Lumbar Fusion : A New Anterior Only Option. The STALIF

STALIF Single Incision 360 o TM Pablo Pazmiño, MD Beverly Hills, CA

Lumbar Fusion Primary Aims of Treatment

Elimination of pain provocation

Removal of pain generator

Prevent movement through anterior column stabilization

Fusion of motion segment

Restoration of sagittal balance

Minimize morbidity

Preserve Muscle Function

Interbody Fusion Creating the Right Environment

Wide disc clearance

removal of all nuclear material

Provides broad surface for graft contact

Preparation of endplates

preserve load-bearing surfaces

good cancellous graft contact exposure

Load-sharing (Wolfe’s Law)

These two techniques help facilitate load sharing and contribute to overall spinal stability

Ideal Device

Greatest cross-sectional area for Stabilization / Bony Pillar

Rigid segmental fixation

Reduction of patient morbidity

Ease of device insertion

PLIF/TLIF Approaches

Pain source removed

Movement through disc prevented

Sagittal balance restored

Low associated morbidity

Muscle function preservation

Yes

Yes

Potentially

?

?

Achieved

MIS PLIF/TLIF

The Working Window

The TLIF requires resection of the facet which destabilizes but enables decompression.

Variances in approach and soft tissue retraction.

The MIS Approach

The Reality

Anterior-Posterior (360 o ) Approach Pain source removed Movement through disc prevented Sagittal balance restored Low associated morbidity Muscle function preserved Yes Yes Yes ? ? Achieved

Percutaneous Pedicle Screw Instrumentation Source: Spine-Health.com

In conjunction with A/P Reconstruction

Still causes posterior muscle disruption

Function as tension band only

Can not provide surface area for fusion

What about Cages & Anterior Lumbar Plating?

Vascular Anatomy Bifurcation – Variations ( high / low) Ilio-lumbar vein –Often ligated to access to L4/5 Pre-sacral vessels –Isolated /ligated to access L5/S1 Anterior Plates may have the potential to Erode Great Vessels/DVT

STALIF ™ VBR Design Rationale

Graft containment

Stable fixation of motion segment

Resistance to axial, torsional and bending movements

Eliminate the need for posterior fixation

Restoration of disc height

Restoration of lordosis

Radiolucency

MRI compatibility

Allow for large graft area

Bone Graft Volume

2.8cc 11mm ht, 8 degree, 25 A/P, 36 Width

5.9cc 17mm ht, 12 degree, 29 A/P, 45 Width

Reminiscent of Humeral Plating Systems

Screw Angulation and Pullout

The convergent screw pattern of STALIF disperse the forces over the mass of the bone that is in between the screws in addition to the surface area of the screw threads. This applies forces throughout the entire mass of bone – not just the bone around the threads.

In a convergent screw pattern rotational forces are applied to the mass of bone behind the screw as well as the threads.

Axial screw pullout strength for the STALIF in Cancellous bone is 1249N for 5.5mm Diameter screw/ 1310N for 6.5mm Diameter Screws (Parry, 2001)

Screw Pullout

Screw backout associated with bending while loads placed transverse to the long axis of the screw (Chapman, J Bio Eng 96)

Convergence of the screws as well creates a compound angle

Their trajectory towards the VB center tends to reduce the transverse bending moment

No reported screw pullout in 15 years

STALIF ™ VBR

Different Philosophy

Prior Strict mid-line implant placement with other devices (L7, Femoral Ring, Carbon Fiber Cage, etc…)

STALIF wide footprint resting on the apophyseal ring reduces subsidence

Allows for complete disc removal

Laterally and down to PLL

Posterolateral corners as well

Posterior osteophyte removal

Endplate preservation

PEEK Optima Load-Sharing Biomaterial

STALIF ™- Single Incision 360™ Pain source removed Movement through disc prevented Sagittal balance restored Low associated morbidity Muscle function preserved Yes Yes Yes Yes Yes Achieved

BIOMECHANICAL TESTING

“ Multidirectional Flexibility Properties of the STALIF Device versus Circumferential Spinal Arthrodesis: An In-Vitro Calf Spine Model”

Andy Cappuccino MD

Bryan Cunningham MSc.

Paul C. McAfee MD

Study Dates 12/21/05-3/16/06

Orthopedics Biomechanics Lab

Baltimore , Md

Study Objectives

Compare segmental flexibility properties of the STALIF TT VBR versus anterior stand alone cages and circumferential arthrodesis

2. Quantify and compare the load at failure under destructive loading conditions

MATERIALS AND METHODS

Specimen Preparation

28 fresh frozen calf lumbosacral spines L3-sacrum utilized

Randomized into four reconstruction groups (n=7 per group)

Thawed to room temp.

