- Email: [email protected]
Extrusion of Biocompatible Osteoconductive Polymer (BOP) Causing Cervical Myelopathy
Case Report
Extrusion of Biocompatible Osteoconductive Polymer (BOP) Causing Cervical Myelopathy Hyung-Youl Park1, Young-Hoon Kim2, Kee-Yong Ha2, Sang-Il Kim2, Kee-Won Rhyu4, Joon-Hyuck Oh4, Chan-Kwon Jung3
Key words Polymethylmethacrylate-N-vinylpyrrolidone - Reoperation - Spinal cord compression - Spinal fusion -
Abbreviations and Acronyms BOP: Biocompatible osteoconductive polymer CT: Computed tomography MRI: Magnetic resonance imaging From the 1Department of Orthopedic Surgery, Eunpyeong St. Mary’s Hospital; Departments of 2Orthopedic Surgery and 3 Hospital Pathology, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, and 4 Department of Orthopedic Surgery, St. Vincent Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea To whom correspondence should be addressed: Young-Hoon Kim, M.D., Ph.D. [E-mail: [email protected]] Supplementary digital content available online. Citation: World Neurosurg. (2019) 127:249-252. https://doi.org/10.1016/j.wneu.2019.04.033 Journal homepage: www.journals.elsevier.com/worldneurosurgery Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2019 Elsevier Inc. All rights reserved.
INTRODUCTION As the prevalence of spinal fusion surgery has increased, the focus on bone graft alternatives has also increased.1 Whereas autologous bone grafts remain the criterion standard, efforts to develop reliable and safe bone graft substitutes have been carried out to prevent the morbidities and complications related to obtaining autologous bone graft material.2,3 Although approximately 1400 products are available for use as bone graft substitutes, they should be evaluated to confirm their safety and efficacy as materials for solid fusion.4,5 Biocompatible osteoconductive polymer (BOP) is an example of such an important lesson. We present a case of extruded BOP and discuss the
- BACKGROUND:
As the prevalence of spinal fusion surgery has increased, reliable and safe bone graft substitutes have been developed in response. Biocompatible osteoconductive polymer (BOP) has been used as a bone graft alternative for spine surgery. We present a case of cervical myelopathy due to extrusion of BOP 23 years after surgery and discuss the pathophysiology in terms of spinal fusion.
- CASE
DESCRIPTION: A 65-year-old man presented with a 3-month history of cervical myelopathic symptoms. Twenty-three years earlier, the patient had undergone cervical surgery for a C6e7 herniated disc with the use of BOP. Imaging studies of the cervical spine showed cord compression due to extruded BOP at C6e7. He underwent corpectomy of the C7 vertebral body and removal of the BOP for the neural decompression, combined with interbody fusion by use of an iliac bone graft and plate fixation. During the operation, crumbly fibers of the BOP were easily removed. His myelopathic symptoms improved immediately after surgery. Postoperative magnetic resonance imaging also showed successful decompression of the spinal cord. Histologically, a foreign body reaction and bony degeneration were found around the synthetic fibers of the BOP.
- CONCLUSIONS:
Spine surgeons should recognize the pathophysiology of the BOP used for spine fusion surgery. Although BOP is not currently used for spinal surgery, patients undergoing previous surgery with the BOP can present with related complications. Revision surgery is recommended to remove the unincorporated BOP and achieve solid spine fusion.
pathophysiology of BOP in aspects of spinal fusion. CASE REPORT A 65-year-old man presented with right shoulder pain and gait disturbances, which had become aggravated over 3 months. He had undergone cervical anterior surgery for a C6e7 disc herniation 23 years earlier at another hospital. At his initial visit to our hospital, the patient reported that an artificial disc had been used for the surgery. On physical examination, he had a sensory disturbance in the little finger, and his patellar tendon reflex was exaggerated. He did not have motor weakness, and the Hoffmann sign was negative. Magnetic resonance imaging (MRI) of the
WORLD NEUROSURGERY 127: 249-252, JULY 2019
cervical spine revealed that graft material with low signal intensity on T2-weighted image was compressing the cord, resulting in signal changes mainly on the right side (Figure 1A).6 Computed tomography (CT) of the cervical spine showed that radiolucent material was extruded into spinal canal, with marginal sclerosis (Figure 1B). The patient underwent surgery for cervical myelopathy caused by extruded graft material. Although he had no hoarseness or dysphagia after the previous surgery conducted on the left side, we approached the index level on the right side to avoid postoperative adhesion. The operative findings revealed that some separated fibers were also extruded ventrally, causing severe adhesion around the esophagus. We performed careful dissection of the
www.journals.elsevier.com/world-neurosurgery
249
CASE REPORT HYUNG-YOUL PARK ET AL.
