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Hamatometacarpal fracture-dislocation: Classification and treatment
The Journal of HAND SURGERY
Sty!. Forssblad, and Lundborg
modifying intracompartmental pressure in human leg. J Bone Joint Surg [Am] 1984;66:1415-20. 8. Folkow B, Gaskell P, Waaler BA. Blood flow through limb muscles during heavy rythmic exercise. Acta Physiol Scand 1970;80:61-72. 9. Styf J, Komer L, Suurkuula M. The muscle relaxation
pressure and muscle blood flow during exercise in chronic compartment syndrome. J Bone Joint Surg [Br] 1987; 69-B. 10. Styf J. Chronic anterior compartment syndrome of the lower leg: An experimental and clinical study. [Thesis]. Goteborg, Sweden: 1986. 174 p.
Hamatometacarpal fracture-dislocation: Classification and treatment Seventeen male patients with a fourth metacarpal fracture and fifth carpometacarpal joint injury were treated. Distinct patterns of injury were recognized and in each case fell into one of three categories. Type IA lesions were characterized by subluxation or dislocation of the fifth carpometacarpal joint without hamate avulsion fracture. Type IB lesions were identical to type IA lesions except for the appearance of a small dorsal rim hamate avulsion fracture. Type II lesions were distinguished by subluxation or dislocation of the fifth carpometacarpal joint and comminution of the dorsal hamate rim. Finally, type III lesions exhibited coronal splitting of the hamate. (J HAND SURG 1987;12A[2 Pt 1]:762-7.)
James E. Cain, Jr., MAJ, MC, USAF, Thomas R. Shepler, COL, MC, USAF, and Michael R. Wilson, MAJ, MC, USAF, Lackland AFR, Texas
Hamatometacarpal injuries encompass a broad yet complex subgroup of injuries to the hand. In most instances the damage occurs as the clenched fist strikes an unyielding object. It is the position at impact of the fourth and fifth metacarpal bases and the degree of metacarpal flexion during load transmission into the hamate that detennine the extent of carpometacarpal (CMC) joint injury. Isolated dislocations and fracturedislocations of the fifth metacarpal base have been reported on extensively. This article addresses a somewhat rarer lesion, hamatometacarpal fracturedislocation.
From the Department of Orthopaedic Surgery, Wilford Hall USAF Medical Center, Lackland AFB, Texas. Received for publication Nov. 10, 1986; accepted in revised form Feb. 27, 1987. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Major James E. Cain, Jr., Department of Orthopaedic Surgery (SGHSB), Lackland AFB, TX 78236.
762
THE JOURNAL OF HAND SURGERY
It has been our experience that lesions that involve fracture-dislocation of the fourth and fifth CMC joint are frequently misdiagnosed at the initial evaluation. The fourth metacarpal fracture is usually appreciated and presumed to be responsible for the observed physical signs and symptoms. Consequently, both the examination and search for an associated injury cease. Anteroposterior and lateral radiographs do not always provide adequate visualization of the hamatometacarpal joints. The 45° pronation oblique image, however, nicely defines injury to both the fourth and fifth CMC joints. Occasionally, the 15° pronation oblique projection is required to assess damage to the dorsal portion of the fifth CMC joint. Anteroposterior tomography is of value in complex fracture-dislocations. Distinct patterns of injury to the fifth CMC joint were observed and in each case fell into one of three categories (Fig. 1). Reduction was generally easy to obtain, but difficult to maintain, with closed methods.
Case reports Seventeen male patients with fracture of the fourth metacarpal, dislocation of the fifth metacarpal base, and
Vol. 12A, No.5, Part 1 September 1987
Hamatometacarpal fracture-dislocation
TYPEIA N-1
Fig. 1. Concomitant fourth metacarpal fracture and fifth CMC joint injury are necessary for inclusion in this classification scheme. In type IA lesions, subluxation or dislocation of the fifth metacarpal base is accompanied by dorsal CMC ligament disruption. No hamate injury is apparent. Type IB lesions demonstrate dorsal hamate fracture. In type II injuries, dorsal hamate comminution is present. Type III lesions exhibit coronal splitting of the hamate. The frequency of injury is represented by the letter "N".
