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Mayr HO, Rosenstiel N, Prakash KS, Comella LM, Woias P, Schmal H, Seidenstuecker M. Internal Rotation Measurement of the Knee with Polymer-Based Capacitive Strain Gauges versus Mechanical Rotation Measurement Taking Gender Differences into Account: A Comparative Analysis. Life (Basel) 2024; 14:142. [PMID: 38276271 PMCID: PMC10821048 DOI: 10.3390/life14010142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 01/02/2024] [Accepted: 01/16/2024] [Indexed: 01/27/2024] Open
Abstract
With the conventional mechanical rotation measurement of joints, only static measurements are possible with the patient at rest. In the future, it would be interesting to carry out dynamic rotation measurements, for example, when walking or participating in sports. Therefore, a measurement method with an elastic polymer-based capacitive measuring system was developed and validated. In our system, the measurement setup was comprised of a capacitive strain gauge made from a polymer, which was connected to a flexible printed circuit board. The electronics integrated into the printed circuit board allowed data acquisition and transmission. As the sensor strip was elongated, it caused a change in the spacing between the strain gauge's electrodes, leading to a modification in capacitance. Consequently, this alteration in capacitance enabled the measurement of strain. The measurement system was affixed to the knee by adhering the sensor to the skin in alignment with the anterolateral ligament (ALL), allowing the lower part of the sensor (made of silicone) and the circuit board to be in direct contact with the knee's surface. It is important to note that the sensor should be attached without any prior stretching. To validate the system, an in vivo test was conducted on 10 healthy volunteers. The dorsiflexion of the ankle was set at 2 Nm using a torque meter to eliminate any rotational laxity in the ankle. A strain gauge sensor was affixed to the Gerdii's tubercle along the course of the anterolateral ligament, just beneath the lateral epicondyle of the thigh. In three successive measurements, the internal rotation of the foot and, consequently, the lower leg was quantified with a 2 Nm torque. The alteration in the stretch mark's length was then compared to the measured internal rotation angle using the static measuring device. A statistically significant difference between genders emerged in the internal rotation range of the knee (p = 0.003), with female participants displaying a greater range of rotation compared to their male counterparts. The polymer-based capacitive strain gauge exhibited consistent linearity across all measurements, remaining within the sensor's initial 20% strain range. The comparison between length change and the knee's internal rotation angle revealed a positive correlation (r = 1, p < 0.01). The current study shows that elastic polymer-based capacitive strain gauges are a reliable instrument for the internal rotation measurement of the knee. This will allow dynamic measurements in the future under many different settings. In addition, significant gender differences in the internal rotation angle were seen.
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Affiliation(s)
- Hermann O. Mayr
- G.E.R.N. Tissue Replacement, Regeneration & Neogenesis, Department of Orthopedics and Trauma Surgery, Medical Center-Albert-Ludwigs-University of Freiburg, Faculty of Medicine, Albert-Ludwigs-University of Freiburg, Engesser Straße 4, 79108 Freiburg, Germany; (H.O.M.); (N.R.)
- Department of Orthopedics and Trauma Surgery, Medical Center Albert-Ludwigs-University of Freiburg, Faculty of Medicine, Albert-Ludwigs-University of Freiburg, Hugstetter Str. 55, 79106 Freiburg, Germany;
| | - Nikolaus Rosenstiel
- G.E.R.N. Tissue Replacement, Regeneration & Neogenesis, Department of Orthopedics and Trauma Surgery, Medical Center-Albert-Ludwigs-University of Freiburg, Faculty of Medicine, Albert-Ludwigs-University of Freiburg, Engesser Straße 4, 79108 Freiburg, Germany; (H.O.M.); (N.R.)
- Kreiskrankenhaus Lörrach, Spitalstraße 25, 79539 Lörrach, Germany
| | - Karthika S. Prakash
- Department of Microsystems Engineering, IMTEK Albert-Ludwigs-University of Freiburg, Geoges-Koehler-Allee 102, 79110 Freiburg, Germany; (K.S.P.); (L.M.C.); (P.W.)
| | - Laura Maria Comella
- Department of Microsystems Engineering, IMTEK Albert-Ludwigs-University of Freiburg, Geoges-Koehler-Allee 102, 79110 Freiburg, Germany; (K.S.P.); (L.M.C.); (P.W.)
