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Microvascular anatomy of the radioscapholunate ligament of the wrist
Microvascular anatomy of the radioscapholunate ligament of the wrist The microvascular circulation and basic structural features of the radioscapbohmate ligament of the wrist were studied in six fresh cadaver specimens by iqjection and clearing techniques. A rich vascular supply was found to originate from vessels that perforate the palmar capsule and enter the synovium radioscaphohmate
that surrounds
the ligament. By way of branches from the synovium,
dant blood supply. No contributions are derived from the bony attachments. light microscopy
the
ligament and most of the scapholunate interosseous ligament receive an abunrevealed a delicate, well-vascularized
Observation under
ligament consisting of regular collagen
bundles. No elastic fibers were observed. This study indicates that the radioscapholunate ligament
has a vascular supply that may be sufficient for healing by known methods. (J HAND SURC 1990;15A:279-82.)
Marcia L. Hixson,
MD, and Charles Stewart, BS, Little Rock, Ark.
S
capholunate diastasis and rotary subluxation of the scaphoid are seen frequently in patients with acute and chronic wrist pain. Treatment of these injuries is best done early; however, even under ideal conditions, the results of open or closed reduction, pinning, ligament repair, or ligament reconstruction are variable and often disappointing. ‘, ’ Valuable information has been gained through the work of Taleisnik, Lewis, Blair, Mayfield and others,3-6 who described the gross anatomy and the important stabilizing function of the radioscapholunate ligament and the scapholunate interosseous ligament. These two ligaments form an integrated complex, which has been shown to be the primary stabilizer of the scapholunate articulation and, along with the radioscaphocapitate ligament, is the principal stabilizer of the proximal pole of the scaphoid.7 Traumatic disruption of this ligamentous complex may lead to instability From the Section of Hand and Microsurgery,
paedic Surgery, University tle Rock, Ark. Received for publication 5, 1989.
of Arkansas
Department of Orthofor Medical Sciences, Lit-
Jan. 26, 1989; accepted in revised form May
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: Marcia L. Hixson, MD, Section of Hand and Microsurgery, Department of Orthopaedic Surgery, University of Arkansas for Medical Sciences, 4301 W. Markham, Little Rock, AR 72205. 3/I/14251
of the proximal pole of the scaphoid and to scapholunate diastasis. If this subluxation is not reduced, the forces that are transmitted through the carpus are concentrated abnormally, and posttraumatic arthritis results. Treatment of injuries to the radioscapholunate ligament and the scapholunate interosseous ligament is d;‘fficult and controversial. This is partly because of lgnorance regarding the anatomy and healing mechanisms of these ligaments. Research into this problem is in t&e developmental stage and has not yielded enough useful information to influence the results of clinical treatment. The purpose of this experiment was to define the microscopic anatomy, including the microvascular anatomy, of the radioscapholunate ligament of the wrist. This knowledge should serve as a foundation for further studies into the ligament’s response to injury and its ability to heal. Materials
and methods
Six fresh-frozen cadaver forearm-hand preparatisns were used in this study. Specimens first had x-ray fihns to rule out preexisting pathologic conditions. The limbs were then divided into two groups; the first group was used to identify the microvascular anatomy of the radioscapholunate ligament and the second group was used to demonstrate the general microscopic anatomy. Group I. The radial and ulnar arteries of four cadaver forearms were cannulated. The vascular system was flushed with warm heparinized saline solution until clear of blood. With the use of the method of Rhinelander and Stewart, a warmed mixture of India ink and THE JOURNAL OF HAND SURGERY
279
280
The Journal of HAND SURGERY
Hixson and Stewart
Fig. 1. Larger caliber perpendicular branches (arrows) pierce
Fig. 2. The midportion of the scapholunate interosseous lig-
the capsule to supply the intracapsular ligaments. (I?/ Radius, (L) lunate.
ament is avascular. (RJ Radius, (15)lunate, (S) scaphoid.
