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.
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.
Here is a current list of research projects in which Dr. Dennis, Miner, Yang and Jennings are involved:
- Population-based Evaluation of Knee Mechanics Considering Inter-subject and Surgical Alignment Variability
(Collaborative effort with the University of Denver which has received a National Science Foundation (NSF)grant)
- Kinematics of Hip and Knee Arthroplasty
- In Vivo Force Determination in Hip and Knee Arthroplasty
- Factors Affecting Flexion After Knee Arthroplasty
- Clinical Results of Revision Knee Arthroplasty
- Use of Computer Assisted Navigation in Knee Arthroplasty
- Gap Balancing Vs. Measured Resection Techniques For Total Knee Arthroplasty
- Evaluation of Patellofemoral Crepitus After Total Knee Arthroplasty
- In vivo comparison of total knee implant designs
- Use of leukocyte esterase to rule out joint infection, determination of false positive
- Long term follow up of RPF implant design
- Effect of marijuana on patients receiving a total knee replacement
- Evaluation of radiation exposure with Direct Anterior Replacement
- Evaluation of Poly-on-Ceramic Hip implants with MARS MRI
Recently Completed Research
New total knee arthroplasty designs: do young patients notice?
Although the volume of total knee arthroplasties (TKAs) performed in the United States continues to increase, recent reports have shown the percentage of patients who remain "unsatisfied" is as high as 15% to 30%. Recently, several newer implant designs have been developed to potentially improve patient outcomes. (http://www.ncbi.nlm.nih.gov/pubmed/24903823)
Nunley RM1, Nam D, Berend KR, Lombardi AV, Dennis DA, Della Valle CJ, Barrack RL. Clin Orthop Relat Res.2015 Jan;473(1):101-8. doi: 10.1007/s11999-014-3713-8.
Muscle strength and functional recovery during the first year after THA.
Patients undergoing total hip arthroplasty (THA) often are satisfied with the decrease in pain and improvement in function they achieve after surgery. Even so, strength and functional performance deficits persist after recovery, but these remain poorly characterized; knowledge about any ongoing strength or functional deficits may allow therapists to design rehabilitation programs to optimize recovery after THA. (http://www.ncbi.nlm.nih.gov/pubmed/23817756)
Judd DL1, Dennis DA, Thomas AC, Wolfe P, Dayton MR, Stevens-Lapsley JE. Clin Orthop Relat Res. 2014 Feb;472(2):654-64. doi: 10.1007/s11999-013-3136-y.
Evaluation of total knee arthroplasty performed with and without computer navigation: a bilateral total knee arthroplasty study.
Sequential bilateral total knee arthroplasty performed on 54 patients utilizing navigation (CAS-TKA) in one knee and traditional instrumentation (T-TKA) in the contralateral knee was reviewed at a mean follow-up duration of 2.5years. (http://www.ncbi.nlm.nih.gov/pubmed/23164836)
Johnson DR1, Dennis DA, Kindsfater KA, Kim RH. J Arthroplasty. 2013 Mar;28(3):455-8. doi: 10.1016/j.arth.2012.06.026. Epub 2012 Nov 17.
Is socioeconomic status a risk factor for stiffness after total knee arthroplasty? A multicenter case-control study.
Socioeconomic factors may play a role in the development of arthrofibrosis following total knee arthroplasty. Using manipulation following total knee arthroplasty as a surrogate for stiffness, this multicenter case-control study found that African American and young patients ( <45 years of age) had twice the odds for manipulation compared with Caucasian and older-age patients. (http://www.ncbi.nlm.nih.gov/pubmed/23102415)
Technical challenges of total knee arthroplasty in skeletal dysplasia.
Total knee arthroplasty (TKA) in patients with skeletal dysplasias is particularly challenging as a result of the anatomic variances and substantial bony deformities. Little has been written regarding technical considerations that should be made when performing TKA in skeletal dysplasia. (http://www.ncbi.nlm.nih.gov/pubmed/20706808)
Kim RH1, Scuderi GR, Dennis DA, Nakano SW. Clin Orthop Relat Res. 2011 Jan;469(1):69-75. doi: 10.1007/s11999-010-1516-0.
