Cortical And Standard Trajectory Pedicle Screw Fixation Techniques In Stabilizing Multisegment Lumbar Spine With Low Grade Spondylolisthesis

Wayne K. Cheng, MD, Serkan İnceoğlu, PhD
Background: The cortical screw fixation has been recently proposed as an alternative to the standard pedicle screw fixation technique. Biomechanical studies involving individual screw pullout and single level motion segment stabilization showed comparable performance of both techniques. However, whether this new fixation technique can be applied to the stabilization of multilevel lumbar segments with significant destabilization has been unclear.

Purpose:  To compare stability of cortical screw (CS) fixation to the traditional pedicle screw (PS) fixation in an unstable 3 level spondylolisthesis model.


Fatigue Performance of Cortical Bone Trajectory Screw Compared to Standard Trajectory Pedicle Screw

Yusuf Tahiri Akpolat, MD, Serkan İnceoğlu, PhD, Nolan Kinne, Devon Hunt, Wayne K. Cheng, MD

Central And Juxta-Endplate Placement of an ALIF Plate: Comparison of Pullout Strength

Wojtek Dajnowicz, Andrew Yang, Wayne K. Cheng, MD, Serkan İnceoğlu, PhD
Object: Although anterior lumbar interbody fusion (ALIF) is becoming popular, some details on the placement technique for optimal biomechanical performance of the ALIF plate are not known. Vertebral screw fixation stability might differ depending on the insertion point and depth due to the non-homogeneous structural characteristics of the vertebral bone. In this study we investigated (1) whether the plate screws should be inserted into the central vertebra or juxta-endplate and (2) whether bony ridge at the perimeter of the endplate should be removed before the plate insertion because it interferes with the seating of the plate.


A Comparison of Staphylococcus aureus Biofilm Formation on Cobalt-chromium and Titanium Spinal Implants

Shalin Patel, MD, Wilson Aruni, PhD, Serkan Inceoglu, PhD, Wayne Cheng, MD, Olumide Danisa, MD
Background: Infection after the implantation of spinal hardware is a costly problem that is associated with significant morbidity.  The formation for antibiotic resistant biofilm on implanted hardware provides a significant challenge with regard to the eradication of deep spinal infections. The intrinsic characteristics of implant materials play a contributory role in the development of biofilm formation.

Purpose: To compare the difference in the propensity for biofilm formation between Titanium alloy (Ti) and Cobalt Chrome (CoCr) spinal implants.

Preventing Instrumentation Failure in Pedicle Subtraction Osteotomy: Biomechanical Analysis of Rod Configuration

Zachary S. Jager, MD, Serkan Inceoglu, PhD, Daniel Palmer, BS, Ashley Voss, BS, Wayne K. Cheng, MD
Introduction: Pedicle subtraction osteotomy (PSO) is a surgical correction option for sagittal imbalance. Posterior fixation for the PSO involves pedicle screw and rod based instrumentation, with the rods being contoured to accommodate the accentuated lordosis. Pseudarthrosis and instrumentation failure are known complications of PSO. However, the long-term fatigue strength and role of additional rods on rod fracture prevention are still unknown.


Adaptive Remodeling At The Pedicle Due To Pars Fracture: A Finite Element Analysis Study

Serkan İnceoğlu, PhD, Prasath Mageswaran, MSc, Michael T. Modic, MD, Edward C. Benzel, MD
Object: Spondylolysis (SP) is a common condition among the general population and major cause of back pain in young athletes. SP can be difficult to detect with plain radiography and has been reported to lead to contralateral pars fracture or pedicle fracture in the terminal stages. Interestingly, some patients with late-stage SP are observed to have X-ray or CT evidence of a sclerotic pedicle on the contralateral side to the SP. Although computational studies have shown stress elevation in the contralateral pedicle after a pars fracture, it is not known if these changes would cause sclerotic changes in the contralateral pedicle.  The objective of this study was to investigate the adaptive remodeling process at the pedicle due to a contralateral spondylolysis using finite element analysis.


Simulating Spiral Fractures In Long Bone: A Sheep Femur Model

Corey Burke, Wojtek Dajnowicz, Scott Epperly, Hrayr Basmajian, MD, Serkan İnceoğlu, PhD; Gary Botimer, MD

Introduction: Spiral fracture is a common type of femoral shaft fracture. It is usually seen in accidents exposing the femur to high-energy torsional loading such as skiing. Biomechanical studies on femoral spiral fracture fixation are surprisingly limited despite its high prevalence. In these studies, the proposed fracture model was obtained by either carefully sawing a synthetic bone substitute1 or applying a high torque at a high rate using a custom-made torque device2. Hence, there is still a need for a methodology for a reproducible and inexpensive model. This study explains how low energy spiral fractures can be obtained in sheep model.


Femoral Spiral Fracture Fixation With Cerclage Wire And Plating Method: Biomechanical Comparison of Fatigue Performance

Corey Burke, Wojtek Dajnowicz, Scott Epperly, Hrayr Basmajian, MD, Serkan İnceoğlu, PhD; Gary Botimer, MD

Iatrogenic Soft Tissue Damage During Total Knee Arthroplasty: Comparison of Different Oscillating Saw Blade Designs

Yong Hwan Kwon, Ryan Kim, Ryan Eggers, Paul Williams, MS, Serkan İnceoğlu, PhD, Gary Botimer, MD

Iatrogenic intra-operative damage to medial collateral ligament during total knee arthroplasty is an uncommon, yet devastating, complication that threatens the success of the surgery. While the cutting tip of the blade is intuitively deemed to be hazardous to the soft tissue, the contribution of the side of the blade to the soft tissue damage has been ignored. We believe that changes in the design of the blades can reduce the risk of tissue damage. The hypotheses of this study were (1) some blade tip designs have less risk of tissue damage, and (2) changes in the design of the side of the blade will reduce the risk of tissue damage.

