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Diagnosis of dorsal and palmar rotation of the lunate on a frontal radiograph
Vol. I3A, No.2 March 1988
9. Cone RO, Szabo R, Resnick D, Gelbennan R, Taleisnik J, Gilula LA. Computered tomography of the normal soft tissues of the wrist. Invest Radiol 1983;18:546-51. 10. Vannier MW, Totty WG, Stevens WG, et al. Musculoskeletal applications of three-dimensional surface reconstructions. Symposium on computed tomography. Orthop Clin North Am 1985;16:543-55.
Evaluation of humpback scaphoid by CT
I I. Sundberg SB, Clark B, Foster BK. Three-dimensional reformation of skeletal abnormalities using computed tomography. J Pediatr Orthop 1986;6:416-20. 12. Merher GL, Clark RA, Schneider HI, Stem PI. Highresolution computed tomography of the wrist in patients with carpal tunnel syndrome. Skeletal Radiol 1986; 15:549-52.
Diagnosis of dorsal and palmar rotation of the lunate on a frontal radiograph Anatomic variations in the contours of the palmar and dorsal horns of 100 dry lunates were classified by symmetry, curvature, and angularity. Frequencies of the major forms were determined. An algorithm was constructed for the identification of the dorsal and palmar horns of the lunate on a frontal radiograph. By this algorithm, it is possible to diagnose intercalated segment instabilities without the use of a lateral radiograph. (J HAND SURG 1988;13A:187-93.)
Robert M. Cantor, MD, PhD and Ethan M. Braunstein, MD, Cincinnati, Ohio, and Ann Arbor, Mich.
Many authors have noted a "triangular" lunate image on frontal wrist radiographs of patients with lunate and perilunate dislocation. In 1941, Huet and Huguier' published a thorough discussion of this sign of dislocation together with a review of the pertinent literature. They described the dislocated lunate as being top-shaped in frontal projection, with base convex proximally and apex pointing distally. Gilula 2
observed that triangularity of the lunate image is a sign of lunate rotation and does not necessarily indicate dislocation. However, we have seen many cases of intercalated segment instability in which the rotated lunate does not form a "triangular" image on a frontal radiograph. In this study, we explain these observations and present an algorithm for the diagnosis of dorsal and palmar rotation of the lunate on a frontal radiograph.
Materials and methods From the Department of Radiology, University of Cincinnati Medical Center, Cincinnati, Ohio, and the Department of Radiology, University of Michigan Medical Center, Ann Arbor, Mich. Received for publication April 20, 1987; accepted in revised form July 21, 1987. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: R. M. Cantor. MD, PhD, Department of Radiology, University of Cincinnati Medical Center, 234 Goodman St., Cincinnati, OH 45267.
We examined 100 dry adult lunates from the osteologic collection of the University of Michigan Department of Anatomy. The palmar and dorsal horns of each specimen were identified by the convexity of the palmar surface and the flatness of the dorsal surface.?" Right was distinguished from left by reference to the slope of the convex facet that articulates with the distal radius and the characteristic shapes of the scaphoid and triquetral facets.':" After each lunate was placed in standard anatomic position in front of the observer, the bone
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\
n
\
a
b
d
c
Fig. 3. The basic orthogonal dorsal series. These are the basic forms of the dorsal horn with a 90 degree radial angle. The radial margin is on the left and drawn vertically. Form Do. Broad form with parallel margins (a) . Form D,. One ulnar angle (b). Form D,. Two ulnar angles (c). Form DJ • Flared ulnar arc that is indistinguishable from P2 (d).
. Fig. 1. A right lunate in neutral position as seen from a dorsal point. Longitudinal lunate axis is indicated by a hatched line. The crescent-shaped scaphoid facet is on the left. This specimen is dorsally wedged i.e .• the rounded palmar hom is wider than the angular dorsal hom.
a
r-. b
c
b
a
d
Fig. 4. The basic oblique dorsal series. These are the basic forms of the dorsal horn with an acute radial angle. The radial margin is on the left and drawn vertically. Form Do'. Broad form with parallel margins (a) . Form D I ' . One ulnar angle (b). ' Form D,'. Two ulnar angles '(c) . Form D/. Flared ulnar arc that is indistinguishable from P,' (d).
