Midcarpal Ultra-wide Scapholunotriquetral Capsulo-ligamentoplasty (MUSCL) Procedure

Abstract

Background

Arthroscopic dorsal capsuloligamentous reconstruction (ADCLR) has gained popularity in addressing symptomatic scapholunate instability without radiographic malalignment (European Wrist Arthroscopy Society [EWAS] grade IIIB/IIIC/IV).

Case Description

A midcarpal ultra-wide version of the ADCLR is described, wherein suture needles are directly inserted into the midcarpal joint without prior entry into the radiocarpal joint. A wide “bite” is taken to plicate the dorsal radiocarpal (DRC), dorsal intercarpal (DIC), and dorsal scapholunotriquetral (DSLT) ligaments. An incision is then performed to allow direct visualization suture passage beneath the extensor tendons. A total of 68 consecutive patients received a midcarpal ultra-wide scapholunotriquetral capsulo-ligamentoplasty (MUSCL) between July 2020 and November 2023. Mean follow-up was 8 months (range 2–24 months). The mean pre- and postoperative range of dorsiflexion was 64.54 and 68.32 degrees, respectively ( p  = 0.14). The mean preoperative and postoperative range of palmarflexion was 71.89 and 67.18 degrees, respectively ( p  = 0.18). A significant improvement of 35.19 points was noted in mean QuickDASH score post-surgery ( p  < 0.001).

Literature Review

Several modifications of the ADCLR exist, including those that take a wider bite incorporating capsule from the mid-carpal joint as well as augmentations with capsuloligamentous imbrications and suture anchor repairs. These approaches yield good pain relief, improved range of motion, and enhanced grip strength when compared with open techniques.

Clinical Relevance

This technique eliminates the challenging maneuver of passing needles from the radiocarpal joint into the midcarpal joint, offering both procedural simplicity and efficacy, with promising short-term outcomes. Long-term follow-up is necessary.

It is increasingly recognized that the scapholunate interosseous ligament (SLIL) plays a secondary role in maintaining scapholunate (SL) stability, with the primary contribution coming from active muscular stabilization, proprioceptive feedback, and the integrity of capsular ligaments, including the dorsal radiocarpal ligament (DRC), dorsal intercarpal (DIC) ligament, dorsal scapholunotriquetral (DSLT) ligament, long radiolunate ligament (LRL), and volar scaphotrapeziotrapezoidal (vSTT) ligament complex. ^{1 2 3} Cadaveric studies have demonstrated that dorsal intercalated segment instability (DISI) occurs only after disruption of the vSTT ligament complex, both scaphoid (DIC-S) and lunate (DIC-L) insertions of the DIC, or the DRC from the lunate. ^{4 5 6}

Contemporary strategies for addressing scapholunate instability and halting the degenerative process have shifted toward a ligament-specific approach rather than treating scapholunate diastasis alone. ⁷ Various arthroscopic and mini-open techniques have been devised to negate the drawbacks of traditional open approaches and provide a modular approach to address specific ligamentous deficiencies. The repair/augmentation of dorsal capsular ligaments (RADiCL) procedure aims to plicate the DRC and DIC, and reconstruct their insertions to the dorsal non-articular surface of the lunate. ⁸ The arthroscopic dorsal capsuloligamentous repair (ADCLR) plicates the DCSS and repairs the dorsal capsular attachments of the SLIL. ^{1 2 9 10} Reconstruction of the volar STT ligaments can be used to augment the ADCLR procedure in European Wrist Arthroscopy Society (EWAS) grade IV/V instabilities. ¹¹ The minimally invasive radiolunate imbrication neutralization (MIRLIN) procedure has recently been described, and may be indicated if the lunate is extended and ulnar-translocated. ¹²

We describe a novel technique which provides an ultra-wide plication of the dorsal capsule (in particular, the DIC, DRC, and DSLT ligaments) in settings where standard ADCLR may be difficult to perform ( Fig. 1 ).

Fig. 1.