EXTRUDED BOP CAUSING CERVICAL MYELOPATHY
Figure 1. Cervical compressive myelopathy due to extruded biocompatible osteoconductive polymer (BOP). (A) Magnetic resonance image revealing BOP compression of the cord showing signal changes (arrowhead) on right side. (B) Computed tomographic view showing extrusion of radiolucent material into spinal canal, with marginal sclerosis.
interbody arthrodesis and decompression esophagus and removal of graft fragof the spinal cord (Figure 2). The patient ments. Huge extruded grafts were not reported no shoulder pain and gait easily removed, even after the C6e7 disdisturbance at his 1-year follow-up visit. cectomy and removal of fragments. After The BOP fragments taken during surthe C7 corpectomy and additional C6e7 gery were examined histologically. The foraminotomy, complete decompression microscopic findings revealed and removal of graft materials some inflammatory cells, was achieved (Supplementary including multinucleated Video 1). We conducted the foreign bodyetype giant cells, C6eT1 interbody fusion among the polymers. Moreusing autologous iliac bone over, degeneration of normal grafts and plate fixation. The Video available at www.sciencedirect.com bony tissue, rather than new removed grafts were easily bone formation, was found disrupted into separable around the BOP fibers (Figure 3). fibers. After the surgery, we identified the graft materials as the BOP from previous surgery at another hospital. The DISCUSSION patient reported improvement in his right shoulder pain immediately after the The BOP consists of 50% polyamide-6 fisurgery and was able to ambulate on the bers, 40% matrix (copolymer N-vinylsecond postoperative day without gait pyrorolidone and methylmethacrylate), disturbance. Postoperative radiographs and 10% calcium gluconate. BOP was and MRI also showed successful developed and has been used as a spacer
Figure 2. Postoperative imaging after revision surgery. (A) Plain radiographs revealing interbody fusion with autogenous iliac bone and plate fixation. (B) Magnetic resonance image showing successful decompression of spinal cord.
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for osteosynthesis and filling of bone defects since the 1970s.7 Then, Skondia et al.8 reported that BOP could be used not only as a spacer for bone filling and reconstructive surgery but also as intramedullary rods, owing to the enhanced mechanical characteristics of the polymer, such as ingrowth of fibrous tissue. Ortolani et al.9 also demonstrated that new bony tissue was incorporated into the BOP histologically in animal models, and more bone regeneration was observed radiographically in human patients treated with BOP after molar extraction. It was suggested that osteoblastic activity, coupled with an osteoclastic reaction, may have resulted in partial fragmentation of the polyamide fibers and their incorporation into the newly formed bone.7 The use of BOP for spine surgery has been reported since the late 1980s. Lozez et al.10,11 reported the use of BOP for bone graft complements and interbody grafts in the arthrodesis of the spine. Owing to the increasing use of BOP for cervical spine surgery, commercial products of BOP (DTI Med. Corporation, Fleurus, Belgium) for the cervical spine were developed in 2 forms: BOP-B block for Smith-Robinson procedures and BOP B-octa for Cloward procedures.12 However, the clinical outcomes after the use of BOP for cervical surgery were not satisfactory. Madawi et al.12 conducted a prospective comparative study between BOP and iliac grafts on 115 patients. They reported that BOP did not show any radiologic evidence of biodegradation or incorporation, despite similar clinical outcomes seen with the iliac graft. Ibanez et al.13 also reported that BOP, used as intervertebral grafts in anterior cervical surgery showed significantly higher graft complications and worse bone fusion, compared with heterologous bovine grafts, although the clinical outcomes were similar. Moreover, reports of complications related to the use of BOP for cervical spine surgery have increased (Table 1).14-18 Symptoms can differ depending on the direction of the extrusion. The anterior extrusion of BOP caused dysphagia, and neurologic symptoms developed in the cases of posterior extrusion. As treatments for these conditions, removal of extruded BOP was effective for
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2019.04.033
CASE REPORT HYUNG-YOUL PARK ET AL.