Table I. The basic palmar series
c
d
Fig. 2. The basic palmar series . These are the basic forms of the palmar horn. By convention. the lateral (radial) margin is on the left and drawn vertically when straight. Form Po. A smooth symmetric arc (a). Form PI' A smooth asymmetric arc (b). Form P2 • A flared ulnar arc with a 90 degree radial angle (c). Form P,'. A flared ulnar arc with an acute radial angle (d).
was rotated along its transverse axis and the contours of its palmar and dorsal horns were sketched. A wide range of anatomic variation was observed. The variations in profile of the palmar and dorsal horns were classified on the basis of symmetry, curvature, and angularity. By use of this classification, an algorithm was constructed for identification of the palmar and dorsal lunate horns on a frontal radiograph. Results Surface anatomy of the lunate. The lunate bone is shaped like a rocker that is crescent-shaped in lateral projection. The palmar and dorsal parts of the bone that form the "horns" of the crescent are called the lunate horns. The remainder of the bone will be called the
Form· Po P, P2
'----F-re-q-lIe-n-c-y - - -
+ P2'
I 30 69t
• Abbreviations refer to forms illustrated in Fig. 2. tRadial angle truncation was present in 21 cases.
body of the lunate. The lunate has four articular and two nonarticular facets. The convex proximal facet articulates with the radius. The concave distal facet articulates with the capitate and hamate. The medial (ulnar) and lateral (radial) facets articulate with the triquetrum and scaphoid, respect ively. The palmar and dorsal surfaces are nonarticular. Relative widths of the lunate horns. The scaphoid and triquetral facets of the lunate have approximately plane surfaces. In most cases , these planes are not parallel but are tilted relative to one another so that both coronal and transverse cross sections of the lunate are wedged (Fig. 1). The planes of the scaphoid and triquetral facets always intersect a frontal plane in lines that converge distally, and they usually intersect a transverse plane in lines that converge dorsally. In the latter case, the dorsal hom is narrower than the palmar
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(\1\(\" abc
d
Fig. 5. Truncated dorsal forms. Form 0 , with truncated radial angle (a). Form 0, with truncated radial angle (b) . Form 0.' with truncated radial angle (c) . Form OJ with truncated radial angle (d) .
Table II. The basic orthogonal dorsal series Form*
I
Do D, D, DJ
Frequency
2 20 16 II
•Abbreviations refer 10 forms illustrated in Fig. 3.
Fig. 6. The ridge line. Tracing of a frontal radiograph with ridge line (arrowhead). The ridge line is not visible on a gross specimen but is a tangential image of the distal concavity of the lunate.
Table III. The basic oblique dorsal series Form*
I
.
Frequency
2
32
horn." ~ This dorsal wedging was present in 84 of the 100 lunates examined. In 13 lunates, the dorsal and palmar horns were equal in width . In three lunates, the dorsal hom was .wider than the palmar hom. Hence, dorsal and palmar horns cannot be distinguished solely on the basis of their relative widths. Profile of the palmar horn. The basic forms of the palmar hom of the lunate are illustrated schematicalIy in Fig. 2. Each contour is divided into radial and ulnar parts by the longitudinal lunate axis (Fig. 1). One form is symmetric about the longitudinal lunate axis, and its contour is a smooth arc convex distaJIy (Fig. 2, a). This form is rare and occurred only once in our sample. When the palmar contour is asymmetric, its ulnar margin is a flared curve. However, the radial margin of asymmetric basic forms may be either curved or angular. The asymmetric form with a curved radial margin is illustrated in Fig. 2, b. This form occurred 30 times. When the radial margin is angular, it may form a 90 degree angle (Fig. 2, c) or an acute angle (Fig. 2, d). Other forms may be derived from the basic palmar series by truncation of a radial angle or flattening of an ulnar arc. These are referred to as truncated forms. The frequencies of the basic palmar forms are given in Table I. Profile of the dorsal horn. The basic forms of the dorsal hom of the lunate may be divided into two series as shown schematicaJIy in Figs . 3 and 4. The basic orthogonal dorsal series is characterized by a 90 degree radial angle. The basic oblique dorsal series is characterized by an acute radial angle. The ulnar contour
9 8 "Abbreviation s refer to fonns illustrated in Fig. 4.
of the dorsal hom may be angular or curved. There are three angular forms in each series. Rarely, the dorsal hom is broad, and the radial and ulnar margins are almost paraJIel (Fig. 3, a and Fig. 4, a). However, in most cases the radial and ulnar margins converge distaJIy and there are one (Fig. 3, b and Fig. 4, b) or two (Fig. 3, c and Fig. 4, c) ulnar angles. When the ulnar contour is not angular, it is a flared curve (Fig. 3, d and Fig. 4, d). These forms are indistinguishable from the corresponding palmar forms (Fig. 2, c and d). The frequencies of the basic dorsal forms are summarized in Tables II and III. ·Angular forms were four times as frequent as curved forms. Of the former, one ulnar angle occurred twice as frequently as two ulnar angles. As in the palmar series, truncated forms may be obtained by truncation of a radial angle (Fig. 5). Radial angle truncation occurred 7 times in the orthogonal series and 20 times in the oblique series. Discussion
Virchow" was the first to recognize dorsal rotation of the lunate on a frontal radiograph by observing distal displacement of the "rounded" contour of the palmar hom. Fick? identified longitudinal rotation of the lunate in abduction and adduction by observing the movements of the rounded palmar and angular dorsal horns.
