Surgical methods for congenital scoliosis

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1. In situ fusion

2. Convex-side hemiepiphysiodesis

3. Convex-side hemiarthrodesis

4. Growth-guidance surgical methods

5. Instrumentation with Zielke-Askani growing rod

6. Vepter instrumentation

7. Wedge vertebra resection, Harms technique

Resection of a hemivertebra was first described by ROYL in 1928, but the method did not establish itself until much later. In 1979, LEATHERMAN was the first to report good results with a number of hemivertebral resections in two-session (dorsal, then ventral) operations. Correction after resection of the hemivertebra was achieved with a plaster or plastic brace worn over a period of about 6 months. Alternatively, the gap resulting from resection of the hemivertebra was closed using compression instrumentation (Harrington) hooks.

The disadvantages of combined wedge vertebra resection acc. to LEATHERMAN are as follows:

Necessity of a second ventral surgical session with repeated anesthesia
Correction in brace with long-term immobilization-ifficult to realize in the thoracic region in particular
Compression with hook instrumentation requires stable dorsal bony structures, making its use highly questionable and conditional in small children.

We developed a wedge vertebra resection technique designed to avoid the pitfalls of this method. Our method requires dorsal access only. It was carried out for the first time in 1991 and is characterized by two basic principles:

Complete resection of the hemivertebra via dorsal access only
Correction and stabilization by means of short-length and semirigid transpedicular instrumentation.

Surgical technique:
In dorsal access (from behind) the hemivertebra and adjacent vertebra are exposed including the small intervertebral joints. Preparation of the costal facet joints is also necessary in the thoracic spine. The entry points for the pedicle screws in the adjacent vertebrae are first marked with needles. The position and direction of the needles are then checked via the image converter (fig. 1).


	fig. 1

The pedicle screws are inserted following drilling and threading. The dorsal portions of the hemivertebra are resected (removed) including the lamina, joint facets, transverse process, dorsal portions of the pedicles. The dural sac and nerve roots above and below the pedicle of the hemivertebra are exposed (fig. 2).


	fig. 2

Following resection of the pedicles, the lateral portion of the hemivertebra is exposed: in the lumbar spine this requires resection of the transverse process, and in the thoracic spine the extra caput costae (posterior ends of the ribs) must be resected to expose the lateral wall of the vertebral body properly. Preparation of the lateral wall and anterior wall of the vertebral body is blunt, and can be done either below or outside the periosteum. It is important to intoduce a blunt spatula at this point to protect the vessels lying ventrally in front of the hemivertebra (fig. 3).


		fig. 3

While protecting the dural sac (surrounding the spinal cord) and nerve roots, the intervertebral discs adjacent to the hemivertebra are then incised and removed. The remainder of the pedicle, together with the hemivertebra, is then mobilized and removed (fig. 4).


		fig. 4

Then the intervertebral disc on the concave side connecting the two vertebral bodies on the cranial and caudal side of the hemivertebra is removed. The upper plates of the adjacent vertebra are then freshened (fig. 5).


		fig. 5

Now the longitudinal supports are inserted on the convex side with compression via the convexity, completely closing the gap resulting from the resection of the hemivertebra. The freshened endplates of the adjacent vertebral bodies move close together. The bone material from the hemivertebra is packed in to facilitate rapid bony fusion. Dynamic stabilization is also carried out in the concavity (figs. 6 and 7).


	fig. 6	fig. 7

In the presence of an additional pronounced kyphosis, a titanium cage can be inserted as a ventral support into the intervertebral disc space. This cage then acts as a support or pivotal point for dorsal compression to achieve segmental lordosis. This also prevents the spinal cord from being shortened excessively.
For single hemivertebrae with no other anomalies, it usually suffices to fuse only the two vertebrae adjacent to the hemivertebra. For more pronounced structural changes in the adjacent vertebrae or a greater degree of kyphosis, additional segments can be temporarily involved in the instrumentation. In cases of contralateral bar formation and rib synostoses, the bar is severed and the concave-side capiti costae are resected. The instrumentation must be done over the entire length of the bar.

Follow-up treatment:
As a rule, patients can leave their beds on the first day after the operation. Depending on the stability of the instrumentation and the length of the fusion, a brace (2-shell orthotic device or Stagnara brace) is fitted and worn for about 12 weeks.

Assessment of the results

Correction of the major curve:
The preoperative segmental angle of the major curve averaged 37.6° (16-66°). This was corrected postoperatively to 8.7° (-1° to 29°) and amounted to 6.2° (-5° to 30°) at the last follow-up examination. This translates into an average correction of 31.4° or 84%.
The overall preoperative angle of the major curve averaged 45.9° (16° to 109°), corrected postoperatively to 11.9° (-1° to 45°) and 9.9° (-5° to 55°) at the last follow-up examination. This corresponds to an average correction of 36° or 78%.

Correction of the minor curves:
The correction of the minor curve is highly satisfactory. For the contralateral minor curve following cranially, a spontaneous correction of 80° was achieved in most cases, as was a spontaneous correction of 75° for the minor curve following caudally.

Sagittal plane correction:
The sagittal profile was also preserved or normalized in most cases.

Complications:
There were no cases of neurological complications. An implant rupture is a possibility since this is a dynamic instrumentation within an overall dynamic system. In a small number of patients, a scoliosis developed again in the course of further growth, requiring surgical correction once more.

Summary:
The overall results were highly satisfactory, and the number of cases requiring follow-up surgery can also be viewed as absolutely acceptable. It is important to remember that the patients were very young. The average age of our patients was 3.5 years (15 months to 6 years).
This clearly documents the considerable growth potential of the spinal column at the time of surgery. Reliable predictions of the effects on fusion within the growing skeleton are never possible. On the whole, however, we were amazed at how small the influence of growth on the fused segment turned out to be.

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