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Fracture of the ulnar sesamoid of the metacarpophalangeal joint of the thumb —An arthrographic study
Fracture of the Ulnar Sesamoid of the Metacarpophalangeal Joint of the Thumb An Arthrographic Study M. J. BELL, R. Y. McMURTRY and J. RUBENSTEIN From the Sunnybrook Medical Centre, Toronto We report a case of fracture of the ulnar sesamoid of the metacarpophalangeal joint of the thumb. The role of arthrography and stress X-rays in delineating the pathological anatomy of this injury is discussed. Volar plate injuries of the metacarpophalangeal joint of the thumb are uncommon. If not diagnosed and treated an unstable, painful, weak thumb may result (Moberg and Stener 1953). The diagnosis is made by history and careful clinical examination. Standard X-ray examination is usually unhelpful. Fracture of the sesamoid bones of the thumb is a rare injury. Crush fractures have been described following direct trauma to the sesamoids (Scobie 1941), but more frequently the sesamoids may fracture as a result of a hyper-extension injury. Stener (1963) reported three cases, in two of which both sesamoids had fractured. The other patient fractured the radial sesamoid alone. This case is reported as the ulnar sesamoid was fractured, and the pathological anatomy of the injury is clearly defined by the use of stress X-rays and arthrography performed under regional anaesthesia, a study which has not previously been documented. Case Report A sixteen-year-old boy was playing American football. Whilst trying to catch the ball he sustained a blow to the tip of the thumb which resulted in a hyper-extension injury to the metacarpophalangeal joint of the left thumb. He presented to the Emergency Department complaining of a painful swollen thumb, at the level of the metacarpophalangeal joint. Examination revealed swelling and bruising around the metacarpophalangeal joint extending to the thenar eminence. All movements of the thumb were painful, but considered to be full. He was tender over the radial and palmar aspects of the joint, and according to the Emergency Physician, stressing the joint in any direction increased his discomfort. Standard antero-posterior and lateral X-rays of the metacarpophalangeal joints of the thumb were taken which revealed a fracture of the ulnar sesamoid and soft tissue swelling around the joint, but no other abnormality (Figure 1). The fractured sesamoid fragments were widely displaced. The patient was placed in an aluminium splint, and referred to the Hand Clinic the following day. Received for publication March, 1985 M. J. Bell, BSc. FRCS, Royal Hallamshire Hospital, Sheffield. R. Y. McMurtry, MD. FRCS(C), FACS, Consultant Orthopaedic Surgeon, Sunnybrook Medical Centre, Toronto. J. Rubenstein, MD, Consultant Radiologist, Sunnybrook Medical Centre, Toronto
VOL. 10-B No. 3 O C T O B E R 1985
Fig. 1
X-rays demonstrating a fracture o f the ulnar sesamoid bone o f the metacarpophalangeal joint of the t h u m b .
At review, the findings of the emergency physician were confirmed, but more careful examination revealed a tender volar plate with marked discomfort on hyperextension of the metacarpophalangeal joint. Stressing the radial collateral ligament caused him increased discomfort. In view of these findings stress X-rays were taken under regional anaesthesia. A median and radial nerve block was performed using 5 mls of one per cent Lignocaine. The stability of the joint was then assessed. No instability of the radial or ulnar collateral ligaments could be demonstrated. Extension of the joint was increased by 20 ~ as compared to the other side. An arthrogram was performed using 0.5 ml of 60 per cent Hypaque to determine the integrity of the joint capsule. The arthrogram showed the extent of the injury by defining the pathological anatomy. All of the contrast medium leaked from the volar aspect of the joint, indicating a large tear of the volar plate; filled the fibrous sheath of the flexor pollicis longus tendon and 379
M. J. BELL, R. Y. McMURTRY AND J. RUBENSTEIN
....~~\~ii i84
~
~ii~!!i 84 :~
g Fig. 2
Arthrogram of metacarpophalangeal joint of the thumb, showing extensive volar leakage of contrast, filling of fibrous sheath of flexor pollicis longus and dye flowing along the belly of adductor pollicis.
