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Research Papers

A Simple Goniometer for Use Intraoperatively in Total Knee Arthroplasty

[+] Author and Article Information
J. Peter

San Francisco Orthopaedic Residency Program,
The Taylor Collaboration,
St. Mary's Medical Center,
San Francisco, CA

J. M. Currey

Biomechanical Testing Facility,
University of California,
San Francisco, CA

J. M. Buckley

San Francisco Orthopaedic Residency Program,
The Taylor Collaboration,
St. Mary's Medical Center,
San Francisco, CA;
Biomechanical Testing Facility,
University of California,
San Francisco, CA

K. D. Liddle

Biomechanical Testing Facility, University of California, San Francisco, CA

Manuscript received April 17, 2012; final manuscript received October 12, 2012; published online February 13, 2013. Assoc. Editor: Hamid M. Lankarani.

J. Med. Devices 7(1), 011010 (Feb 13, 2013) (3 pages) Paper No: MED-12-1052; doi: 10.1115/1.4023289 History: Received April 17, 2012; Revised October 12, 2012

Intraoperative range of motion (ROM) assessment can be challenging during total knee arthroplasty (TKA) surgery. As computer assisted surgery is costly and not readily available to many surgeons, we have developed a simple, cost-effective intraoperative device to precisely measure knee flexion and extension. A simple knee goniometer system was constructed consisting of a digital level mounted to a base that rigidly attaches two standard needles. The needles are pushed through the overlying soft tissue of the distal femur. The device is then applied to the proximal tibia, where an angle measurement of the knee is registered. A validation study for this device was conducted on two pairs of intact cadaveric lower limbs at 0 deg, 10 deg, 15 deg, 20 deg, 25 deg, and 30 deg. Two orthopedic surgeons experienced with the system performed three measurements at each angle. Systematic error, defined as the goniometer reading at 0 deg flexion anatomically as determined by the navigation system, ranged from −9.1 deg to 3.0 deg, consistent for each operator on every case. Measurement error, defined as the variability in repeated, fixed angle measurements made with the goniometer, was 1.5 ± 1.0 deg across all surgeons, cases, and prescribed flexion angles. For both surgeons and all imposed flexion angles, measurement errors were below the 4 deg clinical threshold. The simple knee goniometer system generated accurate, repeatable measures of changes in flexion angle intraoperatively with measurement error comparable to errors obtained using the commercial navigation system (1 deg–2 deg). However, the knee goniometer is less complex, less time intensive, and less costly than currently available computer assistive devices. Taken together, our results are very promising for the continued development of this device.

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Figures

Grahic Jump Location
Fig. 1

(Left) Base of goniometer with detachable needles. (Right) Assessment of knee flexion angle through overlying soft tissue with digital level atop base.

Grahic Jump Location
Fig. 2

(Left) Experimental layout with intraoperative navigation system. (Right) Rigid attachment of navigation markers. Arrows indicate regions where the goniometer was applied.

Grahic Jump Location
Fig. 3

Measurement error for each surgeon by flexion angle compared to clinically accepted error of 4 deg. Error bars represent one standard deviation. *p < 0.05.

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