Pećina, Marko

Smoljanović, Tomislav

English

University of Zagreb Medical School Repository

        Središnja medicinska knjižnica        Smoljanović, T., Pećina, M. (2008) RE: complications attributable to the use of rhBMP-2 inside the femoral ring allograft during anterior lumbar interbody fusion. The Spine Journal, 8 (2). pp. 413-414.    http://www.elsevier.com/locate/issn/1529-9430 http://dx.doi.org/10.1016/j.spinee.2007.11.004  http://medlib.mef.hr/330              University of Zagreb Medical School Repository http://medlib.mef.hr/   1 Letters  Complications Attributable to the Use of rhBMP-2 Inside the Femoral Ring Allograft during Anterior Lumbar Interbody Fusion  Tomislav Smoljanovic, MD,* Marko Pecina, MD, PhD*  *Department of Orthopaedic Surgery, School of Medicine, University of Zagreb, Zagreb, Croatia  Tomislav Smoljanovic, MD (corresponding author) Department of Orthopaedic Surgery School of Medicine University of Zagreb Salata 7 10000 Zagreb Croatia E-mail: drsmoljanovic@yahoo.com Phone: +385-1-4818833 Fax: +385-1-4818810    2 To the Editor:  Complications Attributable to the Use of rhBMP-2 Inside the Femoral Ring Allograft during Anterior Lumbar Interbody Fusion   We read with great interest the prospective analysis of interbody fusion rates by Slosar et al. [1] in which the exceptionally excellent results concerning the use of femoral ring allografts (FRA) with rhBMP-2 during anterior lumbar interbody fusion (ALIF) in addition with posterior pedicle screw fixation were reported. Namely, the rhBMP-2 group had a 100% fusion rate in all levels attempted (n=103), there were no complications attributable to the use of rhBMP-2 and no osteolysis or fragmentations of the allografts were observed. But, there was no mention of the subsidence which is defined as a fusion device sinking into one or both of the adjacent vertebral bodies [2] and end-plate erosions.  On the other side, Vaidya et al. [3] who used machined allograft spacers centrally filled with rhBMP-2 and additional posterior pedicle screw fixation during ALIF and also had 100% fusion rate, found that 70% (14 of 20) of levels had signs of early lucency and underwent significant (> 10%) graft subsidence of a mean of 27% (13% to 42%). CT scans obtained from patients who received allograft/rhBMP-2 revealed two phenomena that may have contributed to subsidence. First, early lucency and incorporation of the allograft were noted, which may have resulted in a loss of structural support. Secondly, there was significant end-plate erosion in each rhBMP-2 case, an appearance that was not evident in patients treated without rhBMP-2.   End-plate erosions have been observed by CT during the first months of follow up in 3 of 4 published studies concerning the use of FRA or similarly shaped allografts and rhBMP-2 during ALIF [3-5] with [3,4] or without additional posterior instrumentation [5]. The only  3 study, beside the one of Slosar et al., which didn’t report end-plate erosion, was the case report by Lee et al. [6]. It was even expected as the CT was not used during the follow up. By the way, Lee et al. reported about histological analysis of a displaced femoral ring allograft spacer filled with rhBMP-2 soaked collagen sponge in a patient who also had additional posterior instrumentation 6 months after the surgery  The total doses of rhBMP-2 used per level of fusion were similar among mentioned studies (from 2 mg to 4,2 mg) (Joon Y. Lee, MD, written communication, September, 2007) [3,4,6] including Slosar et al. who used 3 mg of rhBMP-2 [1]. Only Pradhan et al. used higher dose of rhBMP-2 per level of fusion, i.e. 12 mg (Ben B. Pradhan, MD, MSE, written communication, September, 2007) [5].  As the subsidence and end-plate erosion have not been mentioned at all in the entire manuscript of Slosar et al. [1], not even as possibilities of unanticipated adverse events related to the use of rhBMP-2, it is probable that authors have not been aware of these disorders at the time. The probability was confirmed when an overlooked subsidence of FRA allograft 6 months following surgery at Figure 1 and 2 was noticed in the study of Slosar et al. (Figure 1) [1]. In the light of the presented findings, we kindly ask the authors to evaluate once again the CT scans from the patients involved in the study obtained 6 months after the operation concerning the subsidence and end-plate erosions and to inform reading audience about the results.     4 Figure Legend  Figure 1. From the Slosar et al study. The arrows point the overlooked subsidence of femoral ring allograft into vertebral body 6 months following surgery, A) anterior view, B) lateral view.  5 Reference  1. Slosar PJ, Josey R, Reynolds J. Accelerating lumbar fusions by combining rhBMP-2 with allograft bone: a prospective analysis of interbody fusion rates and clinical outcomes. Spine J. 2007;7:301-307. 2. Williams AL, Gornet MF, Burkus JK. CT evaluation of lumbar interbody fusion: current concepts. AJNR Am J Neuroradiol. 2005;26:2057-2066. 3. Vaidya R, Weir R, Sethi A, Meisterling S, Hakeos W, Wybo CD. Interbody fusion with allograft and rhBMP-2 leads to consistent fusion but early subsidence. J Bone Joint Surg Br. 2007;89:342-345. 4. Hansen SM, Sasso RC. Resorptive response of rhBMP2 simulating infection in an anterior lumbar interbody fusion with a femoral ring. J Spinal Disord Tech. 2006;19:130-134. 5. Pradhan BB, Bae HW, Dawson EG, Patel VV, Delamarter RB. Graft resorption with the use of bone morphogenetic protein: lessons from anterior lumbar interbody fusion using femoral ring allografts and recombinant human bone morphogenetic protein-2. Spine. 2006;31:E277-284. 6. Lee JY, Zeiller S, Voltaggio L, Lim MR, Hilibrand AS, Vaccaro AR, et al. Histological analysis of a displaced femoral ring allograft spacer filled with a recombinant human bone morphogenetic protein-2-soaked collagen sponge. A case report. J Bone Joint Surg Am. 2005;87:2318-2322.  

RE: complications attributable to the use of rhBMP-2 inside the femoral ring allograft during anterior lumbar interbody fusion

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