According to the Agency for Healthcare Research and Quality, more than 285,000 total hip and 600,000 knee replacements are performed each year in the United States. In the 1980s, cementless implants were introduced. Direct bone ingrowth and ongrowth, namely osseointegration, to the implant led to a more durable implant-bone interface than possible with cement and avoided the complications caused by cement insertion and the troublesome removal of cement during revision surgery. Because cementless implants depend on new bone growth for stability, they require a longer healing time than cemented replacements. Many studies have been performed to optimize implant geometry, and surface topography, texture and coating to maximize new bone growth. However, the longevity of these implants is not always predictable. One cause of failure is the implant instability caused by suboptimal osseointegration. Our lab has developed a mouse model using a titanium porous implant inserted to proximal tibia to mimic the knee arthroplasty. With this model, we will investigate factors and cell-signaling pathways which affect and regulate osseointegration. We will also test the efficacy of various anabolic and anti-resorptive agents on osseointegration. Histomorphometry, back scattered electron microscopy, microCT, mechanical testing will be used to asses bone quantity and quality. Immunohistochemistry and rtPCR will be used to detect signaling pathways.The summer student will assist with mouse surgery, administration of agents to mice, tissue collection, and data analysis.
The use of the genetic screening is a new tool for the treatment of adolescent idiopathic scoliosis. This has so far been useful in predicting which patients with mild to moderate scoliosis will progress to require surgical treatment. The utility of genetics-based testing has not been used to predict post-operative progression. As such, we have been unable to find evidence of genetics-based testing to predict risk of post-operative progression. A genetics-based test should be constant over the course of a patient’s lifetime. Therefore, we will be able to study risk of post-operative progression more accurately and efficiently in a retrospective fashion, in particular by identifying those patients who progress to further deformity despite definitive treatment. Genetic testing has only been studied with respect to its relationship to overall magnitude of progression. There has been, to date, no discussion of its association with curve type or its relationship to further progression after fusion. For example, vertebra level selection in posterior spine fusion is a controversial topic, which will likely elicit differing opinions as long as the procedure is performed. Often the lumbar curve will not be touched during a spinal fusion, but the current algorithms used to fuse or not fuse (a so-called “selective thoracic fusion”) involve only classic clinical criteria. The student will perform genetic testing on pediatric patients who have already undergone spinal fusion as part of a historical database. The student will also enroll patients for further study in using the genetic test as part of future surgical decision-making. The student will have the opportunity to present his/her research to the pediatric orthopedic surgery department, as well as scrub in the operating room during spine surgery.
Reverse shoulder arthroplasty is successful at eliminating pain and improving function for patients with shoulder arthritis and a dysfunctional rotator cuff. Traditionally, this prosthesis is designed such that the center of shoulder rotation is medial to the glenoid implant so that shear forces are minimized and failures are reduced. Recent studies have suggested that there may be functional benefits to lateralization, such as improved internal and external rotation, better stability, better shoulder contour, and reduced scapular notching. However, the effects of lateralization on the reactive forces across the implant are poorly understood. This study will evaluate the forces across a reverse total shoulder replacement with varying degrees of lateralization. This will be accomplished with a custom-made shoulder simulator that can replicate muscle forces across the joint. Using this simulator, we plan to determine the joint reactive forces across the implant with varying degrees of lateralization. This data will be used to develop a finite element computer model to determine how various glenoid designs can counteract these forces to ensure implant longevity. The student will be responsible for assisting in cadaver dissection and reverse total shoulder implantation, specimen preparation, running of the simulator, data acquisition, data analysis, and preparation of a manuscript. The student will work closely with a surgeon, research engineer and a doctoral student and will have exposure to senior surgeons and scientists. The only requirement for the position is an enthusiasm for the work at hand.
Biomechanical research will be conducted to compare our novel anatomical interference screw reconstruction of the scapholunate interosseous ligament (SLIL) to the modified Brunelli technique (MBT). We believe that an anatomic reconstruction of the SLIL, secured with interference screws, can provide sufficient stability between the scaphoid and lunate without compromising wrist ROM. It is hypothesized that our interference screw reconstruction technique will restore static scapholunate (SL) relationships (as measured by SL interval and SL angle) and intact wrist kinematics as well as the MBT reconstruction. The medical student will work with the investigator during cadaver dissection of the ligaments, ligament reconstruction, and biomechanical testing of the intact and reconstructed ligaments. The medical student may conduct literature reviews relevant to the project. Research findings will impact surgical approaches to SLIL reconstruction. In addition, the medial student will accompany the investigator to office hours and surgery to better understand how concepts investigated during biomechanical research may ultimately translate into practice.
