Colorado Joint Replacement

Centura Health Physician Group

2535 S Downing St
Ste 100
Denver, Colorado 80210-5847

39.6703825, -104.9742359

Latitude: 39.6703825, Longitude: -104.9742359

Colorado Joint Replacement

Centura Health Physician Group

Colorado Joint Replacement Research

The doctors at Colorado Joint Replacement consider research a cornerstone of their practice. They are involved in both clinical studies with patients to investigate the efficiency and longevity of knee and hip replacements. In addition to clinical research, our team is also working with the engineering departments at both the University of Tennessee and University of Denver to improve both the quality and longevity of total joint replacements.

The research performed by our doctors helps take the guesswork out of designing new medical devices and allows our doctors to find the most effective method of care, which translates into the latest technology and best care for our patients.

  • Current Research

    Current research projects in which Dr. Dennis, Miner, Yang and Jennings are involved: 

    • Clinical Results of Revision Knee Arthroplasty
    • Use of Computer Assisted Navigation in Knee Arthroplasty
    • Long term follow up of RPF implant design
    • Effect of marijuana on patients receiving a total knee replacement
    • Metal Artifact Reduction Sequence (MARS) MRI in Ceramic-on-Ceramic Total Hip Arthroplasty
    • Outcomes following suction drain and non-suction drain assisted total knee arthroplasty
    • 36mm CeramaxTM Ceramic Hip System PMA POST-APPROVAL STUDY:  Short to Mid-Term Follow-up
    • Multi-Center Clinical Evaluation of the ATTUNE® Revision System in Complex Primary Total Knee Arthroplasty
    • Multi-Center Clinical Evaluation of the ATTUNE® Revision System in Revision Total Knee Arthroplasty
    • Revision and Complication profile of the Direct Anterior Approach Total Hip Arthroplasty on a Standard Operating Room Table without the use of a femoral elevator
    • Outcomes of Knee Arthroplasty using a DePuy Knee System
    • Persona® The Personalized Knee System TKA Outcomes Study
    • University of Denver Implant Retrieval Program
    • Manipulation Under Anesthesia (MUA) to Treat Postoperative Stiffness after Total Knee Arthroplasty: A Multicenter Randomized Clinical Trial
    • Computed Tomographic (CT) Evaluation of Femoral and Tibial Component Rotation in a Gap-Balanced Total Knee Arthroplasty
    • Traditional Intravenous Fluid versus Oral Fluid Administration in Primary Total Knee Arthroplasty: A randomized trial
    • The Utility of Next-generation sequencing for the diagnosis of periprosthetic joint infection
    • Does the method of Opening sterile surgical gloves influence Back-Table Contamination Rate?
    • Facilitating a Bladder Scanning Clinical Protocol to Avoid Routine Catheterizations:  A Pilot-study with Knee Athroplasty Patients
    • Colorado Joint Replacement Hip and Knee Data Repository
    • Usefulness of Perioperative Lab Tests in Total Hip and Knee Arthroplasty:  Are they necessary for all Patients?
    • Intraoperative Correlation of Total Joint Implant Fixation with Preoperatively obtained Bone Scan
    • What is the effect of posterior femoral osteophytes on flexion and extension gap tension in total knee arthroplasty?  A cadaveric study.
    • Does the use of intraoperative fluoroscopy improve postoperative radiographic component positioning and size in total hip arthroplasty utilizing a direct anterior approach?
    • Outcomes after total joint arthroplasty in patients using marijuana
    • Movement Pattern Training after Total Knee Arthroplasty (Collaborative effort with the University of Colorado)
    • Improving Rehabilitation Outcomes after Total Hip Arthroplasty (Collaborative effort with the University of Colorado)
    • Edema Management after Total Knee Arthroplasty (Collaborative effort with the University of Colorado)

Completed Research

Our surgeons have completed extensive research in the following areas:

  • Award Winning Research

    Dr. Douglas A. Dennis, one of the premier surgeons at Colorado Joint Replacement, authored a study which evaluated the many factors that can cause patellar crepitus, or grinding around the kneecap, which results when scar tissue develops around the replaced kneecap after total knee replacement. The findings of this research will prove helpful in lessening the incidence of this problem for future total knee replacement recipients. This research received the prestigious John Insall Award for its authors: Dr. Dennis, and co-authors Raymond H. Kim, MD, Derek R. Johnson, MD, Bryan D. Springer, MD, Thomas K. Fehring, MD, and Adrija Sharma, PhD.

