The use of porous tantalum cages in the treatment of unremitting spondylodiscitis 41 Klinični primer Division of Surgery, Department of Orthopaedics, University medical Centre maribor, maribor, Slovenia Korespondenca/ Correspondence: Samo Karel Fokter, e: samo.fokter@guest.arnes. si Ključne besede: kirurgija hrbtenice; vnetje hrbtenice; kostna zatrditev hrbtenice; kletka iz poroznega tantala; piogeni spondilodiscitis Key words: spinal surgery; spinal infection; spinal bone fusion; porous tantalum cage; pyogenic spondylodiscitis prispelo: 23. 4. 2017 Sprejeto: 15. 9. 2017 The use of porous tantalum cages in the treatment of unremitting spondylodiscitis: a case report Uporaba kletk iz poroznega tantala pri zdravljenju trdovratnega spondilodiscitisa: opis primera Samo Karel Fokter, Gregor Rečnik Abstract Background: Unsuccessful medical treatment of pyogenic multifocal spondylodiscitis including signs of sepsis and unremitting pain is challenging. The aim of our report was to present a case of multilevel spondylodiscitis successfully treated by posterior lumbar interbody fusion using porous tantalum cages. Case presentation: A 59-year-old male was diagnosed with spondylodiscitis at T8-T9 level. Although treated with antibiotics, the patient again presented with worsening of systemic signs of infection and back pain. Contrast-enhanced magnetic resonance imaging studies revealed spondylodiscitis at L1 to S1 level. Posterior lumbar interbody bone fusion with tantalum cages from L1 to S1 was performed. The inflammation rapidly subsided. Computer tomography studies showed a stable construct at 24 months. Conclusion: Porous tantalum cages used in combination with transpedicular fixation seem to be a sound alternative to interbody devices made from other materials when treating spondylodi- scitis cases without definite osseous destruction. Izvleček Izhodišče: Zdravljenje neodzivnega piogenega večžariščnega spondilodiscitisa s trdovratno bo- lečino in znaki sepse je zahtevno. Namen našega poročila je predstaviti primer uspešno zdrav- ljenega večnivojskega spondilodiscitisa ledvene hrbtenice z medvretenčno kostno zatrditvijo ob souporabi kletk iz poroznega tantala. Prikaz primera: Pri 59-letnem moškem smo dokazali spondilodiscitis segmenta T8-T9. Kljub zdravljenju z antibiotiki je pri bolniku prišlo do poslabšanja sistemskih znakov okužbe in bolečin. Slikanje z magnetno resonanco in kontrastnim sredstvom je pokazalo spondilodiscitis od nivoja L1 do S1. Izvedli smo posteriorno ledveno medvretenčno kostno zatrditev od L1 do S1 in pri tem uporabili tantalove medvretenčne kletke. Vnetje se je hitro umirilo. Z računalniško tomografijo smo 24 mesecev po operaciji dokazali stabilno konstrukcijo. Zaključek: Porozne kletke iz tantala v kombinaciji s transpedikularno fiksacijo se najverjetneje lahko podobno kot medvretenčni vsadki iz drugih materialov uporabljajo pri zdravljenju prime- rov spondilodiscitisa brez jasne kostne razgradnje. Citirajte kot/Cite as: Fokter SK, rečnik G. The use of porous tantalum cages in the treatment of unremitting spondylodiscitis: a case report. Zdrav Vestn. 2018;87(1–2):41–8. DOI: 10.6016/ZdravVestn.2596 42 Zdrav Vestn | januar – februar 2018 | letnik 87 neVrobioloGija 1.  Background Spondylodiscitis is an infection which affects the intervertebral disk space and the vertebral body of the associated ver- tebra. Haematogenous pyogenic spon- dylodiscitis affects preferentially the lu- mbar spine, followed by the thoracic and the cervical spine; a multifocal infection is very rare (1,2). Staphylococcus aureus (S.aureus) is the predominant pathogen in pyogenic spondylodiscitis (3). Medical management with an appropriate antibi- otic combination is the first choice for eradicating the infection and alleviating pain. Debridement of the affected disc and decompression of the spinal cord followed by transpedicular instrumenta- tion through a posterior approach with autologous bone grafting and drainage is indicated in case of an epidural ab- scess in the lumbar spine. Unsuccessful medical treatment, including severely ill patient with signs of sepsis and/or unre- mitting pain, is also an indication for surgery (4). Titanium mesh cages com- bined with pedicle screw instrumentati- on have been introduced for single-sta- ge anterior surgical debridement and reconstruction in the thoracolumbar spine (5,6), and polyether ether ketone (PEEK) cages proved to be reliable in treating spondylodiscitis of the cervical spine (7). We present a case of a 59-ye- ar-old man with refractory spondylodi- scitis of the lumbar spine treated by the insertion of porous tantalum cages at 5 consecutive levels for anterior support in addition to standard transpedicular fixation after thorough surgical decom- pression and debridement. 2.  