COMMENTARY
Vincent Arlet
Professor of Orthopaedic Surgery
University of Pennsylvania
Philadelphia, PA, USA
Dear Editor,
I read with great interest the case report from Silverstein and colleagues [1] about the surgical technique used to correct a congenital kyphosis in Uganda.
Having been involved in the care of spinal deformities in developing countries for
the last 7 years, I would like to comment on this interesting case.
First, I commend the authors for performing such a procedure (pedicle subtraction
osteotomy [PSO] at the cord level) with this nice immediate postoperative result.
Performing complex spine surgery in such environment requires specific talents that
range from extraordinary personal relationship skills (built over the years with the
local surgical team), to very skilled surgeons used to perform such techniques of
PSO at this level.
However, a few points need to be clarified.
Diagnosis
The diagnosis from the x-rays available appears to show a congenital kyphosis type
2 with lack of segmentation. Besides there seems to be multiple levels of defect of
segmentation on the x-rays as it seems that the level T12– L1 and L1–L2 are fused
anteriorly as well. The curve measured 65°, as indicated by the authors. Such a defect
of segmentation will very likely progress in a 10-year-old girl who is most likely
premenarchal; thus, I agree with the need to correct the deformity.
Her neurological picture is intriguing and I think this should be emphasized in the
text as I am not aware of such a case causing myelopathy at such a young age as opposed
to type I congenital kyphosis (defect of formation), which is notorious for neurological
complications if not stabilized.
In the articles by McMaster and Singh [2] and Winter et al [3], all neurological complications from congenital kyphosis were observed in type 1
or 3 (mixed types) and none from type 2 [4]. Therefore, I have some serious doubts as to this congenital kyphosis causing neurological
symptoms in this case. It is unfortunate that no MRI was available to rule out other
causes of myelopathy or gait disturbance. If Silverstein et al [1] believed that kyphosis was responsible for myelopathy then a simple myelogram with
a lateral shoot through x-rays could have been helpful.
Spinal cord monitoring
In the last 10 years it has become state of the art to perform spinal deformity correction
with spinal cord monitoring (SCM). Performing spinal deformity surgery without SCM
is obviously possible and one can use the Stagnara wake up as the only way of monitoring.
For simple deformities in an underdeveloped environment, this may still be adequate.
Still, such a test may be too late in the course of surgery to allow reversible cord
insult in the case of complex PSO at the cord level. We know from Lenke and colleagues
[3] that in 20% of cases of complex spine osteotomies performed at the cord level, the
MEP disappear and action need to be taken promptly, I would be concerned to perform
PSO at the cord level without SCM.
In today’s high technical environment many surgical teams who have performed outreach
spine surgery had SCM available. The equipment necessary to perform state-of-the art
SCM can be brought in a carry-on luggage and many electrophysiological companies offer
their service free of charge for such missions. So I think that performing complex
osteotomies at the cord level during mission trips should not be done without SCM.
Surgical indication and technique
The kyphosis of the patient appears to measure 65°, which is still in a reasonable
range, and such a deformity may only require minor corrections bringing the deformity
to less than 50°.
One of the principles of kyphotic corrections is to stop the progression of the curve
and to fuse and instrument the integrality of the Cobb angle (I eyeball it to be from
T5 to L2 in this patient, as I do not have the whole standing spine x-rays). Thus,
the instrumentation should have been more extensive, including the whole Cobb angle
and stopping above the first lordotic disc. My concern is that where the instrumentation
stopped short of the whole Cobb angle we shall see recurrence of the deformity, as
the posterior column will keep growing and the anterior column with the defect of
segmentation will not grow any longer. Wedging of the discs below may also contribute
to recurrence of the deformity.
It would have been interesting to see a lateral shoot through the spine and see how
the overall kyphosis from T5 to L1 would reduce. I would not be surprised if the deformity
would have corrected to close to 50° on the supine bolster lateral shoot through x-rays.
Overall, I obviously cannot argue with this short follow-up success. My concern, however,
is to see generalization of such complex techniques when a more simple posterior instrumentation
with simple and less dangerous Smith-Petersen osteotomies (performed at the place
of no anterior fusion existed) would have most likely been satisfactory to correct
enough of the deformity and address the neurological issue if it ever was related
to the kyphosis. Complex spinal osteotomies at the cord level should not be performed
without SCM even in developing countries. Rules of fusion levels in kyphotic deformities
have been established since a long time and a long-term follow-up would be required
to prove the contrary.
