Keywords
translunate - perilunate - dislocation - fracture
The translunate, perilunate fracture dislocation is a rare injury. In a series of
157 cases of perilunate dislocation there were no translunate fractures reported.[1] There are only case reports in the literature. Johnson classified perilunate fracture
dislocations according to the structures involved.[2] If there is a fracture and only the surrounding ligaments of the lunate are involved;
these are termed lesser arc injuries. If a fracture of the carpal bones occurs, these are termed greater arc injuries. Combinations of greater and lesser arc injuries may occur.
Johnson's classification did not include lunate fractures. Isolated lunate fractures
themselves are rare (0.5%).[3] Bain introduced the translunate arc concept in a case series of three patients.[4] The arc is complementary to the greater and lesser arcs. It includes a path of injury
through the lunate producing a lunate fracture, with associated perilunate injury
(fracture, dislocation, or subluxations). Graham introduced an inferior arc, in which
the path of injury is through the radiocarpal plane.[5]
Purpose
To review a series of translunate perilunate dislocations to analyze the, mechanism
of injury diagnosis, management, and outcome.
Methods
A literature search was performed in pubmed, medline, and google scholar using terms
“translunate,” or “lunate fracture.” Cases were included if they contained a fractured
lunate, with a path of injury along the greater or lesser arc, and/or the radial or
ulna styloids. A total of 285 articles were identified, of which 17 articles included
a translunate injury. The largest series was 3 cases. The senior author also contacted
the members of the International Wrist Investigators Workshop (IWIW). As a result,
cases were received for inclusion.
Results
There were 34 cases reported spanning a period from 1976 to 2011.[4]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20] Eleven were from personal correspondence. They included a spectrum of injury from
minimally displaced fractures to complex fracture dislocations. No cases of acute
carpal tunnel or avascular necrosis were noted. No cases were open. The cases were
divided into a subluxated group and a dislocated group.
Subluxation Group
A total of 10 cases (4 cases from IWIW correspondence and 6 from articles) were reported
with translunate arc injuries that were not dislocated at the time of imaging studies.
These ranged from minimally displaced fractures to subluxations.
The mean age of the patients was 23 years. Injury mechanisms tended to be low energy.
There were 7 falls from a standing height and two patients had punching injuries.
Eight of the lunate fractures were coronal. Six cases had associated scaphoid fractures.
Four had scaphoid and triquetral fractures ([Fig. 1]).
Fig. 1 Frequency of associated fractures in translunate subluxations.
Three patients presented in a delayed fashion and underwent salvage with lunate excision
and scaphocapitate fusion. The lunate fracture was initially missed in these cases.
Six lunates were internally fixed. Four cases utilized screws ([Fig. 2a,b]; [Fig. 3]). One patient with undisplaced fractures had a plaster cast.
Fig. 2a,b Examples of transscaphoid translunate subluxation (a) in coronal plane; (b) in sagittal plane. (Courtesy of Dr Luc De Smet.)
Fig. 3 Internal fixation with screws. (Courtesy of Dr Luc De Smet.)
Seven patients had follow-up. Average follow-up was 12 months, and five patients reported
near normal results.
Dislocation Group
Twenty-four cases (8 cases from IWIW, 16 from the literature) were identified involving
perilunate dislocation.
The mean age was 29 years (range 16–66). The mechanisms of injury mostly involved
high-energy trauma. The most common mechanisms were motor vehicle accidents (10) and
fall from a greater than standing height (9).
Three cases presented in a delayed fashion (8 days, 4 weeks and 6 weeks) to the reporting
surgeon. Two were internally fixed. The 6-week case underwent a proximal row carpectomy.
The lunate fracture pattern was recorded in 19 cases. Fourteen were in the coronal
plane. Multiple other injuries were noted. The most frequent associated fracture was
the radial styloid (15), followed by the scaphoid (11). Thirteen patients had two
or more associated fractures as well as the lunate fracture ([Fig. 4]).
Fig. 4 Diagram of associated fractures in translunate perilunate dislocations.
In four cases the fixation method of the lunate was not stated. Wires were the most
common form of fixation (11). Four cases were treated without internal fixation of
the lunate. An external fixator was used in two cases: in one case as a neutralization
device and in the other as the primary fixation.
