Ausr. Radiol. (1979), 23. 158
Carpal Instability and Carpal Injuries BRONTE J. H O C K E Y , M.B.B.S., M.R.A.C.R. Senior Radiology Registrar, Department of Diagrlostic Radiology, The Queen Elizabeth Hospital, Woodville, 501 I , South Australia. INTRODUCTION Carpal injuries are relatively common, and are responsible for both acute and chronic disability. The radiological diagnosis may be subtle but extremely important in the successful management of these injuries. The patterns of severe fracture/ dislocations of the carpus are well known and are briefly discussed in this paper;however the concept of carpal instability or collapse deformity of the wrist is a poorly recognised entity and yet may result in significant problems for the patient. The overall understanding of these lesions depends on an appreciation of basic wrist mechanics. PATHOMECHANICSOF THE WRIST JOINT The carpus is a condyloid joint with two thirds of the movement of carpal extension occurring in the radiocarpal joint, and the remaining one third at the midcarpal joint, and as a result, the midcarpal joint suffers the main impact in hyperextension injuries. Thus, a hyperextension force on the heel of the hand is likely to result in distal radial fractures, and on the distal palm, results in scaphoid fractures or dislocations. Anatomically, the
FIGURE 1A. -The midcarpal joint of the carpus.
158
FIGURE lB.-Carpal ligaments - note the anterior radiocarpal ligament supporting the waist of the scaphoid.
FIGURE 2A.-Lateral
radiograph of the normal wrist.
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THIRD METACARPAL
"""'"TY \ \
FIGURE 2B.- Diagrammatic representation of the outlines of the carpal bones. The scaphoid is obliquely aligned at approximately 40"-60"to the long axis of the carpus.
midcarpal joint extends medially between the trapezium and trapezoid, and then between the scaphoid, capitate and across the carpus into the midcarpal joint (Figure 1A). The first metacarpal, the trapezium and the scaphoid remain as a supporting strut across the midcarpal joint. Severe hyperextension injuries may rupture the anterior radiocarpal, ulnar and radial collateral ligaments, the latter ligaments often avulsing the corresponding styloid processes (Figure 1B). In addition, these injuries may rupture the scapholunate interosseous ligament, and the scaphoid capsular attachments resulting in scapholunate dissociation without apparent bony injury or dislocation. The normal appearances of the carpal bones on a lateral radiograph of the hand in the neutral position is demonstrated in Figures 2A and 2B. Superimposition of the individual carpal bones adds to the complexity of this view. However the important relationships are those of the lunate, scaphoid and capitate to the longitudinal axis of the carpus. During radial deviation,
FIGURES 3A & B.-P.A. radiographs in full radial and ulnar deviation. Note that the scapholunate gap remams unchanged and the distal pole of the scaphoid produces a "ring sign" (arrowed) in full radial deviation indicating scaphoid rotation. Australasim Radiology, Vol. XXIII. No. 2. July, 1979 159
B. J. HOCKLEY
FIGURES 4A & B.-Penlunar dislocation FIGURE 4A.-LateraJ radiograph - the h a t e articulates with the radius; the capitate and other carpal bones are dislocated dorsally.
FIGURE 4B. -P.A. radiograph - note the overlap of the capitate over the outline of the lunate.
the scaphoid rotates anteriorly so as to avoid 3. Dislocations and fracture/dislocations. impinging on the radial styloid process. Therefore (a) Lunate or perilunate. on the P.A. projections, radial deviation produces (b) Transscaphoid perilunate. foreshortening of the scaphoid and results in (c) Rare individual carpal bone dislocations. superimposition of the distal pole over the body 4. Lunate fractures and other individual carpal of the scaphoid. The circular cortical outline of bone fractures. the distal pole that results resembles a “ring-sign’’ 5. Carpal collapse deformities. as described in subluxation of the scaphoid (Hudson el a1 1972) and is secondary to palmar flexion The most common carpal injuries are scaphoid of this bone (Figures 3A and B). It should also be noted that flexion and extension of the wrist fractures and account for approximately 60-7m alters the relationships of the carpal bones, and of carpal injuries. The dislocations/subluxations specifically, rotation of the scaphoid occurs and collapse deformities of the carpus comprise anteriorly in flexion, and posteriorly in extension. a further 10%. Dorsal flake fractures, lunate Thus the movements of the carpal bones are fractures and rare fracture/dislocations of the complex and the position of individual bones other carpal bones account for the remainder depends principally on the position of the hand. @cckwwd and Green). Perilunar and transscaphoidperilunar dislocations (Figures 4 & 5 ) are the most frequent carpal dislocations. The site of impact CLASSIFICATION OF CARPAL INJURIES and the degree of radial deviation of the hand (Modified from Rockwood and Green) during the hyperextension injury determines 1. Scaphoid fracture. which type of injury is likely to occur. Character2. Dorsal flake fracture. istically, the carpus dislocates dorsally around the
160
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CARPAL INSTABILITY AND CARPAL INJURIES surface of the triquetrum. They are noted on lateral radiographs and are highlighted by lateral projections in flexion. P.A. radiographs for this injury often fail to disclose the fracture and in most cases these injuries result in minimal disability. Rarely patients have been described developing carpal collapse. Scaphoid subluxations-dislocations (Boyes 1977 and Hudson et 01 1976) are rare but are easily missed on radiological examination. Scaphoid subluxations may be recognised as a primary traumatic event or as a secondary feature of the unstable carpus and carpal collapse deformities. In scaphoid subluxationsdislocations, there is usually evidence of scapholunate dissociation and displacement of the scaphoid. Scaphoid subluxations typically demonstrate anterior rotation of the scaphoid which appears more horizontally orientated on the lateral radiograph of the wrist (Figure 7). Scaphoid dislocations are usually anterior out of the carpus (Figure 8) and both these types of injuries are frequently unstable following reduction. Failure to recognise either of these lesions may result in severe wrist disability (Figure 9).
