22 Mini-open Endoscopic Excision of Hemivertebrae
R. Stücker
22.1
Endoscopic Excision of Hemivertebra
Endoscopic surgery, like thoracoscopy or minimally in- vasive retroperitoneal surgery, is now a well-accepted alternative to traditional methods and is used for a va- riety of spinal diseases such as idiopathic scoliosis, ky- phosis, degenerative disorders, and spondylitis.
For adults, surgical tools and instrumentations are available even for multisegmental fusions. Spinal sur- gery for small children is less frequently performed, but there are a number of problems that need to be ad- dressed by surgery, such as tumors, infections, and con- genital and developmental deformities of the spine. En- doscopic surgery has proved to be of great benefit for ad- olescents and adults, especially in the reduction of mor- bidity and scar formation. Its usefulness for children has not been clearly shown. The author reports on a series of 13 children with various forms of hemivertebrae who were treated by a combined posterior and minimally in- vasive endoscopically assisted anterior approach. Eight children were under 5 years of age at operation.
22.2
Terminology
A hemivertebra is a defect of vertebral formation with a typical triangular wedge-shaped form. Posteriorly only one pedicle and one hemilamina are present. A he- mivertebra is fully segmented, semisegmented, or non- segmented. In a fully segmented hemivertebra there is a normal disc space and almost normal growth poten- tial of the apophyseal ring above and below and the he- mivertebra is completely separated from the adjacent vertebrae. A hemivertebra can also be semi- or non- segmented with less or even no remaining growth po- tential. An incarcerated hemivertebra usually produces less deformity because the adjacent vertebrae have an trapezoidal form, therefore compensating for the size of the hemivertebra with almost no deformity remain- ing. A hemivertebra may be accompanied by an unseg- mented bar on the other side and usually produces seg- mental kyphosis.
22.3
Surgical Principle
Excision of the hemivertebra is performed in two steps.
The first step is performed in the prone position. The posterior parts including hemilamina, transverse pro- cess, and rib together with the complete pedicle are re- moved. The posterior wound is temporarily closed. The anterior part of the surgical procedure is performed in the lateral decubitus position under endoscopic con- trol. Instead of multiple portals only one 4- to 5-cm- long incision is used. The endoscope is introduced through a separate stab incision and no special instru- ments are required.
22.4 History
In 1928 Royle reported on the removal of an accessory vertebra without the availability of modern segmental fixation [7]. In 1979 Leatherman and Dickson recom- mended a two-stage corrective procedure to avoid neu- rological complications [6]. Since then one-stage sur- gery has evolved to be the standard treatment for an isolated hemivertebra [1, 2]. More recently, a one-stage posterior hemivertebra resection was reported by some authors [8, 9].
22.5 Advantages
In the case of open hemivertebra excision, the anterior
approach produces most of the morbidity associated
with this type of surgery. A minimal incision and endo-
scopically controlled surgery offer less morbidity to
this technically demanding procedure. In addition, bet-
ter illumination and working under magnification con-
tribute to the safety of the procedure. In case of prob-
lems, such as severe bleeding, surgery can easily be
converted into a conventional open procedure.
22.6
Disadvantages
Performing endoscopic surgery on small children for spinal disorders requires expertise in spinal surgery and in endoscopic procedures. A long learning curve must be anticipated.
22.7
Indications and Contraindications
Endoscopic hemivertebra resection can be performed in the lumbar and thoracic regions. Indications for sur- gery are a progressive curve and the development of secondary curves. In the lumbosacral area increasing pelvic obliquity or trunk decompensation are indica- tions for surgery. Relative contraindications for endo- scopic procedures are previous surgery and revisions.
In case of an intraspinal anomaly, neurosurgical inter- vention has to be considered before or together with hemivertebra excision.
22.8
Patient’s Informed Consent
Besides typical complications some special side effects of hemivertebra excision need to be addressed. Sensory as well as motor deficits may occur as a consequence of nerve root entrapment or direct injury to the spinal cord. As a worst-case scenario even bladder and bowel paralysis or complete paraparesis is possible, although current literature suggests that it is rare. In addition, problems with fusion may occur, such as delayed union or pseudarthrosis. Because of insufficient primary sta- bility of the instrumentation a cast and a brace have to be worn for 6 months.
Complications related directly to the anterior ap- proach comprise pneumothorax, pleural effusion, and injury to ureter or other retroperitoneal structures.
Temporary bladder or bowel dysfunctions after sur- gery can occur. Intraoperative bleeding most frequent- ly occurs from epidural veins. Specifically, bleeding may sometimes occur during removal of the posterior wall of the hemivertebra and blood transfusions may be necessary.
22.9
Surgical Technique
Preoperative MRI and three-dimensional CT recon- structions before surgery are mandatory to assess the anatomy and rule out intraspinal anomalies (Fig.