- Institute for Applied Research (IAF), Karlsruhe University of Applied Sciences (HKA), Moltkestraße 30, 76133 Karlsruhe, Germany
| | - Peter Woias
- Department of Microsystems Engineering, IMTEK Albert-Ludwigs-University of Freiburg, Geoges-Koehler-Allee 102, 79110 Freiburg, Germany; (K.S.P.); (L.M.C.); (P.W.)
| | - Hagen Schmal
- Department of Orthopedics and Trauma Surgery, Medical Center Albert-Ludwigs-University of Freiburg, Faculty of Medicine, Albert-Ludwigs-University of Freiburg, Hugstetter Str. 55, 79106 Freiburg, Germany;
| | - Michael Seidenstuecker
- G.E.R.N. Tissue Replacement, Regeneration & Neogenesis, Department of Orthopedics and Trauma Surgery, Medical Center-Albert-Ludwigs-University of Freiburg, Faculty of Medicine, Albert-Ludwigs-University of Freiburg, Engesser Straße 4, 79108 Freiburg, Germany; (H.O.M.); (N.R.)
- Department of Orthopedics and Trauma Surgery, Medical Center Albert-Ludwigs-University of Freiburg, Faculty of Medicine, Albert-Ludwigs-University of Freiburg, Hugstetter Str. 55, 79106 Freiburg, Germany;
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Mayr HO, Rosenstiel N, Prakash KS, Comella LM, Woias P, Schmal H, Seidenstuecker M. Digital measurement of anterolateral knee laxity using strain sensors. Arch Orthop Trauma Surg 2023; 143:6719-6729. [PMID: 37592159 PMCID: PMC10542724 DOI: 10.1007/s00402-023-05024-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Accepted: 08/04/2023] [Indexed: 08/19/2023]
Abstract
PURPOSE The ambition of the research group was to develop a sensor-based system that allowed the transfer of results with strain sensors applied to the knee joint. This system was to be validated in comparison to the current static mechanical measurement system. For this purpose, the internal rotation laxity of the knee joint was measured, as it is relevant for anterolateral knee laxity and anterior cruciate ligament (ACL) injury. METHODS This is a noninvasive measurement method using strain sensors which are applied to the skin in the course of the anterolateral ligament. The subjects were placed in supine position. First the left and then the right leg were clinically examined sequentially and documented by means of an examination form. 11 subjects aged 21 to 45 years, 5 women and 6 men were examined. Internal rotation of the lower leg was performed with a torque of 2 Nm at a knee flexion angle of 30°. RESULTS Comparison of correlation between length change and internal knee rotation angle showed a strong positive correlation (r = 1, p < 0.01). Whereas females showed a significant higher laxity vs. males (p = 0.003). CONCLUSIONS The present study showed that the capacitive strain sensors can be used for reproducible measurement of anterolateral knee laxity. In contrast to the previous static systems, a dynamic measurement will be possible by this method in the future.
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Affiliation(s)
- Hermann O Mayr
- Department of Orthopedic and Trauma Surgery, Faculty of Medicine, Medical Center-University of Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany.
| | - Nikolaus Rosenstiel
- Department of Orthopedic and Trauma Surgery, Faculty of Medicine, Medical Center-University of Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany
| | - Karthika S Prakash
- Department of Microsystems Engineering IMTEK, Albert-Ludwigs-University of Freiburg, Georges-Koehler-Allee 103, 79110, Freiburg, Germany
| | - Laura M Comella
- Department of Microsystems Engineering IMTEK, Albert-Ludwigs-University of Freiburg, Georges-Koehler-Allee 103, 79110, Freiburg, Germany
| | - Peter Woias
- Department of Microsystems Engineering IMTEK, Albert-Ludwigs-University of Freiburg, Georges-Koehler-Allee 103, 79110, Freiburg, Germany
| | - Hagen Schmal
- Department of Orthopedic and Trauma Surgery, Faculty of Medicine, Medical Center-University of Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany
| | - Michael Seidenstuecker
- G.E.R.N. Center of Tissue Replacement, Regeneration & Neogenesis, Department of Orthopedics and Trauma Surgery, Faculty of Medicine, Medical Center-University of Freiburg, Albert-Ludwigs-University of Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany
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