FIGURES 5 A & B. -Transscaphoid perilunar dislocation. The h a t e and proximal half of the scaphoid articulates with the radius and the remainder of the carpus is dislocated dorsally. (Arrowed.)
h a t e and is known as a perilunar dislocation. A transscaphoid-perilunar dislocation has, in addition to the carpal dislocation, a fracture of the waist of the scaphoid and dorsal displacement of the distal pole. Rarely, the converse injury may occur with anterior dislocation of the lunate and proximal pole of the scaphoid. In any of the severe dislocations of the carpus there may be associated fractures of the ulnar and radial styloid processes, dorsal tubercle of the radius and the triquetrum. Lunate dislocations (Figure 6) are commonly anterior and if displacement is severe, then avascular necrosis may result due to rupture of capsular attachments. Otherwise there is little difference in the immediate management and sequelae of both h a t e and perilunate dislocations and separating them for descriptive purposes is of debatable significance (Rockwood and Green). Dorsal chip fractures are relatively frequent and usually represent avulsed fragments from the dorsal Australasian Radiology, Vol. XXIII, No. 2, July, 1979
CARPAL INSTABILITY AND COLLAPSE DEFORMITIES The concept of carpal instability was first proposed by Gilford and associates in 1943 when they described the collapse of the carpus when it loses its supporting elements. The supporting elements which maintain carpal stability include the ligaments, the articulating bones, the tendons and the joint capsule. Particularly, the scaphoid and the anterior radiocarpal ligament are the most important stabilising factors and if either is damaged, the carpus may collapse or crumple in a “zig zag” or “concertina” type of deformity as viewed on the lateral radiograph. This can be further appreciated if the carpus is considered as a series of bones arranged in a link system which would crumple if there was no lateral supporting rod to maintain length. The function of the scaphoid is to act as this connecting rod linking the two carpal rows and bracing the mid carpal joint, particularly when carpal movement occurs. The function of the scaphoid can be described as a “slider-crank’’ mechanism, an engineering principle which converts reciprocating movement into rotatory movement and is well demonstrated in the driving wheels of a steam engine. The patterns of carpal collapse have been classified by Linscheid et 01 (1971) into two major types:1. Dorsiflexion carpal instability. 161
B. J . HOCKLEY
FIGURES 6A & B. - Lunate dislocation. FIGURE 6A.-Lateral radiograph - anterior displacement of the lunate (arrowed).
FIGURES 7A& 8.- Rotatory subluxationof the scaphoid. FIGURE 7A. - P.A. radiograph - note the “ring sign” indicating scaphoid rotation in the absence of radial deviation of the hand and the widened scapholunate gap.
162
FIGURE 6B.-P.A. radiograph - note the triangular shape indicating h a t e rotation (arrowed).
note the horizontal FIGURE 7B. Lateral radiograph alignment of the scaphoid across the carpus. -
-
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FIGURE 8. - Scaphoid dislocation
- the
scaphoid is dislocated anteriorly.
FIGURE 9. -Missed scaphoid subluxation
-
three months after injury with disuse osteoporosis.
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7 0 ‘
FIGURE 10.-Diagrammatic representation of a lateral radiograph of the normal wrist demonstrating the axes of the scaphoid, lunate and capitate, and the normal scapholunate angle - range 40”-70”.
2. Palmarflexion carpal instability. Dorsiflexion carpal collapse describes a crumpling deformity directed dorsally with a hump on the dorsum of the wrist. Palmarflexion collapse represents the converse arrangement, where the crumpling deformity is directed anteriorly. The clinical symptoms of these collapse patterns include wrist pain, particularly during movement, clicking, crepitus, or deformity. Some patients present with “carpal tunnel” syndrome or wrist sprains. Many patients have a history of trauma which may be minor and repetitive and yet others have no history of trauma that they regard as relevant. Clinical examination may demonstrate a local hump deformity on the dorsum of the wrist or tenderness distal to Lister’s tubercle.