22.1).
Fig. 22.1. Preoperative MRI shows a semisegmented hemiverte- bra at the lower lumbar region
In all cases patients are positioned prone on the operat- ing table for the first part of the surgery. An arterial and central venous line are established and prophylactic an- tibiotics are given. A posterior skin incision is per- formed just over the hemivertebra. Usually the skin in- cision is between 6 and 8 cm long. The pedicle of the he- mivertebra is identified by fluoroscopy, and the lami- nae of the adjacent vertebra are subperiosteally ex- posed. The hemilamina is removed and then the trans- verse process and ribs are sectioned. The pedicle is re- moved with a high-speed diamond burr. If a contralat- eral posterior bar exists it is sectioned with rongeurs.
Since the dural sac together with the spinal cord is shifted toward the concavity, removal of the pedicle is a relatively safe procedue and can be done without touching the cord. In small children special pediatric supralaminar and infralaminar hooks are inserted one segment above and below the hemivertebra together with a rod. The hooks are loosely tightened to the rod.
The wound is packed with sponges and temporarily closed with a running suture.
The patient is then positioned in the lateral decubi-
tus position with the side of the hemivertebra upward
(Fig. 22.2). A 4- to 6-cm incision is performed in the
midaxillary line corresponding to the location of the
hemivertebra. The hemivertebra is always approached from the convexity. The location of the incision can eas- ily be appreciated after having performed the posterior incision. Thoracic hemivertebrae and hemivertebrae in the upper lumbar region down to L2 are approached by thoracotomy and by a diaphragm-splitting approach. A small rib spreader is usually inserted (Fig. 22.3). Selec- tive intubation is not performed. A small retractor is generally inserted for lung protection. Access to hemi- vertebrae in the lower lumbar region is obtained through a typical retroperitoneal approach. The ab- dominal muscles are separated by blunt dissection. For this location we use a self-retaining retractor with long blunt blades. In addition, the assistant holds a long re- tractor. A 6-mm-diameter endoscope with a 30° lens is introduced through a separate stab incision. A flexible holding arm is generally used to fix the endoscope. It is positioned opposite the hemivertebra. The surgeon stands in front of the patient while an assistant stands on the opposite side. Ideally, one monitor should be placed on either side to give both the surgeon and the assistant an optimum view. The bone collected from both the anterior and posterior approach is stored for later bone grafting. The first step during anterior re- moval of hemivertebrae is to resect the adjacent disc spaces (Fig. 22.4). The dissection has to be complete in- to the concavity. The resection of the hemivertebra is started with chisels. When the posterior wall is identi-
Fig. 22.2. Lateral decubitus position for anterior part of surgery
fied the resection is completed with the use of a dia- mond burr.
The posterior wound is opened again with the pa- tient still in the lateral decubitus position and compres- sion is performed between the adjacent laminae with the help of the supra- and infralaminar hooks. Com- pression is performed slowly and cord or nerve root compression should be avoided. In the case of a single fully segmented hemivertebra with two adjacent disc spaces it is necessary to add an anterior strut graft or a titanium cage to correct segmental kyphosis. In young children less than 3 years old it is usually easy to close the gap by simply performing posterior compression.
For older children transpedicular fixation or anterior supplementary instrumentation may be used to in- crease stability.
Fig. 22.3. A small retractor is inserted between ribs
Fig. 22.4. Adjacent discs have already been removed. The ante- rior part of the hemivertebra can be removed with rongeurs, curettes, or a diamond burr
22.10
Postoperative Care and Complications
Since in small children compliance with postoperative management is poor, a plaster brace is applied immedi- ately after surgery. It is then changed after 2 weeks. Af- ter 6 weeks the plaster cast is bivalved and a plastic re- movable brace is manufactured. For the first 6 weeks af- ter surgery the parents are told not to allow standing or walking, while sitting is not restricted. After 6 weeks standing and walking is permitted with the aid of an walker to avoid falling. If residual flexible components of the curve are still present, brace treatment is contin- ued (Fig. 22.5a, b)
22.11 Patients
From January 1999 to February 2003, 13 children (8 bo- ys and 5 girls) with an average age of 4+11 years (1+3 to 12+6 years) had hemivertebra excision by a combined posterior and minimally invasive endoscopically as- sisted anterior approach. Eight of the 13 patients were less than 5 years old at the time of surgery. Details are given in Table 22.1.
a b
Fig. 22.5. a Preoperative X-ray of a 2+3-year-old girl with a fully segmented hemiverte- bra at L1 and a long flexible curve. b Postoperative X-ray showing complete correction of the congenital deformity with some flexible compo- nent remaining 1 year after surgery. Brace treatment was continued
22.12 Results
The index curve measured 45° (38 – 55°) preoperatively and 12° (5 – 18°) postoperatively, contributing to an av- erage correction of 73 %. Improvement of secondary curves occurred in each case, but this was also depen- dent on additional congenital deformities which were present in 6 of the patients.
