THE MINUTEMAN G3 DESIGN RATIONALE
The Minuteman G3 is a minimally invasive, interspinous-interlaminar fusion device intended for the temporary fixation of the thoracic, lumbar and sacral spine while awaiting bony fusion to occur. It is designed for attachment to the posterior non-cervical spine at the spinous processes through its bilateral locking plates, and is intended for use with bone graft material placed within the device. The Minuteman G3 provides immobilization and stabilization of the spinal segments while used as an adjunct to interbody fusion. The core threaded post provides controlled distraction, while a wide range of sizes allows for enhanced anatomical fit. The Minuteman G3 can easily be placed under fluoroscopy through a percutaneous lateral approach or a posterior mini-open unilateral approach. The Minuteman G3 is delivered sterile and individually packed.
INDICATIONS FOR USE
The Minuteman G3 is a posterior, non-pedicle supplemental fixation device, intended for use at a single level in the non-cervical spine (T1-S1). It is intended for plate fixation/attachment to spinous processes for the purpose of achieving supplemental fusion in the following conditions:
- Degenerative disc disease (DDD) (defined as back pain of discogenic origin with degeneration of the disc confirmed by history and radiographic studies)
- Trauma (i.e., fracture or dislocation); and/or
The Minuteman G3 is intended for use with bone graft material and is not intended for stand-alone use.
The device may be implanted via an open (T1-S1) or percutaneous (L1-S1) approach.
The Minuteman G3 components are not to be connected to the components of devices from another manufacturer. Titanium implants should not be mixed with stainless steel implants in the same construct. A successful result is not always achieved in every surgical case. This fact is especially true in spinal surgery, where many extenuating circumstances may compromise the result. The Minuteman G3 has not been evaluated for safety and compatibility in the MR environment. The Minuteman G3 has not been tested for heating or migration in the MR environment.
PercLIF – PREPARATION, POSITIONING & APPROACH
1. Preoperative Planning
Routine preoperative studies include AP and lateral x-rays (flexion and extension views are also recommended), MRI, or CT myelography. It is important to rule out gross instability, spondylolisthesis > grade I, significant scoliosis, severe osteoporosis, and ankylosed spinal segment. If the lateral percutaneous approach is taken L3-L4 or above, a preoperative CT is recommended to ensure safe trajectory to the spine. The lateral percutaneous approach may not be performed for levels above L1.
2. Patient Positioning
The patient should be placed in a prone position on a frame that decreases the lordosis of the spine and allows for the abdomen to not be compressed. It is advisable to tilt the pelvis by inclining the table at the level of the pelvis. This will allow for a natural distraction of the spinous processes. The frame and operating table need to be radiolucent in both an AP and a lateral plane.
3. LATERAL PERCUTANEOUS APPROACH – Targeting the Access Point
Using manual palpation and AP fluoroscopy, identify the midline of the spinous processes at the level to be instrumented and insert a spinal needle. Under lateral fluoroscopy, define the anatomical landmarks and project them onto the skin. A skin mark (shown in Blue) is made corresponding to the superior edge of the inferior spinous process. A second skin mark (shown in Magenta) is made corresponding to the inferior edge of the superior spinous process. A third skin mark (shown in Orange) is made corresponding to the posterior limit of the facet joint. Make a longitudinal incision of approximately 2.5 cm along the Orange line and between the Blue and Magenta lines.
Introduce the Guide Wire into the Aiming Device until it reaches the first Stop. The Guide Wire is inserted through the incision. Depress the Aiming Device Knob to increase the Guide Wire length. Under lateral fluoroscopy, carefully advance the Guide Wire between the spinous processes and pierce the interspinous ligament.
For optimal placement of the Minuteman G3, the Guide Wire must be placed as far anterior as possible.
Under AP fluoroscopy, advance the Guide Wire approximately 2 cm across the midline of the spine. Verify position of the Guide Wire with AP and lateral views.
Depress the Aiming Device Knob and carefully remove the Aiming Device from the Guide Wire. It is important to maintain Guide Wire position. The Guide Wire Extension is threaded onto the Guide Wire. The Guide Wire Extension helps maintain correct Guide Wire placement while inserting Dilators, Sleeves and other instruments.
Surgical Technique – IMPLANT SITE PREPARATION
Slide the 3 mm Soft Tissue Dilator over the Extended Guide Wire. Under AP fluoroscopy, the 3 mm Dilator is inserted through the skin incision while holding the Guide Wire in place. Insert the 3 mm Dilator until it is adjacent to the spinous processes. Repeat this technique for the 8 mm Dilator, 14 mm Dilator and the 20 mm Sleeve.
If facet hypertrophy does not allow for perpendicular docking of the Sleeve against the spinous processes, the Bone Rasp is inserted over the Extended Guide Wire and rotated clockwise to gradually reduce the mass of the facets. The Bone Rasp is brought close to the spinous processes, but is not inserted into the interspinous process space. Remove the Bone Rasp and leave the Guide Wire in place.
Under AP fluoroscopy, the Soft Tissue Rasp is inserted over the Extended Guide Wire and into the interspinous process space. The Rasp is rotated clockwise to partially remove the interspinous ligament and to partially decorticate the spinous processes. The Rasp is then removed and the Guide Wire is left in place.
PercLIF – IMPLANT SIZING
The Graduated Tap is inserted over the Extended Guide Wire. Under AP fluoroscopy, the Tap is threaded clockwise into the interspinous process space. Apply gentle force to engage the threads of the Tap with the spinous processes. As the Tap is advanced, the Tap gradually distracts the spinous processes. Once adequate distraction is obtained, the degree of distraction can be determined by viewing which Tap sizing hole is positioned between the spinous processes. This degree of distraction determines the appropriate implant size.
To determine the Minuteman G3 size, the Tap has sizing holes that correspond with the degree of distraction, and these holes can be visualized on AP fluoroscopy.
Slide the 23 mm Sleeve over the 20 mm Sleeve. Insert the 23 mm Sleeve until it is adjacent to the spinous processes. Repeat this step for the 26 mm Sleeve. Remove the 20 mm and 23 mm Sleeves, leaving the 26 mm Sleeve in place.