Original Editors - Assia Dad Soumaya Ajattar Gülcan KaratasSefora Bakkiouias part of the Vrije Universiteit Brussel's Evidence-based Practice project
Instability in the thoracic spine is as lumbar instability. If this instability in thoracic spines is present, it manifests as a spondylolisthesis or the forward translation of the cephalad vertebra on the caudal one.
Furthermore lateral listheses in thoracic spines are rare, possibly due to restraints provided by the rib cage and the uncovertebral joints. The degenerative thoracic spondylolisthesis is uncommon, as the thoracic spine is inherently more stable in the anterior to posterior direction than the cervical or lumbar. This is due to the rib cage and the coronal orientation of the facet joints.☃☃☃☃☃☃Instability is a loss of the functional integrity of a system which provides stability. The osteoarticularligamentous and the myofascial are two systems in the thorax that contribute stability. In the midthorax the rotational instability involves the spinal and costal components of the segment.  (Level of evidence 2C)  (Level of evidence 5) (Level of evidence 5)
Clinically Relevant Anatomy
The costovertebrals joints and rib cage are very important when it comes to stabilizing the thoracic spine.
The rib cage is fixed to the thoracic spine by the costovertebral joints, which consists of costotransverse joints and joints of the head of the ribs. Thoracic vertebrae are connected to adjacent vertebrae by the bilateral costovertebral joints.
The costovertebral joints and their surrounding ligaments, such as the costotransverse, superior costotransverse, radiatie, and intra-articular ligaments, connect nearby vertebrae and ribs.  (Level of evidence 2C)
The biomechanical and stabilization role of the costovertebral joints and rib cage in the thoracic spine is evidential, even more in lateral bending and axial rotation. When the posterior elements and bilateral costovertebral joints are destroyed, the thoracic spine may become unstable. The costovertebral joints are important stabilizers of the thoracic spinal motion segments.  (Level of evidence 2C)  (Level of evidence 5)
There are many causes that induce thoracic spondylolisthesis. The first cause is the dysfunction of the intervertebral disc which can lead to instability because of a lack of disc height. Furthermore this leads to a relative laxity in the motion segment. ‘Horizontalization’ of the lamina is the second cause that can lead to instability.
Lastly, thoracic instability can occur due to severe spondylosis or the presence of a long segment surgical arthrodesis below the unstable segment. 
The state of the costovertebral joints and rib cage should be assessed to evaluate the stability of the thoracic spine.  (Level of evidence 2C)
The rotational instability of the thorax will cause an increase in the neutral zone. This instability is palpated during segmental lateral translation test. The unstable segment has a softer feel of motion, an increased quantity of translation and variable symptom response. The test may provoke pain if the joint is irritable. When the instability is long standing and asymptomatic, the tests are mostly not provocative.  (Level of evidence 5)
The second test for lateral translation stability (rotation)  (Level of evidence 2C) is to evaluate the stability of a midthoracic segment.
It is necessary to first determine the available mobility in lateral translation. The most instability can be found in the region between T3- T7.
This motion is tested in the following manner: the patient is sitting with his arms crossed on his chest. The therapists’ left hand fixes the transverse process of T6. With the other hand you translate the T5 vertebra and the sixth ribs to the right in the transverse plane.
The quantity and the end feel of motions are reported and compared to the levels above and below.
The stability of the T5-6 spinal component can be assessed by constraining the sixth ribs from gliding relative to their transverse processes and then applying a lateral translation force. No motion should occur when the ribs are fixed.