RADIOLOGICALDIAGNOSIS Plain Films Six standard projections can be used to aid in the diagnosis of carpal instability. In the posteroanterior position, projections of the wrist should be performed with the hand in the neutral position, full radial and ulnar deviation. Similarly, the lateral 164
FIGURES 11A & B.-Dorsiflexion carpal collapse. The concavity of the lunate is directed dorsally (arowed); the scapholunateangle is greater than 70”.
radiographs should include three projections with the wrist in the neutral position, full flexion and extension. The neutral position should be accurate with less than 20 degrees of dorsiflexion or less than five degrees of palmar flexion of the third metacarpal in relation to the longitudinal axis of the radius. The radiological features of importance are: I. P.A. Projection (a) The scapholunate gap should be no greater than 2mm. Measurements greater than 34mm are highly suggestive of scapholunate dissociation and the gap has been referred to as the “Terry Thomas” sign in scaphoid subluxation. P.A. projections in full radial and ulnar deviation may show increased widening indicating definite scapholunate dissociation. Full ulnar deviation may be the only projection which opens up the scapholunate gapAustralasian Radiology, Vol. XXIII, No. 2, July, 1979
CARPAL INSTABILITY AND CARPAL INJURIES
FIGURE 11B
(b) Foreshortening of the scaphoid with a ‘‘ring’’ sign. (c) An abnormal h a t e configuration indicating small degrees of dorsal or palmar rotation of the lunate. 11. The Lateral Projection The longitudinal axis of the radius, h a t e and the third metacarpal should form a straight line when the hand is held in neutrality. To make appropriate angle measurements, lines are drawn along the longitudinal axes of the lunate, scaphoid and capitate and the following angles can be measured in the normal wrist (Figure 10). (a) Scapholunate angle - this is usually in the range of 40-70 degrees in normal wrists, with an average of 47 degrees. (b) radiolunate angle - usually less than 15 degrees. (c) capitolunate angle - usually less than 15 degrees. The collapse patterns can be assessed using these normal angle measurements. Dorsiflexion carpal collapse (Figures 1IA &B). (a) scapholunate angle greater than 70 degrees (b) radiolunate angle greater than 15 degrees (c) capitolunate angle greater than 15,degrees. Australasian Radiology, Vol. XXIII. No. 2, July, 1979
FIGURES 12A & B.-Palmarfkxion carpal collapse. There is palmar rotation of the lunate relative to the radius, and the scapholunate angle is less than 40“.
Palmar flexion carpal collapse (Figures 12A & B).
(a) the scapholunate angle less than 40 degrees (b) capitolunate angle greater than 10 degrees. These angle measurements on the lateral radiographs can be supplemented by manual compression of the carpus so as to accentuate the collapse deformity. This can also be useful in patients who can voluntarily deform the wrist (trick wrists). Therefore, in dorsiflexion carpal collapse, the scaphoid assumes a horizontal position and the h a t e articular surface faces dorsally. Conversely, in palmar flexion collapse, the lunate inclines palmarly with minimal change in the position of the scaphoid. Palmar-flexion instability is less common than dorsiflexion instability and is usually diagnosed only on the lateral projections, as the scaphotunate gap on the P.A. projection is 165
B. J. HOCKLEY
FIGURE 13.-Dorsiflexion carpal collapse of trauma.
FIGURE 12B
-
no history
Summary of Radiography 1. P.A. (a) full radial deviation (b) neutral position (c) full ulnar deviation 2. Lateral (a) neutral position with less than 20 degrees of dorsiflexion or less than 5 degrees of palmar flexion of the hand. (b) full flexion (c) full extension 3. Pronation and supination in the PA.position. 4. Lateral projections of the wrist with manual compression of the carpus. 5. Motion studies with cinefluoroscopy - may be useful in difficult diagnostic cases. 6. Arthography - rarely required.
often normal. Again it is emphasised that the hand must be in the neutral position t o make accurate angle measurements.
DISCUSSION Carpal collapse is usually a sequel of trauma.
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FIGURE 14.-Doniflexion carpal collapse and secondary degenerative changes in the thumb-axisand radiocarpal joints. Note the widened scapholunate gap. This patient presented with “carpal tunnel” syndromc.