tracked down the belly of adductor pollicis (Figure 2). These investigations revealed that the only injuries were to the ulnar sesamoid and the cartilaginous portion of the volar plate. The collateral ligaments of the joint were undamaged. The patient was treated with a removable splint holding the metacarpophalangeal joint in 20 ~ of flexion. This splint was made of a thermo-pliable plastic. The patient was instructed to wear this at all times and was allowed out of the splint two or three times a day for mobilisation exercises of the joint. After a period of four weeks of immobilisation the joint was still tender over the volar plate and hyper-extension caused him some further discomfort. Therefore the thumb was immobilised for an additional four weeks, at which point the thumb was painfree with a full range of motion. He was advised to discard the splint during activities of daily living but to wear the splint whilst performing heavy manual tasks until three months had elapsed following the injury. At review six months after the injury the thumb had a full range of motion and was stable in all directions. There was no hyper-extension of the joint, as compared to the contra-lateral side. Discussion Review of the literature reveals that the first description of sesamoid bone fracture as a result of a hyperextension injury to the thumb was by Pye in 1919. Four further reports appeared before Stener (1963) published his article on Hyper-extension Injuries to the Metacarpophalangeal joint of the Thumb. He described cases of sesamoid bone fracture with simple dislocation of the joint, and two cases without dislocation but with volar plate disruption. He reported in detail on the anatomy of the volar plate following a series of thirty 380
eight post-mortem dissections. He described the volar plate as being composed of three parts: the proximal palmar ligament; the fibrous palmar plate and the distal palmar ligament (Figure 3). Both the ligaments are attached to the fibrous plate and are inserted into the metacarpal and proximal phalanx respectively. The sesamoid bones are embedded in the fibrous plate and receive the insertions of the flexor pollicis brevis tendon on the radial sesamoid and of adductor pollicis on the ulnar bone. The accessory collateral ligaments are attached to the lateral edge of the sesamoid bones. The fibrous palmar plate forms part of the fibrous tunnel of the flexor pollicis longus tendon. The volar plate may rupture at any site but the commonest place for a tear to occur is at the attachment of the proximal palmar ligamentto the fibrous palmar plate, and not from the insertion to the metacarpal. Moberg and Stener (1953) reported that isolated volar plate injuries are uncommon but injury to the volar plate has been shown to occur in combination with injuries to the ulnar collateral ligament of the metacarpophalangeal joint of the thumb (Bell, Hill, McMurty 1985). Stener in his series of cases showed that for dislocation of the metacarpophalangeal joint to occur, the volar plate must be disrupted and the collateral ligaments torn. In the complex dislocations of the joints the volar plate ruptures at the level of the proximal palmar ligament and the whole of the fibrous palmar plate with the sesamoid bones attached, is displaced into the joint, often preventing reduction of the dislocation. Entrapment of the sesamoid bones into the joint may well be the mechanism by which fragmentation of these bones occurs as has been reported with this type of dislocation (Moniem 1983). In the cases with fracture of the sesamoid bone and volar plate rupture, the fractures are noted to be displaced. It was felt that the deforming force was probably the flexor pollicis brevis which caused the separation of the fragments. Stener (1963) showed that on maximum flexion of the metacarpophalangeal joint the fracture did not reduce. Therefore he recommended surgical correction and repair of the volar plate by reducing the fractures of the sesamoid bones and maintaining this reduction with silk sutures. This is contrary to the view of Jellinger (1947) and Wood (1984) who believe that immobilisation results in good function, and surgery is seldom indicated. Our patient was managed conservatively with good result. The cases that Stener described had a much greater degree of volar instability. Associated injury to the accessory and probably the true collateral ligament must have occurred to have produced such gross instability. We were able to prove with stress radiographs and arthrography that there were no THE JOURNAL OF HAND SURGERY
FRACTURE OF THE ULNAR SESAMOID
,
1 ~ 3
4 1
4 3
Fig. 3
The anatomy of the volar plate of the metacarpopbalangeal joint of the thumb after Stener. - - 1. Collateral ligament proper; 2. Accessory collateral ligament; 3. Proximal palmar ligament; 4. Distal palmar ligament; 5. Fibrous palmar plate.
damage to the collateral ligaments in this patient. However this case has demonstrated Stener's premise that a fracture of the sesamoid bones indicates an extensive injury to the-volar plate, and must be adequately treated to prevent long term disability.
This case report is of a rare injury which, if not treated adequately, can lead to morbidity. Arthrography and stress X-rays are useful agents in the management of difficult and complex problems of the metacarpophalangeal joint of the thumb.
The use of stress radiographs and arthrography was invaluable in the management of this difficult case. We were able to demonstrate that the radial and ulnar collateral ligaments were stable by stressing the joint under anaesthesia, and that there was only volar instability. The arthrogram confirmed the volar plate tear, and defined the pathological anatomy precisely. The tear of the volar plate was at the level of the sesamoid bones, and through the fibrous palmar plate allowing the dye to flow freely through the volar aspect of the joint into the tendon sheath of flexor pollicis longus. In addition, the contrast ran down the muscle belly of adductor pollicis. There was no leakage of dye from the ulnar or radial aspect of the joint, indicating an intact capsule and collateral ligaments.