Case presentation A 59-year-old male first presented with a one-week history of thoracic pain. His erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) values were elevated (ESR = 55 mm/h; CRP = 104 mg/l) and S. aureus was cultivated from his blood culture. Contrast-enhanced magnetic resonan- ce imaging (MRI) of the thoracic spi- ne revealed signs of spondylodiscitis at T8-T9. Fluoroscopically guided needle biopsy, which was still practiced at our institution at that time, revealed the same bacteria species and intravenous antibiotic treatment was started (cloxa- cillin 2 g/6 h). Patient’s pain has gradu- ally resolved, ESR and CRP values have dropped significantly (ESR = 38 mm/h; CRP = 6 mg/l) and endocarditis was ruled out. In accordance with consul- ted infectious diseases specialist, the patient was discharged from the de- partment after 4 weeks and switched to per os antibiotic treatment (ciprofloxacin 750 mg/12 h) for additional 4 weeks. The patient was fully compliant with the tre- atment. Eight weeks after discharge the pati- ent was readmitted because of fever, ma- laise, and lower back pain. Orthopaedic examination revealed severely impaired mobility of the lumbar spine, a bilaterally positive straight leg raise test and no ne- urologic impairments. Patient’s ESR and CRP values were 89 mm/h and 225 mg/l respectively, and S. aureus was cultivated again from his blood culture. An intrave- nous antibiotic combination (cloxacillin 2 g/6 h and ciprofloxacin 400 mg/12 h) was introduced immediately. Contrast- enhanced MRI of the thoracic and lu- mbar spine showed oedema regression at T8-T9 level and new oedema forma- tion in the vertebral bodies L1 and L2 without the intervertebral disc involve- ment. Ultrasonography of the heart was performed and no signs of endocarditis were found. The patient experienced The use of porous tantalum cages in the treatment of unremitting spondylodiscitis 43 Klinični primer pain persistence. ESR and CRP valu- es remained elevated (ESR = 95 mm/h; CRP = 186 mg/l). Swelling of his left an- kle and right radiocarpal joint appeared; however, both aspirates were negative. S. aureus was cultivated again from his blood cultures. Repetitive contrast-en- hanced MRI of the thoracic and lumbar spine revealed no dynamics at T8-T9 level and showed enhanced oedema of the vertebral bodies L2, L4, L5, at L1-L2 and L5-S1 disc levels, and soft tissues (Figure 1). After 3 weeks of medical ma- nagement the patient was still unable to walk due to sharp back pain which was hard to tolerate despite the use of nar- cotic analgesics. His ESR and CRP levels remained elevated. Infectious disease specialist concluded that the patient’s septic state was not under control and he was brought to the operating theatre. Wide surgical debridement and decompression with laminectomy were performed through posterior approa- ch from L1 to L5. Frank pus was found in the paravertebral soft tissue, epidural space and in the discs L1-L2, L4-L5 and L5-S1, and the material obtained was sent for cultures separately. The discs L2- L3 and L3-L4 were carefully opened and the soft liquid material obtained under pressure was also sent for cultures. It was obvious from the local surgical finding that continuous segments were engaged in the inflammatory disease. The lumbar spine was thus stabilized by transpedi- cular instrumentation from L1 to S1 with titanium screws and rods, disc spaces were cleaned and porous tantalum cages (TM Ardis™ Interbody System, Zimmer, Warsaw, Indiana, USA) were inserted. Two cages per segment were used at two lower lumbar levels (L4-L5 and L5-S1) for a larger foot-print, and one cage per segment was used at three upper levels (L1-L2, L2-L3 and L3-L4). Taken together, 7 porous tantalum cages were inserted. With the help of a compression device, the construct was fixed in appropriate lumbar lordosis, the wound was thoro- ughly washed with saline, drained and closed-up in layers. Surgically-taken bio- psy showed S. aureus growth from para- vertebral soft tissue, epidural tissue and all involved intervertebral spaces. Postoperative course was uneventful, drainage was left in place for 72 hours and at that time rifampicin 450 mg/12 h orally was added. One week after sur- gery, ciprofloxacin treatment was di- scontinued. On day 16, when ESR and CRP values have dropped significan- tly, cloxacillin treatment was replaced Figure 1: T2 weighted MRI of lumbar spine showing signs of spondylodiscitis from L1 to S1 level. 44 Zdrav Vestn | januar – februar 2018 | letnik 87 neVrobioloGija with oral trimetoprim-sulfametoxa- sole (160 mg/800 mg every 8 hours) in accordance with the antibiogram of the causative microorganism and the pati- ent was discharged. He stayed on com- bined antibiotic treatment (rifampicin and trimetoprim-sulfametoxasole) for 12 weeks and was followed clinically and radiologically for 24 months. The pati- ent was pain free and his ESR and CRP values were normal (ESR = 16 mm/h; CRP = 6 mg/l). Standard X-rays at the final follow-up showed spontaneous fu- sion at segment T8-T9 and fusion with subsidence of the cage at L1-L2 thro- ugh upper end-plate of L2 (Figure 2). Computed tomography (CT) scan at 24-month follow-up showed signs of stable fixation from L1 to S1 but failed to show signs of solid bone fusion at levels lower than L1-L2. 