TO THE EDITOR:

Letter to the Editor Regarding “Development of Tuberculosis Spine Instability Score (TSIS)”

We read with interest the recent publication on “Development of Tuberculosis Spine Instability Score (TSIS)” by Ahuja et al. While the article has dealt with an important aspect of providing objectivity to the assessment of instability in spinal tuberculosis, we would like to express our concerns regarding the methodology and their selection of factors in evolving the score. Of the nine factors considered, there are serious issues in the way that at least five of them have been considered.

LOCATION OF LESION

The score has provided two points for all junctional areas of the spine. This approach is flawed as not all the junctional areas are the same. While the cervicothoracic and thorocolumbar junctions are prone for instability and precipitous collapse, the occipitocervical and lumbosacral junctions are very amenable to conservative therapy. A 15-year long-term follow-up of lumbosacral lesions have shown that these junctional lesion are stable and heal by subsidence and not collapse1. A long-term follow-up of conservatively treated cases in OC lesions again showed that many are stable and treated without surgery2. So bunching up all junctional lesions as one is an error leading to over treatment of at least lumbosacral lesions.

PAIN

Pain in an infectious disease is universal and while it can be due to instability it is always present due to the biological pain of an infection. In the acute stage of an infective lesion, while the authors have stressed that they are giving weightage to a mechanical pain, it is usually difficult or impossible to differentiate between biological and mechanical pain as every infection will have pain on sitting, change of postures and also a pain similar to instability catch. In fact, many patients in acute stages have severe pain and cannot even be tested for full range of movements. Many patient’s pain will be found to settle very well after three to six weeks of chemotherapy3. Addition of pain to the criteria of instability will unfavorably push many patients who do not need surgery to a higher level in this score.

MULTILEVEL INVOLVEMENT

Involvement of multiple levels is certainly worrisome but again just having multilevel disease is not indicative of instability. It is common to find multiple levels involved with only edema or minimal destruction at each level4. The authors have very rightly included the extent of vertebral body loss as one of the criteria and once this has been included, the number of levels of lesion becomes superfluous and flawed to include many patients toward surgery.

INTRASPINAL/PARASPINAL ABSCESS

We would like to strongly dispute inclusion of abscess into instability. Patients vary in the presence or absence of intraspinal/paraspinal abscess and also the size of it. Surgeons in endemic areas of tuberculosis would have always have the experience of treating patients with just minimal bone involvement but huge abscesses and similarly extensive bony destruction without any abscess4. Also abscesses respond well to conservative management and complete resolution is possible with medical management5. The presence or the location or the size of the intraspinal/paraspinal abscess in no way corresponds to a bony lesion or instability and hence cannot be a determinant of instability. It is surprising that this has been included into an instability score.

INVOLVEMENT OF POSTERIOR SPINAL ELEMENTS

We agree completely that involvement of facet joints is an important element in determining instability. Spinal tuberculosis is, however, mainly an anterior disease and actual involvement of posterior column or the facet joints is rare and can be found in 5%–10% of patients6. However, our concern is that the authors have described posterior column involvement only as an actual destruction by involvement of the facet joints and totally overlooked facet subluxation which is the most common form of posterior column failure in spinal tuberculosis. The common mode of instability has been well described to be an anterior column destruction followed by facet subluxation which can be sequential in severe cases leading to buckling collapse7. Radiological signs depicting this model of failure have also been well described and documented8. We consider it as an important lapse of this work to have overlooked this method of failure and only given points to actual destruction of the facet joints.

The score we feel is judgementally flawed having included many criteria which have no bearing to instability. Quite respectfully we would like to submit that this score is overestimating instability and thus may not be the best way to be followed for assessing instability.

References 1. Rajasekaran S, Shanmugasundaram TK, Prabhakar R, et al. Tuberculous lesions of the lumbosacral region. A 15-year follow-up of patients treated by ambulant chemotherapy. Spine (Phila Pa 1976). 1998;23:1163–1167. 2. Gupta SK, Mohindra S, Sharma BS, et al. Tuberculosis of the craniovertebral junction: is surgery necessary? Neurosurgery. 2006;58:1144–1150; discussion 1144–1150. 3. Goel A. Tuberculosis of craniovertebral junction: role of facets in pathogenesis and treatment. J Craniovertebr Junction Spine. 2016;7:129–130. 4. Jain AK, Sreenivasan R, Saini NS, et al. Magnetic resonance evaluation of tubercular lesion in spine. Int Orthop. 2012;36:261–269. 5. Cao G, Rao J, Cai Y, et al. Analysis of treatment and prognosis of 863 patients with spinal tuberculosis in Guizhou Province. BioMed Res Int. 2018;2018:e3265735. 6. Kumar K. Posterior spinal tuberculosis: a review. Mycobact Dis. 2017;7:1–4. 7. Rajasekaran S. Buckling collapse of the spine in childhood spinal tuberculosis. Clin Orthop Relat Res. 2007;460:86–92. 8. Rajasekaran S. The natural history of post-tubercular kyphosis in children. Radiological signs which predict late increase in deformity. J Bone Joint Surg Br. 2001;83:954–962.