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Anatomy of the Collateral Ligaments of the Proximal Interphalangeal Joint
Anatomy of the Collateral Ligaments of the Proximal Interphalangeal Joint D. Mark Allison, MBBS, West Perth, Western Australia
Purpose: To study and clarify the anatomy of the proper collateral ligaments and accessory collateral ligaments of the proximal interphalangeal joint. Methods: The collateral ligaments of 8 proximal interphalangeal joints were dissected under an operating microscope to gain an appreciation of their fiber direction and the anatomy of their origin and insertion. Two undissected joints were studied histologically. Results: The proper collateral ligament was found to arise widely from dorsal and proximal to and from the fovea on the side of the head of the proximal phalanx and insert for some distance on most of the side of the base of the middle phalanx. The ligament is stout and its fibers are oriented parallel to the middle phalanx in all positions of the joint. The accessory collateral ligament was found to be a less substantial structure lying between the proper collateral ligament and the volar plate. Conclusions: The anatomy shown by this study is quite different from that shown in most of the anatomic and hand surgery literature, particularly in line drawings. (J Hand Surg 2005;30A: 1026 –1031. Copyright © 2005 by the American Society for Surgery of the Hand.) Key words: Anatomy, collateral ligaments, proximal interphalangeal joint.
The collateral ligaments of the proximal interphalangeal joint (PIPJ) have been divided into the proper collateral ligament (PCL) and the accessory collateral ligament (ACL).1,2 The PCL arises from the head of the proximal phalanx and inserts into the middle phalanx. The ACL inserts onto the volar plate. The anatomy of the PCL is shown varyingly in the hand surgery and anatomy literature. In general the From the Centre for Hand and Wrist Surgery, West Perth, Western Australia. Received for publication January 9, 2003; accepted in revised form May 30, 2005. 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. Corresponding author: D. Mark Allison, MBBS, The Centre for Hand and Wrist Surgery, PO Box 1674, West Perth, Western Australia 6872; e-mail: [email protected]. Copyright © 2005 by the American Society for Surgery of the Hand 0363-5023/05/30A05-0023$30.00/0 doi:10.1016/j.jhsa.2005.05.015
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orientation of the PCL is shown as oblique and/or cord-like and narrow in its anteroposterior dimension.3–12 Other investigators describe it as being a broader structure.2 The ACL usually is shown as a substantial structure that is triangular in shape and to which stabilizing properties are ascribed.2,3,8
Materials and Methods There were 10 fingers in this study. Eight PIPJs were dissected under an operating microscope. Five of these were frozen fingers that were allowed to thaw at room temperature. Three of these fingers were from 1 hand. In addition 3 fingers from another hand that was preserved in formalin were dissected. Because all fingers were amputation specimens it was established by history that none of the digits had any known PIPJ disease or injury. The skin and subcutaneous fat were removed from around the PIPJ distal and proximal to the joint. By
D. Mark Allison / Collateral Ligaments of the PIPJ
dividing the transverse retinacular ligament and elevating the extensor mechanism the lateral sides of the joints were exposed. The skin-anchoring ligaments and loose areola tissue were removed carefully from the sides of the joints. With these layers cleared the orientation of the collateral ligament was observed. The PCL was separated from the volar plate by incising the ACL. The PCL was removed gradually a few fibers at a time from origin to insertion to gain an appreciation of the fiber direction at different depths. Dissection photographs were taken frequently through the operating microscope. Once the PCL had been removed completely on one side of the joint the volar plate was sectioned, allowing the joint to be opened laterally and the opposite ligament to be observed from within the joint. The intact ligament then was divided transversely from dorsal to volar in the midsubstance to examine better the origin and insertion of the PCL. In the case of the origin this was performed by turning the severed ligament proximally and dorsally to show the distal extent of the bony attachment. After this the PCL was cut short at the proximal phalanx so only short stubs of fibers were left, thus making it easier to appreciate the outline of the origin. Because of the insubstantial nature of the ACL attempts at its dissection proved to be frustrating, even at these magnifications. The ACL is appreciated best in histologic section. The skin and subcutaneous tissue were removed in 2 additional fingers. These fingers were preserved in formalin and were decalcified. Transverse sections were taken and stained with hematoxylin and eosin or Masson’s trichrome. The histology was studied with routine light microscopy. One joint was fixed flexed so the sections were parallel to the middle phalanx but transverse through the head of the proximal phalanx; the other joint was straight so the joint was sectioned transversely along its whole length.