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Fig. 7. The ridge line as seen on frontal radiographs. Position of the specimen is maintained by impression in a sheet of wax. A, Neutral position. B, Palmar rotation (flexion). The width of the distally displaced dorsal horn is less than the length of the ridge line. C, Dorsal rotation (extension). The width of the distally displaced palmar horn is greater than the length of the ridge line.
In this study, we have classified anatomic variations in the palmar and dorsal horns of the lunate. The basic palmar series varies from the rare symmetric form Po to the highly asymmetric forms P2 and P/ as the radial arc is deformed into a right or acute angle (Fig. 2). Only forms Po and PI correspond to the description of Fick. In contrast, the ulnar margin of a dorsal horn may be either angular or curved. An orthogonal dorsal series of forms is characterized by a 90 degree radial angle (Fig. 3). Again, the broad symmetric angular form 0 0
is rare. The orthogonal forms vary from O. with one ulnar angle to O 2 with two ulnar angles to 0 3 with a smooth ulnar arc. 0 1 corresponds to the shape described by Fick. An oblique dorsal series of forms may be obtained from the orthogonal series by deforming the 90 degree radial angle into an acute angle (Fig. 4). Note that forms with a radial angle and ulnar arc occur in both the palmar and dorsal series and therefore cannot be distinguished by shape alone. When this occurs, the palmar and dorsal horns may usually be distinguished by their relative widths. To aid in this de-
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Fig. 8. The top-shaped lunate seen in lunate dislocations. This is a frontal radiograph of the same lunate as in Fig. 7 after. flexion and exorotation from anatomic position. The apex is formed by the dorsal hom seen almost in profile. The contour formed by the concave capitate facet is on the left. Note that the ridge line has vanished since the x-ray beam now strikes the capitate facet en face.
termination we have defined a reference line on frontal radiographs of the wrist that we call the ridge line. Observe that the capitate facet of the lunate is shaped like a cylindrical vault (Fig. I). On a frontal radiograph, the tangential image of the ridge line of the lunate vault is a radiopaque line (Fig. 6 and Fig. 7, A). Analogous with architectural terminology, we call this opaque line on the radiograph the ridge line. The ridge line constitutes the distal side of the trapezoidal image of the lunate body," Blurring or loss of the ridge line are indirect signs of lunate rotation. I. 10 In dorsally wedged lunates, the length of the ridge line may be used to distinguish between flexion and extension. When the lunate is flexed, its dorsal hom moves distally and the line of tangency of the x-ray beam with the lunate vault shifts anteriorly. Consequently, the length of the ridge line will be greater than the width of the distally displaced dorsal hom (Fig. 7, B). When the lunate is dorsally rotated, its palmar hom moves distally and the line of tangency shifts posteriorly. In this case, the length of the ridge line will be less than the width of the distally displaced palmar hom (Fig. 7, C). The palmar and dorsal horns cannot be distinguished on a frontal radiograph when they have the same shape
Fig. 9. Dorsal intercalated segment instability (DISI). A, Dorsopalmar projection. The distal lunate contour (arrow) is rounded, corresponding to the form P" Therefore, the lunate is dorsally rotated. Note that the length of the ridge line is less than the width of the distal contour. This is a form of DISI with scapholunate dissociation. H, Lateral projection. Dorsal rotation of the lunate is confirmed.
and width. There were five such lunates in our sample. All three lunates with dorsal hom wider than palmar hom had angular dorsal horns that could be recognized by shape alone.
Algorithm The following algorithm permits the identification of either the palmar or dorsal hom of a flexed or extended lunate on a frontal radiograph. This identification is
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contour and the length of the ridge line arc compared. A. If the width of the contour is greater than the length of the ridge line, it represents the palmar hom. B. If the width of the contour is less than the length of the ridge line, it represents the dorsal hom . C. If contour width equals ridge line length, the case is undecidable.
Lunate rotations
Fig. 10. Volar intercalated segment instability (VISI). A, Dorsopalmar projection . The distal lunate contour (arrow) is angular, corresponding to form D r- Therefore, the lunate is rotated toward the palm . Note that the length of the ridge line is greater than the width of the distal contour. The scaphoid is also rotated toward the palm and there is scapholunate separation. B, Lateral projection. Palmar rotation of the lunate is confirmed.
