CASE REPORT
Clear View of the Index Sesamoid: A Sign of Irreducible Metacarpophalangeal Joint Dislocation Walter W. Silberman, MD San Jose, California
If the index sesamoid bone is clearly seen in the joint following significant injury to the index metacarpophalangeal joint on radiographic examination, there is the probability of incarceraUon of the volar plate. In almost all cases, an open reduction will be necessary to re-establish the normal relationship between the second metacarpal and the proximal phalanx. In a case of irreducible dislocation of the index metacarpophalangeal joint, attempted reduction caused the injury to appear as a subluxation. Silberman WW: Clear view of the index sesamoid: A sign of irreducible metacarpophalangeal joint dislocation. JACEP 8:371-373, September 1979.
hand injury, metacarpophalangeal joint; injury, dislocation, hand
INTRODUCTION Although orthopedic surgeons have emphasized the pathomechanics of index metacarpophalangeal joint dislocations, 1 many physicians who treat this injury are still not aware of its surgical implication. Definitive treatment is often delayed by repeated futile attempts at closed reduction. A clear view of the index sesamoid on radiographic examination following trauma to the metacarpophalangeal joint is a sign that the injury is irreducible by closed means. 2 In other joint injuries the clinical or radiological differentiation of a subluxation from a dislocated joint may imply a difference as to the degree of injury, ease of reduction, and success of efforts to obtain an anatomical restoration of joint alignment. CASE REPORT A 16-year-old boy was practicing karate when he fell on his outstretched left upper extremity, sustaining hyperextension force to the index metacarpophalangeal joint. His karate opponent pulled the digit in an attempt at realignment. The victim arrived at the San Jose Hospital Emergency Department with typical findings of a dislocated index metacarpophalangeal joint. X-ray films revealed what appeared to be a minimal subluxation of the joint. After multiple attempts at closed reduction under local anesthesia, orthopedic consultation was obtained. On x-ray filYa the index sesamoid appeared unusually prominent and I suspected an irreducible dislocation of the index metacarAddress for reprints: Walter W. Silberman, MD, 5150 Graves Avenue, San Jose, California 95129. 8"9 (September) 1979
JACEP
371/53
Fig. 1. The index sesamoid clearly shown in a distal ulnar relationship to the second metacarpal on AP and oblique views. pophalangeal joint which, after being manipulated, appeared as a subluxation. In the operating room the skin was opened by a triple release incision, the first incision paralleling the proximal palmar crease. Then, longitudinal incisions were made in the natatory ligament and anterior fibrocartilaginous plate followed by a release incision of the superficial transverse ligament. The dislocation could not be reduced. The index sesamoid was found to be incarcerated within the joint. Following its removal from the joint with the attached volar plate, the joint was reduced and stable. The volar plate was reattached with 5-0 catgut sutures and the wound was closed. The digit was splinted for two weeks. The patient did well, and regained a full r a n g e of motion. F i g u r e 1 demonstrates the x-ray appearance of the index metacarpopha!angeal joint dislocation, showing the clear view of the index sesamoid. Figure 2 shows the postoperative reduction. Figure 3 shows the operative findings.
DISCUSSION In 1957, Kaplan ~ published the explanation for the irreducible nature of c e r t a i n index m e t a c a r pophalangeal joint dislocations. He described the angtomical derange-
54/372
Fig. 2. After open reduction of the index sesamoid had been restored to the normal overlapping relationship to the second metacarpal on AP and oblique views.
Fig. 3. Operative f i n d i n g s of the index sesamoid in the volar plate shown in the forceps after removal of the joint.
Fig. 4. Schematic drawing of the entry of the metacarpal head in the irreducible i n d e x metacarpophalangeal joint dislocation.