Fig. 2. A, Anteroposterior view. Note the short oblique fracture of the fourth metacarpal base (closed arrow). B, The lateral radiograph reveals dorsal displacement of the fourth (closed arrows) and fifth (outline) metacarpals. C, Demonstrated on the oblique projection is a dorsal hamate rim fracture (closed arrow).
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Cain, Shepler, and Wilson
The Journal of HAND SURGERY
Fig. 3. Although visible on anteroposterior and lateral radiographs it is the 45° pronation oblique view that best demonstrates proximal migration of the fifth metacarpal shaft (open arrow) and comminution of the dorsal hamate (closed arrow).
hamate injury were treated. Of the 12 patients for whom a mechanism of injury could be recalled, nine related common histories in that their injuries occurred as a result of striking a blow with a clenched fist. The fourth metacarpal fracture was recognized in all cases; however, the hamatometacarpal joint injury was seldom appreciated on initial evaluation. Case 1. A 24-year-old left-handed man came to the emergency room 2 days after a fist fight. Physical examination revealed a swollen. painful left hand. Maximum tenderness was elicited by palpation of the dorsal hamatometacarpal joints. Radiographic examination demonstrated fracture of the base of the fourth metacarpal, with dorsal displacement of the distal fragment. Examination of the oblique projection revealed a small (type 18) hamate avulsion fracture and dorsal subluxation of the fifth metacarpal base (Fig. 2). Both injuries were easily reduced with digital pressure; however, displacement recurred immediately upon cessation of the reduction maneuver. At operation the proximal portion of the dorsal CMC ligament was found to be stripped from the surface of the hamate. An osteocartilagenous hamate fragment, much larger than expected based on its radiographic appearance, remained attached to the ligament. The fifth CMC joint was quite unstable, requiring only slight metacarpophalangeal joint flexion to cause dorsal dislocation. The injuries were reduced and stabilized with Kirschner wires. Parallel percutaneous pins were driven from the unstable fifth and fourth metacarpals into the stable third. The osteocartilagenous fragment was reduced and also held in position with Kirschner-wire fixation. Case 2. A 26-year-old right-handed man "tripped" striking his clenched fist against a wall. He was evaluated that same day in our orthopedic clinic and found to have a grossly
swollen right hand. Crepitus was present on palpation of the midportion of the fourth metacarpal. There was exquisite tenderness to palpation of the dorsal portion of the fifth CMC joint. Radiographs of the hand revealed a dorsally angulated mid shaft fracture of the fourth metacarpal. The fifth metacarpal shaft had migrated proximally and was dorsally dislocated at the CMC joint. A rather large comminuted (type II) hamate fracture was present (Fig. 3). The metacarpal fracture and dislocation were easily reduced but recurred when the hand assumed the attitude of a clenched fist. At operation, significant dorsal hamate comminution was noted. The fourth metacarpal fracture was stabilized with an intramedullary device and the fifth metacarpal base located. Parallel pins were then placed into the stable third metacarpal shaft. The hamate fracture fragments were replaced and the dorsal CMC ligament primarily repaired. Case 3. A 21-year-old right-handed man was seen for evaluation of a right hand injury sustained in a fist fight. The diagnosis was a fourth metacarpal fracture. The hand was placed in a splint, and the patient was referred to our clinic for definitive care. Examination revealed significant dorsal swelling and tenderness to palpation of the hamatometacarpal joints. The radiographs showed a fracture of the base of the fourth metacarpal and a central fracture-dislocation of the fifth CMC joint. Tomography showed a small centrally depressed fracture fragment (Fig. 4). At operation, the dorsal CMC ligament was found to be intact. To visualize the fracture site, the proximal portion of the ligament was reflected distally and ulnarly. The fifth metacarpal base was then visualized, located, and pinned. In this manner a buttress was formed upon which the hamate fracture fragments could be molded into congruency. The hamate. once reduced, was secured with Kirschner wires.