Results The orientation of the PCL is such that the dorsal edge parallels the middle phalanx (Fig. 1). The volar edge is a little more oblique than the dorsal edge so the ligament is seen to fan out a little from origin to insertion (Fig. 2A). The deeper fibers are angulated somewhat more volarly and thus are more oblique than the superficial fibers. This general longitudinal orientation was confirmed with the limited histology performed. The origin of the PCL is quite broad when viewed from its superficial aspect (Figs. 1, 2A) but when the
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Figure 1. Lateral view of the PIPJ (upward arrow) dorsal and (right arrow) distal. The superficial tissues have been removed and the PCL has been separated from the extensor mechanism. The ACL is difficult to see but the PCL is substantial. E, extensor tendon; D, deep surface of the extensor insertion; F, flexor tendons; P, PCL; A, ACL; T, transverse retinacular ligament.
cut ligament is flipped dorsally and proximally it is crescent shaped or similar to a circle segment (Fig. 2B, C). The PCL also is seen to arise from the proximal and dorsal sides of the concave area and for a considerable distance beyond, not from the center. The histologic sections show that it attaches to bone by Sharpey’s fibers. The insertion of the PCL into the middle phalanx is also by Sharpey’s fibers. It takes up most of the lateral side of the base of the middle phalanx and inserts over some distance proximal to distal (Figs. 1, 3). It was not seen to join the insertion of the volar plate at the critical corner but does extend close. The origin and insertion coincided with the roughened areas on the proximal and middle phalanges, respectively (Fig. 4). The ACL was an insubstantial structure and was difficult to identify separate from the PCL or the volar plate, particularly from the external aspect. On histologic sections it was of similar thickness to the transverse retinacular ligament. It inserted into the volar plate contiguous and deep to the transverse retinacular ligament. The fibers were oriented from dorsal to volar rather than longitudinally, as was the case in the PCL (Fig. 5). A synovial membrane lined the deep surface. On motion of the PCL there was differential gliding of the fibers. The fibers on the dorsal and volar edges of the PCL became exposed or hidden at different angles. The ligament became bunched prox-
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Figure 2. (A) Lateral view of the proximal phalanx at the PIPJ (upward arrow) dorsal and (right arrow) distal. The PCL has been cut and the middle phalanx has been removed. The extensive origin is seen and has been outlined. P, PCL; O, origin of the PCL. (B) (Upward arrow) dorsal and (right arrow) distal. The same specimen with the cut PCL flipped proximally to show the origin and the concave area or fovea devoid of ligament. The ligament has been outlined. O, origin PCL; CA, concave area or fovea, head proximal phalanx. (C) Composite of panels A and B to show the area occupied by the origin of the PCL. O, origin PCL.
imally as dorsal fibers rode over those more volar (Fig. 6). The joints seemed stable at all angles although no measurements were made of lateral deviation under stress. The PCL is a stout structure with multiple longitudinally oriented fibers, generally aligned with the direction of the longitudinal axis of the middle phalanx. No true cruciate or layered structure was observed. It takes up most of the side of the PIPJ. The ACL is thin with its fibers oriented in an anteroposterior direction. It is lined by synovial tissue. A schematic representation of the anatomy of the ligaments and how they relate to the other structures of the PIPJ is shown in Figure 7. During this study some distal interphalangeal joints were dissected by way of comparison; the pattern was similar to that in the PIPJ.
Discussion During procedures around the PIPJ I became aware of the differences between the observed anatomy and the anatomy shown commonly in the literature, particularly in line drawings. This study sought to clarify the anatomy. The collateral ligaments are important for stability, are injured commonly, and are implicated in the stiffness of the PIPJ. It is essential to have an accurate description of their anatomy. Bogumill13 described the insertions with respect to the growth plates but did not detail the structure of the ligament itself. The literature is concerned more with biomechanical studies or afflictions of the PIPJ and how the collateral ligaments are involved. One description of the PCL3 describes it arising from a concave fossa on the lateral aspect of each
D. Mark Allison / Collateral Ligaments of the PIPJ
Figure 3. The PIPJ viewed proximally and laterally (upward arrow) dorsal and (right arrow) distal. The PCL and the volar plate have been cut on one side, allowing the joint to be opened and the PCL on the other side to be viewed from within the joint. This shows the extensive insertion of the PCL. P, PCL; V, volar plate insertion; I, cut insertion of the PCL.
condyle and passing obliquely volarward and inserting onto the volar third of the side of the base of the middle phalanx. The ACL is described as being triangular in shape and inserting onto the volar plate. Kuczynski6 alluded to the dissection of fresh and preserved hands but came to conclusions quite different from those from this study. He depicted the PCL as cord-like and arising from the fovea. Other
Figure 4. Lateral view of the proximal and distal phalanges held together as they would be if articulated (upward arrow) dorsal and (right arrow) distal. The origin extends from the dorsal and proximal aspect of the concave area for some distance proximally. Similarly the insertion can be seen to be extensive in both vertical and longitudinal directions. O, origin PCL; I, insertion PCL; CA, concave area head of the proximal phalanx.