3.  Discussion Antimicrobial therapy has been a mainstay when treating patients with spondylodiscitis with generally favo- rable results and over 90 % cure rate in population without concomitant endo- carditis (8). Intravenous therapy with flucloxacillin is the standard mode of treatment for S. aureus spondylodisci- tis, but a conversion to oral bacterici- dal drugs as early as 2 weeks has also been associated with similarly good ou- tcomes (9). An infectious disease speci- alist has thus prescribed to our patient fluroquinolones that show excellent per oral bioavailability. However, studies suggest that rapid emergence of resistance to these drugs precludes their use as single agents aga- inst S. aureus, which might have contri- buted to failure of our initial treatment even though it exceeded the recommen- ded 6 weeks (10). If rifampicin were added to fluoroquinolone (preferably levofloxacin), the spread of the infecti- on might have been prevented, unsa- tisfactory response to drug therapy av- oided and surgical intervention would probably not be needed. An alternative to this treatment regime could be clin- damycin (10). Porous tantalum is an open-cell me- tal structure with overall porosity of 80 % that approximates the appearance of human cancellous bone. Open-pore structure facilitates osteointegration, bone modeling, and vascularization. The material has a low modulus of elastici- ty, leading to better load transfer and minimizing the stress-shielding pheno- menon. Its coefficient of friction is one Figure 2: Lateral X-ray of the lumbar spine at 2-year follow-up. The use of porous tantalum cages in the treatment of unremitting spondylodiscitis 45 Klinični primer of the highest among biomaterials, al- lowing sufficient primary stabilization of implants (11). Sagomonyants et al. have shown that porous tantalum stimulates proliferation and osteogenesis of osteob- lasts (12). Due to its unique properties, it has been successfully used in cervical and in a variety of lumbar spine proced- ures as a sound interbody device (13). In cases of bacterial spondylodiscitis, the instrumentation screws, rods and ca- ges can be colonized and covered with a biofilm. However, the risk of using spi- nal instrumentation after debridement is low since only a few colonies adhere to the stainless steel or titanium made de- vices (14). Calvert et al. recently reported on 15 patients treated for spondylodi- scitis with implanted expandable metal cages (15). All patients had clinical reso- lution of infection with an average fol- low-up time of 25 months. Radiograph review revealed no extensive osteolysis around the hardware or progressive co- llapse. The authors concluded that the spine appears to provide a unique envi- ronment that permits the use of metal implants in the setting of infection (15). Walter et al. have shown that PEEK cages, popular in degenerative cases, can also be used safely for implants in cases of cervical spondylodiscitis (16). Schomacher et al. have compared the re- sults of treatment of pyogenic spondylo- discitis with titanium or PEEK cages in addition to 3 month antibiotic therapy and found no reinfection in either gro- up (17). However, a cage subsidence was observed in 70.3 % of all cases. The authors concluded that debridement and fixation with anterior column support in combination with antibiotic therapy appear to be the key points for successful treatment of pyogenic spondylodiscitis and that the application of titanium or PEEK cages does not appear to influence the radiological outcome. The surgical treatment for pyogenic spondylodiscitis should be considered in patients with significant bone destru- ctions, impending fractures, progressi- ve spinal deformities, neurological im- pairments, antibiotic-resistant sepsis, recurrent infections and/or epidural abscesses (18-21). In our case, the indi- cation for surgery was an antibiotic-re- sistant septic state. Significant progress of the inflammatory process was obser- ved at surgery compared to the involve- ment shown on contrast-enhanced MRI a week earlier, when no changes at L2-L3 and L3-L4 disc levels have been obser- ved. There are several other drawbacks of our case report. To start with, no preope- rative local biopsy was performed for di- agnosis confirmation after the spread of infection to the lumbar spine. However, several blood cultures revealed S. aureus septicemia and the focus was clearly visi- ble on MRI. Secondly, wide laminectomy could potentially result in the spread of the infection to the epidural space. In our case, the infection was already pre- sent in the epidural space, making lami- nectomy, radical debridement, wash-out and