Table 1 Summary of techniques to measure the dimensions and geometries of soft tissues and their clinical value
Technique | Papers | Advantages | Disadvantages | Clinical value |
|---|---|---|---|---|
Anthropomorphic correlations | • Simple • Fast | • Limited reliability • Inherent errors due to assumptions • Not truly patient-specific • Lack of quality physical measurements for comparison | Limited clinical usefulness due to assumptions and low reliability | |
Ruler | [76] | • Simple • Fast | • Unable to measure two- or three-dimensional geometry | Clinically useful due to simplicity |
Computed tomography (CT) | • Readily available diagnostic imaging technique • Non-contact • Non-invasive • Three-dimensional | • Poor discrimination of soft tissues • Radiation dose • Lack of quality physical measurements for comparison | Limited clinical usefulness due to poor discrimination of soft tissues | |
Computed tomography with contrast | • Improved differentiation of soft tissues • Non-contact • Non-invasive • Three-dimensional | • Limited to ex vivo evaluations • Potential deformation of tissue • Poor discrimination of soft tissues • Radiation dose | Limited clinical usefulness due to difficulty applying contrast agents | |
Magnetic resonance imaging (MRI) | [61, 62, 70,71,72,73,74,75,76,77,78,79,80,81,82,83,84, 137, 138] | • Readily available diagnostic imaging technique • Able to differentiate soft tissues • Image quality can be improved with digital post-processing • Safe • Non-contact • Non-invasive • Three-dimensional | • Expensive • Slow • Lack of robust methodologies • Conflicted reports of accuracy and reliability • May not adequately resolve paratenon • Lack of quality physical measurements for comparison | Clinically useful due to clear differentiation of soft tissues |
Ultrasound, 2D (2DUS) | [39, 45, 66, 73, 78, 79, 85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115] | • Readily available for diagnostic imaging technique • Safe • Fast • Non-invasive • Inexpensive • Able to differentiate soft tissues | • Two-dimensional • Conflicted reports of accuracy and reliability for deep tendons • Results dependent on operator, pressure, position, and orientation • Lack of quality physical measurements for comparison • Unable to detect paratenon • Requires contact | Clinically useful for superficial tendons |
Ultrasound, 3D (3DUS) | • Accurate • Reliable • Repeatable • Reduced operator-, position-, and orientation-dependency • Safe • Fast • Non-invasive • Three-dimensional • Able to differentiate soft tissues | • Unable to detect paratenon • Requires contact • Pressure dependency | High clinical usefulness for superficial tendons | |
Sectioning | • Accurate • Repeatable • Can be reconstructed to three-dimensional | • Destructive | Low clinical usefulness due to destructive nature | |
By estimation | [126] | • Simple • Fast | • Inherent errors due to shape assumptions • Does not capture geometry • Affected by measurement technique (e.g. ruler) | Clinically useful for comparative measurements |
Area micrometry | • Simple • Fast • Repeatable | • Underestimates area • Contact • Does not capture geometry | Clinically useful for comparative measurements | |
Casting | • Accurate • Reliable • Repeatable • Three-dimensional • Ability to revisit measurements | • Slow • Contact • Requires tissue to be isolated • Unable to visualise internal structures | Clinically useful for some tissues, particularly resected tissues | |
Shadow amplitude | [126] | • Accurate • Non-contact | • Poor repeatability • Unable to visualise internal structures | Limited clinical usefulness |
Laser micrometry | • Fast • High accuracy • Repeatable • Reliable • Non-contact • Two-dimensional | • Affected by specimen geometry, concavities, opacity, reflectivity, and orientation • Unable to visualise internal structures | Limited to external and ex vivo measurements | |
Laser scanning | [142] | • Fast • High accuracy • Repeatable • Reliable • Non-contact • Three-dimensional | • Affected by specimen geometry, concavities, surface refraction, alignment of sample, opacity, reflectivity, and orientation • Limited viewing window for three-dimensional reconstruction • Unable to visualise internal structures | Clinically useful for 3D surface measurements. Limited to external and ex vivo tissues |
Photogrammetry | [143] | • High accuracy • Repeatable • Reliable • Non-contact • Three-dimensional • Photorealistic reconstruction | • Affected by concavities • Unable to visualise internal structures | Clinically useful for 3D surface measurements. Limited to external and ex vivo tissues |
Structured white light (SWL) | • Fast • High accuracy • Repeatable • Reliable • Non-contact • Three-dimensional • Photorealistic reconstruction | • Affected by small concavities • Unable to visualise internal structures | Clinically useful for 3D surface measurements. Limited to external and ex vivo tissues | |
Digital image correlation (DIC) | • Fast • High accuracy • Repeatable • Reliable • Non-contact • Three-dimensional | • Requires sample preparation • Affected by small concavities • Unable to visualise internal structures | Clinically useful for 3D surface and strain measurements. Limited to external and ex vivo tissues |