MCP Joint Arthritis

Synovitis is the primary event. Chronic inflammation of the MCP synovium produces pannus, an invasive synovial tissue, which releases inflammatory cytokines (TNF-alpha, IL-1, IL-6) and degrades cartilage enzymatically through matrix metalloproteinases.

The capsule and ligaments stretch. Synovial hypertrophy distends the joint capsule. The radial collateral ligament stretches, which allows ulnar drift; the volar plate stretches proximally, which allows volar subluxation; and the sagittal bands attenuate, which allows the extensor tendon to displace.

Volar subluxation. The proximal phalanx subluxes volarly on the metacarpal head, producing a visible dorsal step-off at the MCP and loss of the normal joint contour. It worsens with grip, because the force vector of gripping pulls the phalanx volarly.

Ulnar drift. Radial collateral laxity allows ulnar deviation, and the ulnar intrinsics (ulnar lumbricals and interossei) pull the digits ulnarly. Radial deviation at the wrist compounds the drift at the MCP, the Z-collapse described below, and gravity and grip forces perpetuate it.

Extensor tendon displacement. With the sagittal bands attenuated, the extensor falls ulnarly into the valley between the metacarpal heads. There it acts as an ulnar deviator instead of a pure extensor, creating an extensor lag and perpetuating the drift.

Progression. The biomechanical imbalance worsens with hand use until the deformity becomes fixed by contracture, abnormal loading erodes the articular cartilage, and the end stage is a mutilating arthropathy.

The zig-zag (Z-collapse). MCP ulnar drift is the distal half of a collapse of the whole ray. Rheumatoid synovitis at the wrist produces carpal supination, ulnar translocation of the carpus and radial deviation of the metacarpals on the forearm. To keep the fingers pointing forward, and because the radially deviated metacarpals shift the line of pull of the long flexors and extensors, the MCPs compensate by deviating ulnarly: radial at the wrist, ulnar at the MCP, the same collapsing-chain principle that produces the swan-neck and boutonniere zig-zags at digit level.

Why the wrist matters to MCP surgery. A radially deviated, unstable wrist is a standing deforming force on the MCPs. Correct the MCPs with arthroplasty and soft-tissue rebalancing while leaving that force alone and the ulnar drift recurs, which is one of the commonest reasons a technically sound arthroplasty re-drifts. Reconstruction therefore runs proximal to distal: assess and, where needed, realign or stabilise the wrist first or concurrently (wrist arthrodesis or arthroplasty, distal ulna or DRUJ surgery, detailed in the rheumatoid wrist topic), then the MCPs, then the IP joints. The dorsally prominent caput ulnae that accompanies this collapse also threatens the extensor tendons with attrition rupture, a further reason to address the wrist (covered in the extensor-rupture and rheumatoid-wrist topics).

Nalebuff rheumatoid hand classification. The deformity patterns, and what each asks of the reconstruction:

Type I, the swan-neck with MCP flexion deformity, is the most common pattern requiring MCP arthroplasty.

Direct cartilage injury. An intra-articular fracture of the metacarpal head or proximal phalanx base with an articular step-off of more than 2 mm distributes load abnormally. Focal cartilage loss at the impact site becomes secondary degenerative change over months to years.

Chronic instability. A collateral ligament injury, acute or chronic, leads to recurrent MCP subluxation or dislocation; the abnormal kinematics wear the cartilage and the arthrosis progresses.

Stiffness. Prolonged immobilisation after an MCP injury produces adhesions and capsular contracture. Decreased joint motion impairs cartilage nutrition, and degenerative change follows from the stiffness itself.

Primary osteoarthritis. Idiopathic cartilage degeneration, repetitive microtrauma in manual labourers, and a genetic predisposition that is rare in the MCPs compared with the DIP, PIP and first CMC joints. It progresses through cartilage loss, subchondral sclerosis and osteophyte formation. It is rare here because the MCP is a mobile joint under less focal stress than the DIP and PIP, and the thumb base is a much more common site for primary OA.