EXTRUDED BOP CAUSING CERVICAL MYELOPATHY
Figure 3. Histologic findings around the biocompatible osteoconductive polymer (BOP). (A) Multinucleated foreign bodyetype giant cells (arrowhead) among the polymers. (B) Degeneration of normal bony tissue (arrow) around the fibers of BOP (arrowhead). Hematoxylin and eosin stain (magnification 400).
patients with dysphagia, whereas graft removal and complete decompression were needed for patients with neurologic symptoms. Those complications could be attributed to the inability of BOP to achieve successful osteoconduction, as reported by several studies.12-14,16,19,20 In our case, neither fibrous ingrowth nor osteoblastic tissue was observed during the operation. The remaining BOP was easily separated and removed. Moreover, histologic findings also revealed that BOP showed some foreign body reaction and degeneration of normal bony tissues, without any evidence of new bone formation. Hafez et al.14 reported 3 patients who underwent
anterior cervical discectomy and BOP grafting needed repeated operations for recurrent symptoms 8, 10, and 30 months after insertion. They reported that the operative and histologic findings revealed that BOP did not conduct bone formation. Trevor et al.20 also reported that BOP was not osteoconductive within 6 months of placement because neither connective tissue nor bone ingrowth into BOP blocks was observed. In addition, previous studies demonstrated that BOP did not show any radiologic evidence of osteointegration or osteogenesis.12-14,16 Interestingly, in the case we report here, cervical surgery with use of BOP had been performed 23 years earlier. Although the
patient had been symptom free after surgery, myeopathic symptoms due to extrusion of the BOP occurred suddenly, without any history of trauma. To the best of our knowledge, this case represents the longest time to reoperation as a result of BOP extrusion in the literature, where reports range from 4 days to 30 months.14-17 It is plausible that BOP without incorporation or solid fusion can migrate and cause complications later, although the BOP could work as a spacer for some time. Therefore, close follow-up and monitoring are needed for patients treated with BOP grafts, even if they are asymptomatic. If patients present with neurologic symptoms because of extruded BOP, our experience and reports demonstrate that satisfactory clinical outcomes may be achieved through removal of the BOP and interbody fusion with the use of iliac bone grafts.14 CONCLUSIONS Spine surgeons should recognize the pathophysiology and possible complications of BOP in aspects of spinal fusion. In our case, BOP did not show any evidence of new bone formation or incorporation as a bone graft substitute. Patients who have previously undergone surgery in which BOP was used can present with related complications, even 23 years after surgery, as in our case. Because BOP did not conduct bone formation when used for
Table 1. Previous Case Reports of Biocompatible Osteoconductive Polymer Extrusion Study
Number of Patients
Presenting Symptoms
Time to Reoperation
Treatment
Outcome
Hafez et al., 199714
3
Neck pain with left arm pain Left brachalgia and leg stiffness Neck and arm pain
8, 10, and 30 months
Autogenous iliac graft and plate fixation
Immediate relief of neck and arm pain
Dorward et al., 199715
2
New symptom of left brachalgia Recurrent left brachalgia and arm weakness
4 and 6 weeks
Graft removal and decompression
One patient with permanent mild biceps weakness
Hynes et al., 199716
4
Dysphagia (4 patients) Lump and pain in throat (2), change in voice (1), and restriction of neck movement (1)
4 days to 6 months
Graft removal
Uncomplicated recovery in all cases
McLorinan et al., 200117
1
Laryngeal obstruction and pharyngeal perforation
10 months
Graft removal by use of emergency laryngoscopy
Successful pharyngeal healing and no vertebral collapse
Lin et al., 200318
1
Dysphagia at 26 months after surgery
48 months (No reoperation)
Spontaneous removal and feeding via nasogastric tube
No symptom of dysphagia
WORLD NEUROSURGERY 127: 249-252, JULY 2019
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CASE REPORT HYUNG-YOUL PARK ET AL.
