Estimation of Tendon Moment Arms from Three-Dimensional Magnetic Resonance Images

AbstractNew three-dimensional (3D) magnetic resonance imaging (MRI) methods for measuring the tendon moment arm were created and were evaluated on the tendon moment arm of the flexor digitorum profundus at the third metacarpophalangeal joint. Using an open magnet MRI system and a hand holder, a series of static images were acquired at four joint angles and analyzed using specially created computer programs. Three methods were evaluated: (1) a 3D tendon excursion method that extended the method of Landsmeer; (2) a 3D geometric method whereby the moment arm was the perpendicular distance between the joint axis of rotation and the tendon path, and (3) a two-dimensional (2D) geometric method whereby single image slices were analyzed. Repeating the imaging and measurement processes, the 3D tendon excursion method was more reproducible (6% variation) than the 3D geometric method (12%), and both were much more reproducible than the 2D geometric method (27%). By having three operators analyze a single set of image data, we found that the precision of the 3D tendon excursion method was much less affected by segmentation error than the 3D geometric method. With the 3D imaging methods, tendon bowstringing and a displacement of the joint center of rotation toward the dorsal side of the hand were evident, leading to as much as a 60% increase in moment arm with joint flexion. Because of the dependence on flexion and variation between subjects, we recommend patient-specific measurements for target applications in functional neuromuscular stimulation interventions and tendon transfer surgery. © 1999 Biomedical Engineering Society. PAC99: 8761Pk, 8719Rr, 0705Pj

[1]  P. Crago,et al.  A dynamic model for simulating movements of the elbow, forearm, an wrist. , 1996, Journal of biomechanics.

[2]  P. Brand,et al.  Tendon and pulleys at the metacarpophalangeal joint of a finger. , 1975, The Journal of bone and joint surgery. American volume.

[3]  J. Landsmeer.  Studies in the anatomy of articulation. I. The equilibrium of the "intercalated" bone. , 1961, Acta morphologica Neerlando-Scandinavica.

[4]  A Huson,et al.  Estimation of instantaneous moment arms of lower-leg muscles. , 1990, Journal of biomechanics.

[5]  G. Smidt.  Biomechanical analysis of knee flexion and extension. , 1973, Journal of biomechanics.

[6]  D B Chaffin,et al.  An investigation of the relationship between displacements of the finger and wrist joints and the extrinsic finger flexor tendons. , 1978, Journal of biomechanics.

[7]  C. Spoor,et al.  Knee muscle moment arms from MRI and from tendon travel. , 1992, Journal of biomechanics.

[8]  D. Thompson,et al.  A clinical study of forces generated by the intrinsic muscles of the index finger and the extrinsic flexor and extensor muscles of the hand. , 1978, The Journal of hand surgery.

[9]  K. An,et al.  Tendon excursion and moment arm of index finger muscles. , 1983, Journal of biomechanics.

[10]  S. Erickson,et al.  The "magic angle" effect: background physics and clinical relevance. , 1993, Radiology.

[11]  Jayaram K. Udupa,et al.  Registration of 3D objects and surfaces , 1990, IEEE Computer Graphics and Applications.

[12]  R. Gregor,et al.  In vivo moment arm calculations at the ankle using magnetic resonance imaging (MRI). , 1990, Journal of biomechanics.

[13]  G Németh,et al.  In vivo moment arm lengths for hip extensor muscles at different angles of hip flexion. , 1985, Journal of biomechanics.

[14]  C. Spoor,et al.  Rigid body motion calculated from spatial co-ordinates of markers. , 1980, Journal of biomechanics.

[15]  Supun Samarasekera,et al.  Joint kinematics via three-dimensional MR imaging , 1992, Other Conferences.

[16]  T S Buchanan,et al.  Estimation of muscle forces about the wrist joint during isometric tasks using an EMG coefficient method. , 1993, Journal of biomechanics.