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ABSTRACT

Introduction: The treatment of vertebral osteomyelitis includes antibiotics with or without surgical intervention. Debridement is warranted for the treatment of idiopathic spondylo-discitis in case of neurological deficits, deformity, instability, abscess formation, intractable pain or failure of medical management. The use of instrumentation is still controversial.

Objective: Is to evaluate the surgical outcome of idiopathic lumbar spondylodiscitis treated with posterior debridement combined with single-stage posterior instrumentation and autologus bone grafting.

Methods: This retrospective study was conducted to evaluate the outcome of 15 cases of idiopathic lumbar spondylo-discitis treated with posterior debridement combined with single-stage posterior instrumentation and grafting. All patients were followed up for up to 1 year post-operative. We evaluated operative time, blood loss, and complications. Visual analogue scale (VAS), activities of daily living (ADL) (Barthel index), C reactive proteins (CRP), and Erythrocyte sedimentation rate (ESR) in the preoperative, postoperative and final follow-up periods were used to evaluate the surgical outcome.

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Results: All 15 cases of lumbar infections resolved without recurrence. Bony union was obtained in all cases. Twelve out of 15 patients (80%) were completely relieved of pain and fully active with improvement neurological deficits, while the other 3 patients (20%) obtained a good result. No post-operative major complications were reported among the studied group. There were two superficial infections, which healed with debridement and antibiotics.

Conclusion: According to the results reported in this short study, the proposed technique is an effective and safe treatment for idiopathic lumbar spondylo-discitis, if surgery is mandatory.

Keywords: spondylo-discitis, debridement, posterior fixation.

INTRODUCTION

The increasing number of spinal infections has become a global health concern. It is currently due to reactivation of latent infections, more drug resistant agents and more immuno-compromised patients. It has been shown that delay in diagnosis can lead to increased morbidity and mortality, early diagnosis and treatment are therefore of paramount importance.(1)

Spinal infections encompass a spectrum of conditions comprising spondylitis, discitis, spondylodiscitis, pyogenic facet arthropathy, epidural infection, meningitis, polyradiculopathy and myelitis. All of these have a specific presentation and clinical course.(2)

Osteomyelitis of the spine accounts for approximately 1 to 7% of all osseous infections. In recent years, there have been an increasing incidence of spinal infections, which is now estimated to occur in approximately 1/100,000 individuals annually. This rise may be attributed to the increasing prevalence of elderly and immuno-compromised individuals in the population.(3)

The predominant organism in almost all studies is Staphylococcus aureus, accounting for approximately 40 to 80% of all spinal infections. Other Gram-positive organisms such as S. epidermidis and Streptococcus species are also common.(4)

Establishing the diagnosis of vertebral osteomyelitis in a timely fashion is critical to preventing catastrophic neurological injury. In the modern imaging era, magnetic resonance imaging, in particular, has facilitated the diagnosis of osteomyelitis even before the onset of neurological signs or symptoms. Nevertheless, despite advancements in diagnosis, there remains disagreement regarding appropriate treatment. Antibiotics are the main- stay of therapy.(5)

The treatment of pyogenic spondylodiscitis with intravenous antibiotics is universally agreed upon. More than 75% of patients can be treated with intravenous antibiotics and immobilization.(6)

Although no difference in clinical outcomes has been observed when comparing antibiotics alone with antibiotics plus surgical debridement, debridement of infected and dead tissue removes the source of continuing sepsis, may allow shorter courses of antibiotic treatment and may also allow early mobilization of the patient.(7)

Surgery is generally reserved for patients with neurological involvement, spinal instability, severe deformity, and/or those in whom antibiotics alone have not been effective. Current surgical treatment options include anterior or posterior decompression with or without fusion, and with or without instrumentation. The fact that there exist several alternative surgical approaches highlights the lack of a consensus on the optimal operative treatment for vertebral osteomyelitis. The decision to place instrumentation into an infected spinal column remains controversial. Numerous authors have shown that instrumentation in patients with osteomyelitis can be performed safely.(8)

There is still controversy about the best surgical treatment. Many spine surgeons are unwilling to place an implant in an infected area. Some authors go one step further and advocate debridement-only surgery, followed by antibiotic treatment and second- stage instrumentation. Other authors propose single-stage anterior decompression, bone grafting and instrumentation.(9)

Aim of the work

The aim of this retrospective study was to evaluate the surgical outcome of idiopathic lumbar spondylodiscitis treated with posterior debridement combined with single-stage posterior instrumentation and autologus bone grafting.