Clinical examination of the ACL-injured and -reconstructed knee is severely limited. For example, a uniplanar test of anterior laxity shows no correlation with patient outcome. In contrast, the pivot shift exam, a test of the rotational stability of the knee, is closely associated with patient outcomes. In fact, positive findings with this exam correlate with compromised function and may indicate increased risk of osteoarthritis (OA). Unfortunately, this exam is qualitative and subjective. Lack of quantitative and objective clinical measurement of knee rotations in large cohorts of patients severely hampers clinical research aimed at comparative effectiveness of ACL reconstruction techniques for public health recommendations, and impairs the ability to determine the pathomechanics that link ACL injury and reconstruction to OA. Our group is working to overcome this limitation by developing a new measurement instrument, which will provide objective, quantitative measurement of knee rotations. As a first step in the clinical implementation of this new measurement instrument, we will conduct an in vitro study to assess its safety, accuracy and reliability. The summer student will be involved in all aspects of this study including specimen preparation and dissection, and data collection and analysis.
Initial fixation of prosthetic implants to bone relied upon the use of acrylic bone cement for fixation. Unfortunately, over time the cement would fatigue and lead to prosthetic loosening. The development of biologic fixation of implants to bone with the use of porous implants has lead to improved durability. Recently, there has been a movement to change the shape and texture of the porous implant surface by using more complex 3-dimensional configuration with the hope of enhanced fixation. Whether this leads to improved fixation is not known. The assessment of the extent of bone ingrowth into traditional porous implants has been determined by detecting back-scattered electrons (BSE) during scanning electron microscopy, an accurate but timely and costly technique. These 1st generation porous implants were largely made out of titanium alloy and were compatible with this technique. The recent shift to the 3-D surfaces has employed implants made of both titanium and tantalum, another biologically friendly metal. Unfortunately, the use of BSE techniques to assess fixation has proven difficult with implants made from tantalum in addition to the time and cost associated. We have recently started investigating the use of a high resolution optical microscope combined with histological staining techniques to determine if the same metrics for evaluation of bone ingrowth, namely extent and depth of penetration of bone into the porous coating, could be attained with this instrument.
Retrieval analysis is valuable in assessing in vivo surface damage on orthopaedic devices and contributes to understanding the responsible mechanisms and subsequently improving implant materials and designs. Damage assessment traditionally employs subjective techniques to grade damage on the implant’s surface. Digital microscopy has improved our ability to localize and quantify damage, although it is unable to measure volumetric removal of material as a function of this damage. Laser scanning technology fills this niche, but provides lower resolution and minimal photographic evidence. Recent advances in imaging enables laser scan data to be rendered with photographs (photorendering), thus combining the strengths of both techniques. We have recently begun using similar methods to improve our capabilities to assess damage in implants and potentially correlate volumetric changes with the damage assessment. While the methodology of combining microscopy to laser scan data works anecdotally, more work remains in testing the robustness of fit and circumventing limitations in both the microscopy data and the software used to stitch images together. As important, the improved resolution images provided by the microscope offers an opportunity to automate damage assessment, yielding damage mapped images that can also be overlayed on the laser scan data. This may provide a means to better quantify observed damage and yield meaningful correlations with volumetric changes due to wear and deformation of the implant.
