Failure mechanisms in total knee arthroplasty

Abstract

Executive Summary Total Knee Arthroplasty (TKA) has become a well - established treatment modality for surgical correction of knee disorders and pain generated by arthritis and other disorders such as trauma . Today a patient can expect to rely on his new knee to serve him with comfort for a fair number of years if not his entire life . TKA has taken on a predicated level of confidence and certain trends have developed over the years . Success has increased demand and the health care system is challenged to meet current and growing demand for surgery [ In fact the epidemiological studies have predicted that hips will grow only a little whereas knees are projected to have a 6 - fold increase - see Kutz AAOS Scientific Exhibit 2006 ] . Surgical techniques are specializing into specific indications or camps for specialized product features . Uni - compartmental , Bi - compartmental , Total Knee with and without replacement of the patella , along with Patella - femoral replacement are some of the product classifications now available . The near future is now with articular focal defect replacement . New materials and techniques will open this area to increased indications as the sport - medicine surgeon finds his way into this growing surgical market . This review is being drafted as a quick narrative summary and is not meant to be a comprehensive review on the subject . The combined experience of the two authors totals over eighty years in the field of total joint surgery and we feel reasonably confident in our expressed opinions . First and foremost , all surgery is dependent on surgical technique . Technique is more important than material and design . Poor technique places an increased burden on design and materials , and improved materials and designs can ease the burden on surgical technique but never replace the overall benefit of good technique . The clinical assessments (in - vivo ; ex - vivo) for wear ranged 50 - 400 mm 3 / year for either ' backside ' wear or ' overall ' knee wear (RSA and retrievals) . These values were at least as high if not higher than for total hip replacements . Note that there is no data for ' frontside ' knee wear by itself . Clearly there is little known from such ' dimensional ' studies of how much change was due to creep or plastic flow as distinct from wear . Wear estimates for laboratory knee studies fell in the narrow range of 3 - 10 mm 3 / year . Clearly these were at least an order of magnitude less than that reported from clinical studies . Interestingly there has been no insight given as to why such a discrepancy exits in the wear testing literature . However , since these are generally gravimetric wear assessments we believe that they do represent true wear . Whether it is physiologically correct is another question . We excluded two simulator wear rates from discussion . One by an Italian group produced a wear rate of 24mm 3 / Mc with no explanation . One by an American group added hyaluronic acid to the lubricant and obtained wear rates of 64mm 3 / Mc . While they may have been on to something the observed changes were so profound and not yet confirmed by any other study such that some caution is justified here .