The rheumatoid history. Bilateral, symmetric hand pain and stiffness, with morning stiffness of more than an hour that improves with activity, progressive ulnar drift and visible deformity, and difficulty with both power grip (holding objects) and precision pinch. Ask about the known diagnosis and its systemic involvement (other joints, lungs, heart), the DMARD history (methotrexate, biologics), and how long the hand has been symptomatic, which is usually months to years.

The post-traumatic history. A fracture, dislocation or ligament injury of the MCP, followed after a delay of months to years by unilateral, single-digit pain and stiffness, reduced motion compared with the other side, and pain on gripping.

The osteoarthritic history. Insidious onset and gradual progression, usually in a patient over 60, often with an occupational history of manual labour or repetitive gripping, and with fewer systemic symptoms than rheumatoid disease.

Inspection. What to look for, and what each finding means:

• Ulnar drift of the fingers at the MCPs, pathognomonic for rheumatoid disease
• Volar subluxation, the proximal phalanx displaced volarly with a dorsal step-off at the MCP
• Boggy synovitis at the MCP joints in active disease, with fusiform swelling
• Swan-neck (MCP flexion, PIP hyperextension, DIP flexion) or boutonniere deformity at the IP joints
• Extensor tendons displaced ulnarly into the valleys between the metacarpal heads
• Skin: rheumatoid nodules on the extensor surfaces, olecranon and MCPs, with thinning and fragility
• Z-collapse, wrist radial deviation with MCP ulnar drift

Palpation. Joint-line tenderness is felt dorsally, and synovial thickening is boggy, compressible and warm when inflammation is active. Stress the collaterals radially and ulnarly with the joint in flexion, where they are normally tight, and in extension, where they are normally lax: excessive laxity means the ligament has attenuated. Test the volar plate for hyperextension laxity.

Motion. Active MCP flexion-extension is normally 0-90 degrees and is reduced in arthritis. Compare passive with active range to separate capsular tightness from extensor lag, the active extension deficit relative to passive extension that signals extensor tendon pathology (displacement or weakness), and compare with the other hand.

Special tests. The intrinsic tightness test: with the MCP extended, attempt PIP flexion; if the intrinsics are tight PIP flexion is limited, and it should improve with the MCP flexed, which relaxes them. Grip strength is measured by dynamometer against the other side and age-matched norms; key pinch and pulp pinch strength assess thumb MCP stability.

Function. Power grip (holding objects, opening jars), precision pinch (writing, buttoning), the activities of daily living (dressing, eating, hygiene) and the demands of work, manual or sedentary. These findings guide surgical planning and set the patient's expectations.

Radiographs. Plain films are the primary imaging for diagnosis and surgical planning:

• PA hand: joint space, erosions, ulnar drift
• Lateral hand: volar subluxation of the proximal phalanx
• Oblique views: additional detail of the MCP joint surfaces
• Bilateral hands: rheumatoid disease is bilateral and symmetric, so compare

Rheumatoid progression on radiographs. Early disease shows periarticular (juxta-articular) osteopenia and fusiform soft-tissue swelling with the joint space maintained and no erosions. Moderate disease shows joint-space narrowing of less than 50%, marginal erosions at the bare areas not covered by cartilage, subchondral cysts, volar subluxation of the proximal phalanx on the lateral view and ulnar deviation on the PA. Late disease shows narrowing of more than 50% or complete loss of joint space, large central and marginal erosions, volar and ulnar subluxation, metacarpal head destruction, ankylosis (rare, usually fibrous) and mutilating arthropathy, the opera-glass hand with telescoping digits.

Larsen radiographic grading (rheumatoid MCP):

Grades III-V typically require surgery if the joint is symptomatic and medical management has failed.

