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Hook of the hamate fracture in athletes
HOOK OF THE HAMATE FRACTURE IN ATHLETES THOMAS C. BINZER, MD, and PETER R. CARTER, MD
Hook of the hamate fracture in athletes is discussed. Patient history and physical examination, the mechanisms of injury, and pertinent anatomy is emphasized from a clinical perspective. Recommendations for treatment are made. KEY WORDS: hamate hook fracture, athlete
Isolated fractures of the hook of the hamate are frequently overlooked sports injuries. Although it is most common in athletes who use equipment with a handle like golf clubs, baseball bats, or rackets, the fracture occurs less often after a fall on an outstretched hand. Fractures of the body of the hamate require a massive crush-injury not seen in sporting activity. In this report the focus is on hook of the hamate fractures in athletes.
HISTORY Fractures of the hamate, particularly the hook of the hamate, have been considered a relatively rare injury with only approximately 100 cases reported in the literature. Although the true number of instances of the hook of the hamate fractures is not well known, it accounts for less than 2% of all carpal fractures in most reportsJ The first case report was in 1908 when Albers-Schonberg reported an unusual carpal fracture. 2 The first report in the American Journal of Bone and Joint Surgery was by Henry Milch in 1934.2 Since that time, with more heightened awareness, fracture of the hook of the hamate may be more common than is reflected in the literature. 3-1°
MECHANISM OF INJURY Fractures of the hamate are the result of two possible mechanisms of injury: indirect trauma or a direct blow caused by a handle. In golfers and baseball players, the butt end of the handle of the club or bat respectively is held in the nondominant hand. 11 Therefore, in these athletes, hamate fractures most commonly involve the nondominant hand. The golfer or baseball player usually grasps the handle of the club or bat over the distal ulnar aspect of the palm using a power grip. This places the handle in close proximity to the hook of the hamate and when the grip is' relaxed or the force generated by a swing too great, the butt end of the handle can cause direct trauma and fracture the hamate (Fig 1). In golfers, fractures often occur when the club head accidentally strikes the ground. 11 In baseball From the Texas Scottish Rite Hospital for Children, Dallas, TX. Address reprint requests to Peter R. Carter, MD, Texas Scottish Rite Hospital for Children, 2222 Welborn, Dallas, TX 75219. Copyright © 1996 by W.B. Saunders Company 1060-1872/96/0404-0004505.00/0
242
players, more fractures are seen at the end of forceful checked swings as opposed to swings that make contact. Conversely, in athletes who participate in racket sports (ie, tennis and racquetball), hook of the hamate fractures are noted in the dominant hands and usually occur when the player loses control of the racket while trying to make a shot31 Usually, fractures related to indirect forces are the result of a fall on an outstretched hand when forces are transmitted to the hook by its many muscular and ligamentous attachments resulting in a fracture. A fracture of the hook of the hamate may occur at any point along these attachments but usually occurs near the base.
PHYSICAL EXAMINATION The most important physical finding is point tenderness in the palm over the hook of the hamate. Paradoxically, pain is occasionally noted dorsally and sometimes tenderness to direct pressure over the dorsum of the hamate may present. Rarely there is less tenderness in the palm than over the dorsal aspect of the hamate and the carpometacarpal joints of the little and ring fingers. 12An ulnar motor and sensory deficit, a median nerve deficit in the form of carpal tunnel syndrome and involvement of both nerves have been reported. ~3 Occasionally, a weakly positive Allen's test may be present. ~2 Symptoms of partial or complete tendon rupture may be part of the patient's complaints. These include the following: pain with grip, crepitance with finger motion, and eventually loss of active flexion at the distal interphalangeal joint. The incidence of tendon rupture has been reported as high as 15% to 20O/o.14
ANATOMY To understand the treatment and mechanism of injury of hamate fractures in athletes, a clear knowledge of the basic bony, ligamentous, and vascular anatomy in this area of the hand is required. A brief review is presented. Topographically, the body of the hamate is located on the dorsal and ulnar aspect of the wrist at the base of the fourth and fifth metacarpal. The hook is a palmar osseous protrusion from the ulnar aspect of the base. To locate it topographically, project a line from the pisiform to the center of the head of the index metacarpal. The hook is
Operative Techniques in Sports Medicine, Vol 4, No 4 (October), 1996: pp 242-247
TC L ~ ~t/
~_
~/
~'~
/~~
C
H P U TCL FDP V
Fig 1. Note the proximity of the hook of the hamate to the fifth profundus tendon to the motor branch of the ulnar nerve and the placement of the baseball bat near the hook.
Superior view of Guyon's Canal
palpable as a vague but firm prominence along this line 1.5 to 3 cm distal to the pisiform (Fig 2). The hook serves as an ulnar mooring for the transverse carpal ligament. Two of the hypothenar intrinsics (the flexor digiti minimi brevis and the opponens digiti minimi), take origin from the hook and diverge distally to their insertions on the little finger. The pisohamate ligament, a distal extension of the flexor carpi ulnaris after it inserts on the pisiform, inserts on the hook and forms a floor of Guyon's canal. In this compartment, in direct apposition to the ulnar side of the hook of the hamate, the ulnar nerve and artery pass into the palm.
