The osseous construction of the hand and foot developed in the same manner during a long period of evolution. Even today, many similarities can be discovered between these two sections of the skeleton. It is well known that the acquisition of upright stance and bipedal locomotion differentiates the skeleton of the upper limb fully from the skeleton of the lower limb.
As the end organ of the upper limb, the hand is a well-developed working instrument with a large variety of very fine functions. Kapandji (2006) described the different types of grasp. These include power grips and precision handling, with pinching (bi-digital grasping using the thumb and index finger) being the most important function.
The precision with which the visually impaired are able to recognize different surfaces, materials, and consistencies is always impressive. The high density of mechanoreceptors in the skin of the hand and particularly of the fingertips provides humans with the extraordinary ability to perceive differences in the smallest of areas (ability to discriminate). The large sensory supply of the hand is mirrored in the hand’s representation in the sensory cortex.
The hand naturally plays an important role in nonverbal communication, the interaction between gestures, mimic, and body posture. Everyone is familiar with typical, common, and international gestures and positions of the hand, such as connecting the thumb and the index finger into a circle (forming an “O”) and holding the other fingers straight or relaxed in the air to indicate that everything is okay.
A large number of joints in the wrist and the fingers, with some of these joints being very mobile. The amazing interaction between the bones of the wrist (carpal bones) is based on the three-dimensional movements seen in every bone during forward and backward movements of the palm (flexion and extension of the wrist) and sideways movements (ulnar and radial deviation of the wrist). With two joint lines (radio- and mediocarpal) in the hand, the carpus gives the hand the amazing mobility of a range of motion up to 180° for flexion and extension.
Opposition of the thumb and the finger. The ability of the thumb bones to turn toward the other fingers (opposition) is shared by many primates. The particular spatial orientation of the trapezium in relation to the other bones of the carpus is the chief factor in this ability. Thus, at rest, the relaxed thumb hangs approximately 35° in a palmar direction, 15° in a radial direction (Zancolli et al., 1987). These two characteristics, combined with the special muscles acting on the thumb, enable opposition. Not only the thumb, but also the fingers are able to oppose. This becomes clear when therapists view the palmar aspect of the extended hand and flex each finger individually. In flexion, every fingertip points to the carpometacarpal joint.
Finger opposition can also be identified when the thumb touches the small finger. The finger pads of the thumb and fifth finger come into contact, not the sides of the fingers. Metacarpal V also has its own opponens muscle (▶ Fig. 4.1).
Mobility, expression, and functional diversity are impossible without a stable base. The different types of grasp and the development of strength are almost impossible without a central fixed point within the hand.
This stable center is located in the transition between the carpus (here the distal row of carpal bones) and the bases of metacarpals II to V (carpometacarpal joint line). This area is identified by the rigidity of the articular connections. All anatomical parameters, such as the jagged joint line, articular surfaces of complex structure, and a dense supply of ligaments, indicate stability, not mobility.
This carpal and the metacarpal junction also form a bony transverse arch that is comparable to the transverse arch of the foot in its position, significance, and the point of its evolutionary development. It is the osseous foundation for the carpal tunnel (carpal groove).
The proximal ends of the metacarpals articulate firmly with each other and with the carpus. Distally, connected by syndesmoses, they move very freely against each other. The palm can therefore flatten itself out—important for power grips—as well as cupping the hand—which is of importance for precision handling using the fingers.
The extraordinary presence of the hand in the primary motor center of the precentral gyrus (Williams, 2009) as well as the developmentally most recent tracts of the voluntary motor system, constitute the motor basis of the functional diversity. Just the functionally vital pincer grip requires finely tuned coordination based on small motor units (▶ Fig. 4.2).
The special feature of this section of the skeleton is the close proximity of clinically relevant structures in a tight area. The therapist searches for the source of most symptoms either in the carpus or its close proximity. Nontraumatic problems are rarely observed toward the forearm or the fingers. Therefore, the carpus region and the anatomical structures surrounding the carpus take up the largest proportion of the precise palpation of the hand.