Physical Therapy Management
- Conservative management should be attempted and considered as first-line treatment on patients with suspected iatrogenic instability resulting from posterior foraminotomy.  (Level of evidence 2A)
- The thoracic spine can be regarded as a hidden source for improving overall postural stability. It may be suitable to focus on thoracic region in the kinetic chain for the treatment or training.  (Level of evidence 1B)  (Level of evidence 5) (Level of evidence 5)
- The multifidi and erector spinae muscles contribute to force closure of the midthoracic region. Therefore it is really important that these muscles have to be addressed in the rehabilitation of the unstable thorax. The region can become dynamically stable and the neutral zone can be controlled, through appropriate training.  (Level of evidence 2C)  (Level of evidence 5)
- The exercise programs were composed of 10 min- warm-up exercises, 40 min-stabilization exercises, 10 min-cool-down, and stretching exercises in a group set-up. If needed a gymnastic ball or proprioceptive, balance and resistive work can be integrated into the program. The exercise velocity can be increased according to the patients work and recreation demands. The load should be applied bilaterally and then progressed to unilateral work. 
The program consists of:
- General exercises for the spine: The contraction of the related muscle activity according to the spine segment with the usage of Stabilizer Pressure Biofeedback unit (Chattanooga,USA). The training programs aimed at creating neutral spine and activation of deep muscles of the spine.
- Specific exercises for the thoracic spine: Postural alignment and minimal multiﬁdus activation with scapular orientation for thoracic group. The participants were asked to maintain the positions and contractions during the exercises and throughout the day as much as possible.
- Abdominal bracing was also shown to be one of the most effective exercise techniques for muscles even compared to dynamic exercises involving trunk flexion/ extension movements. Furthermore abdominal bracing should be included in exercise programs when the goal is to improve trunk stability. Moreover, abdominal bracing also shows an increase in stiffness of the spine, promoting stability in the vertebral segments, and is frequently recommended and/or included in rehabilitation. Further investigation focusing on its actual effects on spinal stability in rehabilitation is needed.  (Level of evidence 2B)  (Level of evidence 4). Also along Skoch, Jesse et al. further investigation is needed to determine when and if (post operative) bracing for surgically stabilized thoracolumbar fractures is indicated. Controlled studies should include a careful analysis of pseudoarthrosis and complication rates.  (Level of evidence 1A)
- D.G. Lee, Rotational instability of the mid-thoracic spine : assessment and management, 1996, Manual Therapy (Level of evidence 2C)
- O'Sullivan, Peter B. "Masterclass. Lumbar segmental ‘instability’: clinical presentation and specific stabilizing exercise management." Manual therapy 5.1 (2000): 2-12. (Level of evidence 5)
- Panjabi, Manohar M., Jeff N. Hausfeld, and Augustus A. White. "A biomechanical study of the ligamentous stability of the thoracic spine in man." Acta Orthopaedica Scandinavica 52.3 (1981): 315-326. (Level of evidence 5)
- I. Oda et al, Biomechanical role of posterieur elements, costovertebral joints, and rib cage in the stability of the thoracic spine, 1996, Spine (Level of evidence 2C)
- A. Zahrai et al, Cervical and thoracic degenerative spinal instability, 2013, Semin Spine Surg (Lvel of evidence 3A)
- A.J. Bevevino et al, Iatrogenic spinal instability: Cervical and thoracic spine, 2013, S E M IN S P I N E S U R G (Level of evidence 2A)
- D.O. Kaya et al, Effects of different segmental spinal stabilization exercise protocols on postural stability in asymptomatic subjects randomized controlled trial, 2012, Journal of back and musculoskeletal rehabilitation (Level of evidence 1B)
- Liebenson, Craig, ed. Rehabilitation of the spine: a practitioner's manual. Lippincott Williams & Wilkins, 2007. (Level of evidence 5)
- S. Maeo et al, Trunk Muscle Activities during Abdominal Bracing: Comparison among Muscles and Exercises, 2013, Journal of Sports Science and Medicine (Level of evidence 2B)
- F.J. Vera-Garcia, J.L. Elvira, S.H. Brown and S.M. McGill, Effects of abdominal stabilization maneuvers on the control of spine motion and stability against sudden trunk perturbations, J Electromyogr Kinesiol 17(5) (2007), 556-67 (Level of evidence 4)
- Skoch, Jesse, et al. "Bracing after surgical stabilization of thoracolumbar fractures: a systematic review of evidence, indications, and practices." World neurosurgery 93 (2016): 221-228.(Level of evidence 1A)