Temporary Internal Distraction for Severe Scoliosis
Authors: Badin Daniel , Skaggs David L. , Sponseller Paul D. 
Published: August 2022

Background:
Temporary internal distraction (TID) is a surgical technique that can be utilized to correct severe scoliotic deformities. It allows the correction of severe curves (i.e., exceeding 90° to 100°) while minimizing the risk of neurologic injury associated with large corrections
1,2
.

Description:
TID can be performed as a single or staged procedure. During the first part, cephalad anchors are placed on the spine or ribs, and caudad anchors are placed on the spine or pelvis. Temporary distraction rods are inserted, osteotomies and/or releases are performed, and iterative distractions are utilized for the duration of the procedure. If adequate correction is achieved, the final fusion may be completed at this time. If not, a staged approach may be performed: the wound is closed and the patient is returned to the operating room 1 to 3 weeks later, at which time the temporary rods are removed, further distraction is performed, and the final fusion instrumentation is placed. Around 80% to 90% cumulative correction of the major coronal angle should be achievable.

Alternatives:
The mainstay of treatment for large scoliotic curves is typically surgical correction and fusion. The main alternative to TID is traditional halo-gravity traction followed by fusion
3–5
. In rare cases, nonoperative treatment may be appropriate if comorbidities and/or prognoses that preclude surgery exist.

Rationale:
Halo traction is an effective adjunct for the treatment of large scoliotic curves; nonetheless, it has several disadvantages. First, halo traction requires a prolonged hospital stay with restriction of mobility and interference with daily activities. Second, this procedure may be less effective in cases of lumbar deformity, in which halo traction achieves limited tensile forces. Third, this procedure is associated with several risks, such as cranial nerve injuries and pin track complications
3–6
. Finally, halo traction is contraindicated for certain conditions, such as cervical instability.
TID, on the other hand, involves the application of iterative corrective forces directly to the area of deformity, allowing a stronger correction
1
. TID takes advantage of the viscoelastic nature of the spine to achieve a higher percent correction compared with halo traction, with a low risk of neurologic injury
1,2
. TID also avoids the prolonged hospital stay, mobility restriction, and complications associated with halo traction. When performed as a staged procedure, TID allows accurate assessment of neurologic function with the patient awake and moving.
TID is most effective for severe scoliotic multisegment deformities rather than short rigid curves, which are better treated by osteotomies.

Expected Outcomes:
This procedure provides satisfactory outcomes and a low risk of complications. In our retrospective case series, TID resulted in a mean major coronal angle correction of 53% after the first distraction and 80% to 90% after definitive fusion
1
. The overall percent correction was higher than that reported for halo traction
1
.
The major risks of TID include infection and spinal injury. The risk of infection is decreased by antibiotic prophylaxis, perioperative nutritional optimization, and careful soft-tissue handling and wound closure. The risk of spinal cord injury is decreased by intraoperative neuromonitoring. Neuromonitoring changes occur in around 40% of cases, but these are almost always reversible and seldom lead to neurologic deficits if detected and appropriately treated, as described below
2
.
Although risks exist, no complications have occurred among the 32 cases we presented in our series
1,2
.

Important Tips:

Temporary anchors should be expected to loosen during distraction. Therefore, temporary anchors must be placed strategically so as to not jeopardize the purchase of the final implants.Gradual corrections must be performed over time, utilizing the viscoelastic nature of the spine to minimize risk of neurologic injury.Accurate neuromonitoring is essential for this procedure.If neuromonitoring changes occur, distraction must be stopped and the correction attained must be decreased.

Acronyms and Abbreviations:

TID = temporary internal distractionLIV = lowest instrumented vertebraAP = anteroposteriorTP = transverse processSAI = sacral-alar-iliacMAP = mean arterial pressureTPN = total parenteral nutritionVCR = vertebral column resectionJIS = juvenile idiopathic scoliosisAIS = adolescent idiopathic scoliosis