ment of the structures entrapping the metacarpal head as involving the superficial transverse ligament proximally, the n a t a t o r y ligament distally, the flexor tendons ulnarwards, and the lumbricals radially. A triple release of the constriction permitted a stable open reduction. Figure 4 demonstrates the pathomechanics of first metacarpal entrapment~ Other authors4, 5 have verified this description and added unusual cases. Barash ~ and Hunt et al 7 described finding a volar plate traumatically detached at its proximal insertion on the volar aspect of the
metacarpal neck. The free end was consistently found to pass through the joint space and to be dorsal to the metacarpal head. The wedging of the volar plate within the joint is a mechanical obstruction to closed reduction. Murphy and Stark 1 described the clinical appearance of the injured digit in response to the hyperextem sion force applied to it, usually following a fall on the outstretched hand. In the characteristic deformity, the index finger is deviated ulnar" wards, rotated to overlap the long finger, and the distal two joints are
JACEP
8"9 (September) 197g
semiflexed. The index finger a p p e a r s short and motion at the metacarp o p h a l a n g e a l j o i n t is restricted. Out of t e n c a s e s , 1 one d i s l o c a t i o n w a s successfully reduced by closed m a n ipulation and three others, seen acutely, were successfully t r e a t e d by open r e d u c t i o n . The r e m a i n i n g six injuries had h a d inadequate, unsuccessful a t t e m p t s at open reduction. Subsequent operative intervention still left the patients with compromised function. Recently, Berenfield a n d Wesely s reported on a more fortunate r e s u l t in a p a t i e n t who was reoperated on t h r e e months following inadequate i n i t i a l surgery. K a p l a n 3 differentiated a complete dislocation from a s u b l u x a t i o n . He c o n s i d e r e d the s u b l u x a t i o n a m i n o r i n j u r y t h a t in most instances was easily reduced, often by the p a t i e n t himself. However, in r e v i e w i n g the cases reported in t h e l i t e r a t u r e , 1,2 a l m o s t all p a t i e n t s h a d h a d a t t e m p t s a t m a n i p u l a t i o n of the injured digit by themselves, bystanders, or their p h y s i c i a n , o f t e n r e d u c i n g t h e app e a r a n c e of a f r a n k d i s l o c a t i o n to that of a s u b l u x a t e d joint. Sweterlitsch et al 9 reported two cases of e n t r a p m e n t of t h e i n d e x sesamoid within the metacarpop h a l a n g e a l joint. It was t h e i r opinion that prior cases described in the lite r a t u r e r e p r e s e n t e d r e s i d u a l s from incomplete reduction of f r a n k dorsal dislocations. They recommended res e c t i o n of t h e s e s a m o i d w i t h t h e volar plate and reported a functional range of motion as the end r e s u l t in their two cases. They did describe t h e sesamoid as d i s t a l l y p o s i t i o n e d associated w i t h l a t e r a l w i d e n i n g of the joint space as the subtle radiological finding in t h e i r cases. In m y opinion, because of the int i m a t e a s s o c i a t i o n of the s e s a m o i d with the volar plate, the so-called ent r a p m e n t of the sesamoid is m e r e l y
8:9 (September) 1979
an a n a t o m i c a l concomitant to the ent r a p m e n t o f t h e v o l a r p l a t e as a whole when it acts as the m e c h a n i c a l blockade to closed reduction. Therefore, the surgical release o f the dislocated j o i n t r e q u i r e s the so-called triple r e l e a s e of K a p l a n 3 a n d t h e removal of the o b s t r u c t i n g v o l a r plate with associated sesamoid. Following this procedure, a stable reduction is o b t a i n e d w i t h o u t t h e n e c e s s i t y of r e s e c t i n g the volar plate or sesamoid. When present, the sesamoids, which overlie the head of the m e t a carpals, a p p e a r at age 12. They are u s u a l l y s i n g l e in t h e s e c o n d a n d t h i r d r a y s but m a y be double in the first, fourth a n d fifth rays. F u r t h e r investigations have revealed the sporadic occurrence of sesamoid bones in p r o x i m i t y to m o s t of t h e o t h e r finger joints. TM A single index sesamoid is p r e s e n t in about 70% of hands, lo According to F l a t t , 11 the n o r m a l position of the index sesamoid is w i t h the r a d i a l h a l f of the volar plate partially replacing the cartilaginous portion of the accessory p a l m a r liga m e n t . T h e u p p e r e x t r e m i t y sesamolds a r e r a r e l y c l i n i c a l l y signific a n t b u t m a y cause locking of t h e joint.
CONCLUSION It is a d v i s a b l e to define s k e l e t a l t r a u m a by two x - r a y views projected a t 90 d e g r e e a n g l e s to each other. Although the thumb metacarpop h a l a n g e a l j o i n t c a n be d e f i n e d in this m a n n e r , it is technically difficult to o b t a i n and i n t e r p r e t a true l a t e r a l view of the index m e t a c a r p o p h a l a n geal joint. In r e v i e w i n g this case as well as cases r e p o r t e d by others,4, 7 the clear view of the sesamoid due to its shift d i s t a l l y and u s u a l l y ulnarw a r d s s e e m s to be a v a l i d r a d i o graphic finding indicating e n t r a p m e n t of t h e v o l a r p l a t e a n d s e s a m o i d
JACEP
w i t h i n t h e joint. Recognition of this fact should a l e r t the t r e a t i n g physician to the i n e v i t a b i l i t y of open reduction for a n a t o m i c a l r e p o s i t i o n i n g of the joint.