Arthritis, mainly caused by rheumatic disease or trauma. Joint inflammation is not only seen in the wrist area; it can also be observed in the distal radioulnar joint (DRUJ) and the first carpometacarpal joint, which must be kept in mind in differential diagnosis of radial or ulnar symptoms.
Restrictions in mobility, mostly as a result of immobilization, for example, following fractures near the joint (Colles fracture). When presented with a hand with restricted mobility, the crucial issue for the therapist is to locate the point of restriction. Should the therapist start treating the radiocarpal joint, or should the local carpal bones be assessed first?
Globally at the carpal joint lines: mid-carpal instability is located at the mediocarpal joint between the two rows of carpal bones (Lichtman, 2006). Palmar dislocations of the radiocarpal joint are typically encountered with rheumatoid arthritis.
Local, within the carpus: here, attention is on the lunate. It is held in position with intrinsic ligaments within the proximal row of scaphoid and triquetrum. If one of these ligaments ruptures as a result of a trauma, the lunate most often dislocates with a translational component in a palmar direction.
The passage of tendons through compartments and the carpal tunnel, for example, and also the fixed points of the long muscles in the wrist provide sufficient opportunity for the development of overuse problems. The entire spectrum of possible pathological conditions can be observed here: tenosynovitis, myotenosynovitis, and insertion tendinopathy. On the dorsal side, the tendons travel in tendon compartments. On the palmar aspect, nine tendons and one nerve are bundled together in the carpal tunnel. Symptoms in this region can often be improved with precisely applied treatments.
The median nerve can be compromised in the carpal tunnel. A variety of provocative tests for carpal tunnel syndrome are based on the careful location of the point of constriction. Cyclists occasionally compress the ulnar nerve in the Guyon canal (“handlebar palsy”). The radial nerve can be compressed as it passes through the fascia of the forearm into the superficial tissue.
The therapist’s challenge is to identify the causative laxity and thus the reason for the symptoms, using understanding of the local biomechanics and precision in locating the articulating bones. The necessary foundation for this task is knowledge of local surface anatomy based on good topographic and morphological knowledge.
It is an advantage of surface anatomy on the hand that patients are usually able to describe their symptoms exactly. With the exception of neural irritation, referred pain is not expected so far distally in the limb. In regard to diagnosis, this means that besides the assessment of function, the pain reported is of great importance to identify the affected structure.
There have been exact anatomical representations of the hand since Da Vinci and Vesalius. Since that time, there has been no change in the choice of the simpler, more transparent dorsal view for a description of the anatomy (Berger, 2010). In addition to the familiar horizontal anatomical divisions of the hand into the carpus, metacarpus, and phalanges (▶ Fig. 4.3), the skeleton of the hand can also be divided in an axial direction (▶ Fig. 4.4). The so-called columnar design was already described by Navarro in 1937 (Matthijs et al., 2003).
This classification is the result of experience when addressing clinical aspects. Each column consists of one or two “rays” (metacarpals plus phalanges) and the corresponding longitudinally positioned carpal bones:
Radial column: this column comprises the first and second rays as well as the trapezium and scaphoid (distal pole). Experience shows that arthrotic changes are most frequently detected here. The scaphoid articulates with four neighboring carpal bones and the radius so that it controls the biomechanics of both capitate and lunate. Hypomobility and fractures, particularly of the scaphoid, are encountered most frequently in the radial column. Within this column, the thumb column can be considered separately since the skeleton of the thumb is set apart from the rest of the carpus by the special orientation of the trapezium. This would then include the first ray, trapezium, and scaphoid (▶ Fig. 4.5).