Hamate Pisiform Ulnar n. Transverse carpal lig. Flexor digitorum profundus
The radial border of the hook provides a trochlea for the flexor digitorum profundus tendon of the little finger during power grip (Fig 3). The course of the motor branch of the ulnar nerve is particularly important in surgical treatment of fractures of the hook of the hamate. The nerve passes into the hand =
%
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ior
linimi /
Tra car
i
",
.5-3cm
\
hate lig.
~arpi m.
Hamate
Pisiform
Fig 2. Topographical location of pisiform hamate hook and metacarpal head. HAMATE HOOK FRACTURES IN ATHLETES
Fig 3. Anatomic drawing showing the relation of the tendons and their vascular structures to the hamate hook.
243
outside of the carpal tunnel through Guyon's canal radial to the pisiform but on the ulnar side of the hook of the hamate (Fig 3). The motor branch of the ulnar nerve usually divides midway between the proximal and distal margins of the flexor retinaculum distal to the midpoint of the pisiform. The motor branch then dives between the flexor digiti minimi and the abductor digiti minimi and passes through the substance of the opponens digiti minimi, giving off branches to all three muscles as it passes. 12 The motor branch is in close proximity to the ulnar and distal surfaces of the hook and is vulnerable during excision. The more superficial sensory branches of the ulnar nerve lie close to the tip of the hook in or beneath the skin or fibro fatty pad. 14 Occasionally the hamate may have two separate centers of ossification and be bipartite. Separate ossification centers are rarely unilateral. This is a fact that is useful in distinguishing the bipartite hamate from a true hamate fracture. 15 The blood supply to the hamate is from the following three sources (Fig 4). (1) The palmar hamate surface, which receives its blood supply from the palmar carpal branch and deep palmar branch of the ulnar artery. (2) The dorsal hamate surface, which receives its nutrient vessels from a ulnar dorsal carpal artery, but may be supplied in part by an anterior interosseous artery perforator. All blood supply of the hamate perforates distally resulting in a proximal tip of the hamate body (like the scaphoid proximal pole) predominately surviving on the intraosseous blood supply. 16
Medial view of the hamate ,,
Distal
Proximal Fig 4. Blood supply of the hook of the hamate.
244
I|
(3) Finally, the blood supply of the hook of the hamate is provided by one to two small vessels that enter the bone through the medial base and at the tip of the hook. These vessels anastomose with each other but are separate from the blood supply to the body. 17 The hamate hook is therefore well supplied with blood proximally and distally and avascular necrosis of the hook after fracture has not been reported.
DIFFERENTIAL DIAGNOSIS Differential diagnosis of hamate fractures includes thromboses of the ulnar artery, flexor tendonitis, fracture or dislocation of the carpometacarpal joint of the ring or little finger, sprain of the ligaments about the ulnar side of the wrist and contusion of the hamate hook. 12
RADIOLOGIC STUDIES Although the diagnosis of any type of hamate fracture depends on radiographic confirmation, routine anteroposterior and lateral views of the wrist are rarely helpful in hook fractures. The diagnosis of fracture of the hamate is often delayed because the signs and symptoms maybe nonspecific and routine radiographs of the wrist fail to show the fracture. Four techniques have been described to show fractures of the hook of the hamate. They are (1) the carpal tunnel view, (2) the supinated radially deviated oblique view, (3) lateral tomography, and (4) the computed tomography (CT) scan. The orientation of the fracture surface determines which method is most helpful. The carpal tunnel view is relatively simple and best for showing fractures in the coronal plane. The problem with this method is that it requires positioning the wrist in forced hyperextension. Many patients, especially during the acute phase of the injury, have enough pain and limitation of motion that the wrist cannot be positioned properly to make use of this x-ray technique. 2,3,1s Careful technique is important (Fig 5). The partial supination oblique view of the wrist in maximum radial deviation provides a profile view of the hook of the hamate and is useful in showing fractures that are oriented more parallel to the frontal plane (Fig 6). Accurate positioning of the wrist for this view is critical because rotation of the wrist a few degrees from the correct position can project the hamate behind the carpal arch. When learning to position patients for this view, image intensification and spot film techniques may be instructional. Once learned, this technique, like the carpal tunnel view, is often made in the orthopedist's office. Lateral tomography in i to 2 m m increments is a reliable method of examination and some authors feel this may be the best way to show the fracture. 14This is especially useful for fractures in the axial plane (Fig 7). The use of the CT scan has been described as the definitive imaging technique for showing hamate fractures. The CT scan has the advantage of bilateral comparison and can be helpful in excluding congenital variations of the hook of the hamate (the os hamuli proprium). It is also useful in fractures at the very base of the hook where it
BINZER AND CARTER
offers little advantage over excision which generally produces excellent results.
