Hand and Wrist Anatomy and Biomechanics Review PDF

1 / Anatomy Carpal Tunnel Landmarks -​ Scaphoid tubercle -​ Trapezium tubercle -​ Hook of hamate -​ Pisiform -​ The flexor retinaculum is attached to these four points Anatomical Snuffbox Landmarks -​ Lateral tendons are abductor pollicis longus and extensor pollicis brevis -​...

1 / Anatomy Carpal Tunnel Landmarks -​ Scaphoid tubercle -​ Trapezium tubercle -​ Hook of hamate -​ Pisiform -​ The flexor retinaculum is attached to these four points Anatomical Snuffbox Landmarks -​ Lateral tendons are abductor pollicis longus and extensor pollicis brevis -​ Medial tendon is extensor pollicis longus -​ The scaphoid is the ‘floor’ and the radial artery is inside Tunnel of Guyon -​ Between pisiform and hook of hamate (covered by pisohamate lig) -​ Contains ulnar nerve The midcarpal joint is important for its mobility -​ This is the joint between the proximal row and distal row of carpals -​ There are no interosseous ligaments, increasing the mobility -​ This is needed for full ROM of the wrist TFCC -​ Triangular fibrocartilage complex -​ Includes the disc of the UMT -​ Important structure for stability of the wrist -​ Poorly vascularised, slow healing -​ Most aggravated by extension with pronation (under load) 2a / Wrist Biomechanics The wrist complex: - distal radioulnar joint - radiocarpal joint - midcarpal joint Radiocarpal joint includes the articulation between the TFCC and the carpals (lunate, triquetrum) because it acts as an extension of the ulna. In other words, when we say radiocarpal in the context of biomechanics, we include the UMT joint as well. Flexion-Extension Mechanics Axis of Flexion-Extension - capitate Flexion primarily occurs at - midcarpal Extension primarily occurs at - radiocarpal Radiocarpal Closed Pack (Full extension) caused by - asymmetry of scaphoid movement - relies on movement of lunate on scaphoid Closed pack is a high risk of injury (FOOSH) -​ Most common fractured carpal = scaphoid -​ Most common dislocated = lunate (palmar direction) -​ Both at risk of avascular necrosis Mob to increase flexion - dorsal glide proximal carpals Mob to increase extension - palmar glide proximal carpals Radial-Ulnar Deviation Mechanics Axis of deviations - capitate Convex-on-concave - movement is opposite In ulnar deviation, proximal and distal row of carpals do radial glide In radial deviation, proximal and distal row of carpals do ulnar glide In addition to glides, there are small rotation movements that happen between each row of carpals. These are small and complex. The key point from this is that a necessary portion of full ulnar deviation or radial deviation is mobility between the rows of carpals. Thai can inform our treatment when trying to achieve full radial or ulnar deviation. 2b / Hand Biomechanics Functional arches of the hand -​ 1 longitudinal arch (per digit) -​ Most important is through digit 3 and the capitate -​ 2 transverse arches -​ 1 is the transverse carpal arch which runs through the distal row of carpals -​ This is sometimes called the proximal transverse arch -​ 1 is the transverse metacarpal arch which runs through the head of the metacarpals -​ This is sometimes called the distal transverse arch -​ Consists of the heads of the metacarpals -​ Focal point is MC 3, capitate and lunate Cascade Sign and finger flexion -​ only index finger flexes in sagittal plane -​ all others flex in oblique plane towards scaphoid Length-Tension Relationships Extrinsic Muscles of the hand - the wrist provides a stable base for the hand - its position controls the length of the extrinsic hand muscle **Movements of the wrist are usually in reverse of the movements of the fingers and reinforce the action of the extrinsic muscle of the fingers In finger Flexion - wrist extensors activate to stabilise wrist - prevent long finger flexors from simultaneously flexing the wrist In finger Extension - wrist flexors activate to stabilise the wrist - long finger extensors can function more effectively **Grip Strength - as grip strength increases, extensors slacken allowing a favourable shortening of the flexors to achieve a strong contraction Greatest interphalangeal flexion force - ulnar deviation and neutral flexion-extension Weakest interphalangeal flexion force - when the wrist is in full flexion (too short to generate force) Dorsal Digital Expansion DDE - originates on posterior, medial, lateral surfaces of proximal phalanges 1 - 5 - extrinsic tendons are ED & EPL - intrinsic tendons are lumbricals and interossei - there is trifurcation on dorsal aspect Prehension (grip) Power grips - object contacts palm - isometric Precision Grip - object does not contact palm - isotonic Grabbing something usually involves median/ulnar nerves; release of something involves the radial nerve. 