Bone morphogenetic protein-2 for the treatment of congenital pseudarthrosis of the tibia or persistent tibial nonunion in children and adolescents: A retrospective study with a minimum 2-year follow-up

Anterolateral Tibial Bowing and Congenital Pseudoarthrosis of the Tibia: Current Concept Review and Future Directions

PURPOSE OF REVIEW

Congenital pseudarthrosis of the tibia (CPT) is a rare condition closely associated with neurofibromatosis type I. Affected children are born with anterolateral bowing of the tibia which progresses to pathologic fracture, pseudarthrosis, and high risk of refracture even after initial union has been attained. There is currently no consensus on the classification of this disease or consensus on its treatment. The purpose of this review is to (1) review the clinical presentation, etiology, epidemiology, classification, and natural history of congenital pseudarthrosis of the tibia and (2) review the existing trends in treatment of congenital pseudarthrosis of the tibia and its associated complications.

RECENT FINDINGS

Current treatment protocols focus primarily on combining intramedullary fixation with external or internal fixation to achieve union rates between 74 and 100%. Intramedullary devices should be retained as long as possible to prevent refracture. Cross-union techniques, though technically difficult, have a reported union rate of 100% and no refractures at mid- to long-term follow-up. Vascularized fibular grafting and induced membrane technique can be successful, but at the cost of numerous surgical procedures. Growth modulation is a promising new approach to preventing fracture altogether, though further study with larger patient series is necessary. The primary consideration in treatment of CPT is expected union rate and refracture risk. Combined intramedullary and external or internal fixation, especially with cross-union techniques, show most promise. Perhaps most exciting is further research on preventing fracture through guided growth, which may reduce the morbidity of multiple surgical procedures which have been the mainstay of treatment for CPT thus far.

Novel method for the treatment of congenital pseudarthrosis of the tibia using the gastrocnemius flap: A preliminary study

PURPOSE

Congenital pseudarthrosis of the tibia is a rare disease that is particularly difficult to treat; the most difficult complications include nonunion of the tibia, refracture, and failed surgery. This study aimed to evaluate the efficiency of transposing gastrocnemius flaps for the treatment of congenital pseudarthrosis of the tibia.

METHODS

Nine patients (aged 6.2 ± 3.6 years) diagnosed with congenital pseudarthrosis of the tibia in our hospital between March 2013 and March 2018 were enrolled. The tibial pseudarthrosis and thickened periosteum were completely removed, and intramedullary nails were used to fix the tibia. Bone harvest from the iliac, mixed with allogenic bone, was filled in the gap created by excision of the pseudarthrosis site and the surrounding periosteum; the gastrocnemius flap was then used to wrap the pseudoarthrosis site. The plaster cast was fixed postoperatively. The tibial union was evaluated via radiograph, and the plaster cast was removed after 12-24 weeks. Patients began walking approximately 12-14 weeks postoperatively.

RESULTS

Anatomical reduction was achieved in all the patients; the mean bone healing time was 10.1 ± 2.1 months. Bone nonunion was observed in one patient, and no neurovascular injury or wound infection occurred. Limb length discrepancy was in the range 3.2 ± 1.8 cm at 1 year and 4.7 ± 2.7 cm at 2 years after surgery. Two patients underwent replacement of the intramedullary nail, and eight patients exhibited good functional and radiographic outcomes.

CONCLUSION

This preliminary study proved that using the gastrocnemius muscle flap to cover the pseudarthrosis site was an effective method to promote the tibial union and treat congenital pseudarthrosis of the tibia.

