Keywords
Kienbock's disease - capitate shortening - joint leveling - capitate vascularity -
capitate osteotomy
Just as the etiology of Kienbock's disease has remained controversial, so has the
optimal treatment. Müller and Kienbock described the disease as one of overactivity
from workplace activities, leading to “occupational lunatolmalacia.”[1]
[2] The etiology is thought to be multifactorial, with both biological and mechanical
triggers.[3]
[4] Although the natural history is unclear, lunate compromise and fragmentation is
known to cause central column collapse and proximal row instability. The late sequelais
degeneration of the articular surfaces of the joint.[5]
There are three classification systems that define the osseous, chondral, and vascular
components of the disease, which were described by Lichtman, Bain, and Schmitt, respectively.[5]
[6]
[7]
[8]
[9] Lichtman and Bain developed a classification system and algorithm that incorporates
all these factors when assessing and planning surgical management. The aim of surgical
treatment is to bypass or excise “nonfunctional articular surfaces,” thereby reducing
pain and maintaining functional wrist movement.[6]
[10]
The concept of an unloading procedure is a well-recognized surgical treatment.[10] This procedure unloads the radiolunate articulation and also provides indirect revascularization
due to regional hyperemia.[11] Several techniques have been described for capitate-shortening osteotomy. Some of
these techniques are technically challenging, risk violating the blood supply to the
capitate, and not easily reproducible. We will review the osseous and vascular anatomy
associated with capitate shortening with the aim to optimize the accuracy, safety,
and reproducibility of the technique.
Anatomy
Osseous
The capitate is the largest of the carpal bones. It articulates proximally with the
lunate and scaphoid and distally with the base of the third metacarpal and, variably,
fourth metacarpal.
The capitate has three parts; the head, neck, and body.[12] The head is the proximal articular aspect that has no ligamentous attachments.[12]
[13] Distal to the head is a narrow neck covered in the periosteum. The body is distal
to the neck. The dorsal and volar aspects of the body have ligamentous attachments.[12]
[14]
[15]
[16] The volar aspect may have part of the adductor pollicis muscle insertion.[14] The hamate articulates with a flat but elongated facet on the ulnar aspect of the
capitate.[14] The articular surfaces of these two joints are interrupted by the attachment sites
for the deep trapezoid–capitate and capitate–hamate (CH) ligaments.[12]
The proximal capitate articulation has been classified into three types: flat, spherical,
and V-shaped. The flat capitate is associated with a single distal lunate facet type
I lunate. The spherical type was associated with a concave articulation formed by
the scaphoid and lunate articulations, with an indistinct border between the scaphoid
and lunate facets.
The “V”-shaped capitate is associated with the presence of a type II lunate, with
a large hamate facet, hamate ridge, capitate ridge, and a fourth carpometacarpal facet
on the distal capitate).[17] It is known that Kienbock's disease is more common if there is a type I lunate,
which may be associated with a flatter proximal capitate articular surface. Capitate
shortening is designed to unload the compromised lunate.[18]
[19]
[20]
Vascular Supply
The vascularity of the lunate is known to be important in Kienbock's disease. We expect
the vascularity of capitate to be important for the risk of postoperative nonunion
and/or avascular necrosis (AVN). Most research has been directed to the arterial supply.[21] Crock did some pioneering work on the venous drainage of the lunate.[22] We have been able to apply this to the etiological concepts of Kienbock's disease.[23]
[24]
Arterial
An anatomical study by Vander Grend et al[21] reported that the palmar blood supply was predominant. The palmar carpal branch
provides vessels at the palmar ulnar border of the capitate neck. In addition, another
large consistent branch from the deep palmar arch enters the palmar aspect of the
distal capitate. Dorsally, the branches enter the capitate at the midwaist portion.
