The biomechanical goals of lumbar interbody fusion are to restore alignment, restore intervertebral and foraminal height, and promote fusion by providing immediate stability (ability to limit segmental motions under physiologic load). Interbody cages can aid in achieving these goals, especially bone graft resorption/disc height loss. Biomechanical and clinical data suggest that PLIF stand-alone cages may not provide adequate stability and supplemental stabilization may be needed for a more predictable biomechanical environment conducive to fusion. However,besides the PLIF approach to place cages, a number of other approaches (e.g., far lateral - LIF,transforaminal - TLIF and anterior – ALIF) are used.  The hypothesis for the present study is that some of these approaches preserve the structures that impart stability to the segment and thus stand-alone cage placed using those approaches may provide sufficient stability without additional posterior instrumentation (360 constructs). Additionally, the size, footprint, and end plate support for the cages differ and may play a role in the surgical success. Such a comprehensive study is somewhat lacking in the literature.  The outcome may enable industry with the design and development of an appropriate cage which will be very effective the imparting the stability to the decompressed segment.

Principal Investigator: Vijay Goel, PhD

Co-Principal Investigator: Anand Agarwal, MD

Trainee: Sushil Sudershan

Sagittal balance is an important clinical parameter significantly associated with high health-related quality of life scores. Loss of global balance occurs during aging as lordotic lumbar segments become neutral or kyphotic through the degenerative cascade. Realignment of the spine through osteotomies, interbody cages and posterior spinal fusion can be extremely effective at restoring global sagittal balance. Realignment procedures are being performed more frequently and despite their effectiveness these procedures are expensive and revision rates remain high. Loss of alignment through reciprocal kyphosis and weak hip extensors contribute to failures of these procedures. Assessment of global and segmental range of motion of the thoracic-lumbar-hip axes is critical to the success of spinal realignment procedures. Although static angular normal parameters have been well established there is limited data on how these parameters perform in the dynamic setting in the older patient. Furthermore data on soft tissue balancing of the spine is limited because range of motion parameters are not routinely measured objectively through Xray, CT or MRI. Laboratory based motion analysis techniques (eg. Vicon motion analysis system) have become the gold standard to quantify spine motion. Recently, a low-cost system that uses depth cameras to measure three-dimensional motion (Microsoft Kinect) has emerged as a potential alternative to the gold standard laboratory based motion analysis systems that can be used in a clinical setting.

Principal Investigator: Shane Burch, MD 

Co-Principal Investigator: Jeffrey Lotz, PhD 

Trainee: Daniel Beckerman 

Today’s orthopaedic devices can be subjected to variations of worst-case configurations under different use conditions, especially as more patients are receiving particular implant types (i.e.,total hip, spinal cage) at younger, more active ages. Presently, the FDA regulatory review (i.e.,510k) process relies on evaluation of worst-case scenarios to evaluate device safety, but many new device types have few established standards, thus requiring sponsors to design tests that they think best represent physiologic use. Even with standards in place, devices may need to be tested in larger configuration envelopes because the standards may not fully represent be true worst-case scenarios.

Principal Investigator: Edward Nyman, Jr. PhD 

Co-Principal Investigators: Anil Gupta, MD; Vijay K. Goel, PhD 

Trainee: Rodney Summers 

While the lumbar spine is the most significant source of low back pain, the SI joint has been recognized as a pain generator in 14.5% to 22.55% of patients. SI joint fusion may be required if non-operative treatments (e.g. anti-inflammatory medications, physical therapy, steroid injections) fail. Surgical treatment of the SI joint can be performed using either open or minimally invasive surgical (MIS) techniques. Recent studies comparing the two fusion techniques found the MIS procedure resulted in largerimprovements in ODI and pain relief, as well as shorter surgical times and hospital stays. Although SI joint fusion is effective, the potential for adjacent segment disease is unknown. The purpose of this study is to quantify the changes at the adjacent lumbar motion segmentsafter SI joint fusion and compare them to the changes reported for lumbar arthrodesis procedures that have increased risk for ASD.

PrincipaI Invesitigator: Vijay K. Goel, PhD

Proximal Junctional Kyphosis (PJK) and Proximal Junctional Failures (PJF) are complications observed in long posterior thoracolumbar spinal fusions. The vertebral compression fractures (VCF) at the adjacent proximal junction are correlated to PJK. Prophylactic vertebroplasty for the treatment of VCF reduces the rate of immediate adjacent segment fractures but it shifts the level of failure one level up. To mitigate upper level fractures, we hypothesize that a vertebroplasty technique involving tapered reduction of cement volume in the proximal vertebrae adjacent to the fused segment may translate into a decreased rate of PJK.

Principal Investigator: Vijay K. Goel, PhD

Current instrumentation standards for correction of scoliosis and other thoracic spinal deformities include the use of thoracic pedicle screws. The anatomy of the pedicles including their diameter, length, and trajectories in the normal spine as well as the scoliotic spine have been studied and have served as the basis for pedicle screw insertion techniques. A number of techniques to facilitate accurate placement of pedicle screws have been utilized including free-hand technique (FH), funnel technique, the in-out-in technique, fluoroscopically-assisted screw placement, laminoforaminal pedicle palpation, and various other forms of intraoperative navigation techniques including robotics. Each technique has its proponents with the goal of accurate screw placement, efficient placement, and minimization of neurological deficits and re-operation for errant screw placement. Re-operations for errant screw placement have been noted in the early post-operative period in AIS surgery. Breaches of the pedicle in the placement of thoracic pedicle screws have been reported to range from 2to 15.7%. The accuracy of placement has been shown to depend upon the level of the surgeon’sand assistant’s experience. 

Principal Investigators: Baron Lonner, MD and Vijay K. Goel, PhD 

In the bilateral fusion approach, the lag screws are inserted across the two adjacent vertebrae, thus passing through the IVD. Lag screws passing through the intervertebral disc will compress the two vertebral bodies, and thus provides stabilization with and without the interbody cage. The new screw concept and surgical approach might be a good alternative to traditional posterior transpedicular stabilization.

Principal Investigators: Cengiz Gomleksiz, MD and Deniz U.Erbulut, PhD