Lateral retinacular release rates in mobile- versus fixed-bearing TKA.
Controversy exists as to whether bearing mobility facilitates centralization of the extensor mechanism after TKA. To assess the incidence of lateral retinacular release, we retrospectively reviewed 1318 consecutive primary TKAs (1032 patients) performed by one surgeon using either a rotating-platform bearing (940) or a fixed bearing (378) from the same implant system. (http://www.ncbi.nlm.nih.gov/pubmed/18709430)
Yang CC1, McFadden LA, Dennis DA, Kim RH, Sharma A. Clin Orthop Relat Res. 2008 Nov;466(11):2656-61. doi: 10.1007/s11999-008-0425-y. Epub 2008 Aug 16.
In vivo comparison of hip mechanics for minimally invasive versus traditional total hip arthroplasty.
Minimally invasive surgery has been developed to reduce incision
length, muscle damage, and rehabilitation time. However, reduced exposure of anatomical landmarks may result in technical errors and inferior implant survivorship. The objective of this study was to compare in vivo motions and hip joint contact forces during gait in total hip arthroplasty subjects, performed with either minimally invasive surgery or standard surgical approaches. (http://www.ncbi.nlm.nih.gov/pubmed/18022739)
Glaser D1, Dennis DA, Komistek RD, Miner TM. Clin Biomech (Bristol, Avon). 2008 Feb;23(2):127-34. Epub 2007 Nov 26.
- Della Valle CJ, Berry DJ, Bragdon CR, et al. Primary Total Hip Arthroplasty. In: Mont M a., Tanzer M, eds. Orthopaedic Knowlege Update: Hip and Knee Reconstruction 5. 5th ed. Rosemont, IL: American Adademy of Orthopaedic Surgeons; 2016:377-391.
- Dennis DA, Kim RH, Conrad DN. Custome Acetabular Components for Acetabular Revision. In: Callaghan JJ, Rosenberg AG, Rubash HE, Clohisy J, Beaule P, DellaValle C, ed. The Adult Hip: 3. 3rd ed. Lippincott Williams & Wilkins; 2016:1362-1371.
- Yang CC, Dennis DA. Mobile-Bearing Total Knee Arthroplasty: Technique and Clinical Results. In: Vaidya S V., ed. Basics in Hip and Knee Arthrplasty. 1st ed. RELX India Private Limited; 2016:280-286.
- Duke J, Dennis DA. Cementation Techniques in Total Knee Arthroplasty. In: Vaidya S V., ed. Basics in Hip and Knee Arthrplasty. 1st ed. RELX India Private Limited; 2016:240-248.
CORR Insight Articles:
- Dennis DA. CORR Insights: Do Stemmed Tibial Components in Total Knee Arthroplasty Improve Outcomes in Patients With Obesity? Clin Orthop Relat Res. 2016:1-9. doi:10.1007/s11999-016-4791-6.
- Douglas A. Dennis M. CORR Insights: No Difference Between Trabecular Metal Cones and Femoral Head Allografts in Revision TKA: Minimum 5-year Followup. Clin Orthop Relat Res. 2016. doi:10.1007/s11999-016-4898-9.
- Jennings JM, Randell TR, Green CL, Zheng G, Wellman SS. Independent Evaluation of a Mechanical Hip Socket Navigation System in Total Hip Arthroplasty.
Acetabular cup malpositioning during total hip arthroplasty may lead to impingement, instability, wear-induced osteolysis, and increased rates of revision surgery. The purpose of this study was to independently evaluate the accuracy of acetabular cup orientation using a novel mechanical navigation device. An adjustable, reusable mechanical navigation device was used in a consecutive series of patients. Angles (inclination and anteversion) were measured by 2 independent reviewers with a validated 2-dimensional/3-dimensional matching application using a preoperative computed tomographic scan and a postoperative plain film
J Arthroplasty. 2016;31(3):658-661. doi:10.1016/j.arth.2015.09.052.
