Elimination of Preoperative Flexion Contracture as a Contraindication for Unicompartmental Knee Arthroplasty.

Introduction: Unicompartmental knee arthroplasty (UKA) is an effective alternative to total knee arthroplasty (TKA) for the management of unicondylar osteoarthritis. Historical contraindications limit patients' eligibility for UKA. However, recent reports have suggested that some contraindications may not be absolute.

Is Outpatient Unicompartmental Knee Arthroplasty Safe to Perform at an Ambulatory Surgery Center? A Comparative Study of Early Post-Operative Complications.

Background: Unicompartmental knee arthroplasty (UKA) lends itself to the outpatient surgical setting. Prior literature has established a low rate of readmission and post-operative complications when performed in a hospital outpatient setting (HOP). To our knowledge, there have been no studies comparing complications of UKA performed at an ambulatory surgery center (ASC) and those in a HOP.

Patellar Cut and Composite Thickness: The Influence on Postoperative Motion and Complications in Total Knee Arthroplasty.

Background: Little data exist on the influence of patellar thickness on postoperative motion or complications after total knee arthroplasty (TKA). This study addresses the following questions: Is postoperative motion influenced by change in composite patellar thickness? Is change in patellar thickness associated with more complications? And do more complications occur in the knees with a patellar bone remnant (<12 mm) and a native patellar thickness <18 mm?

Methods: In total, 3655 TKAs were performed by 3 surgeons over a 28-year interval. All knees had caliper measurement of patellar thickness before the patellar cut, after implantation of the component and postoperative motion recorded in the database 1 or 2 years after TKA.

Mid-term survivorship of minimally invasive unicompartmental arthroplasty with a fixed-bearing implant: revision rate and mechanisms of failure.

Minimally invasive unicondylar arthroplasty (UKA) continues to gain popularity for the management of patients with degenerative arthritis limited to one compartment of the knee. In this study, we examine a series of 517 fixed-bearing, cemented unicompartmental knee components implanted in patients to manage degenerative arthritis in the medial compartment of their knee. All UKAs were performed at a single institution using the same fixed-bearing design.

The functional assessment test: a method of evaluating improvement in function after knee arthroplasty.

Questionnaires are marginally useful for objectively measuring function after knee arthroplasty. The Functional Assessment (FA) test is an easily administered, timed test of a person's ability to stand, walk and ascend/descend stairs that would be useful for quantifying a patient's function after knee arthroplasty. Four hundred forty-five individuals were included in the study: 313 without lower extremity arthritis or neurologic disease and 132 with advanced degenerative arthritis prior to knee arthroplasty.

Unicondylar arthroplasty in knees with deficient anterior cruciate ligaments.

Background: Historically, a functional ACL has been a prerequisite for patients undergoing unicondylar knee arthroplasty (UKA). However, this premise has not been rigorously tested.

Questions/purposes: We compared (1) the survivorship free from revision and (2) the failure mechanisms of UKAs in ACL-deficient knees and UKAs in ACL-intact knees performed over the same time interval.

Use of structural allograft in revision total knee arthroplasty in knees with severe tibial bone loss.

Background: Tibial bone loss is frequently encountered at the time of revision total knee arthroplasty, and the outcome of the revision often depends on the management of this bone deficiency. We examined the clinical and radiographic outcomes of a series of revision total knee arthroplasties in which a structural allograft had been used to reconstruct a tibial bone defect encountered at the time of the revision procedure.

Methods: From January 1985 through September 1999, one surgeon performed revision arthroplasty in forty-nine knees (forty-seven patients) with a severe tibial bone defect.

Wear and osteolysis around total knee arthroplasty.

Osteolysis induced by wear debris of ultra-high-molecular-weight polyethylene has emerged as a significant problem after total knee arthroplasty. The generation of polyethylene wear and the development of osteolysis around total knee arthroplasty are caused by a combination of patient, implant, and surgical factors. Activity level over time may be the most important patient factor affecting the loads placed on a total knee replacement, but it is the most difficult to manage.

Isolated revision of failed metal-backed patellar components: outcome with minimum 4-year follow-up.

Several reports document high failure rates of metal-backed patellar components, but few report the outcome of revising these components to all-polyethylene, cemented implants. At a mean 87.2-month follow-up, we describe a series of 36 patients (40 knees) who underwent isolated metal-backed patellar revision to a cemented, all-polyethylene patellar component.

Epidemiology of osteolysis: backside implant wear.

Osteolysis is an emerging problem in patients who undergo total hip arthroplasty and total knee arthroplasty (TKA). Before the introduction of modular components, osteolysis was not as prevalent in patients who underwent TKA. Although polyethylene wear and the generation of small-particle debris were linked to the presence of osteolysis in patients who have undergone total hip arthroplasty, the fatigue-type wear and larger wear particles often seen with TKA were not thought to invoke the cellular response that causes osteolysis.

Treatment of the unstable total knee arthroplasty.

Instability is one of the leading causes of clinical failure after total knee arthroplasty. Instability can be categorized according to three basic patterns: AP or flexion space instability, varus/valgus or extension space instability, and global instability. Surgical options for treating instability include polyethylene exchange of a modular component, revision to a more constrained component, or revision to a hinged component.

Synovial entrapment: a complication of posterior stabilized total knee arthroplasty.

Background: We observed a complication of posterior stabilized total knee arthroplasty involving hypertrophy of tissue proximal to the patella associated with pain during active knee extension from 90 degrees of flexion. The purpose of this paper was to describe synovial entrapment and to determine if design features of the prosthesis predispose patients to the complication.

Methods: Between April 1990 and June 1999, we performed 459 consecutive posterior stabilized primary total knee arthroplasties using three prosthetic designs with different femoral intercondylar geometries.

Rapid polyethylene failure of unicondylar tibial components sterilized with gamma irradiation in air and implanted after a long shelf life.

Background: The mechanical toughness of polyethylene that has been sterilized by gamma irradiation in air decreases after a long shelf life. The purpose of the present study is to report the high failure rate after unicondylar knee replacements performed with polyethylene bearings that had been sterilized with gamma irradiation in air and implanted after a shelf life of < or = 4.4 years.