Scapholunate advanced collapse (literature review)

Full Text

Introduction

Scapholunate collapse (SLAC) is a common form of osteoarthritis of the wrist [1] that affects the radiocarpal and intercarpal joints [2] and is characterized by progressive deformity, instability, and arthritis due to chronic dissociation of the scaphoid and lunate bones resulting from chronic injuries of the scapholunate interosseous ligament ( SLIL). The SLIL is considered the primary stabilizer of these bones, while the scaphotrapezoid and radioscaphocapitate ligaments are considered secondary stabilizers of the scapholunate joint [3]. SLIL consists of three parts including dorsal, membrane and palmar portions [4]. The dorsal and palmar parts are the genuine ligaments of the capsule. The membrane part consists of fibrous cartilage and multidirectional bundles of collagen fibers. The dorsal part [5] is composed of transversely oriented collagen fascicles surrounded by connective tissue containing neurovascular bundles and has the greatest mechanical strength.

Material and methods

The original literature search was conducted on key resources including Scientific Electronic Library (www.elibrary.ru) and the National Library of Medicine (www.pubmed.org). Search strategy was comprised of keywords: scapholunate advanced collapse, SLAC, scapholunate instability, proximal row carpectomy. The review of 59 articles was performed.

Etiology

Chronic SLIL injuries usually result from trauma, and the extent of the wrist injury can be underestimated and wrist sprain is often diagnosed. Arthroscopy indicates SLIL damage in 21.6% of cases of intra-articular radial fractures and in 6.7% of cases of extra-articular fractures [6]. SLIL injuries result in chronic instability and arthritis of the wrist joint, and timely diagnosis and treatment are essential [7]. Other authors believe that there is currently no evidence that SLIL reconstruction for acute and chronic injuries can slow down or prevent arthritis [8]. The scaphoid can change the shape and location due to chronic SLIL injuries causing mechanical injury to the capitate bone, which migrates between the lunate and scaphoid bones over time. SLAC is common for male (80.3%) young and middle-aged individuals (53.1 ± 10.4); 49% of patients are engaged in manual labor, 69.5% have a history of trauma with the duration of symptoms of 10.3 ± 13.3 years [9]. SLAC may also be a manifestation of crystalline arthropathy with pyrophosphate dehydrate deposits [10].

Clinical diagnosis of SLAC

If the patient has a history of falls onto an outstretched arm, a SLIL injury should be suspected. It may be isolated or accompany fractures of the distal radius or scaphoid. Sometimes SLIL lesions develop secondary to inflammatory arthritis, such as pseudogout, with an injury being often bilateral [8]. There is a case report of iatrogenic SLAC with wide excision of a ganglion cyst on the dorsum of the hand [11]. SLAC may be asymptomatic for many years and is usually associated with pain aggravating with heavy work, and is sometimes accompanied by a clunking sensation when moving [12]. The pain is accompanied by a decreased range of motion in the joints and a weakened wrist grip. Scapholunate instability may exist without apparent manifestations. Moderate swelling of the wrist can be seen in the acute phase. There is significant pain with the motion in case of progressive SLAC. The Watson's scaphoid shift test is used for the diagnosis of scapholunate dissociation. The examiner's thumb applies pressure to the scaphoid tubercle while the subject's hand is moved from ulnar deviation to radial deviation. Negative test suggests scaphoid moving normally, pushing back on the examiner's thumb with ulnar deviation of the wrist. A positive Watson's test indicates a total scapholunate injury or wrist weakness. When the pressure of the thumb is released, the scaphoid often shifts back in palmar direction with a “thunk”. The test has a low specificity and sensitivity [13], and a negative result is not a reason to refuse additional diagnostic methods.