Post-traumatic findings. Joint-space narrowing that is usually focal and asymmetric, subchondral sclerosis and cysts, osteophytes (a dorsal MCP prominence) and the post-traumatic deformity itself, malunion or articular step-off, usually in one digit of one hand.

MRI is not routine, since plain films suffice for most cases. It is asked for to assess the extent of synovitis, erosions not visible on radiographs, tendon integrity, or to rule out an occult fracture. It shows synovial enhancement in active inflammation, erosions as T1-dark bone destruction, marrow oedema as T2-bright pre-erosive change, and tendon rupture or displacement.

Ultrasound assesses synovial thickening, with power Doppler signal marking active inflammation to guide injection or medical therapy. It is dynamic, real-time and cheaper than MRI, and shows synovial hypertrophy, effusion, Doppler signal and erosions. Its place is rheumatology follow-up rather than routine orthopaedic assessment.

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Rheumatoid serology. Rheumatoid factor, an IgM antibody against the Fc portion of IgG, is positive in 70-80% of rheumatoid patients but is not specific: it is also positive in hepatitis C, cryoglobulinaemia and the elderly. Anti-CCP antibodies are positive in 70% and are the more specific test, with specificity above 95%, and they are prognostic, predicting erosive disease.

Markers of activity. ESR rises with active inflammation and guides DMARD therapy; CRP is more specific than ESR for acute inflammation and tracks disease activity. ANA may be positive in 20-30% of rheumatoid patients, and should raise the question of an overlap syndrome (SLE, Sjogren). The blood count shows the normocytic, normochromic anaemia of chronic disease and thrombocytosis when inflammation is active.

Seronegative spondyloarthropathy. RF and anti-CCP are negative, which is what seronegative means. HLA-B27 is positive in 90% of ankylosing spondylitis, 60-80% of reactive arthritis and 20% of psoriatic arthritis; ESR and CRP may be raised; the diagnosis is clinical, on psoriasis of skin and nails, axial involvement and DIP joint arthritis.

Psoriatic arthritis. Seronegative for RF and anti-CCP, with ESR and CRP possibly raised. The diagnosis is clinical: psoriasis, nail pitting and oil spots, DIP and MCP involvement, sausage digits. Radiographs show the pencil-in-cup deformity at the DIP, erosions and osteolysis.

Crystalline arthropathy. Serum uric acid is raised in gout (more than 6.8 mg/dL) but may be normal during an acute attack, so aspirate the joint. Gout shows negatively birefringent needle-shaped monosodium urate crystals, yellow when parallel to the polariser; pseudogout shows positively birefringent rhomboid calcium pyrophosphate crystals, blue when parallel. The fluid is inflammatory, with a white cell count above 2,000 and often above 50,000 in an acute attack. Radiographs show chondrocalcinosis in CPPD and tophi, soft-tissue masses, in gout.

Before surgery. A blood count and comprehensive metabolic panel as baseline, ESR and CRP to gauge disease activity (defer surgery in an active flare), and albumin and prealbumin for wound healing. Perioperative DMARD management is decided with rheumatology: methotrexate is continued through surgery in most cases, and biologics are held according to their half-life. Laboratory tests confirm the diagnosis and guide medical management; imaging and examination determine surgical candidacy.

Disease-modifying therapy is first-line for rheumatoid MCP arthritis, and surgery is reserved for the patient whose symptoms and functional impairment persist after it has failed. Methotrexate is the anchor; the rest are alternatives or additions.

Triple therapy, methotrexate with sulfasalazine and hydroxychloroquine, is used for moderate-to-severe disease and is as effective as some biologics.

Biologic and targeted DMARDs are indicated for moderate-to-severe disease uncontrolled on methotrexate monotherapy, high disease activity, or erosive disease:

Around surgery. Hold an anti-TNF agent for 1-2 half-lives before the operation (adalimumab, for example, for 2-4 weeks) and restart it once the wound has healed, 2 weeks after surgery. The decision is made jointly with rheumatology.