METHODS

This retrospective study included 15 patients (9 males, 6 females) with a mean age of 66 years (range: 43-80) who were admitted to El-Menoufia University Hospitals Neurosurgical Department, in the period from Aug 2007 to Nov 2008.

The inclusion criteria were:

MRI of lumbo-sacral spine showing evidence of spondylodiscitis.

Plain radiographs revealed disc space narrowing with erosion and sclerosis of the adjacent end-plates.

Persistent high levels of laboratory tests: white blood cell count (WBC; count/mm3), C-reactive protein (CRP; mg/dl) and erythrocyte sedimentation rate (ESR; mm/h).

Failure of conservative treatment for about 3 months.

Development of neurological deficit.

The exclusion criteria were:

– Postoperative spondylodiscitis.

– Decreasing ESR and CRP levels with conservative treatment.

– Medically unfit patients.

The mean duration of symptoms before admission was 3.7 months (range: 0.5 to 12 months) and the mean duration of conservative treatment before surgery was 2.2 months (range: 1 to 3 months). The average follow-up period was 12 months.

Six out of 15 patients (40 %) had an elevated white blood cell count, while all 15 had an elevated ESR and CRP level .Plain radiographs, magnetic resonance imaging (MRI) with and without contrast were performed in all patients. Conservative treatment was given to all cases preoperatively in the form of two bactericidal and synergistic antibiotics were administered intravenously in high doses: mostly a first-generation cephalosporin and an aminoglycoside. Postoperatively, the antibiotics were adapted to the antibiogram performed on the specimens obtained. The duration of treatment was determined by the clinical evolution, the ESR and the C-reactive protein. Generally speaking, the antibiotics were administered intravenously for 6 weeks, and orally for 6 weeks.

Patients were operated in the prone position for the posterior instrumentation and grafting. A meticulous debridement of all granulation tissue, devitalized disc and sequestra was carried out to the point where healthy cancellous bone is exposed. Wide decompression of the thecal sac was done, with drainage of any epidural abscess and depridment of any necrotic tissue, which were submitted for bacteriological culture and sensitivity, and histological examination. Finally, trans-pedicular screw fixation was done combined with autologus done chips graft. Postoperatively all patients were immediately mobilized with an external lumbo-sacral orthosis. Duration of surgery and operative blood loss were recorded.

The clinical outcome was assessed according to Barthel Index,(10) which has been used since the 1960s because of its high reliability and validity, as regards the activities of daily living (ADL), and the VPAS as regards the severity of back pain.

Fig 1: Preoperative sagittal MRI-scan of the lumbar spine. T2-weighted images showing L3-L4 spondylodiscitis.

Fig 2: A, B. Postoperative antero-posterior and lateral radiographs showing L3-L4 posterior trans-pedicular screw fixation

RESULTS

After surgery, infection was successfully controlled in all patients, with return of the white blood cell count, ESR and CRP to normal within a mean period of 4 months (range, 2 to 6 months). Two patients (13% of cases) had a superficial wound infection which healed with debridement and antibiotics. The estimated blood loss was 650 ml (range 450-1000 ml). The mean duration of surgery was 3 hours (range: 2 hours to 4 hours). Bony fusion with incorporation of the graft was achieved in all patients.

.

Table I: Pre-operative clinical presentations

No.

%

Persistent low back pain

15

100 %

Radiculopathy

12

80 %

Constitutional symptoms

6

40 %

Table II: Pre-operative laboratory findings

No.

%

Elevated ESR

15

100 %

Elevated CRP

10

66 %

Leukocytosis

6

40 %

Table III: Pre-operative radiological leveling

No.

%

L 3/4 spondylodiscitis

8

53 %

L4/5 Spondylodiscitis

5

33 %

L5/S1 Spondylodiscitis

2

14 %

Table IV: Associated risk factors

No.

%

DM

5

33 %

Chronic Liver Disease

2

14 %

Urinary tract infection

4

28 %

Table V: Post-operative outcome according

to Barthel Index

No.