based on the shape and width (relative to the ridge line) of the distal lunate contour: I. If the contour is rounded, it represents the palmar hom. II. If the contour is angular, it represents the dorsal hom. III. In all other cases, the width of the distal lunate
Clearly, a flexed lunate is not always triangular shaped in frontal projection. However, we agree with Huet and Huguier' that a top-shaped lunate results from a double rotation about transverse and longitudinal lunate axes . This complex movement consists of palmar rotation and exorotation (the palmar hom moves radially) (Fig. 8). Because of the longitudinal component of this rotation, the dorsal hom is seen in profile and its form in frontal projection has no significant effect on the production of the top-shaped image. In 1972, Linscheid et al." published a fundamental study of traumatic instability of the wrist. In that paper, the scapholunate and capitolunate angles were defined by means of a lateral radiograph. These angles were used in the definition and diagnosis of volar flexion intercalated segment instability (VISI) and dorsiflexion intercalated segment instability (DISI): In this study, we present a diagnostic algorithm for the recognition of extension and flexion of the lunate on a frontal radiograph. Since criteria for the recognition of scaphoid flexion on a frontal radiograph are well known," it is now possible to make the diagnosis of DISI (Fig. 9) and VISI (Fig. 10) without reference to carpal angles and without the use of a lateral radiograph. The authors thank Dr. Louis Gilula for his critical reading of the manuscript.
REFERENCES I. Huet P, Huguier J. Syndrome radiologique de face au cours des luxations retrolunaires du carpe, Presse Med I941;6-9:Aug:860-3. 2. Gilula LA. Carpal injuries: analytic approach and case exercises . AJR 1979;133:503-17. 3. Anson BJ, ed. Morris ' human anatomy. 12th ed , New York: McGraw-Hili, 1966:264. 4. Pfitzner W. Beitrage zur Kenntnis des mcnschlichen Extrernitatenskelets. VIII. Die morphologischen Elemente des menschlichen Handskelcts. Z Morphol Anthropol 1900;2:632.
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Diagnosis of dorsal and palmar rotation of lunate on frontal radiograph
5. Romanes GJ, ed. Cunningham's textbook of anatomy. 10th ed. London: Oxford University Press; 1964:164. 6. Testut L, Latarjet A. Traite d'anatornie humaine. 9th ed. Paris: G Ooin & Cie, 1948:341. 7. Gray H. Anatomy of the human body. Clemente CD, ed. Philadelphia: Lea & Febiger, 1985:251. 8. Virchow H. Rdntgcn-Aufnahmen der Hand. Sitzungsber Ges Naturf Fr Berlin 1899;16 May:90. 9. Fick R. Handbuch der Anatomie und Mechanik der Gelenke. Spezielle Gelenk-und Muskelmechanik. Jena: Gustav Fischer, 1911:375.
10. Rogers LF. Radiology of skeletal trauma. New York: Churchill Livingstone, 1982:552. 11. Linscheid RL, DobynsJH, BeaboutJW, Bryan RS. Traumatic instability of the wrist. Diagnosis, classification and pathomechanics. J Bone Joint Surg 1972;54A: 1612-32. 12. Cope JR. Rotatory subluxation of the scaphoid. Clin Radiol 1984;35:495-501.
Failed distal ulna resections Twenty patients with complaints of pain and limitation of activities for more than 1 year after ulnar head resection (Darrach) were studied. Their ages ranged from 18 to 60 years (mean, 38 years), The initial indications for operation were posttraumatic derangement in 18 patients, radial growth anomaly in 1, and a lesion of the ulna in 1. Follow-up ranged from 29 to 135 months (mean, 61 months). The patients had an average of 2.2 additional operations, with up to seven procedures per patient. Radiographs were compared with those from an equal number of successful Darrach resections chosen randomly, and no significant differences were noted. All 20 patients continue to have difficulties despite several years of treatment. The Darrach resection can result in serious disability, especially in the younger patient and the patient with lax ligaments. Reoperation on these patients is rarely successful. (J Hand Surg 1988;13A:193-200.)
Edward J. Bieber, MD, Ronald L. Linscheid, MD, James H. Dobyns, MD, and Robert D. Beckenbaugh, MD, Rochester, -Minn.
Resection of the distal ulna for various afflictions of the distal radioulnar joint was first recommended in the nineteenth century' but was popularized in this century, beginning with the description in 19l3 by Darrach.' The procedure has been applied after fractures, ligamentous disruptions of the distal radioulnar joint, and congenital anomalies such as Madelung's deformity and in rheumatoid arthritis. Several series
From the Department of Orthopedics, Mayo Clinic and Mayo Foundation, Rochester, Minn. Received for publication Dec. 29, 1986; accepted in revised form July 22, 1987. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: R. L. Linscheid, MD, Mayo Clinic, 200 First 51. SW, Rochester, MN 55905.
have evaluated results, beginning with the series of Boyd and Stone in 1944. 3 In most of these series, including those from our institution, I. 3-6 the results generally have been good, with the achievement of a good range of motion and minimal loss of strength. However, in the last few years, reports of a lack of uniformly good results with the Darrach procedures have appeared.?" For several years, we have been concerned about the patient with persistent complaints. We evaluated a group of patients whose complaints persisted for at least 12 months after the Darrach procedure in an attempt to define the causes for the less-than-satisfactory results. We analyzed the indications, surgical technique, and postoperative care. It is our goal to characterize the small percentage of patients who have trouble with a distal ulna resection and to identify the patient at risk.