Infection resistant bio-nanopatterned surfaces for orthopedic implants

Serkan Inceoglu, PhD, Wilson Aruni, PhD, Gary Botimer, MD
Joint replacements and other orthopedic prosthetic surgeries are performed with a total estimated cost of 3 billion dollars annually in the USA and the overall incidence of implant related infections increase leading to many complication and health related cost. Multidrug resistant biofilm forming bacteria pose a great threat to the success of the implants due to their persistent infections. The success of an orthopedic implant depends on its infection resistance property, and also its nature to support cell attachment, growth and osseointegration. Various strategies, have been resorted to focus on addressing such issues, however, they have not proven to be long lasting and are with modest clinical success. Recent paradigm shift from fabrication techniques to nanoscience-enabled techniques have significantly enhanced the ability to design and develop better prosthetics. Nanoengineered surfaces possess anti-biofilm property and unique capacity to facilitate molecular and cellular events leading to improved biological response. Since there is increasing evidence that nanoscale surface properties can prevent bacterial adhesion, stimulate and modulate various molecular and biological processes at the implant - tissue interface, we propose to study the modifications on the surface of the orthopedic implants using various patterns at nanoscale level. Such modifications on PDMS matrix will be used to test our central hypothesis that nanopatterned / bio-nanopatterned surface modification of implant can inhibit biofilm formation thus prevent endogenous infections and also promote osteoblastic and osteoclastic activities.

Novel orthopedic cements for the controlled delivery of antibiotics in the treatment of prosthetic infection in total joint arthroplasty

Vicky Maskiewicz, PhD, Serkan Inceoglu, PhD, Gary Botimer, MD
Infection following total joint arthroplasty is a major complication. National statistics report that 1-2% of all joint arthroplasty procedures fail through infection every year.  CDC statistics for 2006 reported a total of 22,847 infected knee and hip replacements, with an average financial burden of over $80,000 per case. With the emergence of more resistant strains of bacteria, this cost has been escalating significantly in the past 5 years.  A two-stage exchange revision is the gold standard for therapy in these cases, involving the removal of infected components, the implantation of a temporary antibiotic-laden polymethylmethacrylate (PMMA) cement spacer, and a minimum 6-week course of intravenous antibiotic therapy to resolve the infection prior to a second surgery (involving the removal of the spacer and the insertion of a revision prosthetic joint). The purpose of the PMMA cement spacer, which is custom crafted at the time of surgery, is to provide proper soft-tissue and limb length between stages and ostensibly act as a source of local delivery of antibiotics.  Unfortunately, in order to avoid compromising the mechanical properties of the cement spacer, antibiotics are incorporated at very low (%w/w) levels, thereby often not reaching the cytotoxic levels required to clear the infection. Although the strength of the spacer used in two stage revisions is less of a concern than the antibiotic delivery, the resultant antibiotic released is only small fraction of its incorporated payload, due to the majority of the antibiotic being incorporated deep in the cement construct, resulting in a large burst of drug, followed by release of significantly lower levels of antibiotic.  The ideal antibiotic-loaded bone cement for management of these infections should release continuously high antibiotic concentrations over a prolonged period of time, in order to guarantee infection sanitation and avoid the emergence of new resistant bacterial strains.   The long term goal of this project is to develop a novel and innovative delivery system that will release antibiotics into the bone and/or joint spaces at therapeutic levels over a period of days to weeks, with complete elution of payload for two stage revisions and adequate amounts of antibiotics with near normal strength of the cement for single stage revisions. 

Biomechanical Comparison of Krackow Locking Stitch versus Nonlocking Loop Stitch with Varying Number of Throws

Joseph Hahn, MD, Serkan İnceoğlu, PhD, Montri Wongworawat, MD
Background: Common suture configuration techniques used for ligament and tendon grafts and repair are the Krackow locking stitch and nonlocking loop stitch such as a whipstitch. Clinically, the preferences of orthopaedic surgeons vary.
Hypothesis/Purpose: The Krackow locking stitch and the nonlocking whipstitch, with varying suture loops, produce different biomechanical and physical effects on the tendon end.

Biomechanical Comparison of Bicortical Screws Versus Lag Screws in Metacarpal Fixation

Priya Lewis, BA, Benjamin Gerke, BS, Zachary Filip, MD, Serkan Inceoglu, PhD, Jane Dhillon, MD, Mark Martin, MD, DMD
Background:  The lag screw technique has become the standard for open fixation of oblique, spiral and condylar hand fractures. Compression is achieved by over-drilling the near cortex so the screw head will pull the near and distal fragments together. The potential for iatrogenic comminution is increased. Bicortical fixation achieves compression with bone clamps prior to fixation.
The purpose of this study was to biomechanically compare two types of fixation with cyclic loading to more accurately describe physiologic stress to the metacarpals.