Achieving a 3D Biomechanical Goal with a Corrective TLSO
Due to the three-dimensional (3D) deformities and complexity of idiopathic scoliosis (IS), it is hard to achieve a well-balanced, properly aligned spine and a symmetric trunk with an orthosis. This article introduces techniques that orthotists can apply at each stage of treatment to achieve the identified 3D biomechanical IS goal using a corrective orthosis.
Strategies that can be used during the radiographic evaluation stage of a patient with IS include drawing a central sacral line (CSL) and making an iliac clavicular (IC) box on the radiographic image of the spine.
The CSL is a key reference line for the coronal plane and is used to determine the degree of decompensation at C7 (spinal imbalance). If the patient is decompensated at C7, consider building a trochanteric extension on the same side of the orthosis as the area of decompensation (Figure 1, Image 2). Analyze the posteroanterior and lateral views of the radiographs to determine which vertebrae are deviated from the CSL and to understand the severity of sagittal malalignment (Figure 1, Images 1 and 2). General ideas regarding where corrective forces need to be applied and what kind of pads are required, including the size and placement of the corrective pads, can be identified at this stage.
An IC box can be used to evaluate trunk shift and trunk balance (Figure 2). The IC box is a rectangular box drawn with two vertical lines that mark the widest lateral points of each ilium with two horizontal linesóone at the superior aspect of the clavicles and the other at the level where the ilium is the widest. This technique allows you to understand whether the overall trunk is shifted and where it is positioned in comparison to the pelvis. This radiograph technique can also be used at the end of the fitting procedure to determine if the in-orthosis spine is in balance with the trunk centered within the box (Figure 2, Image 3). Figure 2 shows samples of how these radiograph drawings are used to assess spine balance and trunk balance or symmetry.
During the patient evaluation stage, complete a physical examination of the patient, assess alignment of all three planes, and compare results to the information obtained from the radiograph.
Use your hands during patient evaluation to determine the location and amount of corrective forces, the degree of balance that occurs amongst several corrective forces, and the amount of flexibility that exists at each curve. Push your hand gradually, medially directed, on the curve prominence at the area most displaced laterally, which is the location of the primary curve, or on the lowest structural curve if the patient has a double curve. After this first force is applied, use the other hand, medially directed, to apply a corrective force on the location of a second, lower structural curve in an opposing direction, as part of the three-point correction principle that maintains the ideal alignment and balance of the spine and trunk. As shown in Figure 3, first place your left hand on the patientís left lumbar curve region while applying a counterforce with your right hand on the patientís right gluteus medius area. Then, while you move your right hand from the gluteus area and push on the right thoracic prominence, move your left hand and hold the area under the patientís left axilla if needed.
For optimal sagittal alignment, the placement of the posteriorly or anteriorly directed forces is also determined by applying your hands on the patient. The posteriorly directed force provides the spine more flexibility by unlocking the facets and the posterior structures of the vertebrae on the structural curve area and then maximizes curve correction (Figure 4). To address the excessive lumbar lordosis and the excessive anterior pelvic tilt, use your hands to place a posteriorly directed force on the abdomen and an anteriorly directed counterforce on the gluteus maximus. For a loss of relative thoracic kyphosis, place your hands on the inferior-anterior area of the ribcage to assess the sagittal alignment. An anteriorly directed force may be needed on the proximal scapula area as a counterforce if the patientís head is not aligned properly in the sagittal plane after applying all posteriorly directed forces mentioned above for optimal sagittal alignment (Figure 4).
The hand evaluation technique also helps to determine curve flexibility. Curves are considered flexible when the patient is able to self-correct or bring him or herself to a compensated position against the forces you applied at the location of the structural curve(s). If the patient is self-corrected, there is no counterforce or corrective force needed on the left side of the axillar area (Figure 3). If C7 decompensation occurs during this assessment and the patient is unable to self-correct, consider reducing the degree of the force applied or consider applying a counterforce on the left axilla to ensure optimal alignment and balance.
