Surgical intervention for idiopathic scoliosis dates all the way back to 1865 (France) and resulted in one of the first medical malpractice cases (which later paved the way for the concept of evidence-based medicine). From its controversial beginnings, the discussion has continued on through the decades as newer surgical techniques and hardware became available — with the Harrington rods in the 1960s through the mid 1980s, and the Cortel-Dubousset (C-D) hooks and rods instrumentation as its current predecessor.

ApiFix Internal Brace Option (MID-C Implant)

In 2003, noted scoliosis researchers Stuart Weinstein and Lori Dolan published a 50-year natural history follow-up study documenting the health and function of patients with untreated idiopathic scoliosis. Based on the long-term data collected from patients, they concluded that untreated adults with late idiopathic scoliosis (LIS) are productive and functional at a high level at 50-year follow-up. Untreated LIS causes little physical impairment other than back pain and cosmetic concerns.

This finding contrasted sharply with the alarmingly high rate of post scoliosis fusion complications only 15 to 20 year postoperative procedure, calling into question the efficacy of the procedure if it did not provide a favorable long-term cost/benefit for the patient. These long-overdue discussions spurred on a sense of urgency to devise, develop, and study less invasive and more motion-sparing surgical interventions for scoliosis.

The development of the Minimally Invasive Deformity Correction (MID-C) System by ApiFix is the direct result of one of those aforementioned discussions to replace scoliosis fusion surgery as the sole posterior surgical approach for treating idiopathic scoliosis.


The MID-C device by ApiFix is described as a miniature ratchet mechanism surgically screwed to the patient’s posterior spine on the concave side of the spinal curvature, resulting in a short peri-apical fixation with actual curve correction achieved on the operating table as part of the post operative procedures.

Additional correction can sometimes be obtained following surgery, the ratcheting rod expands in small increments during lateral bending exercises and stretching in the weeks/months following the procedure or during remaining growth.

The ApiFix procedure may be appropriate for patients with flexible idiopathic scoliosis Lenke classifications 1 & 5 who have adequate bone density to hold the necessary surgical screws that attach the ratchet device to the posterior aspect of the curve apex at the superior and inferior vertebral levels of the curve.

  • Lenke 1
    Primary thoracic curve with minimal lumbar curve centered over the center mass of the pelvis
  • Lenke 5
    Primary thoraco-lumbar curve with little-to-no upper torso translation from the midline


Curve flexibility is a crucial and critical element to be a candidate for the MID-C ApiFix procedure. Spinal curvatures must be less than 60 degrees Cobb angle and bend to 30 degrees or less on lateral bending x-rays — or with a forced lateral fulcrum bending x-ray prior to recommendation for the procedure.

While curve flexibility in idiopathic scoliosis remains poorly understood, increasing curve size and age of the patient are correlated with increased curve rigidity in most cases.

Anecdotal evidence suggests many of the spinal preparation procedures utilized in the ScoliSMART protocols increase curve flexibility after short but intensive bouts of treatment. In addition, several studies utilizing manipulation under anesthesia (MUA) on adult scoliosis patient have shown promise for improvements in spinal range of motion and curve flexibility.

It is theorized that either or both protocols could be offered as a preparation program in order to help patients quality for ApiFix or spinal tethering procedures in the future.

FDA Approval for the ApiFix MID-C Implant Mechanism

On August 23, 2019, the FDA approved ApiFix’s MID-C device under the human device exemption (HDE) provision. The criteria of recommending the device and procedure was limited to:

  • Curves less than 55 Cobb angle degrees
  • Below the spinal level of T2 (2nd thoracic vertebra)
  • No spinal cord abnormalities
  • Motor neurological deficit
  • Sufficient bone density to hold the surgical screws used to attach the device
  • Thoracic kyphosis greater than 55 degrees from T5-T12

Advantages and Concerns/Considerations of the ApiFix Device and Procedure

The benefits of non-fusion surgical techniques are rather obvious in regards to being less invasive, and allowing more preservation of motion as compared to traditional fusion, but some of the other advantages of the ApiFix approach specifically include:

  • Less hospitalization time (3 days vs 7 days post fusion)
  • Less overall surgery/anesthesia time (vs. fusion)
  • Smaller scar (20 cm vs. 45 cm post fusion)
  • Less blood loss (vs. fusion)
  • Faster recovery time (vs. fusion)

As with all new technology and innovations, concerns and considerations need to be fully evaluated and studied over a long period of time to determine the actual risk:benefit ratio for patients before choosing any surgical procedure. Many of the risks of ApiFix have yet to be completely understood or determined:

  • Despite the manufacturer’s claims of motion-sparing polyaxial joints, the spinal segments bridged be the device are fixated, thus resulting in a short fusion effect biomechanically
  • The rate of re-operations for ApiFix procedures is higher than traditional spinal fusion
  • The intermediate and long-term data is sparse to non-existent on only a small number of patients
  • Although the amount of surgical hardware is reduced, metal implant sensitivity concerns with the surgical implant still exist
  • Long term “wear and tear” of the ratchet device may be subject to fatigue stress over the course of a normal lifetime

The FDA-approved Minimally Invasive Deformity Correction (MID-C) device by the ApiFix corporation is the latest innovation in non-fusion surgical procedures for idiopathic scoliosis and continues the push for less invasive procedures that began over 15 years ago.

While this approach has some distinct advantages over traditional fusion surgeries, it is only appropriate for a limited number of curve patterns and clinical conditions. A non-surgical approach to treating idiopathic scoliosis is still the most preferred option by parents, patients, and clinicians as the long-term benefits of surgical intervention remains largely unknown at this time.