Tendon rupture is a common complication of RA. Synovitis weakens the substance of tendons, and chronic erosive changes of the joints lead to bony prominences which might cause tendon attrition.

The extensor tendons to the small finger are most at risk due to the erosive synovitis at the dorsal distal radioulnar joint; over time, this will progress radially to finally affect all extensor tendons. Diagnosis of finger extensor tendon rupture requires a thorough physical examination for differential diagnosis with other conditions possible in RA patients. First, metacarpophalangeal (MCP) joint subluxation in ulnar drift hand must be excluded. In this case, the extensor tendon is dislocated, not ruptured. Therefore, patients can maintain their fingers extended once passively extended by an examiner. Secondly, synovitis at the elbow joint can cause a posterior interosseous nerve (PIN) palsy which will cause weakness of finger extension. This PIN palsy should be checked by means of a tenodesis test; passive flexion of the wrist will cause passive finger extension if the tendons are intact.

Extensor tendon ruptures can be reconstructed by tendon transfer, tendon grafting or end-to-side suturing of adjacent tendons (Figure 1). Primary end-to-end repair is not desirable because the ends of the tendon are frayed from inflammation and the proximal motor unit has already developed contractures. To prevent recurrent ruptures, the preexisting synovitis, osseous irritations, and dorsally subluxed ulnar head should be addressed in the way of debridement or formal Darrach or Sauvé-Kapandji (SK) procedures (Figure 2).

Flexor tendon ruptures are much less common than extensor tendon ruptures. Attritional damage from bony spurs at the thumb scaphotrapezial joint in advanced RA can be a cause [14]. Ruptures are frequently associated with compressive neuropathies, and initial presentation with trigger fingers is also frequently seen [15]. The most commonly involved flexor tendon is flexor pollicis longus (FPL), followed by flexor digitorum profundus to the index finger.

Surgical patient selection and counseling: An isolated extensor tendon rupture of the little finger may not result in significant functional limitation, but the patient should be advised to undergo surgery to prevent additional tendon ruptures and irreversible contracture of the intrinsic muscles due to flexed MCP posture. Patient satisfaction after surgical treatment for multiple tendon ruptures is lower than in cases with a single tendon rupture [16]. In multiple ruptures involving three or more extensor tendons, limitation of available donor muscles results in weak extension strength, and intrinsic muscle contracture can result in limited finger flexion [17]. The best treatment for tendon rupture may be prophylactic management such as extended tenosynovectomy to prevent further damage to the tendons. A number of reports have identified several risk factors associated with higher rates of tendon rupture, which are dorsal dislocation of the distal ulna, carpal collapse, presence of the scallop sign (an erosive change in the distal radioulnar joint) on X-rays, and swelling of the extensor compartments [18-20].

FPL rupture leads to significant functional disability of the thumb, which also necessitates surgical intervention. In RA patients with symptoms of carpal tunnel syndrome and impaired grasping function, flexor tenosynovectomy may be indicated not only to alleviate the symptoms, but also to prevent subsequent tendon ruptures.

Patients need to be informed that healing of the reconstructed tendons generally requires two to four months, and full recovery of strength and motion can take more than six months [21].

Distal radioulnar joint (DRUJ) arthritis is a common cause of ulnar wrist pain in RA. The joint is affected early in the disease causing painful forearm rotation, instability, and dorsal subluxation of the distal ulna. The prominent ulnar head abuts the carpus, leading to ulnocarpal impingement. Surgical options include resection of the distal ulna (the Darrach procedure) and the SK procedure (Figure 2). Long-term outcomes of Darrach resection show significant pain reduction and functional improvement [22,23]. However, there are some concerns such as increased instability of the wrist and potential ulnar translation of the carpus [24]. Alternatively, the SK procedure fuses the DRUJ to prevent ulnar translation of the carpus while also performing a proximal ulna ostectomy to maintain some rotatory function. Complications include instability of the proximal ulnar stump and nonunion of the fusion site [25]. Outcomes of the two procedures have been equally satisfactory in the rheumatoid population [26].