glycerine was injected at a pressure of 120 mm of mercury until dye emerged from small cuts on the fingertips. The specimens were cooled overnight, then dissected. All soft tissue superficial to the wrist capsule was removed after noting major arteries and their branches. A band saw was used to reduce the specimen to a block of tissue consisting of radius, scaphoid, and lunate with intact capsule and ligaments. These blocks were fixed in formalin and bleached for 24 hours with 6% hydrogen peroxide. They were then further cut into 2 mm-thick sections, with a 0.012-inch diamond wheel, some in the sagittal and others in the coronal plane. By use of a modified Spalteholtz technique these sections were decalcified and cleared as follows: The blocks were decalcified in a formic acid-sodium citrate mixture, washed in a 5% crystalline sodium sulphate solution, and dehydrated in ethanol. The blocks were cleared in benzene and in Spalteholtz fluid (methyl salicylate and benzyl benzoate). They were then examined
under the dissecting microscope and the polarized light microscope, and the vascular patterns were noted. Group II. The radioscapholunate ligaments, with their synovial envelopes, were harvested from two cadaver wrists. The ligaments were fixed and stained for light microscopy with hematoxylin and eosin stain, and also using Weigert’s resourcin-fuschin stain for elastic fibers. The fixed ligaments were cut in longitudinal and cross sections and viewed under the light and polarized light microscopes. Results Group I. Ail specimens were adequately perfused and were included in the study. Gross dissection showed a rich vascular plexus on the palmar aspect of the capsule, which appears to be derived mainly from branches of the radial and anterior interosseous arteries. Sagittal microscopic sections revealed numerous perpendicular branches that perforate the capsule at roughly 1 mm
Vol. HA, No. 2 March 1990
intervals. These perforators in turn send branches to the synovium of the radiocarpal joint and also directly to the intracapsular ligaments (Fig. 1). Small vessels course along the radioscapholunate ligament in the synovium and send frequent branches to the substance of the ligament. Arterioles are most numerous in the synovium near bony attachments. No branches were observed entering the ligaments from the bone. Vessels that course along the axis of the ligament continue into the bony fossae, where they terminate within the synovial attachment. The scapholunate interosseous ligament was best seen in the coronal sections. The ligament is continuous with the articular cartilage of the scaphoid and lunate but, as demonstrated under polarized light, is distinctly collaginous. In its midportion the ligament appears to be entirely avascular (Fig. 2). Dorsally and palmarly where it is surrounded by synovium, the interosseous ligament is well supplied by synovial arterioles, similar to the pattern observed in the extrinsic ligaments (Fig. 3). Group II. Observation of the detached radioscapholunate ligaments under light microscopy revealed multiple slender, longitudinally oriented collagen bundles populated by fibroblasts. The ligament is surrounded by a synovium rich in blood vessels, which send frequent branches into the substance of the ligament. Small vessels also course longitudinally among the collagen bundles (Fig. 4). The Weigert resourcin-fuschin stain for elastic fibers failed to reveal elastin in either the substance of the ligament or in the small caliber arterioles. Discussion The radioscapholunate ligament of the wrist is a slender, largely synovial structure, which is weak in comparison to other palmar intracapsular ligaments and in comparison to the scapholunate interosseous ligament.6 Nevertheless, its function appears to be important in maintaining wrist stability. Its gross description has been published previously in detail and will be summarized here. The ligament originates from the interfacet prominence of the palmar lip of the distal radius where its collagenous bundles interdigitate with the artitular cartilage. From this point, the ligament fans out distally, obliquely, and dorsally to attach to the proximal and palmar aspects of the scapholunate interosseous ligament, and to the articular surfaces of the scaphoid and lunate.’ The entire complex is enveloped in a synovial membrane that isolates the radioscapholunate ligament, the scapholunate interosseous liga-
Anatomy of radioscapholunate
ligament of wrist
281
Fig. 3. Dorsal cut of the scapholunate interosseous ligament showing abundant synovial-derived branches. (R) Radius, (L) lunate, (S) scaphoid. ment, and scapholunate joint from the radial carpal joint. Vessels from the metaphysis of the distal radius do not penetrate the ligament, and vessels in and around the ligament do not penetrate the lunate and scaphoid. The radioscapholunate ligament itself measures approximately 1 cm in length, 0.5 cm in width, and 0.2 to 0.4 cm in thickness. After the synovial covering has been removed, the ligament’s fibrous component is seen, which consists of parallel bundles of collagen fibers. With wrist movement after removal of the radioscaphocapitate and radiolunotriquetral (long radiolunate) ligaments, the radioscapholunate ligament is seen to be taut in extension and in ulnar deviation and is lax in flexion and in radial deviation. This implies that the radioscapholunate ligament acts as a restraint during wrist extension and ulnar deviation, keeping the proximal pole of the scaphoid anchored to the palmar lip of the radius while the distal pole is pulled into extension. Other ligaments appear to be responsible for stabilizing the proximal pole of the scaphoid when the
282
The Journal of HAND SURGERY
Hixson and Stewart
Fig. 4. Light microscopy shows that the radioscapholunate ligament is composed of regular collagen fibers. Arterioles (arrows) course around and through the collagen bundles. (S) synovium. (Original magnification X IO.)
wrist is in flexion or radial deviation (distal pole flexed).