Primary salvage was performed in five cases. The techniques used were proximal row
carpectomy (PRC), lunate excision, and a transarticular wire.
Secondary salvage was required in one case with a comminuted coronal fracture of the
lunate, and it involved a total wrist arthrodesis ([Figs. 5a,b]; [Fig. 6a,b]).
Figs. 5a,b Examples of translunate fracture perilunate dislocation (a) in coronal plane; (b) in sagittal plane.
Figs. 6a,b Failed internal fixation with K-wires due to comminution of the lunate (a) in coronal plane; (b) in sagittal plane.
The follow-up of these patients was incomplete, and the outcome data recorded were
variable, limiting our results.
Discussion
Although translunate injury is rare, we identified 34 cases. Surgeons need to be mindful
of this, and expect that they may come across this complex injury in their practicing
lifetime.
Our series included a wide spectrum of injuries that included the translunate arc.
It is possible that some of the undisplaced or subluxated cases were spontaneous reductions.
These had better clinical outcomes, compared with the dislocation group.
Associated fractures were very common. The radial styloid was the most common associated
fracture in the dislocation group. In contrast, Herzberg found that a transscaphoid
injury was the most common (91%) in greater arc perilunate fracture dislocations.[1]
In several cases, the lunate fracture was not identified initially and the presentation
was delayed. This is particularly the case in the subluxation group, where the displacement
was less obvious. To aid in identifying all injuries preoperatively, we use longitudinal
traction radiographs to eliminate carpal bone overlap. The pathological separation
of structures is noted. A separation between carpal bones occurs in purely ligamentous
injuries, and fractures are allowed to gap.[21]
The pathomechanics of the translunate perilunate dislocation is unclear, and our series
contained no information on this. Mayfield suggested that extension, intercarpal supination,
and ulna deviation lead to a perilunate dislocation.[22] It is likely that a variation of this leads to a translunate perilunate injury.
The most common plane of lunate fracture was the coronal plane, similar to a Teisen's
type V fracture.[3] We postulate that this may be due to a longitudinal impaction of the capitate on
the lunate.[23] The capitate shearing against the lunate in the axial plane may cause a coronal
“lip” or “rim” (Teisen type I) fracture of the lunate.[18] This may be accentuated by the tension of the volar radiolunate ligaments. Others
have suggested an avulsion mechanism for the lunate fracture, with the wrist in hyperextension
and the hand being forced into supination against a pronated forearm.[20]
The traditional classification of greater and lesser arc injuries can be expanded.
When grouped together with the translunate and radiocarpal arcs, the four arcs represent
a more inclusive classification of carpal fracture/dislocations ([Figs. 7], [8]). It is based on the level of injury to the lunate or “central column” and guides
diagnosis and treatment.
Fig. 7 Arc injuries, coronal plane. 1: greater arc; 2: lesser arc; 3: translunate arc, 4:
inferior arc.
Fig. 8 Arc injuries, sagittal plane.
A perilunate dislocation, comminuted lunate fracture, and delayed presentation were
more likely to lead to a salvage procedure.
Due to the inconsistent outcome data, we cannot recommend specific treatments.
The senior author previously recommended fixation of the lunate first, often considered
the “keystone” of the proximal row.[2] This is followed by repair of any coincident fractures, followed by ligamentous
repair, in a manner similar to treatment of greater arc injuries.[4] Having now reviewed 34 cases by multiple surgeons, we note that a similar principle
is being utilized of internal fixation of the lunate first, followed by other fracture
fixation then ligament repair. Two cases used external fixation, but these cases are
from older literature.[16] The senior author would recommend their use as a neutralization device.[24]
Our study is a retrospective review and contains only case reports. There is a wide
variability in the data that are reported, leading to an incomplete dataset. Outcomes
were not reported in all cases, and a bias toward positive outcomes is likely. The
spectrum of injuries was variable, and multiple surgical techniques employed. The
cases were collected over a period of more than 30 years, and surgical techniques,
implants, and patient expectations have changed over this time. However, the study
is unique in that it provides a better understanding of the spectrum of a rare and
complex injury.
