Can Adding BMP2 Improve Outcomes in Patients Undergoing the SUPERhip Procedure?

Abstract

Congenital femoral deficiency (CFD) Paley type 1b is characterized by severe bony deformity of the upper femur, extra-articular contractures of the hip, and, delayed ossification of the femoral neck and/or subtrochanteric region. The Systematic Utilitarian Procedure for Extremity Reconstruction of the hip (SUPERhip) procedure for the correction of CFD deformities was developed in 1997. Initially, a non-fixed angle device (rush rod) was used for fixation. Late complications of persistent delayed ossification and recurrent varus deformity occurred. In order to reduce and treat such complications, fixation with a fixed angle device and the off-label use of BMP2 to induce ossification of the un-ossified femoral neck were employed. The purpose of this study is to determine if the use of a fixed angle device, and, BMP2 inserted into a drill hole in the cartilage of the femoral neck, decreases the incidence of these late complications. We retrospectively reviewed 72 SUPERhip procedures performed for Paley type 1b CFD between 1997 and 2012. Due to recurrent varus or persistent delayed ossification of the femoral neck, 34 revision SUPERhip procedures were performed. In total, 106 SUPERhip procedures were studied. Sixty-eight SUPERhips were performed using internal fixation without BMP2, while 38 SUPERhips were performed with both internal fixation and the addition of BMP2. Forty-one were performed using non-fixed angle internal fixation while 65 had fixed angle internal fixation. Fixed angle devices significantly reduced the incidence of recurrent varus compared with non-fixed angle devices. Inserting BMP2 in the femoral neck significantly reduced the incidence of persistent delayed ossification. Using only a fixed angle device but no BMP2 did not reduce the incidence of delayed ossification. The combination of both a fixed angle device and BMP2 reduced the incidence of recurrent coxa vara and persistent delayed ossification of the femoral neck. The SUPERhip procedure corrects the pathoanatomy of the proximal femur in CFD Paley type 1b but is associated with a very high risk of recurrence of coxa vara and persistence of femoral neck delayed ossification, unless, a fixed angle internal fixation device is used to prevent recurrent coxa vara and BMP2 is used to induce ossification of the femoral neck.

Keywords

• congenital femoral deficiency (CFD)
• proximal focal femoral deficiency (PFFD)
• coxa vara
• bone morphogenic protein 2 (BMP2)
• endochondral ossification