1 An introduction to classification and grading of spinal infection

Developing a comprehensive classification system that will encompass all types and severities of infections of the bony spine, the associated soft tissues, the neural elements, and it coverings is a Herculean task. The ideal system should assign severity in terms of anatomical extent, microbiological and pathological nature of lesion, clinical syndromes, and outcomes of therapy and also help allocate therapeutic strategies. It should allow easy documentation and communication across cultures. Modern scoring systems should also consider converting nonparametric data into parametric information for easy digitization and retrieval since in the near future one can visualize such data storage systems becoming totally digitized.

2 The challenges

Unlike spinal deformity or fractures of the spine the constraints to uniform scoring or grading are multiple.

3 What do we have now

Tuberculosis (Tb) of the spine is as old as mankind itself and naturally most efforts to quantify the disease severity has been in this area with less data on Pyogenic infections. One of the early attempts at classification of Tb has been that of Tuli [1] in 1975 based on x-ray appearance. Based on the origin of the disease he described a pardiscal disease, a central disease, an anterior lesion, and an appendicular lesion (encompassing all the posterior elements) which appears to be a modification of Doub and Badgley [2].

Kumar [3] has further classified posterior element disease into subtypes based on the site of the lesion, radiological stage, associated lesions, and the neurological involvement. The neurological involvement of Tuberculosis has been graded according to severity by Konstam et al [4] and Goel [5] based on the Frankel grading system [6] and modified by Tuli [7]. Jain [8] in 2005 incorporated bladder and bowel affection and sensory involvement into the neurological evaluation. Perhaps the most important prognostic indicators in Tb spine are the deformity progression potential and neurological progression potential. Rajasekaran [9] and coworkers have tried to quantify the extent of vertebral destruction (number of vertebrae affected and loss of bone mass) and correlate it with the progression of deformity. Based on all these factors several authors have attempted simplified, algorithmic treatment regimes. Bhojraj [10] relies entirely on the morphological pattern of vertebral disease while the GATA classification [11] from Turkey relies on morphology and neurology to determine treatment strategy. However, these are at best simplistic guidelines and certainly not applicable to all cases of spinal Tb.

Pyogenic infections of the spine came along much after tuberculosis, largely due to increasing invasive procedures on the spine and longer survival of patients with cancer, autoimmune disease, and organ transplants. Winter et al [12] have described classifying systems to cover many aspects of spinal infection from host age to causative organism. However they are discrete units with no grading attempted. Cierny and Mader’s [13] classic on pyogenic osteomyelitis of long bone is a workable model but not directly applicable to cancellous bone infection. Thalgott [14] and coworkers’ study on postoperative spinal infection is an excellent work in that category of patients but obviously ignores other infections and also does not take into account the pathomorphology of the disease. Dewald et al [15] and Harrington et al [16] look specifically at host parameters (originally in relation to tumors but probably equally applicable to infections).

What we have is a picture of many systems, none comprehensive to cover all aspects of all infections and guide therapy as well as prognosticate outcomes.

4 The way forward

Infection, including spinal infection, is a problem involving the microbial agent, the host and his underlying susceptibility, and environmental factors. Specifically in spinal infection this implies the causative organism for agent—Pyogenic, MRSA, M Tuberculosis, atypical mycobacteria, MDR/SDRTb, Brucellae, fungi, etc. Many host factors specifically affect spinal infections – age, general health and hygiene, diabetes, organ transplants, anticancer and antirheumatic therapy, general debility, drug abuse, AIDS, etc. Environmental factors we need to evaluate are issues like previous invasive procedures (discogram, lumbar puncture, etc), the presence of implant, nature of implant, presence of bone graft or graft substitute, the approach used in earlier surgery, etc. Disease pathomorphology may also be included as a separate heading (number of vertebrae affected, extent of destruction, presence of abscess, neurological status, degree of kyphosis, etc) overlapping with the said criteria as shown in Fig 5.6-1 below. The comprehensive evaluation and strategizing system for spinal infection must include all these parameters which at the moment is lacking. The way forward appears to be creating large databases of well documented cases (infrequent occurrence mandates multicenter studies), critically reviewing them, and formulating digitizable systems encompassing all aspects of infection mentioned above.

5 References

1 Calderone and Larsen Classification of Spinal Infections

Calderone RR, Larsen JM (1996) Overview and classification of spinal infections. Orthop Clin North Am; 27:1–8.

SCALE ILLUSTRATION

CONTENT

RATING

2 Cierny and Mader Classification of Osteomyelitis

Developed for long-bone osteomyelitis*

Cierny G 3rd, Mader JT (1987) Approach to adult osteomyelitis. Orthop Rev; 16:259–270.

Related posts:

5.1 Spine Classifications and Severity Measures 5.3 Deformity severity measures: 5.3.2 Spine Classifications and Severity Measures 5.3 Deformity severity measures: 5.3.4 Deformity severity measures: spondylolisthesis 5.5 Osteoporosis severity measures 5.4 Degenerative measures: 5.4.1 Degenerative measures: cervical myelopathy 5.3 Deformity severity measures: 5.3.1 Spine Classifications and Severity Measures

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