spinal fusion surgery, we recommend revision surgery to achieve solid spinal fusion. REFERENCES 1. Weinstein JN, Lurie JD, Olson PR, Bronner KK, Fisher ES. United States’ trends and regional variations in lumbar spine surgery: 1992-2003. Spine (Phila Pa 1976). 2006;31:2707-2714. 2. Dimar JR 2nd, Glassman SD, Burkus JK, Pryor PW, Hardacker JW, Carreon LY. Two-year fusion and clinical outcomes in 224 patients treated with a single-level instrumented posterolateral fusion with iliac crest bone graft. Spine J. 2009;9:880-885. 3. Arrington ED, Smith WJ, Chambers HG, Bucknell AL, Davino NA. Complications of iliac crest bone graft harvesting. Clin Orthop Relat Res. 1996;Aug:300-309. 4. Fischer CR, Cassilly R, Cantor W, Edusei E, Hammouri Q, Errico T. A systematic review of comparative studies on bone graft alternatives for common spine fusion procedures. Eur Spine J. 2013;22:1423-1435. 5. Kim YH, Ha KY, Kim SI. Spinal cord injury and related clinical trials. Clin Orthop Surg. 2017;9:1-9. 6. Kaliya-Perumal AK, Ariputhiran-Tamilselvam SK, Luo CA, Thiagarajan S, Selvam U, SumathiEdirolimanian RP. Revalidating Pfirrmann’s magnetic resonance image-based grading of lumbar nerve root compromise by calculating reliability among orthopaedic residents. Clin Orthop Surg. 2018;10:210-215. 7. Buron F, Bourgois R, Burny F, et al. BOP: biocompatible osteoconductive polymer: An experimental approach. Clin Mater. 1994;16: 217-221.
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EXTRUDED BOP CAUSING CERVICAL MYELOPATHY
8. Skondia V, Davydov AB, Belykh SI, Heusghem C. Chemical and physicomechanical aspects of biocompatible orthopaedic polymer (BOP) in bone surgery. J Int Med Res. 1987;15:293-302.
16. Hynes JE, Weaver L, Jones RA, Cowie RA, Jackson A. Extrusion of osteoconductive biosynthetic polymer dowels after cervical fusion surgery. AJNR Am J Neuroradiol. 1997;18:792-793.
9. Ortolani E, Nazzicone M, Fratto G. Evaluation of biocompatible osteoconductive polymer activity and biocompatibility for minor oral surgery in animals and humans. J Int Med Res. 1991;19: 237-241.
17. McLorinan GC, Choudhari KA, Cooke RS. Life threatening complication of biocompatible osteoconductive polymer graft after anterior cervical discectomy. Br J Neurosurg. 2001;15:363-365.
10. Lozes G, Fawaz A, Cama A, et al. Discectomies of the lower cervical spine using interbody biopolymer (B.O.P.) implants. Advantages in the treatment of complicated cervical arthrosis: A review of 150 cases. Acta Neurochir (Wien). 1989;96: 88-93. 11. Lozes G, Fawaz A, Mescola P, et al. Percutaneous interbody osteosynthesis in the treatment of thoracolumbar traumatic or tumoural lesions: A review of 51 cases. Acta Neurochir (Wien). 1990;102: 42-53. 12. Madawi AA, Powell M, Crockard HA. Biocompatible osteoconductive polymer versus iliac graft: A prospective comparative study for the evaluation of fusion pattern after anterior cervical discectomy. Spine (Phila Pa 1976). 1996;21:2123-2129 [discussion: 2129-2130]. 13. Ibanez J, Carreno A, Garcia-Amorena C, Caral J, Gaston F, Ferrer E. Results of the biocompatible osteoconductive polymer (BOP) as an intersomatic graft in anterior cervical surgery. Acta Neurochir (Wien). 1998;140:126-133. 14. Hafez RF, Crockard HA. Failure of osseous conduction with cervical interbody BOP graft. Br J Neurosurg. 1997;11:57-59. 15. Dorward NL, Malik NN, Illingworth RD. Disintegration of cervical intervertebral BOP grafts with neurological sequelae: A report of two cases. Br J Neurosurg. 1997;11:65-68.