NSAIDs give symptomatic relief of pain and stiffness by inhibiting cyclooxygenase and prostaglandin synthesis, and do not modify disease progression. Ibuprofen 400-800 mg three times daily, naproxen 500 mg twice daily or celecoxib 200 mg once or twice daily; the risks are GI bleeding (co-prescribe a PPI if the risk is high), renal impairment and cardiovascular events, especially with COX-2 inhibitors, so monitor renal function and the blood count.

Corticosteroids. Low-dose oral prednisone, 5-10 mg daily, covers acute flares and bridges the 8-12 weeks a DMARD takes to work. Long-term use is minimised because of osteoporosis, infection, glucose intolerance and Cushing syndrome, and the dose is tapered gradually once the DMARD is effective.

Corticosteroid injection is for active synovitis with pain and swelling or an MCP effusion, when oral medication has failed with DMARDs optimised, for temporary relief while a DMARD takes effect, or when the patient refuses or cannot tolerate surgery. It is contraindicated in active infection or overlying cellulitis, and relatively so in coagulopathy.

Technique. A dorsal approach between the extensor tendon and the collateral ligament, with a 25-27 gauge, 1 inch needle, after alcohol preparation and a no-touch technique.

• Triamcinolone acetonide 20 mg (0.5-1 ml), methylprednisolone 20-40 mg (0.5-1 ml), or betamethasone 3-6 mg
• Optional lidocaine 1% (0.5 ml): immediate relief confirms intra-articular placement
• Afterwards: rest the hand for 24-48 hours, ice for 15 minutes to reduce post-injection flare, no heavy gripping for a week

What it achieves. Pain relief in 50-70% of patients, lasting 3-6 months, less than in larger joints like the knee and shoulder. The risks are cartilage damage, which is why injections are limited to three a year; tendon weakening or rupture if the extensor is injected; infection, rare at less than 1 in 10,000 with strict asepsis; subcutaneous fat atrophy and skin depigmentation from a superficial injection; and hyperglycaemia in diabetics, whose glucose should be monitored.

Splints. Each has a specific job; the drift orthosis does not reverse deformity:

• MCP ulnar drift orthosis: custom-moulded thermoplastic or prefabricated, holding the MCPs at 0 degrees of radial-ulnar deviation, worn during activities such as gripping and writing or at night, for years. It slows progression and does not reverse the drift
• Resting hand splint: a full hand splint in the intrinsic-plus position, wrist 20-30 degrees extension, MCPs 30-45 degrees flexion, IPs extended, worn at night during acute painful flares and removed by day for function. It reduces pain and prevents deformity while the joint is inflamed
• Dynamic extension splint: the post-operative outrigger after silicone arthroplasty, described with the operation

Splinting is adjunctive, not curative; the primary management is medical.

Joint protection. The therapist's aims are to preserve motion and strength, protect the joints from deforming forces, improve function in daily living and teach the patient to protect the joints. The principles are to avoid ulnar-deviating forces (jar openers, twisting with radial deviation rather than ulnar), to use larger joints (bags carried on the forearm, doors pushed with the body), to reduce grip force with built-up utensils and adaptive equipment, to rest during flares, and to set up the workstation, keyboard and mouse properly.

Exercise. Active MCP flexion-extension (fist-making and finger extension) and gentle passive stretching, daily in multiple sessions of 10 repetitions, without aggressive stretching, which can worsen inflammation. Strengthening uses soft-to-medium therapy putty and foam-ball squeezes, avoiding heavy resistance in active disease because it worsens synovitis, and progresses once the DMARD has controlled the inflammation.

Equipment and training. Built-up handles on forks, spoons and pens; key turners; jar openers; button hooks and zipper pulls; electric can openers to cut repetitive gripping. Functional training rehearses dressing, eating and hygiene with the equipment, simulates work tasks, and teaches pacing and rest breaks. Hand therapy is essential non-operative care, and after arthroplasty it is critical to the result, because the therapist fabricates and supervises the dynamic splint.

