Aus dem Veterinärwissenschaftlichen Department der Tierärztlichen Fakultät der Ludwig-Maximilians-Universität München Lehrstuhl für Anatomie, Histologie und Embryologie Vorstand: Prof. Dr. Dr. Fred Sinowatz Arbeit angefertigt unter der Leitung von Dr. Renate Weller, PhD, MRCVS The Anatomy and Function of the equine thoracolumbar Longissimus dorsi muscle Inaugural-Dissertation zur Erlangung der tiermedizinischen Doktorwürde der Tierärztlichen Fakultät der Ludwig-Maximilians-Universität München Vorgelegt von Christina Carla Annette von Scheven aus Düsseldorf München 2010 2 Gedruckt mit der Genehmigung der Tierärztlichen Fakultät der Ludwig-Maximilians-Universität München Dekan: Univ.-Prof. Dr. Joachim Braun Berichterstatter: Priv.-Doz. Dr. Johann Maierl Korreferentin: Priv.-Doz. Dr. Bettina Wollanke Tag der Promotion: 24. Juli 2010 3 Für meine Familie 4 Table of Contents I. Introduction................................................................................................................ 8 II. Literature review...................................................................................................... 10 II.1 Macroscopic anatomy ............................................................................................. 10 II.1.1 Comparative evolution of the body axis ............................................................ 10 II.1.2 Axis of the equine body ..................................................................................... 12 II.1.2.1 Vertebral column of the horse..................................................................... 12 II.1.2.2 Axial musculature ....................................................................................... 16 II.1.2.3 Spinal ligaments.......................................................................................... 17 II.1.2.4 Function of the body axis of the horse........................................................ 18 II.2 Microscopic anatomy .............................................................................................. 28 II.2.1 Skeletal muscle morphology .............................................................................. 29 II.2.1.1 The Sarcomere ............................................................................................ 29 II.2.1.2 Neuromuscular control................................................................................ 30 II.2.2 Structural arrangement of skeletal muscle ......................................................... 31 II.2.2.1 Muscle architecture..................................................................................... 32 II.2.2.2 Muscle architectural parameter................................................................... 33 II.3 Muscle function and mechanics .............................................................................. 36 II.3.1 Types of muscle contraction .............................................................................. 36 II.3.2 Force-length relationship.................................................................................... 36 II.3.3 Force-velocity relationship................................................................................. 37 II.4 Pathological changes of the equine back................................................................. 37 II.4.1 Aetiopathogenesis and clinical signs.................................................................. 38 II.4.2 Diagnostic methods ............................................................................................ 42 II.4.2.1 Clinical examination ................................................................................... 42 II.4.2.2 Diagnostic imaging ..................................................................................... 43 III. Own investigations: Novel insights into the anatomy and function of the equine thoracolumbar Longissimus dorsi muscle................................................................................ 47 III.1 Gross anatomy of the equine thoracolumbar Longissimus dorsi muscle................ 47 III.1.1 Introduction ........................................................................................................ 47 III.1.2 Material and Methods......................................................................................... 48 III.1.2.1 Subjects....................................................................................................... 48 III.1.2.2 Experimental protocol................................................................................. 48 III.1.2.3 Statistical analysis....................................................................................... 51 III.1.3 Results ................................................................................................................ 51 III.1.3.1 Descriptive Anatomy .................................................................................. 51 5 III.1.3.2 Architectural measurements........................................................................ 59 III.1.4 Discussion and Conclusion ................................................................................ 76 III.1.4.1 Structure and Function................................................................................ 76 III.1.4.2 Conclusion .................................................................................................. 79 III.2 Muscle activity of the equine thoracolumbar Longissimus dorsi muscle during locomotion .............................................................................................................. 81 III.2.1 Introduction ........................................................................................................ 81 III.2.2 Material and Methods......................................................................................... 85 III.2.2.1 Subjects....................................................................................................... 85 III.2.2.2 Data collection ............................................................................................ 85 III.2.2.3 Experimental protocol................................................................................. 88 III.2.2.4 Data processing........................................................................................... 88 III.2.2.5 Data analysis ............................................................................................... 90 III.2.3 Results ................................................................................................................ 90 III.2.3.1 Stride parameters ........................................................................................ 90 III.2.3.2 EMG activity pattern................................................................................... 92 III.2.3.3 Intensity of muscle activity......................................................................... 96 III.2.4 Discussion and conclusion ................................................................................. 98 III.2.4.1 Muscle activity of thoracolumbar LD during different conditions............. 98 III.2.4.2 Muscle activity of LD between different muscle segments...................... 100 III.2.4.3 Conclusion ................................................................................................ 101 III.3 Ultrasonographic anatomy of the equine thoracolumbar Longissimus dorsi muscle ............................................................................................................................... 102 III.3.1 Introduction ...................................................................................................... 102 III.3.2 Material and Methods....................................................................................... 105 III.3.3 Results .............................................................................................................. 107 III.3.4 Discussion and Conclusion .............................................................................. 124 III.4 Quantitative Ultrasonography of the equine thoracolumbar Longissimus dorsi muscle: repeatability of muscle thickness and pennation angle measurements ... 128 III.4.1 Introduction ...................................................................................................... 128 III.4.2 Material and Methods....................................................................................... 130 III.4.2.1 Subjects..................................................................................................... 130 III.4.2.2 Data collection .......................................................................................... 130 III.4.2.3 Data analysis ............................................................................................. 131 III.4.3 Results .............................................................................................................. 132 III.4.3.1 Variation in muscle thickness measurements ........................................... 132 III.4.3.2 Variation in pennation angle..................................................................... 134 III.4.4 Discussion and Conclusion .............................................................................. 136 IV. Discussion and Conclusion.................................................................................... 139 6 V. References.............................................................................................................