18. Lin TJ, Huang FC, Chang CK. Complication of an interbody biopolymer graft extruded orally after anterior cervical discectomy and fusion. J Clin Neurosci. 2003;10:629-631. 19. Lussier B, Lanthier T, Martineau-Doize B. Evaluation of biocompatible osteoconductive polymer shelf arthroplasty for the surgical correction of hip dysplasia in normal dogs. Can J Vet Res. 1994;58: 173-180. 20. Trevor PB, Stevenson S, Carrig CB, Waldron DR, Smith MM. Evaluation of biocompatible osteoconductive polymer as an orthopedic implant in dogs. J Am Vet Med Assoc. 1992;200:1651-1660.
Conflict of interest statement: This work was supported by Small Grant for Exploratory Research (SGER) through the Ministry of Education of the Republic of Korea and The Catholic University of Korea Songeui (NRF2018R1D1A1A02049202). Received 6 March 2019; accepted 3 April 2019 Citation: World Neurosurg. (2019) 127:249-252. https://doi.org/10.1016/j.wneu.2019.04.033 Journal homepage: www.journals.elsevier.com/worldneurosurgery Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2019 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2019.04.033
Extrusion of Biocompatible Osteoconductive Polymer (BOP) Causing Cervical Myelopathy Hyung-Youl Park1, Young-Hoon Kim2, Kee-Yong Ha2, Sang-Il Kim2, Kee-Won Rhyu4, Joon-Hyuck Oh4, Chan-Kwon Jung3
Key words Polymethylmethacrylate-N-vinylpyrrolidone - Reoperation - Spinal cord compression - Spinal fusion -
Abbreviations and Acronyms BOP: Biocompatible osteoconductive polymer CT: Computed tomography MRI: Magnetic resonance imaging From the 1Department of Orthopedic Surgery, Eunpyeong St. Mary’s Hospital; Departments of 2Orthopedic Surgery and 3 Hospital Pathology, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, and 4 Department of Orthopedic Surgery, St. Vincent Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea To whom correspondence should be addressed: Young-Hoon Kim, M.D., Ph.D. [E-mail: [email protected]] Supplementary digital content available online. Citation: World Neurosurg. (2019) 127:249-252. https://doi.org/10.1016/j.wneu.2019.04.033 Journal homepage: www.journals.elsevier.com/worldneurosurgery Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2019 Elsevier Inc. All rights reserved.
INTRODUCTION As the prevalence of spinal fusion surgery has increased, the focus on bone graft alternatives has also increased.1 Whereas autologous bone grafts remain the criterion standard, efforts to develop reliable and safe bone graft substitutes have been carried out to prevent the morbidities and complications related to obtaining autologous bone graft material.2,3 Although approximately 1400 products are available for use as bone graft substitutes, they should be evaluated to confirm their safety and efficacy as materials for solid fusion.4,5 Biocompatible osteoconductive polymer (BOP) is an example of such an important lesson. We present a case of extruded BOP and discuss the
- BACKGROUND:
As the prevalence of spinal fusion surgery has increased, reliable and safe bone graft substitutes have been developed in response. Biocompatible osteoconductive polymer (BOP) has been used as a bone graft alternative for spine surgery. We present a case of cervical myelopathy due to extrusion of BOP 23 years after surgery and discuss the pathophysiology in terms of spinal fusion.
- CASE
DESCRIPTION: A 65-year-old man presented with a 3-month history of cervical myelopathic symptoms. Twenty-three years earlier, the patient had undergone cervical surgery for a C6e7 herniated disc with the use of BOP. Imaging studies of the cervical spine showed cord compression due to extruded BOP at C6e7. He underwent corpectomy of the C7 vertebral body and removal of the BOP for the neural decompression, combined with interbody fusion by use of an iliac bone graft and plate fixation. During the operation, crumbly fibers of the BOP were easily removed. His myelopathic symptoms improved immediately after surgery. Postoperative magnetic resonance imaging also showed successful decompression of the spinal cord. Histologically, a foreign body reaction and bony degeneration were found around the synthetic fibers of the BOP.