BELL, M. J., HILL, R. J., McMURTRY, R. Y., Acute Injuries to the Metacarpophalangeal Joint of the Thumb - - A Clinical and Radiological Study British Orthopaedic Association 1985. JELLINGER, D. L. (1947) Fracture of a Sesamoid Bone of the Thumb-Report of a Case. American Journal Roentgenology and Radium Therapy. 57: 619-621. MOBERG, E. and STENER, B. (1953) Injuries to the Ligaments of the Thumb and Fingers - - Diagnosis, Treatment and Prognosis, Acta Chirurgica Scandinavica 106: 166-186. MONEIM, M. S. (1983). Volar Dislocation of the Metacarpophalangeal Joint. Pathologic Anatomy and Report of Two Cases. Clinical Orthopaedics and Related Research 176: 186-189. PYE, W. Surgical Handicraft 8th Edition (1919) p.205. SCOBIE, W. H. (1941) Crush Fracture of the Sesamoid Bone of the Thumb British Medical Journal. 2: 912. STENER, B. (1963) Hyperextension Injuries to the Metacara0ophalangeal Joint of the Thumb, Rupture of Ligaments, Fracture of Sesamoid Bones, Rupture of Flexor Pollicis Brevis, An Anatomical and Clinical Study Aeta Chirurgica Scandinavica 125: 275-293. WOOD, V. E. (1984) The Sesamoid Bones of the Hand and their Pathology, The Journal of Hand Surgery 9B: 3: 261-264.
References
VOL. 10-B No. 3 OCTOBER 1985
381
VOL. 10-B No. 3 O C T O B E R 1985
Fig. 1
X-rays demonstrating a fracture o f the ulnar sesamoid bone o f the metacarpophalangeal joint of the t h u m b .
At review, the findings of the emergency physician were confirmed, but more careful examination revealed a tender volar plate with marked discomfort on hyperextension of the metacarpophalangeal joint. Stressing the radial collateral ligament caused him increased discomfort. In view of these findings stress X-rays were taken under regional anaesthesia. A median and radial nerve block was performed using 5 mls of one per cent Lignocaine. The stability of the joint was then assessed. No instability of the radial or ulnar collateral ligaments could be demonstrated. Extension of the joint was increased by 20 ~ as compared to the other side. An arthrogram was performed using 0.5 ml of 60 per cent Hypaque to determine the integrity of the joint capsule. The arthrogram showed the extent of the injury by defining the pathological anatomy. All of the contrast medium leaked from the volar aspect of the joint, indicating a large tear of the volar plate; filled the fibrous sheath of the flexor pollicis longus tendon and 379
M. J. BELL, R. Y. McMURTRY AND J. RUBENSTEIN
....~~\~ii i84
~
~ii~!!i 84 :~
g Fig. 2
Arthrogram of metacarpophalangeal joint of the thumb, showing extensive volar leakage of contrast, filling of fibrous sheath of flexor pollicis longus and dye flowing along the belly of adductor pollicis.
tracked down the belly of adductor pollicis (Figure 2). These investigations revealed that the only injuries were to the ulnar sesamoid and the cartilaginous portion of the volar plate. The collateral ligaments of the joint were undamaged. The patient was treated with a removable splint holding the metacarpophalangeal joint in 20 ~ of flexion. This splint was made of a thermo-pliable plastic. The patient was instructed to wear this at all times and was allowed out of the splint two or three times a day for mobilisation exercises of the joint. After a period of four weeks of immobilisation the joint was still tender over the volar plate and hyper-extension caused him some further discomfort. Therefore the thumb was immobilised for an additional four weeks, at which point the thumb was painfree with a full range of motion. He was advised to discard the splint during activities of daily living but to wear the splint whilst performing heavy manual tasks until three months had elapsed following the injury. At review six months after the injury the thumb had a full range of motion and was stable in all directions. There was no hyper-extension of the joint, as compared to the contra-lateral side. Discussion Review of the literature reveals that the first description of sesamoid bone fracture as a result of a hyperextension injury to the thumb was by Pye in 1919. Four further reports appeared before Stener (1963) published his article on Hyper-extension Injuries to the Metacarpophalangeal joint of the Thumb. He described cases of sesamoid bone fracture with simple dislocation of the joint, and two cases without dislocation but with volar plate disruption. He reported in detail on the anatomy of the volar plate following a series of thirty 380