TREATMENT OF NONUNION Nonunion in hook of the hamate fractures is often seen in patients in whom the diagnosis is delayed. The vascular supply of the hamate described previously, is not believed to be the cause of nonunion. 21Most investigators feel that a delay in bone healing because of forces transmitted from soft tissue attachments on the hook of the hamate and the resulting micromotion at the fracture is the most significant factor in development of nonunion. 16 Patients with nonunion may be grouped in two categories. They are painful and painless. Most recognized nonunions are painful and excision of the entire hook of the hamate is the generally accepted treatment. 2° This reduces the risk of later tendon damage and possible neurovascular compromise. Excision of the hook of the hamate is associated with a complicate rate of 3%. 1,2°These include weakness, painful grasp, altered sensibility, and scar tenderness. All of these usually resolve within a few weeks. More severe complications are caused by the surgical exposure rather than to the actual excision of the fragment. 2° A precise knowledge of the regions anatomy and careful operative technique are mandatory. Injury to the ulnar and median nerves has been reported. This may result from laceration, contusion, pressure from hemor-
Fig 5. Positioning for the carpal tunnel view. Seat the patient so that the pronated forearm lies on the x-ray film holder. Place a one inch thick radiolucent pad between the wrist and the film holder. Either hold or have the patient hold the wrist in maximum dorsiflexion by pulling the finger tips dorsally. Direct the x-ray beam approximately one inch distal to the base of the fourth metacarpal, and angle the tube approximately 25 ° toward the horizontal from the long axis of the hand. (Reprinted with permission. 11)
attaches to the body that may not be visualized with the standard carpal tunnel view ~9(Fig 8).
TREATMENT OF FRESH FRACTURES Frequently, the diagnosis is delayed in athletes who are often treated initially for a wrist sprain or tendonitis. After demonstration of the fresh fracture on x-ray, some investigators recommend immobilization in a short arm cast. The cast should include the metacarpophalangeal joints of the ring and little fingers and be worn for 6 to 8 weeks. 2° Others report less success with conservative treatment and recommend primarily excision of the fragment. 2° For the acute displaced fracture there are two options for open treatment. They are (1) open reduction internal fixation or (2) excision of the fragment. Although open reduction and internal fixation is technically possible, it
HAMATE HOOK FRACTURES IN ATHLETES
Fig 6. X-ray view of oblique fracture of hamate hook.
245
this fracture be treated even when asymptomatic. Treatment of ruptured flexor tendons should be done at the same time of hook excision by a competent hand surgeon. This requires bridge grafts or transfers of the ruptured tendon to intact remaining profundus tendons. 23
SURGICAL APPROACHES
Fig 7. Lateral tomogram showing transverse fracture through hamate. (Reprinted with permission TM from Churchill Livingston, New York from Bishop AT, Bechenbaugh RD: Fracture of the hamate hook. J Hand Surg 13A:135-139, 1988.)
rhage, edema, or later development of perineural fibrosis. 22 To prevent this complication, careful exploration and protection of nerves is always indicated at the time of excision. Although painless nonunion is less common, its treatment is more controversial. Most investigators recommend removal of the fragment even in painless cases to prevent late complication of tendon rupture. 12Others advocate that treatment be delayed until signs and symptoms of tendon damage or neurological compromise are present. 2 Fraying tendonitis of the flexor digitorum profundus and superficialis tendons to the small and ring fingers caused by the irregular surface of the hamate nonunion has been reported. Complete rupture of a flexor tendon has been reported to occur in 15% to 20% of cases. 14 Usually the tendon of the little finger ruptures first followed by the ring finger tendon. This high rate of tendon rupture strongly supports the recommendation that nonunions of
Fig 8. CT scan of fracture of the hook of the hamate note normal versus abnormal.
