"Normal spines have lordotic curves in the cervical and lumbar spine and a kyphotic curve in the thoracic spine for equal distribution of force across the spinal column. This allows people to stand in an upright posture and achieve forward gaze with minimal effort. But, when the spine is imbalanced in the sagittal plane, it takes more energy to stand erect, ambulate and maintain a horizontal gaze. This results in pain, functional disability and deformity," explains Steven J. Tresser, MD, a neurosurgeon at Neurological Specialties in Tampa, Fla.
"Restoring the spine to sagittal balance, when possible, eliminates this problem," says Dr. Tresser. "There is a growing body of evidence that surmises that after a lumbar spinal fusion procedure an increased moment arm is created above the fusion construct. This moment arm contributes to the development of adjacent level degeneration and proximal junction kyphosis as it is relates to sagittal imbalance. Establishing normal sagittal balance at the time of the fusion procedure hopefully can reduce these delayed failures."
In some patients a Pedicle Subtraction Osteotomy (PSO) is required to achieve sagittal balance. In these cases, hyperlordotic options like 16 and 20 degree Integrated Interbody implants can support better outcomes. "PSOs are big open procedures that result in long operations with significant blood loss and other significant associated morbidities," said James Billys, MD, a spine surgeon with Florida Orthopaedic Institute in Brandon, Fla. "Anterior reconstruction employing the use of hyperlodotic implants accomplishes comparable sagittal balance to PSOs with significantly less surgery time with decreases in blood loss and other morbidities."
The MIDLINE II device has been designed to meet the surgical demands of restoring sagittal balance while striking a balance between STALIF’s historical clinical success and its new, surgeon-driven features. The device provides original benefits of STALIF with compressive lag fixation while also requiring a reduced surgical envelope and an increased graft area. MIDLINE II is available in 8, 12, 16, and 20 degrees of lordosis to support restoring of sagittal balance.
"Centinel Spine's MIDLINE II is an important tool in my practice because of the variety of options that are available," says Dr. Tresser. "MIDLINE II has up to 20 degrees of lordosis, which matches the angles needed at the L4-L5 and L5-S1 segments. Since more than two-thirds of normal lumbar lordosis comes from these levels, an ALIF procedure with a MIDLINE II device is a very powerful method of re-establishing lordosis and thus correcting sagittal balance."
When cage lordosis increases, implant fixation becomes even more important. MIDLINE II can negate the need for supplemental fixation because it offers:
• 6mm diameter cancellous lag screws that ensure fixation in cancellous bone while providing endplate compression against the implant and bone graft, in line with Wolff's Law for bone healing;
• Carefully designed screw angulation that enhances stability and reduces bending moments on the screws, to mitigate risk of screw back-out and stress shielding;
• ABO screws (Anti Back-Out) that incorporate a retention feature, which provides an added layer of security.
"The STALIF lag screw design provides compression on the interbody implant, allowing greater control for the surgeon on the graft/bone interface," says Dr. Tresser. "MIDLINE II is a well thought out and designed implant system. I have been extremely happy with the system and the clinical results."
Centinel Spine will fully release its Ti-ACTIVE coated MIDLINE II-Ti device this year. Ti-ACTIVE is a texturized titanium coating that is applied through a proprietary application process with reproducible and uniform thickness, as well as controlled porosity. The texturized coating creates a three-dimensional topography that delivers immediate implant stabilization. Furthermore, the surface has been shown to enable cellular attachment and proliferation as observed on representative test coupons coated with Ti-ACTIVE.1
"I'm a big believer in STALIF technology, as it offers the advantage of achieving the same fusion rate as other approaches while also having less recovery time than posterior fixation options. Adding the titanium coating to this technology is state of the art; it improves initial fixation, making the implant more secure, and allows bony apposition to the implant endplates," explains Scott L. Blumenthal, M.D., a spine surgeon with the Texas Back Institute in Plano, TX.
Dr. Tresser concurs, "The Ti-ACTIVE implant [MIDLINE II-Ti] provides better immediate stability and cellular attachment than competitive PEEK-only products with much better radiographic ability to assess fusion than titanium-only products. It's a great step forward."
1Yoon BJV, et al.. Polishing methods less a factor in cell adhesion than surface characteristics of titanium plasma spray coatings on PEEK. LSRS 2015 Paper, Chicago, IL.
*This article is sponsored by Centinel Spine.