Keywords
scapholunate - ligament - injury - reconstruction - ligamentoplasty
Introduction
The scapholunate (SL) ligament and its pathology have been the subject of interest
in multiple lines of research over the last decades. The better understanding of the
anatomy and biomechanics of the carpus, as well as advances in minimally-invasive
surgery of the wrist and hand, resulted in a wide range of possibilities that are
now available for the treatment of SL lesions.[1] In contrast to traditional open surgery techniques, the current surgical treatment
is increasingly geared towards minimally-invasive techniques with the aim of preserving
proprioception and joint mobility as much as possible.[2]
Recent biomechanical studies[3]
[4]
[5]
[6]
[7] have highlighted the importance of the secondary wrist stabilizers and their role
in intracarpal mobility. For practical purposes, the extrinsic muscles can be divided
into two large groups:
-
Carpal pronator muscles: flexor carpi radialis (FCR) and extensor carpi ulnaris (ECU).
The FCR also presents a paradoxical effect of supination of the scaphoid.[8]
-
Carpal supinator muscles: abductor pollicis longus (APL), extensor carpi radialis
longus (ECRL), and flexor carpi ulnaris (FCU).
When the SL ligament is incompetent or injured, the scaphoid tends to assume a flexed,
pronated, and ulnar-deviated position, while the lunate assumes an extended position.
This characteristic alteration is known as dorsal intercalated segment instability
(DISI), and is mainly observed in complete injuries of the SL ligament.[9]
[10]
[11] The objective of SL reconstruction is to restore the correct intracarpal anatomical
relationships, to also recover adequate joint biomechanics.
Based on the described effect of the extrinsic musculature on intracarpal mobility,
and following the growing trend towards minimally-invasive surgery, we have developed
a new surgical technique for the reconstruction of the SL ligament. The objective
is to get the most out of the biomechanical properties of the donor tendon, in this
case, the ECRL, which acts as a supinator of the first row and is a stabilizer of
the SL interval.[3]
[4]
[5]
[6]
[7] Radial extensors have been previously used as donors for this type of ligamentoplasty.
Linscheid and Dobyns,[12] and later Kakar et al.,[13] have described plasties through open surgery using the ECRL as donor. Likewise,
Almquist et al.[14] have based their own technique on the use of the extensor carpi radialis brevis
(ECRB). The present study seeks to describe the surgical technique step by step, as
well as the indications and potential complications that may arise during its course.
Indications and Contraindications
Indications and Contraindications
The surgical indication for this technique coincides with that previously described
for other ligamentoplasties or techniques for SL interval reconstruction: Geissler
grades III to IV SL ligament injuries, reducible, and not associated with degenerative
changes in the joint surface.[2]
Acute injuries, grades I to II injuries that can be treated with other types of techniques,
and the presence of injuries with fixed deformity or degenerative changes in the joint
are contraindications to perform this type of technique.
Surgical Anatomy
The ECRL tendon inserts at the base of the second metacarpal, a place that is easy
to locate by palpation, especially when the upper limb is suspended from the traction
tower. Its muscle belly presents a volar-radial location in the proximal forearm,
being superficial to the ECRB, deep to the brachioradialis (BR), which we must dissect
and retract. The length of the tendinous path is extensive, easily exceeding 15 cm;
this anatomical characteristic makes it an ideal donor if the extraction of long plasties
is required. Between 5 cm and 7 cm proximal to its insertion, it passes through the
intersection with the tendons of the first slider, following its path distally through
the second extensor slider to the base of the second metacarpal ([Figure 1]). Both points are critical places of stenosis that can make it difficult to remove
the plasty if an adequate dissection is not performed.
Fig. 1 Dissection of the muscle belly and tendon of the ECRL. The asterisk indicates the
second extension slider and the intersection with the first slider. The arrow points
to the superficial radial nerve.
The superficial radial nerve travels deep to the BR muscle until it divides into terminal
sensory branches to the dorsum of the hand. It is a structure at risk during the plasty
extraction process if careful dissection and extraction are not performed ([Figure 1]).
The proximal pole of the scaphoid is almost constantly located at the intersection
between the extensor pollicis longus (EPL) and the tendons of the second extensor
compartment. At the distal level, these three tendons form a triangular space through
which we can directly access the joint capsule of the wrist and, through arthrotomy,
the proximal pole of the scaphoid and even the SL interval ([Figure 2A-B]).
Fig. 2 (A-B) Anatomical relationships of the extensors of the second extensor groove, EPL, joint
capsule, and proximal pole of the scaphoid.