Application of BMP in Bone Tissue Engineering

At present, bone nonunion and delayed union are still difficult problems in orthopaedics. Since the discovery of bone morphogenetic protein (BMP), it has been widely used in various studies due to its powerful role in promoting osteogenesis and chondrogenesis. Current results show that BMPs can promote healing of bone defects and reduce the occurrence of complications. However, the mechanism of BMP in vivo still needs to be explored, and application of BMP alone to a bone defect site cannot achieve good therapeutic effects. It is particularly important to modify implants to carry BMP to achieve slow and sustained release effects by taking advantage of the nature of the implant. This review aims to explain the mechanism of BMP action in vivo, its biological function, and how BMP can be applied to orthopaedic implants to effectively stimulate bone healing in the long term. Notably, implantation of a system that allows sustained release of BMP can provide an effective method to treat bone nonunion and delayed bone healing in the clinic.

Surgical treatment options for congenital pseudarthrosis of tibia in children: cross-union versus other options: a systematic review

The systematic review aimed to provide a comprehensive update on various surgical treatment options for congenital pseudarthrosis of tibia (CPT) in children and the outcome achieved in terms of union, union time and complications of non-union and refracture. A literature search was performed in PubMed (including Medline) database for broad keywords: 'Congenital pseudarthrosis of tibia and children'. Studies selected included full-text articles on surgical treatments of CPT following: intra-medullary rod (IMR)/Ilizarov/combined IMR with Ilizarov/vascularized fibular graft (VFG) and cross-union. Out of 719 studies, 57(1227 CPT patients/1235 tibias) were included for review. Cross-union group had 100% union rate with no non-unions, least refracture rate (22.5%) and minimal time to primary union (4.5 months). For IMR, Ilizarov, combined IMR with Ilizarov and VFG, the respective results were as follows: primary union rates - 67.7, 84.2, 83.7 and 65.3%; final union - 76.5, 81.5, 92.4 and 87.1%; primary union time - 12.6, 9.3, 5.3 and 9.5 months; non-union rates - 17.0, 13.6, 6.0 and 7.9%; refracture rates - 48.1, 47.7, 33.7 and 34.6%. The success probability was lowest for IMR (35.2%), 44% for Ilizarov, 55.5% for combined IMR with Ilizarov, 42.7% for VFG and highest 77.5% for cross-union group. Outcomes of the more recent cross-union technique fare better than other surgical methods. However, studies on cross-union are few and longer follow-up is lacking. Combined IMR with Ilizarov and VFG have better results compared to IMR or Ilizarov alone.

Fracture Nonunion of the Clavicle After Surgical Reduction in a 13-Year-Old Girl: A Case Report

CASE

Although congenital nonunion of the clavicle is a well-known pathology in children, posttraumatic nonunion is a rare entity. Nonunion after open reduction and internal fixation of a clavicle fracture is exceptional in the pediatric population. We report on a patient presenting posttraumatic pseudarthrosis of the clavicle after surgical treatment. Pseudarthrosis was resected, and the defect was bridged with an iliac crest autograft, supplemented with bone morphogenetic protein, and fixed with an elastic stable intramedullary nail.

CONCLUSION

This procedure offered enough stability for achieving fracture consolidation and is a safe alternative to plating in clavicle nonunion.

Management of spinal deformities and tibial pseudarthrosis in children with neurofibromatosis type 1 (NF-1)

The skeletal system is affected in up to 60% of patients with neurofibromatosis type 1. The most commonly observed entities are spinal deformities and tibial dysplasia. Early recognition of radiologic osseous dystrophy signs is of utmost importance because worsening of the deformities without treatment is commonly observed and surgical intervention is often necessary. Due to the relative rarity and the heterogenic presentation of the disease, evidence regarding the best surgical strategy is still lacking.

PURPOSE

To report our experience with the treatment of skeletal manifestations in pediatric patients with (neurofibromatosis type 1) NF-1 and to present the results with our treatment protocols.

MATERIALS AND METHODS

This is a retrospective, single expert center study on children with spinal deformities and tibial dysplasia associated with NF-1 treated between 2006 and 2020 in a tertiary referral institution.

