Radiographic & Functional Oucomes of Surgical Treatment

The outcomes of scoliosis treatment are being evaluated continually in an attempt to optimise the results for each scoliosis patient. The two prinicpal goals of any scoliosis surgery are to limit further curve progression and achieve some degreeof deformity correction. The greater the focus on deformity correction, however, the greater the risk of procedure, with the most obvious risk being limitation of spinal cord function. Advances in surgical technique, instrumentation, and intra-operative monitoring of the spinal cord have allowed greater and safer deformity correction than that achieved with the Harrington rod, which is the correction I had in 1989. The Harrington rod is from the era of the 1960s and 1970s.

Deformity correction both radiographically and with regard to trunk shape is important to many patients with scoliosis. The functional outcome after fusion is equally important and may be assessed using a variety of methods, including measurements of physiologic function, such as range of motion, strength, and pulmonary volume and flow, as well as patient based outcomes determined by specialised questionnaires. We are focusing on radiographic and functional outcomes of scoliosis treatment.

Radiographic Outcomes
Spinal deformity surgeons will never escape measuring radiographs because the measurements obtained provide the most precise method of describing the magnitude and specific features of a scoliotic deformity. The Cobb angle quantifies the magnitude of a curve, however, other measures of global spinal alignment are often more important. The normal relative position to the head, shoulders, trunk, and pelvis has been called balance. Radiographic measures of coronal balance include translation of C7 (cervical) or the chest relative to the sacrum and decompensation described as a state of being "out of balance".

Postoperative decompression of the trunk to the left sidde after instrumentation of a typical right thoracic, left lumbar curve pattern has plagued some surgeons seeking to achieve maximal Cobb angle correction of the thoracic curve. The importance of saggital plane alignment is also appreciated to a greater degree. Maintenance of a thoracic kyphosis and, particularly, lumbar lordosis are important for upright stance. Thus, the typical focus on the percentage of correction with a specific technique is inappropriate if done without consideration of global alignment. Similarly, the pattern and location of structural curves play heavily into the treatment required and the radiographic results of surgery.

Thoracic Scoliosis
The multihook dual rod posterior constructs introduced by Cotrel and Dubousset in the 1980s resulted in greater scoliosis correction, reducing the Cobb angle by 40% to 60%, and increased postoperative stability compared to the Harrington rod system. In the last decade the trend of increasing the number of bony anchor points and the greater use of pedicle screws in both the thoracic and lumbar regions increased the average Cobb angle correction for certain curve to nearly 80%. The risk of creating secondary deformities by overzealous correction must be recognised and managed. Minor curves that were left unfused in the era of limited potential correction od the main curve rarely caused difficulty, but now maximal corrextion had led some authors to recommend including some minor curves, thereby extending the length of the functional cost of the degree of deformity correction must be made for every patient. The anterior approach must be considered in this analysis because in some cases the length of fusion may be substantially less than with posterior methods. Current anterior methods (both open and endoscopic) have yielded correction comparison of a specific thoracic curve pattern (Lenke type), both surgical approaches (anterior and posterior) were effective in achieving deformity correction while maintaining overall balance.

The frequency of major complications has been similar across approaches as well, although the nature of the problem seems to depend on the approach. For example, late surgical site pain requiring implant removal and postoperative infection occur nearly exclusively with posterior procedures, whereas screw loosening and rod failure are more frequent with single anterior rod instrumentation procedures. This rate of rod failure has been cut approximately tenfold with the change from threaded to solid rods. Current systems use 4.5 to 5.0 mm stainless stell or titanium alloy smooth rods that fail in less than 3% of patients.

I have a stainless steel Harrington rod correction from T4 to L1 & compression rod from T6 to T10.

Double Major Scoliosis
In general, patients with structural lumbar and thoracic curves require fusion of both curves and are thus treated by posterior instrumentation techniques. Pedicale screw use in the lumbar portion of these curves has become standard, and improvement in correction compared to exclusively hook constructs has been clearly documented. Fusing much of the lumbar spine increases the physiologic demand on the remaining disks, emphasizing the importance of preserving as many distal lumbar levels as reasonably possible. The frequent lower level of fusion is L4, whicn results in twice the number of mobile disks compared to ending at L5. Use of segmental pedicle screw fixatioon and wide posterior release of the soft tissues, spinuous processes, and facetjoints may allow a shorter fusion compared to prior hook constructs and should be encouraged if a balanced fusion can be obtained. The goal of achieving a balanced correction remains.

We will continue with this thread on surgery including the risks associated with scoliosis correctional surgery.

Information from American Academy of Orthopaedic Surgeons

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