However the aetiology may be subdivided into three main groups. (a) post-traumatic (b) post-arthritic (c) Congenital ligament laxity. Post-arthritic collapse patterns are usually noted in rheumatoid arthritis and rare examples can be demonstrated in patients with ligament laxity of their wrists. Acute post-traumatic carpal instability may occur with or without associated fracturedislocations of the carpus (Linscheid et al 1972). The natural development of carpal collapse may be immediately obvious following trauma. However it is usually slowly progressive over months and years, and the diagnosis may require serial examinations before being apparent (Linscheid et a2 1974). A negative examination does not preclude the diagnosis, and as the radiographic signs are subtle, progress examinations are often necessary for early diagnosis. The collapse pattern is usually of the dorsiflexion variety. (Figure 13) However palmarflexion collapse can occur following trauma. Austrahsian Radiology, VoL XXIII, No. 2. July. 1 9 79
Failure to appreciate this lesion may result in severe degenerative changes in the carpus particularly affecting the thumb-axis and radio-carpal joints. These changes are secondary to chronic collapse patterns but have been poorly recognised as such in the past, and frequently interpreted as simple “wear and tear” arthritis (Figure 14). The degenerative changes are mainly the result of rnalalignment of the scaphoid and abnormal stresses in its articulations on the lateral side of the carpus. These degenerative changes are common in chronic rheumatoid arthritis (CowanCollins et a2 1972) where ligament degeneration allows carpal collapse to occur (Figure 15). Non-union of the scaphoid that is associated with pain and disability typically develops degenerative changes in these lateral carpal joints and are secondary to dorsal collapse deformities. Fisk (1970) postulated that the aetiology of non-union is secondary to carpal instability with abnormal stresses occurring at the scaphoid fracture line. Therefore, the emphasis of this paper is in the early diagnosis of these collapse deformities, and particularly it should be appreciated that acute post-traumatic carpal instability without associated 167
B. J. HOCKLEY bony injury has the same propensity for producing disabling degenerative change as the scaphoid fracture, and should be treated accordingly. The rotatory subluxation of the scaphoid is probably another form of expression of the unstable carpus where rupture of the scapholunate ligament allows palmar or anterior rotation of the scaphoid. As a result, this scaphoid injury may result in a chronic carpal collapse deformity and secondary chronic degenerative change. Carpal collapse deformities should always be considered in patients who present with acute “wrist sprains”, negative radiological examinations for clinically suspected scaphoid fractures, “carpal tunnel” syndrome and “clicking wrists”. Particularly, the collapse deformities can be demonstrated in patients with no obvious history of trauma. However, many are engaged in manual labour occupations with repetitive minor trauma (Figure 16). Carpal instability can be treated by repair of the anterior radiocarpal and scapholunate interosseous ligaments. This usually involves the use of Kirschner wires across the lunate and scaphoid, and reconstruction of the anterior supporting ligaments of the carpus. Lunate and scaphoid to relieve the disabling FIGURE lS.-Palmarflexion carpalcollapse in rheumatoid prostheses Can be arthritis. The mncavity of the lunate is directed palmarly. symptoms of the secondary degenerative arthritis.
FIGURE 16.-Dorsiflexion carpal collapse - note the degenerative cysts at the site of insertion of the scapholunate ligament. Occupation - manual labourer and had used pneumatic drills.
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CARPAL INSTABILITY AND CARPAL INJURIES SUMMARY Carpal instability or collapse deformities of the carpus are a poorly recognised radiological entity. The spectrum of these lesions includes painful non-united scaphoid fractures, rotatory subluxations of the scaphoid, post-arthritic degenerative changes and acute “wrist sprains”. The collapse patterns can be subdivided into two types:Dorsiflexion carpal instability Palmarflexion carpal instability. In the acute form, the radiological appearances may be non-specific if normal carpal relationships are maintained in standard wrist projections. The use of six standard projections is advocated in diagnosis with accurate lateral radiographs and with the hand in a true neutral position. Serial examinations may be required to make the diagnosis, possibly augmented with lateral views using carpal compression or motion studies of the wrist. Patients with acute and chronic “wrist sprains” and “carpal tunnel” syndrome should be energeticd y investigated with the purpose of diagnosing collapse deformities and instituting the appropriate orthopaedic treatment .
ACKNOWLEDGEMENTS In the preparation of this paper I wish to thank
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Miss P. Parsons for her clerical assistance and Mr. Oleg Hetman for his photographic expertise. I also wish to thank Dr. G . Davies and Dr. B. Parkinson for the use of some of their radiological material.
REFERENCES 1. Boyes, J. (1977): “Wrist sprain with subluxation of the scaphoid.” Amer. Fam. Physician, 15 : 149-151. 2. CowanCollin& L., Lidsky, M. D., Sharp, J. T. and Moreland, L. (1972): “Malposition of Carpal Bones in Rheumatoid Arthritis” Radiology, 103 : 95-98. 3. Fisk, G. R. (1970): “Carpal Instability and the Fractured Scaphoid.” Ann Roy. Coll. Surg. 46 : 63-16. 4. Gilford, W. W., Bolton, R. H. and Lambrinudi, C. (1943): ‘The Mechanism of the Wrist Joint with Special Reference to the Fractures of the Scaphoid.” Guy. Hosp. Rep. 92 : 52-59. 5. Hudson, T. M., Caragol, W. J. and Kaye, J. J. (1976): “Isolated Rotatory Subluxation of the Carpat Navicular.” Amer. J. RoentgenoL 126 : 3.601-611. 6. Linscheid, R. L., Dobyns, J. H., Beabout, J. W. and Bryan, R. S. (1972): ‘Traumatic Instability of the Wrist.”J. Bone Joint Swg. MA : 1612-1632. 7. Rockwood and Green. “Fractures.” Vol. I. 8. SebaId, J. R., Dobyns, J. H. and Linscheid. R. L. (1974): ‘The Natural History of Collapse Deformities of the Wrist.” Chn Orthopredics & Related Research, 104 : 140-148.