No neurological complications were found and no pseudarthrosis developed. In 5 of the 13 patients blood transfusion was required. No major hemorrhage or other complications were encountered during opera- tion. Two patients developed pneumonia after surgery which resolved quickly with adequate therapy.
22.13
Critical Evaluation
Hemivertebrae can be resected by a combined anterior and posterior approach or by a posterior approach on- ly. The advantage of a single posterior approach is to avoid anterior scars and repositioning during surgery.
The advantage of an anterior approach is that resection
of the hemivertebra and adjacent disc spaces is more
complete, and correction and restoration of the sagittal
Table 22.1. Patients’ data.
(T Thoracic spine, L lumbar spine)
Patient Age (years+
months)
Gender Loca- tion
Type of hemivertebra
Other abnormalities
K.K. 2+6 Male T11 Fully segmented Lumbosacral dysplasia
L.J. 6+6 Male T11 Fully segmented
M.S. 2+0 Female T12 Semisegmented Congenital bar and fused ribs upper thoracic region F.M. 2+10 Female T11 Fully segmented
G.F. 5+5 Female L4 Fully segmented
G.A. 1+9 Male L1 Fully segmented
L.V. 5+6 Male T12 Fully segmented
C.E. 1+3 Female L1 Semisegmented Contralateral bar
G.M. 2+3 Female L1 Fully segmented Additional non-segmented hemivertebra at T6
M.S. 7+11 Male L4 Semisegmented
S.A. 4+2 Male T10 Fully segmented Contralateral hemivertebra T6 J.T. 2+7 Male T7 Semisegmented Contralateral bar and fused ribs
F.R. 12+6 Male L4 Fully segmented
contour better. It is now well accepted that hemiverte- bra excision should be carried out early before second- ary structural curves have developed [1, 7]. In our ex- perience it is easier and safer to remove hemivertebrae in small children than in adolescents. In children under the age of 3 years compression with a supra- and infra- laminar hook is usually sufficient for correction and stabilization. Neurological complications after hemi-
Fig. 22.6. This male patient had hemivertebra excision at T12 at the age of 2+6 years. At 2 years follow-up there is no residual deformity. Notice the small anterior scar after endoscopically assisted surgery
vertebra excision are rare [1 – 5, 7]. In our series of 13 patients treated by endoscopically assisted hemiverte- bra excision no neurological complications were en- countered.
The introduction of a minimally invasive approach by endoscopically assisted surgery produces less mor- bidity. Besides less morbidity through smaller inci- sions, better illumination and working under magnifi- cation are major advantages of this procedure. To our knowledge, endoscopically assisted surgery has not been reported for hemivertebra removal. Early et al. [3]
reported on the feasibility of anterior thoracoscopic spine surgery in children. In their opinion performing thoracoscopic spine surgery on patients under 20 kg is a relative contraindication. We have performed endo- scopically assisted surgery on children weighing 10 – 15 kg without any significant problems (Fig. 22.6).
22.14 Conclusions
In children, excision of hemivertebrae with the help of an endoscopically assisted anterior approach is a safe procedure and can even be performed on very small children under the age of 5 years.
References
1. Bergoin M, Bollini G, Taibi L, Cohen G (1986) Excision of hemivertebrae in children with congenital scoliosis. Ital J Orthop Traumatol 12:179 – 184
2. Bradford DS, Boachie-Adjei O (1990) One-stage anterior and posterior hemivertebral resection and arthrodesis. J Bone Joint Surg Am 72:536 – 540
3. Early SD, Newton PO, White KK, Wenger DR, Mubarak SJ (2002) The feasibility of anterior thoracoscopic spine sur- gery in children under 30 kilograms. Spine 27:2368 – 2373
4. Holte DC, Winter RB, Lonstein JE, Denis F (1995) Excision of hemivertebrae and wedge resection in the treatment of congenital scoliosis. J Bone Joint Surg Am 77:159 – 171 5. Lazar RD, Hall JE (1999) Simultaneous anterior and posteri-
or hemivertebra excision. Clin Orthop 364:76 – 84 6. Leatherman KD, Dickson RA (1979) Two-stage corrective
surgery for congenital deformities of the spine. J Bone Joint Surg Br 61:324 – 328
7. Royle ND (1928) Operative removal of an accessory verte- bra. Med J Aust 1:467 – 468
8. Ruf M, Harms J (2003) Posterior hemivertebra resection with transpedicular instrumentation: early correction in children aged 1 to 6 years. Spine 28:2132 – 2138
9. Shono Y, Abumi K, Kaneda K (2001) One-stage posterior hemivertebra resection and correction using segmental posterior instrumentation. Spine 26:752 – 757