The surgical anatomy applied to perform the dorsal approach to the lunate and the
volar portal has been described in previous articles.[2]
[15]
Surgical technique
-
Standard wrist arthroscopy:
With the upper limb suspended in a traction tower (Acumed, Hillsboro, OR, US), a standard
diagnostic arthroscopic procedure is first performed using the usual radiocarpal portals
3-4, 6R, and dorsal midcarpal portals ([Figure 3A]). This first surgical gesture is essential to typify the SL ligament injury, as
well as to determine if the patient meets the criteria to be submitted to this reconstruction
technique.
Fig. 3 (A) Placement of anatomical piece in the traction tower. (B) Distal location of the donor tendon. (C) Extraction of the ECRL hemitendon plasty.
-
ECRL plasty extraction
We make a longitudinal incision joining the 3-4 and the radial midcarpal portals.
Next, we dissect the subcutaneous cellular tissue, preserving as much as possible
the small veins of the back and the dorsal sensory branches. At the radial edge of
the incision, we can identify and dissect the ECRL tendon ([Figure 3B]). Next, we open and dissect the tendon sheath up to the entrance of the tendon in
the second extensor groove, releasing all the adhesions that may later hinder donor
extraction. Once identified at the distal level, we gently pull to locate it at the
proximal level, on the radial-volar border of the forearm. We extract a hemitendon
of approximately 12 cm in length ([Figure 3C]), marking the ulnar 2 mm with a number 0 or number 1 monofilament that we will use
to divide the tendon longitudinally. At this level, it is equally important to open
and dissect the tendon sheath, as well as tunneling the path with blunt material to
facilitate the extraction of the graft. Once the ulnar hemitendon is released, we
will use it to perform the ligamentoplasty, while the remnant will remain inserted
at the base of the second metacarpal to guarantee the functional continuity of the
donor muscle.
-
Scaphoid tunneling and plasty fixation with the DX SwiveLock device (Arthrex, Naples,
FL, US).
At the distal level, we perform a deep dissection until we reach the joint capsule.
During the dissection, special care must be taken not to injure the EPL tendon, which
can be observed at the proximal edge of the incision. We performed a longitudinal
arthrotomy, exposing the proximal pole of the scaphoid and its dorsal crest. Using
a guide needle, we locate the entry point for the tunnel in the scaphoid through radioscopic
control, which is located proximal to the crest following the longitudinal axis of
the bone ([Figures 4A-C]). The slightly more dorsal entry point enables us to further extend and supinate
the scaphoid. The tunnel is drilled using a 3.5-mm drill for the DX SwiveLock device,
with which we will fix the plasty inside the bone. During the tunneling process, it
is important to leave the distal cortex unharmed so that the device can press on the
bone. If the thickness of the plasty exceeds the size of the tunnel or fixation device,
making it difficult to insert, it can be thinned to fit exactly. Lastly, we check
the adequate anchorage to the scaphoid by means of traction.
Fig. 4 (A-C) Radioscopic control to locate the entry point in the scaphoid.
-
Tunneling of the lunate bone:
We locate the center of the bone by radioscopic control. We make a 2-cm longitudinal
skin incision centered at this level. To access the dorsum of the lunate, it is necessary
to open the retinaculum, retract the extensor tendons of the fourth compartment in
an ulnar direction, and perform a longitudinal arthrotomy as described in previous
techniques.[2]
[15] We make a tunnel parallel to the articular surface of the lunate bone guided by
radioscopy, first using a guide needle for its correct location, and later, a 3-mm
cannulated drill bit.
-
Recovery from the plasty and passage to the volar region:
Using an arthroscopic grasping forceps or a mosquito, we slide the plasty below the
extensor tendons and the joint capsule, intra-articularly, towards the incision made
on the lunate. In this step, we must be careful to pass the plasty under the EPL tendon
and the ECRB tendon so that they are not pinched under it. Next, we make a central
fly portal.[16] Using a straight SutureLasso (Arthrex), we recover the plasty towards the volar
region of the wrist. With the arthroscope located in the midcarpal joint, we apply
tension to the plasty, testing the adequate closure of the joint space by palpation.
We fix the plasty on the back of the lunate with a 3 × 8-mm biotenodesis screw (Arthrex).
Postoperative period
During the first three postoperative weeks, the joint must be kept immobilized with
a dorsal splint in extension and slight ulnar deviation to inhibit the action of the
extensor carpi ulnaris (ECU), which is detrimental to the SL. Subsequently, we remove
the splint and begin with passive mobility exercises to gain joint range, especially
flexion-extension, as well as active mobility in unloading the joint for another 3
to 4 weeks. From this period on, wrist proprioception exercises can be started, limiting
weight-bearing activities until the third postoperative month.
