Knee Replacement Design - Essay Example

This house believes that the total knee replacement design should be improved. ‘For the motion Total knee replacement commonly referred as total knee arthroplasty can be explained as a procedure involving the surgery of the knee aimed at relieving pain and the restoration of movement in severe cases of arthritis. Surgery is a culmination of failed non-operative methods of treating knee arthritis with the surgery type highly dependent on age, underlying conditions, and anatomy. The use of operative solutions to knee problems has evolved since inception, but the major concern related to the surgery remains to be the design. The implant design is crucial in the determination of activity level patients can engage in after the knee replacement. Research indicates that massive restrictions have been caused owing to the implant disease, and this necessitates the improvement of implant designs for better service and improved mobility. The paper focuses and discusses parameters influencing the level of activities patients engage in after the knee replacement process. This is important in understanding the different aspects allowing normal high flexion owing to the implant design. The motion range attributed to flexion and other constraints are tied to the systematic design employed in the knee replacement surgery. New total knee replacement designs should be directed towards increased flexion ranges of motion generating movement closer to natural knees. Introduction Total knee replacement refers to the surgical procedure used in the replacement of surfaces that bear weight in the knee joint with the aim of reducing pain and averting possible disability. The necessity for knee surgery is occasioned by osteoarthritis and other arthritis related diseases affecting the knees. Cartilage defects, ligament tears, and meniscus tears might further occasion the surgery. The history of knee replacement surgery attempts is long, but of importance is the first total knee replacement surgery carried out in 1968 heralding the dawn of a new era in terms of progress on dealing with the problem affecting millions of people globally. The progress noted is related to techniques, surgical materials, and design of implants in efforts of increasing the effectiveness of knee replacement and in essence contributing to it being amongst the most successful surgery procedure across the globe. Pioneers in the industry include Leslie Gordon Percival Shiers, Leonard Marmor, Frank Gunston, and John Insall. The replacement of knees has been performed for over forty years with immeasurable rates of success recorded coupled with numerous challenges. Knee replacement has been identified to contribute to the relief of pain and improved functionality of the replacement. In other words, the history can be described as an innovative one witnessing immense improvements in design as well operation methods contributing to the extension of lifespan of the knee replacement as well as reduction in identified negative effects (Lloyd and Wainwright et al., 2012). The surgical process has witnessed numerous advancements since their introduction with rectifications on design flaws experienced in the early phases. The replacements had early flaws attributed to the artificial knee’s design flaws. The artificial knee can also be referred as prosthesis and has undergone modifications leading to the improvement of stability, increased motion, and enhanced durability with an estimated lifespan of twenty years. The evolution of knee replacement in terms of design has been tremendous, but indicates the room for further improvements to be pursued. Early flaws in the design to the prosthesis included some level of difficulty in loosening attributed to the cementing techniques applied. However, there has been marked improvements in cementing techniques, leg alignment, and instrumentation (Clyburn and Sheth, 2012). Literature review Hamelynck (2006) discusses the deep history related too total knee replacement outlining the different innovations shaping the surgery. The first exploration to knee arthroplasty can be traced to 1891 when Gluck made an ivory knee hinge. Further developments were made in 1960 through the introduction methyl methacrylate as a material for fixation. The next innovation was responsible for the introduction of polyethylene plastic of high density as the bearing surface. Changes in condylar knee design progressed in the 1970’s with inclusion of the single-piece component of the femur to cover the lateral and medial femoral condyles. This was enhanced by the use of tibia component single pieced used in the resurfacing of the lateral and medial plateaus. Additional changes included the use of PMMA in fixation. The evolution of total knee replacement (TKR) was faulted for the wear and mechanical loosening of the different designs used as knee replacements. According to Earnshaw (2001), the problem in design was firstly identified as the presence of incongruent surfaces. The surfaces allowed for unrestricted movements, minimal loosening, and increased contact stresses. The dilemma in designing knee replacements is linked the congruent surfaces allowing for lowered contact stresses in addition to restricted movements linked to the maximal loosening. The introduction of new knees progressed in the 198s and 1990s with knees such as the LCS mobile knee, PCA knee system, AGC knee system, Miller-Galante, and PFC Sigma total knees. The article identifies the minimal progress recorded in the 90s in relation to new inventions with many developments involving innovations that changed the design of different prosthesis. Major issues identified include the use of cement in fixation, wear and tear of polyethylene, use of mobile or fixed bearings, replacement off patella, and the instability experienced with the use of replaced knees. Brugioni (2004) discusses issues pertaining to intensive knee designs for increased flexion in relation to gender. Surgeons and manufacturers are engaged in continued efforts of addressing issues related to the improvement of implant designs. Trends in designing implants have tilted to include several gender specific designs to meet diversified needs. The gender specific designs incorporate elements that contribute to high flexion. This follows established differences between female and male bones and thus the differences are addressed