There are no external vessels that enter the capitate head. Vander Grendet al reported
that the capitate intraosseous blood supply has three types. In type 1, the arterial
supply was exclusively from the palmar vessels. In type 2, both the palmar and dorsal
arteries supplied the waist and distal capitate, but the head was predominantly supplied
by the palmar vessels. In type 3, the proximal pole is equally supplied by the palmar
and dorsal vessels.
The intraosseous arterial blood supply assessed by Kadar et al[25] using micro-CT reported the large arterial supply entering the capitate from the
radial aspect of the neck.
Venous
Crock studied the arterial and venous systems and identified a subarticular venous
plexus and a large single venous channel draining at the articular margin into a large
single vascular channel ([Fig. 1]).[22] Crock stated that a compromise to this venous plexus, through biological or mechanical
factors, leading to venous stasis or venous hypertension, may play a part in the pathogenesis
of AVN.[22] We consider that it is also important to avoid compromise of this large vein during
osteotomy for Kienbock's disease.
Fig. 1 Capitate vascularity. (A) The venous anatomy of the capitate. Note the single large vein draining the proximal
capitate (white arrow). (B) The intraosseous arterial supply. (Reproduced with permission of Crock[22].)
Biomechanics of Capitate Shortening
Biomechanics of Capitate Shortening
Werber et al[26] described that a capitate shortening of 1.8 to 2 mm decreased the radiolunate pressure
by 49to 56% and that the load was redistributed to the radial and ulnar columns.[27]
[28] Viola et al[29] reported a 25% decrease after 2.9-mm capitate shortening. Horii et al reported that
a 4-mm capitate shortening with CH fusion decreased the radiolunate pressure by 66%.[30]
Fixation Options
Various authors have described different techniques to stabilize the osteotomy, including
plates, Kirschner (K) wires, staples, and screws ([Fig. 2]).[31]
[32]
[33]
[34]
Fig. 2 Different methods of fixation for capitate-shortening osteotomy.
Capitate Shortening
Almquist[19] recommended capitate shortening for Kienbock's disease in ulnar positive wrists.
Various techniques have been reported and are presented in [Table 1]. A summary of these results is that there have been 89 cases reported in the literature.
The ranges of motion are similar to the preoperative values. However, the mean grip
strength improved from 47 to 58% to 63 to 80% of the contralateral wrist. The mean
visual analog scale score improved from a score of 6.0 to 8.2 to a score of 1.7 to
3.3. All cases united in 6 to 8 weeks. There was one case with irritation from the
K-wire. The concepts of partial capitate osteotomy and CH fusion were not obviously
superior to a capitate osteotomy. However, patients with a lower Lichtman grade did
have better outcomes.[32]
[33]
[34]
[35]
Table 1
Types of capitate osteotomy
|
Author
|
Procedure
|
|
Waitayawinyu et al[33]
|
Capitate shortening with VBG to the lunate
|
|
Moritomoet al[18]
|
Capitate shortening in a reverse L shape
|
|
Citlak et al[31]
|
|
Singer et al[32]
|
|
Almquist[19]
|
Capitate shortening
|
|
Gay et al[34]
|
|
Viola et al[29]
|
Capitate shortening with capitohamate fusion
|
|
Graner et al[35]
|
Lunate excision, capitate osteotomy with interposition bone graft.
|
Abbreviation: VBG, vascularized bone grafting.
Single-Cut Single-Screw Capitate-Shortening Osteotomy
Single-Cut Single-Screw Capitate-Shortening Osteotomy
Based on the aforementioned anatomical and biomechanical factors, we propose a simplified
technique of capitate osteotomy. We performed single-cut capitate osteotomy in three
cases.
Indication for Capitate Shortening
The ideal scenario for capitate shortening is a patient who has a lunate that is intact
(Lichtman and Bain grade B1) that should be protected. The wrist should have a neutral
or positive ulnar variance.