246
When operative treatment is selected, two slightly different approaches have been reported. In both, careful dissection using tourniquet hemostatis is mandatory to prevent damage to the ulnar artery and nerve. Special care should be taken with the motor branch that hugs the distal and ulnar surface of the hook. Some investigators feel that the standard carpal tunnel approach with careful dissection to prevent neurovascular damage and identification of the hook fragment is the preferred approach. 22 We prefer the palmar approach described by Eaton and Littler5 2,24On a line between a pisiform and the head of the index metacarpal, the hamate is palpable 1.5 to 3 cm distal to the pisiform bone (Fig 2). A curvilinear palmar incision 6 to 8 cm long is adequate for exposure (Fig 9). The ulnar neurovascular bundle must be first identified in Guyon's canal, traced to the hamate and carefully retracted. Using subperiosteal dissection, the ununited bone fragment is removed intact. It is important to again emphasize the need for particular care to protect the motor branch of the ulnar nerve. When motion at the fracture site is present, a pseudoarthrosis interface is seen at the site of the nonunion. However, a tight fibrous union is occasionally present and motion may be much less apparent. After removal of the fragment, the anterior surface at the base of the hamate is made smooth to prevent tendon irritation. Only the skin is closed and the wrist and hand is immobilized with 10 ° to 20 ° wrist extension in a short plaster dressing for 2 to 3 weeks. Later active motion and rehabilitation of grip is encouraged. Wound induration frequently persists for 6 to 10 weeks and responds to persistent massage. By 8 to 10 weeks after excision the patient is usually able to carry out all activities. Return to symmetrical grip strength may be expected. 12
Fig 9. Incision preferred by authors. (Reprinted with permission. 24) BINZER AND CARTER
THE AUTHORS' PREFERRED MANAGEMENT When the fracture is less than 3 weeks old and minimally displaced (less than 2 mm) we recommend a trial of n o n o p e r a t i v e t r e a t m e n t . This c o n s i s t s of a s h o r t a r m cast t h a t i n c l u d e s the m e t a c a r p o p h a l a n g e a l j o i n t s of the r i n g a n d little f i n g e r s for a 6 - w e e k - p e r i o d . If s y m p t o m s persist, w e p r e f e r e x c i s i o n of the f r a g m e n t . I n this case w e f a v o r c o m p l e t e e x c i s i o n of the h o o k . We d o n o t r e c o m m e n d o p e n r e d u c t i o n a n d i n t e r n a l f i x a t i o n b e c a u s e the r e s u l t s of e x c i s i o n are p r e d i c t a b l y g o o d a n d a s s o c i a t e d risk of o p e n r e d u c t i o n a n d i n t e r n a l f i x a t i o n s e e m s u n n e c e s s a r y . For a n y n o n u n i o n , e v e n if p a i n l e s s , w e r e c o m m e n d e x c i s i o n of the hook.
REFERENCES 1. Frymoyer (ed): Orthopaedic Knowledge Update IV. Chicago, IL, AAOS, 1993, pp 370-372 2. Milch H: Fracture of the hamate bone. J Bone Joint Surg 16:459-462, 1934 3. Whalen JL, Bishop AT, Linscheid RL: Nonoperative treatment of acute hamate hook fractures. J Hand Surg 17:507-511, 1992 4. Ohshio I, Ogino T, Miyake A: Dislocation of the hamate associated with fracture of the trapezial ridge. J Hand Surg 11A:658-660,1986 5. McClain EJ, Boyes JH: Missed fractures of the greater multangular. J Bone Joint Surg 48A:1525-1528,1966 6. Ogunro O: Fracture of the body of the hamate bone. J Hand Surg 8:353-355, 1983 7. Thomas AP, Birch R: An unusual hamate fracture. Hand 15:281-286, 1983 8. Spinner M: Kaplan's Functional and Surgical Anatomy of the Hand (ed 3). Philadelphia, PA, Lippincott, 1984
HAMATE HOOK FRACTURES IN ATHLETES
9. Smith III P, Wright TW, Wallace PF, et ah Excision of the hook of the hamate: A retrospective survey and review of the literature. J Hand Surg 13A:612-615,1988 10. Amadio P, Talelsink J: Green's 2nd Edition of Hand Surgery. New York, NY, Churchill Livingston, 1993, pp 850-852 11. Stark HH, Jobe FW, Boyes JH, et al: Fracture of the hook of the hamate in athletes. J Bone Joint Surg 59A:575-582,1977 12. Carter PR, Eaton RG, Littler JW: Ununited fracture of the hook of the hamate. J Bone Joint Surg 59A:583-588,1977 13. Manske PR: Fracture of the hook of the hamate presenting as a carpal tunnel syndrome. Hand 10:181, 1978 14. Bishop AT, Bechenbaugh RD: Fracture of the hamate hook. J Hand Surg 13A:135-139,1988 15. Okuhara T, Matsui T, Sugimoto Y: Spontaneous rupture of flexor tendons of a little finger due to projection of the hook of the hamate. A case report. Hand 14:71-74, 1982 16. Van Demark RE, Parke WW: Avascular necrosis of the hamate: A case report with reference to the hamate blood supply. J Hand Surg 17A:1086-1090, 1992 17. Panagis JS, Gelberman RH, Taleisnik J, et al: The arterial anatomy of the human carpus. Part II. The intraosseous vascularity. J Hand Surg 8:375-382, 1983 18. Hart VL, Gaynor V: Roentgenographic study of the carpal canal. J Bone Joint Surg 23:382-383,1941 19. Egawa M, Asai T: Fracture of the hook of the hamate: Report of six cases and the suitability of computerized tomography. J Hand Surg 8A:393-398, 1983 20. Culp RW, Lemel M, Taras JS: Complications of Common Carpal Injuries. Hand Clin 10:149-155, 1994 21. Foucher G, Schuind ]7, Merle M, et ah Fractures of the hook of the hamate. J Hand Surg 10B:205-210,1985 22. Blair WE Kilpatrick WC, Omer GE: Open fracture of hook of the hamate: A case report. Clin Orthop 163:180-184, 1982 23. Boulas HJ, Milek MA: Hook of the hamate fractures. Diagnosis, treatment and complications. Orthop Rev 19:518~529,1990 24. Eaton RG, Morris J: What's New with Bones--in Littler JW, Cramer LM, Smith JW (eds): Symposium on Reconstructive Hand Surgery, St. Louis, MO, Mosby, 1974, pp 274-278
247
Hook of the hamate fracture in athletes is discussed. Patient history and physical examination, the mechanisms of injury, and pertinent anatomy is emphasized from a clinical perspective. Recommendations for treatment are made. KEY WORDS: hamate hook fracture, athlete
Isolated fractures of the hook of the hamate are frequently overlooked sports injuries. Although it is most common in athletes who use equipment with a handle like golf clubs, baseball bats, or rackets, the fracture occurs less often after a fall on an outstretched hand. Fractures of the body of the hamate require a massive crush-injury not seen in sporting activity. In this report the focus is on hook of the hamate fractures in athletes.