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Carpal Instability and Carpal Injuries BRONTE J. H O C K E Y , M.B.B.S., M.R.A.C.R. Senior Radiology Registrar, Department of Diagrlostic Radiology, The Queen Elizabeth Hospital, Woodville, 501 I , South Australia. INTRODUCTION Carpal injuries are relatively common, and are responsible for both acute and chronic disability. The radiological diagnosis may be subtle but extremely important in the successful management of these injuries. The patterns of severe fracture/ dislocations of the carpus are well known and are briefly discussed in this paper;however the concept of carpal instability or collapse deformity of the wrist is a poorly recognised entity and yet may result in significant problems for the patient. The overall understanding of these lesions depends on an appreciation of basic wrist mechanics. PATHOMECHANICSOF THE WRIST JOINT The carpus is a condyloid joint with two thirds of the movement of carpal extension occurring in the radiocarpal joint, and the remaining one third at the midcarpal joint, and as a result, the midcarpal joint suffers the main impact in hyperextension injuries. Thus, a hyperextension force on the heel of the hand is likely to result in distal radial fractures, and on the distal palm, results in scaphoid fractures or dislocations. Anatomically, the
FIGURE 1A. -The midcarpal joint of the carpus.
158
FIGURE lB.-Carpal ligaments - note the anterior radiocarpal ligament supporting the waist of the scaphoid.
FIGURE 2A.-Lateral
radiograph of the normal wrist.
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THIRD METACARPAL
"""'"TY \ \
FIGURE 2B.- Diagrammatic representation of the outlines of the carpal bones. The scaphoid is obliquely aligned at approximately 40"-60"to the long axis of the carpus.
midcarpal joint extends medially between the trapezium and trapezoid, and then between the scaphoid, capitate and across the carpus into the midcarpal joint (Figure 1A). The first metacarpal, the trapezium and the scaphoid remain as a supporting strut across the midcarpal joint. Severe hyperextension injuries may rupture the anterior radiocarpal, ulnar and radial collateral ligaments, the latter ligaments often avulsing the corresponding styloid processes (Figure 1B). In addition, these injuries may rupture the scapholunate interosseous ligament, and the scaphoid capsular attachments resulting in scapholunate dissociation without apparent bony injury or dislocation. The normal appearances of the carpal bones on a lateral radiograph of the hand in the neutral position is demonstrated in Figures 2A and 2B. Superimposition of the individual carpal bones adds to the complexity of this view. However the important relationships are those of the lunate, scaphoid and capitate to the longitudinal axis of the carpus. During radial deviation,
FIGURES 3A & B.-P.A. radiographs in full radial and ulnar deviation. Note that the scapholunate gap remams unchanged and the distal pole of the scaphoid produces a "ring sign" (arrowed) in full radial deviation indicating scaphoid rotation. Australasim Radiology, Vol. XXIII. No. 2. July, 1979 159
B. J. HOCKLEY
FIGURES 4A & B.-Penlunar dislocation FIGURE 4A.-LateraJ radiograph - the h a t e articulates with the radius; the capitate and other carpal bones are dislocated dorsally.
FIGURE 4B. -P.A. radiograph - note the overlap of the capitate over the outline of the lunate.
the scaphoid rotates anteriorly so as to avoid 3. Dislocations and fracture/dislocations. impinging on the radial styloid process. Therefore (a) Lunate or perilunate. on the P.A. projections, radial deviation produces (b) Transscaphoid perilunate. foreshortening of the scaphoid and results in (c) Rare individual carpal bone dislocations. superimposition of the distal pole over the body 4. Lunate fractures and other individual carpal of the scaphoid. The circular cortical outline of bone fractures. the distal pole that results resembles a “ring-sign’’ 5. Carpal collapse deformities. as described in subluxation of the scaphoid (Hudson el a1 1972) and is secondary to palmar flexion The most common carpal injuries are scaphoid of this bone (Figures 3A and B). It should also be noted that flexion and extension of the wrist fractures and account for approximately 60-7m alters the relationships of the carpal bones, and of carpal injuries. The dislocations/subluxations specifically, rotation of the scaphoid occurs and collapse deformities of the carpus comprise anteriorly in flexion, and posteriorly in extension. a further 10%. Dorsal flake fractures, lunate Thus the movements of the carpal bones are fractures and rare fracture/dislocations of the complex and the position of individual bones other carpal bones account for the remainder depends principally on the position of the hand. @cckwwd and Green). Perilunar and transscaphoidperilunar dislocations (Figures 4 & 5 ) are the most frequent carpal dislocations. The site of impact CLASSIFICATION OF CARPAL INJURIES and the degree of radial deviation of the hand (Modified from Rockwood and Green) during the hyperextension injury determines 1. Scaphoid fracture. which type of injury is likely to occur. Character2. Dorsal flake fracture. istically, the carpus dislocates dorsally around the
160
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CARPAL INSTABILITY AND CARPAL INJURIES surface of the triquetrum. They are noted on lateral radiographs and are highlighted by lateral projections in flexion. P.A. radiographs for this injury often fail to disclose the fracture and in most cases these injuries result in minimal disability. Rarely patients have been described developing carpal collapse. Scaphoid subluxations-dislocations (Boyes 1977 and Hudson et 01 1976) are rare but are easily missed on radiological examination. Scaphoid subluxations may be recognised as a primary traumatic event or as a secondary feature of the unstable carpus and carpal collapse deformities. In scaphoid subluxationsdislocations, there is usually evidence of scapholunate dissociation and displacement of the scaphoid. Scaphoid subluxations typically demonstrate anterior rotation of the scaphoid which appears more horizontally orientated on the lateral radiograph of the wrist (Figure 7). Scaphoid dislocations are usually anterior out of the carpus (Figure 8) and both these types of injuries are frequently unstable following reduction. Failure to recognise either of these lesions may result in severe wrist disability (Figure 9).