What the implant is. Alfred Swanson introduced silicone MCP arthroplasty in the 1960s-1970s and it revolutionised rheumatoid hand surgery. The implant is a flexible spacer, not a load-bearing hinge, and not a true joint replacement: it maintains the joint space, allows motion through flexion of the elastomer itself, and derives its stability from the fibrous capsule that forms around it (encapsulation). It cannot withstand high compressive loads, which is why it is contraindicated at the thumb MCP.

Indications.

• Rheumatoid MCP arthritis with ulnar drift and/or volar subluxation
• Post-traumatic MCP arthritis of digits 2-5
• Failed conservative management (DMARDs, splinting, injections for more than 3-6 months)
• A wish to preserve motion rather than fuse
• Larsen grade III-V radiographic change
• Functional impairment: difficulty with grip and daily living

Contraindications. Active infection is absolute. The others are inadequate soft-tissue cover (exposed bone, compromised skin), severe bone loss with insufficient stock for the stems, the thumb MCP (arthrodesis is preferred), an active rheumatoid flare (defer until controlled), and the patient who will not adhere to the post-operative splinting protocol.

Implants. The Swanson implant is the original design, a hinge with stems; the Sutter is similar; the NeuFlex is a newer silicone design reinforced with titanium grommets. Silicone is the standard. Pyrocarbon surface replacement is not silicone, requires intact bone stock, has a higher revision rate and is not standard.

Spacer versus surface replacement. Pyrocarbon and metal-on-polyethylene implants are unconstrained surface replacements that resurface the metacarpal head and phalangeal base and depend on the patient's own collateral ligaments and bone to stay reduced, whereas silicone generates its own fibrous-capsule stability. Because they need competent ligaments and good bone stock, surface replacements suit primary OA or post-traumatic MCP arthritis with intact ligaments, preserved bone and minimal deformity in a younger, higher-demand patient who wants to preserve more motion, and not the deformed, ligament-deficient, osteopenic rheumatoid MCP, where nothing is left to hold an unconstrained implant reduced. Pyrocarbon's elastic modulus is close to cortical bone, which limits stress shielding, and it is biocompatible, but it demands precise sizing and seating. Surface replacements carry higher rates of squeak, migration or subsidence, dislocation or instability and reoperation, and the comparative evidence (Srnec, Wagner and Rizzo) shows no survivorship advantage over silicone at the MCP, so silicone stays the standard for the rheumatoid MCP and pyrocarbon is reserved for selected non-rheumatoid joints.

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Planning. Bilateral hand radiographs (PA, lateral, oblique) to assess bone stock, the degree of erosion and metacarpal head destruction, and to template the implant size. Coordinate DMARD management with rheumatology, control active synovitis before operating, and make sure the patient understands the commitment to 6 weeks of full-time splinting afterwards.

Set-up and exposure. Supine, the arm on a radiolucent hand table, an upper-arm pneumatic tourniquet at 250 mmHg after exsanguination with an Esmarch or by elevation. A longitudinal dorsal incision of 3-4 cm centred over the MCP; for several joints, one longitudinal incision from index to small or separate incisions for each digit, without excessive undermining, to preserve venous drainage.

1. Subcutaneous dissection preserving the dorsal veins and cutaneous nerves
2. Identify the extensor digitorum communis tendon overlying the joint
3. Develop the plane between the extensor and the joint capsule
4. Elevate the extensor mechanism radially, preserving the sagittal bands if intact or raising them as a flap if ruptured
5. Longitudinal capsulotomy to expose the joint

Synovectomy in the rheumatoid joint is complete: all hypertrophic, inflamed synovium is removed with rongeur, curette or electrocautery, and as much pannus as possible, because that reduces recurrent synovitis.

Bone preparation.