REFERENCES 1. Murphy AF, Stark HH: Closed dislocation of the metacarpophalangeal joint of the index finger. J Bone Joint Surg 49A:1576-1586, 1967. 2. Greene DR, Terry GC: Complex dislocation of the metacarpophalangeal joint. J Bone Joint Surg 55A:1180-1186, 1972. 3. Kaplan EB: Dorsal dislocation of the metacarpophalangeal joint of the index finger. J Bone Joint Surg 39A:1081-1086, 1957. 4. von Rarer W: Irreducible dislocation of the metacarpophalangeal joint of the finger. Clin Orthop 35"171-173, 1964. 5. Milch H: Subluxation of the index metacarpophalangeal joint of the index finger. J Bone Joint Surg 47A.522-523, 1965. 6. Barash HL: An unusual case of dorsal dislocation of the metacarpophalangeal joint of the index finger. Clin Orthop 83:122-123, 1972. 7. Hunt JC, Watts HB, Glascow JP: Dorsal dislocation of the metacarpophalangeal joint of the index finger with particular reference to open dislocation. J Bone Joint Surg 49A:1572-1578, 1967. 8. Berenfield PA, Wesely MS: DOrsal dislocation of the metacm'pophalangeal joint of the index finger treated by late open reduction. J Bone Joint Surg 54A:13111313, 1972. 9. Sweterlitsch PR, Torg JS, Pollack H: Entrapment of a sesamoid in the index metacarpophalangeal joint. J Bone Joint Surg 51A:995-998, 1969. 10. Kohler AL, Zimmer EA: Borderlands of the Normal and Early Pathologic in Skeletal Roentgenology, ed 11. New York,
Grune and Stratton, 1968, pp 882-883. 11. Flatt AE: Recurrent locking of an index finger. J Bone Joint Surg 40A: 1128-1130, 1958.
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Clear View of the Index Sesamoid: A Sign of Irreducible Metacarpophalangeal Joint Dislocation Walter W. Silberman, MD San Jose, California
If the index sesamoid bone is clearly seen in the joint following significant injury to the index metacarpophalangeal joint on radiographic examination, there is the probability of incarceraUon of the volar plate. In almost all cases, an open reduction will be necessary to re-establish the normal relationship between the second metacarpal and the proximal phalanx. In a case of irreducible dislocation of the index metacarpophalangeal joint, attempted reduction caused the injury to appear as a subluxation. Silberman WW: Clear view of the index sesamoid: A sign of irreducible metacarpophalangeal joint dislocation. JACEP 8:371-373, September 1979.
hand injury, metacarpophalangeal joint; injury, dislocation, hand
INTRODUCTION Although orthopedic surgeons have emphasized the pathomechanics of index metacarpophalangeal joint dislocations, 1 many physicians who treat this injury are still not aware of its surgical implication. Definitive treatment is often delayed by repeated futile attempts at closed reduction. A clear view of the index sesamoid on radiographic examination following trauma to the metacarpophalangeal joint is a sign that the injury is irreducible by closed means. 2 In other joint injuries the clinical or radiological differentiation of a subluxation from a dislocated joint may imply a difference as to the degree of injury, ease of reduction, and success of efforts to obtain an anatomical restoration of joint alignment. CASE REPORT A 16-year-old boy was practicing karate when he fell on his outstretched left upper extremity, sustaining hyperextension force to the index metacarpophalangeal joint. His karate opponent pulled the digit in an attempt at realignment. The victim arrived at the San Jose Hospital Emergency Department with typical findings of a dislocated index metacarpophalangeal joint. X-ray films revealed what appeared to be a minimal subluxation of the joint. After multiple attempts at closed reduction under local anesthesia, orthopedic consultation was obtained. On x-ray filYa the index sesamoid appeared unusually prominent and I suspected an irreducible dislocation of the index metacarAddress for reprints: Walter W. Silberman, MD, 5150 Graves Avenue, San Jose, California 95129. 8"9 (September) 1979
JACEP
371/53
Fig. 1. The index sesamoid clearly shown in a distal ulnar relationship to the second metacarpal on AP and oblique views. pophalangeal joint which, after being manipulated, appeared as a subluxation. In the operating room the skin was opened by a triple release incision, the first incision paralleling the proximal palmar crease. Then, longitudinal incisions were made in the natatory ligament and anterior fibrocartilaginous plate followed by a release incision of the superficial transverse ligament. The dislocation could not be reduced. The index sesamoid was found to be incarcerated within the joint. Following its removal from the joint with the attached volar plate, the joint was reduced and stable. The volar plate was reattached with 5-0 catgut sutures and the wound was closed. The digit was splinted for two weeks. The patient did well, and regained a full r a n g e of motion. F i g u r e 1 demonstrates the x-ray appearance of the index metacarpopha!angeal joint dislocation, showing the clear view of the index sesamoid. Figure 2 shows the postoperative reduction. Figure 3 shows the operative findings.