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Figure 5. Transverse low-power micrograph (magnification, ⫻10) through the head of the proximal phalanx showing the main structures around the PIPJ. C, central tendon of the extensor mechanism; L, lateral slip of the extensor tendon; P, origin PCL; T, transverse retinacular ligament; A, ACL; V, volar plate; F, flexor tendons.
investigators have used line drawings similar to his in reports on the stiff PIPJ.7,12 The description by Bowers2 was similar to the findings in this study but with some differences. Bowers2 described the origin of the PCL as being located eccentrically in the concave area on the side of the condyles of the proximal phalanx. This study found that the origin extended proximally and dorsally beyond this eccentric site in the concave area so
Figure 6. Lateral view of the PIPJ (upward arrow) dorsal and (right arrow) distal. Flexion of the PIPJ showing the bunching of the PCL fibers. E, extensor tendon partly cut away; H, proximal phalanx condyle; B, bunching of the PCL. Compare with Figure 1.
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Figure 7. Collateral ligaments and their relationship to the other structures of the PIPJ (Bowers2). E, extensor insertion; P, proper collateral ligament; I, insertion of PCL; O, origin of PCL delineated by dotted line; A, accessory collateral ligament; V, volar plate; S, synovial space.
that it was similar to a crescent or circle segment. This study found that the insertion of the PCL took up most of the side of the base of the middle phalanx whereas Bowers2 stated it took up three quarters. The critical corner, as defined by Bowers et al,14 is the area where the fibers of the volar plate and the PCL merge. This study did not observe this and a small bare area was seen between the 2 structures. Ligaments are thickenings in joint capsules for functional reasons.15 There is blending with surrounding collagenous tissue so the edges of a ligament may not always be identified precisely.8 Different dissectors may arrive at different conclusions. The PCL has been described as a cruciate structure in 2 layers.16 The present study suggests the deeper fibers are more oblique than the superficial but no true cruciate structure could be identified by careful dissection under magnification. No layers were seen on histology, as one would expect in a cruciate arrangement. Although the PCL is not the only lateral stabilizer of the PIPJ it is the most important.2,8 Biomechanically it would seem inefficient for the ligament to run obliquely from dorsal to volar as shown commonly in the literature. In the fully flexed position of the PIPJ, if the ligament were as shown in most line drawings there would be little lateral stability. This is not the case. The wide insertion of the PCL into the base of the middle phalanx is fixed. Any relative movement of the fibers occurs between this fixed area and the origin. Perhaps it is the unique shape of the origin that allows the large range of motion with such a thick ligament. If the ligament arose from the center
of the fovea as has been described3,6 then it would not be able to provide this range of movement without being thin or having a twisted construction or both. Neither was found in this study. This study found that both the origin and insertion of the PCL were in keeping with the skeletal anatomy (Fig. 4). The bony anatomy observed was different than that suggested by other investigators.2,6 The rough area of ligament insertion occupied most of the side of the middle phalanx and not just a volar tubercle. Similarly the rough area for the origin was extensive dorsal and proximal to the smoother fovea. The ACL is insubstantial. It was named first by Kaplan.1 This study showed that it arises largely from the volar edge of the PCL and inserts into the dorsolateral side of the volar plate, contiguous with and deeper to the insertion of the transverse retinacular ligament (Fig. 5). The fiber orientation is in an anterior to posterior direction; this supports a role in suspension of the volar plate.2 The ACL also serves to complete the joint capsule and act as a base for the synovial lining. Misconceptions about the anatomy of these important ligaments have led to assumptions in management of hand surgical problems, some of which may be inaccurate based on the information obtained in this study.17,18 –23 One deficiency of this study is that it was difficult to obtain an accurate appreciation of the precise orientation of the collagen fiber bundles in ligaments by dissection, even under the operating microscope. To an extent the act of dissection is destructive and one has to avoid creating artificial boundaries and shapes. The precise alignment of the collagen bundles might be studied better by histology with 3-dimensional reconstruction. Another deficiency was the small number of specimens studied. Although my numerous observations of the ligaments, during surgery on the PIPJ, are in keeping with the findings here, it is possible that more dissections would show racial, age, gender, or other individual variations. These ligaments are important. An accurate appreciation of their anatomy is essential in hand surgery. Although I have no doubt that most hand surgeons do have an accurate appreciation of these structures, this is not reflected in much of the literature. The author would like to thank Mr. James Savundra, FRACS, for assistance with the microdissections and logistical help.