Vol. 12A, No.5, Part I September 1987
Hamatometacarpal fracture-dislocation
765
Fig. 4.A, Note the benign appearance of this injury on both anteroposterior and lateral radiographs. B, On close examination of the lateral projection one can appreciate dorsal displacement of both the fifth metacarpal (closed arrow) and dorsal hamate (open arrow). C, Tomography nicely defines the configuration of the fourth metacarpal fracture (outline) and reveals a centrally depressed hamate fracture fragment (center open arrow) . a potential block to anatomic reduction.
Discussion Injuries to the fourth and fifth carpometacarpal joints are uncommon. Scattered reports of trauma to this region exist, but the paucity of literature would reflect either infrequency of injury or more likely, a lack of reporting. Isolated dislocation of the fifth metacarpal base was first described in 1918 by McWhorter. 4 Since his original description, several more cases have been recorded in the literature. 5· 7 Fracture-dislocation occurring at the fifth metacarpal base is apparently a more common injury. This was first described in 1945 by Clement,8 who commented
on the instability of the injury and the necessity for percutaneous pin fixation. Several other examples appear in the literature, the largest series being reported by Bora and Didizian. 2 Marck and Klaser9 in 1986 presented a case report of a similar injury. Open reduction was advised to achieve reduction of the hamate fracture fragment and to inspect the fracture site for interposition of the dorsal CMC ligament. The hamatometacarpal articulations are modified saddle joints. As such, they allow considerable motion in the anterior-posterior plane. A 15 0 arc of motion exists at the fourth CMC joint while a 300 arc exists at
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Fig. 5. Axial loading of the fourth metacarpal shaft (top) results in fourth metacarpal fracture and shortening (middle). Load transference t.o the fifth metacarpal causes fifth CMC joint injury.
the fifth CMC joint. It is this mobility that predisposes the joint to dislocation. Motion beyond these limits is prevented by several soft tissue structures. The transverse metacarpal ligament via its attachment to the immobile third metacarpal restrains motion in the anteroposterior plane and prevents significant abduction of the fourth and fifth metacarpal rays. The dorsal carpometacarpal ligament likewise provides restraint at the limits of palmarflexion. The interosseous ligaments tether the proximal portions of the metacarpals to one another and thus are important stabilizers of the hamatometacarpal joint. 1 Finally, the saddle joint by virtue of its concavoconvexity resists dislocation. The mechanism of this injury in most cases involves transmission of an axial load (Fig. 5) .1.3 Initially, load transmission is conducted by the fourth metacarpal into the carpus. At some point, the forces generated by
The Journal of HAND SURGERY
impact outpace the abilities of the fourth metacarpal shaft and fourth CMC joint to dissipate them; hence, fracture occurs. With fracture comes shortening and with shortening comes load transference to the fifth metacarpal shaft. It is likely that the degree of fifth metacarpal palmarflexion is the determinate of the type and degree of hamate injury. Flexion during impact results in dorsal dislocation of the fifth metacarpal base, dorsal CMC ligament disruption, and oftentimes, a hamate dorsal rim fracture. Axial loading through minimally flexed fourth and fifth metacarpal rays results in a type III hamate injury. Treatment options in this series were based on the classification of the fifth CMC joint injury. Type I lesions were reduced then tested for stability. Those type IA and IB lesions that were found to be stable were treated with a 4-week period of cast immobilization. In those unstable type IA lesions, we elected to percutaneously pin the reduced fifth metacarpal base to the hamate with a smooth transarticular Kirschner wire. Pins may also be driven from the fifth and fourth metacarpal shafts into the stable third metacarpal should the fourth metacarpal fracture show a tendency to displace dorsally. Care must be taken, however, to preserve the transverse metacarpal arch should the surgeon opt for this form of fixation . Generally the type IB lesion was unstable and difficult to treat in a closed fashion. Radiographs were oftentimes misleading in that the size of the osteocartilagenous hamate fracture fragment was underestimated. For this reason, we chose open reduction of unstable type IB lesions, with anatomic restoration of bony and soft tissues. Internal fixation of this lesion was as for type IA lesions. Occasionally, however, the osteocartilagenous fragment was large enough to allow it to be pinned back to the hamate. Type II injuries were grossly unstable usually requiring only minimal flexion of the fifth metacarpal ray to dislocate the metacarpal base. Open reduction was done, the goal being the reconstitution of the dorsal hamate buttress and dorsal CMC ligament. The injury, once reduced, was held with percutaneous pins placed through the fifth, fourth, and into the third metacarpal shaft. If the stability of the fifth CMC joint was questioned, it was pinned using a smooth transarticular Kirschner wire. The type III fracture-dislocation is the injury most likely to be missed. The findings on anteroposterior and lateral radiographs are subtle. The injury however is quite dramatic and requires open reduction and internal fixation to develop a congruent joint surface.