DISCUSSION In 1957, Kaplan ~ published the explanation for the irreducible nature of c e r t a i n index m e t a c a r pophalangeal joint dislocations. He described the angtomical derange-
54/372
Fig. 2. After open reduction of the index sesamoid had been restored to the normal overlapping relationship to the second metacarpal on AP and oblique views.
Fig. 3. Operative f i n d i n g s of the index sesamoid in the volar plate shown in the forceps after removal of the joint.
Fig. 4. Schematic drawing of the entry of the metacarpal head in the irreducible i n d e x metacarpophalangeal joint dislocation.
ment of the structures entrapping the metacarpal head as involving the superficial transverse ligament proximally, the n a t a t o r y ligament distally, the flexor tendons ulnarwards, and the lumbricals radially. A triple release of the constriction permitted a stable open reduction. Figure 4 demonstrates the pathomechanics of first metacarpal entrapment~ Other authors4, 5 have verified this description and added unusual cases. Barash ~ and Hunt et al 7 described finding a volar plate traumatically detached at its proximal insertion on the volar aspect of the
metacarpal neck. The free end was consistently found to pass through the joint space and to be dorsal to the metacarpal head. The wedging of the volar plate within the joint is a mechanical obstruction to closed reduction. Murphy and Stark 1 described the clinical appearance of the injured digit in response to the hyperextem sion force applied to it, usually following a fall on the outstretched hand. In the characteristic deformity, the index finger is deviated ulnar" wards, rotated to overlap the long finger, and the distal two joints are
JACEP
8"9 (September) 197g
semiflexed. The index finger a p p e a r s short and motion at the metacarp o p h a l a n g e a l j o i n t is restricted. Out of t e n c a s e s , 1 one d i s l o c a t i o n w a s successfully reduced by closed m a n ipulation and three others, seen acutely, were successfully t r e a t e d by open r e d u c t i o n . The r e m a i n i n g six injuries had h a d inadequate, unsuccessful a t t e m p t s at open reduction. Subsequent operative intervention still left the patients with compromised function. Recently, Berenfield a n d Wesely s reported on a more fortunate r e s u l t in a p a t i e n t who was reoperated on t h r e e months following inadequate i n i t i a l surgery. K a p l a n 3 differentiated a complete dislocation from a s u b l u x a t i o n . He c o n s i d e r e d the s u b l u x a t i o n a m i n o r i n j u r y t h a t in most instances was easily reduced, often by the p a t i e n t himself. However, in r e v i e w i n g the cases reported in t h e l i t e r a t u r e , 1,2 a l m o s t all p a t i e n t s h a d h a d a t t e m p t s a t m a n i p u l a t i o n of the injured digit by themselves, bystanders, or their p h y s i c i a n , o f t e n r e d u c i n g t h e app e a r a n c e of a f r a n k d i s l o c a t i o n to that of a s u b l u x a t e d joint. Sweterlitsch et al 9 reported two cases of e n t r a p m e n t of t h e i n d e x sesamoid within the metacarpop h a l a n g e a l joint. It was t h e i r opinion that prior cases described in the lite r a t u r e r e p r e s e n t e d r e s i d u a l s from incomplete reduction of f r a n k dorsal dislocations. They recommended res e c t i o n of t h e s e s a m o i d w i t h t h e volar plate and reported a functional range of motion as the end r e s u l t in their two cases. They did describe t h e sesamoid as d i s t a l l y p o s i t i o n e d associated w i t h l a t e r a l w i d e n i n g of the joint space as the subtle radiological finding in t h e i r cases. In m y opinion, because of the int i m a t e a s s o c i a t i o n of the s e s a m o i d with the volar plate, the so-called ent r a p m e n t of the sesamoid is m e r e l y
