Osteofibrous dysplasia (OFD) is characterized by osteolysis in the cortex, peripheral sclerosis, dilation and thinning of the cortical surface, and narrowing of the marrow cavity. It is a rare, benign fibroosseous lesion that predominantly occurs in the tibia of children[1]. While often asymptomatic, it can induce pain and deformity[2, 5]. Although OFD bears clinical and radiologic similarities to adamantinoma (ADM), the direct association between the two, especially considering the malignant nature of ADM, remains a subject of debate. Some researchers suggest that OFD could be a precursor to adamantinoma or even develop secondary to adamantinoma degeneration, prompting recommendations for radical surgical measures like wide excision or amputation due to the suspected ADM association[4]. Conversely, others argue that the risk of OFD transforming to ADM appears low in clinical practice[6, 8, 9]. Recent longitudinal studies of both unilateral and bilateral OFD cases extending into adulthood have not identified any instances of malignant transformation[9]. We firmly believe that open biopsy is an essential part of patient management, recommending it for all patients to exclude the presence of adamantinoma and other bone tumors. In this cohort of 4 patients, we conducted pathological examinations during surgery to achieve clear pathological results.
Treatment strategies should be tailored to the clinical and anatomical specifics of the lesion. Observation might be best for children with minor symptoms, such as occasional pain or slight swelling. In contrast, surgical interventions are advised for those presenting with persistent pain, pathological fractures, or worsening tibial deformity[5]. All our studied cases were exceptional OFD examples. All four manifested significant bowing deformity with extensive lesions. The median lesion length was 14.5 cm (9-21.5 cm) with a lesion length ratio of 63.2% (50–75%) and an anterior bowing angle averaging 32° (20°-48°). Clinicians face two primary challenges regarding the natural history of anterior tibial bowing: the self-worsening nature of the bowing deformity and the very low spontaneous healing probability of tibial fractures, which also complicates surgical treatments[10].
Multiple studies posit that the primary objective of OFD treatment is lesion resection to minimize recurrence. This approach has proven effective for small lesions or those limited to a single cortex. Curettage and allograft treatment of OFD have yielded satisfactory outcomes and low recurrence rates as documented by several authors [5, 11]. For extensive lesions causing deformity, most researchers recommend extra-periosteal resection, which, regardless of the reconstruction method employed, can result in significant bone defects and may pose high surgical risks and complications [5, 6].
Lee et al. [4] presented five cases of OFD with expansive lesions, treated with extra-periosteal resection followed by bone transport using the Ilizarov technique. Although all patients achieved symptom and disease remission, the distraction osteogenesis process compelled patients to endure external fixators for several months, a challenge many found hard to accept. Moreover, three patients required further surgery due to nonunion at the docking site, while two experienced pin-site infections.
Another study by Yunan Lu [5] reported five OFD cases (mean age: 8.2 years; range, 2 to 12) of the tibia with extensive lesions. These underwent extra-periosteal excision and primary bone transport using an Ilizarov external fixator. Complications recorded included one case of delayed union, two of pin-site infection, and one of joint stiffness. Given the higher complication rate and elevated costs, Lu advises selective utilization of this technique.
In Dala-Ali's report [6], 19 lesions (extensive, recurrent, or progressive) underwent wide excision, and three distinct reconstruction methods addressed bone defects: bone transport, fibular graft, and megaprosthesis. Bone transport presented with the highest incidence of tibial nonunion (4/6), all of which needed re-grafting. One case required supplementary stabilization using a plate, and another with an external fixator. Fibular graft complications included recurrence (2/10) and nonunion (2/10). Notably, while the free vascularized fibula graft is a globally recognized method for filling bone defects, donor site complications persist.
Dong Li [12] documented 12 patients treated with extraperiosteal segmental excision and reconstruction using liquid nitrogen-treated recycled autograft and allograft to address bone defects. The median resected segment length was 8 cm (range: 5–11 cm). Follow-up radiographs indicated a median complete union time of 9 months (range: 6–15 months). This prolonged healing time necessitated extended external fixation immobilization.
As OFD is self-limiting, stabilizing with bone maturity, contemporary research proposes focusing on deformity correction rather than lesion treatment. In a 2022 study, Dala-Ali [6] monitored 101 tibial OFD patients over an average of 5.65 years. The findings certified OFD as benign, with minimal progression and no malignant transformations. Surgery, Dala-Ali suggests, should prioritize angular deformity. In a corroborating study, Daniel Westacott [7] observed 28 tibial OFD cases, noting lesion stability with bone maturity and no malignancy signs. Westacott further promoted minimally invasive techniques to restore tibial force lines and functionality over broad lesion removal.