eight post-mortem dissections. He described the volar plate as being composed of three parts: the proximal palmar ligament; the fibrous palmar plate and the distal palmar ligament (Figure 3). Both the ligaments are attached to the fibrous plate and are inserted into the metacarpal and proximal phalanx respectively. The sesamoid bones are embedded in the fibrous plate and receive the insertions of the flexor pollicis brevis tendon on the radial sesamoid and of adductor pollicis on the ulnar bone. The accessory collateral ligaments are attached to the lateral edge of the sesamoid bones. The fibrous palmar plate forms part of the fibrous tunnel of the flexor pollicis longus tendon. The volar plate may rupture at any site but the commonest place for a tear to occur is at the attachment of the proximal palmar ligamentto the fibrous palmar plate, and not from the insertion to the metacarpal. Moberg and Stener (1953) reported that isolated volar plate injuries are uncommon but injury to the volar plate has been shown to occur in combination with injuries to the ulnar collateral ligament of the metacarpophalangeal joint of the thumb (Bell, Hill, McMurty 1985). Stener in his series of cases showed that for dislocation of the metacarpophalangeal joint to occur, the volar plate must be disrupted and the collateral ligaments torn. In the complex dislocations of the joints the volar plate ruptures at the level of the proximal palmar ligament and the whole of the fibrous palmar plate with the sesamoid bones attached, is displaced into the joint, often preventing reduction of the dislocation. Entrapment of the sesamoid bones into the joint may well be the mechanism by which fragmentation of these bones occurs as has been reported with this type of dislocation (Moniem 1983). In the cases with fracture of the sesamoid bone and volar plate rupture, the fractures are noted to be displaced. It was felt that the deforming force was probably the flexor pollicis brevis which caused the separation of the fragments. Stener (1963) showed that on maximum flexion of the metacarpophalangeal joint the fracture did not reduce. Therefore he recommended surgical correction and repair of the volar plate by reducing the fractures of the sesamoid bones and maintaining this reduction with silk sutures. This is contrary to the view of Jellinger (1947) and Wood (1984) who believe that immobilisation results in good function, and surgery is seldom indicated. Our patient was managed conservatively with good result. The cases that Stener described had a much greater degree of volar instability. Associated injury to the accessory and probably the true collateral ligament must have occurred to have produced such gross instability. We were able to prove with stress radiographs and arthrography that there were no THE JOURNAL OF HAND SURGERY
FRACTURE OF THE ULNAR SESAMOID
,
1 ~ 3
4 1
4 3
Fig. 3
The anatomy of the volar plate of the metacarpopbalangeal joint of the thumb after Stener. - - 1. Collateral ligament proper; 2. Accessory collateral ligament; 3. Proximal palmar ligament; 4. Distal palmar ligament; 5. Fibrous palmar plate.
damage to the collateral ligaments in this patient. However this case has demonstrated Stener's premise that a fracture of the sesamoid bones indicates an extensive injury to the-volar plate, and must be adequately treated to prevent long term disability.
This case report is of a rare injury which, if not treated adequately, can lead to morbidity. Arthrography and stress X-rays are useful agents in the management of difficult and complex problems of the metacarpophalangeal joint of the thumb.
The use of stress radiographs and arthrography was invaluable in the management of this difficult case. We were able to demonstrate that the radial and ulnar collateral ligaments were stable by stressing the joint under anaesthesia, and that there was only volar instability. The arthrogram confirmed the volar plate tear, and defined the pathological anatomy precisely. The tear of the volar plate was at the level of the sesamoid bones, and through the fibrous palmar plate allowing the dye to flow freely through the volar aspect of the joint into the tendon sheath of flexor pollicis longus. In addition, the contrast ran down the muscle belly of adductor pollicis. There was no leakage of dye from the ulnar or radial aspect of the joint, indicating an intact capsule and collateral ligaments.
BELL, M. J., HILL, R. J., McMURTRY, R. Y., Acute Injuries to the Metacarpophalangeal Joint of the Thumb - - A Clinical and Radiological Study British Orthopaedic Association 1985. JELLINGER, D. L. (1947) Fracture of a Sesamoid Bone of the Thumb-Report of a Case. American Journal Roentgenology and Radium Therapy. 57: 619-621. MOBERG, E. and STENER, B. (1953) Injuries to the Ligaments of the Thumb and Fingers - - Diagnosis, Treatment and Prognosis, Acta Chirurgica Scandinavica 106: 166-186. MONEIM, M. S. (1983). Volar Dislocation of the Metacarpophalangeal Joint. Pathologic Anatomy and Report of Two Cases. Clinical Orthopaedics and Related Research 176: 186-189. PYE, W. Surgical Handicraft 8th Edition (1919) p.205. SCOBIE, W. H. (1941) Crush Fracture of the Sesamoid Bone of the Thumb British Medical Journal. 2: 912. STENER, B. (1963) Hyperextension Injuries to the Metacara0ophalangeal Joint of the Thumb, Rupture of Ligaments, Fracture of Sesamoid Bones, Rupture of Flexor Pollicis Brevis, An Anatomical and Clinical Study Aeta Chirurgica Scandinavica 125: 275-293. WOOD, V. E. (1984) The Sesamoid Bones of the Hand and their Pathology, The Journal of Hand Surgery 9B: 3: 261-264.
References
VOL. 10-B No. 3 OCTOBER 1985
381