Cadaveric dissection demonstrating the dorsal scapholunotriquetral ligament (arrows), scaphoid (Sc), triquetrum (Tq), and dorsal intercarpal ligament (DIC). The blue line represents the dorsal scapholunotriquetral imbrication afforded by the midcarpal ultra-wide scapholunotriquetral capsulo-ligamentoplasty (MUSCL) technique. MC side, Midcarpal side. (Adapted with permission from Williams D, Raja S, Ross M, Couzens G, Wolfe S. New concepts in carpal instability. In: Geissler, W, eds. Wrist and Elbow Arthroscopy with Selected Open Procedures. Cham: Springer;2022:173–185.)

Anatomy

The DRC, DIC, and DSLT share an insertion on the dorsal tubercle of the triquetrum ( Fig. 2 ). ¹³ The DRC originates on the dorsal margin of the distal radius, ulnar and distal to Lister's tubercle, and runs obliquely to insert on the dorsal tubercle of the triquetrum, with attachments to the dorsal lunate in most patients. ¹⁴ It prevents ulnar translation of the proximal row of the carpus. ¹⁵ The DIC arises from the dorsal tubercle of the triquetrum and inserts onto the dorsal groove of the scaphoid. Together, the DIC and DRC form a radially based V-shaped structure that provides dorsal stability of the proximal pole of the scaphoid throughout wrist range of motion. ¹⁴ The DSLT ligament forms a deep proximal component of the DIC and has strong attachments to the lunate, effectively attaching the DIC to the proximal carpal row. It acts as a dorsal midcarpal “labrum” for the proximal capitate, preventing dorsal translation, excessive loading, and subsequent extension of the lunate. ¹³

Fig. 2.

Schematic of dorsal intercarpal, radiocarpal, and scapholunotriquetral ligaments. Source: Original Illustration by © M. Crespi.

Indications/Contraindications

This procedure is indicated in isolation in the setting of symptomatic scapholunate instability with arthroscopic widening and no radiographic malalignment (EWAS grades IIIB–IV). Adjunct procedures will be required in the presence of radiographic scaphoid flexion, lunate extension, or wide diastasis. Optimal recovery requires a period of postoperative immobilization and hand therapy—thus, patient compliance is key.

Technique

Following an appropriate anesthetic, the patient is positioned supine with an above-elbow tourniquet. The arm is placed into a traction tower with corresponding countertraction to impart the longitudinal distraction required for articular access. Our preference is to perform this procedure via “dry” arthroscopy—however, a “wet” technique can also be utilized.

Landmarks include the ulnar styloid and extensor carpi ulnaris (ECU) tendon ( Fig. 3A ), as well as any large dorsal veins, which are to be avoided when establishing the far ulnar portal. The radiocarpal joint is initially accessed via standard ¾ and 6R portals, and any synovitis debrided to visualize and assess the proximal aspect of the SLIL.

Fig. 3.

( A ) Landmarks include the ulnar styloid, extensor carpi ulnaris (ECU) tendon, and any dorsal veins that lie close to the far ulnar portal. ( B ) The first needle pierces the skin distal and radial to the radial portal. ( C ) Arthroscopic image showing the needle entering the midcarpal joint. ( D ) The second needle pierces the skin proximal to the far ulnar portal and distal to 6R. ( E ) Arthroscopic image showing the needle entering the midcarpal joint just distal to the triquetrum. ( F ) The two suture ends emerging from the radial working portal are tied together with a granny knot and one suture is used to shuttle the other. ( G ) A 2- to 3-cm transverse incision is performed incorporating the radial portal allowing the two suture ends to be located in the subcutaneous tissues and retrieved into the incision. An arthroscopy probe is used to guide each suture end under the extensor tendons while remaining superficial to the capsule. ( H ) The two suture ends are tied securely over the capsule using a 1-mL syringe as a knot pusher.

The far ulnar portal is established. This portal is key in enabling the ultra-wide plication by providing a panoramic view of the midcarpal joint. It is established in line with the 6R portal, radial to the ECU tendon, to enter between the hamate and triquetrum. The radial portal is then established directly over the SL interval, through the fourth compartment.