Experiments on the anterior cruciate ligament of the knee suggest that the ligament heals by means of a fibrin clot.* The clot is thought to originate from the surrounding vasculature and organizes within the tom ligament to bridge the gap. Little is known about the radioscapholunate ligament’s response to injury or its mechanism or ability to repair itself. It, like the anterior cruciate ligament, is intracapsular, appears to have a similar anatomy, and is surrounded by a synovial envelope through which it receives its major blood supply. This study uses a reproducible method to demonstrate that the radioscapholunate and scapholunate interosseous ligaments have a complex and rich vascular supply. Further work should demonstrate the importance of a vascular response to injury. If arterial proliferation and ingrowth play an important part in healing of the ligament, approaches and methods can be developed that maximize this response. REFERENCES 1. Green DP, O’Brien ET. Open reduction of carpal dislocations: indications and operative SURG 1978;3:250-65.
techniques.
J HAND
2. Palmer AK, Dobyns MD, Linscheid RL. Management of posttraumatic instability of the wrist secondary to ligament rupture. J HAND SURG 1978;3:507-32. 3. Taleisnik J. Wrist: anatomy, function and injury. In: Am Acad Orthop Surgeons Instruct Course Lect. St. Louis: The CV Mosby Company, 1978:27-61. 4. Lewis OJ. Hamshem RJ, Buckmill TM. The anatomy of the wrist joint. J Anat 1979;106:539-52. 5. Berger RA, Blair WF, Crowninshield RO, Flatt AE. The scapholunate ligament. J HAND SURC 1982;7:87-91. 6. Mayfield JK, Johnson RP, Kilcoyne RF. The ligaments of the human wrist and their funtionai significance. Anat Ret 1986;186:417. 7,. Berger RA, Landsmeer JMF. The palmar radiocarpal ligaments: a study of adult and fetal human wrist joints. Iowa Orthop J 1985;5:32-41. 8. Amoczky SP, Rubin RM, Marshall JL, Microvasculature of the cruciate ligaments and its response to injury. J Bone Joint Surg 1979;61A:l221-9.
that surrounds
the ligament. By way of branches from the synovium,
dant blood supply. No contributions are derived from the bony attachments. light microscopy
the
ligament and most of the scapholunate interosseous ligament receive an abunrevealed a delicate, well-vascularized
Observation under
ligament consisting of regular collagen
bundles. No elastic fibers were observed. This study indicates that the radioscapholunate ligament
has a vascular supply that may be sufficient for healing by known methods. (J HAND SURC 1990;15A:279-82.)
Marcia L. Hixson,
MD, and Charles Stewart, BS, Little Rock, Ark.
S
capholunate diastasis and rotary subluxation of the scaphoid are seen frequently in patients with acute and chronic wrist pain. Treatment of these injuries is best done early; however, even under ideal conditions, the results of open or closed reduction, pinning, ligament repair, or ligament reconstruction are variable and often disappointing. ‘, ’ Valuable information has been gained through the work of Taleisnik, Lewis, Blair, Mayfield and others,3-6 who described the gross anatomy and the important stabilizing function of the radioscapholunate ligament and the scapholunate interosseous ligament. These two ligaments form an integrated complex, which has been shown to be the primary stabilizer of the scapholunate articulation and, along with the radioscaphocapitate ligament, is the principal stabilizer of the proximal pole of the scaphoid.7 Traumatic disruption of this ligamentous complex may lead to instability From the Section of Hand and Microsurgery,
paedic Surgery, University tle Rock, Ark. Received for publication 5, 1989.