Vol. 12A, No.5, Part 1 September 1987
Hamatometacarpal fracture-dislocation
Conclusion The injury described in this article is among the most severe in a continuum of fourth and fifth carpometacarpal joint injuries. The radiographic findings are often subtle, and frequently the true extent of the lesion is not appreciated. It is mandatory that a 45° pronation oblique film be obtained and occasionally necessary to acquire a 15° pronation oblique to fully assess this injury. Failure to satisfactorily locate the fifth metacarpal base alters the mechanics of the hand and weakens power grip.2. 10 Since significant motion exists at both the fourth and fifth carpometacarpal joints, failure to restore a congruent joint surface may result in a degenerative arthrosis and pain. REFERENCES 1. Lilling M, Weinberg H. The mechanics of dorsal fracture dislocation of the fifth carpometacarpal joint. J HAND SURG 1979;4:340-2. 2. Bora FW, Didizian NH. The treatment of injuries to the
3. 4.
5. 6. 7. 8. 9.
10.
carpometacarpal joint of the little finger. J Bone Joint Surg [Am] 1974;56:1459-63. Waugh RL, Yancey AG. Carpometacarpal dislocations. J Bone Joint Surg [Am] 1948;30:397-404. McWhorter GL. Isolated and complete dislocation of the fifth carpometacarpal joint: Open operation. Surg Clin Chicago 1918;2:793-6. Buzby BF. Palmar carpometacarpal dislocation of the fifth metacarpal. Br J Surg 1934; 100:555-7. Roberts N, Holland CT. Isolated dislocation of the base of the fifth metacarpal. Br J Surg 1936;23:567-71. Ker HR. Dislocation of the fifth carpometacarpal joint. J Bone Joint Surg [Br] 1955;37:254-6. Clement BL. Fracture dislocation of the base of the fifth metacarpal. J Bone Joint Surg [Am] 1945;27:498-9. Marck KW, Klasen HJ. Fracture-dislocation of the hamatometacarpal joint: A case report. J HAND SURG 1986;IIA:128-30. Imbriglia JE. Chronic dorsal carpometacarpal dislocation of the index, middle, ring, and little fingers: A case report. J HAND SURG 1979;4:343-5.
The effect of scapholunate ligament section on scapholunate motion Although the scapholunate interosseous ligament has been studied anatomically and functionally by several investigators, its exact role in wrist kinematics is still controversial. We designed and executed an experimental study with four cadaver specimens to compare various carpal motions before and after section of this ligament. Our results suggest that injury to this structure significantly changes carpal motion especially between the scaphoid and lunate. (J HAND SURG 1987;12A[2 Pt 1]:767-71.)
L. K. Ruby, M.D., K. N. An, Ph.D., R. L. Linscheid, M.D., W. P. Cooney III, M.D., and E. Y. S. Chao, Ph.D., Boston, Mass., and Rochester, Minn.
From the Department of Orthopedic Surgery, Tufts University School of Medicine, Boston, Mass., and the Orthopedic Biomechanics Laboratory, Mayo Clinic/Mayo Foundation, Rochester, Minn. Received for publication Sept. 29, 1986; accepted in revised form Dec. 8, 1986. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Leonard K. Ruby, M.D., Tufts-New England Medical Center, 750 Washington St., Boston, MA 02111-1854.
In the last decade, there has been heightened interest in the wrist among clinicians. Several controversial areas have become apparent. One of these areas concerns the function of the scapholunate interosseous ligament. Several authors 1·3 have assigned a major role to this structure in the prevention of scapholunate disassociation and carpal collapse. Others4 • 5 have demonstrated little change in the scapholunate relationship or relative motion when this ligament is disrupted.