drainage seem obligatory. In additi- on, long fusion has increased the chance of complications and pseudoarthrosis. An option would therefore be to fuse only the most involved segments, in our case L1-L2 and L5-S1 segments. However, according to surgical findings at explo- ration, continuous segments were en- gaged in the inflammatory disease. Left untreated, these segments could possibly lead to further disease propagation ne- cessitating repetitive surgical explorati- ons. Moreover, if left unfused, diseased central lumbar segments in combination with posterior element disruption du- ring laminectomy could rapidly progress to adjacent segment disease. Stable en- vironment is a condition which helps to 46 Zdrav Vestn | januar – februar 2018 | letnik 87 neVrobioloGija eradicate a spinal infection and it is ea- siest to achieve with hardware fixation. Furthermore, we could have conti- nued with non-operative management of the patient for a considerable amo- unt of time since there was no abscess formation or neurological impairment. Nevertheless, in this particular case, the burden of the infectious agent seemed to be too large for the patient’s immune system to tolerate and we were not able to control the disease with antibiotics alone. Conservative treatment consi- sting of long-term bed rest and antibi- otic intravenous regimen could have detrimental effects on the overall health status of the patient, entailing not only generalized muscle wasting but also the possibility of pneumonia, vein thrombo- sis or regional pressure ulcers. Minimally invasive screw fixation with limited focal debridement offers an alternative even in the most morbid group of patients, pro- viding the patient with early ambulatory activity while minimizing the drawbacks of open spine surgery. In the end, the manufacturer sta- tes that active local infection in or near operative region represents a contrain- dication for the use of the TM Ardis™ Interbody System. This is a standard warning regarding the implantation of any orthopaedic implant, it is thus im- portant to note that we have used the implant officially off-label. Other autho- rs have used orthopaedic implants made from titanium and/or PEEK material to successfully treat pyogenic osteomye- litis of thoracic and lumbar spine actu- ally off-label (18). An attempt has been made to clean up all the infected tissue and stabilize the patient’s spine, thereby optimizing its healing potential. This was only possible with hardware implantati- on. Lastly, no postoperative contrast- -enhanced MRI was performed to show resolution of the infection. However, the clinical course after surgery was uneven- tful and evaluation of an MRI after spine surgery with metallic hardware inserted is sometimes difficult to interpret. Posterior instrumentation combined with autologous bone grafting repre- sents the standard treatment for patients with pyogenic spondylodiscitis of the lumbar spine. Many authors have repor- ted about the safety of harvesting bone grafts in these patients (19-24). Chou et al. have shown that intervertebral tita- nium and PEEK implants could be safely used as an alternative (25). We did not feel comfortable obtaining autologous bone grafts in our septic patient because we were afraid of spreading the infecti- on. Lack of evidence of bone fusion at all treated levels, apart from L1-L2 where the cage subsided and end plates could come into contact, e.g. sentinel sign on X-rays and CT scans at final follow-up, may be the result of this treatment mo- dification. The producer also advises the use of the devices in combination with autologous bone graft and states that fa- ilure to properly fill and/or compress the graft material into the area surrounding the implant may result in delayed hea- ling and/or non-union which can lead to fracture or breakage of the implant. Since this was not the case, bone might have grown through the porous structu- re of the device. Unfortunately, this cou- ld only be proved by histologic examina- tion of the explanted implant. Although debridement and necrotic tissue excision has been the mainstay of treating patients with spondylodiscitis, providing a stable environment by fixati- on alone has been shown by Mohamed et al. to provide comparable efficiency (26). Long-segment fixation without formal debridement resulted in resolution of spinal infection in all 15 observed cases, making the authors believe this surgical technique, when combined with aggressi- The use of porous tantalum cages in the treatment of unremitting spondylodiscitis 47 Klinični primer ve antibiotic therapy and a multidiscipli- nary team approach, is an effective way of managing serious spinal infections in a challenging patient population. 4.  Conclusion To the best of our knowledge, porous tantalum cages have not been used in the treatment of pyogenic lumbar spondylo- discitis. 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