520 - Long-term Safety and Efficacy of Human Bone Morphogenetic Protein (hBM...

#520 Long-term Safety and Efficacy of Human Bone Morphogenetic Protein (hBMP) in the Treatment of Resistant Non-unions and Failed Arthrodesis: A Retrospective Study

Biologic Therapies

Poster Presented by: O. Amajoyi

Author(s):

A.N. Shamie (1)
O. Amajoyi (1)
E. Johnson (1)

(1) Ronald Reagan UCLA Medical Center, Department of Orthopaedic Surgery, Los Angeles, CA, USA

Abstract

Introduction: The management for the majority of cases of pseudarthrosis and nonunions include mechanical stabilization, in addition to the application of demineralized bone matrix, autogenous bone graft, or bone morphogenetic proteins (BMP). BMP has emerged as a suitable alternative to autogenous cancellous bone grafting due to its ability to decrease the number of non-unions, risk of infection, and donor site morbidity. Furthermore, it has been shown to enhance the rate of fracture healing via progenitor cell chemotaxis and inducing differentiation and proliferation of mesenchymal cells into cartilage and bone-forming cells. Despite current knowledge about its mechanism, few studies provide evidence about the long-term safety of BMP. The aim of this investigation is to determine if BMP implantation is a safe and effective agent in a long-term setting for the treatment of patients with resistant nonunions and failed arthrodesis.

Methods: An IRB-approved, retrospective case series was conducted on 55 patients with prior attempt at fracture fixation or spinal fusion. These cases resulted in nonunion or pseudarthrosis, and were subsequently treated with revision surgery and hBMP implantation. Non-union was defined as

1) motion at the fracture site,

2) persistent pain at the fracture site, and

3) absence of bridging bone in the long bones or lumbar spine x-rays on at least two views upon radiographic examination greater than 6 months after the initial operation.

Patients were evaluated at different time-points post-operatively. To assess the safety and efficacy of hBMP use, the following complications were identified:

1) persistent nonunion or failed spinal arthrodesis,

2) malignancy,

3) wound infection,

4) allergic reaction to hBMP, and

5) hematoma or seroma formation at the site of hBMP implantation.

Results: All of the patients reached a minimum follow-up time of 12 months. The average follow-up time was 84 months (7 years; SD ± 44 months, range = 12-256 months). Seven patients (13%) experienced adverse events related to their surgery with hBMP. Six patients (11%) experienced persistent nonunion; five of these underwent further revision surgery with hBMP that subsequently resulted in successful union. One patient (2%) developed an infected nonunion, which was treated with removal of hardware, revision surgery, and a course of antibiotics. No patients experienced tumor induction, allergic reaction to hBMP, or development of a hematoma or seroma at the hBMP implant site. The remaining 48 patients all achieved osseous union within 6 months of hBMP implantation.

Conclusion: The cornerstone of successful bone healing rests on improving current strategies aimed towards both the biomechanical stability of bone, and the biological vitality of bone, albeit in a safe manner. This study contributes to the latter. This study differs from previous literature by providing data suggesting that the use of hBMP is a safe, non-toxic, and efficacious treatment method for resistant nonunions and failed arthrodesis in the long-term setting. With a mean follow-up time of 84 months, this study stands alone in assessing the long-term potential sequelae associated with hBMP. It has great clinical utility in this patient population, and when used in a judicious fashion can help avoid the limitations and comorbidities associated with other bone grafts and bone graft substitutes.