**2.3. Surgical technique**

otherwise healthy teenagers during puberty. Mild or moderate curves pose no health threats but may be associated with cosmetic concerns. Teenagers with mild deformities are placed under clinical surveillance and are encouraged to exercise, those with larger curves (more than 25°) are braced, while skeletally immature patients with thoracic curves exceeding 45° are candidates for surgical intervention [2]. Patients with thoracolumbar or lumbar curves usually undergo surgery with a lower than the traditional 45°Cobb angle threshold [3]. The standard surgical procedure for AIS is a spinal fusion of 8–10 vertebrae. Although surgical fusion is a successful solution for progressive spinal deformity, fusion leads to loss of spine mobility and may cause painful disc degeneration at the junctions of the mobile spine with

Non-fusion surgical solutions addressing moderate AIS curves may, therefore, be desirable alternatives to the traditional standard care of fusion. To this end, growth-modulating nonfusion procedures have been developed such as convex vertebral body stapling and/or convex vertebral body tethering as a surgical alternative for idiopathic scoliosis [4–6]. Stapling or tethering necessitate an anterior surgical approach to the spine and are both relatively extensive procedures. An intermediate posterior fusionless and less complex surgical approach for moderate AIS may be helpful. The ApiFix® system was developed to fill this missing gap [7]. ApiFix® is a new posterior dynamic device consisting of an expandable ratcheting rod anchored by two pedicle screws to the concave side of the scoliotic spine. Surgery is performed without the addition of spine fusion of the instrumented segments. Deformity correction is achieved by distraction leading to rod elongation. Curve correction is achieved not only during surgery but also after the surgical procedure by performing scoliosis specific exercises. These exercises activate the ratchet with further rod expansion and curve reduction.Early experience with the ApiFix® device showed it to be a viable alternative to fusion in reducing and maintaining

**2. Indications, implant design, surgical technique, postoperative exercises**

The implant is designed to be used in patients with AIS, aged 10–17 years, with a single major curve, either Lenke type 1 or Lenke type 5 curves, with a Risser sign between 0 and 4. The magnitude of the major curve should be between 30° and 60° and adequate flexibility on supine side bending views showing curve diminution to 35° or less. The device may be also used in individuals with smaller curves as an internal brace, especially in non-compliant external brace users.

The device has a mini-ratchet mechanism that allows unidirectional elongation of an expandable rod. It is made out of titanium alloy with an Amorphous Diamond-Like Ceramic coating

the fused segments.

184 Innovations in Spinal Deformities and Postural Disorders

correction of moderate AIS curves [7].

**2.1. Indications**

**2.2. Implant design**

The concave side of the spine is exposed through a 10–12 cm incision usually from end to end vertebrae. The convex side of the spine is left undisturbed. Two pedicle screws are inserted into the end vertebrae and connected by the eye joints to the expandable ApiFix® device. The construct usually spans five to six disc spaces around the curve apex.

The distraction of the ratchet mechanism during surgery allows immediate correction of the deformity. No fusion is performed. The surgical procedure takes about 1 h, and blood loss is negligible. Intra-operative neuro-monitoring is utilized during surgery. Hospitalization is very short, i.e., 1–2 days. Patients are immediately mobilized without external support.

**Figure 1.** (A) The ApiFix® device, the expandable rod, and the control pin and (B) close-up of the ratchet and the control pin.

#### **2.4. Postoperative exercises**

Postoperative exercises were designed to activate the ratchet mechanism and to further elongate the distance between the pedicle screws. Two to three weeks after surgery, patients are directed to perform five basic Schroth-like exercises that enabled gradual elongation of the ratchet mechanism, leading to further curve reduction (**Figure 2**). The patients bend towards the corrective direction, and the device maintains the designated correction after the patients' return to the neutral position. There are five basic exercises:

(1) Hanging from an open door or bar; the exercise begins with both hands holding the door top with the hips and knees bent at 90°, while the knees and toes lean on the door. By extending the

**Figure 2.** (A) Hanging from a door or bar, (B) chair bends, (C) bending on a roll, (D) lying on two chairs, and (E) bending over the band.

hips and knees, a traction force along the instrumented spine is exerted elongating the device. The maneuver is repeated five times. (2) Sitting on a chair with the backrest against the right rib cage (in Lenke type 1 curves). The right-hand leans on the backrest and the left one is placed over the head. The torso is leaned toward the backrest and right hand. The exercise is repeated 10–15 times. (3) Side bending on a rigid cylinder or roll placing the roll under the right rib cage. The right hand is bent under the head and the left one is placed over the head. The left arm is stretched above the head. (4) Lying on two chairs and a roll. A bolster is placed on the chair closer to the exercising individual. The patient lies on the bolster over the right side. The left hand is stretched over the head toward the second chair. (5) Standing tilts with a band. The band is placed on the right rib cage creating a fulcrum over which the torso is bent to the corrective side.

For Lenke type 5 curves, exercises are slightly modified by applying the band or bolster to the lower ribs or even to the waist usually on the left side of the body.

The patients are instructed to perform the exercises for 30 min daily, for 3–6 months after surgery. No braces are used and no restrictions on physical activity are imposed on the adolescents.