Instability is confirmed by probing the scapholunate interval and attempting a “drive-through” maneuver. Once the deformity is deemed reducible and articular surfaces are adjudged normal, the MUSCL can be performed.

Two “suture darts” are prepared, whereby an end of a dyed 2/0 polydioxanone (PDS) suture is passed through a 21-gauge needle, with approximately 3 cm left protruding from the bevel. A 1-mL syringe can be connected to the needle to create the dart and enable precise maneuverability.

With the camera in the far ulnar portal, the first needle is inserted distal and radial to the radial portal to enter the midcarpal joint midway along the scaphoid ( Fig. 3B, C ). By positioning the needle close to the scaphoid, this suture should pass through the DSLT ligament and the most radial aspect of the DIC-S. An arthroscopic grasper is used to retrieve one suture end through the radial portal, and the suture dart is disassembled. The two suture ends are clipped together and positioned over the thumb.

With the camera maintained in the far ulnar portal, the second suture dart is inserted proximal and radial to the far ulnar portal to enter the midcarpal joint just distal to the triquetrum ( Fig. 3D, E ). The needle passes through the confluence of the DRC and DIC ligaments on the triquetrum. By staying close to bone and maintaining a low trajectory over the triquetrum, the suture also captures the DSLT ligament ulnar to the lunotriquetral joint. A grasper is again utilized to retrieve one suture end through the radial portal. The suture dart is disassembled and the two suture ends clipped together.

The two suture ends emerging from the radial portal are now tied together with a granny knot, and one suture used to shuttle the other by gently withdrawing the suture end emerging from the ulnar needle site ( Fig. 3F ). As per surgeon's preference, a non-dissolvable suture can be used in place of the dissolvable PDS, or a looped suture can be utilized to shuttle a single heavier suture end, such as 0 Ethibond. This might be considered in higher grade instabilities or for high demand patients.

A 2- to 3-cm transverse incision is created incorporating the radial portal. The skin is retracted to visualize the extensor tendons. The suture ends are located in the subcutaneous tissue via blunt dissection and are retrieved into the center of the incision, passing under the tendons while remaining superficial to the capsule ( Fig. 3G ).

Once the two suture ends have been centralized without any tendon entrapment, the capsular imbrication can be performed. The knot is tied in traction with the wrist in neutral position. A 1-mL syringe can be utilized to act as a knot pusher if necessary ( Figs. 3H and 4 ). Stability of the scapholunate interval is confirmed arthroscopically prior to trimming the suture ends. If required, the MUSCL can now be augmented with an open volar STT ligament reconstruction to control scaphoid rotation. ¹¹

Fig. 4.

( A ) Arthroscopy portals utilized in this technique including the far ulnar portal. ( B ) The first needle pierces the skin distal and radial to the radial portal, and is retrieved through the radial portal, picking up the dorsal intercarpal (DIC) and ligament (DSLT). ( C ) The second needle pierces the skin proximal to the far ulnar portal and distal to 6R, and is retrieved through the radial porta, picking up the confluence of the dorsal radiocarpal (DRC) and DIC, as well as the DSTL. ( D ) The two suture ends emerging from the radial working portal are tied together with a granny knot and one suture is used to shuttle the other. ( E, F ) After making a 2- to 3-cm transverse incision incorporating the radial portal, an arthroscopy probe is used to guide each suture end under the extensor tendons while remaining superficial to the capsule. ( G ) The two suture ends are tied securely over the capsule using a 1-mL syringe as a knot pusher. Midcarpal radial. Source: Original Illustration by © M. Crespi.

The wrist is immobilized in neutral in a splint for 4 weeks, after which motion is gradually reintroduced, commencing with dart throwing motion. Loading of the wrist is prohibited for 12 weeks.

Complications

Potential complications include those associated with wrist arthroscopy, such as traction neuropraxias, tendon lacerations, and iatrogenic cartilaginous injury. ¹⁶ Tendon entrapment may occur if the sutures are retrieved on either side of an extensor tendon—care must be taken to ensure this does not occur prior to securing the imbrication ( Fig. 5 ).

Fig. 5.