    The research, titled Control-Matched Evaluation of Patellar Crepitus after Total Knee Arthroplasty, was peer-reviewed and published in the journal Clinical Orthopaedics and Related Research. Dr. Dennis, along with several of his colleagues, presented the study at the Knee Society Open Meeting. The research was also presented at the American Association of Orthopaedic Surgeons.

    The evaluation compared a group of patients who developed this problem with a group that did not suffer this condition that was matched for age, gender, and body weight. An extensive analysis of patient history and diagnostics showed there were many factors associated with development of patellar crepitus including implant size and design, a history of previous knee surgery, and thickness of the replaced kneecap, among others.

  • Published Research

    Has Self-reported Marijuana Use Changed in Patients Undergoing Total Joint Arthroplasty After the Legalization of Marijuana?

    Marijuana use has become more accessible since its recent legalization in several states. However, its use in a total joint arthroplasty population to our knowledge has not been reported, and the implications of its use in this setting remain unclear.
    Jason M. Jennings MD, DPT, Michael A. Williams MD, Daniel L. Levy BS, Roseann M. Johnson BA,
    Catherine L. Eschen BS, Douglas A. Dennis MD
    Clin Orthop Relat Res (2018) 0:1-6, DOI 10.1097/CORR.0000000000000339 [Epub]

    Revisions of Modular Metal-on-metal THA Have a High Risk of Early Complications

    The risk of early complications is high after monoblock acetabular metal-on-metal (MoM) THA revisions. However, there is a paucity of evidence regarding clinical complications after isolated head-liner exchange of modular MoM THA.
    Jason M. Jennings MD, DPT, Samuel White BS, J. Ryan Martin MD, Charlie C. Yang MD,
    Todd M. Miner MD, Douglas A. Dennis MD
    Clin Orthop Relat Res (2018) 0:1-7DOI 10.1097/CORR.0000000000000363 [Epub]

    Radiographic Changes in Nonoperative Contralateral Knee After Unilateral Total Knee Arthroplasty

    Some patients perceive symptomatic improvement in the contralateral knee after unilateral total knee arthroplasty (TKA).  This so-called “splinting effect” has been observed but has not been radiographically evaluated.
    (https://www.ncbi.nlm.nih.gov/pubmed/29548619)
    Parisi TJ, Levy DL, Dennis DA, Harscher CA, Kim RH, Jennings JM.
    J Arthroplasty. 2018 Jul;33(7S):S116-S120. doi: 10.1016/j.arth.2018.02.018. Epub 2018 Feb 15.

    Revision Total Knee Arthroplasty for Arthrofibrosis

    Arthrofibrosis after TKA is a significant cause of patient dissatisfaction. There is little evidence regarding revision arthroplasty in this patient population. The purpose of this study is to evaluate outcomes after revision TKA for arthrofibrosis.
    (https://www.ncbi.nlm.nih.gov/pubmed/29681492)
    Rutherford RW, Jennings JM, Levy DL, Parisi TJ, Martin JR, Dennis DA
    J Arthroplasty. 2018 Jul;33(7S):S177-S181. doi: 10.1016/j.arth.2018.03.037. Epub 2018 Mar 23.

    Midterm Prospective Comparative Analysis of 2 Hard-on-Hard Bearing Total Hip Arthroplasty Designs

    Hard-on-hard (HoH) bearing surfaces in total hip arthroplasty (THA) are commonly utilized in younger patients and may decrease mechanical wear compared to polyethylene bearing surfaces. To our knowledge, no study has prospectively compared the 2 most common HoH bearings, ceramic-onceramic
    (CoC) and metal-on-metal (MoM) THA.
    (https://www.ncbi.nlm.nih.gov/pubmed/29429884)
    Martin JR, Jennings JM, Watters TS, Levy DL, Miner TM, Dennis DA.
    J Arthroplasty. 2018 Jun;33(6):1820-1825. doi: 10.1016/j.arth.2018.01.019. Epub 2018 Jan 31.