D. Mark Allison / Collateral Ligaments of the PIPJ
References 1. Kaplan EB. Functional and surgical anatomy of the hand. 2nd ed. Philadelphia: JB Lippincott Company, 1965:39 – 45. 2. Bowers WH. The anatomy of the interphalangeal joints. In: Bowers WH, ed. The hand and upper limb. Vol 1. The interphalangeal joints. Edinburgh: Churchill Livingstone, 1987:2–13. 3. Glickel SZ, Barron OA, Eaton RG. Dislocations and ligament injuries in the digits. In: Green DP, Hotchkiss RN, Pederson WC, eds. Green’s operative hand surgery. 4th ed. New York: Churchill Livingstone, 1999:772–775. 4. Last RJ. Anatomy regional and applied. 6th ed. Edinburgh: Churchill Livingstone, 1978:105–106. 5. Grant JCB. An atlas of anatomy. 5th ed. Baltimore: Williams & Wilkins Co., 1962:Fig. 88,89,96. 6. Kuczynski K. The proximal interphalangeal joint. Anatomy and causes of stiffness in the fingers. J Bone Joint Surg 1968;50B:656 – 663. 7. Harrison DH. The stiff proximal interphalangeal joint. Hand 1977;9:102–108. 8. Kiefhaber TR, Stern PJ, Grood ES. Lateral stability of the proximal interphalangeal joint. J Hand Surg 1986;11A:661– 669. 9. Diao E, Eaton RG. Total collateral ligament excision for contractures of the proximal interphalangeal joint. J Hand Surg 1993;18A:395– 402. 10. Tonkin MA, Burke FD, Varian JPW. The proximal interphalangeal joint in Dupuytren’s disease. J Hand Surg 1985; 10B:358 –364. 11. Andrew JG. Contracture of the proximal interphalangeal joint in Dupuytren’s disease. J Hand Surg 1991;16B:446 – 448. 12. Abbiati G, Delaria G, Saporiti E, Petrolati M, Tremolada C. The treatment of chronic flexion contractures of the proximal interphalangeal joint. J Hand Surg 1995;20B:385–389.
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13. Bogumill GP. A morphologic study of the relationship of collateral ligaments to growth plates in the digits. J Hand Surg 1983;8:74 –79. 14. Bowers WH, Wolf JW Jr, Nehil JL, Bittinger S. The proximal interphalangeal joint volar plate. I. An anatomical and biomechanical study. J Hand Surg 1980;5:79 – 88. 15. Le Gros Clark WE. The tissues of the body. 5th ed. Oxford: Clarendon Press, 1965:175–177. 16. Von Hintringer W, Leixnering M. Knöcherne oder ligamentäre verletzungen am mittelgelenk und ihre behandlung. Handchir Mikrochir Plast Chir 1991;23:59 – 66. 17. Agee JM. Unstable fracture dislocations of the proximal interphalangeal joint of the fingers. A preliminary report of a new treatment technique. J Hand Surg 1978;3:386 – 389. 18. Inanami H, Ninomiya S, Okutsu I, Tarui T, Fujiwara N. Dynamic external finger fixator for fracture dislocation of the proximal interphalangeal joint. J Hand Surg 1993;18A: 160 –164. 19. Hastings H II, Ernst JMJ. Dynamic external fixation for fractures of the proximal interphalangeal joint. Hand Clin 1993;9:659 – 674. 20. Schenck RR. Dynamic traction and early passive movement for fractures of the proximal interphalangeal joint. J Hand Surg 1986;11A:850 – 858. 21. Allison DM. Fractures of the base of the middle phalanx treated by a dynamic external fixation device. J Hand Surg 1996;21B:305–310. 22. Stanley JK, Jones WA, Lynch MC. Percutaneous accessory collateral ligament release in the treatment of proximal interphalangeal joint flexion contracture. J Hand Surg 1986; 11B:360 –363. 23. Tonkin MA, Hughes J, Smith KL. Lateral band translocation for swan-neck deformity. J Hand Surg 1992;17A:260 –267.