Terminology and diagnostic imaging

There are four commonly used terms used to describe the pathology seen in the pathway to the development of SLAC wrist [14]. These terms are scapholunate dissociation, scapholunate diastasis, rotary subluxation of the scaphoid and dorsal intercalated segment instability (DISI). These pathological entities can be identified on imaging by measuring specific angles and distances between the different bones of the wrist. The imaging findings which can be seen with scapholunate dissociation include scapholunate diastasis, which is described as having a scapholunate distance greater than 4 mm as measured on the posteroanterior view. Scapholunate dissociation may be suspected when the scapholunate interval is 2–4 mm. There are several imaging findings that can be observed with rotary subluxation of the scaphoid. On the lateral radiograph, an increased scapholunate angle >60–80° (the scaphoid is tilted palmarly) and/or radioscaphoid angle >60°. The scaphoid tubercle projects into the scapholunate diastasis as a result of the scaphoid rotation of bone, which is referred to as the “signet ring” or cortical ring sign [15]. On the lateral wrist radiograph, DISI demonstrates dorsal tilt of the lunate with a scapholunate angle >80° (60–80° is suspected DISI), a radiolunate angle >10°, capitolunate angle >30°. Widening of the scapholunate interval on imaging has been called the “Terry Thomas sign”, referring to the famous actor with a prominent gap in his front teeth [16]. MRI is useful in that in addition to diastasis, it may also directly show a SLIL tear. Plain wrist radiographs are usually sufficient to make the diagnosis of the progressive course of SLAC; MRI is practical for the diagnosis of the initial stages of the condition demonstrating thin articular surfaces of the scaphoid, synovitis of the scaphoid facet of the distal radius, the capitolunate joint and the radiocarpal and intercarpal joints. Ultrasound can be used as a low cost alternative to MRI to identify scapholunate ligament tears. Ultrasound is particularly useful for assessing patients with prior wrist fractures with subsequent surgical fixation hardware placement [17]. Research into the possibilities of tomosynthesis for questionable visualization of wrist injuries is promising [18].

Pathogenesis of SLAC

On imaging, the three [3, 19] or [20] stages of SLAC arthropathy can be demonstrated. In stage I SLAC tthe proximal part of the scaphoid and the styloid process of the radius are affected. AP radiographic views and CT scans show sharp spurring on the radial side of the scaphoid and at the radial styloid process, with loss of the normal rounded curvature of the radial styloid process and signs of local arthritis of the scaphoid facet. In Stage II SLAC the rest of the radioscaphoid joint is affected with progression to narrowing of the radioscaphoid joint, sclerosis of the entire scaphoid facet of the distal ray, followed by Stage III SLAC where there is narrowing of the capitolunate joint. Ultimately, proximal migration of the capitate with ulnarward displacement of the lunate occurs. In Stage IV, degenerative arthritis of the semilunar radial joint occurs. SLAC can develop without acute or chronic trauma in 26% of patients with crystal deposition arthropathy [21]. Deposition of pyrophosphate dehydrate crystals in the interosseous scapholunate ligament leads to ligament laxity and disruption and thus rotation of the scaphoid. Crystal arthropathy can be associated with bilateral involvement, triangular fibrocartilage calcification, periarticular soft tissue calcification, subchondral cysts and osteoarthritic changes involving the metacarpophalangeal joints, with hook-like or drooping osteophytes at the radial aspects of the metacarpal heads [22].

SLAC treatment options

For mild SLAC arthropathy conservative non-surgical measures are the first line therapy including NSAIDs, wrist splinting and intra-articular steroid injections. However, there are no publications reporting the effectiveness of conservative treatment of SLAC in the world literature [8]. Some authors indicate that pharmacological pain control and splinting are effective in elderly patients and crystal arthropathies [20]. Scapholunate dissociation and lunate necrosis resulting from SLIL rupture was successfully treated with intra-articular injections of amnion and umbilical cord particle [23] after failed conservative treatment of pain.