THE JOURNAL OF HAND SURGERY
767
Sty!. Forssblad, and Lundborg
modifying intracompartmental pressure in human leg. J Bone Joint Surg [Am] 1984;66:1415-20. 8. Folkow B, Gaskell P, Waaler BA. Blood flow through limb muscles during heavy rythmic exercise. Acta Physiol Scand 1970;80:61-72. 9. Styf J, Komer L, Suurkuula M. The muscle relaxation
pressure and muscle blood flow during exercise in chronic compartment syndrome. J Bone Joint Surg [Br] 1987; 69-B. 10. Styf J. Chronic anterior compartment syndrome of the lower leg: An experimental and clinical study. [Thesis]. Goteborg, Sweden: 1986. 174 p.
Hamatometacarpal fracture-dislocation: Classification and treatment Seventeen male patients with a fourth metacarpal fracture and fifth carpometacarpal joint injury were treated. Distinct patterns of injury were recognized and in each case fell into one of three categories. Type IA lesions were characterized by subluxation or dislocation of the fifth carpometacarpal joint without hamate avulsion fracture. Type IB lesions were identical to type IA lesions except for the appearance of a small dorsal rim hamate avulsion fracture. Type II lesions were distinguished by subluxation or dislocation of the fifth carpometacarpal joint and comminution of the dorsal hamate rim. Finally, type III lesions exhibited coronal splitting of the hamate. (J HAND SURG 1987;12A[2 Pt 1]:762-7.)
James E. Cain, Jr., MAJ, MC, USAF, Thomas R. Shepler, COL, MC, USAF, and Michael R. Wilson, MAJ, MC, USAF, Lackland AFR, Texas
Hamatometacarpal injuries encompass a broad yet complex subgroup of injuries to the hand. In most instances the damage occurs as the clenched fist strikes an unyielding object. It is the position at impact of the fourth and fifth metacarpal bases and the degree of metacarpal flexion during load transmission into the hamate that detennine the extent of carpometacarpal (CMC) joint injury. Isolated dislocations and fracturedislocations of the fifth metacarpal base have been reported on extensively. This article addresses a somewhat rarer lesion, hamatometacarpal fracturedislocation.
From the Department of Orthopaedic Surgery, Wilford Hall USAF Medical Center, Lackland AFB, Texas. Received for publication Nov. 10, 1986; accepted in revised form Feb. 27, 1987. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Major James E. Cain, Jr., Department of Orthopaedic Surgery (SGHSB), Lackland AFB, TX 78236.
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THE JOURNAL OF HAND SURGERY
It has been our experience that lesions that involve fracture-dislocation of the fourth and fifth CMC joint are frequently misdiagnosed at the initial evaluation. The fourth metacarpal fracture is usually appreciated and presumed to be responsible for the observed physical signs and symptoms. Consequently, both the examination and search for an associated injury cease. Anteroposterior and lateral radiographs do not always provide adequate visualization of the hamatometacarpal joints. The 45° pronation oblique image, however, nicely defines injury to both the fourth and fifth CMC joints. Occasionally, the 15° pronation oblique projection is required to assess damage to the dorsal portion of the fifth CMC joint. Anteroposterior tomography is of value in complex fracture-dislocations. Distinct patterns of injury to the fifth CMC joint were observed and in each case fell into one of three categories (Fig. 1). Reduction was generally easy to obtain, but difficult to maintain, with closed methods.
Case reports Seventeen male patients with fracture of the fourth metacarpal, dislocation of the fifth metacarpal base, and
Vol. 12A, No.5, Part 1 September 1987
Hamatometacarpal fracture-dislocation
TYPEIA N-1
Fig. 1. Concomitant fourth metacarpal fracture and fifth CMC joint injury are necessary for inclusion in this classification scheme. In type IA lesions, subluxation or dislocation of the fifth metacarpal base is accompanied by dorsal CMC ligament disruption. No hamate injury is apparent. Type IB lesions demonstrate dorsal hamate fracture. In type II injuries, dorsal hamate comminution is present. Type III lesions exhibit coronal splitting of the hamate. The frequency of injury is represented by the letter "N".