HISTORY Fractures of the hamate, particularly the hook of the hamate, have been considered a relatively rare injury with only approximately 100 cases reported in the literature. Although the true number of instances of the hook of the hamate fractures is not well known, it accounts for less than 2% of all carpal fractures in most reportsJ The first case report was in 1908 when Albers-Schonberg reported an unusual carpal fracture. 2 The first report in the American Journal of Bone and Joint Surgery was by Henry Milch in 1934.2 Since that time, with more heightened awareness, fracture of the hook of the hamate may be more common than is reflected in the literature. 3-1°
MECHANISM OF INJURY Fractures of the hamate are the result of two possible mechanisms of injury: indirect trauma or a direct blow caused by a handle. In golfers and baseball players, the butt end of the handle of the club or bat respectively is held in the nondominant hand. 11 Therefore, in these athletes, hamate fractures most commonly involve the nondominant hand. The golfer or baseball player usually grasps the handle of the club or bat over the distal ulnar aspect of the palm using a power grip. This places the handle in close proximity to the hook of the hamate and when the grip is' relaxed or the force generated by a swing too great, the butt end of the handle can cause direct trauma and fracture the hamate (Fig 1). In golfers, fractures often occur when the club head accidentally strikes the ground. 11 In baseball From the Texas Scottish Rite Hospital for Children, Dallas, TX. Address reprint requests to Peter R. Carter, MD, Texas Scottish Rite Hospital for Children, 2222 Welborn, Dallas, TX 75219. Copyright © 1996 by W.B. Saunders Company 1060-1872/96/0404-0004505.00/0
242
players, more fractures are seen at the end of forceful checked swings as opposed to swings that make contact. Conversely, in athletes who participate in racket sports (ie, tennis and racquetball), hook of the hamate fractures are noted in the dominant hands and usually occur when the player loses control of the racket while trying to make a shot31 Usually, fractures related to indirect forces are the result of a fall on an outstretched hand when forces are transmitted to the hook by its many muscular and ligamentous attachments resulting in a fracture. A fracture of the hook of the hamate may occur at any point along these attachments but usually occurs near the base.
PHYSICAL EXAMINATION The most important physical finding is point tenderness in the palm over the hook of the hamate. Paradoxically, pain is occasionally noted dorsally and sometimes tenderness to direct pressure over the dorsum of the hamate may present. Rarely there is less tenderness in the palm than over the dorsal aspect of the hamate and the carpometacarpal joints of the little and ring fingers. 12An ulnar motor and sensory deficit, a median nerve deficit in the form of carpal tunnel syndrome and involvement of both nerves have been reported. ~3 Occasionally, a weakly positive Allen's test may be present. ~2 Symptoms of partial or complete tendon rupture may be part of the patient's complaints. These include the following: pain with grip, crepitance with finger motion, and eventually loss of active flexion at the distal interphalangeal joint. The incidence of tendon rupture has been reported as high as 15% to 20O/o.14
ANATOMY To understand the treatment and mechanism of injury of hamate fractures in athletes, a clear knowledge of the basic bony, ligamentous, and vascular anatomy in this area of the hand is required. A brief review is presented. Topographically, the body of the hamate is located on the dorsal and ulnar aspect of the wrist at the base of the fourth and fifth metacarpal. The hook is a palmar osseous protrusion from the ulnar aspect of the base. To locate it topographically, project a line from the pisiform to the center of the head of the index metacarpal. The hook is
Operative Techniques in Sports Medicine, Vol 4, No 4 (October), 1996: pp 242-247
TC L ~ ~t/
~_
~/
~'~
/~~
C
H P U TCL FDP V
Fig 1. Note the proximity of the hook of the hamate to the fifth profundus tendon to the motor branch of the ulnar nerve and the placement of the baseball bat near the hook.
