious at the other.” While there are some reports in the literature that the rare Crawford type 1 congenital tibial dysplasia (CDT) may not fracture and may even remodel, these do not constitute any long term evidence involving a large series of similar patients. This issue was discussed in our paper. [1]

    Only two of the patients reported in our study were type 1; the rest were type 2. Moreover, one of our two type 1 patients developed a stress fracture and the other developed a fibular pseudoarthrosis prior to bypass grafting. We considered both of these patients as being at higher risk for fracture. It has been well reported in the literature that Crawford type 2 tibias carry a high risk of developing fractures and subsequent pseudoarthroses. We disagree with the implication that it is "an ethical issue" to try to prevent an at-risk group of patients from progressing to that risk is faulty reasoning. This is particularly true in light of the complexity of, difficulty and complications associated with the treatment of pseudoarthrosis.

    Dr. El-Rosasy is not correct in stating that we “described a technique identical to the bypass grafting described by McFarland”. Not only are there many technical differences between the techniques, but McFarland applied his technique to existing pseudoarthroses while none of our patients had a pseudoarthrosis of the tibia.[4] Dr. El-Rosasy goes on to state that McFarland “believed that the cause of persistence of the pseudarthrosis must be mechanical due to angulation and the bending stresses of muscles.” A careful reading of McFarland’s paper, however shows that he was acutely aware of a biologic component, i.e. that a “defect exists in the shaft of the tibia…” [4]

    Dr. El-Rosasy referrred to a paper written by Morrissy et al [5] to state that “there are reports that prove that congenital pseudoarthrosis of the tibia is a biological defect.” To quote from Morrissy’s paper “It is felt that congenital pseudoarthrosis of the tibia is a biological problem and not merely a mechanical one.” A thorough review of the literature confirms that prevailing opinion suggests a combination of biological and mechanical factors. Importantly, neither of these issues either proves or disproves the idea that mechanical support with bypass grafting can reduce the risk of pseudoarthrosis in CDT.

    Dr. El-Rosasy then states that “the current best treatment depends on the type of dysplasia…” but then asserts that “For a dysplastic tibia without fracture, no surgery is justified and the limb should be protected in a removable brace….” This assertion is made without reference to the type of “dysplastic tibia without fracture,” or reference to the many papers noting the high risk of fracture in Crawford type 2. [6,7,8]

    Dr. El-Rosasy then suggests that all congenital dysplasia of the tibia without fracture can be treated by bracing alone without any reference to any study. To our knowledge, there is not one large, long- term study showing this. As noted in our study, we have seen many of our patients with congenital dysplasia of the tibia sustain a fracture and progress to pseudoarthrosis. Our patients fractured while wearing recommended bracing, while bathing out of the brace, and even while walking without the brace at home. Our paper asserts all of this. Indeed, we would welcome a study of "long-term bracing" of the different Crawford types of congenital dysplasia of the tibia associated with neurofibromatosis. However, until a large long-term study of brace treatment of the various types of congenital dysplasia of the tibia demonstrates that bracing alone is successful in preventing progression to pseudoarthrosis in these patients, Dr. El-Rosasy’s statement "…no surgery is justified …" is itself unjustified.

    Dr El-Rosasy’s opinion that, “The development of better fixation methods” has nothing to do with the risk of pseudoarthrosis. Dr. El- Rosasy even states in his letter that, "the limb should be protected…until skeletal maturity when the deformity can be safely corrected”. In our experience and as documented in the literature, CDT can go on to fracture and pseudoarthrosis with bracing, which cannot be worn 24hours per day, seven days per week. The bypass grafting was instituted as an easy surgical procedure providing a permanent internal splint in order to avoid the more difficult and complicated treatment of pseudoarthrosis.

    Once pseudoarthrosis of the tibia occurs, healing is difficult to achieve. Complications, shortening, and deformity, are common . [9,10] One recent paper reported that pseudoarthrosis was ultimately resulted with amputation in one in four of the cases. [11] While substantial limb length discrepancy is common with pseudoarthrosis, our patients who underwent the bypass grafting had a discrepancy of less than 9 mm. All of these points are addressed in our paper. It is our belief that surgical treatment is appropriate given the natural history and rate of complications associated with other forms of treatment after established pseudarthrosis.

    Although our study is one of the largest of its kind for this rare dysplasia, the numbers are, as noted in our paper,too small for many conclusions that reach statistical significance. None of the patients in our study sustained a fracture, developed a pseudoarthrosis or required the extensive surgical procedure and complications from treatment of pseudoarthrosis. Our paper suggests that thr bypass grafting method can be a means of reducing fracture and pseudoarthrosis.

    Finally, the last sentence of the Dr. El-Rosasy’s letter states, "For a pseudoarthrotic tibia, a biological solution should be adopted including intramedullary fixation to maintain a straight leg and lessen refractures" makes reference to established pseudoarthroses. Therefore, it has no relation to the situation described in our paper, which relates to dysplastic tibias which have not gone on to pseudoarthrosis. Dr. El-Rosasy’s references to his own review chapter in his letter provide insight into his opinions, and contain references to original studies and data. In the conclusion to his chapter, Dr. El-Rosasy speculates that future investigations should focus on “modalities that locally stimulate osteogenesis and bone repair.” [12] We believe that this is precisely what the bypass grafting described in our paper appears to be doing. The graft is incorporated into the tibia, realigning the mechanical forces, strengthening the tibia and reducing the risk of fracture and pseudoarthrosis. While future treatments may permit “biologic cure” of the disease which causes CDT, the closest current biological and mechanical option for treatment is what was presented in our paper, that is, structural bypass grafting.