Similar to the views of these authors, the main purpose of our treatment is to correct angular deformity rather than the lesion.In this paper, we report for the first time the use of minimally invasive tibial osteotomy, and TR fixation to correct anterior bowing deformity and maintain alignment of the tibia. Compared with lesion resection and bone reconstruction, this surgical method has less trauma, faster healing, avoids large bone defects and difficult bone reconstruction, and is more acceptable to patients and their families.
It's crucial to differentiate OFD's anterior bowing deformity from the congenital tibial variant. The latter often precedes congenital tibial pseudarthrosis and frequently associates with type I neurofibromatosis. Given congenital anterior bowing's unique nature, post-osteotomy complications like non-union and pseudarthrosis are common, rendering osteotomy contraindicated for congenital tibial bowing deformities [13, 14]. Few studies discuss potential nonunion or pseudarthrosis following tibial osteotomies in OFD-affected children. In our patient group, osteotomies occurred within the tibial tumor lesion, followed by TR fixation continuity restoration. Subsequent assessments showed successful osteotomy end healing in four patients, averaging a bone healing duration of 3 months (range: 2.5–4.5 months), with no instances of nonunion or pseudarthrosis.
In the case report by Nakahara H[15], a 6-year-old child with OFD exhibiting tibial varus underwent treatment using an intrafocal orthopaedic locking plate for internal fixation. The 3-year follow-up indicated positive outcomes, with no observed deformity, implant failure, or progression of the lesion. The patient demonstrated the ability to run and returned to daily activities without restrictions. However, given the limited follow-up duration, concerns remain regarding potential re-fracture as the child's tibia grows. Contrasting Nakahara H's approach, our study opted for TR fixation. TR has been extensively documented as a secure and durable technique for pediatric deformity correction surgery. It has seen successful applications in the deformity correction of osteogenic imperfections in the femur and tibia and in CROSS-fusion of congenital pseudarthrosis of the tibia in children[16–17]. However, its use in children with OFD remains unreported. In our study, we detail the application of TR in patients undergoing tibia osteotomy to restore bone alignment. The subsequent outcomes from our cases underscored TR's capability to consistently maintain the tibia's mechanical axis, adapt to the child's growth, and act as a preventive measure against fractures. Yunan Lu[5] mentioned the use of ESIN to preserve the tibial axis post-lesion removal in OFD patients, which provided substantial support. However, with the tibia's growth, ESIN tends to displace from the tibia's ends, necessitating a subsequent procedure for its replacement as the child ages. In our patient cohort, given the non-resection of the lesion, the lesion's area might eventually surpass the length of the ESIN due to growth. TR's extendable nature accommodates the tibia's growth, with both ends anchored in the epiphysis, alleviating concerns about variations in the tibial lesion's length. Nevertheless, challenges exist, including the complexities involved in replacing or extracting TR. Given the tumor lesions in children, there's a heightened risk of re-fractures or anterior arch deformities. Hence, to prevent fractures, we don't recommend the removal of extendable nails.
All four patients in our study displayed LLD with an average extremity length discrepancy of 7.5 mm (ranging from 5–10 mm). This discrepancy may be attributed to the tibia's excessive growth following repeated pathological fractures and partial lesion area resection during surgeries. One patient benefited from insole correction, while the others underwent observation.
The MSTS score, initially formulated for evaluating post-malignant tumor reconstruction functionality[18], was repurposed in our study to assess benign tumors. Its components, including pain, gait, orthosis use, walking capability, function, and patient satisfaction, offer invaluable metrics for clinicians evaluating lower limb diseases. We believe the MSTS score is apt for gauging the prognosis of OFD in children. Our surgical procedure significantly enhanced children's quality of life, eliciting heightened satisfaction from parents.
However, our research has its constraints. Firstly, the disease's rarity led to a smaller patient sample size, coupled with the study's retrospective nature. Secondly, the relatively short follow-up duration for the children necessitates extended observation to discern long-term effects until bone maturation.
In conclusion, minimally invasive tibia osteotomy combined with telescopic rod osteosynthesis, without lesion resection, proves effective for treating bowing deformities resulting from osteofibrous dysplasia. This approach circumvents the creation of sizable bone defects and intricate bone reconstructions, markedly enhancing limb functionality and the affected children's quality of life.