Superior view of Guyon's Canal
palpable as a vague but firm prominence along this line 1.5 to 3 cm distal to the pisiform (Fig 2). The hook serves as an ulnar mooring for the transverse carpal ligament. Two of the hypothenar intrinsics (the flexor digiti minimi brevis and the opponens digiti minimi), take origin from the hook and diverge distally to their insertions on the little finger. The pisohamate ligament, a distal extension of the flexor carpi ulnaris after it inserts on the pisiform, inserts on the hook and forms a floor of Guyon's canal. In this compartment, in direct apposition to the ulnar side of the hook of the hamate, the ulnar nerve and artery pass into the palm.
Hamate Pisiform Ulnar n. Transverse carpal lig. Flexor digitorum profundus
The radial border of the hook provides a trochlea for the flexor digitorum profundus tendon of the little finger during power grip (Fig 3). The course of the motor branch of the ulnar nerve is particularly important in surgical treatment of fractures of the hook of the hamate. The nerve passes into the hand =
%
\
ior
linimi /
Tra car
i
",
.5-3cm
\
hate lig.
~arpi m.
Hamate
Pisiform
Fig 2. Topographical location of pisiform hamate hook and metacarpal head. HAMATE HOOK FRACTURES IN ATHLETES
Fig 3. Anatomic drawing showing the relation of the tendons and their vascular structures to the hamate hook.
243
outside of the carpal tunnel through Guyon's canal radial to the pisiform but on the ulnar side of the hook of the hamate (Fig 3). The motor branch of the ulnar nerve usually divides midway between the proximal and distal margins of the flexor retinaculum distal to the midpoint of the pisiform. The motor branch then dives between the flexor digiti minimi and the abductor digiti minimi and passes through the substance of the opponens digiti minimi, giving off branches to all three muscles as it passes. 12 The motor branch is in close proximity to the ulnar and distal surfaces of the hook and is vulnerable during excision. The more superficial sensory branches of the ulnar nerve lie close to the tip of the hook in or beneath the skin or fibro fatty pad. 14 Occasionally the hamate may have two separate centers of ossification and be bipartite. Separate ossification centers are rarely unilateral. This is a fact that is useful in distinguishing the bipartite hamate from a true hamate fracture. 15 The blood supply to the hamate is from the following three sources (Fig 4). (1) The palmar hamate surface, which receives its blood supply from the palmar carpal branch and deep palmar branch of the ulnar artery. (2) The dorsal hamate surface, which receives its nutrient vessels from a ulnar dorsal carpal artery, but may be supplied in part by an anterior interosseous artery perforator. All blood supply of the hamate perforates distally resulting in a proximal tip of the hamate body (like the scaphoid proximal pole) predominately surviving on the intraosseous blood supply. 16
Medial view of the hamate ,,
Distal
Proximal Fig 4. Blood supply of the hook of the hamate.
244
I|
(3) Finally, the blood supply of the hook of the hamate is provided by one to two small vessels that enter the bone through the medial base and at the tip of the hook. These vessels anastomose with each other but are separate from the blood supply to the body. 17 The hamate hook is therefore well supplied with blood proximally and distally and avascular necrosis of the hook after fracture has not been reported.
DIFFERENTIAL DIAGNOSIS Differential diagnosis of hamate fractures includes thromboses of the ulnar artery, flexor tendonitis, fracture or dislocation of the carpometacarpal joint of the ring or little finger, sprain of the ligaments about the ulnar side of the wrist and contusion of the hamate hook. 12
RADIOLOGIC STUDIES Although the diagnosis of any type of hamate fracture depends on radiographic confirmation, routine anteroposterior and lateral views of the wrist are rarely helpful in hook fractures. The diagnosis of fracture of the hamate is often delayed because the signs and symptoms maybe nonspecific and routine radiographs of the wrist fail to show the fracture. Four techniques have been described to show fractures of the hook of the hamate. They are (1) the carpal tunnel view, (2) the supinated radially deviated oblique view, (3) lateral tomography, and (4) the computed tomography (CT) scan. The orientation of the fracture surface determines which method is most helpful. The carpal tunnel view is relatively simple and best for showing fractures in the coronal plane. The problem with this method is that it requires positioning the wrist in forced hyperextension. Many patients, especially during the acute phase of the injury, have enough pain and limitation of motion that the wrist cannot be positioned properly to make use of this x-ray technique. 2,3,1s Careful technique is important (Fig 5). The partial supination oblique view of the wrist in maximum radial deviation provides a profile view of the hook of the hamate and is useful in showing fractures that are oriented more parallel to the frontal plane (Fig 6). Accurate positioning of the wrist for this view is critical because rotation of the wrist a few degrees from the correct position can project the hamate behind the carpal arch. When learning to position patients for this view, image intensification and spot film techniques may be instructional. Once learned, this technique, like the carpal tunnel view, is often made in the orthopedist's office. Lateral tomography in i to 2 m m increments is a reliable method of examination and some authors feel this may be the best way to show the fracture. 14This is especially useful for fractures in the axial plane (Fig 7). The use of the CT scan has been described as the definitive imaging technique for showing hamate fractures. The CT scan has the advantage of bilateral comparison and can be helpful in excluding congenital variations of the hook of the hamate (the os hamuli proprium). It is also useful in fractures at the very base of the hook where it
BINZER AND CARTER
offers little advantage over excision which generally produces excellent results.