- CONCLUSIONS:
Spine surgeons should recognize the pathophysiology of the BOP used for spine fusion surgery. Although BOP is not currently used for spinal surgery, patients undergoing previous surgery with the BOP can present with related complications. Revision surgery is recommended to remove the unincorporated BOP and achieve solid spine fusion.
pathophysiology of BOP in aspects of spinal fusion. CASE REPORT A 65-year-old man presented with right shoulder pain and gait disturbances, which had become aggravated over 3 months. He had undergone cervical anterior surgery for a C6e7 disc herniation 23 years earlier at another hospital. At his initial visit to our hospital, the patient reported that an artificial disc had been used for the surgery. On physical examination, he had a sensory disturbance in the little finger, and his patellar tendon reflex was exaggerated. He did not have motor weakness, and the Hoffmann sign was negative. Magnetic resonance imaging (MRI) of the
WORLD NEUROSURGERY 127: 249-252, JULY 2019
cervical spine revealed that graft material with low signal intensity on T2-weighted image was compressing the cord, resulting in signal changes mainly on the right side (Figure 1A).6 Computed tomography (CT) of the cervical spine showed that radiolucent material was extruded into spinal canal, with marginal sclerosis (Figure 1B). The patient underwent surgery for cervical myelopathy caused by extruded graft material. Although he had no hoarseness or dysphagia after the previous surgery conducted on the left side, we approached the index level on the right side to avoid postoperative adhesion. The operative findings revealed that some separated fibers were also extruded ventrally, causing severe adhesion around the esophagus. We performed careful dissection of the
www.journals.elsevier.com/world-neurosurgery
249
CASE REPORT HYUNG-YOUL PARK ET AL.
EXTRUDED BOP CAUSING CERVICAL MYELOPATHY
Figure 1. Cervical compressive myelopathy due to extruded biocompatible osteoconductive polymer (BOP). (A) Magnetic resonance image revealing BOP compression of the cord showing signal changes (arrowhead) on right side. (B) Computed tomographic view showing extrusion of radiolucent material into spinal canal, with marginal sclerosis.
interbody arthrodesis and decompression esophagus and removal of graft fragof the spinal cord (Figure 2). The patient ments. Huge extruded grafts were not reported no shoulder pain and gait easily removed, even after the C6e7 disdisturbance at his 1-year follow-up visit. cectomy and removal of fragments. After The BOP fragments taken during surthe C7 corpectomy and additional C6e7 gery were examined histologically. The foraminotomy, complete decompression microscopic findings revealed and removal of graft materials some inflammatory cells, was achieved (Supplementary including multinucleated Video 1). We conducted the foreign bodyetype giant cells, C6eT1 interbody fusion among the polymers. Moreusing autologous iliac bone over, degeneration of normal grafts and plate fixation. The Video available at www.sciencedirect.com bony tissue, rather than new removed grafts were easily bone formation, was found disrupted into separable around the BOP fibers (Figure 3). fibers. After the surgery, we identified the graft materials as the BOP from previous surgery at another hospital. The DISCUSSION patient reported improvement in his right shoulder pain immediately after the The BOP consists of 50% polyamide-6 fisurgery and was able to ambulate on the bers, 40% matrix (copolymer N-vinylsecond postoperative day without gait pyrorolidone and methylmethacrylate), disturbance. Postoperative radiographs and 10% calcium gluconate. BOP was and MRI also showed successful developed and has been used as a spacer
Figure 2. Postoperative imaging after revision surgery. (A) Plain radiographs revealing interbody fusion with autogenous iliac bone and plate fixation. (B) Magnetic resonance image showing successful decompression of spinal cord.