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9. Cone RO, Szabo R, Resnick D, Gelbennan R, Taleisnik J, Gilula LA. Computered tomography of the normal soft tissues of the wrist. Invest Radiol 1983;18:546-51. 10. Vannier MW, Totty WG, Stevens WG, et al. Musculoskeletal applications of three-dimensional surface reconstructions. Symposium on computed tomography. Orthop Clin North Am 1985;16:543-55.
Evaluation of humpback scaphoid by CT
I I. Sundberg SB, Clark B, Foster BK. Three-dimensional reformation of skeletal abnormalities using computed tomography. J Pediatr Orthop 1986;6:416-20. 12. Merher GL, Clark RA, Schneider HI, Stem PI. Highresolution computed tomography of the wrist in patients with carpal tunnel syndrome. Skeletal Radiol 1986; 15:549-52.
Diagnosis of dorsal and palmar rotation of the lunate on a frontal radiograph Anatomic variations in the contours of the palmar and dorsal horns of 100 dry lunates were classified by symmetry, curvature, and angularity. Frequencies of the major forms were determined. An algorithm was constructed for the identification of the dorsal and palmar horns of the lunate on a frontal radiograph. By this algorithm, it is possible to diagnose intercalated segment instabilities without the use of a lateral radiograph. (J HAND SURG 1988;13A:187-93.)
Robert M. Cantor, MD, PhD and Ethan M. Braunstein, MD, Cincinnati, Ohio, and Ann Arbor, Mich.
Many authors have noted a "triangular" lunate image on frontal wrist radiographs of patients with lunate and perilunate dislocation. In 1941, Huet and Huguier' published a thorough discussion of this sign of dislocation together with a review of the pertinent literature. They described the dislocated lunate as being top-shaped in frontal projection, with base convex proximally and apex pointing distally. Gilula 2
observed that triangularity of the lunate image is a sign of lunate rotation and does not necessarily indicate dislocation. However, we have seen many cases of intercalated segment instability in which the rotated lunate does not form a "triangular" image on a frontal radiograph. In this study, we explain these observations and present an algorithm for the diagnosis of dorsal and palmar rotation of the lunate on a frontal radiograph.
Materials and methods From the Department of Radiology, University of Cincinnati Medical Center, Cincinnati, Ohio, and the Department of Radiology, University of Michigan Medical Center, Ann Arbor, Mich. Received for publication April 20, 1987; accepted in revised form July 21, 1987. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: R. M. Cantor. MD, PhD, Department of Radiology, University of Cincinnati Medical Center, 234 Goodman St., Cincinnati, OH 45267.
We examined 100 dry adult lunates from the osteologic collection of the University of Michigan Department of Anatomy. The palmar and dorsal horns of each specimen were identified by the convexity of the palmar surface and the flatness of the dorsal surface.?" Right was distinguished from left by reference to the slope of the convex facet that articulates with the distal radius and the characteristic shapes of the scaphoid and triquetral facets.':" After each lunate was placed in standard anatomic position in front of the observer, the bone
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\
n
\
a
b
d
c
Fig. 3. The basic orthogonal dorsal series. These are the basic forms of the dorsal horn with a 90 degree radial angle. The radial margin is on the left and drawn vertically. Form Do. Broad form with parallel margins (a) . Form D,. One ulnar angle (b). Form D,. Two ulnar angles (c). Form DJ • Flared ulnar arc that is indistinguishable from P2 (d).
. Fig. 1. A right lunate in neutral position as seen from a dorsal point. Longitudinal lunate axis is indicated by a hatched line. The crescent-shaped scaphoid facet is on the left. This specimen is dorsally wedged i.e .• the rounded palmar hom is wider than the angular dorsal hom.
a
r-. b
c
b
a
d
Fig. 4. The basic oblique dorsal series. These are the basic forms of the dorsal horn with an acute radial angle. The radial margin is on the left and drawn vertically. Form Do'. Broad form with parallel margins (a) . Form D I ' . One ulnar angle (b). ' Form D,'. Two ulnar angles '(c) . Form D/. Flared ulnar arc that is indistinguishable from P,' (d).