Rationale for Single-Cut Osteotomy
The publication by Werber et al[26] has clearly demonstrated that the capitate shortening is very effective in reducing
the radiolunate load. Shortening of 2mm, however, can result in a capitate that is
not in contact with the lunate. The effect of this is to increase the load on the
scaphotrapeziotrapezoid (STT) and triquetrohamate articulations. We believe that a
2-mm shortening is a lot for the midcarpal joint and likely to lead to a change in
the mechanics more than is required. We believe that an osteotomy the width of the
saw blade (∼1 mm) is adequate to unload the joint and reduce the excessive loading
on the ulnar and radial columns.
Rationale for the Site of Osteotomy
Review of the capitate arterial[21]
[36] and venous[22] supply demonstrates that the proximal capitate head has a retrograde vascular supply,
including vessels within the volar capsule. Placement of the osteotomy at the STT
joint line position will preserve the volar capsular vessels.
Rationale for Retrograde Fixation
Antegrade fixation of the capitate involves hyperflexing the wrist and introducing
the screw through the articular surface. Hyperflexion of the wrist places undue pressure
on the fragile lunate and could cause it to fragment. The retrograde method can be
performed without flexing or violating the joint.
Rationale for Single Screw
When performing a capitate osteotomy, there is a concern about the risk of nonunion
or AVN. However, there have been no nonunions or AVN in almost 100 cases of capitate
shortening published in the world literature. Therefore, if we preserve the soft tissue
envelope, we expect that the osteotomy will heal with the stability of a well-placed
single screw.
Surgical Technique: “Retrograde” Single-Cut Single-Screw Capitate Osteotomy
Surgical Technique: “Retrograde” Single-Cut Single-Screw Capitate Osteotomy
A 26-year old male with right wrist pain for 1 year presented to our clinic. He had
midcarpal tenderness, flexion of 60 degrees, extension of 45 degrees, radial deviation
of 30 degrees, ulnar deviation of 30 degrees. Grip strength was 28 kg bilaterally.
Imaging demonstrated neutral ulnar variance and lunate sclerosis with coronal fracture
without carpal collapse ([Figs. 3] and [4]).
Fig. 3 Preoperative radiographs showing Kienbock's disease with lunate sclerosis.
Fig. 4 Computed tomography images showing lunate sclerosis and a coronal fracture without
carpal collapse.
The treatment options and prognosis were considered and discussed with the patient.
At wrist arthroscopy, the radiocarpal synovitis was debrided. The radiocarpal and
midcarpal joint surfaces were pristine. The wrist was graded as B1 using the Lichtmanand
Bain classification. It was decided to preserve and unload the lunate and perform
a capitate shortening.
At wrist arthroscopy, the articular cartilage was assessed using the Bain and Begg
classification.[5] Any radiocarpal synovitis was debrided.
Surgical Technique: “Retrograde” Single-Cut Single-Screw Capitate Osteotomy
Surgical Technique: “Retrograde” Single-Cut Single-Screw Capitate Osteotomy
We reviewed the plain radiographs to determine the correct alignment of the osteotomy.
Our aim is to make the osteotomy parallel to the capitolunate articulation. This usually
means that the osteotomy is slightly oblique ([Fig. 5]).
Fig. 5 The osteotomy is designed relative to the axis of the lunocapitate joint, at the
level of the STT joint. STT, scaphotrapeziotrapezoid.
The capitate is exposed through a dorsal approach. The extensor retinaculum does not
need to be divided, as the capitate is distal to it. We predrill the osteotomy so
that we try not to advance the K-wire into the unstable proximal capitate.
A small area of the third metacarpal base is removed with an osteotome to ensure the
correct line of entry of the wire. A threaded guidewire is then passed down the capitate.
On the anteroposterior plane, it is perpendicular to the proximal capitate joint surface.
On the lateral projection, the wire is placed parallel to the dorsal cortex of the
capitate. A cannulated drill is advanced over the wire and into the head of the capitate
([Fig. 6]). We then remove the drill and the wire.