In the casting stage, a standing frame is useful for achieving ideal alignment and balance in all three planes. Although greater flexibility and correction can be obtained with casting in supine, a standing position is used to increase the potential for orthosis tolerance and patient compliance since the patient will mainly be sitting or standing during daytime orthosis wear. Adjust the position of the standing frame so that the patientís shoulders are level and derotated if the shoulders present as rotated or adducted due to a thoracic curve. The kneepad of the standing frame is used to aid in reducing the patientís lordosis.
A two-stage wrapping technique can be used during casting. Cast from the inferior to the superior direction, first wrapping the area of the pelvis to the lower margin of the rib. The pelvic section is stabilized and secured first, as a base of support, so that forces can be applied to the upper torso without ruining pelvic rotation and without causing misalignment during the second stage. In the second stage, wrap the patient from the waist to the clavicles anteriorly and from the waist to mid-scapula posteriorly, crossing the axilla, and initiating the casting once the first half of the plaster wrap is almost firm.
During this wrapping process, perform hand evaluation techniques and apply forces to the areas in need of correction or alignment while the plaster is still malleable, including a derotational force to the trunk at the area where rotation is observed (Figure 5). Compression is also applied to the abdomen at this time, if needed. The hand impressions that are made at the time of casting serve as a guide during the modification stage.
Ensure that the negative cast is in neutral alignment in all three planes before filling it with plaster. The bilateral waist grooves or the pelvis should be level horizontally if a patient does not have a pelvic obliquity. If the model is not aligned, place wedges under the base to ensure it is level prior to filling the coronal and sagittal planes with plaster. If the negative model itself is out of alignment, cut it at the point of malalignment and then tilt or shift the model to realign it in all three planes (Figure 6). For example, if the model has a thoracic hyperextension, the hyperextended segment can be cut, and the model can be shifted into a more flexed degree in the sagittal plane (Figure 7). If any rotation still exists, such as a rotation on the pelvis or the upper trunk, especially on the spinal segment that has a structural curve, it is easy to cut and derotate the pelvis or the segment at this stage (Figure 8).
Once the negative model is filled, begin modifying the positive model by drawing the CSL on the model. The areas of the positive model that are needed to address corrective forces, derotational forces, or compensatory forces should be removed based on previous radiographic reviews, the patient evaluation, measurement results, and the markings left on the cast (i.e., hand impressions made when corrective forces were applied during the casting phase).
For a thoracic curve, carve plaster away from the lateral and lateral-posterior area of the model at the location that corresponds with the ribs on the convex side of curve (Figure 9, Image 2). However, if the patient has thoracic hypokyphosis, removing plaster from the area that corresponds to the posterior area of the curve is not recommended in order to avoid increasing the flattening.
For a lumbar curve, carve plaster from the posterior area of the model at the location that corresponds with the lateral area of the paraspinal muscles or vertebrae on the convex side of the patientís curve. Also carve plaster from the area of the model that corresponds with the patientís abdomen and gluteus maximus area (Figure 9, Image 1).
If the torso of the model is rotated as compared to the pelvic section, add plaster at the location where derotational forces are needed. Plaster does not need to be removed from the area of the model that corresponds with the axillas if the medial-lateral measurements of the axillas of the model are equidistant from the CSL, since this means that the torso is balanced. If the axillary area is not equidistant from the CSL bilaterally, it is necessary to shape the model to obtain a result in which both sides from the CSL are equal (Figure 11).