through specified designs. Gender specific knees vary in size in comparison to the standard knee implants used. The knee implants have been developed in narrower forms with reduced widths for fitting bones of specific patients achieving better fitting than standard knee implants. Kalairajah, Simpson, Cossey, Verrall, and Spriggins, (2005) discuss the changes in implant designs against the backdrop of changes in level of technology influencing surgery procedures. Improvements in the design of implants can be linked to the increased use of technology in surgery such as the development of computer-assisted surgery. The use of navigation systems with computerization has been of immense help in the replacement of knees. The use of the systems has not yet been widely adopted even though it works well with the new developments in design improvement. However, the use of computer-assisted surgery has been faced with criticism owing to increased surgical times, and fracturing at the holes used in the bone. Moskowitz (2007) explains the knee as comprising of three parts referred as compartments. The three parts include the region between the thighbone and kneecap, the shin bone in the inside and the thigh bone, and the shin bone in the outside and the thigh bone. The parts are referred as patellofemoral, medial, and lateral compartments respectively. During the total knee replacement, the three different compartments of the knee are replaced and this can be attributed to majority of patients who have problems spreading in two or the three compartments. This demands the use of total knee replacement as the mode of treatment and thus relies on design features coupled with the surgical procedure and care taken after surgery. The procedure of total knee replacement demands the removal of the cruciate ligament (anterior) depending on the design of the implant. Majority of implant designs provide for the preservation of the cruciate ligament (posterior) using the design for the provision of ligament stability. This supports the argument for improved normal motion and ease in correction of identified deformities. Lloyd, Wainwright, and Middleton (2012) discuss the issue of minimally invasive surgery, mobile bearing, and fixed bearing designs. Majority of the total knee implants incorporate the fixed bearing design in which the implant is attached to the bone. The implant in this instance does not act independently in terms of movement. This is contrary to the mobile bearing design where the plastic placed between the tibial and femoral components has free rotation when the knee is in motion. The use of the mobile bearing design in TKA is essential in the reduction of the stress experienced between the shin bone and the implant. This leads to reduction in the rate of failure and wear with the designs experiencing numerous innovations incorporating improvements. The use of design is an important feature of minimally invasive surgery where smaller incisions than conventional incisions are used in knee replacement. The use of minimally invasive surgery is important in the production of a cosmetic scar, speedy recovery, and reduction of pain. The use of this type of surgery works best with slimmer patients and optimizes the use of improved implant designs. Bhandari and Adili (2011) discuss the advancements made in knee replacements owing to improvements in surgical methods, materials, and design of the implant. In relation to material improvements, the paper considers the use of metal prosthesis on metal as well as the new polyethylene, and the plastic joints. The use of metal on metal has not been an entirely new concept because it had been applied to hip replacement. The use of metal in design has been aided by the use of smoother harder metal on articulating surfaces. The use of ceramic has come of age providing a perfect alternative for the bearing surface and aiding in the reduction of wear. Improvements in design have witnessed the improvement of mobile bearing implants that can be attributed to improvements in metallurgy and plastic. New designs provide implants that increase flexion while providing longer lasting implants. Improvements in design have led to the development of implants coated with a rough porous surface from fiber metal or metal beads. The surface is crucial in the provision of growth surfaces for bones into the implant allowing for increased stability without the use of bonding. Buechel and Pappas (2011) attribute the need for total knee replacement on arthritis with majority of the chronic pain of the knee being linked to three types of arthritis that include osteoarthritis, post-traumatic arthritis, and rheumatoid arthritis. Osteoarthritis is an arthritis type that is linked with age. Majority of the people contracting this disease are old and have delicate bones thus need for specially designed implants. The paper emphasizes on the need for new designs to incorporate the posterior cruciate ligament together with the range of flexion motion. Discussion The modern designs of prosthesis give flexibility in the use of bone cement with some design eliminating its use. The design of the metal parts of the replacement has some special coating on the surfaces aimed at allowing the bone’s direct growth. Marmor and Gunston contributed with designs used in unicompartmental operations although there were numerous setbacks relating to the lifetime of the knee replacement. However, progress into the age of new design can be attributed to the Condylar design fronted by Insall. Gunston’s design incorporated the use of stainless steel circular runner alongside a polyethylene track. Later progress in the 1990’s witnessed the introduction of a mobile-bearing knee replacement form. The mobile-bearing replacement provided complete congruency on the surface aimed at minimizing previous creep and wear attributed to earlier versions of knee replacement. The design increased the freedom of movement enjoyed by a patient using the mobile-bearing design. The rate of innovations are poised to ensure marked improvement on the total knee replacement procedure owing to better designs with longer lifespan and increased flexion. The new developments witnessed in total knee replacement designs increase the flexion ranges enjoyed by patients following the surgery. The improved flexion ranges enjoyed with the development of new designs range between one hundred and twenty