    Fluoroscopy use and radiation exposure in the direct anterior hip approach

    The direct anterior approach to the hip is an increasingly common approach for a total hip replacement. Fluoroscopic guidance can help evaluate bone preparation and component positioning. Traditional landmarks for establishing acetabular component position can be variable and lead to placement of the acetabular component outside Lewinnek’s safe zone. Fluoroscopic imaging has been shown to increase accuracy in acetabular cup position. Fluoroscopic imagining during the direct anterior approach has been shown to be safe and can be viewed as an advantage of the anterior hip approach.
    (http://dx.doi.org/10.21037/aoj.2018.03.13)
     Brian K. Daines1, Charlie C. Yang2
    Annals of Joint 2018; 3:31. doi: 10.21037/aoj.2018.03.13

    Surgical approaches for total hip arthroplasty

    The total hip arthroplasty (THA) has dramatically changed the quality of life patients debilitated by hip arthrosis since its modern inception in the 1950s. THA may be accomplished through a myriad of approaches with the most common being the posterior, direct lateral, and direct anterior approaches (DAAs). The survivorship of THA via these approaches are comparable. A plethora of recent reports demonstrate that each approach has its own unique profile of advantages and disadvantages that surgeons must navigate. This review outlines the three most common approaches for THA including technical pearls, complication profiles, and clinical outcomes.
    (http://dx.doi.org/10.21037/aoj.2018.04.08)
     Marc R. Angerame, Douglas A. Dennis
    Annals of Joint 2018; 3:31. doi: 10.21037/aoj.2018.04.08

    Surgical anatomy of the direct anterior approach for total hip arthroplasty

    With the increasing popularity of the direct anterior approach (DAA) for total hip arthroplasty (THA), it is imperative that surgeons understand the anatomy associated with the approach. Particular anatomic considerations associated with the approach are reviewed here, with particular attention paid to neurological, vascular, muscular, and osseous structures that the surgeon must be familiar with when performing the approach. These are reviewed within the context of a brief outline of the steps of completing the operation.
    (http://dx.doi.org/10.21037/aoj.2018.03.07)
     David C. Holst, Charlie C. Yang
    Annals of Joint 2018; 3:31. doi: 10.21037/aoj.2018.03.07

    Surgical technique of direct anterior approach for total hip arthroplasty on a standard operating room table

    The direct anterior approach (DAA) for total hip arthroplasty (THA) is an increasingly popular surgical approach with numerous benefits cited in the literature. However, it is not without a well-documented “learning curve”, during which time potential difficulties can occur. This article outlines the authors’ technique of performing the DAA on a standard operating room table, with particular attention paid to technical specifics that may be helpful to the surgeon in performing this operation safely.
    (http://dx.doi.org/10.21037/aoj.2018.04.01)
     David C. Holst, Marc R. Angerame, Charlie C. Yang
    Annals of Joint 2018; 3:31. doi: 10.21037/aoj.2018.04.01

    Advances in instrumentation and enhancing technology for direct anterior hip replacement surgery

    This review discusses the numerous advances in technology and instrumentation that have contributed to the success and popularity of the direct anterior hip replacement. Topics covered include: pharmaceuticals, anesthesia, surgical energy, fluoroscopy, navigation, instrumentation, and operating room equipment. These technologies are discussed and presented with supporting science as well as the authors’ preferred methods of implementing this technology an instrumentation into practice.
    (http://dx.doi.org/10.21037/aoj.2018.04.06)
    J.N. Duke, Charlie C. Yang
    Annals of Joint 2018; 3:31. doi: 10.21037/aoj.2018.04.06

    Direct anterior total hip arthroplasty: solicitation and industry

    The following manuscript reviews the recent and continued increased interest in the direct anterior total hip arthroplasty approach. Two important drivers for the popularization of this approach were identified: industry and solicitation. We discuss the potential roles in which industry has been able to market this approach and what impact this had on patient and surgeon demand. The direct anterior approach is now the second most commonly performed approach and continues to increase in popularity amongst both patients and surgeons.
    (http://dx.doi.org/10.21037/aoj.2018.05.07)
    J. Ryan Martin, Oliver B. Nikolaus, Bryan D. Springer
    Annals of Joint 2018; 3:31. doi: 10.21037/aoj.2018.05.07