Table I. The basic palmar series
c
d
Fig. 2. The basic palmar series . These are the basic forms of the palmar horn. By convention. the lateral (radial) margin is on the left and drawn vertically when straight. Form Po. A smooth symmetric arc (a). Form PI' A smooth asymmetric arc (b). Form P2 • A flared ulnar arc with a 90 degree radial angle (c). Form P,'. A flared ulnar arc with an acute radial angle (d).
was rotated along its transverse axis and the contours of its palmar and dorsal horns were sketched. A wide range of anatomic variation was observed. The variations in profile of the palmar and dorsal horns were classified on the basis of symmetry, curvature, and angularity. By use of this classification, an algorithm was constructed for identification of the palmar and dorsal lunate horns on a frontal radiograph. Results Surface anatomy of the lunate. The lunate bone is shaped like a rocker that is crescent-shaped in lateral projection. The palmar and dorsal parts of the bone that form the "horns" of the crescent are called the lunate horns. The remainder of the bone will be called the
Form· Po P, P2
'----F-re-q-lIe-n-c-y - - -
+ P2'
I 30 69t
• Abbreviations refer to forms illustrated in Fig. 2. tRadial angle truncation was present in 21 cases.
body of the lunate. The lunate has four articular and two nonarticular facets. The convex proximal facet articulates with the radius. The concave distal facet articulates with the capitate and hamate. The medial (ulnar) and lateral (radial) facets articulate with the triquetrum and scaphoid, respect ively. The palmar and dorsal surfaces are nonarticular. Relative widths of the lunate horns. The scaphoid and triquetral facets of the lunate have approximately plane surfaces. In most cases , these planes are not parallel but are tilted relative to one another so that both coronal and transverse cross sections of the lunate are wedged (Fig. 1). The planes of the scaphoid and triquetral facets always intersect a frontal plane in lines that converge distally, and they usually intersect a transverse plane in lines that converge dorsally. In the latter case, the dorsal hom is narrower than the palmar
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(\1\(\" abc
d
Fig. 5. Truncated dorsal forms. Form 0 , with truncated radial angle (a). Form 0, with truncated radial angle (b) . Form 0.' with truncated radial angle (c) . Form OJ with truncated radial angle (d) .
Table II. The basic orthogonal dorsal series Form*
I
Do D, D, DJ
Frequency
2 20 16 II
•Abbreviations refer 10 forms illustrated in Fig. 3.
Fig. 6. The ridge line. Tracing of a frontal radiograph with ridge line (arrowhead). The ridge line is not visible on a gross specimen but is a tangential image of the distal concavity of the lunate.
Table III. The basic oblique dorsal series Form*
I
.
Frequency
2
32
horn." ~ This dorsal wedging was present in 84 of the 100 lunates examined. In 13 lunates, the dorsal and palmar horns were equal in width . In three lunates, the dorsal hom was .wider than the palmar hom. Hence, dorsal and palmar horns cannot be distinguished solely on the basis of their relative widths. Profile of the palmar horn. The basic forms of the palmar hom of the lunate are illustrated schematicalIy in Fig. 2. Each contour is divided into radial and ulnar parts by the longitudinal lunate axis (Fig. 1). One form is symmetric about the longitudinal lunate axis, and its contour is a smooth arc convex distaJIy (Fig. 2, a). This form is rare and occurred only once in our sample. When the palmar contour is asymmetric, its ulnar margin is a flared curve. However, the radial margin of asymmetric basic forms may be either curved or angular. The asymmetric form with a curved radial margin is illustrated in Fig. 2, b. This form occurred 30 times. When the radial margin is angular, it may form a 90 degree angle (Fig. 2, c) or an acute angle (Fig. 2, d). Other forms may be derived from the basic palmar series by truncation of a radial angle or flattening of an ulnar arc. These are referred to as truncated forms. The frequencies of the basic palmar forms are given in Table I. Profile of the dorsal horn. The basic forms of the dorsal hom of the lunate may be divided into two series as shown schematicaJIy in Figs . 3 and 4. The basic orthogonal dorsal series is characterized by a 90 degree radial angle. The basic oblique dorsal series is characterized by an acute radial angle. The ulnar contour
9 8 "Abbreviation s refer to fonns illustrated in Fig. 4.
of the dorsal hom may be angular or curved. There are three angular forms in each series. Rarely, the dorsal hom is broad, and the radial and ulnar margins are almost paraJIel (Fig. 3, a and Fig. 4, a). However, in most cases the radial and ulnar margins converge distaJIy and there are one (Fig. 3, b and Fig. 4, b) or two (Fig. 3, c and Fig. 4, c) ulnar angles. When the ulnar contour is not angular, it is a flared curve (Fig. 3, d and Fig. 4, d). These forms are indistinguishable from the corresponding palmar forms (Fig. 2, c and d). The frequencies of the basic dorsal forms are summarized in Tables II and III. ·Angular forms were four times as frequent as curved forms. Of the former, one ulnar angle occurred twice as frequently as two ulnar angles. As in the palmar series, truncated forms may be obtained by truncation of a radial angle (Fig. 5). Radial angle truncation occurred 7 times in the orthogonal series and 20 times in the oblique series. Discussion
Virchow" was the first to recognize dorsal rotation of the lunate on a frontal radiograph by observing distal displacement of the "rounded" contour of the palmar hom. Fick? identified longitudinal rotation of the lunate in abduction and adduction by observing the movements of the rounded palmar and angular dorsal horns.