FIGURES 5 A & B. -Transscaphoid perilunar dislocation. The h a t e and proximal half of the scaphoid articulates with the radius and the remainder of the carpus is dislocated dorsally. (Arrowed.)
h a t e and is known as a perilunar dislocation. A transscaphoid-perilunar dislocation has, in addition to the carpal dislocation, a fracture of the waist of the scaphoid and dorsal displacement of the distal pole. Rarely, the converse injury may occur with anterior dislocation of the lunate and proximal pole of the scaphoid. In any of the severe dislocations of the carpus there may be associated fractures of the ulnar and radial styloid processes, dorsal tubercle of the radius and the triquetrum. Lunate dislocations (Figure 6) are commonly anterior and if displacement is severe, then avascular necrosis may result due to rupture of capsular attachments. Otherwise there is little difference in the immediate management and sequelae of both h a t e and perilunate dislocations and separating them for descriptive purposes is of debatable significance (Rockwood and Green). Dorsal chip fractures are relatively frequent and usually represent avulsed fragments from the dorsal Australasian Radiology, Vol. XXIII, No. 2, July, 1979
CARPAL INSTABILITY AND COLLAPSE DEFORMITIES The concept of carpal instability was first proposed by Gilford and associates in 1943 when they described the collapse of the carpus when it loses its supporting elements. The supporting elements which maintain carpal stability include the ligaments, the articulating bones, the tendons and the joint capsule. Particularly, the scaphoid and the anterior radiocarpal ligament are the most important stabilising factors and if either is damaged, the carpus may collapse or crumple in a “zig zag” or “concertina” type of deformity as viewed on the lateral radiograph. This can be further appreciated if the carpus is considered as a series of bones arranged in a link system which would crumple if there was no lateral supporting rod to maintain length. The function of the scaphoid is to act as this connecting rod linking the two carpal rows and bracing the mid carpal joint, particularly when carpal movement occurs. The function of the scaphoid can be described as a “slider-crank’’ mechanism, an engineering principle which converts reciprocating movement into rotatory movement and is well demonstrated in the driving wheels of a steam engine. The patterns of carpal collapse have been classified by Linscheid et 01 (1971) into two major types:1. Dorsiflexion carpal instability. 161
B. J . HOCKLEY
FIGURES 6A & B. - Lunate dislocation. FIGURE 6A.-Lateral radiograph - anterior displacement of the lunate (arrowed).
FIGURES 7A& 8.- Rotatory subluxationof the scaphoid. FIGURE 7A. - P.A. radiograph - note the “ring sign” indicating scaphoid rotation in the absence of radial deviation of the hand and the widened scapholunate gap.
162
FIGURE 6B.-P.A. radiograph - note the triangular shape indicating h a t e rotation (arrowed).
note the horizontal FIGURE 7B. Lateral radiograph alignment of the scaphoid across the carpus. -
-
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CARPAL INSTABILITY AND CARPAL INJURIES
FIGURE 8. - Scaphoid dislocation
- the
scaphoid is dislocated anteriorly.
FIGURE 9. -Missed scaphoid subluxation
-
three months after injury with disuse osteoporosis.
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B. J. HOCKLEY
7 0 ‘
FIGURE 10.-Diagrammatic representation of a lateral radiograph of the normal wrist demonstrating the axes of the scaphoid, lunate and capitate, and the normal scapholunate angle - range 40”-70”.
2. Palmarflexion carpal instability. Dorsiflexion carpal collapse describes a crumpling deformity directed dorsally with a hump on the dorsum of the wrist. Palmarflexion collapse represents the converse arrangement, where the crumpling deformity is directed anteriorly. The clinical symptoms of these collapse patterns include wrist pain, particularly during movement, clicking, crepitus, or deformity. Some patients present with “carpal tunnel” syndrome or wrist sprains. Many patients have a history of trauma which may be minor and repetitive and yet others have no history of trauma that they regard as relevant. Clinical examination may demonstrate a local hump deformity on the dorsum of the wrist or tenderness distal to Lister’s tubercle.
