Osteonecrosis, obesity relative contraindications UKA - Academy News at the 2007 AAOS Annual Meeting

Osteonecrosis, obesity relative contraindications for UKA

By Jennie McKee

Orthopaedic surgeons should consider both obesity and osteonecrosis as relative contraindications for unicompartmental knee arthroplasty (UKA), according to poster exhibit P130.

Recent advances in implant design and minimally invasive surgical techniques for UKA have led to improved clinical results, including excellent pain relief and restoration of knee function. Controversy over the effectiveness of this surgical procedure has led some orthopaedic surgeons to propose specific patient selection criteria to ensure positive short- and mid-term results. Althoughthere is some disagreement on the absolute and relative contraindications for UKA, researchers have found that obesity and osteonecrosis can be detrimental to implant survivorship.

Between January 1994 and October 2002, 79 patients (101 knees) received a cemented UKA with the Zimmer implant. The cohort consisted of 32 men and 47 women with a mean age of 84 years (range: 47-95 years old). Researchers followed patients for a mean of 11 years (range: 4-12 years) and evaluated them using the Knee Society clinical and radiographical rating system.

Implant survival at final follow-up was 92 percent; eight knees (6 female and 2 male) had been revised to total knee arthroplasty. Patients who received a revision had a mean age of 68 years (range: 55-81 years old), compared to the rest of the cohort, which had a mean age of 88 years.

Of the patients who needed revision surgery, four (50 percent) had avascular necrosis and four (50 percent) were obese, meaning they had a body mass index (BMI) greater than 30. Two patients exhibited advanced tibial polyethylene wear and progressive tibial radiolucencies. The lead researcher for poster exhibit P130 is Peter M. Bonutti, MD, of Effingham, Ill. Co-investigators include Thorsten M. Seyler, MD; David R. Marker, BS, and Michael A. Mont, MD, all of Baltimore, and Margot McMahon, RN, of Effingham, Ill. Drs. Bonutti and Mont serve as consultants to Stryker Howmedica.

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