1. Resect the metacarpal head with an oscillating saw, perpendicular to the shaft and not angled, taking minimal bone (approximately 5-10 mm) to preserve length; remove osteophytes and smooth the edges
2. Ream the metacarpal and proximal phalanx canals with hand reamers or a burr to a snug fit for the stems, without over-reaming
3. Insert a trial and assess the fit, which should be snug rather than loose
4. Select the definitive size to match the trial
5. Insert the silicone implant, stems into both canals

Sizing is the trade the surgeon makes at this point: an implant that is too large over-stuffs the joint and causes stiffness and implant fracture; one that is too small lets the deformity recur.

Soft-tissue balancing. The extensor tendon has displaced ulnarly into the valley and is acting as an ulnar deviator, so it is repositioned over the centre of the MCP and sutured to the radial capsule with 3-0 non-absorbable suture (Ethibond, Ti-Cron); if the radial sagittal band has ruptured, it is reconstructed instead. The stretched, incompetent radial collateral ligament is reefed (plicated), or reconstructed by suturing the radial capsule to the radial side of the metacarpal neck, to tighten the radial structures against ulnar drift. If the intrinsic tightness test is positive, the ulnar interosseous is released from the ulnar side of the proximal phalanx, preserving the radial intrinsics that counteract the drift. Crossed intrinsic transfer, moving the ulnar lateral band to the radial side to create an active radial deviating force, is reserved for severe recurrent ulnar drift despite ligament reconstruction and is rarely performed.

Closure. Capsule over the implant with 2-0 absorbable (Vicryl), the extensor confirmed centralised and the sagittal bands closed if opened, subcutaneous 3-0 absorbable, skin 4-0 or 5-0 nylon, running or interrupted. Non-adherent dressing (Xeroform) and gauze, and the dynamic MCP extension splint applied immediately.

The dynamic extension splint. An outrigger custom-fabricated by a certified hand therapist, wrist in 20-30 degrees of extension, MCPs at 0 degrees with radial deviation, elastic bands pulling the MCPs into extension and radial deviation. It allows controlled passive flexion and blocks ulnar deviation. It is worn full-time (23 hours a day, off for hygiene only) for weeks 0-6, at night only for weeks 6-12, and at night as needed from months 3-6. Patient compliance with it is key to preventing recurrent ulnar drift.

Rehabilitation.

• Day 1-2: passive motion in the splint, flexion allowed and extension assisted by the bands
• Week 1: hand therapy begins with therapist-guided passive motion
• Weeks 2-6: progressive passive motion and gentle active motion within the splint
• Week 6: splint off by day; active motion begins
• Weeks 6-12: progressive active motion and gentle resisted strengthening
• Week 12: full strengthening, power grip and resistance training

What to expect. A 30-40 degree MCP flexion arc (0-40 degrees is typical), which is not the normal 0-90 but is enough for most daily activities and grip. With balanced soft tissue, 80-85% maintain the correction of ulnar drift and 85-90% maintain the reduction of volar subluxation. Pain improves significantly in 80-90%, because the operation removes painful synovium, stabilises the joint and improves alignment, and 85-90% are satisfied with pain relief and alignment. Counsel that this is a spacer, not a normal joint, and that motion is limited.

Survivorship. 80-90% of implants are in place and functioning at 10 years and 60-70% at 15 years; the failure modes are implant fracture, subsidence and recurrent deformity, detailed under Complications, and squeaking from silicone friction is an occasional complaint, a dissatisfaction rather than a mechanical failure. Read the 10-year figure against the long-term evidence on this page: at a mean of 14 years Goldfarb and Stern found 63% of implants fractured, ulnar drift recurring to 16 degrees and only 38% of hands rated satisfactory, though fracture is often well tolerated and, at 5 years, Squitieri and Chung found the patient-reported gains maintained.