Demonstration of tendon entrapment which occurs if the sutures are retrieved on either side of an extensor tendon—care must be taken to ensure this does not occur prior to securing the imbrication.

Results

A series of 68 consecutive patients underwent the MUSCL procedure for symptomatic scapholunate instability (EWAS grades IIIA–V) between July 2020 and November 2023. All patients were reviewed by the senior author at regular intervals. Range of motion, grip strength, and QuickDASH scores were recorded preoperatively and at final follow-up, with statistical analysis performed using Python 3.x (Python Software Foundation, Wilmington, Delaware, United States). Statistical comparisons were performed using paired t-tests for dependent variables and Welch's t-tests for unpaired data. ¹⁷

Patient characteristics are summarized in Table 1 and postoperative outcomes are presented in Table 2 . A significant improvement in QuickDash of 35.19 was noted following surgery ( p  < 0.001). Mean postoperative wrist extension had increased, while flexion had decreased—however, neither change was significant.

Table 1. Patient characteristics.

Characteristic	Value
Gender
Female	43 (63.2%)
Male	25 (36.8%)
Age	Mean 36 years (range 15–69)
Dominant side injured	43 (63.2%)
Manual worker	28 (41.2%)
Mechanism of injury
Motor vehicle accident	7
Sports	23
Operating machinery	7
Lifting heavy load	15
Fall onto outstretched hand	10
Other	6
Time since injury to surgery	Mean 11 months (range 20 days–120 months)
Follow-up	Mean 8 months (range 2–24 months)
Lost to follow-up	1 (1.5%)

Table 2. Patient outcomes (at mean follow-up of 8 months following surgery).

	Pre-op mean value	Post-op mean value	p -value (α = 0.05)
Dorsiflexion	64.54 degrees ( n  = 66 patients)	68.32 degrees ( n  = 66 patients)	p  = 0.1415
Palmarflexion	71.89 degrees ( n  = 66 patients)	67.18 degrees ( n  = 66 patients)	p  = 0.1752
Grip strength of affected side	41.88 kg ( n  = 4 patients)	35.63 kg ( n  = 27 patients)	p  = 0.4020
Grip strength of unaffected side	48.50 kg ( n  = 4 patients)	42.61 kg ( n  = 27 patients)	p  = 0.4462
QuickDASH	49.57 (range 15.9–95.45) ( n  = 16 patients)	14.38 (range 0–97.73) ( n  = 16 patients)	p  = 0.000059

Discussion

The advent and uptake of wrist arthroscopy have resulted in a re-evaluation of the management paradigm for scapholunate instability. Following recognition that scapholunate stability is maintained by an anatomic “scapholunate complex” consisting of well-defined capsuloligamentous structures (and that the scapholunate ligament itself likely plays a limited role), there has been a shift away from open procedures, and toward arthroscopic repairs and imbrications of the aforementioned complex. ²

Traditional reconstructive techniques (such as open capsulodesis, tenodesis, or ligament reconstructions) utilize an open dorsal approach, which leads to scarring and stiffness. ¹⁸ An open approach inherently requires dissection through many of the critical capsuloligamentous stabilizers, which is counterintuitive when attempting to restore scapholunate stability. Although the open dorsal ligament-splitting capsulotomy theoretically maintains integrity of the DIC and DRC, cadaveric studies reveal that it violates their lunate insertions, resulting in dorsal scaphoid translation and a DISI deformity. The proximal row remains malaligned even following suture anchor repair during closure. ^{19 20} A dorsal capsulotomy may also damage the vascular supply to the capsular ligaments (diminishing their healing potential) and the posterior interosseous nerve (impairing proprioception). ^{21 22}

The reconstructive procedures also have other drawbacks—they are prone to complications such as tendon loosening, fracture through drill holes, and avascular necrosis. Reconstructions do not replace like for like—tendon grafts lack mechanoreceptors and cope poorly with the intricacies of wrist motion—and lack long-term evidence demonstrating efficacy in preventing scapholunate advanced collapse. ^{1 19 23 24}