Fig. 6 A small area of the third MC base is removed with an osteotome to ensure the correct
line of entry of the wire. A threaded guidewire is then passed down the capitate.
On the lateral projection, the wire is placed parallel to the dorsal cortex of the
capitate. A cannulated drill is advanced over the wire and into the head of the capitate.
MC, metacarpal.
With a 6-mm-wide fine-tooth oscillating saw, a transverse capitate osteotomy is made
distal to the midwaist (middle one-third) at the level of the STT joint ([Fig. 7]). The osteotomy is not opened to preserve the soft tissue envelope. A sharp (5-mm)
osteotome can be used to complete the osteotomy if necessary.
Fig. 7 With a 6-mm-wide fine-tooth oscillating saw, a transverse capitate osteotomy is made
distal to the midwaist (middle one-third), at the level of the scaphotrapeziotrapezoid
joint.
The K-wire is again inserted and then a single cannulated compression screw (2.2 mm)
is advanced over the wire to compress the osteotomy (Medartis, Switzerland) ([Fig. 8]). The position is confirmed to be satisfactory with fluoroscopy. Capsule and skin
are sutured in layers.
Fig. 8 The K-wire is again inserted and then a single cannulated compression screw (2.2 mm)
is advanced over the wire to compress the osteotomy.
The osteotomy is inherently stable following fixation; therefore, the wrist is only
immobilized with a volar splint for 2 weeks. The patient can then commence gentle
range-of-motion exercises. The patient can resume normal activity after 2 months.
Radiographs at 6 months in our patient confirmed union with capitate shortening of
1.5 mm ([Fig. 9]).
Fig. 9 Follow-up radiographs: united capitate osteotomy with no signs of avascular necrosis.
No further collapse in the lunate was noted.
Results
All our three cases of capitate osteotomy have united. In line with previous publications,
the patients did have some considerable pain relief but did not have a complete resolution
of pain. There was an improvement in function and grip strength. There have been no
cases with an infection, nonunion, AVN, or need for a salvage procedure.
Discussion
Panagis et al[22] reported that the intraosseous vascularity of the capitate developed from both the
palmar and dorsal aspects. Dorsally, two to four medium-sized vessels enter the distal
two-thirds of the concavity of that surface. The vessels course palmarly, proximally,
and slightly ulnarly, supplying the capitate body and head in 67% of the cases. Rarely,
some vessels entered proximally in the neck. Palmarly, one to three medium-sized vessels
enter slightly more proximally than the dorsal blood vessels but within the distal
half of capitate. In the study by Panagiset al, however, the dorsal vessels predominated
in most specimens. In 30% of specimens, there was anastomosis between the dorsal and
volar networks.
The capitate proximal pole is supplied in a retrograde manner similar to the scaphoid.
Cadaver studies have demonstrated vascular penetrations through the volar capsule
at the articular margin.[37] Hence, considering the unique vascularity, the osteotomy should be performed with
precaution in theleast traumatic way as possible to the bone as well as volar carpal
ligament to avoid the risk of AVN. It is recommended that the osteotomy is best performed
no more proximal than the capitate waist. The technique reported in this article uses
only a single cut, thereby decreasing the risk of compromising the capitate. We believe
that 1mm is enough to effectively unload the lunocapitate joint. Shortening more than
this risks overloading the remaining midcarpal joints and the development of osteoarthritis,
although this has not yet been proven.
There are few clinical studies on capitate shortening. Almquist reported a clinical
series of 83% revascularization and healing of the lunate after capitate shortening
with CH arthrodesis.[37]
Overall, isolated capitate shortening, as described in this article, is easiest with
a single cut and fixation with a single screw, which is adequate to stabilize the
shortened capitate. This procedure has the advantage of shorter rehabilitation, and
it can be combined with vascularization of the lunate if deemed necessary. Limitation
of this procedure is that it increases the loads on the STT and TH joints, which may
lead to degeneration later.[30]
