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Computer-assisted TKAs yield better outcomes

By Peter Pollack

Computer-assisted navigation may result in better outcomes than standard instrumentation methods for total knee arthroplasty (TKA) patients, according to the authors. John M. Dillon, MRCS, presented the results of “Functional outcome assessment after navigated and standard TKA using gait analysis” at the 2009 AAOS Annual Meeting.

The research team conducted a prospective, controlled study of 54 patients based on gait analysis. Standard instrumentation was used for TKA in 20 patients (9 men, 11 women; mean age 66.3 years); 20 patients (8 men, 12 women; mean age 67.2 years) had TKAs performed using a computer-assisted navigation system; and 14 patients with no history of knee pathology, knee surgery, or gait abnormality acted as controls.

All patients in the two TKA groups were given the same implant.

Analyzing everyday motions
The authors recorded real-time motion using an 8-camera motion analysis system (Vicon, Oxford, UK) to assess the following functional activities: walking, rising from a chair, sitting, and ascending/descending stairs. They performed gait analysis at an average of 8 months (range: 6-14 months) postoperatively.

The researchers found that, while walking, TKA patients who had standard instrumentation had a longer double-stance support time (mean 17 percent of the gait cycle) than patients in the navigated group (mean 15.5 percent of the gait cycle). However, other outcome measures—including biphasic moment pattern, adduction moment, and maximum flexion angle—were better in patients who had computer-assisted TKA surgery.

Additionally, patients who had computer-assisted TKA fared better in chair sitting and rising, stair ascent, and stair descent.

Dr. Dillon pointed out that range of motion among both navigated and standard groups was lower than the control group. He also noted that the presence of a biphasic moment pattern has been shown to be a reliable finding in normal subjects, and the navigated group had a higher proportion of patients with that finding than the standard group.

Compared to TKA performed using standard instrumentation, TKA performed with computer-assisted navigation achieved an overall improvement in dynamic functional knee outcomes.

Dr. Dillon’s coauthors include Jon V. Clarke, MRCS; Alexander C. Nicol, MD; Frederic Picard, MD; Alberto Gregori, FRCS; and Andrew Kinninmonth, FRCS. The authors report the following disclosures: Drs. Dillon and Nicol—none; Dr. Clarke—B. Braun Aesculap, ConvaTec; Dr. Picard— B. Braun Aesculap, Stryker; Dr. Gregori—B. Braun Aesculap, Biomet; Dr. Kinnenmonth—Stryker, B. Braun.

Peter Pollack is a staff writer for AAOS Now. He can be reached at ppollack@aaos.org

AAOS Now
April 2009 Issue
http://www.aaos.org/news/aaosnow/apr09/clinical6.asp