Central column: the principal ray of the hand (metacarpal III and middle finger) plus the capitate, scaphoid (proximal pole), and lunate form the central column. In addition to the location of hypomobilities, the clinical particularity of this column is the frequent occurrence of local instabilities, especially of the lunate, with possible dislocations fixed in a nonphysiological position and under stress. Finally, dislocation is promoted by the sagittal angling of the distal radius (volar tilt) and the arrangement of the deep palmar ligaments (▶ Fig. 4.6). Local mobility tests of the articular connections of the lunate to the neighboring articulation partners test the local stability if it is possible to determine precisely the location of the individual carpal bones.
Ulnar column: the connections between the fourth and fifth rays, hamate, and triquetrum opposite the articular disk of the DRUJ are known to be hypermobile and can cause symptoms. The stability of the ulnar column depends to a large degree on the intact condition of the TFC complex.
The arrangement of eight carpal bones in two rows provides the basis for the anatomical structure of the carpus. In this arrangement in rows, the proximal row of carpal bones has a particular importance. With the exception of the flexor carpi ulnaris, no extrinsic muscle is directly attached to this row. The pisiform is indeed classified as a carpal bone, but biomechanically it is not part of the proximal row.
This independence from muscular influence marks the function of the proximal row as an intercalated segment that mediates between two rigid entities (distal forearm and distal carpal row of the metacarpals). The proximal row is able to perform this function through large, passive accompanying movements during planar movement (extension and flexion) and marginal movement (ulnar and radial abduction). The planar and marginal movements of the hand are assigned to two articular rows: radiocarpal and mediocarpal joints, where each carpal bone has its own degree of motion (De Lange et al., 1985). The mobility of the marginal movements depends on the position of the forearm. At complete supination, the forearm is pulled distally by contraction of certain fibers of the interosseous membrane of the forearm, and the degree of radial abduction is less than in full pronation. Scaphoid and lunate articulate with the corresponding articular groove at the radius (scaphoid fossa and lunate fossa), the triquetrum with the articular disk of the ulna. The radius has a total of two angles in relation to its longitudinal axis: an ulnar and a palmar tilt (see ▶ Fig. 4.18).
The distal row articulates with the proximal row in the mediocarpal joint; both rows have a generally convex form. It is only radially that the curvature between the scaphoid and the two trapezoid bones turns around. This makes it possible for the trapezoid and the trapezium to glide onto the scaphoid in extension (with radial abduction), which, in end-range motion, brings them into the direct vicinity of the distal radius. The mediocarpal joint is a hinge joint that permits radial extension and ulnar flexion around an oblique axis, known in the literature as a dart-throwing motion (Moritomo et al., 2007).
The carpus is responsible for ensuring that the hand is optimally positioned in space for its various tasks. To achieve this, a high degree of mobility must be reached while ensuring stability (Ryu and Klin, 2010).
The proximal carpal row is the intercalated segment, which in every position represents a stable socket toward distal and a head toward proximal. The proximal carpal row achieves this with compensatory movements between the individual members of this row (▶ Fig. 4.7).
The task of this model is to ensure a high degree of mobility under compressive forces in every position at the same time. The stability of the hand is ensured by the bony and, in particular, capsuloligamentous structures. With the exception of the flexor carpi ulnaris muscle, the carpus is completely traversed by the tendons of the extrinsic muscles. These tendons insert at the bases of the metacarpals and the finger skeleton.
In terms of kinematics, the greatest challenge involves ensuring the stability of the carpus while actively grasping objects. The maximum grasping force comes about when the hand is held in slight extension. This means that at the moment of grasping, the hand extensors, hand flexors, finger flexors, and thumb flexor are active and thus exert compression force on the carpus. In the middle position of the hand, of the total compression force transferred to the forearm, around 50% is transferred via the radial column, 30% via the central column, and 20% via the ulnar column (Hara et al., 1992).
