Biomedical subjects
Publications and source records attributed to Michael A Kelly.
Arthroscopic debridement of the arthritic knee remains a source of controversy in the surgical management of osteoarthritic knees. Lack of a clear consensus on patient indications and surgical technique as well as unpredictable clinical success continues to generate this controversy. A conservative arthroscopic debridement technique appears to have a more limited role today than in the past.
In designing a posterior-stabilized total knee arthroplasty (TKA) it is preferable that when the cam engages the tibial spine the contact point of the cam move down the tibial spine. This provides greater stability in flexion by creating a greater jump distance and reduces the stress on the tibial spine. In order to eliminate edge loading of the femoral component on the posterior tibial articular surface, the posterior femoral condyles need to be extended. This provides an ideal femoral contact with the tibial articular surface during high flexion angles. To reduce extensor mechanism impingement in deep flexion, the anterior margin of the tibial articular component should be recessed. This provides clearance for the patella and patella tendon. An in vivo kinematic analysis that determined three dimensional motions of the femorotibial joint was performed during a deep knee bend using fluoroscopy for 20 subjects having a TKA designed for deep flexion. The average weight-bearing range-of-motion was 125 degrees . On average, TKA subjects experienced 4.9 degrees of normal axial rotation and all subjects experienced at least -4.4 mm of posterior femoral rollback. It is assumed that femorotibial kinematics can play a major role in patellofemoral kinematics. In this study, subjects implanted with a high-flexion TKA design experienced kinematic patterns that were similar to the normal knee. It can be hypothesized that forces acting on the patella were not substantially increased for TKA subjects compared with the normal subjects.
Osteoarthritis of the knee is common, increasing with age in both women and men, but is generally more prevalent in women following the fourth decade. Osteoarthritis may be primary/idiopathic or secondary as a consequence of trauma, surgery, infection, or another disease process. Normal articular cartilage is composed of an extracellular matrix and chondrocytes. This matrix contains water, collagen fibers, and proteoglycan macromolecules cross-linked into an integrated network with hyaluronic acid. Osteoarthritis represents an imbalance in the destructive and synthetic processes of the cartilage that leads to erosion of the cartilage. In addition, there is a decreased concentration and viscosity of the synovial fluid in osteoarthritic patients, and this may decrease the lubricating and cushioning properties of the joint. There is also an underlying inflammation of the synovium, as well as damage or reactive changes in the subchondral bone. The entire process is thought to involve a complex interaction of cells and soluble mediators such as cytokines, growth factors, inflammatory mediators, metalloproteinases, and chondrodegradative enzymes. Understanding the biochemical and molecular changes that occur in the joint is requisite to the development of treatments for osteoarthritis of the knee that address both the symptoms of pain and loss of mobility as well as the underlying disease progression. The clinical goal of the management of osteoarthritis should be to treat not only the symptoms of the disease, such as pain and decreased mobility, but also the underlying pathology of the degenerative process.
The effective management of pain in osteoarthritis of the knee is complex and subject to many treatment- and patient-related variables. This article reviews the broad range of nonsurgical options available to the clinician, which include pharmacologic and nonpharmacologic measures such as weight loss, physical and occupational therapy, exercises, and the use of assistive devices. Pharmacotherapeutic options for osteoarthritis of the knee include the use of oral agents, topical creams, and intra-articular injections of hyaluronans or glucocorticoids. Since pain in the osteoarthritic knee can vary widely from patient to patient in its origins, pain management should address the individual patient's symptoms, level of pain, and functional disabilities.
Intra-articular hyaluronans are used to treat pain associated with osteoarthritis of the knee. Many controlled clinical studies have demonstrated their efficacy for this indication. The rationale for the use of hyaluronans therapeutically is based on observations that hyaluronic acid is an important component of the synovial fluid acting as a cushion and lubricant for the joint and also serving as a major component of the extracellular matrix of the cartilage, helping to enhance the ability of cartilage to resist shear and maintain a resiliency to compression. While intra-articular hyaluronans are indicated at this time only for the treatment of pain in osteoarthritis of the knee, there are data to suggest that they may also be useful in treating degenerative disease of other articular joints, as well as have an impact on disease progression. The mechanisms by which hyaluronans mediate their clinical benefit seem to be multifactorial and biologically related, in contrast to the notion that they provide only viscous fluid replacement. The safety profile of intra-articular hyaluronans is very favorable and, because they are used as a local therapy, there are no known drug interactions-an advantage for patients receiving treatment for comorbid conditions. Some adverse effects, such as pseudosepsis, have been associated with cross-linked hyaluronan agents and do not appear to be class related.
Hyaluronan therapy has numerous medical applications, including the treatment of joint arthropathies, wound healing, prevention of postsurgical adhesions, treatment of urinary incontinence, ophthalmic surgery, and tissue augmentation and engineering. Studies have been conducted and are ongoing to evaluate the efficacy of intra-articular hyaluronans in disease modification in osteoarthritis of the knee; efficacy in disease states other than osteoarthritis; as adjunct therapy after joint surgery; and in joints other than the knee--namely the shoulder, hand, hip, temporomandibular joint, spine, foot, and ankle. Preliminary results have been promising and parallel what has been found in treatment of osteoarthritis of the knee. Research also continues into the development of chemically modified derivatized hyaluronan to optimize responses and enhance duration of action, as well as to expand the uses of this therapeutic modality.
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Recent improvements in total knee arthroplasty (TKA) surgical technique, instrumentation, and prosthetic design have decreased the incidence of extensor mechanism complications following TKA. The majority of these complications continue to be secondary to errors in surgical technique. Extensor mechanism complications following TKA include soft-tissue impingement, instability, patellar fractures, patellar component failures, and extensor mechanism rupture. Both nonsurgical and surgical treatment may be used in the management of these complications. However, the majority of these complications are avoidable with attention to proper surgical technique and selection of appropriate patellar components in TKA.
To do a successful total knee arthroplasty (TKA), adequate exposure of the tibial plateau and distal femur is required. Difficulty with exposure often is encountered in the patient with a stiff or ankylosed knee. This can lead to complications including component malpositioning and extensor mechanism problems, such as patellar tendon rupture. In these cases where the knee has limited motion preoperatively, knowledge of advanced techniques for soft tissue treatment, and for optimizing exposure are required. Numerous such techniques have been described, including the quadriceps snip, V-Y quadriceps turndown, tibial tubercle osteotomy, and femoral peel. A systematic review of these techniques, including indications and results, based published reports and our experiences, is presented.
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Posterior cruciate ligament-substituting total knee prostheses have been used extensively since the original posterior-stabilized condylar prosthesis was introduced more than 2 decades ago. The key design principle of this prosthesis was the incorporation of a cam and post mechanism on the femoral and tibial components. This mechanism was intended to function as a mechanical substitute for the posterior cruciate ligament, to optimize prosthesis roll back in flexion, and to avoid flexion instability by preventing posterior subluxation. Central to the use of these devices was the surgical technique, which required resection of both cruciate ligaments and creation of symmetric flexion and extension gaps with equal medial and lateral soft tissue tension. Modifications to the original design have been introduced gradually; these include changes to the patellofemoral geometry, and the addition of monoblock and modular metal-backed tibial components. Despite these changes, the key concepts of the prosthesis design and surgical technique have remained constant. The clinical results obtained with the use of these designs have been reported extensively. Long-term results at greater than 10 years continue to duplicate the outstanding early results with prosthesis survivorship exceeding 95% and high levels of patient function.