The extensor carpi ulnaris (ECU) tendon is one of the most frequently involved tendons in RA [27]. In some RA patients, synovial thickening of the ECU subsheath may lead to its destruction and eventual volar dislocation of the ECU proper. Findings have suggested that tenosynovitis of the ECU tendon can be a predictor of erosive progression in early RA [28]. Surgical options include simple ECU synovectomy, relocation of the tendon, and bony procedures if necessary.

The triangular fibrocartilage complex (TFCC), which is a load-bearing structure for the ulnocarpal joint and a primary stabilizer of the DRUJ, is progressively destroyed in RA. This situation can lead to instability, pain, and mechanical symptoms. With the trend toward milder disease activity due to improved medical therapies, patients with TFCC tears can benefit from arthroscopic synovectomy or repair of the TFCC, before any significant arthritic changes accompany.

Surgical patient selection and counseling: Surgical treatment for DRUJ arthritis should be recommended for patients with intractable pain, limitation of forearm rotation, or extensor tendon ruptures. The DRUJ procedures (Darrach or SK procedures, Figure 2) are an effective and rewarding surgery, and are less invasive compared to total arthrodesis or replacement arthroplasties of other large joints. The authors prefer a Darrach procedure in low-demand elderly patients while the SK procedure is selected for high-demand young patients with a risk of ulnar translocation of the carpus.

Common dorsal wrist problems are synovitis of extensor tendons and/or synovitis of the radiocarpal or midcarpal joints. Dorsal synovitis is generally more recognized than volar synovitis, because the dorsal synovium is placed more superficially. Synovitis of extensor tendons needs tenosynovectomy through an open incision, while synovitis limited to radiocarpal or midcarpal joints can be treated with arthroscopic synovectomy. Arthroscopic procedures can be simply performed for synovial biopsy, which aids in accurate diagnosis by exclusion of other chronic inflammatory disorders or infection.

Synovectomy of the joint is most appropriate when joint motion is still relatively well preserved [29]. On the other hand, advanced arthritis with severe joint destruction and instability can be treated with arthrodesis or arthroplasty. In patients with disease localized to the radiocarpal joint and progressive ulnar translocation of the carpus, limited wrist arthrodesis such as radiolunate or radioscapholunate arthrodesis has shown good outcomes at mid- and long-term follow-up [30,31]. Through the procedure, partial wrist motion and bone stock are preserved while disease progression is prohibited (Figure 3). There is an objective and subjective increase in grip strength while pain relief is also achieved [32]. Progression of arthritic changes at the midcarpal joint following partial wrist fusion is generally well tolerated [33]. Total wrist arthrodesis is the procedure of choice in advanced or diffuse arthritis of the wrist with severe pain, deformity, and poor soft tissue support, but the necessity of this procedure is decreasing. The obvious drawback to this procedure is loss of wrist motion. It is important that the patients understand this, although, in most situations, a pain-free and stable wrist can overweigh this drawback.

Total wrist arthroplasty is an alternative to arthrodesis and has the advantage of preserving wrist motion. Disadvantages lie in the durability and reliability of the implant. Systematic reviews comparing wrist arthrodesis with wrist arthroplasty in RA patients show that pain relief is achieved after both procedures, but with higher complication rates after arthroplasty than arthrodesis [34]. Stable wrists with preserved bone stock is a good indication for arthroplasty and good results can be expected even in the long-term [35,36]. When done successfully, patients prefer arthroplasty to arthrodesis because of improved ease of activities of daily living [37]. Further longer-term studies will be needed to better define the role of arthroplasty in the management of wrist RA.

Surgical patient selection and counseling: Extensor tenosynovectomy is recommended to prevent tendon ruptures, which is possible when synovitis persists for more than four to six months of medical therapies [20]. In some patients with synovitis of the wrist, systematic inflammation might be well controlled by medical treatment. For these patients, arthroscopic synovectomy can be helpful for debulking the synovitis and for maintaining the dose of current medical treatment [38]. The patients should be informed that synovectomy procedures are prophylactic and not curative; although the short-term benefits, such as pain relief and improved function, are fairly reliable, it does not correlate with long-term disease remission and retardation of joint destruction [39,40].

For the patient with persistent, debilitating pain and advanced wear of the radiocarpal joint, surgical options are relatively straightforward; either arthrodesis or arthroplasty.