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Fig. 7. The ridge line as seen on frontal radiographs. Position of the specimen is maintained by impression in a sheet of wax. A, Neutral position. B, Palmar rotation (flexion). The width of the distally displaced dorsal horn is less than the length of the ridge line. C, Dorsal rotation (extension). The width of the distally displaced palmar horn is greater than the length of the ridge line.
In this study, we have classified anatomic variations in the palmar and dorsal horns of the lunate. The basic palmar series varies from the rare symmetric form Po to the highly asymmetric forms P2 and P/ as the radial arc is deformed into a right or acute angle (Fig. 2). Only forms Po and PI correspond to the description of Fick. In contrast, the ulnar margin of a dorsal horn may be either angular or curved. An orthogonal dorsal series of forms is characterized by a 90 degree radial angle (Fig. 3). Again, the broad symmetric angular form 0 0
is rare. The orthogonal forms vary from O. with one ulnar angle to O 2 with two ulnar angles to 0 3 with a smooth ulnar arc. 0 1 corresponds to the shape described by Fick. An oblique dorsal series of forms may be obtained from the orthogonal series by deforming the 90 degree radial angle into an acute angle (Fig. 4). Note that forms with a radial angle and ulnar arc occur in both the palmar and dorsal series and therefore cannot be distinguished by shape alone. When this occurs, the palmar and dorsal horns may usually be distinguished by their relative widths. To aid in this de-
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Fig. 8. The top-shaped lunate seen in lunate dislocations. This is a frontal radiograph of the same lunate as in Fig. 7 after. flexion and exorotation from anatomic position. The apex is formed by the dorsal hom seen almost in profile. The contour formed by the concave capitate facet is on the left. Note that the ridge line has vanished since the x-ray beam now strikes the capitate facet en face.
termination we have defined a reference line on frontal radiographs of the wrist that we call the ridge line. Observe that the capitate facet of the lunate is shaped like a cylindrical vault (Fig. I). On a frontal radiograph, the tangential image of the ridge line of the lunate vault is a radiopaque line (Fig. 6 and Fig. 7, A). Analogous with architectural terminology, we call this opaque line on the radiograph the ridge line. The ridge line constitutes the distal side of the trapezoidal image of the lunate body," Blurring or loss of the ridge line are indirect signs of lunate rotation. I. 10 In dorsally wedged lunates, the length of the ridge line may be used to distinguish between flexion and extension. When the lunate is flexed, its dorsal hom moves distally and the line of tangency of the x-ray beam with the lunate vault shifts anteriorly. Consequently, the length of the ridge line will be greater than the width of the distally displaced dorsal hom (Fig. 7, B). When the lunate is dorsally rotated, its palmar hom moves distally and the line of tangency shifts posteriorly. In this case, the length of the ridge line will be less than the width of the distally displaced palmar hom (Fig. 7, C). The palmar and dorsal horns cannot be distinguished on a frontal radiograph when they have the same shape
Fig. 9. Dorsal intercalated segment instability (DISI). A, Dorsopalmar projection. The distal lunate contour (arrow) is rounded, corresponding to the form P" Therefore, the lunate is dorsally rotated. Note that the length of the ridge line is less than the width of the distal contour. This is a form of DISI with scapholunate dissociation. H, Lateral projection. Dorsal rotation of the lunate is confirmed.
and width. There were five such lunates in our sample. All three lunates with dorsal hom wider than palmar hom had angular dorsal horns that could be recognized by shape alone.
Algorithm The following algorithm permits the identification of either the palmar or dorsal hom of a flexed or extended lunate on a frontal radiograph. This identification is
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contour and the length of the ridge line arc compared. A. If the width of the contour is greater than the length of the ridge line, it represents the palmar hom. B. If the width of the contour is less than the length of the ridge line, it represents the dorsal hom . C. If contour width equals ridge line length, the case is undecidable.
Lunate rotations
Fig. 10. Volar intercalated segment instability (VISI). A, Dorsopalmar projection . The distal lunate contour (arrow) is angular, corresponding to form D r- Therefore, the lunate is rotated toward the palm . Note that the length of the ridge line is greater than the width of the distal contour. The scaphoid is also rotated toward the palm and there is scapholunate separation. B, Lateral projection. Palmar rotation of the lunate is confirmed.