Purpose: To study and clarify the anatomy of the proper collateral ligaments and accessory collateral ligaments of the proximal interphalangeal joint. Methods: The collateral ligaments of 8 proximal interphalangeal joints were dissected under an operating microscope to gain an appreciation of their fiber direction and the anatomy of their origin and insertion. Two undissected joints were studied histologically. Results: The proper collateral ligament was found to arise widely from dorsal and proximal to and from the fovea on the side of the head of the proximal phalanx and insert for some distance on most of the side of the base of the middle phalanx. The ligament is stout and its fibers are oriented parallel to the middle phalanx in all positions of the joint. The accessory collateral ligament was found to be a less substantial structure lying between the proper collateral ligament and the volar plate. Conclusions: The anatomy shown by this study is quite different from that shown in most of the anatomic and hand surgery literature, particularly in line drawings. (J Hand Surg 2005;30A: 1026 –1031. Copyright © 2005 by the American Society for Surgery of the Hand.) Key words: Anatomy, collateral ligaments, proximal interphalangeal joint.
The collateral ligaments of the proximal interphalangeal joint (PIPJ) have been divided into the proper collateral ligament (PCL) and the accessory collateral ligament (ACL).1,2 The PCL arises from the head of the proximal phalanx and inserts into the middle phalanx. The ACL inserts onto the volar plate. The anatomy of the PCL is shown varyingly in the hand surgery and anatomy literature. In general the From the Centre for Hand and Wrist Surgery, West Perth, Western Australia. Received for publication January 9, 2003; accepted in revised form May 30, 2005. 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. Corresponding author: D. Mark Allison, MBBS, The Centre for Hand and Wrist Surgery, PO Box 1674, West Perth, Western Australia 6872; e-mail: [email protected]. Copyright © 2005 by the American Society for Surgery of the Hand 0363-5023/05/30A05-0023$30.00/0 doi:10.1016/j.jhsa.2005.05.015
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orientation of the PCL is shown as oblique and/or cord-like and narrow in its anteroposterior dimension.3–12 Other investigators describe it as being a broader structure.2 The ACL usually is shown as a substantial structure that is triangular in shape and to which stabilizing properties are ascribed.2,3,8
Materials and Methods There were 10 fingers in this study. Eight PIPJs were dissected under an operating microscope. Five of these were frozen fingers that were allowed to thaw at room temperature. Three of these fingers were from 1 hand. In addition 3 fingers from another hand that was preserved in formalin were dissected. Because all fingers were amputation specimens it was established by history that none of the digits had any known PIPJ disease or injury. The skin and subcutaneous fat were removed from around the PIPJ distal and proximal to the joint. By
D. Mark Allison / Collateral Ligaments of the PIPJ
dividing the transverse retinacular ligament and elevating the extensor mechanism the lateral sides of the joints were exposed. The skin-anchoring ligaments and loose areola tissue were removed carefully from the sides of the joints. With these layers cleared the orientation of the collateral ligament was observed. The PCL was separated from the volar plate by incising the ACL. The PCL was removed gradually a few fibers at a time from origin to insertion to gain an appreciation of the fiber direction at different depths. Dissection photographs were taken frequently through the operating microscope. Once the PCL had been removed completely on one side of the joint the volar plate was sectioned, allowing the joint to be opened laterally and the opposite ligament to be observed from within the joint. The intact ligament then was divided transversely from dorsal to volar in the midsubstance to examine better the origin and insertion of the PCL. In the case of the origin this was performed by turning the severed ligament proximally and dorsally to show the distal extent of the bony attachment. After this the PCL was cut short at the proximal phalanx so only short stubs of fibers were left, thus making it easier to appreciate the outline of the origin. Because of the insubstantial nature of the ACL attempts at its dissection proved to be frustrating, even at these magnifications. The ACL is appreciated best in histologic section. The skin and subcutaneous tissue were removed in 2 additional fingers. These fingers were preserved in formalin and were decalcified. Transverse sections were taken and stained with hematoxylin and eosin or Masson’s trichrome. The histology was studied with routine light microscopy. One joint was fixed flexed so the sections were parallel to the middle phalanx but transverse through the head of the proximal phalanx; the other joint was straight so the joint was sectioned transversely along its whole length.