2c / Observation Swan Neck MCP - Flexion PIP - Extension DIP - Flexion Caused by contracture of muscle or tearing volar plate (@ PIP) - usually with RA or post trauma Boutonniere MCP - Extension PIP - Flexion DIP - Extension Caused by rupture of central slip (@ PIP) of DDE - usually with RA or post trauma Dupuytren's Contracture of palmar fascia Contracture - including skin - MC digits 4, 5 MCP& PIP - fixed flexion deformity Heberden's Nodes Arthritic change on dorsal surfaces of DIPS Bouchard's Nodes Arthritic changes on dorsal surfaces of PIPS Drifts Ulnar Drift - with RA - changes in MCP and resulting pull on long tendons Radial Drift - with OA Z deformity of thumb MCP Flexion IP Hyperextension - due to RA or hereditary Mallet Finger Distal phalanx is flexed - results from rupture or avulsion of extensor tendon at distal insertion Neurological Deformities Ulnar Nerve (C8-T1) Bishop’s Hand aka Benediction Claw Hand (Rattray) Froment’s Sign Hand (Magee) Resting Resting Active Loss of ulnar lumbricals leads to digits Same as Bishop’s hand, but said to Loss of adductor pollicis (innervated 4 & 5 resting in a position opposite to have some abduction of digits 4 & 5 by ulnar nerve) leads to the lumbricals action compensatory recruitment of flexor pollicis longus (innervated by median nerve) Median Nerve (C5-T1) Ape Hand (Magee, Rattray) Oath Hand (Rattray) Resting Active Thenar muscle wasting causes the thumb to rest in line Attempts to make a fist are unsuccessful. Ulnar digits 4 & with the other digits and also causes inability to oppose or 5 flex but median digits 1, 2, 3 do not. Looks similar to the flex thumb resting ulnar deformity Bishop’s hand above. Combined Median Nerve (C5-T1) & Ulnar Nerve (C8-T1) Claw Fingers (Magee) Resting Loss of finger flexors leads to resting finger extension deformity. Cannot cup hand. Radial Nerve (C5-T1) Wrist Drop (Rattray) aka Drop Wrist (Magee) Resting Loss of extensors leads to flexed wrist and finger posture with inability to extend wrist or fingers 3 / Pathologies (Tables and pictures from Myers & Hanks, 5th Ed) Carpal Tunnel Syndrome (See PNS Tx) Median nerve compression; either decreased space in tunnel or increased size of contents inside tunnel; can be due to external pressure on wrist. Hallmark sign = nocturnal pain, especially in digits 1-3 (as opposed to the skin over the thenar eminence) Important to differentiate pronator teres as an alternate compression site of the median nerve. Dupuytren’s Contracture Affects the palmar fascia -​ The palmar fascia has 3 layers - longitudinal, transverse, vertical -​ Palmaris longus inserts into palmar fascia and is therefore indirectly affected by Dupuytren’s contracture Idiopathic condition -​ Slowly progressive -​ Does not affect tendon, muscle, or joint Signs & symptoms -​ Tender, thick, nodular palmar fascia -​ MCP & IP joints stuck in flexed position due to fascial shortening -​ Usually affects the palmar fascia in line with digits 4 & 5 Treatment plan: -​ Heat, MFR, and stretching. Dupuytren's is a long-term process which is very resistant to change, so frequent treatment and self-care over a long period of time are necessary. Skier’s Thumb / Gamekeeper’s Thumb UCL sprain of the first MCP joint The MCP joint sits between a highly mobile saddle joint (CMC) and a very rigid hinge joint (IP) and is vulnerable to instability because of the forces it is subject to. UCL dysfunction of the thumb may be the result of acute trauma such as forceful abduction or radial deviation of the thumb away from the palm. It may also result from repetitive stress, or be secondary instability from chronic OA changes. FYI: If the CMC undergoes arthritic changes, it becomes more lax (less joint space due to loss of cartilage creates ligamentous and capsular laxity at the CMC joint). If the CMC is more lax, the thenar muscles adaptively shorten and pull the thumb into a slightly flexed position. This makes extension of the thumb to grasp objects difficult, so the body compensates by radially deviating the thumb. Continued radial deviation stress on the thumb will create laxity in the UCL of the thumb. Symptoms & history: -​ Ulnar-sided MCP pain at digit 1 -​ Difficulty and pain with gripping and pinching -​ Positive UCL of the thumb