RADIOLOGICALDIAGNOSIS Plain Films Six standard projections can be used to aid in the diagnosis of carpal instability. In the posteroanterior position, projections of the wrist should be performed with the hand in the neutral position, full radial and ulnar deviation. Similarly, the lateral 164
FIGURES 11A & B.-Dorsiflexion carpal collapse. The concavity of the lunate is directed dorsally (arowed); the scapholunateangle is greater than 70”.
radiographs should include three projections with the wrist in the neutral position, full flexion and extension. The neutral position should be accurate with less than 20 degrees of dorsiflexion or less than five degrees of palmar flexion of the third metacarpal in relation to the longitudinal axis of the radius. The radiological features of importance are: I. P.A. Projection (a) The scapholunate gap should be no greater than 2mm. Measurements greater than 34mm are highly suggestive of scapholunate dissociation and the gap has been referred to as the “Terry Thomas” sign in scaphoid subluxation. P.A. projections in full radial and ulnar deviation may show increased widening indicating definite scapholunate dissociation. Full ulnar deviation may be the only projection which opens up the scapholunate gapAustralasian Radiology, Vol. XXIII, No. 2, July, 1979
CARPAL INSTABILITY AND CARPAL INJURIES
FIGURE 11B
(b) Foreshortening of the scaphoid with a ‘‘ring’’ sign. (c) An abnormal h a t e configuration indicating small degrees of dorsal or palmar rotation of the lunate. 11. The Lateral Projection The longitudinal axis of the radius, h a t e and the third metacarpal should form a straight line when the hand is held in neutrality. To make appropriate angle measurements, lines are drawn along the longitudinal axes of the lunate, scaphoid and capitate and the following angles can be measured in the normal wrist (Figure 10). (a) Scapholunate angle - this is usually in the range of 40-70 degrees in normal wrists, with an average of 47 degrees. (b) radiolunate angle - usually less than 15 degrees. (c) capitolunate angle - usually less than 15 degrees. The collapse patterns can be assessed using these normal angle measurements. Dorsiflexion carpal collapse (Figures 1IA &B). (a) scapholunate angle greater than 70 degrees (b) radiolunate angle greater than 15 degrees (c) capitolunate angle greater than 15,degrees. Australasian Radiology, Vol. XXIII. No. 2, July, 1979
FIGURES 12A & B.-Palmarfkxion carpal collapse. There is palmar rotation of the lunate relative to the radius, and the scapholunate angle is less than 40“.
Palmar flexion carpal collapse (Figures 12A & B).
(a) the scapholunate angle less than 40 degrees (b) capitolunate angle greater than 10 degrees. These angle measurements on the lateral radiographs can be supplemented by manual compression of the carpus so as to accentuate the collapse deformity. This can also be useful in patients who can voluntarily deform the wrist (trick wrists). Therefore, in dorsiflexion carpal collapse, the scaphoid assumes a horizontal position and the h a t e articular surface faces dorsally. Conversely, in palmar flexion collapse, the lunate inclines palmarly with minimal change in the position of the scaphoid. Palmar-flexion instability is less common than dorsiflexion instability and is usually diagnosed only on the lateral projections, as the scaphotunate gap on the P.A. projection is 165
B. J. HOCKLEY
FIGURE 13.-Dorsiflexion carpal collapse of trauma.
FIGURE 12B
-
no history
Summary of Radiography 1. P.A. (a) full radial deviation (b) neutral position (c) full ulnar deviation 2. Lateral (a) neutral position with less than 20 degrees of dorsiflexion or less than 5 degrees of palmar flexion of the hand. (b) full flexion (c) full extension 3. Pronation and supination in the PA.position. 4. Lateral projections of the wrist with manual compression of the carpus. 5. Motion studies with cinefluoroscopy - may be useful in difficult diagnostic cases. 6. Arthography - rarely required.
often normal. Again it is emphasised that the hand must be in the neutral position t o make accurate angle measurements.
DISCUSSION Carpal collapse is usually a sequel of trauma.
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FIGURE 14.-Doniflexion carpal collapse and secondary degenerative changes in the thumb-axisand radiocarpal joints. Note the widened scapholunate gap. This patient presented with “carpal tunnel” syndromc.