Potted in rectangular containers with 8 compression screws

Materials and Methods

Plexiglass motion detectors placed on the anterior aspect of L4, L5 and container base

2. Each marker equipped with 3 LED’s for detection by an optoelectronic motion measurement system(3020 Optotrak system)

FOUR STUDY GROUPS (L4-5)

1) LT PEEK Cages Alone (n=7)

Bilateral LT cages ( 19mm Dia. x 23mm Length ) (Medtronic Sofamor Danek, Inc.) were inserted from the anterior direction at the L4-L5 intervertebral level

2) LT Peek cages + anterior Pyramid plate with screws LT Cage + Pyramid Anterior Plate (n=7) The bilateral LT cages were augmented using the Pyramid Anterior Plate (Medtronic Sofamor Danek, Inc.), which was inserted anteriorly spanning the operative L4-L5 level. Two screws were inserted at the inferior level and one superiorly

3) STALIF VBR

STALIF VBR (Paradigm BioDevices, Inc.Rockland, MA).

The number of fixation points was increased from two four to evaluate the effect of increasing fixation points

4)Anterior LT Peek cages and posterior Isola pedicle screw-rod instrumentation

Bilateral LT cages were inserted from the anterior direction at the L4-L5 intervertebral level, followed by posterior ISOLA pedicle screw / rod instrumentation (Depuy-Spine, Inc.) to create a circumferential spinal arthrodesis.

STUDY GROUPS

MULTIDIRECTIONAL FLEXIBILITY TESTING

Six pure non-destructive moments were applied to ensure multidirectionality

Axial rotation (Y-axis +/- 6Nm)

Flexion/extension (X-axis +/- 6Nm)

Lateral bending (z-axis +/- 6Nm)

Load applied to proximal specimen end

Intact Reconstructed specimen

All specimens tested on six degree of freedom spinal simulator

All specimens followed by Optotrak motion analysis

All specimens underwent continuous irrigation with 0.9% NaCl solution during testing

MULTIDIRECTIONAL FLEXIBILITY TESTING

TESTING SEQUENCE OF SPINAL CONSTRUCTS

Intact spine

Reconstructed Specimen

Destructive Extension load to failure

DESTRUCTIVE TESTING

Extension moment applied using an MTS858 system

Rate of 5 degrees per second to quantify peak moment at failure

Specimen/device failure was indicated by a significant decrease (approx. 30%) in applied moment as indicated on real time load-displacement tracings

DATA AND STATISTICAL ANALYSIS

ROM calculated as the sum of the neutral and elastic zones (NZ + EZ = ROM) and represents the peak total range of motion at the third loading cycle

Analysis conducted within the 3 dimensional conceptual frame work of Panjabi

Statistical analysis includes a one way analysis of variance (ANOVA) to compare differences within groups and a Student –Newman-Keuls test to compare differences across treatment groups

P < 0.05 was considered statistically significant

Biomechanical Data

NON DESTRUCTIVE ROM AXIAL ROTATION Error bars represent one standard deviation and significance is indicated at p<0.05. Intact demonstrated more motion compared to LT Cages+ pedicle screws and STALIF groups (p<0.05).

LATERAL BENDING ROM : Z Axis . No other comparisons between the six reconstruction groups were statistically significant (p>0.05) (One Way ANOVA: F=24.32, p=0.000)

FLEXION-EXTENSION ROM No S. differences were noted between STALIF and LTPS construct (p>0.05) (One Way ANOVA: F=26.55, p=0.000)

EXTENSION LOAD TO FAILURE LT Cage combined with pedicle screws as producing the greatest mean moment at failure compared to the remaining treatments, however, was not statistically different from the other treatments (p>0.05

FAILURE – LT Cages Alone

Fracture/ripping of residual annulus at operative level

FAILURE – LT Cage + Pyramid

Fracture of the vertebral endplate at the operative level

Usually at the single screw site

LT cage + Pedicle Screw Failure

Failure was similar to LT cages alone with tearing through the residual annulus

Screw cutout through the vertebral endplate at the operative level

STALIF OUTCOME

Fracture of the vertebral endplate at the operative level. In all cases a trapezoidal mass of bone dislodged between the triangulated screws

Clinical Experience

Several Peer-Reviewed Studies

Multi-Center Safety & Efficacy (IMAST ’07)

Clinical Study (Journal of Spinal Disorders ’01)

Biomechanical Comparison (IMAST ’06)

ProDisk Case Study (Spine 2005)

Safety and Efficacy Questions Answered

What is the fusion rate with STALIF?

Did the construct do what we wanted it to?

Did it fall apart?

What device complications were seen?

Performance & Safety of STALIF- A Multi-Center Study

115 Contiguous Patients reviewed from nine (9) U.S. Centers

Minimum of 1 year Follow-up

95% Fusion Rate

0 Pseudoarthroses

No Broken Devices

No Screw Dislodgements

Presented at IMAST ‘07

Advantages of STALIF

Shorter operation time

Less anaesthetic risk

Single procedure

Advantages of STALIF

Reduced blood loss

Posterior muscles preserved

Reduced post-op pain

Quicker recovery

Shorter hospital stay

Improved functional restoration

Long-term Restoration of Function and Reduction of Pain with movement Goal of STALIF

Elimination of pain provocation

Removal of pain generator

Reduction of painful movement

Fusion of motion segment

Restoration of sagittal balance

Minimize morbidity

Preserve muscle function

End Plate Preparation

Encourage a wide exposure

Extensive disc removal and complete end plate preparation.