stress test Differential: -​ If due to trauma, in the presence of first dorsal interosseous swelling, the person should be referred to xray to rule out fracture Treatment plan: -​ Minor sprains benefit from taping, bracing/orthoses for the CMC, and reduction in provoking movements for about 3 weeks. -​ Strengthening the first dorsal interosseous muscle is helpful. -​ Once AROM is pain-free, more challenging activities like biking and heavy gripping should be gradually reintroduced. -​ Moderate sprains should be treated the same but may take up to months and require the use of a brace or orthoses for 6 weeks -​ Full rupture requires surgery; your treatment plan will be guided by post-surgical advice. Flexor Pollicis Longus Tenosynovitis The tendinous sheath of the FPL is sometimes called the radial bursa and extends from radial and superficial to the carpal tunnel before angling around the scaphoid and trapezium to the thumb.This area is a potential site of irritation to the FPL tendon and its sheath. Symptoms & history: -​ Palmar thumb pain especially with movement. It normally follows repeated thumb use such as gripping, rock climbing, or texting. -​ Classic presentation is pain with AROM or concentric RROM but pain-free MMT. The reason is that movement of the tendon within the sheath is the problem. An isometric contraction does not cause movement and thus would not be painful or weak. Differential: -​ Sprain -​ While the median nerve and C6 nerve root both refer into this area, the quality of symptom, movement findings, and history should clearly distinguish. Treatment plan: -​ Identify and eliminate or modify the provoking factor -​ NMT, dynamic release, MFR to FPL muscle -​ Gentle skin rolling and MFR in palm; frictions should be avoided if flared-up or not tolerated (the bone is very close and frictioning an irritated sheath into a bone is not a good idea -​ Isometric strength should be progressed before reintroducing full ROM; eg, pain-free isometric holds of 10 times 60s of thumb flexion should be achieved before going into full ROM 1st CMC OA 1st CMC OA is common in older adults. It is of course a long-term degenerative process; it causes pain and relative instability of the 1st CMC (due to capsular laxity as discussed in the FYI under Skier’s thumb) which may predispose to UCL of the thumb injury. Symptoms & history: -​ Pain in the area of the anatomical snuffbox especially with thumb movement. Pain is worse in the morning or after prolonged disuse. Pain is generally helped with heat. -​ Activities which cause compression (forceful gripping, pinching, radial deviation) will be painful and these are generally avoided. This can create significant disability and loss of function. -​ There may also be thenar contracture, reduced thumb abduction, decreased CMC ROM, intrinsic muscle atrophy and weakness (from disuse) and eventual MCP UCL pain or dysfunction. Differential: -​ DeQuervain’s -​ Scaphoid fracture or dislocation, if trauma occurred at the onset of symptoms -​ Radial nerve irritation Treatment plan: -​ Remove provoking movements for a period of time -​ Taping, bracing, CMC orthosis may be helpful in reducing severity in order to begin rehab -​ Thenar muscle MFR, stretching into abduction, and massage -​ Joint distraction -​ Hand function - strengthening dorsal interosseous muscle and other intrinsic hand muscles -​ Pain-free gentle ROM such as a thumb rolling exercise Fractures & Dislocations Colles -​ Dinner Fork > radius fragment is displaced dorsally just proximal to wrist -​ FOOSH -​ Complications of poor union and reflex sympathetic dystrophy Galeazzi -​ Radius fracture with dislocation of Distal radioulnar joint -​ Complications of ulnar nerve injury Scaphoid -​ Most commonly fractured carpal -​ Most commonly misdiagnosed sprain -​ Difficult to diagnose by xray -​ Poorly vascularised / easily compromised blood vessels with injury -​ Complication of avascular necrosis Lunate Dislocation  -​ Most commonly dislocated carpal -​ Occurs in palmar direction -​ Complications of possible median nerve injury and avascular necrosis of lunate Trigger Finger Aka digital tenovaginitis / tenosynovitis / stenosing tenosynovitis Due to -​ Thickening of flexor tendon sheath (FDS) -​ Nodules developing along affected tendon, usually beginning at the MCP just distal to the palm crease When the finger is flexed, the nodule moves proximally. As the patient attempts to extend the finger, the nodule has to move back, creating a palpable and sometimes audible click. Results