250
www.SCIENCEDIRECT.com
for osteosynthesis and filling of bone defects since the 1970s.7 Then, Skondia et al.8 reported that BOP could be used not only as a spacer for bone filling and reconstructive surgery but also as intramedullary rods, owing to the enhanced mechanical characteristics of the polymer, such as ingrowth of fibrous tissue. Ortolani et al.9 also demonstrated that new bony tissue was incorporated into the BOP histologically in animal models, and more bone regeneration was observed radiographically in human patients treated with BOP after molar extraction. It was suggested that osteoblastic activity, coupled with an osteoclastic reaction, may have resulted in partial fragmentation of the polyamide fibers and their incorporation into the newly formed bone.7 The use of BOP for spine surgery has been reported since the late 1980s. Lozez et al.10,11 reported the use of BOP for bone graft complements and interbody grafts in the arthrodesis of the spine. Owing to the increasing use of BOP for cervical spine surgery, commercial products of BOP (DTI Med. Corporation, Fleurus, Belgium) for the cervical spine were developed in 2 forms: BOP-B block for Smith-Robinson procedures and BOP B-octa for Cloward procedures.12 However, the clinical outcomes after the use of BOP for cervical surgery were not satisfactory. Madawi et al.12 conducted a prospective comparative study between BOP and iliac grafts on 115 patients. They reported that BOP did not show any radiologic evidence of biodegradation or incorporation, despite similar clinical outcomes seen with the iliac graft. Ibanez et al.13 also reported that BOP, used as intervertebral grafts in anterior cervical surgery showed significantly higher graft complications and worse bone fusion, compared with heterologous bovine grafts, although the clinical outcomes were similar. Moreover, reports of complications related to the use of BOP for cervical spine surgery have increased (Table 1).14-18 Symptoms can differ depending on the direction of the extrusion. The anterior extrusion of BOP caused dysphagia, and neurologic symptoms developed in the cases of posterior extrusion. As treatments for these conditions, removal of extruded BOP was effective for
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2019.04.033
CASE REPORT HYUNG-YOUL PARK ET AL.
EXTRUDED BOP CAUSING CERVICAL MYELOPATHY
Figure 3. Histologic findings around the biocompatible osteoconductive polymer (BOP). (A) Multinucleated foreign bodyetype giant cells (arrowhead) among the polymers. (B) Degeneration of normal bony tissue (arrow) around the fibers of BOP (arrowhead). Hematoxylin and eosin stain (magnification 400).
patients with dysphagia, whereas graft removal and complete decompression were needed for patients with neurologic symptoms. Those complications could be attributed to the inability of BOP to achieve successful osteoconduction, as reported by several studies.12-14,16,19,20 In our case, neither fibrous ingrowth nor osteoblastic tissue was observed during the operation. The remaining BOP was easily separated and removed. Moreover, histologic findings also revealed that BOP showed some foreign body reaction and degeneration of normal bony tissues, without any evidence of new bone formation. Hafez et al.14 reported 3 patients who underwent
anterior cervical discectomy and BOP grafting needed repeated operations for recurrent symptoms 8, 10, and 30 months after insertion. They reported that the operative and histologic findings revealed that BOP did not conduct bone formation. Trevor et al.20 also reported that BOP was not osteoconductive within 6 months of placement because neither connective tissue nor bone ingrowth into BOP blocks was observed. In addition, previous studies demonstrated that BOP did not show any radiologic evidence of osteointegration or osteogenesis.12-14,16 Interestingly, in the case we report here, cervical surgery with use of BOP had been performed 23 years earlier. Although the