Jennings JM, Dennis DA, Kim RH, Miner TM, Yang CC, Mcnabb DC. False-positive Cultures After Native Knee Aspiration : True or False.
Synovial fluid aspiration is a routine practice used by most orthopaedic surgeons to aid in the diagnosis of joint infection. In patients for whom there is a low pretest probability of infection, a positive culture—particularly if it is a broth-only culture—may be considered a contaminant, especially if the bacterial species are skin pathogens. To our knowledge no study has evaluated the incidence of con- tamination of aspirations from the native knee. What is the frequency of false-posi- tive cultures among knee aspirations of the native knee? Two hundred patients, with a total of 200 knees, with the diagnosis of degenerative osteoarthritis undergo- ing a total knee arthroplasty (TKA) were identified for this study. None of these patients had symptoms, signs, or laboratory studies to suggest the presence of joint infection; a positive culture in this population therefore would be considered contaminated. Thirty–two (16%) patients were excluded secondary to a dry aspiration. One patient was enrolled in the study but did not have the knee aspirated and another patient’s specimen was accidentally discarded. Each knee was aspirated under sterile conditions before performing the TKA. The fluid was sent for cell count and culture. If insufficient fluid was obtained for both cell count and culture, culture was performed rather than cell count.
Clin Orthop Relat Res. 2016. doi:10.1007/s11999-016-5194-4.
Jennings JM, Dennis DA, Yang CC. Corrosion of the Head-Neck Junction After Total Hip.
Corrosion of the head-neck junction of implants used in total hip arthroplasty is a complex problem. Clinical severity appears to be multifactorial, and the predictive variables have yet to be consistently identified in the literature. Corrosion should be considered in the differential diagnosis of hip pain following total hip arthroplasty regardless of the type of bearing surface used. The most common presentation, pain followed by instability, is similar to complications associated with metal-on-metal articulations. Thediagnosis of implant corrosion of the head-neck junction can be challenging; an infection workup should be performed along with analysis of serum metal ion levels and cross-sectional imaging. In the short term, a well-fixed stem maybe retained, and the exchange of an isolated head with a ceramic femoral head seems to be a promising option for certain implants. Further research with longer follow-up is warranted, and high levels of evidence are needed to determine whether this approach is generalizable.
Jennings JM, Thiele RAR, Krynetskiy E, Wellman SS, Attarian DE, Bolognesi MP. Independent Analysis of the Dorr Classification of Proximal Femoral Morphology : A Reliability Study.
The purpose of this study was to assess the inter- and intraobserver reliability through visual perception of a previously described classification system of proximal femoral morphology. The interobserver reliability ranged from slight to moderate across testing. Experience appears to play a role as the intratester reliability did not differ with fellowship trained attending physicians, but differences were seen with junior- and senior-level residents. The diversity of the proximal femoral morphology likely represents a continuum rather than three distinct shapes. This may imply that for many proximal femoral canals, characterization of a single type may not be possible. Further research is warranted to determine the clinical significance of these findings.
Duke Orthop J. 2016;6(July 2015):1-4.
Levy DL, Ryan Martin J, Watters TS, Jennings JM, Miner TM. Primary total knee arthroplasty in a patient with a chronic extensor mechanism deficiency.
A 44-year-old female presented with a chief complaint of left knee pain and dysfunction. The patient had a complex surgical history including patellar fracture repair, subsequent patellar ligament repair, and ultimately allograft reconstruction which was complicated by septic arthritis requiring graft resection. On presentation to our clinic, she was noted to have significant degenerative disease in addition to chronic extensor mechanism deficiency. She underwent primary total knee arthroplasty with concomitant tibial tubercle osteotomy and advancement. The patient has had an excellent result postoperatively including return of full range of motion without residual extensor lag.