    Pearls: Early Removal of Posterior Osteophytes in TKA

    Posterior-compartment osteophytes are commonly encountered during TKA.  They can limit of prevent terminal extension by tenting the posterior capsule and can cause coronal plane imbalance due to tenting of adjacent capsule-ligamentous structures.  Osteophyte removal is a principle of TKA soft tissue balancing
    (https://www.ncbi.nlm.nih.gov/pubmed/29419635)
    Holst DC, Dennis DA.
    Clin Orthop Relat Res. 2018 Apr;476(4):684-686. doi: 10.1007/s11999.0000000000000015.

    Fracture of the insert cone of a polyethylene liner in a failed posterior-stabilized, rotating-platform total knee arthroplasty

    Failures unique to posterior cruciate-substituting total knee prostheses rarely include polyethylene post fractures but have been described. We report a case involving a fracture of the distal insert cone of a rotating-platform (RP) polyethylene liner in a primary total kneearthroplasty. This case highlights a 67-year-old male presenting with new-onset knee pain and recurrent effusions with osteolysis 11 years following placement of a posterior-stabilized, RP total knee arthroplasty. At the time of revision surgery, the polyethylene insert cone was found to be fractured just below the junction between cone and the body of the insert. Liner exchange, synovectomy, and osteolytic-defect curettage and cement packing were performed. One year following revision surgery, the patient is without pain and has returned to function without limitations. Clinicians must be aware of this possible failure with RP prostheses in the setting of pain with a stable knee, recurrent aseptic effusions, and osteolysis.
    (https://www.ncbi.nlm.nih.gov/pubmed/29896543)
    Angerame MR, Jennings JM, Dennis DA
    Arthroplast Today. 2017 Nov 7;4(2):148-152. doi: 10.1016/j.artd.2017.10.002. eCollection 2018 Jun.

    Total Knee Arthroplasty After Anterior Cruciate Ligament Reconstruction

    Despite the success of restoring joint stability and improving early functional outcomes after anterior cruciate ligament (ACL) reconstruction, the long-term risk of developing symptomatic osteoarthritis requiring total knee arthroplasty is higher than that in the uninjured population. The purpose of this study was to compare operative characteristics and early outcomes of patients undergoing total knee arthroplasty after ACL reconstruction with those of a matched cohort of control subjects with primary osteoarthritis and no history of ligament reconstruction.
    (https://www.ncbi.nlm.nih.gov/pubmed/28145948)
    Watters TS1, Zhen Y, Martin JR, Levy DL, Jennings JM, Dennis DA.
    J Bone Joint Surg Am. 2017 Feb 1;99(3):185-189. doi: 10.2106/JBJS.16.00524.

    Muscle sparing anterior approach to the hip

    The anterior approach to the hip is a muscle-sparing approach where no muscles are cut. Muscle splitting approaches, such as the direct lateral approach, anterolateral approach, or the posterior approaches require the cutting and detachment of soft tissues. The anterior approach, on the other hand, utilizes the interval between the rectus femoris muscle and tensor fasciae latae to access the hip joint. Potential benefits of the anterior approach include reduced soft tissue trauma, improved early outcomes and speed of recovery, comparable component position, and decreased dislocation rate.
    (http://dx.doi.org/10.21037/aoj.2017.04.03)
     Brian K. Daines, Charlie C. Yang
    Annals of Joint: 2017, doi: 10.21037/aoj.2017.04.03    

    Magnitude of Deformity Correction May Influence Recovery of Quadriceps Strength After Total Knee Arthroplasty

    Malalignment of the lower extremity is commonly seen in patients with severe osteoarthritis undergoing total knee arthroplasty (TKA) and is believed to play a role in quadriceps strength loss. Deformity correction is typically achieved through surgical techniques to provide appropriate ligamentous balancing. Therefore, this study examined the influence of change in lower extremity alignment on quadriceps strength outcomes after TKA.
    (https://www.ncbi.nlm.nih.gov/pubmed/28559195)
    Loyd BJ, Jennings JM, Falvey JR, Kim RH, Dennis DA, Stevens-Lapsley JE
    J Arthroplasty. 2017 Sep;32(9):2730-2737. doi: 10.1016/j.arth.2017.04.030. Epub 2017 Apr 27.