patient had been symptom free after surgery, myeopathic symptoms due to extrusion of the BOP occurred suddenly, without any history of trauma. To the best of our knowledge, this case represents the longest time to reoperation as a result of BOP extrusion in the literature, where reports range from 4 days to 30 months.14-17 It is plausible that BOP without incorporation or solid fusion can migrate and cause complications later, although the BOP could work as a spacer for some time. Therefore, close follow-up and monitoring are needed for patients treated with BOP grafts, even if they are asymptomatic. If patients present with neurologic symptoms because of extruded BOP, our experience and reports demonstrate that satisfactory clinical outcomes may be achieved through removal of the BOP and interbody fusion with the use of iliac bone grafts.14 CONCLUSIONS Spine surgeons should recognize the pathophysiology and possible complications of BOP in aspects of spinal fusion. In our case, BOP did not show any evidence of new bone formation or incorporation as a bone graft substitute. Patients who have previously undergone surgery in which BOP was used can present with related complications, even 23 years after surgery, as in our case. Because BOP did not conduct bone formation when used for
Table 1. Previous Case Reports of Biocompatible Osteoconductive Polymer Extrusion Study
Number of Patients
Presenting Symptoms
Time to Reoperation
Treatment
Outcome
Hafez et al., 199714
3
Neck pain with left arm pain Left brachalgia and leg stiffness Neck and arm pain
8, 10, and 30 months
Autogenous iliac graft and plate fixation
Immediate relief of neck and arm pain
Dorward et al., 199715
2
New symptom of left brachalgia Recurrent left brachalgia and arm weakness
4 and 6 weeks
Graft removal and decompression
One patient with permanent mild biceps weakness
Hynes et al., 199716
4
Dysphagia (4 patients) Lump and pain in throat (2), change in voice (1), and restriction of neck movement (1)
4 days to 6 months
Graft removal
Uncomplicated recovery in all cases
McLorinan et al., 200117
1
Laryngeal obstruction and pharyngeal perforation
10 months
Graft removal by use of emergency laryngoscopy
Successful pharyngeal healing and no vertebral collapse
Lin et al., 200318
1
Dysphagia at 26 months after surgery
48 months (No reoperation)
Spontaneous removal and feeding via nasogastric tube
No symptom of dysphagia
WORLD NEUROSURGERY 127: 249-252, JULY 2019
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251
CASE REPORT HYUNG-YOUL PARK ET AL.
spinal fusion surgery, we recommend revision surgery to achieve solid spinal fusion. REFERENCES 1. Weinstein JN, Lurie JD, Olson PR, Bronner KK, Fisher ES. United States’ trends and regional variations in lumbar spine surgery: 1992-2003. Spine (Phila Pa 1976). 2006;31:2707-2714. 2. Dimar JR 2nd, Glassman SD, Burkus JK, Pryor PW, Hardacker JW, Carreon LY. Two-year fusion and clinical outcomes in 224 patients treated with a single-level instrumented posterolateral fusion with iliac crest bone graft. Spine J. 2009;9:880-885. 3. Arrington ED, Smith WJ, Chambers HG, Bucknell AL, Davino NA. Complications of iliac crest bone graft harvesting. Clin Orthop Relat Res. 1996;Aug:300-309. 4. Fischer CR, Cassilly R, Cantor W, Edusei E, Hammouri Q, Errico T. A systematic review of comparative studies on bone graft alternatives for common spine fusion procedures. Eur Spine J. 2013;22:1423-1435. 5. Kim YH, Ha KY, Kim SI. Spinal cord injury and related clinical trials. Clin Orthop Surg. 2017;9:1-9. 6. Kaliya-Perumal AK, Ariputhiran-Tamilselvam SK, Luo CA, Thiagarajan S, Selvam U, SumathiEdirolimanian RP. Revalidating Pfirrmann’s magnetic resonance image-based grading of lumbar nerve root compromise by calculating reliability among orthopaedic residents. Clin Orthop Surg. 2018;10:210-215. 7. Buron F, Bourgois R, Burny F, et al. BOP: biocompatible osteoconductive polymer: An experimental approach. Clin Mater. 1994;16: 217-221.
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EXTRUDED BOP CAUSING CERVICAL MYELOPATHY
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Conflict of interest statement: This work was supported by Small Grant for Exploratory Research (SGER) through the Ministry of Education of the Republic of Korea and The Catholic University of Korea Songeui (NRF2018R1D1A1A02049202). Received 6 March 2019; accepted 3 April 2019 Citation: World Neurosurg. (2019) 127:249-252. https://doi.org/10.1016/j.wneu.2019.04.033 Journal homepage: www.journals.elsevier.com/worldneurosurgery Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2019 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2019.04.033