Basic Study
Copyright ©The Author(s) 2018. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Jun 18, 2018; 9(6): 85-91
Published online Jun 18, 2018. doi: 10.5312/wjo.v9.i6.85
Comparison of a simplified skin pointer device compared with a skeletal marker for knee rotation laxity: A cadaveric study using a rotation-meter
Ken Lee Puah, Andy Khye Soon Yew, Siaw Meng Chou, Denny Tijauw Tjoen Lie
Ken Lee Puah, Andy Khye Soon Yew, Denny Tijauw Tjoen Lie, Department of Orthopaedic Surgery, Singapore General Hospital, Singapore General Hospital, Singapore 169608, Singapore
Siaw Meng Chou, School of Mechanical and Aerospace Engineering, College of Engineering, Nanyang Technological University, Singapore 639798, Singapore
Author contributions: Puah KL performed the experiment, analysis and wrote the manuscript; Yew AKS designed and performed the experiment and edited the manuscript; Chou SM designed the experiment, obtained funding and edited the manuscript; Lie DTT designed the experiment, obtained funding and edited the manuscript.
Conflict-of-interest statement: No potential conflicts of interest relevant to this article were reported.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Dr. Ken Lee Puah, FRCS (Ed), Surgeon, Department of Orthopaedic Surgery, Singapore General Hospital, Outram Road, Singapore 169608, Singapore. puah.ken.lee@singhealth.com.sg
Telephone: +65-63214603 Fax: +65-62248100
Received: January 11, 2018
Peer-review started: January 11, 2018
First decision: February 9, 2018
Revised: March 16, 2018
Accepted: May 13, 2018
Article in press: May 13, 2018
Published online: June 18, 2018
Processing time: 155 Days and 1.1 Hours
ARTICLE HIGHLIGHTS
Research background

With double-bundle and anatomical single-bundle anterior cruciate ligament reconstruction for restoration of rotational knee kinematics, the need for objective clinical measurement of knee rotational laxity arises. Evaluation of knee rotation remains a challenge with intra-observer variability in the pivot shift test.

Research motivation

We aim to compare a non-invasive skin pointer with a knee rotation jig in cadaveric knees against a skeletally mounted marker.

Research methods

Six pairs of cadaveric legs were mounted on a knee rotation jig. One Kirscher wire was driven into the tibial tubercle as a bone marker and a skin pointer was attached. Rotational forces of 3, 6 and 9 nm applied at 0°, 30°, 45°, 60° and 90° of knee flexion. Results were analysed using the Pearson correlation coefficient and paired t-test.

Research results

Total rotation recorded with the skin pointer significantly correlated with the bone marker at 3 nm at 0° (skin pointer 23.9 ± 26.0° vs bone marker 16.3 ± 17.3°, r = 0.92; P = 0.0), 30° (41.7 ± 15.5° vs 33.1 ± 14.7°, r = 0.63; P = 0.037), 45° (49.0 ± 17.0° vs 40.3 ± 11.2°, r = 0.81; P = 0.002), 60° (45.7 ± 17.5° vs 34.7 ± 9.5°, r = 0.86; P = 0.001) and 90° (29.2 ± 10.9° vs 21.2 ± 6.8°, r = 0.69; P = 0.019) of knee flexion and 6 nm at 0° (51.1 ± 37.7° vs 38.6 ± 30.1°, r = 0.90; P = 0.0), 30° (64.6 ± 21.6° vs 54.3 ± 15.1°, r = 0.73; P = 0.011), 45° (67.7 ± 20.6° vs 55.5 ± 9.5°, r = 0.65; P = 0.029), 60° (62.9 ± 22.4° vs 45.8 ± 13.1°, r = 0.65; P = 0.031) and 90° (43.6 ± 17.6° vs 31.0 ± 6.3°, r = 0.62; P = 0.043) of knee flexion and at 9 nm at 0° (69.7 ± 40.0° vs 55.6 ± 30.6°, r = 0.86; P = 0.001) and 60° (74.5 ± 27.6° vs 57.1 ± 11.5°, r = 0.77; P = 0.006). No statistically significant correlation with 9 nm at 30° (79.2 ± 25.1° vs 66.9 ± 15.4°, r = 0.59; P = 0.055), 45° (80.7 ± 24.7° vs 65.5 ± 11.2°, r = 0.51; P = 0.11) and 90° (54.7 ± 21.1° vs 39.4 ± 8.2°, r = 0.55; P = 0.079). We recognize that 9 nm of torque may be not tolerated in vivo due to pain.

Research conclusions

We have measured knee rotation on a cadaveric knee utilising a knee rotation jig paired with a skin pointer against that of a skeletally mounted bone marker and have found a significant correlation between the two methods for the same magnitude of torque and knee flexion. We recognise that the use of the skin pointer introduces error due to movement of the soft tissue which increases with increasing torque.

Research perspectives

Our aim is to eventually develop a portable and user-friendly device which can be used for objective measurement of knee rotation laxity in a non-invasive manner. This may entail the use of accelerometers or robotic arms to measure kinematics.