of Arkansas
Department of Orthofor Medical Sciences, Lit-
Jan. 26, 1989; accepted in revised form May
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: Marcia L. Hixson, MD, Section of Hand and Microsurgery, Department of Orthopaedic Surgery, University of Arkansas for Medical Sciences, 4301 W. Markham, Little Rock, AR 72205. 3/I/14251
of the proximal pole of the scaphoid and to scapholunate diastasis. If this subluxation is not reduced, the forces that are transmitted through the carpus are concentrated abnormally, and posttraumatic arthritis results. Treatment of injuries to the radioscapholunate ligament and the scapholunate interosseous ligament is d;‘fficult and controversial. This is partly because of lgnorance regarding the anatomy and healing mechanisms of these ligaments. Research into this problem is in t&e developmental stage and has not yielded enough useful information to influence the results of clinical treatment. The purpose of this experiment was to define the microscopic anatomy, including the microvascular anatomy, of the radioscapholunate ligament of the wrist. This knowledge should serve as a foundation for further studies into the ligament’s response to injury and its ability to heal. Materials
and methods
Six fresh-frozen cadaver forearm-hand preparatisns were used in this study. Specimens first had x-ray fihns to rule out preexisting pathologic conditions. The limbs were then divided into two groups; the first group was used to identify the microvascular anatomy of the radioscapholunate ligament and the second group was used to demonstrate the general microscopic anatomy. Group I. The radial and ulnar arteries of four cadaver forearms were cannulated. The vascular system was flushed with warm heparinized saline solution until clear of blood. With the use of the method of Rhinelander and Stewart, a warmed mixture of India ink and THE JOURNAL OF HAND SURGERY
279
280
The Journal of HAND SURGERY
Hixson and Stewart
Fig. 1. Larger caliber perpendicular branches (arrows) pierce
Fig. 2. The midportion of the scapholunate interosseous lig-
the capsule to supply the intracapsular ligaments. (I?/ Radius, (L) lunate.
ament is avascular. (RJ Radius, (15)lunate, (S) scaphoid.
glycerine was injected at a pressure of 120 mm of mercury until dye emerged from small cuts on the fingertips. The specimens were cooled overnight, then dissected. All soft tissue superficial to the wrist capsule was removed after noting major arteries and their branches. A band saw was used to reduce the specimen to a block of tissue consisting of radius, scaphoid, and lunate with intact capsule and ligaments. These blocks were fixed in formalin and bleached for 24 hours with 6% hydrogen peroxide. They were then further cut into 2 mm-thick sections, with a 0.012-inch diamond wheel, some in the sagittal and others in the coronal plane. By use of a modified Spalteholtz technique these sections were decalcified and cleared as follows: The blocks were decalcified in a formic acid-sodium citrate mixture, washed in a 5% crystalline sodium sulphate solution, and dehydrated in ethanol. The blocks were cleared in benzene and in Spalteholtz fluid (methyl salicylate and benzyl benzoate). They were then examined
under the dissecting microscope and the polarized light microscope, and the vascular patterns were noted. Group II. The radioscapholunate ligaments, with their synovial envelopes, were harvested from two cadaver wrists. The ligaments were fixed and stained for light microscopy with hematoxylin and eosin stain, and also using Weigert’s resourcin-fuschin stain for elastic fibers. The fixed ligaments were cut in longitudinal and cross sections and viewed under the light and polarized light microscopes. Results Group I. Ail specimens were adequately perfused and were included in the study. Gross dissection showed a rich vascular plexus on the palmar aspect of the capsule, which appears to be derived mainly from branches of the radial and anterior interosseous arteries. Sagittal microscopic sections revealed numerous perpendicular branches that perforate the capsule at roughly 1 mm
Vol. HA, No. 2 March 1990
intervals. These perforators in turn send branches to the synovium of the radiocarpal joint and also directly to the intracapsular ligaments (Fig. 1). Small vessels course along the radioscapholunate ligament in the synovium and send frequent branches to the substance of the ligament. Arterioles are most numerous in the synovium near bony attachments. No branches were observed entering the ligaments from the bone. Vessels that course along the axis of the ligament continue into the bony fossae, where they terminate within the synovial attachment. The scapholunate interosseous ligament was best seen in the coronal sections. The ligament is continuous with the articular cartilage of the scaphoid and lunate but, as demonstrated under polarized light, is distinctly collaginous. In its midportion the ligament appears to be entirely avascular (Fig. 2). Dorsally and palmarly where it is surrounded by synovium, the interosseous ligament is well supplied by synovial arterioles, similar