Results The orientation of the PCL is such that the dorsal edge parallels the middle phalanx (Fig. 1). The volar edge is a little more oblique than the dorsal edge so the ligament is seen to fan out a little from origin to insertion (Fig. 2A). The deeper fibers are angulated somewhat more volarly and thus are more oblique than the superficial fibers. This general longitudinal orientation was confirmed with the limited histology performed. The origin of the PCL is quite broad when viewed from its superficial aspect (Figs. 1, 2A) but when the
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Figure 1. Lateral view of the PIPJ (upward arrow) dorsal and (right arrow) distal. The superficial tissues have been removed and the PCL has been separated from the extensor mechanism. The ACL is difficult to see but the PCL is substantial. E, extensor tendon; D, deep surface of the extensor insertion; F, flexor tendons; P, PCL; A, ACL; T, transverse retinacular ligament.
cut ligament is flipped dorsally and proximally it is crescent shaped or similar to a circle segment (Fig. 2B, C). The PCL also is seen to arise from the proximal and dorsal sides of the concave area and for a considerable distance beyond, not from the center. The histologic sections show that it attaches to bone by Sharpey’s fibers. The insertion of the PCL into the middle phalanx is also by Sharpey’s fibers. It takes up most of the lateral side of the base of the middle phalanx and inserts over some distance proximal to distal (Figs. 1, 3). It was not seen to join the insertion of the volar plate at the critical corner but does extend close. The origin and insertion coincided with the roughened areas on the proximal and middle phalanges, respectively (Fig. 4). The ACL was an insubstantial structure and was difficult to identify separate from the PCL or the volar plate, particularly from the external aspect. On histologic sections it was of similar thickness to the transverse retinacular ligament. It inserted into the volar plate contiguous and deep to the transverse retinacular ligament. The fibers were oriented from dorsal to volar rather than longitudinally, as was the case in the PCL (Fig. 5). A synovial membrane lined the deep surface. On motion of the PCL there was differential gliding of the fibers. The fibers on the dorsal and volar edges of the PCL became exposed or hidden at different angles. The ligament became bunched prox-
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Figure 2. (A) Lateral view of the proximal phalanx at the PIPJ (upward arrow) dorsal and (right arrow) distal. The PCL has been cut and the middle phalanx has been removed. The extensive origin is seen and has been outlined. P, PCL; O, origin of the PCL. (B) (Upward arrow) dorsal and (right arrow) distal. The same specimen with the cut PCL flipped proximally to show the origin and the concave area or fovea devoid of ligament. The ligament has been outlined. O, origin PCL; CA, concave area or fovea, head proximal phalanx. (C) Composite of panels A and B to show the area occupied by the origin of the PCL. O, origin PCL.
imally as dorsal fibers rode over those more volar (Fig. 6). The joints seemed stable at all angles although no measurements were made of lateral deviation under stress. The PCL is a stout structure with multiple longitudinally oriented fibers, generally aligned with the direction of the longitudinal axis of the middle phalanx. No true cruciate or layered structure was observed. It takes up most of the side of the PIPJ. The ACL is thin with its fibers oriented in an anteroposterior direction. It is lined by synovial tissue. A schematic representation of the anatomy of the ligaments and how they relate to the other structures of the PIPJ is shown in Figure 7. During this study some distal interphalangeal joints were dissected by way of comparison; the pattern was similar to that in the PIPJ.
Discussion During procedures around the PIPJ I became aware of the differences between the observed anatomy and the anatomy shown commonly in the literature, particularly in line drawings. This study sought to clarify the anatomy. The collateral ligaments are important for stability, are injured commonly, and are implicated in the stiffness of the PIPJ. It is essential to have an accurate description of their anatomy. Bogumill13 described the insertions with respect to the growth plates but did not detail the structure of the ligament itself. The literature is concerned more with biomechanical studies or afflictions of the PIPJ and how the collateral ligaments are involved. One description of the PCL3 describes it arising from a concave fossa on the lateral aspect of each
D. Mark Allison / Collateral Ligaments of the PIPJ
Figure 3. The PIPJ viewed proximally and laterally (upward arrow) dorsal and (right arrow) distal. The PCL and the volar plate have been cut on one side, allowing the joint to be opened and the PCL on the other side to be viewed from within the joint. This shows the extensive insertion of the PCL. P, PCL; V, volar plate insertion; I, cut insertion of the PCL.
condyle and passing obliquely volarward and inserting onto the volar third of the side of the base of the middle phalanx. The ACL is described as being triangular in shape and inserting onto the volar plate. Kuczynski6 alluded to the dissection of fresh and preserved hands but came to conclusions quite different from those from this study. He depicted the PCL as cord-like and arising from the fovea. Other
Figure 4. Lateral view of the proximal and distal phalanges held together as they would be if articulated (upward arrow) dorsal and (right arrow) distal. The origin extends from the dorsal and proximal aspect of the concave area for some distance proximally. Similarly the insertion can be seen to be extensive in both vertical and longitudinal directions. O, origin PCL; I, insertion PCL; CA, concave area head of the proximal phalanx.
