Published online Jan 18, 2017. doi: 10.5312/wjo.v8.i1.36
Peer-review started: June 20, 2016
First decision: July 29, 2016
Revised: August 29, 2016
Accepted: October 25, 2016
Article in press: October 27, 2016
Published online: January 18, 2017
To present the incidence of heterotopic ossification after the use of recombinant human bone morphogenetic protein-7 (rhBMP-7) for the treatment of nonunions.
Bone morphogenetic proteins (BMPs) promote bone formation by auto-induction. Recombinant human BMP-7 in combination with bone grafts was used in 84 patients for the treatment of long bone nonunions. All patients were evaluated radiographicaly for the development of heterotopic ossification during the standard assessment for the nonunion healing. In all patients (80.9%) with radiographic signs of heterotopic ossification, a CT scan was performed. Nonunion site palpation and ROM evaluation of the adjacent joints were also carried out. Factors related to the patient (age, gender), the nonunion (location, size, chronicity, number of previous procedures, infection, surrounding tissues condition) and the surgical procedure (graft and fixation type, amount of rhBMP-7) were correlated with the development of heterotopic ossification and statistical analysis with Pearsons χ2 test was performed.
Eighty point nine percent of the nonunions treated with rhBMP-7, healed with no need for further procedures. Heterotopic bone formation occurred in 15 of 84 patients (17.8%) and it was apparent in the routine radiological evaluation of the nonunion site, in a mean time of 5.5 mo after the rhBMP-7 application (range 3-12). The heterotopic ossification was located at the femur in 8 cases, at the tibia in 6, and at the humerus in οne patient. In 4 patients a palpable mass was present and only in one patient, with a para-articular knee nonunion treated with rhBMP-7, the size of heterotopic ossification affected the knee range of motion. All the patients with heterotopic ossification were male. Statistical analysis proved that patient’s gender was the only important factor for the development of heterotopic ossification (P = 0.007).
Heterotopic ossification after the use of rhBMP-7 in nonunions was common but it did not compromise the final clinical outcome in most cases, and affected only male patients.
Core tip: Bone morphogenetic proteins are identified as factors promoting osteogenesis. In this study an attempt was made to estimate the rate of heterotopic bone formation in patients with long bone nonunions treated with recombinant human bone morphogenetic protein-7 (rhBMP-7), and to identify predisposing factors, related to the patient, the nonunion characteristics, and the surgical procedure. Eighteen percent of the patients developed heterotopic ossification on the radiographs, without functional limitations. All patients that developed heterotopic ossification were male. This rate of heterotopic ossification after rhBMP-7 use for the treatment of long bone nonunions is higher than the rates reported in literature.