The prognosis of RA often includes hand deformities, with ulnar drift being the most common. It is secondary to chronic proliferative synovitis of the MCP joints which causes attenuation of the radial collateral ligament and radial portion of the sagittal band of the extensor apparatus. The extensor tendons displace ulnarly, the proximal phalanges subluxate volarly and intrinsic contractures develop in a compensatory manner (Figure 4). Fine pinch is hampered and patients find it difficult to curl the fingers around large objects. Another very important concern for patients is the unappealing appearance; studies have shown that aesthetics along with function are major factors that influence patients’ decision to undergo surgery [41].

In early stage of the deformity, synovectomy of the MCP joint, coupled with extensor tendon centralization and a cross-intrinsic transfer, is a good surgical option to restore the normal position of the fingers (Figure 5, Supplementary Video 1 and 2). For patients with chronic MCP joint subluxation or joint destruction, soft tissue reconstruction alone may not correct the deformity, and arthroplasty is needed. MCP joint arthroplasty has been one of the most commonly performed surgical procedures on the hand for RA patients in the developed countries [42]. Constrained silicone implants have been used for decades and are still the most commonly used material for replacement of MCP joints destroyed by RA. These implants act as an interpositional spacer which help align the joint in proper position. According to a multicenter prospective cohort study, subjects who underwent silicone metacarpophalangeal joint arthroplasty showed better outcomes at seven-year follow-up in function, aesthetics and satisfaction, when compared to the medically managed group [43].

Surgical patient selection and counseling: Soft tissue reconstruction for ulnar drift hand can be performed with good functional and aesthetic outcomes and with less invasiveness. The procedure offers an opportunity to perform synovectomy and correct the ulnar drift deformity before progression of more severe skeletal damage. Deformity alone should not be an indication for recommending surgical treatment, but for some patients, aesthetics is the main concern and improving the appearance of the typical ulnar drift may be beneficial to the patient's self-regard. Similar to the synovectomy for the wrist joint, the patient should be reminded that soft tissue reconstruction is not curative, and recurrence can occur if medical treatment fails to control inflammation.

The proximal interphalangeal (PIP) joints and distal interphalangeal (DIP) joints are less commonly involved in RA. The two common digital deformities are swan-neck and boutonniere deformities.

Deformities that are flexible can be treated by conservative treatment using a figure-eight ring for swan-neck deformity and extension splinting for boutonniere deformity. Soft tissue reconstruction procedures include flexor digitorum superficialis tenodesis, reconstruction of the oblique retinacular ligament, and volar translocation of the lateral bands for swan-neck deformity [44-46], and reconstruction of the central slip and repositioning of the lateral bands dorsally for boutonniere deformity. For severe arthritic joints, arthrodesis or arthroplasty can be performed.

Surgical patient selection and counseling: Patients with swan-neck deformity can have functional problems as they are unable to make a full fist due to the hyperextended PIP joint. However, in patients with boutonniere deformity, their capacity to make a full fist is maintained, and the unappealing appearance of the finger is more of concern to the patient. In the authors’ experience, soft tissue reconstruction for swan-neck deformity can be helpful for patients’ hand function, but surgical correction of boutonniere deformity is difficult and may not fulfill patients’ expectation for cosmetic appearance.

The two most common thumb deformities in RA are also boutonniere deformity and swan-neck deformity. Boutonniere deformity of the thumb consists of flexed MCP joint and hyperextended interphalangeal (IP) joint. Progressive synovitis attenuates the dorsal capsule and causes volar and ulnar subluxation of the EPL tendon, which results in volar subluxation of the MCP joint. On the other hand, swan-neck deformity develops mainly due to synovitis and dorsoradial subluxation at the trapeziometacarpal (TMC) joint with resultant metacarpal adduction. Progressive adduction and flexion of the metacarpal results in secondary hyperextension of MCP joint and flexion of IP joint (Figure 6).

The thumb constitutes approximately 50% of hand function. Therefore, the most important part of rheumatoid hand surgery is to reconstruct the thumb to improve pinch and grip, appearance, and posture. In the authors’ experience, for severe boutonniere deformity with hyperextension or deviation of the IP joint, arthrodesis of the IP joint is a simple and effective solution. Severe deformity at TMC joint can also be managed with simple trapeziectomy (Figure 6).