    References

    1.Onder Ofluoglu, Richard S. Davidson, and John P. Dormans Prophylactic Bypass Grafting and Long-Term Bracing in the Management of Anterolateral Bowing of the Tibia and Neurofibromatosis-1 J Bone Joint Surg Am 2008; 90: 2126-213.

    2. Lloyd-Roberts GC, Shaw NE. The prevention of pseudarthrosis in congenital kyphosis of the tibia. J Bone Joint Surg Br. 1969 Feb 1;51(1):100-5.

    3. Nicoll EA. Infantile pseudarthrosis of the tibia. J Bone Joint Surg Br. 1969 Nov;51(4):589-92.

    4. McFarland B. Pseudarthrosis of the tibia in childhood. J Bone Joint Surg Br. 1951 Feb;33-B(1):36-46.

    5. Morrissy RT, Riseborough EJ, Hall JE. Congenital pseudarthrosis of the tibia. J Bone Joint Surg Br. 1981;63-B(3):367-75.

    6. Crawford AH Jr, Bagamery N. Osseous manifestations of neurofibromatosis in childhood. J Pediatr Orthop 1986;6:72-88.

    7. Hardinge K. Congenital anterolateral bowing of the tibia. The significance of the different types in relation to pseudoarthrosis. Ann R Coll Surg Engl. 1972;51:17-30.

    8. Lehman WB, Atar D, Feldman DS, Gordon JC, Grant AD. Congenital pseudoarthrosis of the tibia. J Pediatr Orthop B 2000;9:103-7.

    9. Boero S, Catagni M, Donzelli O, Facchini R, Frediani PV Congenital pseudarthrosis of the tibia associated with neurofibromatosis-1: treatment with Ilizarov's device J Pediatr Orthop. 1997 Sep-Oct;17(5):675-8.

    10. Paley D, Catagni M, Argnani F, Prevot J, Bell D, Armstrong P. Treatment of congenital pseudoarthrosis of the tibia using the Ilizarov technique. Clin Orthop Relat Res. 1992 Jul;(280):81-93.

    11. Dobbs MB, Rich MM, Gordon JE, Szymanski DA, Schoenecker PL.Use of an intramedullary rod for treatment of congenital pseudarthrosis of the tibia. A long-term follow-up study. J Bone Joint Surg Am. 2004 Jun;86-A(6):1186-97.

    12. El-Rosasy MA, Paley D, Herzenberg JE. congenital pseudarthrosis of the tibia. in Limb Lengthening and Reconstruction. Chapter 34, pages 485-495. Editors; S.R. Rozbruch and S. Ilizarov. Informa healthcare publisher, New York, London. October 25th. 2006.

    Mahmoud A. El-Rosasy
    Posted on October 31, 2008
    Prophylactic Bypass Grafting in the Management of congenital tibial dysplasia
    Department of Orthopaedic Surgery - Faculty of Medicine - University of Tanta - Tanta - Egypt

    To the Editor:

    I read with interest the paper by Ofluoglu et al.(1).The concept of prophylactic bypass grafting of the anterolaterally bowed tibia (congenitally dysplastic tibia) was described by Lloyd- Roberts and Shaw(2). They thought that grafting during the period before development of fracture, the "latent period", would prevent fracture. They reported its use in seven cases and described their own results as "not wholly satisfactory". A review of the English literature reveals several reports of patients with congenital tibial dysplasia who not only did not develop fractures, but in whom the tibia became nearly normal with spontaneous deformity-resolution. Thus, some tibias will not fracture even if left alone. This raises an ethical issue--is it justified to operate on an intact tibia in patients with this diagnosis only because we believe that our procedure may prevent the development of an assumed fracture?. Especially since this procedure is neither curative nor has it been proven to be truly prophylactic(3).

    The authors described a technique identical to the bypass grafting described by McFarland (4). He believed that the cause of persistence of the pseudarthrosis must be mechanical due to angulation and the bending stresses of muscles. However, this theory has not been proven and there are reports that prove that congenital pseudarthrosis of the tibia (CPT) is a biological defect(5).

    With the development of better fixation methods and better understanding of the pathology of CPT, the current best treatment depends on the type of dysplasia. For a dysplastic tibia without fracture, no surgery is justified and the limb should be protected in a removable brace until skeletal maturity when the deformity can be safely corrected. For a psudarthrotic tibia, a biological solution should be adopted including intramedullary fixation to maintain a straight leg and lessen refractures(6).

    The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.

    References

    1.Onder Ofluoglu, Richard S. Davidson, and John P. Dormans Prophylactic Bypass Grafting and Long-Term Bracing in the Management of Anterolateral Bowing of the Tibia and Neurofibromatosis-1 J Bone Joint Surg Am 2008; 90: 2126-213

    2. Lloyd-Roberts GC, Shaw NE. The prevention of pseudarthrosis in congenital kyphosis of the tibia. J Bone Joint Surg Br. 1969 Feb 1;51(1):100-5.

    3. Nicoll EA. Infantile pseudarthrosis of the tibia. J Bone Joint Surg Br. 1969 Nov;51(4):589-92.

    4. McFarland B. Pseudarthrosis of the tibia in childhood. J Bone Joint Surg Br. 1951 Feb;33-B(1):36-46.

    5. Morrissy RT, Riseborough EJ, Hall JE. Congenital pseudarthrosis of the tibia. J Bone Joint Surg Br. 1981;63-B(3):367-75.

    6. El-Rosasy MA, Paley D, Herzenberg JE. congenital pseudarthrosis of the tibia. in Limb Lengthening and Reconstruction. Chapter 34, pages 485-495. Editors; S.R. Rozbruch and S. Ilizarov. Informa healthcare publisher, New York, London. October 25th. 2006.

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