Arthroplast Today. 2016;2(1):2-5. doi:10.1016/j.artd.2015.12.005.
Martin JR, Jennings JM, Levy DL, Watters TS, Miner TM, Dennis DA. What Preoperative Radiographic Parameters Are Associated With Increased Medial Release in Total Knee Arthroplasty?
Preoperative varus deformity of the knee is a common malalignment in patients under- going primary total knee arthroplasty (TKA). We are unaware of any studies that have correlated how various preoperative radiographic parameters can predict the amount of medial releases performed to achieve optimal coronal alignment and ligamentous balance. A retrospective review was performed on 67 patients who required at least a medial tibial reduction osteotomy (MTRO) during primary TKA to achieve coronal balance. This patient population was matched 1:1 to another cohort of TKA patients by age, gender, and body mass index who did not require an MTRO. A radiographic evaluation was used to compare the 2 cohorts.|
J Arthroplasty. 2016. doi:10.1016/j.arth.2016.08.018.
Martin JR, Jennings JM, Watters TS, Levy DL, McNabb DC, Dennis DA. Femoral Implant Design Modification Decreases the Incidence of Patellar Crepitus in Total Knee Arthroplasty.
Patellar crepitus is a complication most commonly seen in patients implanted with a posterior-stabilized total knee arthroplasty (TKA). Recently, design changes in the patellofemoral geo- metry and the intercondylar box ratio have been optimized in newer TKA designs. A comparative study was performed to analyze the incidence of patellar crepitus between a historical vs modern TKA design. A retrospective review of all patients at our institution that underwent a primary TKA with either a PFC Sigma or Attune posterior-stabilized TKA (DePuy, Inc, Warsaw, IN), with a minimum of 1- year follow-up duration was performed. A total of 1165 participants implanted with the PFC Sigma and 728 with the Attune design were analyzed. Patellar crepitus incidence, functional scores, and range of motion were recorded at each follow-up appointment. Statistical analyses were performed between the 2 groups to determine if there were differences in clinical outcomes.
J Arthroplasty. 2016:1-4. doi:10.1016/j.arth.2016.11.025.
Martin JR, Watters TS, Levy DL, Jennings JM, Dennis DA. Removing a well-fixed femoral sleeve during revision total knee arthroplasty.
The following surgical technique describes a case of a 51-year-old man with severe juvenile rheumatoid arthritis that required a 2-stage revision of an infected revision total knee implant. The patient had previously been implanted with a revision rotating platform, constrained condylar device which gained excellent fixation through the use of diaphyseal-engaging stems, and a well-ingrown, fully porous-coated femoral metaphyseal sleeve. To avoid intraoperative complications while removing the femoral sleeve, a novel technique for femoral sleeve extraction was used. Using this technique, the femoral sleeve was successfully removed without intraoperative fracture or substantial bone loss.
Arthroplast Today. 2016:1-5. doi:10.1016/j.artd.2016.05.005.
Martin JR, Watters TS, Levy DL, Jennings JM, Boyle JP, Dennis DA. Medial tibial “spackling” to lessen chronic medial tibial soft tissue irritation.
We describe a unique, utilitarian reconstructive treatment option known as tibial “spackling” for chronic, localized medial joint line pain corresponding with progressive radiographic peripheral medial tibial bone loss beneath a well-fixed revision total knee arthroplasty tibial baseplate. It is believed that this localized pain is due to chronic irritation of the medial capsule and collateral ligament from the prominent medial edge of the tibial component. In the setting of failed nonoperative treatment, our experience with utilizing bone cement to reconstruct the medial tibial bone defect and create a smooth medial tibial surface has been successful in eliminating chronic medial soft tissue irritation.
Arthroplast Today. 2016:1-5. doi:10.1016/j.artd.2016.05.003.
