4.1.1 Causes of the Diversity of Functions in the Hand

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.

  
  
  
  
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    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).

  
  
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  A stable bony center as the foundation for grasp.

  
  
  
  
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    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.

    
    
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    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.

    
    
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    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).

  
  
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  Pliancy of the palm.

  
  
  
  
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    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.

    
    
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    Moreover, the palm does not possess interfering muscle mass, in contrast to the short muscles in the sole of the foot.

    
    
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    Finally, the reinforced fascia of the hand (palmar aponeurosis) can be tightened by muscles designed especially for this purpose (palmaris longus).

  
  
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  Selective muscular control.

  
  
  
  
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    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).

4.1.2 Common Applications for Treatment in this Region

Hand symptoms constituting a therapeutic challenge are numerous and include almost the entire palette of postoperative, traumatic, and nontraumatic symptoms of the extremities.

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.

4.1.3 Required Basic Anatomical and Biomechanical Knowledge

Students require a certain amount of important background information to understand the instructions for local palpation:

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  The construction of the skeleton of the hand and fingers and, in particular, the name and position of the carpal bones and the longitudinal divisions of the hand.

  
  
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  The names and positions of the tendons that cross over the wrist.

  
  
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  The position and dimensions of the retinacula that keep the long tendons in the extensor compartments and the carpal tunnel.

  
  
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  The position and construction of narrow passages for peripheral nerves in the hand, in particular the carpal tunnel.

4.1.4 Axial Divisions of the Skeleton of the Hand into Columns and Their Clinical Significance

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:

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  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).

  
  
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  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.

  
  
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  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.

4.1.5 The Carpus

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).

4.1.6 Kinematic and Kinetic Model of the Hand

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).

In terms of kinematics, the biomechanical model of the carpus consists of two rigid parts moving toward each other with an intercalated segment:

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  The rigid parts are the proximal radius and the metacarpal bones including the distal carpal row.

  
  
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  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).

Ryu refers to this as the “four-unit concept”: distal carpal row plus the scaphoid, lunate, and triquetrum bones (Ryu and Klin, 2010).

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):

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  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.

  
  
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  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).

Hence, the lunate takes on a flexion tendency from radial and an extension tendency from ulnar, and if the intrinsic ligaments are intact, it remains neutral for flexion and extension.

Different types of trauma to the ligament and carpal instabilities of the hand sustained during a fall on the hand can be explained by this model.

4.1.7 Triangular Fibrocartilage Complex (TFC)

The stability of the ulnar carpus and the distal radioulnar joint is controlled by the TFC complex (▶ Fig. 4.9).

4.1.8 Construction of the Carpal Tunnel

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):

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  Radial: scaphoid tubercle and trapezium.

  
  
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  Ulnar: pisiform and the hook of hamate.

  
  
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  On the floor of the groove lie the lunate and capitate bones. The transverse carpal ligament encloses this carpal arch, forming the carpal tunnel.

  
  
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  Schmidt and Lanz (2003) give the diameter of the tunnel as between 8 and 12 mm.

The following structures pass through the carpal tunnel:

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  The four tendons of the flexor digitorum profundus (▶ Fig. 4.11).

  
  
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  The four tendons of the flexor digitorum superficialis (▶ Fig. 4.12).

  
  
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  The tendon of the flexor pollicis longus (▶ Fig. 4.13).

  
  
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  Median nerve (▶ Fig. 4.13 and ▶ Fig. 4.14).

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).

4.1.9 Extensor Tendons and their Compartments

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).

4.2.1 Summary of the Palpatory Process

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.

Starting Position

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.

Fig. 4.17 Topography of the bones—radial view.

Fig. 4.18 Palpation of the radius from a distal position.

Tip

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.

4.2.2 Palpation of Individual Structures

Proximal Boundary of the Carpus (Radiocarpal Joint Line)

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.

Technique

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.

Fig. 4.19 Palpation of the radial styloid process.

Fig. 4.20 Illustration of the palpation technique.

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).

Fig. 4.21 Distal radial radius.

Fig. 4.22 Palpation of the dorsal tubercle of the radius.

Fig. 4.23 Palpation of the distal radioulnar joint (DRUJ).

Fig. 4.24 Palpation of the distal head of the ulna and the ulnar styloid process.

Tip

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.

Alignment of the Radiocarpal Joint 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.

Fig. 4.25 Alignment of the radiocarpal joint space.

Distal Boundary of the Carpus (Carpometacarpal Joint Line)

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.

Technique

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.

Fig. 4.26 Searching for the carpometacarpal joint line.

Fig. 4.27 Carpometacarpal technique.

Tip

In our own experience, palpation is easier when it is initiated at metacarpal IV. The joint space felt there is somewhat wider and changes its size from radial to ulnar abduction.

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.

Fig. 4.28 Proximal and distal boundaries of the carpus.

Tip

If it is difficult to find the joint space at the level of metacarpals III and IV with very sharp fingertip palpation, it can be more easily found if the patient moves the hand in radial abduction. No other kind of movement of this not very moveable joint line is helpful for confirmation.

4.2.3 Tips for Assessment and Treatment

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.

Evidently, the position of the forearm on the supportive surface and the handling itself require correct knowledge of the position and alignment of the joint space and the articular bones.

4.3.1 Summary of the Palpatory Process

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.

4.3.2 Palpation of Individual Structures

Radial Fossa (Anatomical Snuffbox)

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.

Fig. 4.30 Position of the radial fossa.

The following structures form the boundaries of the radial fossa:

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  Proximal = distal radius.

  
  
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  Dorsal = extensor pollicis longus tendon (tendon compartment III).

  
  
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  Palmar = extensor pollicis brevis tendon (tendon compartment I).

Technique

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).

If the radial fossa is not yet obvious, the bordering extensor tendons of the thumb can be identified using a transverse palpation technique.

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).

Extensor Tendons and their Compartments

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 six canals through which the tendons pass are referred to as tendon compartments.

Technique

First Compartment

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.

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