8:9 (September) 1979
an a n a t o m i c a l concomitant to the ent r a p m e n t o f t h e v o l a r p l a t e as a whole when it acts as the m e c h a n i c a l blockade to closed reduction. Therefore, the surgical release o f the dislocated j o i n t r e q u i r e s the so-called triple r e l e a s e of K a p l a n 3 a n d t h e removal of the o b s t r u c t i n g v o l a r plate with associated sesamoid. Following this procedure, a stable reduction is o b t a i n e d w i t h o u t t h e n e c e s s i t y of r e s e c t i n g the volar plate or sesamoid. When present, the sesamoids, which overlie the head of the m e t a carpals, a p p e a r at age 12. They are u s u a l l y s i n g l e in t h e s e c o n d a n d t h i r d r a y s but m a y be double in the first, fourth a n d fifth rays. F u r t h e r investigations have revealed the sporadic occurrence of sesamoid bones in p r o x i m i t y to m o s t of t h e o t h e r finger joints. TM A single index sesamoid is p r e s e n t in about 70% of hands, lo According to F l a t t , 11 the n o r m a l position of the index sesamoid is w i t h the r a d i a l h a l f of the volar plate partially replacing the cartilaginous portion of the accessory p a l m a r liga m e n t . T h e u p p e r e x t r e m i t y sesamolds a r e r a r e l y c l i n i c a l l y signific a n t b u t m a y cause locking of t h e joint.
CONCLUSION It is a d v i s a b l e to define s k e l e t a l t r a u m a by two x - r a y views projected a t 90 d e g r e e a n g l e s to each other. Although the thumb metacarpop h a l a n g e a l j o i n t c a n be d e f i n e d in this m a n n e r , it is technically difficult to o b t a i n and i n t e r p r e t a true l a t e r a l view of the index m e t a c a r p o p h a l a n geal joint. In r e v i e w i n g this case as well as cases r e p o r t e d by others,4, 7 the clear view of the sesamoid due to its shift d i s t a l l y and u s u a l l y ulnarw a r d s s e e m s to be a v a l i d r a d i o graphic finding indicating e n t r a p m e n t of t h e v o l a r p l a t e a n d s e s a m o i d
JACEP
w i t h i n t h e joint. Recognition of this fact should a l e r t the t r e a t i n g physician to the i n e v i t a b i l i t y of open reduction for a n a t o m i c a l r e p o s i t i o n i n g of the joint.
REFERENCES 1. Murphy AF, Stark HH: Closed dislocation of the metacarpophalangeal joint of the index finger. J Bone Joint Surg 49A:1576-1586, 1967. 2. Greene DR, Terry GC: Complex dislocation of the metacarpophalangeal joint. J Bone Joint Surg 55A:1180-1186, 1972. 3. Kaplan EB: Dorsal dislocation of the metacarpophalangeal joint of the index finger. J Bone Joint Surg 39A:1081-1086, 1957. 4. von Rarer W: Irreducible dislocation of the metacarpophalangeal joint of the finger. Clin Orthop 35"171-173, 1964. 5. Milch H: Subluxation of the index metacarpophalangeal joint of the index finger. J Bone Joint Surg 47A.522-523, 1965. 6. Barash HL: An unusual case of dorsal dislocation of the metacarpophalangeal joint of the index finger. Clin Orthop 83:122-123, 1972. 7. Hunt JC, Watts HB, Glascow JP: Dorsal dislocation of the metacarpophalangeal joint of the index finger with particular reference to open dislocation. J Bone Joint Surg 49A:1572-1578, 1967. 8. Berenfield PA, Wesely MS: DOrsal dislocation of the metacm'pophalangeal joint of the index finger treated by late open reduction. J Bone Joint Surg 54A:13111313, 1972. 9. Sweterlitsch PR, Torg JS, Pollack H: Entrapment of a sesamoid in the index metacarpophalangeal joint. J Bone Joint Surg 51A:995-998, 1969. 10. Kohler AL, Zimmer EA: Borderlands of the Normal and Early Pathologic in Skeletal Roentgenology, ed 11. New York,
Grune and Stratton, 1968, pp 882-883. 11. Flatt AE: Recurrent locking of an index finger. J Bone Joint Surg 40A: 1128-1130, 1958.
373/55