to the pattern observed in the extrinsic ligaments (Fig. 3). Group II. Observation of the detached radioscapholunate ligaments under light microscopy revealed multiple slender, longitudinally oriented collagen bundles populated by fibroblasts. The ligament is surrounded by a synovium rich in blood vessels, which send frequent branches into the substance of the ligament. Small vessels also course longitudinally among the collagen bundles (Fig. 4). The Weigert resourcin-fuschin stain for elastic fibers failed to reveal elastin in either the substance of the ligament or in the small caliber arterioles. Discussion The radioscapholunate ligament of the wrist is a slender, largely synovial structure, which is weak in comparison to other palmar intracapsular ligaments and in comparison to the scapholunate interosseous ligament.6 Nevertheless, its function appears to be important in maintaining wrist stability. Its gross description has been published previously in detail and will be summarized here. The ligament originates from the interfacet prominence of the palmar lip of the distal radius where its collagenous bundles interdigitate with the artitular cartilage. From this point, the ligament fans out distally, obliquely, and dorsally to attach to the proximal and palmar aspects of the scapholunate interosseous ligament, and to the articular surfaces of the scaphoid and lunate.’ The entire complex is enveloped in a synovial membrane that isolates the radioscapholunate ligament, the scapholunate interosseous liga-
Anatomy of radioscapholunate
ligament of wrist
281
Fig. 3. Dorsal cut of the scapholunate interosseous ligament showing abundant synovial-derived branches. (R) Radius, (L) lunate, (S) scaphoid. ment, and scapholunate joint from the radial carpal joint. Vessels from the metaphysis of the distal radius do not penetrate the ligament, and vessels in and around the ligament do not penetrate the lunate and scaphoid. The radioscapholunate ligament itself measures approximately 1 cm in length, 0.5 cm in width, and 0.2 to 0.4 cm in thickness. After the synovial covering has been removed, the ligament’s fibrous component is seen, which consists of parallel bundles of collagen fibers. With wrist movement after removal of the radioscaphocapitate and radiolunotriquetral (long radiolunate) ligaments, the radioscapholunate ligament is seen to be taut in extension and in ulnar deviation and is lax in flexion and in radial deviation. This implies that the radioscapholunate ligament acts as a restraint during wrist extension and ulnar deviation, keeping the proximal pole of the scaphoid anchored to the palmar lip of the radius while the distal pole is pulled into extension. Other ligaments appear to be responsible for stabilizing the proximal pole of the scaphoid when the
282
The Journal of HAND SURGERY
Hixson and Stewart
Fig. 4. Light microscopy shows that the radioscapholunate ligament is composed of regular collagen fibers. Arterioles (arrows) course around and through the collagen bundles. (S) synovium. (Original magnification X IO.)
wrist is in flexion or radial deviation (distal pole flexed).
Experiments on the anterior cruciate ligament of the knee suggest that the ligament heals by means of a fibrin clot.* The clot is thought to originate from the surrounding vasculature and organizes within the tom ligament to bridge the gap. Little is known about the radioscapholunate ligament’s response to injury or its mechanism or ability to repair itself. It, like the anterior cruciate ligament, is intracapsular, appears to have a similar anatomy, and is surrounded by a synovial envelope through which it receives its major blood supply. This study uses a reproducible method to demonstrate that the radioscapholunate and scapholunate interosseous ligaments have a complex and rich vascular supply. Further work should demonstrate the importance of a vascular response to injury. If arterial proliferation and ingrowth play an important part in healing of the ligament, approaches and methods can be developed that maximize this response. REFERENCES 1. Green DP, O’Brien ET. Open reduction of carpal dislocations: indications and operative SURG 1978;3:250-65.
techniques.
J HAND
2. Palmer AK, Dobyns MD, Linscheid RL. Management of posttraumatic instability of the wrist secondary to ligament rupture. J HAND SURG 1978;3:507-32. 3. Taleisnik J. Wrist: anatomy, function and injury. In: Am Acad Orthop Surgeons Instruct Course Lect. St. Louis: The CV Mosby Company, 1978:27-61. 4. Lewis OJ. Hamshem RJ, Buckmill TM. The anatomy of the wrist joint. J Anat 1979;106:539-52. 5. Berger RA, Blair WF, Crowninshield RO, Flatt AE. The scapholunate ligament. J HAND SURC 1982;7:87-91. 6. Mayfield JK, Johnson RP, Kilcoyne RF. The ligaments of the human wrist and their funtionai significance. Anat Ret 1986;186:417. 7,. Berger RA, Landsmeer JMF. The palmar radiocarpal ligaments: a study of adult and fetal human wrist joints. Iowa Orthop J 1985;5:32-41. 8. Amoczky SP, Rubin RM, Marshall JL, Microvasculature of the cruciate ligaments and its response to injury. J Bone Joint Surg 1979;61A:l221-9.