Indications. Thumb MCP arthritis, post-traumatic or rheumatoid, where fusion is preferred over arthroplasty; post-traumatic arthritis with bone loss too severe for arthroplasty stems; failed MCP arthroplasty (implant fracture, subsidence, infection); the young, high-demand patient in manual work with high grip forces; severe MCP instability from collateral incompetence; and the patient who prefers stability to motion.

Contraindications. Stiff or fused IP joints, which need MCP motion to compensate; bilateral multiple-digit fusion, which would eliminate grip; and the index to small fingers of a low-demand patient, where arthroplasty is preferred.

Why the thumb is fused. The thumb MCP needs stability for lateral key pinch and pulp pinch, and the loads during pinch are high, 5-10 times pinch force. Arthroplasty there risks instability, recurrent pain and implant failure, whereas fusion gives pain-free, stable pinch and is the gold standard for the thumb MCP.

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Fusion position. The ulnar digits are fused progressively more flexed, mimicking the normal cascade so that every digit reaches the palm in grip. Rotation is neutral, the digit pointing toward the scaphoid when flexed, and the position is confirmed before fixation by testing pinch for the thumb or grip for the fingers with the trial position held.

Exposure (thumb). Supine on a hand table with an upper-arm tourniquet at 250 mmHg. A dorsal longitudinal incision of 3-4 cm centred over the thumb MCP joint line; preserve the dorsal veins, identify EPL radial to the incision and retract it radially, and open the capsule longitudinally on the ulnar side of EPL to expose the joint. In the rheumatoid joint, a complete synovectomy if synovitis is present.

Joint preparation.

1. Resect the articular cartilage of the metacarpal head with saw or rongeur down to subchondral bone, and remove the cartilage from the base of the proximal phalanx
2. Shape the surfaces, either cup-and-cone (metacarpal head conical, phalanx base concave, maximising contact) or flat perpendicular cuts on both sides, simpler and adequate
3. Decorticate with burr or curette to bleeding bone, which promotes fusion
4. Trial the position: 10-15 degrees of flexion, neutral rotation with the thumb pad facing radially, and simulate key pinch and pulp pinch to confirm it
5. Provisional fixation with two or three crossed K-wires, 0.045 or 0.062 inch

Fixation. A dorsal locking plate, a 2.0 mm or 2.4 mm hand plate with two or three screws in the metacarpal and two or three in the proximal phalanx, is the preferred construct: it is the most rigid, has the highest fusion rate and allows the earliest IP joint motion. The plate is applied dorsally and the joint compressed where possible before the screws are locked. Read that alongside Lutsky's series in the evidence below: fully locked constructs specifically raised the rate of delayed union and non-union, and the authors do not recommend routine use of locked plates, so the construct should not be an all-locked-screw one. The alternatives:

• K-wires: two or three crossed 0.045 or 0.062 inch wires obliquely across the fusion site; simple and low profile, but less rigid, needing 6 weeks of immobilisation and later removal
• Headless compression screw (Herbert, Acutrak): a single lag screw from the metacarpal head into the proximal phalanx; low profile, compressive, no removal, but needs good bone quality
• Tension band wiring: a dorsal figure-of-8 wire with K-wires, rarely used for MCP fusion

Bone graft is usually unnecessary when bone contact is good; it is added for significant bone loss, poor bone quality or a revision fusion, from the iliac crest (cancellous) or the distal radius (local). Closure is capsule with 2-0 absorbable, subcutaneous 3-0 absorbable and skin 4-0 or 5-0 nylon, under a non-adherent dressing and a thumb spica splint that immobilises the wrist and thumb MCP and leaves the IP free.

After the operation. With a plate, a protective thumb spica splint for 2 weeks, then a removable splint with the MCP still held while thumb IP motion begins. With K-wires, a thumb spica cast for 6 weeks of rigid immobilisation until fusion, then the wires come out. At week 6 a radiograph assesses fusion: if fusing, the splint is discontinued and motion and strengthening progress; if not, immobilisation continues for 2-4 more weeks and the film is repeated. Grip and pinch strengthening progress from weeks 8-12.