TREATMENT OF NONUNION Nonunion in hook of the hamate fractures is often seen in patients in whom the diagnosis is delayed. The vascular supply of the hamate described previously, is not believed to be the cause of nonunion. 21Most investigators feel that a delay in bone healing because of forces transmitted from soft tissue attachments on the hook of the hamate and the resulting micromotion at the fracture is the most significant factor in development of nonunion. 16 Patients with nonunion may be grouped in two categories. They are painful and painless. Most recognized nonunions are painful and excision of the entire hook of the hamate is the generally accepted treatment. 2° This reduces the risk of later tendon damage and possible neurovascular compromise. Excision of the hook of the hamate is associated with a complicate rate of 3%. 1,2°These include weakness, painful grasp, altered sensibility, and scar tenderness. All of these usually resolve within a few weeks. More severe complications are caused by the surgical exposure rather than to the actual excision of the fragment. 2° A precise knowledge of the regions anatomy and careful operative technique are mandatory. Injury to the ulnar and median nerves has been reported. This may result from laceration, contusion, pressure from hemor-
Fig 5. Positioning for the carpal tunnel view. Seat the patient so that the pronated forearm lies on the x-ray film holder. Place a one inch thick radiolucent pad between the wrist and the film holder. Either hold or have the patient hold the wrist in maximum dorsiflexion by pulling the finger tips dorsally. Direct the x-ray beam approximately one inch distal to the base of the fourth metacarpal, and angle the tube approximately 25 ° toward the horizontal from the long axis of the hand. (Reprinted with permission. 11)
attaches to the body that may not be visualized with the standard carpal tunnel view ~9(Fig 8).
TREATMENT OF FRESH FRACTURES Frequently, the diagnosis is delayed in athletes who are often treated initially for a wrist sprain or tendonitis. After demonstration of the fresh fracture on x-ray, some investigators recommend immobilization in a short arm cast. The cast should include the metacarpophalangeal joints of the ring and little fingers and be worn for 6 to 8 weeks. 2° Others report less success with conservative treatment and recommend primarily excision of the fragment. 2° For the acute displaced fracture there are two options for open treatment. They are (1) open reduction internal fixation or (2) excision of the fragment. Although open reduction and internal fixation is technically possible, it
HAMATE HOOK FRACTURES IN ATHLETES
Fig 6. X-ray view of oblique fracture of hamate hook.
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this fracture be treated even when asymptomatic. Treatment of ruptured flexor tendons should be done at the same time of hook excision by a competent hand surgeon. This requires bridge grafts or transfers of the ruptured tendon to intact remaining profundus tendons. 23
SURGICAL APPROACHES
Fig 7. Lateral tomogram showing transverse fracture through hamate. (Reprinted with permission TM from Churchill Livingston, New York from Bishop AT, Bechenbaugh RD: Fracture of the hamate hook. J Hand Surg 13A:135-139, 1988.)
rhage, edema, or later development of perineural fibrosis. 22 To prevent this complication, careful exploration and protection of nerves is always indicated at the time of excision. Although painless nonunion is less common, its treatment is more controversial. Most investigators recommend removal of the fragment even in painless cases to prevent late complication of tendon rupture. 12Others advocate that treatment be delayed until signs and symptoms of tendon damage or neurological compromise are present. 2 Fraying tendonitis of the flexor digitorum profundus and superficialis tendons to the small and ring fingers caused by the irregular surface of the hamate nonunion has been reported. Complete rupture of a flexor tendon has been reported to occur in 15% to 20% of cases. 14 Usually the tendon of the little finger ruptures first followed by the ring finger tendon. This high rate of tendon rupture strongly supports the recommendation that nonunions of
Fig 8. CT scan of fracture of the hook of the hamate note normal versus abnormal.