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Figure 5. Transverse low-power micrograph (magnification, ⫻10) through the head of the proximal phalanx showing the main structures around the PIPJ. C, central tendon of the extensor mechanism; L, lateral slip of the extensor tendon; P, origin PCL; T, transverse retinacular ligament; A, ACL; V, volar plate; F, flexor tendons.
investigators have used line drawings similar to his in reports on the stiff PIPJ.7,12 The description by Bowers2 was similar to the findings in this study but with some differences. Bowers2 described the origin of the PCL as being located eccentrically in the concave area on the side of the condyles of the proximal phalanx. This study found that the origin extended proximally and dorsally beyond this eccentric site in the concave area so
Figure 6. Lateral view of the PIPJ (upward arrow) dorsal and (right arrow) distal. Flexion of the PIPJ showing the bunching of the PCL fibers. E, extensor tendon partly cut away; H, proximal phalanx condyle; B, bunching of the PCL. Compare with Figure 1.
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Figure 7. Collateral ligaments and their relationship to the other structures of the PIPJ (Bowers2). E, extensor insertion; P, proper collateral ligament; I, insertion of PCL; O, origin of PCL delineated by dotted line; A, accessory collateral ligament; V, volar plate; S, synovial space.
that it was similar to a crescent or circle segment. This study found that the insertion of the PCL took up most of the side of the base of the middle phalanx whereas Bowers2 stated it took up three quarters. The critical corner, as defined by Bowers et al,14 is the area where the fibers of the volar plate and the PCL merge. This study did not observe this and a small bare area was seen between the 2 structures. Ligaments are thickenings in joint capsules for functional reasons.15 There is blending with surrounding collagenous tissue so the edges of a ligament may not always be identified precisely.8 Different dissectors may arrive at different conclusions. The PCL has been described as a cruciate structure in 2 layers.16 The present study suggests the deeper fibers are more oblique than the superficial but no true cruciate structure could be identified by careful dissection under magnification. No layers were seen on histology, as one would expect in a cruciate arrangement. Although the PCL is not the only lateral stabilizer of the PIPJ it is the most important.2,8 Biomechanically it would seem inefficient for the ligament to run obliquely from dorsal to volar as shown commonly in the literature. In the fully flexed position of the PIPJ, if the ligament were as shown in most line drawings there would be little lateral stability. This is not the case. The wide insertion of the PCL into the base of the middle phalanx is fixed. Any relative movement of the fibers occurs between this fixed area and the origin. Perhaps it is the unique shape of the origin that allows the large range of motion with such a thick ligament. If the ligament arose from the center
of the fovea as has been described3,6 then it would not be able to provide this range of movement without being thin or having a twisted construction or both. Neither was found in this study. This study found that both the origin and insertion of the PCL were in keeping with the skeletal anatomy (Fig. 4). The bony anatomy observed was different than that suggested by other investigators.2,6 The rough area of ligament insertion occupied most of the side of the middle phalanx and not just a volar tubercle. Similarly the rough area for the origin was extensive dorsal and proximal to the smoother fovea. The ACL is insubstantial. It was named first by Kaplan.1 This study showed that it arises largely from the volar edge of the PCL and inserts into the dorsolateral side of the volar plate, contiguous with and deeper to the insertion of the transverse retinacular ligament (Fig. 5). The fiber orientation is in an anterior to posterior direction; this supports a role in suspension of the volar plate.2 The ACL also serves to complete the joint capsule and act as a base for the synovial lining. Misconceptions about the anatomy of these important ligaments have led to assumptions in management of hand surgical problems, some of which may be inaccurate based on the information obtained in this study.17,18 –23 One deficiency of this study is that it was difficult to obtain an accurate appreciation of the precise orientation of the collagen fiber bundles in ligaments by dissection, even under the operating microscope. To an extent the act of dissection is destructive and one has to avoid creating artificial boundaries and shapes. The precise alignment of the collagen bundles might be studied better by histology with 3-dimensional reconstruction. Another deficiency was the small number of specimens studied. Although my numerous observations of the ligaments, during surgery on the PIPJ, are in keeping with the findings here, it is possible that more dissections would show racial, age, gender, or other individual variations. These ligaments are important. An accurate appreciation of their anatomy is essential in hand surgery. Although I have no doubt that most hand surgeons do have an accurate appreciation of these structures, this is not reflected in much of the literature. The author would like to thank Mr. James Savundra, FRACS, for assistance with the microdissections and logistical help.