Large anterior rectangular anulotomy

Clear lateral posterior corners.

Remove posterior osteophytes

Intra-operative trial placement and proper location

Permanent Implant Position

Case 1

56 yo police officer presents for a second opinion.

6-9/10 Low back pain

PMhx: Depression, Asthma

PSx: Appendectomy.

Pexam: Pain with forward flexion past 70 degrees, pain with extension past 30 deg, SLR negative, 5/5 Strength throughout, tender to palpation over posterior lumbar spine/hardware prominent

Post Operative XRays

4 Month Post Op CT

Case 2 : Hybrid Scenario 3 Month Post Op CT

Outcomes Analysis of Hybrid Disc Arthroplasty

AbstractStudy Design. A retrospective observational cohort study of consecutive patients with multiple level lumbar discogenic disease recalcitrant to conservative therapy.

Objective. Assess the efficacy and benefits of hybrid lumbar arthroplasty in the treatment of multiple level disc pathology.

Summary of Background Data. There have been several biomechanical reports describing the single, multiple level and hybrid lumbar disc arthroplasty. However, few have studied the outcomes of hybrid arthroplasty for the surgical treatment of multiple level lumbar discogenic disease.

Introduction

Fusion has long been considered the treatment of choice for severe pain arising from lumbar degenerative disc disease. However, clinical and biomechanical research has demonstrated significant morbidity and long term clinical sequellae associated with spinal fusion constructs. Recently, total disc arthroplasty has emerged as an alternative approach for dynamic stabilization of a painful intervertebral segment. Both the Charite´ and ProDisc artificial disc replacements have been approved by the FDA as another treatment option for single level lumbar discogenic disc disease. They have demonstrated encouraging results throughout the initial short and mid term studies.

However, a considerable subset of patients demonstrate symptomatic multiple level lumbar discogenic disease. The rationale behind arthroplasty in preserving adjacent level segments becomes more important in this group of patients given the larger cantilever forces at play with a potential longer fusion construct. In efforts to preserve motion and limit force concentrations at the remaining lumbar segments hybrid disc arthroplasty is gaining momentum as a new treatment modality for patients with multilevel discogenic disease recalcitrant to conservative therapy.

To our knowledge there are no clinical studies which evaluate the outcomes of patients with hybrid disc arthroplasty. The present study compares a subset of patients treated for multiple level disc pathology through their patient perceived outcomes, return to sport and work.

Methods. A total of 36 discs in 32 patients were reviewed. We performed hybrid disc arthroplasty using either the Charite or Prodisc-L prosthesis in concert with fusion constructs in 32 consecutive patients. Outcome variables included radiographic fusion based on postoperative and follow up films, and clinical assessment using visual analog scale for back pain, the Oswestry disability instruments, return to sport, return to work, , and review of postoperative complications.

Results . 32 patients, 18 males (56.3%) and 14 females (43.8%) were treated with a hybrid construct. Mean patient age was 48.69 years (range 30 to 69) and mean followup was 17.7 months. The mean duration of back pain before surgery was 3.92 years. All patients were available at each follow-up interval except one patient who was lost to followup. Patients showed statistically significant improvement in ODI scores at all follow-up periods compared to baseline ( P < 0.0001). The mean ODI score at baseline was 58.97, which improved to a mean of 38.94 at recent followup. Patients also showed statistically significant improvement in VAS scores at all follow-up periods compared to baseline ( P < 0.0001). The mean VAS score at baseline was 8.56, which improved to a mean of 3.69 at recent followup. Improvement at each interval and overall was statistically significant (p<0.0001) using the Wilcoxon Rank Sum Test. Using the modified Stauffer-Coventry classification the mean outcome was 3.59 (range 2-4, SD 0.682 ). The mean interval from surgery to return to work for the 26 patients in employment was 3.6months or 111.63 days (range 7-351,SD 80.3). The mean interval from surgery to return to sports was 5.2 months or 162.22 days (range 28-507, SD 106.5). Return to sport, activities of daily living and return to work positively correlated to the patients’ perception of their surgical outcome .

Conclusions . Hybrid lumbar arthroplasty appears to be a safe and effective treatment for painful lumbar discogenic disease. The rate of improvement is rapid and sustained through 1.5 years. This study observes outcomes and times to return to work and sport which may serve as a guide for patient education and post-operative expectation.

Dr Pazmiño: Spine Surgeon Dr. Wagmeister: Vascular Surgeon

Dr Lauryssen: Neurolgical Spine Dr Pazmiño: Orthopaedic Spine

Just prior to implantation of a STALIF

Teamwork