Build up or add plaster to the model to ensure alignment and provide areas of relief for bony prominences. Add plaster or plaster bandages to the posterior and lateral areas of the model corresponding with the concave side of the curve as part of the orthotic active muscle component. This creates an opposing relief (trunk or spine shift) on the side opposite to where force is applied so that the ribcage can migrate laterally and posteriorly toward the concave side of the curve and can shift back into optimal alignment when corrective forces are applied on the convex side of the curve. The diagram in Figure 10, Image 2, shows where space will be added for the trunk or spine to shift; which addresses the needs of a patient with a right thoracic curve at T8/T9. If a patient has less kyphosis on the thoracic area, in order to improve thoracic sagittal alignment, space will also be needed around the posterior part of the spine where thoracic curve exists (or mid-posterior thoracic area). This is needed to pull the body into a more acceptable range of thoracic kyphosis (Figure 10, Image 1) when the posteriorly directed corrective force is applied on the anterior-inferior area of the ribcage. It is also necessary to add plaster in cases where the patient has excessive lumbar lordosis. The plaster is added to the midposterior lumbar area as shown in Figure 10, Image 1, to create space in the orthosis. After all modifications to the model are completed, the orthosis is ready for fabrication (Figure 11).
During fitting, add additional corrective pads in the orthosis to maximize correction, alignment, and balance. For example, a gluteus medius pad may be added to serve as a counterforce to aid in lumbar correction; an axillary pad may be needed as a counterforce to the thoracic pad; and a trochanteric pad with an extension may be added on the same side as the C7 decompensation to redirect the head back to coronal balance. To improve thoracic hypokyphosis, a flexible hypokyphosis panel is often attached to increase the posteriorly directed force on the anterior part of the ribcage and torso (Figure 12, Image 1). This kind of panel allows the patient to breathe more easily than using a plastic trim line of the orthosis as a force.
Trim lines are also customized to the needs of each patient for alignment and balance in all three planes. For example, for a patient with a flexible thoracic hypokyphosis or less kyphosis, the superior-posterior trim line should be positioned around the proximal scapula area (Figure 12, Image 3). This provides an anteriorly directed counterforce against the posteriorly directed corrective force on the anterior thoracic region. The superior-anterior trim line for this same patient should be positioned inferiorly as compared to the posterior trim line. However, if a patient has a rigid thoracic curve and C7 decompensation, the superior-anterior trim line may need to be placed superiorly as compared to the superior-posterior trim line. This directs all corrective forces (medially directed, posteriorly directed, and coupled derotational forces) to the upper thoracic region and on the ribs of the axilla area on the opposite side of the thoracic curve or on the side of the C7 decompensation. In the latter case, an anterior sternal bar is useful to place appropriate force on the upper thoracic and axilla regions. The anterior sternal bar is not only used for correction but is also used to enhance the stability of the orthosis (Figure 12, Image 1). Lateral trim lines are also used during the fitting stage. To allow level shoulders with a patient with a thoracic curve, a lateral trim line is placed on the concave side of the curve in a position that is higher than the trim line located on the convex side of the curve.
It is also important to check the final placement and degree of the pad pressure during the fitting stage. Mount a lumbar pad on the posterior aspect of the orthosis on the lateral side of the paraspinal muscles at the apex and below apex levels of the convex side of the lumbar curve. The superior edge of the thoracic pad has to mount on the lateral side and corner of the lateral-posterior area of the rib that is attached at the apex of the convex side of the curve (Figure 12, Image 2).
A well-balanced and properly aligned spine with a symmetric trunk is an important goal to achieve for the 3D treatment of IS. Throughout each stage of treatment, you must make critical decisions to meet the patientís needs. When applied correctly, it is expected that these techniques will allow you to achieve better treatment outcomes for your patients with IS.
Sun Hae Jang, MSc, CO, vice-chair of the Academyís Spinal Orthotics Society, is a research scientist for Gillette Childrenís Specialty Healthcare, Blaine, Minnesota. She is also an assistant professor in the Master of Science in Orthotics and Prosthetics program at Eastern Michigan University, Ypsilanti.
Jennifer A. Hutson, MS, OTR, OTL, ATP, is a seating specialist for Gillette Childrenís Specialty Healthcare, St. Paul, Minnesota. She is an assistant professor in the Master of Arts in Occupational Therapy program at St. Catherine University, St. Paul.
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