    Enhancing Recovery After Total Knee Arthroplasty

    There have been multiple successful efforts to improve and shorten the recovery period after elective total joint arthroplasty. The development of rapid recovery protocols through a multidisciplinary approach has occurred in recent years to improve patient satisfaction as well as outcomes. Bundled care payment programs and the practice of outpatient total joint arthroplasty have provided additional pressure and incentives for surgeons to provide high-quality care with low cost and complications. In this review, the evidence for modern practices are reviewed regarding patient selection and education, anesthetic techniques, perioperative pain management, intraoperative factors, blood management, and postoperative rehabilitation.
    (https://www.ncbi.nlm.nih.gov/pubmed/28870300)
    Rutherford RW, Jennings JM, Dennis DA.
    Orthop Clin North Am. 2017 Oct;48(4):391-400. doi: 10.1016/j.ocl.2017.05.002. Epub 2017 Aug 8.

    Medial Tibial Reduction Osteotomy is Associated with Excellent Outcomes and Improved Coronal Alignment

    The medial tibial reduction osteotomy (MTRO) was introduced to achieve coronal ligamentous balance in total knee arthroplasty (TKA) patients with substantial preoperative varus deformity. Limited data exists on the outcomes of patients requiring an MTRO. This study compares outcomes of a matched cohort of patients that either required or did not require an MTRO during TKA.
    Martin R , Levy D, Miner T, Conrad D, Jennings J, Dennis D
    Reconstructive Review

    Book Chapters:

    • Thomas J Parisi and Douglas A. Dennis. “Management of Severe Tibial Bone Loss: Tibial Bone Graft”. In: A.J. Tria, G.R. Scuderi, F.D. Cushner (Eds.): Complex Cases in Total Knee Arthroplasty. Cham, Switzerland, 2018: p. 246-254.
    • Richard W. Rutherford and Douglas A. Dennis. “Femoral Bone Grafting for Severe Femoral Bone Loss”. In: A.J. Tria, G.R. Scuderi, F.D. Cushner (Eds.): Complex Cases in Total Knee Arthroplasty. Cham, Switzerland, 2018: p. 269-277.
    • Richard W. Rutherford, Jason M. Jennings, Douglas A. Dennis. “Enhancing Recovery After Total Knee Arthroplasty”. In FM Azar (Eds.): Orthopedic Clinics of North America: Perioperative Pain Management, Volume 48(4). Philadelphia Pennsylvania, October 2017: p. 391-400
    • C.J. Della Valle, D.J. Berry, C.R. Bragdon, J.J. Callaghan, R. D’Apolito, D.A. Dennis, I. De Martino, R.H. Emerson, A.A. Freiberg, Y.-M. Kwon, K.W. Lacy, S.J. MacDonald, R.M. Meneghini, M. c. Morrey, B.F. Morrey, A.S. Ranawat, H.E. Rubash, T.P. Sculco. “Primary Total Hip Arthroplasty”. In: M. a. Mont, M. Tanzer (Eds.): Orthopedic Knowledge Update. Hip Knee Reconstruction, 5th ed. American Academy of Orthopaedic Surgeons. Rosemont, IL, 2017: pp. 377–391

Collaborative Research

Our surgeons have the privilege of working with the University of Colorado School of Medicine, University of Denver and University of Tennessee School of Biomedical Engineering and Biomechanics on research dedicated to improving patient outcomes after joint replacement surgery.

  • Functional Performance Research

    Collaborative-care Intervention to Promote Physical Activity after Total Arthroplasty

    The goal of this study is to increase physical activity and overall health following a total knee replacement. We are studying whether an intervention using physical activity monitors and monthly face to face meetings will increase PA and health. 

    Determination of Pain Phenotypesin Older Adults with Knee Osteoarthritis

    The purpose of this study is to learn more about painful knee osteoarthritis.  The evidence suggests that, even though people with knee osteoarthritis all have the same diagnosis, different people probably have pain for different reasons.  However, right now, we don’t know how best to discriminate one “type” of pain from another “type” of pain.  This study is designed to begin answer that question.  We will measure a number of different things—all are thought to be important in painful knee OA—so that we can hopefully identify different types of painful knee OA.