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When operative treatment is selected, two slightly different approaches have been reported. In both, careful dissection using tourniquet hemostatis is mandatory to prevent damage to the ulnar artery and nerve. Special care should be taken with the motor branch that hugs the distal and ulnar surface of the hook. Some investigators feel that the standard carpal tunnel approach with careful dissection to prevent neurovascular damage and identification of the hook fragment is the preferred approach. 22 We prefer the palmar approach described by Eaton and Littler5 2,24On a line between a pisiform and the head of the index metacarpal, the hamate is palpable 1.5 to 3 cm distal to the pisiform bone (Fig 2). A curvilinear palmar incision 6 to 8 cm long is adequate for exposure (Fig 9). The ulnar neurovascular bundle must be first identified in Guyon's canal, traced to the hamate and carefully retracted. Using subperiosteal dissection, the ununited bone fragment is removed intact. It is important to again emphasize the need for particular care to protect the motor branch of the ulnar nerve. When motion at the fracture site is present, a pseudoarthrosis interface is seen at the site of the nonunion. However, a tight fibrous union is occasionally present and motion may be much less apparent. After removal of the fragment, the anterior surface at the base of the hamate is made smooth to prevent tendon irritation. Only the skin is closed and the wrist and hand is immobilized with 10 ° to 20 ° wrist extension in a short plaster dressing for 2 to 3 weeks. Later active motion and rehabilitation of grip is encouraged. Wound induration frequently persists for 6 to 10 weeks and responds to persistent massage. By 8 to 10 weeks after excision the patient is usually able to carry out all activities. Return to symmetrical grip strength may be expected. 12
Fig 9. Incision preferred by authors. (Reprinted with permission. 24) BINZER AND CARTER
THE AUTHORS' PREFERRED MANAGEMENT When the fracture is less than 3 weeks old and minimally displaced (less than 2 mm) we recommend a trial of n o n o p e r a t i v e t r e a t m e n t . This c o n s i s t s of a s h o r t a r m cast t h a t i n c l u d e s the m e t a c a r p o p h a l a n g e a l j o i n t s of the r i n g a n d little f i n g e r s for a 6 - w e e k - p e r i o d . If s y m p t o m s persist, w e p r e f e r e x c i s i o n of the f r a g m e n t . I n this case w e f a v o r c o m p l e t e e x c i s i o n of the h o o k . We d o n o t r e c o m m e n d o p e n r e d u c t i o n a n d i n t e r n a l f i x a t i o n b e c a u s e the r e s u l t s of e x c i s i o n are p r e d i c t a b l y g o o d a n d a s s o c i a t e d risk of o p e n r e d u c t i o n a n d i n t e r n a l f i x a t i o n s e e m s u n n e c e s s a r y . For a n y n o n u n i o n , e v e n if p a i n l e s s , w e r e c o m m e n d e x c i s i o n of the hook.
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HAMATE HOOK FRACTURES IN ATHLETES
9. Smith III P, Wright TW, Wallace PF, et ah Excision of the hook of the hamate: A retrospective survey and review of the literature. J Hand Surg 13A:612-615,1988 10. Amadio P, Talelsink J: Green's 2nd Edition of Hand Surgery. New York, NY, Churchill Livingston, 1993, pp 850-852 11. Stark HH, Jobe FW, Boyes JH, et al: Fracture of the hook of the hamate in athletes. J Bone Joint Surg 59A:575-582,1977 12. Carter PR, Eaton RG, Littler JW: Ununited fracture of the hook of the hamate. J Bone Joint Surg 59A:583-588,1977 13. Manske PR: Fracture of the hook of the hamate presenting as a carpal tunnel syndrome. Hand 10:181, 1978 14. Bishop AT, Bechenbaugh RD: Fracture of the hamate hook. J Hand Surg 13A:135-139,1988 15. Okuhara T, Matsui T, Sugimoto Y: Spontaneous rupture of flexor tendons of a little finger due to projection of the hook of the hamate. A case report. Hand 14:71-74, 1982 16. Van Demark RE, Parke WW: Avascular necrosis of the hamate: A case report with reference to the hamate blood supply. J Hand Surg 17A:1086-1090, 1992 17. Panagis JS, Gelberman RH, Taleisnik J, et al: The arterial anatomy of the human carpus. Part II. The intraosseous vascularity. J Hand Surg 8:375-382, 1983 18. Hart VL, Gaynor V: Roentgenographic study of the carpal canal. J Bone Joint Surg 23:382-383,1941 19. Egawa M, Asai T: Fracture of the hook of the hamate: Report of six cases and the suitability of computerized tomography. J Hand Surg 8A:393-398, 1983 20. Culp RW, Lemel M, Taras JS: Complications of Common Carpal Injuries. Hand Clin 10:149-155, 1994 21. Foucher G, Schuind ]7, Merle M, et ah Fractures of the hook of the hamate. J Hand Surg 10B:205-210,1985 22. Blair WE Kilpatrick WC, Omer GE: Open fracture of hook of the hamate: A case report. Clin Orthop 163:180-184, 1982 23. Boulas HJ, Milek MA: Hook of the hamate fractures. Diagnosis, treatment and complications. Orthop Rev 19:518~529,1990 24. Eaton RG, Morris J: What's New with Bones--in Littler JW, Cramer LM, Smith JW (eds): Symposium on Reconstructive Hand Surgery, St. Louis, MO, Mosby, 1974, pp 274-278
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