At the moment of grasping, during the activity of the two radial hand extensors, the mediocarpal joint is in slight radial extension. This results in two mechanisms (▶ Fig. 4.8):
The compressive force on the radial side presses the distal pole of the scaphoid palmarly in the direction of flexion (Kobayashi et al., 1997). This flexion tendency transfers it over an intrinsic ligament (scapolunate ligament) to the lunate.
The radial extension stretches a part of the deep extrinsic ligaments, that is, the arcuate or triquetral capitate ligament, in a palmar direction. This exerts an extensory force on the triquetrum that transfers this extension tendency to the lunate via an additional intrinsic ligament (triquetral lunate ligament).
The stability of the ulnar carpus and the distal radioulnar joint is controlled by the TFC complex (▶ Fig. 4.9).
The main components are the articular disk of the DRUJ, the ulnar collateral ligament of the wrist joint, the deep ulnocarpal ligaments, and the synovial sheath of the extensor carpi ulnaris tendon. The disk extends between the ulnar styloid process and the border of the radial articular surface for the DRUJ and is supported by ligaments.
The two rows of carpal bones form a transverse arch, the carpal tunnel. The term “row” is actually quite confusing. The construction of the carpal arch becomes clear when the therapist examines the parts of bone that protrude palmarly (▶ Fig. 4.10):
The four tendons of the flexor digitorum profundus (▶ Fig. 4.11).
The four tendons of the flexor digitorum superficialis (▶ Fig. 4.12).
The tendon of the flexor pollicis longus (▶ Fig. 4.13).
In the past, the flexor carpi radialis tendon was considered part of the carpal tunnel. Its course underneath the ligament is listed as a separate passage in topographical anatomy (Beckenbaugh in Cooney, 2010).
The tendons of the long (extrinsic) muscles that move the hand and finger skeletons are held close to the radius and ulna in their palmar and dorsal aspects and at the sides of the forearm by a deep thickening of the forearm fascia (flexor and extensor retinacula).
The retinacula maintain the position of all the tendons in relation to the forearm, even during large rotatory movements of the hand or the forearm. The extensor retinaculum extends between the radius and the tendon sheath of the flexor carpi ulnaris and is attached to the bones between the respective tendon compartments, so that small osteofibrous canals are formed for the passage of the tendons (▶ Fig. 4.16). Tendon sheaths protect the tendons at this point from frictioning during movement.
The six canals through which the tendons pass are named tendon compartments (▶ Fig. 4.15).
Fig. 4.16 Extensor tendons and retinaculum extensorum—distal view after Omer Matthijs). FCU: flexor carpi ulnaris. ECU: extensor carpi ulnaris. EDM: extensor digiti minimi. EI: extensor indicis. ED: extensor digitorum. EPL: extensor pollicis longus. ECRB: extensor carpi radialis brevis. ECRL: extensor carpi radialis longus. EPB: extensor pollicis brevis. APL: abductor pollicis longus.
The following instructions for finding the structures of the hand start on the dorsal aspect. The therapist first gains a general impression of the dimensions of the carpus and its proximal and distal boundaries so that precise information can be obtained on the size of the carpus and metacarpus. The therapist looks for distinct bony edges and points. This lays the groundwork for very local display of the extensor tendons in their tendon sheaths as well as of the individual carpal bones.
For the hand to be palpated, a relaxed position is selected that can be maintained without muscle activity. When palpating osseous structures, it is essential that all types of muscular contraction be avoided by placing the hand and forearm on a level surface (▶ Fig. 4.17). If this is not done, the more superficially located tendons will be placed under tension and impede the specific search for deeper-lying structures. The therapist sits next to the ulnar side of the hand.
Directions will be described using the terms radial (toward the thumb), ulnar (toward the small finger), dorsal (toward the back of the hand), and palmar (toward the palm). This may take a while to get used to, but it enables the use of exact terminology and therefore understanding. For example, the joint space of the DRUJ is found radial to the head of the ulna.
The boundary between the proximal row of carpal bones and the forearm marks the joint space for the radiocarpal joint. In particular, the joint line orients itself on the edges of the radius and ulna.