Mcnabb DC, Dennis DA, Kim RH, Miner TM, Yang CC, Jennings JM. Determining False Positive Rates of Leukocyte Esterase Reagent Strip When Used as a Detection Tool for Joint Infection.
Use of leukocyte esterase (LE) testing of synovial fluid as an adjunct to the infection workup in total joint arthroplasty patients has been advocated. The purpose of this study was to determine the false positive rate of this test. Two hundred patients with the diagnosis of degenerative osteoarthritis undergoing a total knee arthroplasty were identified for this study. The knee joint was aspirated under sterile conditions before performing the total knee arthroplasty. The fluid was analyzed with an LE reagent strip.
J Arthroplasty. 2016;32(1):220-222. doi:10.1016/j.arth.2016.05.065.
McNabb DC, Jennings JM, Dennis DA. Fracture of a spline of the femoral stem in an ingrown modular hip implant.
Physiologic strain patterns of the femur are altered by the bending stiffness of the implant as well as the loading pattern of the implant itself. The Savish Range of Motion (S-ROM) femoral stem has been designed with flutes (to decrease distal material) and with a coronal slot (to decrease stiffness). The purpose of this case report is to briefly discuss design characteristics of femoral stems and their relationship to thigh pain as well as to describe the only report in the literature of a fracture of the anterior spline of
Hip Int. 2016;26(4):0-0. doi:10.5301/hipint.5000399.
Watters T, Levy D, Kim R, Miner T, Dennis D, Jennings J. Tourniquet Application During Total Knee Arthroplasty Does Not Benefit Perioperative Blood Loss or Transfusion Requirement with the Routine Use of Tranexamic Acid.
The use of a tourniquet during total knee arthroplasty (TKA) continues to be a matter of debate. Advantages of tourniquet use include improved visualization, decreased intraoperative and to- tal blood loss, and possibly decreased transfusion requirement. However, the recent widespread adop- tion of antifibrinolytic therapy with tranexamic acid (TXA), may negate these benefits. The purpose of this study was to evaluate perioperative blood loss and transfusion requirement with two different tour- niquet application strategies, and surgery without the use of a tourniquet during routine, primary cement- ed TKA. A retrospective cohort study was performed of 300 patients undergoing TKA at a single institution after the implementation of a routine intravenous TXA administration protocol and consisted of three groups based on tourniquet usage: tourniquet inflation before incision and deflation following ce- ment hardening (TQ), tourniquet inflation prior to cement application and deflation following hardening (Partial TQ), and no tourniquet usage (No TQ). Each group consisted of 100 consecutive patients. Peri- operative blood loss, change in hematocrit and transfusion requirement were compared between groups.
Reconstr Rev. 2016;6(3):43-47.
- Population-based Evaluation of Knee Mechanics Considering Inter-subject and Surgical Alignment Variability
University of Colorado Muscle Performance Lab
The surgeons of Colorado Joint Replacement have had the privilege of working with the physical therapy department at the University Of Colorado School Of Medicine over the past several years. We have performed a number of studies assessing the effect of postoperative physical therapy on eventual performance of a patient’s joint replacement. While we have found that our total joint patients are doing very well, we have also observed that many could be further improved with more advanced physical therapy protocols.
If you are interested in participating in future studies or being informed of opportunities that are available to you, please complete the authorization form (Patient Authorization to Disclose Protected Health Information) below that allows us to provide the University of Colorado School of Medicine’s physical therapy department your name, address, and phone number so they may contact you to determine whether you are a potential candidate to be involved in future studies. This authorization form in no way signs you up for any specific study. We appreciate your consideration of participation in this advanced research to allow us to offer better care. Any future questions you may have regarding this form, you may discuss this with your Colorado Joint Replacement physician.
Collaborative-care Interventionto 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 forTotal 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).
Recently Completed Research
Strength and Function FollowingTotal 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 Tourniquetand 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.