in -​ Sticking of finger in flexed position > cannot return to extended position -​ Painful snapping sensation as finger lets go progresses to finger not letting go and needing help (passive) with extension Trigger finger is idiopathic but often preceded by a recent activity requiring increased finger flexion force. The nodules are palpable and a click, catch, or lock is often observed or palpated during flexion-extension. Movement is painful. Treatment plan: -​ Taping, bracing, orthosis may be helpful in reducing severity in order to begin rehab or to prevent exacerbation -​ Especially, using tape or a splint that will keep the MCP extended often allows the inflammation and friction to reduce and the nodule to resolve itself -​ During this time, massage to decrease flexor tone and stimulate extensor function can he helpful Finger Arthritis Both RA and OA affect the fingers. Commonly, multiple joints at the same level (eg multiple MCPs, or multiple PIPs) are affected. Overall, OA has a better prognosis than RA for hand function. RA mainly affects the MCPs. OA mainly affects the PIPs (Bouchard’s nodes) and the DIPs (Heberden’s nodes) RA typically presents as hypermobile due to destruction of the joint capsule over time from chronic inflammation. OA typically presents as hypomobile. Both may present with ulnar drift primarily at the MCP, but it is much more common in inflammatory arthritis (RA). Overall hand function can be severely reduced including grip and pinch. Gout should be ruled out by medical exam, especially if only one joint is affected and the onset was relatively fast. Treatment plan: -​ Taping, bracing, orthosis may be helpful in reducing severity in order to begin rehab or to prevent exacerbation -​ Intrinsic hand muscle function, especially lumbricals is most indicated. If strengthening exercises emphasise extrinsic hand muscle function, it is likely to increase or lead to the onset of ulnar drift -​ Joint distraction, stretching, and massage -​ Pain-free gentle ROM -​ Recommend a medical doctor or hand specialist; they can provide advice on various equipment that will make ADLs easier to perform DeQuervain’s Syndrome DeQuervain’s is one of 3 common sources of radial wrist pain (see table above). Affects Abductor pollicis longus & extensor pollicis brevis -​ Tenosynovitis (inflammation of tendon sheath) Due to repetitive ulnar-radial deviation and forceful gripping Treatment plan: -​ Identification and modification of the provoking movement are important -​ Dynamic release and MFR through the muscles of the anatomical snuffbox and surrounding muscles are helpful -​ Isometric activation and strengthening should be pain-free before going to resisted concentric movements TFCC Injury TFCC injuries are one of the most common causes of ulnar wrist pain. Most are traumatic such as FOOSH with hyperextension or a rotation injury. However, slow onset through repetitive stress is also possible. Symptoms & history -​ Deep, ulnar-sided wrist pain -​ Pain worse with weight bearing or carrying heavy objects -​ Pain worse with end-range pronation, extension and ulnar deviation -​ May complain of wrist instability -​ Note that edema is rare (unless due to other injured tissue such as fracture) Differential -​ UCL sprain -​ DRU jt sprain -​ FCU or ECU tendinopathy Treatment plan: -​ Immobilisation and bracing or compression to support wrist joint -​ Medical management may include cortisone injections or NSAIDs -​ Active assisted and active wrist ROM -​ Strengthening of forearm muscles and massage to those muscles to support proper function -​ Traction or joint mobilisation are not strongly supported in research but can be tried and monitored 4 / Orthopedic Tests (finish this table) Under indication -​ What about the person’s presentation would make you choose this test? -​ What is the give-away sign or symptom that makes you want to confirm or rule out a condition? Test Relevant Condition Positive Indication Ulnocarpal stress test TFCC lesion Ulnar impaction test TFCC lesion Ulnar & radial collateral UCL & RCL of thumb stress test Finkelstein test De Quervain’s (paratenonitis) Allen test Circulation to hand Digit blood flow Circulation to fingers (capillary refill) 5 / Home Care Principles -​ As you know, -​ Strengthen weak muscles -​ Stretch short muscles Extrinsic v Instrinsic hand muscles -​ Think about creative ways to strengthen different finger and hand movements -​ Think about isolating intrinsic hand muscles (no wrist movement) from extrinsic (as much as possible)