Fig. 2. A, Anteroposterior view. Note the short oblique fracture of the fourth metacarpal base (closed arrow). B, The lateral radiograph reveals dorsal displacement of the fourth (closed arrows) and fifth (outline) metacarpals. C, Demonstrated on the oblique projection is a dorsal hamate rim fracture (closed arrow).
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Cain, Shepler, and Wilson
The Journal of HAND SURGERY
Fig. 3. Although visible on anteroposterior and lateral radiographs it is the 45° pronation oblique view that best demonstrates proximal migration of the fifth metacarpal shaft (open arrow) and comminution of the dorsal hamate (closed arrow).
hamate injury were treated. Of the 12 patients for whom a mechanism of injury could be recalled, nine related common histories in that their injuries occurred as a result of striking a blow with a clenched fist. The fourth metacarpal fracture was recognized in all cases; however, the hamatometacarpal joint injury was seldom appreciated on initial evaluation. Case 1. A 24-year-old left-handed man came to the emergency room 2 days after a fist fight. Physical examination revealed a swollen. painful left hand. Maximum tenderness was elicited by palpation of the dorsal hamatometacarpal joints. Radiographic examination demonstrated fracture of the base of the fourth metacarpal, with dorsal displacement of the distal fragment. Examination of the oblique projection revealed a small (type 18) hamate avulsion fracture and dorsal subluxation of the fifth metacarpal base (Fig. 2). Both injuries were easily reduced with digital pressure; however, displacement recurred immediately upon cessation of the reduction maneuver. At operation the proximal portion of the dorsal CMC ligament was found to be stripped from the surface of the hamate. An osteocartilagenous hamate fragment, much larger than expected based on its radiographic appearance, remained attached to the ligament. The fifth CMC joint was quite unstable, requiring only slight metacarpophalangeal joint flexion to cause dorsal dislocation. The injuries were reduced and stabilized with Kirschner wires. Parallel percutaneous pins were driven from the unstable fifth and fourth metacarpals into the stable third. The osteocartilagenous fragment was reduced and also held in position with Kirschner-wire fixation. Case 2. A 26-year-old right-handed man "tripped" striking his clenched fist against a wall. He was evaluated that same day in our orthopedic clinic and found to have a grossly
swollen right hand. Crepitus was present on palpation of the midportion of the fourth metacarpal. There was exquisite tenderness to palpation of the dorsal portion of the fifth CMC joint. Radiographs of the hand revealed a dorsally angulated mid shaft fracture of the fourth metacarpal. The fifth metacarpal shaft had migrated proximally and was dorsally dislocated at the CMC joint. A rather large comminuted (type II) hamate fracture was present (Fig. 3). The metacarpal fracture and dislocation were easily reduced but recurred when the hand assumed the attitude of a clenched fist. At operation, significant dorsal hamate comminution was noted. The fourth metacarpal fracture was stabilized with an intramedullary device and the fifth metacarpal base located. Parallel pins were then placed into the stable third metacarpal shaft. The hamate fracture fragments were replaced and the dorsal CMC ligament primarily repaired. Case 3. A 21-year-old right-handed man was seen for evaluation of a right hand injury sustained in a fist fight. The diagnosis was a fourth metacarpal fracture. The hand was placed in a splint, and the patient was referred to our clinic for definitive care. Examination revealed significant dorsal swelling and tenderness to palpation of the hamatometacarpal joints. The radiographs showed a fracture of the base of the fourth metacarpal and a central fracture-dislocation of the fifth CMC joint. Tomography showed a small centrally depressed fracture fragment (Fig. 4). At operation, the dorsal CMC ligament was found to be intact. To visualize the fracture site, the proximal portion of the ligament was reflected distally and ulnarly. The fifth metacarpal base was then visualized, located, and pinned. In this manner a buttress was formed upon which the hamate fracture fragments could be molded into congruency. The hamate. once reduced, was secured with Kirschner wires.