to one hundred and fifty-five degrees. These improvements should be angled towards the reduction of tension emanating from the extensor mechanism. All improvements in design should be accompanied by improvements in the surgical techniques as well as well-regulated post-operative rehabilitation. The three factors work in tow for the improvement of flexion (Buechel and Pappas, 2011). Design issues are complex and differ from one implant manufacturer to the other and according to specifications for particular surgery. Implant manufacturers influence the design in accordance with the different techniques and instrumentation used with lack of consensus on the best and common procedure to be employed. However, there is some significant level of agreement pertaining to the use of un cemented and cemented components with differences emerging on the need for resurfacing of the patella. The retention of the posterior cruciate ligament accrues benefits to patients tilting designs towards its retention. On the other hand, other designs advocate for the removal of the posterior cruciate ligament in attempts of reducing the maximal force exerted on the knee. The removal of the PCL leads to patients leaning forward when climbing for maximization of force applied on quadriceps. The mobile bearing is suitable for the provision of some level of complete congruency that is unique to the articulate surface for accommodating preferred motion patterns from the remaining natural compartment of the knee. The replacement surgery involves the cutting away of an arthritic bone with the knee joint being filled with the prosthetic joint. Total knee replacement is responsible for the removal of all arthritic surfaces including the tibia, patella, and femur. The ends of the knee bone are inserted with prosthesis similar to the capping of teeth. Majority of the prosthetics are made of plastic and metallic surfaces with a special design enabling them to glide over each other with ease. This aspect of the knee replacement is important and underlines the importance of design in the functionality of the prosthesis. The design of the prosthesis should ensure optimization of kinematics with features ranging from femoral aspects having small radii in the curvature of sagittal and frontal planes alongside a lateral condoyle with larger radii in its curvature (Lloyd and Wainwright et al., 2012). The change in design is expected to increase the flexion range providing a motion of up to 160 degrees. The designs featured in knee replacement surgery have notable kinematic abnormalities that include the reduction of rollback, reversal in axial rotations, translation occurrence in a paradoxical manner, and the condylar liftoff. The knee design has to take into consideration the multi radius design and the anatomic radius design (Brugioni and Falkel, 2004). The motion of a natural knee has been identified to occur at a constant radius, which is centered at an axis known as transepicondylar. The design of the knee implant should be a replication of the kinematics and motion of a natural knee. This places immense need for the knee replacement design to incorporate the constant radius of motion from a natural knee as opposed to the use of an instantaneous center. The instantaneous center allows for the change in the center of the knee in movements from extension to flexion. Changes in the rotation center are connected to mid-flexion instability. The adoption of single radius designs can aid in decreasing the knee pain experienced in the anterior side, chair rise, and increased flexion gain (Bhandari and Adili, 2011). Conclusion Total knee replacement is important in the relief of pain as well as regaining of motion and higher flexion by patients. The field has experienced numerous innovations pertaining to the design of knee implants and this is important in the provision of a lasting solution. However, the progress achieved in improvements related to the knee design is not enough with increased need for designs that provide patients with optimal qualities. The development of implant designs should consider the renewal of motion and backside function (Bhandari and Adili, 2011). This is achievable through a design that focusing on the back of the implant by flaring the posterior condyles of the femur. Secondly, new designs should consider renewal of motion and gain in functionality. Wear and tear is an important component that should be incorporated in design to ensure longer lasting implants than those developed lasting a lifespan of twenty years (R\"As\"Anen and Paavolainen et al., 2007). The final aspect that requires improvement in relation to knee replacement concentrates on component sizing. The provision of new designs should ensure presence of appropriate implants in terms of size for optimized flexion. Reference List Bhandari, M. and Adili, A. 2011. Evidence-based orthopedics. Chichester, West Sussex, UK: Wiley-Blackwell. Brugioni, D. J. and Falkel, J. E. 2004. Total knee replacement and rehabilitation. Alameda, CA: Hunter House. Buechel, F. and Pappas, M. J. 2011. Principles of human joint replacement. Berlin: Springer. Clyburn, T. A. and Sheth, D. 2012. Total Knee Replacement. UT Physician Referral Service, 1-888 (4UT DOC), pp. 1-18. Earnshaw, P. 2001. Controversies in total knee replacement. Edited by Richard S. Laskin. Pp 400. Oxford: Oxford University Press, 2001. ISBN: 0-19-263072-5. $129.00. Journal of Bone & Joint Surgery, British Volume, 83 (7), pp. 1087--1088. Hamelynck, K. J. 2006. The history of mobile-bearing total knee replacement systems. Orthopedics, 29 (9 Suppl), pp. 7--12. Kalairajah, Y., Simpson, D., Cossey, A., Verrall, G. M. and Spriggins, A. J. 2005. Blood loss after total knee replacement EFFECTS OF COMPUTER-ASSISTED SURGERY. Journal of Bone & Joint Surgery, British Volume, 87 (11), pp. 1480--1482. Lloyd, J., Wainwright, T. and Middleton, R. 2012. What is the role of minimally invasive surgery in a fast track hip and knee replacement pathway?. Annals of the Royal College of Surgeons of England, 94 (3), pp. 148--151. Moskowitz, R. W. 2007. Osteoarthritis. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. R"As"Anen, P., Paavolainen, P., Sintonen, H., Koivisto, A., Blom, M., Ryyn"Anen, O. and Roine, R. P. 2007. Effectiveness of hip or knee replacement surgery in terms of quality-adjusted life years and costs. Acta Orthopaedica, 78 (1), pp. 108--115. Read More