This research project is a biomechanical study that will utilize 3D motion analysis to investigate the relationship between wrist range of motion and wrist function. The long term goal of this work is to develop an objective clinical outcome measure for wrist pathologies that accurately reflects wrist function. 3D motion analysis will be used to quantify wrist circumduction, defined as a smooth circular wrist motion along the boundary limits of the wrist. Results for both normal and individuals with restricted motion will be correlated with performance of various wrist dependent functional tasks
Total hip replacement surgery is one of the most successful procedures in orthopaedic surgery - one that restores function and quality of life. Traditional components include an acetabular component and a femoral component, which in recent years have come to heavily rely on biologic fixation rather than traditional cemented fixation. In our study we look at the safety and efficacy of an uncemented, hemispherical acetabular component that has been used by many orthopaedic surgeons for hip replacement, with a minimum 5 year follow up, in a cohort of over 250 consecutive patients over a four year period. Outcomes would be measured by radiographic parameters such as osseointegration, absence of radiographic lucency, presence of stress induced hypertrophy of bone, demarcation, etc. Our hypothesis is that this particular cup being studied has an exceptional track record and will prove to be safe and efficacious in contemporary total hip replacement. The student's role will be to collect demographic and clinical data through chart review. Additionally, the student will perform radiographic analysis to measure osseointegration over time.
The purpose of this clinical research study, "Total Hip Replacement at HSS in Subjects under 35 Years of Age: Retrospective Chart Review and Patient Follow-up," is to evaluate the survivorship of total hip arthroplasty (THA) in patients under 35 years of age, as well as to evaluate their functional levels. Ultimately, this information will help us to improve implants for patients, many of whom currently require custom implants due to unusual bone development. We have identified and reviewed charts on 711 patients (952 hips) performed at HSS since 1988. Patients under 35 who receive hip replacements have a wide variety of diagnoses, with the leading diagnoses being avascular necrosis, inflammatory arthritis, and developmental dysplasia of the hip. We have completed chart review for all patients and have begun to obtain follow-up and survivorship data on those patients with AVN and JIA. We will analyze and collect X-ray data on those patients with altered pathoanatomy (JIA, DDH and skeletal dysplasia). The medical student involved in this project will work to contact patients and collect follow-up data on survivorship, pain, and mobility. The student will prepare data for analysis and will present a talk at the completion of his rotation. The student will have the opportunity to attend daily educational conferences as well as scrub in the OR.
Bone morphogenetic proteins (BMPs) are growth factors that encourage the growth of cartilage and bone. Recombinant forms of these proteins are often used by surgeons when trying to help bones heal, when healing might be sub-optimal. Utilization of BMPs in children is controversial, and is not currently FDA-approved. The aim of this study is to assess how BMPs are used in children through analysis of discharge record databases: In which procedures and with which diagnoses are BMPs most frequently used? What are the long term outcomes following BMP utilization in children? Is BMP utilization associated with any post-operative complications in the long term? The medical student will perform a comprehensive review of the literature on this topic. He or she will work with diagnosis and procedure codes to identify cases in which BMP was used. He or she may help with statistical analysis depending on his/her experience and interest. He or she will contribute to interpretation of results, and will have the opportunity to prepare results for presentation and publication. The medical student will also have the opportunity to gain clinical experience in pediatric orthopedics, working with pediatric orthopedic surgeons both in the operating room and the clinic.
There is established evidence that frailty is a measurable quality among patients. There are a number of different methods for measuring frailty, and they fall under either performance-based (for instance, the Fried Frailty Index) or self-reported (for instance, the Modified Frailty Index by Farhat et al., 2012) categories. Studies have shown that these measures can have predictive power for surgical outcomes or development of dependence and disability over time. However, no studies have shown whether frailty can acutely predict the level of post-operative care expected for patients entering post-trauma surgery. Specifically, we are interested in predicting the level of post-operative care (ICU, step-down, or floor) for patients undergoing orthopaedic related surgery. For this project we are designing a self-reported test using existing validated scores to measure the frailty of patients admitted to the hospital undergoing trauma surgeries. This information will allow physicians to identify high-risk patients and appropriately adjust management and allocation of resources. Under the guidance of Dr. Joseph Lane, the medical student’s role would be to collect demographic and clinical information, administer the frailty questionnaire, and analyze the data collected. The student will also have the opportunity to participate in some of procedures and follow these patients in clinic.