The palpating finger moves first from distal, so that the fingertip can meet the radius and the head of the ulna (transverse palpation,▶ Fig. 4.18). It is most effective to start on the radial side of the hand in a depression at the carpus (radial fossa), which will be described in more detail below.
Transverse palpation at this point encounters a distinct, hard resistance when it reaches the edge of the radius. Moving a little more toward the palm, one can find the radial styloid process, the radial and right palmar boundary of the radius ( ▶ Fig. 4.19 and ▶ Fig. 4.20). Above the radial styloid are the tendons of extensor compartment I and the V-shaped radial collateral ligament runs to the radial carpus (scaphoid and trapezium) from its tip.
The same technique is used to locate the boundaries of the carpus by palpating from radial to ulnar. The rounded tendons passing through their compartments in the wrist increasingly interfere with the palpation more ulnarly (▶ Fig. 4.21). When the palpating finger moves proximally from the second and third ray it feels, exactly when it reaches the radius at the level of the ulnar head, the drop-shaped dorsal tubercle of the radius, also known as the Lister tubercle (▶ Fig. 4.22). Directly distal to this is the edge of the radius. Further in the ulnar direction is the transition between radius and ulna. The level of the distal radioulnar articular space has been reached when the rather straight edge of the radius takes on a convex shape and the transition can be felt, on palpation, to be a small, V-shaped depression (▶ Fig. 4.23). The palpation ends distal to the ulnar head and the ulnar styloid process, located to the side (ulnar and dorsal) at the ulnar head (▶ Fig. 4.24).
If tendons hinder the palpation of the edge of the radius, the wrist is extended slightly and the hand relaxed. This causes the proximal row of bones to disappear in a palmar direction and relaxes the soft-tissue structures. The position of the extensor digiti minimi tendon at the level of the ulnar head confirms the position of the DRUJ space.
For rapid location of the proximal boundary corresponding to the joint space of the radiocarpal joint, another structure must be found. Connecting the styloid process of the radius, the distal aspect of the dorsal radial tubercle, with the ulnar styloid process, easily yields a line that exactly reproduces the course and orientation of the radiocarpal joint space.
It becomes clear that the orientation of the joint space is not exactly perpendicular to the forearm. In fact, seen from radial to ulnar, it runs obliquely proximal (▶ Fig. 4.25). Different angles are given in the literature. Taleisnik (1984) described the average value of this angle as 22° (12–30°), where the left–right differences, at an average of 1.5°, are very small (Hollevoet, 2000). Not depicted here, the joint surface of the distal radius in the sagittal plane, seen from the side, decreases from dorsal–distal to palmar–proximal. This palmar tilt measures an average of 11 to 15° (Taleisnik, 1984; Zanetti et al., 2001) and varies intraindividually by an average of 2.5° (Hollevoet, 2000). In addition, Zanetti reports changes in palmar tilt depending on the position of the forearm. In complete supination it is 29° but in complete pronation it is only 13°. This area is so precisely examined because there are so many global mobilization techniques available in manual therapy used to mobilize the whole hand at the radiocarpal joint. In using them, the therapist should have a spatial understanding of how the joint surfaces bend and vary.
The distal boundary of the carpus is significantly more difficult to feel than the proximal boundary. The starting position is the same. The fingertips of the palpating hand still point in a proximal direction. First the joint line between the base of metacarpal III and the capitate or between metacarpal IV and the hamate is located. This can only be done centrally here, since further toward the radius, the joint line cannot be directly reached due to the protuberances on metacarpals II and III.
The palpating finger pad moves in a proximal direction directly on the shaft of the third or between the third and fourth metacarpals until it feels the base as an elevation (▶ Fig. 4.26). On top of this elevation is the very narrow joint space that is being sought. For this reason, the fingers must now be raised to their tips in order to feel the joint space as a narrow gap, very locally and with some pressure (▶ Fig. 4.27). This technique can be used for the joint space between metacarpal III and the capitate and for the joint space between metacarpal IV and hamate.