Vol. 12A, No.5, Part I September 1987
Hamatometacarpal fracture-dislocation
765
Fig. 4.A, Note the benign appearance of this injury on both anteroposterior and lateral radiographs. B, On close examination of the lateral projection one can appreciate dorsal displacement of both the fifth metacarpal (closed arrow) and dorsal hamate (open arrow). C, Tomography nicely defines the configuration of the fourth metacarpal fracture (outline) and reveals a centrally depressed hamate fracture fragment (center open arrow) . a potential block to anatomic reduction.
Discussion Injuries to the fourth and fifth carpometacarpal joints are uncommon. Scattered reports of trauma to this region exist, but the paucity of literature would reflect either infrequency of injury or more likely, a lack of reporting. Isolated dislocation of the fifth metacarpal base was first described in 1918 by McWhorter. 4 Since his original description, several more cases have been recorded in the literature. 5· 7 Fracture-dislocation occurring at the fifth metacarpal base is apparently a more common injury. This was first described in 1945 by Clement,8 who commented
on the instability of the injury and the necessity for percutaneous pin fixation. Several other examples appear in the literature, the largest series being reported by Bora and Didizian. 2 Marck and Klaser9 in 1986 presented a case report of a similar injury. Open reduction was advised to achieve reduction of the hamate fracture fragment and to inspect the fracture site for interposition of the dorsal CMC ligament. The hamatometacarpal articulations are modified saddle joints. As such, they allow considerable motion in the anterior-posterior plane. A 15 0 arc of motion exists at the fourth CMC joint while a 300 arc exists at
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Fig. 5. Axial loading of the fourth metacarpal shaft (top) results in fourth metacarpal fracture and shortening (middle). Load transference t.o the fifth metacarpal causes fifth CMC joint injury.
the fifth CMC joint. It is this mobility that predisposes the joint to dislocation. Motion beyond these limits is prevented by several soft tissue structures. The transverse metacarpal ligament via its attachment to the immobile third metacarpal restrains motion in the anteroposterior plane and prevents significant abduction of the fourth and fifth metacarpal rays. The dorsal carpometacarpal ligament likewise provides restraint at the limits of palmarflexion. The interosseous ligaments tether the proximal portions of the metacarpals to one another and thus are important stabilizers of the hamatometacarpal joint. 1 Finally, the saddle joint by virtue of its concavoconvexity resists dislocation. The mechanism of this injury in most cases involves transmission of an axial load (Fig. 5) .1.3 Initially, load transmission is conducted by the fourth metacarpal into the carpus. At some point, the forces generated by
The Journal of HAND SURGERY
impact outpace the abilities of the fourth metacarpal shaft and fourth CMC joint to dissipate them; hence, fracture occurs. With fracture comes shortening and with shortening comes load transference to the fifth metacarpal shaft. It is likely that the degree of fifth metacarpal palmarflexion is the determinate of the type and degree of hamate injury. Flexion during impact results in dorsal dislocation of the fifth metacarpal base, dorsal CMC ligament disruption, and oftentimes, a hamate dorsal rim fracture. Axial loading through minimally flexed fourth and fifth metacarpal rays results in a type III hamate injury. Treatment options in this series were based on the classification of the fifth CMC joint injury. Type I lesions were reduced then tested for stability. Those type IA and IB lesions that were found to be stable were treated with a 4-week period of cast immobilization. In those unstable type IA lesions, we elected to percutaneously pin the reduced fifth metacarpal base to the hamate with a smooth transarticular Kirschner wire. Pins may also be driven from the fifth and fourth metacarpal shafts into the stable third metacarpal should the fourth metacarpal fracture show a tendency to displace dorsally. Care must be taken, however, to preserve the transverse metacarpal arch should the surgeon opt for this form of fixation . Generally the type IB lesion was unstable and difficult to treat in a closed fashion. Radiographs were oftentimes misleading in that the size of the osteocartilagenous hamate fracture fragment was underestimated. For this reason, we chose open reduction of unstable type IB lesions, with anatomic restoration of bony and soft tissues. Internal fixation of this lesion was as for type IA lesions. Occasionally, however, the osteocartilagenous fragment was large enough to allow it to be pinned back to the hamate. Type II injuries were grossly unstable usually requiring only minimal flexion of the fifth metacarpal ray to dislocate the metacarpal base. Open reduction was done, the goal being the reconstitution of the dorsal hamate buttress and dorsal CMC ligament. The injury, once reduced, was held with percutaneous pins placed through the fifth, fourth, and into the third metacarpal shaft. If the stability of the fifth CMC joint was questioned, it was pinned using a smooth transarticular Kirschner wire. The type III fracture-dislocation is the injury most likely to be missed. The findings on anteroposterior and lateral radiographs are subtle. The injury however is quite dramatic and requires open reduction and internal fixation to develop a congruent joint surface.