Hip fractures are a major public health problem, and surgical intervention is a crucial aspect of their management. From 1986 to 2005, the mean occurrence of hip fractures was 957 per 100,000 in women and 414 per 100,000 in men annually. The 180-day mortality rates for these individuals have been reported as high as 14.3% in women and 22.9% in men. Identifying risk factors for poor recovery time, morbidity, mortality, and complications may allow physicians to identify high-risk patients and appropriately adjust management and allocation of resources. Furthermore, risk stratification may indicate which patients may most benefit from intervention. We plan to measure functional outcomes differently by assessing several physical therapy measures including the timing of bed-to-chair transfer, standing, walking, and the clearance for discharge by the physical therapist. We also plan to investigate how operating in regular timing (earlier than 6pm) versus emergency timing (after 6pm) are associated with these outcomes. We hypothesize that patients with hip fractures operated during regular operative timings have less morbidity and shorter recovery times than those operated in emergency timings and that the patients with hip fractures operated within 48 hours of hospital admission show less morbidity and shorter recovery times than those operated after 48 hours of hospital admission. Under the co-guidance of Dr. Pingal Desai and Dr. Joseph Lane, the medical student’s role would be to collect demographic, radiographic, clinical and laboratory data through chart review. The student will also have the opportunity to participate in some of procedures and follow these patients in clinic.
The purpose of this study is to evaluate the response of nerves to different nerve wraps in a mouse model with an induced scarred tissue bed. We will be using IL-4/IL-10 null mice, which show increased scarring, to evaluate the sciatic nerve response to three nerve wraps following the creation of a scarred tissue bed. Muscular tissues surrounding the sciatic nerves of both left and right rear legs will be dissected to expose the nerve; each nerve will be isolated out of the tissue bed, and wrapped with either AxoGuard (porcine submucosa), NeuraWrap (bovine type I collagen), vein wrap, or no wrap (sham control). The rats will be sacrificed at 2 month and 4 month intervals. Endpoint testing will include assessment of neovascularization, adhesion, scarring, nerve gliding, nerve histology and nerve function. The student will be able to participate in study design, assisting with the animal surgery, endpoint testing, and manuscript preparation.
Hypotheses: 1. Excessive graft strain will adversely affect healing of a tendon graft in a bone tunnel. 2. Novel MRI pulse sequences will allow detection of differences in graft collagen ultrastructure in response to varying levels of strain loading. Methods: ACL reconstruction will be performed in a rabbit model. We have verified that we can induce different levels of graft strain by varying the location of the femoral tunnel and knee flexion angle for graft fixation. We then use an external fixator on the knee to control post-operative knee motion. The independent variable (graft strain) is controlled by knee motion done using a custom-designed motion device with the animal under anesthesia. We vary the magnitude, frequency, and time of onset of strain loading. The primary outcome measure is MRI appearance of the graft (quantitative MRI- measurement of T2 relaxation time and T1 rho). Secondary outcome measures are graft healing to bone (histology) and graft attachment strength and stiffness (biomechanical testing). Role of Student: The student will participate in all aspects including animal surgery, specimen harvest, tissue dissection, biomechanical testing, data analysis, and manuscript preparation. The student will be exposed to the research environment in our laboratory, which includes senior scientists, post-doctoral fellows, technicians, and other students. They will be exposed to numerous basic laboratory techniques, and will also participate in regular laboratory meetings.
Heterotopic ossification (HO) is a recognized complication of arthroplasty which can cause pain and significantly limit function. HO is a well recognized complicates total hip arthroplasty (THR) in patients with diseases such as ankylosing spondylitis, which are characterized by the formation of new bone. Psoriatic arthritis (PsA) is also a form of arthritis, more common than ankylosing spondylitis, in which new bone is formed. Although it is not usually associated with increased risk of HO, preliminary work by our group suggests HO may be increased in patients with psoriatic arthritis, and possibly in patients with cutaneous psoriasis (PsC) alone. Although medications such as non-steroidal anti-inflammatory drugs (NSAIDS) can affect HO rates, it is unclear how often these regimens are actually used, and how effective they are in psoriatic patients. Our study will investigate the prevalence of HO in patients with psoriatic arthritis and psoriasis, and clarify the effect of HO and HO prophylactic regimens on post-operative pain and function. The role of the student in this project will be to review radiographs of patients with validated diagnosis of PsA and PsC after THR, and grade HO using the Brooker classification. Additional information will be gathered by chart review to determine the exposure in each case to NSAIDS, and to determine if prophylaxis for HO was administered.
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