    Progressive Rehabilitation for Total knee Arthroplasty

    This study compares two approaches for rehabilitation after unilateral TKA (progressive vs traditional). Rehabilitation begins immediately after hospital discharge and continues for 12 weeks. In addition to physical therapy, patients come in for 6 testing sessions to assess muscle strength, knee ROM, pain, muscle size (pQCT) and function (e.g. walking and stairs).

    Strength and Function Following Total Hip Arthroplasty

    This study compares feasibility of a comprehensive, multicomponent (CMC) intervention with a control rehabilitation intervention after THA. The CMC intervention involves strength, neuromuscular control and functional training to improve muscle coordination around the hip and pelvis to enhance functional performance (2 times/week for 8 weeks).

    Outcomes Following Tourniquet and Non-Tourniquet Assisted Total Knee Arthroplasty

    This study aims to determine the effects of a tourniquet on muscle strength and physical function after a total knee replacement. A tourniquet is a device used to slow blood flow to the leg. Surgeons typically use a tourniquet in order to control blood loss during surgery and to improve their ability to see the knee joint as they operate, but it’s unknown if a tourniquet can cause some muscle damage. We follow progress from before surgery to 3 months after surgery.

  • Orthopedic Biomechanics

    Control-matched computationalevaluation of tendo-femoral contact in patients with PS TKA

    Hoops, H.E., Johnson, D., Kim, R., Dennis, D.A., Baldwin, M.A.*, Fitzpatrick, C.K., Laz, P.J., Rullkoetter, P., 2012.
    Journal of Orthopaedic Research, Vol. 30, 1355-1361.

    Painful patellar crepitus is a potential complication in up to 14% of patients following posterior-stabilized (PS) total knee arthroplasty (TKA). A recent clinical study identified influential patient and surgical variables by comparing a group of crepitus patients with controls matched for age, sex, and body mass index. The purpose of our study was to evaluate effects of variables identified as significant in the clinical study, including patellar ligament length, femoral component flexion, patellar button size, and position of the joint line, on contact between the quadriceps tendon and the PS femoral component. A previously verified finite element model was utilized to estimate tendo-femoral contact during deep flexion activity. Using discrete perturbations, the computational model confirmed the clinical findings in that an increased patellar ligament length, flexed femoral component, lowered joint line, and larger patellar component all reduced potentially deleterious contact near the intercondylar notch. With the selected level of anatomic and component alignment perturbations, the most influential factor affecting tendo-femoral contact was patellar ligament length. Three crepitus patients with matched controls were subsequently modeled, and contact with the anterior border of the notch was present in each crepitus patient, but none of the controls. Alternative surgical alignments for these patients were evaluated to improve the potential long-term outcomes. By characterizing conditions that may lead to painful crepitus, the modeling approach supports clinicians by identifying pre-surgical indicators and important alignment parameters to control intraoperatively. Learn More

    Patellar component design influences size selection and coverage

    C.C. Yang, D.A. Dennis, P.G. Davenport, R.H. Kim, T.M. Miner, D.R. Johnson, P.J. Laz
    The Knee, 2016 Dec 1. [Epub ahead of print]

    Patellofemoral (PF) complications following total knee arthroplasty continue to occur. Outcomes are influenced by implant design, size and alignment in addition to patient factors. The objective of this study was to assess the effect of implant design, specifically round versus oval dome patellar components, on size selected and bony coverage in a population of 100 patients. Intraoperative assessments of patella component size were performed using surgical guides for round and oval designs. Digital images of the resected patellae with and without guides were calibrated and analyzed to measure bony coverage. Lastly, the medial-lateral location of the median ridge was assessed in the native patella and compared to the positioning of the apex of the patellar implants. In 82% of subjects, a larger oval implant was selected compared to a round. Modest, but statistically significant, differences were observed in selected component coverage of the resected patella: 82.7% for oval versus 80.9% for round. Further, positioning of the apex of oval patellar components reproduced the median ridge of the native patella more consistently than for round components. These findings characterized how implant design influenced size selection and coverage in a population of patients. The ability to "upsize" with oval dome components led to increases in bony coverage and better replication of the median ridge compared to round components. Quantifying the interactions between implant design, sizing and coverage for a current implant system in a population of patients supports surgical decision-making and informs the design of future implants.

