Orthopedic Neurology] Page | 1

[Orthopedic Neurology] Page | 1 Neuro-Anatomy Neuron: Is the specialized cell of the nervous system that capable of electrical exciation (action potential) along their axons 2 | Page [Orthopedic Neurology] Peripheral nerve has a mixture of neurons: 1]. Motor 2]. Sensory 3]. Reflex 4]. Sympathetic 5]. Parasympathetic Types of fibers: A (α, , γ, δ), B, C Motor Sensory Ms reflex sympathetic Parasymp Neuron AHC Dorsal root ganglia AHC IHC relay at organ Root Anterior Dorsal root Ant Ant Ant Tract 1- Direct pyramidal 1- Spinothalamic (Pain, temp, Stretch reflex crude) arc from ms 2- Indirect pyramid 2- Lemniscal (DC) spindle (proprioception, fine touch) Fibre α Motor (12-20 μm) α Propriocep (12-20 μm) γ fibers B preganglionic B fibres Touch, vib (5-12 μm) C Postganglionic δ fast pain, temp (2-5μm) C Slow pain, crude (0.2-2µm) A fibers are most affected by pressure C fibers are most affected by anesthesia and are the principle fibers in the dorsal root Neurons are surrounded by endoneurium GroupToFor m fascicles surrounded by perineurium GroupToFor m nerve surrounded by epineurium Muscle: Motor unit is the unit responsible for motion and formed of the group of ms fibers and neuromuscular junction and feeding neuron Ms fibers types: 1- Smooth ms fibers 2- Cardiac ms fibers 3- Skeletal ms fibers: . Type I: slow twitching, slow fatiguability, posture . TypeII: fast twitiching, fast fatigue MS CONTRACTION: is the active state of a ms, in which there is response to the neuron action potential either by isometric or iso tonic contraction ISOMETRIC CONTRACTION: is the contraction in ώ there is tension ώ out change in the ms length ISOTONIC CONTRACTION: is the contraction in ώ here is a change in the length of the ms éout change in the tone MS TONE: is the resting state of tension MS CONTRACTURE: is the adaptive structural changes in a ms ð prolonged immobilization in a shortened position, in the form of shortening and fibrosis MS WASTING: is the adaptive structural changes in a ms ð prolonged disuse of denervation, in the form of hypoplasias and hypotrophy, and eventually shortening and fibrosis SPASTICITY: Abnormal contraction of a ms in response to stretch. Growth of ms is impaired RIGIDITY: Involuntary sustained contraction of a ms not stretch-dependent. Growth of ms is fair [Orthopedic Neurology] Page | 3 Sarcomere A band...................................... Actin + myocin (= H + overlap zone) H band .................................... Myocin M line ....................................... Myocin Interconnect I band........................................ Actin Z line ........................................ Actin Anchors Contraction Definition Phases Isotonic Constant ms tension & Concentric: ms shortens during contraction length (dynamic) Eccentric: ms lengthens during contraction Isometric Constant ms length (static) Isokinetic Max contraction é constant Concentric velocity over a full ROM Eccentric Aerobic In the presence of O2 Replenishes 34 ATP via Kreb’s Anerobic In the absence of O2 Glycolysis into lactic and 2 ATP ATP hydrolysis éout O2 ATP hydrolysis to produce direct, fast energy Dermatome: o Is the area of skin supplied by a specific nerve root Myotome o Is the group of muscles supplied by a specific nerve root Sclerotome o Is the area of bone and fascia supplied by a specific nerve root Sprain: o Tearing or injury of a non contractile motion unit, e.g. Ligament Strain o Tearing or injury of a contractile motion unit, e.g. Muscle 4 | Page [Orthopedic Neurology] Muscle injuries: 1]. Muscle Strain: • Occurs at Musculo-tendinous junction of the ms that cross 2 joint (e.g. gastroc, hamstring) • First there is inflammation then ends by fibrosis 2]. Muscle tears: • Occurs at the Musculo-tendinous junction • During the higher eccentric contractions & Heal by dense scarring 3]. Muscle soreness: During the higher eccentric contractions 4]. Muscle denervation: Causes atrophy and y sensitivity to acetyl-choline and fibrillation in 2wk Tendons • COMPOSED OF: 1]. Collagen I ......................................... 80% 2]. Fibroblasts synthesis tropocollagens Æ micro-fibrils Æ sub-fibril Æ fibril Æ fascicle 3]. Loose areolar CT .......................... Endotenon Æ epitenon Æ paratenon • TYPES OF TENDONS: a. PARATENON covered tendons rich capillary supply = better healing b. Sheathed tendons ....................... segmental bl.supply via mesotenon (VINCULA) • MUSCULO-TENDINOUS JUNCTION: 1]. Tendon 2]. Fibro-cartilage 3]. Mineralized fibrocartilage (SHARPEY’S fibers) 4]. Bone • HEALING STARTS by fibroblasts and macrophages of the epitenon in 3 phases: 1]. ................................................................ Initial fibroblastic phase: 10 days (weak) 2]. ................................................................ Intermediate Collagen phase 30 days (most of the strength is regained) 3]. ................................................................ Late remodeling phase 6 month (maximal strength is regained) • Collagen tends to arrange along stress lines; so immobilization causes weak healing Ligaments • COMPOSED OF: 1]. Collagen I (same ultrasturcture) ........ 70% 2]. Elastin 3]. Fibroblasts + Loose areolar CT • BL SUPPLY is uniformly arranged via the ligament insertion at bone • Types of ligamentous insertions: 1]. Indirect: ............................................. superficial fr insert to periosteum @ acute angle 2]. Direct ................................................. Deep fr insert to bone @ 90º • BONY LIGAMENTOUS JUNCTION: 1]. Ligament 2]. Fibro-cartilage 3]. Mineralized fibrocartilage (SHARPEY’S fibers) 4]. Bone • HEALING starts by fibroblasts and macrophages of the epitenon Phase Time Process Strength 1].Hemostasis 10 min platelet plug Æ fibrin clot Weak 2].Inflammatory 10 days macrophages debride granulation tissue Weak 3].Fibrogenesis 30 days UMC Æ fibroblasts Æ strong type I collagen most strength regained 4].Remodeling 6-18 mo Realignment & cross linking of collagen bundles Max strength • LIGAMENTS GRAFTING: 1]. Autografts: ..................................................... Faster healing, no disease transmission 2]. Allograft: ......................................................... no donor morbidity but may transmit diseases 3].. Synthetic: (Gortex, Leeds Keio) ................ no initial weakness, but cause sterile effusion [Orthopedic Neurology] Page | 5 Tendon Transfers Definition A tendon transfer is a procedure in which the tendon of insertion or of origin of the functioning muscle is mobilized, detached or divided and reinserted into a bony part or onto another tendon, to supplement or substitute for the action of the recipient tendon, in order to correct muscle imbalance and keep the corrected position rather than to correct a deformity Indications 1]. Irreparable nerve damage 2]. Loss of function of a musculotendinous unit due to trauma or disease 3]. In some nonprogressive or slowly progressive neurological disorders Contraindications 1]. Unstable joint 2]. Stiff joint 3]. Fixed deformity 4]. Advanced arthritis 5]. If affection of all muscles at the same degree 6]. If no suitable tendon or muscle is available for transfer Principles Preoperative 1]. Age: It is better to delay operations >5y so you can get cooperation in physiotherapy: o If the patient is skeletally immature do tendon transfers (TT) o If the patient is skeletally mature do fusion + removal of appropriate wege ± TT o If the patient is has talipes valgus add stabilizing bony op. e.g. Grice Green or Evans 2]. Timing: Early tendon transfers – within 12 weeks of injury: If no chance of functional recovery, transfers should be performed ASAP Late tendon transfers -- If reasonable return of function not present for 3m after the expected Following nerve injury repair, the date of expected recovery can be calculated by measuring the distance between the injury to the most proximal muscle supplied, assuming a rate of regeneration of 1mm/day 3]. Planning Make a list of deficient functions Make a list of available donor muscles Availability of tendon for transfer: o If many tendons are available do tendon transfers for all deficient muscles o If 2 tendons are available do TT for the most crucial functional muscle o If one agonist tendon is available do TT to the middle line e.g. Tohen transfer o If one antagonist tendon do split TT & suture under equal tension Operative Joint: 1]. Should be stable 2]. Should be a freely mobile joint (free ROM) 3]. Should not have fixed deformity 4]. Should not have advanced arthritis 6 | Page [Orthopedic Neurology] Muscles: 1]. Adequate donor muscle Strength (G IV, V) 2]. Adequate recipient muscle Excursion: o Wrist flexors ......................................... 33cm o Finger extensor ................................... 50cm o Finger flexor ......................................... 70cm 3]. Adequate neurologic & blood supply 4]. Agonists better than antagonists 5]. Synergestic better than non synergestic 6]. Start Proximal then distal Tendon 1]. Should be of an adequate Length 2]. Should pass in a Straight line 3]. Should pass through a Gliding Medium (the best is fat or superficial fascia) 4]. Should be sutured under Moderate Tension 5]. Should be Covered 6]. Better to suture tendon To Bone (pull-out technique) Techniques 1]. Multiple short transverse incisions rather than long longitudinal incisions 2]. Careful tendon handling 3]. Joining the tendons o End to end anastomoses o End to side anastomoses o Side to side anastomoses o Tendon weave

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