Vertebral Body Osteolysis following Transpsoas Interbody Fusion with rhBMP-2

Presented at SMISS Annual Forum 2014
By Reginald Q. Knight MD, MHA
With Scott Grainger BS, RN, Melissa Scribani MPH, Jibiao Huang PAC, Grace Ma MD,

Disclosures: Reginald Knight MD, MHA B; Stryker Spine, Vertebral Technology Inc, Vertera Spine. C; Stryker Spine, Vertebral Technology Inc, Vertera Spine. D; Vertebral Technology Inc, Vertera Spine, Gerstner Medical. Scott Grainger BS, RN None, Melissa Scribani MPH None, Jibiao Huang PAC None, Grace Ma MD None,

Introduction:
Literature convening use of rhBMP-2 in lumbar fusion patients has raised concern regarding the incidence of associated complications, such as osteolysis. Published data with respect to osteolysis and trranspsoas interbody fusion is limited.

Aims/Objectives:
Ascetain occurrence and reliability of grading osteolysis, its impact on patient functional improvement and fusion rate associated with use of rhBMP-2 during transpsoas lumbar interbody fusion.

Methods:
From August 2010 through June 2012 22 consecutive transpsoas interbody fusion patients with 4.2 mg rhBMP-2/level and supplemental fixation were studied. Serial radiographs and functional outcome data were collected preop, 1, 4, 10, and 24 months. Postop CT scans with sagittal and coronal reconstructions were obtained on all patients at 10 months. Test data with specific criteria grading osteolysis and fusion were analyzed in test retest format. Osteolysis was decried as absent, mild, moderate or severe with fusion designated as bony, fibrous or absent. Intra and inter-observer agreement was determined.

Results:
35 levels were fused. 8/22 patients underwent multilevel procedures. L3-4 was most common. 210 disc space evaluations were made. Agreement improved following test retest. Inter-observer agreement was moderate for fusion (kappa = 0.59) and slight for osteolysis (kappa = 0.07). 77% of patients demonstrated osteolysis 60% of these were mild (<5mm). 85% suggested solid bone fusion. Statistically significant improvement in Oswetry (preop 42.5; 24 months 28.5) and visual analog scale (back pre 66; 24 month 39.2: leg pre 65; 24 month 28.5) was noted independent of osteolysis.

Conclusions:
Mild osteolysis (<5mm) is frequently seen following use of rhBMP-2 for transpsoas lumbar interbody fusion. Occurrence of this level of osteolysis does not appear to negatively impact fusion rate or patient functional outcome.