For more information about the Muscle Performance Lab please visit their website at:
University of Denver Center for Orthopaedic Biomechanics
The Center for Orthopaedic Biomechanics at the University of Denver applies engineering principles to investigate clinically relevant issues in Orthopaedics. Using a combination of experimental and computational tools, the Center performs research in joint mechanics, human motion, musculoskeletal modeling, wearable sensor systems and implant device testing.
Computational Modeling of Joint Mechanics
Computational models provide insight into the loading and contact mechanics on implants and the structures of a joint that are not possible to measure experimentally in patients. Through a close partnership between DU and Colorado Joint Replacement, computational models have been developed to help address clinical questions. For example, the effects of patient factors, implant size and placement on patellar crepitus, an irritation of the tendon caused by contact with the femoral implant geometry, has been assessed. Image analysis has been performed on intraoperative photographs to characterize how implant design and size selection influenced the implant’s coverage of the resected bone.
Computational model of knee simulator (left) that enables assessment of contact mechanics (middle) and implant stresses (right).
Implanted knee model investigates the potential for crepitus by assessing contact between tendon and implant during knee flexion.
Measurement of Natural and Implanted Joint Mechanics
Joint replacement restores a patient’s functionality and enhances their ability to perform activities of daily living. Understanding the mechanics (movements and loading) of the body is critical to understanding the environment of the implant, which can inform implant design. Patients from Colorado Joint Replacement and healthy normal counterparts have participated in data collections in the Human Dynamics Laboratory, located on the campus of the University of Denver. Data collections are focused on functional assessments, and also challenging activities, including stair ascent/descent and pivoting. The lab at DU has the unique capability of measuring whole body motion and forces using an optical camera system and force plates, and also the local joint motion using a stereo radiography system. Supported by a grant from the National Science Foundation, the high-speed stereo radiography system allows dynamic x-ray imaging in two planes to accurately measure the motions of the joint inside the body.
If you are interested in participating in a study, email us.
Data collection of a subject during gait (left) and stereo radiographic images of a patient with a total knee replacement during a leg extension (right).
Video from the high-speed stereo radiography (HSSR) system of a natural knee during a pivot activity.
Recently Completed Research:
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.
For more information about the Center for Orthopaedic Biomechanics department at the University of Denver please visit their website at: www.du.edu/biomechanics
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.
University of Tennessee Department of Biomedical Engineering and Biomechanics Current Research
In Vivo Mechanics for Subjects Having Either a DePuy Attune Fixed or Mobile Bearing PS TKA
The primary goal of this study is to compare and contrast the kinematics (knee motion) between the Attune Fixed Bearing Posterior Stabilized knee and the Attune Mobile Bearing Posterior Stabilized knee using a 3D-to-2D computer overlay process. Subjects will be asked to perform a deep knee bend (and other activities) while under fluoroscopic surveillance (video x-ray). A custom built software package will be used to determine the kinematics. This program uses still frames from the fluoroscopic video and three-dimensional computer models to re-create the motion of each subject. Range-of-motion, axial rotation, and anterior/posterior contact will be analyzed. Effects of patella type will also be explored.
Recently Completed Research
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.
For more information about the Biomedical Engineering and Biomechanics department at the University of Tennessee please visit their website at:
Total Knee Replacement Rehabilitation Study
As part of ongoing joint replacement and orthopedics research, the physicians of Colorado Joint Replacement have teamed with the University of Colorado School of Medicine to investigate ways to improve patient rehabilitation following total knee replacement surgery.
In order to identify improvements to post-operative rehabilitation programs, researchers will examine the effects of a high-intensity physical therapy for total knee replacement patients. The study, which is recruiting eligible patients through 2013 via physician recommendation, includes high-intensity exercises and weight lifting to strengthen various muscle groups. Patients will receive home and outpatient physical therapy for 11 weeks, all the while steadily increasing the amount of activity.
Patients who are considering a total knee replacement are encouraged to consult the physicians at Colorado Joint Replacement to see if they are eligible to participate in the study and take advantage of the research-related rehabilitation services.