%

Excellent

12

80 %

Good

3

20 %

Total

15

100 %

DISCUSSION

Although there have been advances in diagnosis and treatment of spinal infections with further refinement of microbiological and histopathological techniques, early detection and management remain a matter of considerable difficulty.(11)

A correct diagnosis may be delayed by more than a month in over two thirds of the patients. A rise in the world’s elderly and immuno-compromised populations is bringing an increased incidence of pyogenic and granulomatous infections of the spine, hence, timely diagnosis of pyogenic spondylodiscitis with back pain and fever may prevent greater tissue destruction, spinal instability and progressive neurological deficit. Advances in therapy have reduced mortality rates, but early diagnosis is essential for a satisfactory outcome.(12)

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The exact cause of lumbar spondylodiscitis is controversial; some authors believe that there are two types of spondylodiscitis, a septic form caused by an infectious agent and an aseptic form resulting from an inflammatory reaction. (13) Others believe that there is no such thing as an aseptic spondylodiscitis and that this form is actually the result of a less virulent, low grade infection.(14) Once inoculated, the process of infection and discitis begins. More than often, the main causative organism is not identified. When an organism is identified, the most common infectious etiologic agent is Staphylococcus aureus followed by other Staphylococcus species and anaerobic organisms. Other less common organisms include Streptococcus viridans and other Streptococcus species, Escherichia coli, Pseudomonas aeruginosa.(15)

Traditionally, the mainstay treatment of pyogenic infections of the spine remains medical management, with external immobilization and culture specific antibiotics for a minimum of 4 to 6 weeks. However, large clinical series have demonstrated the need for surgical intervention in up to 43% to 57% of the patients, in case of neurological compromise, deformity, instability, abscess formation, extensive destruction, intractable pain or failure of medical management.(16)

Because all the patients in our study were from the low socio-economic class and because of the difficulty to identify the causative organism, we elected not to perform CT guided biopsy and give the patients empirical broad spectrum antibiotics covering both aerobic and anerobic pathogens.

It has been reported that the most sensitive laboratory studies indicative of the presence of an inflammatory process are the ESR and the CRP.

However, it should be noted that in adults, ESR trends are confused by associated medical conditions. Nevertheless, the ESR was a useful tool in the management of adult pyogenic spondylodiscitis, and the authors of most studies on this matter, view a 60 to 85% reduction in the ESR as compatible with eradication of infection, and this correlates with the results in our study which reported reduction of ESR in 80% of case.(17)

MRI is the radiographic imaging modality of choice in diagnosing lumbar spondylodiscitis with a reported sensitivity and specificity of 93% and 97%, respectively. It has been shown that MRI is superior in showing loss of disc space height. This can be accompanied with erosion of the vertebral end plates above and below the infected disc space, and these changes were reported in all cases included in our study.(18)

In the surgical treatment of spondylodiscitis, numerous authors have advocated a staged operation with a period of antibiotic therapy bridging the debridement and instrumentation procedures. Open surgical drainage for spondylodiscitis was historically reserved for patients with an epidural abscess. The prognosis is stated to be better when treatment is instituted early during the infection.(19)

Posterior debridement combined with trans-pedicular screw fixation has been advocated by several authors. Dai et al(20) obtained 100% of good results with this technique in a series of 22 cases and we used the same technique in this short study.

The first series describing the consistent placement of posterior instrumentation at the time of debridement was published in 1988 by Redfern et al(21) In 1996, Rath et al(22) reported on a series of 43 patients with thoracic or lumbar spondylodiscitis who were treated entirely via a posterior approach. This approach is based on the principle that instrumentation placed posteriorly involves a second operating field that is not (at least directly) contaminated.

Single-stage procedure surgery (autograft and posterior instrumentation) was used in this study and its results correlates with the Kuklo et al(23) study which included 21 patients with pyogenic vertebral osteomyelitis managed by a single-stage with neither recurrence of infection nor perioperative complications. A single-stage procedure has several advantages, such as avoidance of a second anesthesia, reduced blood loss, avoidance of graft displacement during transfers, earlier mobilization, less anxiety for the patient, shortened hospital stay and less expense. (23)

According to Barthel Index,(10) 80 % of our patients had an excellent result, without pain or restriction of activity. From a neurological viewpoint, ten patients (83%) of the 12 with a neurological deficit improved and these findings were consistent with Fayazi et al(24) who reported 85% improvement after posterior approach for lumbar spondylo-discitis.

After posterior instrumentation, fusion rates up to 93% and 96% have been reported (25) the current study yielded a 100% fusion rate. As stated by Hadjipavlou et al(26) posterior stabilization through instrumentation was the critical factor in these improved results. We believe that posterior instrumentation and grafting is the principal stabilizer of the vertebral column in order to achieve a successful fusion.

Conclusion

Although this is a limited series, we found that a posterior debridement combined with trans-pedicular screw fixation and autologus grafting may be a safe and effective surgical treatment for selected patients with lumbar spondylodiscitis and may not be associated with recurrent hardware infections and/or any major complications.