based on the shape and width (relative to the ridge line) of the distal lunate contour: I. If the contour is rounded, it represents the palmar hom. II. If the contour is angular, it represents the dorsal hom. III. In all other cases, the width of the distal lunate
Clearly, a flexed lunate is not always triangular shaped in frontal projection. However, we agree with Huet and Huguier' that a top-shaped lunate results from a double rotation about transverse and longitudinal lunate axes . This complex movement consists of palmar rotation and exorotation (the palmar hom moves radially) (Fig. 8). Because of the longitudinal component of this rotation, the dorsal hom is seen in profile and its form in frontal projection has no significant effect on the production of the top-shaped image. In 1972, Linscheid et al." published a fundamental study of traumatic instability of the wrist. In that paper, the scapholunate and capitolunate angles were defined by means of a lateral radiograph. These angles were used in the definition and diagnosis of volar flexion intercalated segment instability (VISI) and dorsiflexion intercalated segment instability (DISI): In this study, we present a diagnostic algorithm for the recognition of extension and flexion of the lunate on a frontal radiograph. Since criteria for the recognition of scaphoid flexion on a frontal radiograph are well known," it is now possible to make the diagnosis of DISI (Fig. 9) and VISI (Fig. 10) without reference to carpal angles and without the use of a lateral radiograph. The authors thank Dr. Louis Gilula for his critical reading of the manuscript.
REFERENCES I. Huet P, Huguier J. Syndrome radiologique de face au cours des luxations retrolunaires du carpe, Presse Med I941;6-9:Aug:860-3. 2. Gilula LA. Carpal injuries: analytic approach and case exercises . AJR 1979;133:503-17. 3. Anson BJ, ed. Morris ' human anatomy. 12th ed , New York: McGraw-Hili, 1966:264. 4. Pfitzner W. Beitrage zur Kenntnis des mcnschlichen Extrernitatenskelets. VIII. Die morphologischen Elemente des menschlichen Handskelcts. Z Morphol Anthropol 1900;2:632.
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5. Romanes GJ, ed. Cunningham's textbook of anatomy. 10th ed. London: Oxford University Press; 1964:164. 6. Testut L, Latarjet A. Traite d'anatornie humaine. 9th ed. Paris: G Ooin & Cie, 1948:341. 7. Gray H. Anatomy of the human body. Clemente CD, ed. Philadelphia: Lea & Febiger, 1985:251. 8. Virchow H. Rdntgcn-Aufnahmen der Hand. Sitzungsber Ges Naturf Fr Berlin 1899;16 May:90. 9. Fick R. Handbuch der Anatomie und Mechanik der Gelenke. Spezielle Gelenk-und Muskelmechanik. Jena: Gustav Fischer, 1911:375.
10. Rogers LF. Radiology of skeletal trauma. New York: Churchill Livingstone, 1982:552. 11. Linscheid RL, DobynsJH, BeaboutJW, Bryan RS. Traumatic instability of the wrist. Diagnosis, classification and pathomechanics. J Bone Joint Surg 1972;54A: 1612-32. 12. Cope JR. Rotatory subluxation of the scaphoid. Clin Radiol 1984;35:495-501.
Failed distal ulna resections Twenty patients with complaints of pain and limitation of activities for more than 1 year after ulnar head resection (Darrach) were studied. Their ages ranged from 18 to 60 years (mean, 38 years), The initial indications for operation were posttraumatic derangement in 18 patients, radial growth anomaly in 1, and a lesion of the ulna in 1. Follow-up ranged from 29 to 135 months (mean, 61 months). The patients had an average of 2.2 additional operations, with up to seven procedures per patient. Radiographs were compared with those from an equal number of successful Darrach resections chosen randomly, and no significant differences were noted. All 20 patients continue to have difficulties despite several years of treatment. The Darrach resection can result in serious disability, especially in the younger patient and the patient with lax ligaments. Reoperation on these patients is rarely successful. (J Hand Surg 1988;13A:193-200.)
Edward J. Bieber, MD, Ronald L. Linscheid, MD, James H. Dobyns, MD, and Robert D. Beckenbaugh, MD, Rochester, -Minn.
Resection of the distal ulna for various afflictions of the distal radioulnar joint was first recommended in the nineteenth century' but was popularized in this century, beginning with the description in 19l3 by Darrach.' The procedure has been applied after fractures, ligamentous disruptions of the distal radioulnar joint, and congenital anomalies such as Madelung's deformity and in rheumatoid arthritis. Several series
From the Department of Orthopedics, Mayo Clinic and Mayo Foundation, Rochester, Minn. Received for publication Dec. 29, 1986; accepted in revised form July 22, 1987. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: R. L. Linscheid, MD, Mayo Clinic, 200 First 51. SW, Rochester, MN 55905.
have evaluated results, beginning with the series of Boyd and Stone in 1944. 3 In most of these series, including those from our institution, I. 3-6 the results generally have been good, with the achievement of a good range of motion and minimal loss of strength. However, in the last few years, reports of a lack of uniformly good results with the Darrach procedures have appeared.?" For several years, we have been concerned about the patient with persistent complaints. We evaluated a group of patients whose complaints persisted for at least 12 months after the Darrach procedure in an attempt to define the causes for the less-than-satisfactory results. We analyzed the indications, surgical technique, and postoperative care. It is our goal to characterize the small percentage of patients who have trouble with a distal ulna resection and to identify the patient at risk.
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