    Experimental Biomechanics Laboratory

    The Experimental Biomechanics Laboratory performs a wide variety of testing to evaluate the biomechanics of the body, the performance of implants and the mechanical properties of tissue and materials. The signature piece of equipment in the lab is an AMTI VIVO, which is the first six degree-of-freedom joint simulator. The VIVO is used in conjunction with high accuracy imaging systems: Optetrack infrared marker tracking for measurement of relative motion and a digital imaging correlation system to measure strain fields on tissue and devices. Further the lab has servo-hydraulic testing equipment to perform traditional single and bi-axial materials characterization. The lab is well equipped to perform a variety of evaluations ranging from ASTM standard tests on implants to measurement of joint mechanics in cadavers under realistic loading conditions.

    The Effect of Posterior Osteophytes on Flexion and Extension Gaps in Total Knee Arthroplasty

    David Holst, Gary Doan, Marc Angerame, Chadd Clary, Douglas Dennis

    Large osteophytes within the posterior compartment of the arthritic knee pose intraoperative challenges for matching flexion and extension gaps to avoid instability during total knee arthroplasty (TKA). The purpose of this study was to evaluate the effect of posterior osteophytes on medial and lateral contact forces through the flexion range during TKA. Five cadaveric lower limbs were acquired for testing. Ellipsoidal synthetic osteophytes were fashioned to replicate the morphology of clinically-observed osteophytes and positioned on the superior aspect of the posterior medial condyle. Osteophytes were created with 10-mm and 15-mm S-I radii and secured via a mounting flange extending into the intercondylar notch. Osteophytes were 3D printed using a Fortus 450 printer. Posterior stabilized TKA was performed on the specimens via a medial parapatellar approach using a gap-balancing technique. After primary bony resections, articulating trials were affixed to tibia and femur and the Orthosensor® tibial spacer was inserted into the specimen to measure medial and lateral contact forces at the knee. Contact measurements were taken at full extension, 10°, 30°, 45°, 60°, and 90° knee flexion while the tibia was supported in neutral I-E and Ad-Ab rotations. As expected, osteophytes on the medial condyle approximately doubled the medial contact loads near full extension, but also influenced the contact loads in mid- and deep-flexion. The increased medial loads were coupled with an unloading of the lateral condyle, indicating that osteophytes induced an asymmetric reduction in the extension space. These results demonstrate care should be taken when employing the balanced gap technique on knees with significant posterior osteophytes. Posterior osteophytes should be removed prior to establishing the extension space, potentially via a conservative preliminary distal femoral resection to enable osteophyte removal. This research enables improved surgical technique for patients with significant posterior osteophytes, potentially improving stability and outcomes after TKA.

  • Biomedical Engineering and Biomechanics

    In Vivo Mechanics Analysis of Patients Having Either a Sigma PS Fixed or Mobile Bearing TKA

    The goal of this study was to determine knee kinematics for the Sigma Fixed Bearing Posterior Stabilized TKA and the Sigma Mobile Bearing Posterior Stabilized TKA using fluorscopy.  Range-of-motion, axial rotation, and anterior/posterior contact was analyzed.  For the mobile bearing group, axial rotation of the bearing was also assessed.  In addition to the motion analysis, contact forces, contact stresses and vibration/sound were also analyzed. 

    Implantation and Comparison of Kinematics for Subjects Implanted with a Press Fit Condylar Sigma Rotation Platform Total Condylar III or Fixed-Bearing Total Condylar III Prosthesis

    The aim of this study was to compare knee kinematics between the Sigma TC3 Rotating Platform TKA and the Sigma TC3 Fixed Bearing TKA using fluoroscopy.  Range-of-motion, axial rotation, and anterior/posterior contact was analyzed.  For the rotating platform group, axial rotation of the bearing was also assessed. Electromyography (EMG) data was also collected in addition to the fluoroscopic data.  This data allowed us to correlate muscle activity to kinematic patterns.