D. Mark Allison / Collateral Ligaments of the PIPJ
References 1. Kaplan EB. Functional and surgical anatomy of the hand. 2nd ed. Philadelphia: JB Lippincott Company, 1965:39 – 45. 2. Bowers WH. The anatomy of the interphalangeal joints. In: Bowers WH, ed. The hand and upper limb. Vol 1. The interphalangeal joints. Edinburgh: Churchill Livingstone, 1987:2–13. 3. Glickel SZ, Barron OA, Eaton RG. Dislocations and ligament injuries in the digits. In: Green DP, Hotchkiss RN, Pederson WC, eds. Green’s operative hand surgery. 4th ed. New York: Churchill Livingstone, 1999:772–775. 4. Last RJ. Anatomy regional and applied. 6th ed. Edinburgh: Churchill Livingstone, 1978:105–106. 5. Grant JCB. An atlas of anatomy. 5th ed. Baltimore: Williams & Wilkins Co., 1962:Fig. 88,89,96. 6. Kuczynski K. The proximal interphalangeal joint. Anatomy and causes of stiffness in the fingers. J Bone Joint Surg 1968;50B:656 – 663. 7. Harrison DH. The stiff proximal interphalangeal joint. Hand 1977;9:102–108. 8. Kiefhaber TR, Stern PJ, Grood ES. Lateral stability of the proximal interphalangeal joint. J Hand Surg 1986;11A:661– 669. 9. Diao E, Eaton RG. Total collateral ligament excision for contractures of the proximal interphalangeal joint. J Hand Surg 1993;18A:395– 402. 10. Tonkin MA, Burke FD, Varian JPW. The proximal interphalangeal joint in Dupuytren’s disease. J Hand Surg 1985; 10B:358 –364. 11. Andrew JG. Contracture of the proximal interphalangeal joint in Dupuytren’s disease. J Hand Surg 1991;16B:446 – 448. 12. Abbiati G, Delaria G, Saporiti E, Petrolati M, Tremolada C. The treatment of chronic flexion contractures of the proximal interphalangeal joint. J Hand Surg 1995;20B:385–389.
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13. Bogumill GP. A morphologic study of the relationship of collateral ligaments to growth plates in the digits. J Hand Surg 1983;8:74 –79. 14. Bowers WH, Wolf JW Jr, Nehil JL, Bittinger S. The proximal interphalangeal joint volar plate. I. An anatomical and biomechanical study. J Hand Surg 1980;5:79 – 88. 15. Le Gros Clark WE. The tissues of the body. 5th ed. Oxford: Clarendon Press, 1965:175–177. 16. Von Hintringer W, Leixnering M. Knöcherne oder ligamentäre verletzungen am mittelgelenk und ihre behandlung. Handchir Mikrochir Plast Chir 1991;23:59 – 66. 17. Agee JM. Unstable fracture dislocations of the proximal interphalangeal joint of the fingers. A preliminary report of a new treatment technique. J Hand Surg 1978;3:386 – 389. 18. Inanami H, Ninomiya S, Okutsu I, Tarui T, Fujiwara N. Dynamic external finger fixator for fracture dislocation of the proximal interphalangeal joint. J Hand Surg 1993;18A: 160 –164. 19. Hastings H II, Ernst JMJ. Dynamic external fixation for fractures of the proximal interphalangeal joint. Hand Clin 1993;9:659 – 674. 20. Schenck RR. Dynamic traction and early passive movement for fractures of the proximal interphalangeal joint. J Hand Surg 1986;11A:850 – 858. 21. Allison DM. Fractures of the base of the middle phalanx treated by a dynamic external fixation device. J Hand Surg 1996;21B:305–310. 22. Stanley JK, Jones WA, Lynch MC. Percutaneous accessory collateral ligament release in the treatment of proximal interphalangeal joint flexion contracture. J Hand Surg 1986; 11B:360 –363. 23. Tonkin MA, Hughes J, Smith KL. Lateral band translocation for swan-neck deformity. J Hand Surg 1992;17A:260 –267.