To address these shortcomings, several arthroscopic techniques have been devised to restore stability in a minimally invasive fashion, diminishing the risk of postoperative stiffness and damage to the surrounding soft tissues when compared with their open counterparts. ^{1 2 9 10} Wahegaonkar and Mathoulin first described a repair of the DCSS by passing two sutures through the dorsal capsule and remnants of the scapholunate ligament via the ¾ portal and retrieving them in the midcarpal joint to tie them to each other. The sutures are then tensioned around the ¾ portal to recreate the internal brace that binds the dorsal capsule to the dorsal portion of the SLIL. ¹⁰ This technique has been further modified to incorporate capsule from the mid-carpal joint—the wide ADCLR. ²⁵ ADCLR may be combined with scapholunate ligament repairs using suture anchors. ^{26 27} Studies show that these techniques yield good pain relief, improved range of motion, and greater grip strength when compared with open techniques, with near-normal radiographic parameters at 1 year follow-up. ^{25 28 29}

The MUSCL aims to imbricate the DRC, DIC, and DSLT ligaments, which are generally healthy and intact. This procedure does not require instrumentation of the SLIL itself, which is advantageous in the setting of poor quality or completely avulsed ligamentous remnants. The bite of capsule is very wide, which provides more latitude for plication, and it incorporates the DSLT ligament for a robust result. The procedure is technically simple—all suture work is performed in the midcarpal space, obviating the need to maneuver between the radiocarpal and midcarpal joints and streamlining suture passage. The use of an incision to visualize the tendons minimizes the risk of tendon entrapment inherent to minimally invasive approaches. ²⁵

This procedure may be utilized independently or combined with other minimally invasive procedures as part of a modular reconstruction. The senior author has previously published a technique for volar STT reconstruction, and prefers to utilize this following the MUSCL procedure for EWAS grade V scapholunate instability. ¹¹ If the lunate is extended and ulnar translocated, the MIRLIN procedure may be considered. ¹² When the MUSCL procedure is augmented dorsally with a RADiCL, the technique becomes similar to the “supercapsuloplasty” in which the DIC, DRC, and capsule are re-tensioned and the midcarpal labrum is recreated. ³⁰ Ultimately, the choice of procedure is guided by the specific ligamentous injuries and associated kinematic disruptions encountered clinically.

Promising short-term outcomes are noted following the use of the MUSCL for symptomatic scapholunate instability, with maintenance of motion and improvements in patient-reported outcome measures. These results are similar to those reported following the ADCLR procedure; slightly inferior range of motion and QuickDASH scores are likely attributable to a shorter duration of follow-up. ¹⁰

This study has several limitations. The data presented in this study is retrospective, derived from medical notes documented during postoperative clinic appointments with both the surgeon and hand therapist, and is restricted by missing data points, infrequent documentation of specific pain scores, and sparse recordings of grip strength measurements. The relatively short follow-up period further limits interpretation of cause and effect. Despite these constraints, this dataset utilizes parameters employed by other authors when reporting on the treatment of scapholunate instability. Radiographic measurements were not collected, and it is acknowledged that (as with other arthroscopic scapholunate procedures) a persistent scapholunate diastasis may be observed on postoperative radiographs. ²⁴ However, this gap is unlikely to be of clinical relevance, with coupled scapholunate motion and correction of radiolunate and capitolunate angles more critical in preventing pain and degeneration. ^{2 31 32}

Conclusion

The MUSCL technique offers several advantages in addressing symptomatic scapholunate instability. The width of spacing between the two needles permits mechanically advantageous plication of the DRC, DIC, and DSLT ligaments, affording stability even in the setting of complete avulsion of the scapholunate ligament. This technique obviates the need to maneuver between the radiocarpal and midcarpal joints by limiting suture passage to the midcarpal space alone. Direct visualization of the extensor tendons minimizes the risk of tendon entrapment while tensioning and securing the suture tie over the capsule. The MUSCL can be combined with other arthroscopic or minimally invasive techniques as part of a ligament-specific modular approach to scapholunate instability. Further clinical results will be useful to assess long-term efficacy.