Long-term results of wrist denervation with neurectomy of the anterior and posterior interosseous nerves demonstrated the procedure as practical for patients with maintained range of motion to improve pain, grip strength with no effect on range of motion [24]. Resection of the styloid process is contraindicated in SLAC to prevent scaphoid instability at a long term [20]. Resection of the distal pole of the scaphoid can provide good short-term results for SLAC I-II with instability and osteoarthritis progressing over time [25–27]. Proximal carpal resection (PRC) may be recommended for stages I-II and stage III and minimal damage to the capitate cartilage [28]. It should be noted that the newly formed joint between the capitate and the radius is not congruent with the risk for good surgical results deteriorating over time, and PRC cannot be recommended for patients younger than 35 years   [29]. Four-corner arthrodesis with scaphoid resection and arthrodesis of  lunate, capitate, hamate and triangular bones can be reserved for patients with stage III arthritis [3].The surgery improves pain, preserves range of motion and hand grip in 50% and 75%, correspondingly, as compared to the contralateral side [30-32]. The authors of the technique reported use of Kirschner wires for fixation of arthrodesed bones, but fixation methods have been debated for several decades. Compression screws [33] and braces [32] have been used successfully. A circular dorsal plate was used to stabilize arthrodesis to speed up rehabilitation (after 4 weeks) [34-35]. Complications associated with the technique included broken construct, irritation, dorsal impingement [31, 36-38].The use of Herbert screws for four-corner arthrodesis has become common [39-40]. There are studies that demonstrate the importance of  crossing screws placed at an angle of 90 and the retrograde insertion  to preserve lunate cartilage [41]. Encouraging results were reported with bioabsorbable plates used for 4-corner arthrodesis in 10 patients [42]. A comparative analysis of open and arthroscopic arthrodesis showed comparable levels on pain and clinical scales, similar radiological data, but a greater range of motion was seen with arthroscopy [43]. Radioscaphoid-lunate arthrodesis is the method of choice for stage IV arthritis. Intercarpal joint mobility is maintained by dart-thrower’s motion (DTM) [44–45]. Total wrist arthrodesis can be used as a revision procedure and as a primary surgery for stage IV arthritis and for individuals engaged in heavy physical labor [46].PRC modifications. The rationale for PRC modifications includes a review of long-term results of the procedure with a minimum follow-up period of 15 years; few patients could return to their previous hard physical work and the patients experienced pain with maintained range of motion [47]. Capsular interpositional allografts [48], restoration of the capitate bone surface with pyrocarbon implants [49, 50, 51], osteochondral grafts [52, 53] are used with PRC modifications.Although no effect on functional parameters and severity of pain is reported with interpositional capsular grafts have, osteochondral grafts allow restoration of the articular cartilage of the capitate bone [54]. The use of capsular interpositional allografts, pyrocarbon implants, osteochondral grafts to restore the capitate bone surface require studies of long-term results [55]. Dorsal capsudodesis and restoration of the lining of the radioscaphoid joint using two types of bioabsorbable implants was used for young and active patients with SLAC I-II [56]. Dorsal capsulodesis is aimed at strengthening the dorsal intercarpal ligaments taking into account their role in dynamic and static scapholunate instability [57]. Although bioabsorbable implants were supposed to ensure restoration of cartilage grip strength can remain weak with the range of motion being limited after the combined operation. Although dorsal capsulodesis was shown to reduce pain, the procedure failed to relieve it completely in many cases. Radiological findings showed no alignment of the carpal bones in chronic scapholunate dissociation [58]. Adjuvant surgeries and effective methods for restoring articular cartilage are essential for young patients with early manifestations of wrist arthritis [57]. Total wrist arthroplasty is associated with higher complication rate than total arthrodesis and therefore cannot be recommended for widespread use; careful patient selection is required [59]. Conclusion The terms “scapholunate collapse”, “SLAC syndrome”, “osteoarthrosis of the radioscaphoid joint”, “carpal joint collapse”, which are used in the literature, denote a single clinical and pathophysiological picture of the disease. The problem of choosing surgical treatment depending on the clinical stage of the disease has no generally accepted solutions. Adjuvant operations aimed at greater  effective treatment is essential for young active patients

About the authors

Natalya Shchudlo

НМИЦ ТО имени акад. Г.А. Илизарова

Email: nshchudlo@mail.ru

Доктор медицинских наук

г.Курган, Марии Ульяновой д.6

Shyngys Kuttygul

НМИЦ ТО имени акад. Г.А. Илизарова

Author for correspondence.
Email: artana.kaz@gmail.com
ORCID iD: 0009-0009-1072-468X

Травматолог- ортопед, кистевой хирург

Россия, г.Курган, Марии Ульяновой д.6

Artem Mironov

ФГБУ «НМИЦ ТО им. Р.Р. Вредена» Минздрава России

Email: ortopedix@yandex.ru
ORCID iD: 0009-0001-9273-8680
SPIN-code: 9915-1012

Травматолог-ортопед

г.Санкт-Петербург, ул. Академика Байкова 8

References

Supplementary files