However the aetiology may be subdivided into three main groups. (a) post-traumatic (b) post-arthritic (c) Congenital ligament laxity. Post-arthritic collapse patterns are usually noted in rheumatoid arthritis and rare examples can be demonstrated in patients with ligament laxity of their wrists. Acute post-traumatic carpal instability may occur with or without associated fracturedislocations of the carpus (Linscheid et al 1972). The natural development of carpal collapse may be immediately obvious following trauma. However it is usually slowly progressive over months and years, and the diagnosis may require serial examinations before being apparent (Linscheid et a2 1974). A negative examination does not preclude the diagnosis, and as the radiographic signs are subtle, progress examinations are often necessary for early diagnosis. The collapse pattern is usually of the dorsiflexion variety. (Figure 13) However palmarflexion collapse can occur following trauma. Austrahsian Radiology, VoL XXIII, No. 2. July. 1 9 79
Failure to appreciate this lesion may result in severe degenerative changes in the carpus particularly affecting the thumb-axis and radio-carpal joints. These changes are secondary to chronic collapse patterns but have been poorly recognised as such in the past, and frequently interpreted as simple “wear and tear” arthritis (Figure 14). The degenerative changes are mainly the result of rnalalignment of the scaphoid and abnormal stresses in its articulations on the lateral side of the carpus. These degenerative changes are common in chronic rheumatoid arthritis (CowanCollins et a2 1972) where ligament degeneration allows carpal collapse to occur (Figure 15). Non-union of the scaphoid that is associated with pain and disability typically develops degenerative changes in these lateral carpal joints and are secondary to dorsal collapse deformities. Fisk (1970) postulated that the aetiology of non-union is secondary to carpal instability with abnormal stresses occurring at the scaphoid fracture line. Therefore, the emphasis of this paper is in the early diagnosis of these collapse deformities, and particularly it should be appreciated that acute post-traumatic carpal instability without associated 167
B. J. HOCKLEY bony injury has the same propensity for producing disabling degenerative change as the scaphoid fracture, and should be treated accordingly. The rotatory subluxation of the scaphoid is probably another form of expression of the unstable carpus where rupture of the scapholunate ligament allows palmar or anterior rotation of the scaphoid. As a result, this scaphoid injury may result in a chronic carpal collapse deformity and secondary chronic degenerative change. Carpal collapse deformities should always be considered in patients who present with acute “wrist sprains”, negative radiological examinations for clinically suspected scaphoid fractures, “carpal tunnel” syndrome and “clicking wrists”. Particularly, the collapse deformities can be demonstrated in patients with no obvious history of trauma. However, many are engaged in manual labour occupations with repetitive minor trauma (Figure 16). Carpal instability can be treated by repair of the anterior radiocarpal and scapholunate interosseous ligaments. This usually involves the use of Kirschner wires across the lunate and scaphoid, and reconstruction of the anterior supporting ligaments of the carpus. Lunate and scaphoid to relieve the disabling FIGURE lS.-Palmarflexion carpalcollapse in rheumatoid prostheses Can be arthritis. The mncavity of the lunate is directed palmarly. symptoms of the secondary degenerative arthritis.
FIGURE 16.-Dorsiflexion carpal collapse - note the degenerative cysts at the site of insertion of the scapholunate ligament. Occupation - manual labourer and had used pneumatic drills.
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CARPAL INSTABILITY AND CARPAL INJURIES SUMMARY Carpal instability or collapse deformities of the carpus are a poorly recognised radiological entity. The spectrum of these lesions includes painful non-united scaphoid fractures, rotatory subluxations of the scaphoid, post-arthritic degenerative changes and acute “wrist sprains”. The collapse patterns can be subdivided into two types:Dorsiflexion carpal instability Palmarflexion carpal instability. In the acute form, the radiological appearances may be non-specific if normal carpal relationships are maintained in standard wrist projections. The use of six standard projections is advocated in diagnosis with accurate lateral radiographs and with the hand in a true neutral position. Serial examinations may be required to make the diagnosis, possibly augmented with lateral views using carpal compression or motion studies of the wrist. Patients with acute and chronic “wrist sprains” and “carpal tunnel” syndrome should be energeticd y investigated with the purpose of diagnosing collapse deformities and instituting the appropriate orthopaedic treatment .
ACKNOWLEDGEMENTS In the preparation of this paper I wish to thank
Australasian Radiology, Vol. XXIII, No. 2, July. 1979
Miss P. Parsons for her clerical assistance and Mr. Oleg Hetman for his photographic expertise. I also wish to thank Dr. G . Davies and Dr. B. Parkinson for the use of some of their radiological material.
REFERENCES 1. Boyes, J. (1977): “Wrist sprain with subluxation of the scaphoid.” Amer. Fam. Physician, 15 : 149-151. 2. CowanCollin& L., Lidsky, M. D., Sharp, J. T. and Moreland, L. (1972): “Malposition of Carpal Bones in Rheumatoid Arthritis” Radiology, 103 : 95-98. 3. Fisk, G. R. (1970): “Carpal Instability and the Fractured Scaphoid.” Ann Roy. Coll. Surg. 46 : 63-16. 4. Gilford, W. W., Bolton, R. H. and Lambrinudi, C. (1943): ‘The Mechanism of the Wrist Joint with Special Reference to the Fractures of the Scaphoid.” Guy. Hosp. Rep. 92 : 52-59. 5. Hudson, T. M., Caragol, W. J. and Kaye, J. J. (1976): “Isolated Rotatory Subluxation of the Carpat Navicular.” Amer. J. RoentgenoL 126 : 3.601-611. 6. Linscheid, R. L., Dobyns, J. H., Beabout, J. W. and Bryan, R. S. (1972): ‘Traumatic Instability of the Wrist.”J. Bone Joint Swg. MA : 1612-1632. 7. Rockwood and Green. “Fractures.” Vol. I. 8. SebaId, J. R., Dobyns, J. H. and Linscheid. R. L. (1974): ‘The Natural History of Collapse Deformities of the Wrist.” Chn Orthopredics & Related Research, 104 : 140-148.
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