Keywords
non-union - trapezoid - bone graft
Introduction
Trapezoid bone fractures are very rare injuries, accounting for <1% of all carpal
bone fractures.[1] Its appearance as an isolated condition is even rarer, since in 95% of cases, they
are associated with fractures of the metacarpals, phalanges, scaphoid, or tears of
the scapholunate ligament.[2] Its unique bone anatomy and the strength of the intrinsic ligaments that insert
into it contribute to protecting it from trauma, so a very specific mechanism is required
for it to become injured. Distally, it forms a nearly immobile joint with the base
of the second metacarpal and is one of the elements of the distal carpal row, which
gives it enormous stability. The injury mechanism required for a trapezoid fracture
involves the application of an axial load, usually high-energy, to the second radius
of the hand, combined with a dorsal extension moment of the carpal-metacarpal joint.[3]
Due to its low incidence, it is often not diagnosed during the initial examination.
Seventy-five percent of cases go undetected on plain radiographs,[3] so complementary examinations such as computed tomography (CT) or magnetic resonance
imaging (MRI) are very useful for identifying them. However, despite the usual delay
in diagnosing this injury, the development of pseudoarthrosis has been described infrequently.
In this paper, we present a case of trapezoid pseudoarthrosis that, to our knowledge,
has not been previously reported in international medical literature. There is only
one article on delayed consolidation treated 3 months after the injury.[4]
Clinical Case
A 39-year-old male butcher with no significant medical history suffered a motorcycle
accident, sustaining multiple contusions in various locations, one of them on his
right hand, which is his dominant side. Initial radiological examination revealed
no bone injury, so he was referred for physical therapy for his various ailments.
After 6 months, the patient continued to experience pain located near the base of
the second metacarpal on its dorsal side. Repeat plain X-rays in anteroposterior,
oblique, and lateral projections were performed, again with no evidence of bone injury.
Eight months after the accident, and given the lack of improvement in the pain, an
MRI was performed, which revealed bone edema in the trapezoid bone and signs of an
advanced fracture. At this time, the patient was referred to our unit. The patient
presented with pain and swelling on the back of the hand around the carpometacarpal
joint of the second radius, with limited mobility in the last degrees of flexion and
extension of the radiocarpal, midcarpal, and metacarpophalangeal joints. The patient
reported being unable to perform his professional activities due to a compromised
grip with that hand.
The radiological study was completed with a CT scan, which confirmed a pseudoarthrosis
of the trapezoid bone with a fracture line in the coronal plane affecting both the
carpometacarpal and scaphotrapeziotrapezoid joints (STT) ([Fig. 1]).
Fig. 1 A) Axial CT scan showing trapezoid pseudarthrosis. B) Sagittal CT scan showing the
coronal fracture line and fragment displacement.
Surgical treatment was decided upon. Through a dorsal approach centered over the body
of the trapezoid, both the carpometacarpal joint and the STT were accessed. Through
the latter, the focus of the nonunion was located and aggressively treated until bleeding
edges were obtained without sclerotic remnants. A cancellous bone autograft from the
distal radius metaphyseal bone was applied to the focus, and internal fixation was
performed with a 2.0 mm cannulated headless compression screw (BRM Extremities, Milan,
Italy).
The patient was discharged the same day of the procedure with a compression bandage
and instructions for full non-weight-bearing wrist and finger motion. Rehabilitation
began two weeks after surgery.
At 6 months, the patient had full mobility of the wrist and fingers, pain-free, with
full recovery of function and return to work without limitations ([Fig. 2]). The follow-up CT scan confirmed complete consolidation of the pseudoarthrosis
([Fig. 3]). After one year, the patient's outcome showed no deterioration and was discharged.
Fig. 2 Wrist mobility at the end of follow-up.
Fig. 3 A) Postoperative plain radiograph. B) Axial CT scan confirming complete consolidation
of the fragments. C) Sagittal CT scan.
Discussion
Isolated fractures of the trapezoid bone are extremely rare. A recent review on the
subject notes that only 19 articles have been published with a total of 22 cases.[3] Most of these fractures occur after a high-energy traffic accident involving a frontal
fall and direct trauma to the hand. A load transferred axially to the second radius,
or a forced extension of the metacarpophalangeal joint, and subsequently the carpometacarpal
joint, can lead to injury.
75% of cases go unnoticed during the initial examination. This high percentage is
due, first, to its low frequency, which requires a high level of suspicion for diagnosis.
Second, due to the unique anatomy of the trapezoid bone, its small size, and its location
in the middle of the distal carpal row, which makes it difficult to obtain clear radiological
projections that allow for proper assessment. Third, approximately 35% of fractures
present a fracture pattern in the coronal plane,[5] which is why they would only be visible in well-performed lateral projections.
The vascular supply of the trapezoid bone mostly comes from its dorsal aspect. The
main contributions come from the vascular network of the dorsal intercarpal artery
and the basal metacarpal arch.[6] From this network arise 3 or 4 branches that penetrate the trapezoid on its dorsal
face and give rise to various branches in the subchondral bone, without anastomosis
between them, providing vascularization to approximately 70% of the bone in a segmental
manner.[7] This particular vascular anatomy means that the volar region of the bone has a more
precarious blood supply, so coronal fracture lines, such as the one in our case, could
cause an interruption in the vascular supply to the volar region.
Conservative treatment, using immobilization with a forearm splint, has proven to
be very effective.[3]
[5]
[8] Surgical treatment is only considered in cases of fractures displaced more than
2 millimeters or when there are associated injuries.[3]
[5] Osteosynthesis with screws or Kirschner wires are valid alternatives with good functional
results and 100% consolidation rates in the few published cases.[2]
[3]
[5]
Kohara et al.
[4] reports a case of delayed consolidation of a trapezoid fracture. It involves a 25-year-old
patient who suffered a motorcycle accident. The diagnosis was made three months after
the trauma. As in our case, the fracture line runs in the coronal plane. They decided
to perform surgical treatment through osteosynthesis with a screw plus the addition
of autologous cancellous bone graft from the iliac crest. Unlike our approach, they
used a percutaneous technique without exposing the fracture site, applying the cancellous
graft through the hole made with the drill. At six months, the fracture was fully
consolidated. After one year, the patient was asymptomatic, with full mobility and
78% strength compared to the contralateral hand, although he did not return to his
previous work activity before the accident. In our case, we achieved very similar
results in terms of postoperative pain, mobility, and function, as well as in the
fracture consolidation time, despite the much longer evolution time of the pseudarthrosis
(eight months). We preferred an open approach to the lesion to achieve good debridement
of the fracture site and proper placement of the bone graft. It is interesting to
highlight that in both cases the fracture line runs in the coronal plane, which could
have predisposed to the consolidation deficit, as the fracture line may have interrupted
the vascular supply coming from the dorsal region to the volar segment. However, more
case reports on this rare condition are needed to confirm this hypothesis.