Vol. 12A, No.5, Part 1 September 1987
Hamatometacarpal fracture-dislocation
Conclusion The injury described in this article is among the most severe in a continuum of fourth and fifth carpometacarpal joint injuries. The radiographic findings are often subtle, and frequently the true extent of the lesion is not appreciated. It is mandatory that a 45° pronation oblique film be obtained and occasionally necessary to acquire a 15° pronation oblique to fully assess this injury. Failure to satisfactorily locate the fifth metacarpal base alters the mechanics of the hand and weakens power grip.2. 10 Since significant motion exists at both the fourth and fifth carpometacarpal joints, failure to restore a congruent joint surface may result in a degenerative arthrosis and pain. REFERENCES 1. Lilling M, Weinberg H. The mechanics of dorsal fracture dislocation of the fifth carpometacarpal joint. J HAND SURG 1979;4:340-2. 2. Bora FW, Didizian NH. The treatment of injuries to the
3. 4.
5. 6. 7. 8. 9.
10.
carpometacarpal joint of the little finger. J Bone Joint Surg [Am] 1974;56:1459-63. Waugh RL, Yancey AG. Carpometacarpal dislocations. J Bone Joint Surg [Am] 1948;30:397-404. McWhorter GL. Isolated and complete dislocation of the fifth carpometacarpal joint: Open operation. Surg Clin Chicago 1918;2:793-6. Buzby BF. Palmar carpometacarpal dislocation of the fifth metacarpal. Br J Surg 1934; 100:555-7. Roberts N, Holland CT. Isolated dislocation of the base of the fifth metacarpal. Br J Surg 1936;23:567-71. Ker HR. Dislocation of the fifth carpometacarpal joint. J Bone Joint Surg [Br] 1955;37:254-6. Clement BL. Fracture dislocation of the base of the fifth metacarpal. J Bone Joint Surg [Am] 1945;27:498-9. Marck KW, Klasen HJ. Fracture-dislocation of the hamatometacarpal joint: A case report. J HAND SURG 1986;IIA:128-30. Imbriglia JE. Chronic dorsal carpometacarpal dislocation of the index, middle, ring, and little fingers: A case report. J HAND SURG 1979;4:343-5.
The effect of scapholunate ligament section on scapholunate motion Although the scapholunate interosseous ligament has been studied anatomically and functionally by several investigators, its exact role in wrist kinematics is still controversial. We designed and executed an experimental study with four cadaver specimens to compare various carpal motions before and after section of this ligament. Our results suggest that injury to this structure significantly changes carpal motion especially between the scaphoid and lunate. (J HAND SURG 1987;12A[2 Pt 1]:767-71.)
L. K. Ruby, M.D., K. N. An, Ph.D., R. L. Linscheid, M.D., W. P. Cooney III, M.D., and E. Y. S. Chao, Ph.D., Boston, Mass., and Rochester, Minn.
From the Department of Orthopedic Surgery, Tufts University School of Medicine, Boston, Mass., and the Orthopedic Biomechanics Laboratory, Mayo Clinic/Mayo Foundation, Rochester, Minn. Received for publication Sept. 29, 1986; accepted in revised form Dec. 8, 1986. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Leonard K. Ruby, M.D., Tufts-New England Medical Center, 750 Washington St., Boston, MA 02111-1854.
In the last decade, there has been heightened interest in the wrist among clinicians. Several controversial areas have become apparent. One of these areas concerns the function of the scapholunate interosseous ligament. Several authors 1·3 have assigned a major role to this structure in the prevention of scapholunate disassociation and carpal collapse. Others4 • 5 have demonstrated little change in the scapholunate relationship or relative motion when this ligament is disrupted.
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