Complications
Prior to performing it on the live patient, we have developed this surgical technique
using 28 cadaveric pieces preserved fresh, from the Cadaver Donation Center of Universidad
Complutense de Madrid, Spain. The potential complications that we have been able to
verify are:
-
During the removal of the plasty:
-
Injury to neurovascular structures if an adequate dissection is not carried out; in
this case, the structure with the greatest risk of being injured is the superficial
radial nerve.
-
Error in identifying the donor tendon. At the distal level, the ECRL and ECRB tendons
are in proximity, so errors may occur when identifying the donor. It is important
to always check that the tendon is correct; when in doubt, the ECRL is always the
most radial and is easily identified at the base of the second metacarpal.
-
Difficulty in extracting the plasty if an adequate dissection of the tendon sheath
is not performed. It is essential to tunnel the path with a blunt instrument to avoid
potential points of stenosis that can make extraction difficult (intersection with
the first slide, extensor retinaculum, EPL).
-
Donor rupture during extraction. The development of this complication makes it practically
necessary to choose another donor to continue with the surgical technique, since the
tendon remnant is usually of insufficient length to continue.
-
Scaphoid tunneling:
-
During capsular dissection and arthrotomy, the EPL tendon is located proximal to the
incision. One must be careful not to produce an injury to it. Likewise, care must
be taken not to injure the ECRB tendon that is ulnar and in proximity to the donor.
-
Anomalous location of the tunnel: if an entry point is made that is excessively dorsal
(distal to the crest of the scaphoid) or the tunnel does not develop in the axis of
the bone, it can lead to complications such as rupture of the wall or perforation
of the distal cortex. Therefore, tunneling of the carpal bones must be performed under
radioscopic guidance.
-
During the course of the plasty:
-
The plasty should not exceed 2 mm in thickness, as it may compromise the press of
the DX SwiveLock device inside the bone. In the case of excessively thick plasties,
we recommend thinning them until a correct diameter is obtained that enables the safe
implantation of the device.
-
During its passage through the dorsal region of the wrist towards the lunate, it is
important that the plasty travels below the wrist extensors and the joint capsule.
Its passage under the EPL and the ECRB is especially critical; if it is not carried
out properly the tendons can be trapped under the plasty when it is subjected to tension.
Clinical case
A 42-year-old male with no personal history of interest, who practiced sports on a
regular basis, especially climbing. The patient had a history of repetitive trauma
related to sports activities, not a history of recent acute trauma.
He was evaluated in Outpatient Consultations by his traumatologist due to nonspecific
pain in the right wrist that had lasted for months. The magnetic resonance imaging
(MRI) study showed an SL ligament injury ([Figure 5A-B]), which is why the patient was referred to our center.
Fig. 5 (A-B) Magnetic resonance imaging scan with scapholunate ligament injury and DISI deformity.
Upon physical examination, the patient presented pain in the dorsal region of the
wrist with activity, and pain at the tip of the finger over the SL interval. The Watson
test was positive. The patient had full passive range of motion (PROM) and active
range of motion (AROM) of the wrist, and reported pain in the last degrees of extension
or when carrying loads. The grip strength in the right hand (Jamar-type dynamometer)
was of 30, markedly decreased compared to the contralateral hand. We requested a dynamic
study using functional radiographs that showed opening of the SL space ([Figures 6]), which is why we suggested diagnostic arthroscopy and treatment by means of reconstruction
withSL ligamentoplasty, using the ECRL as a donor ([Figures 7A-C]).
Fig. 6 Functional study with opening of the SL space in the right wrist.
Fig. 7 (A) Placement of the patient in the traction tower. Distal and proximal incisions for
extraction of the plasty. (B) Arthroscopic image of SL ligament injury with evident step between the scaphoid
and lunate. (C) Image of ligamentoplasty on the dorsum of the wrist. (D) Arthroscopic control after reconstruction of the SL ligament.
The patient is currently in his fifth postoperative month, and he presents disappearance
of the previous symptoms of joint instability, as well as a negative Watson test.
The score on the Visual Analog Scale (VAS) with activity improved from 7 in the preoperative
period to 2 at the present time when carrying out activities with load. The grip strength
measured by a Jamar-type dynamometer is currently at 41, remaining lower than on the
contralateral hand. He performs activities of daily living without limitation, and
is working with progressive weight bearing. The PROM and AROM present an extension
deficit of −20 degrees. The functional score on the Quick Disabilities of the Arm,
Shoulder and Hand (DASH) questionnaire has improved from 33 preoperatively to 16 at
the present time.