At approximately the same level is the joint space between metacarpal V and the hamate. The base of metacarpal V offers another very helpful anatomical feature: a tuberosity for the insertion of the extensor carpi ulnaris (see ▶ Fig. 4.36). This can be easily felt perpendicularly from proximal.
The joint space to the radial, at metacarpal II, can be felt with the same technique. As already described, the ulnar aspect of metacarpal II and radial side of metacarpal III converge into a protuberance projecting proximally, a sort of styloid process. The extensor carpi radialis brevis inserts at this point (Rauber and Kopsch, 2003).
If the carpometacarpal joint line is drawn, this, together with the radiocarpal joint line, indicates the entire extent of the carpalia (▶ Fig. 4.28). The space between the two joint lines amounts to approximately two of the patient’s finger widths. This is the basis for locating the individual bones of the carpus on the dorsal aspect of the hand.
Once found, the joint line of the radiocarpal joint is the definitive orientation point for several manual therapy techniques. The angle of the radioulnar joint line as well as of the dorsopalmar joint line (palmar tilt) must therefore be found and observed. The illustrated example (▶ Fig. 4.29) demonstrates a translational technique at the radiocarpal joint that is used for assessment and treatment. Here, the proximal row of the carpus is pushed toward the radius in a palmar direction. In this case, the therapist tries to compensate for the palmar tilt using a support under the forearm so that an almost perpendicular push on the distal hand, in a palmar direction, can succeed.
After the dimensions of the carpus and its boundaries have become clear, the soft tissue (tendons, vessels, and nerves) is at the mid-point of the local orientation on the dorsal surface of the hand. The palpation again begins radially, finishes ulnarly, and reveals the exact position of the extensor tendons.
The patient’s hand and forearm are relaxed and rest on a supportive surface, which is as level as possible. The therapist generally sits to the side. The palm of the hand should face downward, enabling the dorsal and ulnar aspect of the wrist to be precisely palpated. If structures are being sought more on the radial side, the hand is positioned with the small finger downward.
A triangular depression can be found in the radial region of the carpus that has already been used as a starting position for the palpation of the boundary of the carpus. This depression is called the radial fossa, or the “anatomical snuffbox” (▶ Fig. 4.30). Therapists can easily observe and palpate swelling here caused by inflammation in the wrist.
Usually, the participating muscles must contract so that the position of the bordering tendons can be located and the radial fossa identified. The patient’s hand is positioned with the small finger downward, and the patient is instructed to move the thumb upward toward the ceiling (extension of the thumb).
The two tendons of the thumb extensors come closer to each other more distally. The structures of the radial column are found in the floor of this depression (scaphoid and trapezium; see ▶ Fig. 4.42 and ▶ Fig. 4.43).
The tendons of the long (extrinsic) muscles that move the hand and finger skeletons are held close to the radius and the ulna in their dorsal aspects at the side of the forearm by a thickening of the forearm fascia at the radius and ulna.
This extensor retinaculum maintains the position of all extensor tendons on the forearm skeleton, even during large rotary movements of the hand or forearm. The extensor retinaculum is attached to the bones between the respective tendon compartments, causing small osteofibrous canals to be formed for the passage of the tendons (▶ Fig. 4.15). Tendon sheaths protect the tendons from frictioning during movement.
The ulnar side of the patient’s hand is still positioned downward and the radial fossa is made distinct by moving the muscles of the thumb ( ▶ Fig. 4.31 and ▶ Fig. 4.32). The most palmar tendon bundle of the tendons shown here is located using transverse palpation. The patient then relaxes the thumb and the tendon bundle is followed proximally until the bony resistance of the radius is felt. This is the point where both tendons pass underneath the retinaculum through the first compartment. It lies directly over the radial styloid process.