RESULTS

Spinal deformity: Thirty-three patients (n = 33) were included. Mean age at index surgery was 9.8 years. In 30 patients (91%), the deformity was localized in the thoracic and/or lumbar spine, and in 3 patients (9%), there was isolated involvement of the cervical spine. Eleven patients (33%) received definitive spinal fusion as an index procedure and 22 (67%) were treated by means of "growth-preserving" spinal surgery. Halo-gravity traction before index surgery was applied in 11 patients (33%). Progression of deformity was stopped in all patients and a mean curve correction of 60% (range 23-98%) was achieved. Mechanical problems with instrumentation requiring revision surgery were observed in 55% of the patients treated by growth-preserving techniques and in none of the patients treated by definitive fusion. One patient (3%) developed a late incomplete paraplegia due to a progressive kyphotic deformity. Tibial dysplasia: The study group comprised of 14 patients. In 5 of them (36%) pathological fractures were present on initial presentation. In the remaining 9 patients (64%), anterior tibial bowing without fracture was observed initially. Four of them (n = 4, 28%) subsequently developed a pathologic fracture despite brace treatment. Surgical treatment was indicated in 89% of the children with pathological fractures. This involved resection of the pseudarthrosis, autologous bone grafting, and intramedullary nailing combined with external fixation in some of the cases. In 50% of the patients, bone morphogenic protein was used "off-label" in order to promote union. Healing of the pseudarthrosis was achieved in all of the cases and occurred between 5 to 13 months after the index surgical intervention. Four of the patients treated surgically needed more than one surgical intervention in order to achieve union; one patient had a re-fracture. All patients had a good functional result at last follow-up.

CONCLUSION

Early surgical intervention is recommended for the treatment dystrophic spinal deformity in children with NF-1. Good and sustainable curve correction without relevant thoracic growth inhibition can be achieved with growth-preserving techniques alone or in combination with short spinal fusion at the apex of the curve. Preoperative halo-gravity traction is a safe and very effective tool for the correction of severe and rigid deformity in order to avoid neurologic injury. Fracture union in tibial dysplasia with satisfactory functional results can be obtained in over 80% of the children by means of surgical resection of the pseudarthrosis, intramedullary nailing, and bone grafting. Wearing a brace until skeletal maturity is achieved is mandatory in order to minimize the risk of re-fracture.

Safety and Efficacy of Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) in Craniofacial Surgery

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is one of the most commonly used osteogenic agents in the craniofacial skeleton. This study reviews the safety and efficacy of rhBMP-2 as applied to craniofacial reconstruction and assesses the level of scientific evidence currently available.

Congenital pseudarthrosis of the tibia: biological and biomechanical considerations to achieve union and prevent refracture

Congenital pseudarthrosis of the tibia (CPT) is likely to be a primary periosteal disease and secondary bone disease. The primary goal of treatment is to obtain union, correct the diaphyseal deformity, correct any proximal fibular migration and prevent refracture. The pathobiology demonstrates increased osteoclasis by the surrounding fibrous hamartoma and reduced osteogenesis and bone morphogenic protein production by the bone. This leads to a loss of remodelling potential and gradual bowing and atrophy of the bone with eventual fracture of the tibia and or fibula. This recommends the synergistic use of bisphosphonates and bone morphogenic protein. The pathomechanics of CPT implicate the anterolateral bowing, narrow diameter of the atrophic bone ends and proximal fibular migration. These biomechanical factors can be addressed by means of straightening of the deformity, intramedullary support of both bones, stable fixation and reduction of proximal migration of the fibula. A summary of the literature on CPT shows that the mean probability of achieving primary union without refracture, by most treatments is 50% (12% to 80%). Two recent studies have shown a much higher success rate approaching 100%, by creating a cross-union between the tibia and fibula. The cross-union with intramedullary reinforcement of the bone makes refracture unlikely due to the cross-sectional area of union with its two-bar linkage. A new classification to guide such treatment is also proposed.

LEVEL OF EVIDENCE

V - expert opinion.