Results. Union in 90-95% with plate fixation, radiographically at 8-12 weeks, with nonunion in 5-10% (risk factors: smoking, poor bone quality, rheumatoid disease). Pain relief is excellent, near-complete in 95% or more, because the painful arthritic motion is eliminated; the patient gains stable key and pulp pinch, keeps or improves grip strength on a stable thumb post, and accepts the loss of MCP motion, which the IP joint compensates for. Satisfaction is 90% or higher, and fusion is preferred over arthroplasty for the thumb. The complications are nonunion, malposition (too much or too little flexion, or malrotation, avoided by testing the position intra-operatively), dorsal hardware prominence (rare, removed if symptomatic), infection in less than 2%, and secondary IP joint stiffness treated with hand therapy.

A pre-DMARD operation. MCP synovectomy was performed in the pre-DMARD era to remove inflamed synovium and prevent joint destruction. It has been largely supplanted by DMARDs and biologics, which control synovitis systemically and more effectively, and is now rarely performed as an isolated procedure; it is occasionally combined with arthroplasty, where the synovium is removed during the joint replacement.

The rare indication. Early rheumatoid MCP arthritis, Larsen grade I-II, with persistent synovitis despite optimised DMARD therapy, before significant erosions or deformity, and as an isolated MCP synovitis rather than a systemic flare. It is contraindicated at Larsen III-V, where erosions and deformity need arthroplasty or arthrodesis; in an active systemic flare, where medical management is optimised instead; and where the DMARD has not been tried or has not been given long enough.

Technique. The dorsal approach used for arthroplasty, a longitudinal capsulotomy, and complete removal of hypertrophic inflamed synovium with rongeur and curette. Inspect the extensor tendons and centralise them if displaced, repair the radial collateral ligament if lax, release tight ulnar intrinsics, and close the capsule and skin. The hand is splinted in MCP extension and radial deviation for 2 weeks, then hand therapy for motion and strengthening.

What it achieves. Temporary relief, on average 3-5 years before the synovitis recurs, with pain improved in 70-80% in the short term. It does not reverse deformity, only slows its progression, and it does not prevent erosions in the long term.

How a failed arthroplasty presents. Return of pain points to implant fracture, subsidence or recurrent synovitis; loss of motion to stiffness from adhesions; recurrent ulnar drift or volar subluxation to inadequate balancing; crepitus or instability to a palpable implant fracture; and swelling with erythema to infection. PA and lateral radiographs show the break in the silicone, subsidence with loss of joint-space height as the implant sinks into bone (poor bone stock, over-reaming), bone resorption around the implant, and recurrent drift or subluxation.

Choosing the revision. The scenario decides the operation:

Revision arthroplasty.

1. Remove the fractured implant through the dorsal approach, which may be scarred, retrieving every fragment and curetting the fibrous capsule
2. Assess the metacarpal and phalangeal canals for resorption from subsidence: adequate bone allows revision arthroplasty, poor bone means arthrodesis
3. If the canals have enlarged, use a larger implant, without over-stuffing
4. Rebalance the soft tissue more aggressively than at the primary operation: extensor centralisation, tight reefing of the radial collateral and capsule, release of the ulnar intrinsics, and consider crossed intrinsic transfer of the ulnar lateral band to the radial side to resist drift actively
5. Dynamic splinting is even more critical than after a primary: 6 weeks full-time, then night splinting for 6 months

Revision outcomes are less predictable than primary surgery: a satisfactory result in 70-80% against 85-90% for a primary, with recurrent deformity in 20-30%. Counsel realistic expectations, and stress soft-tissue balancing and compliance with the splint.

Salvage arthrodesis is for the failed arthroplasty with poor bone stock, infection, or a patient who prefers stability. The implant and all fibrous tissue are removed, the metacarpal and phalanx prepared as for a primary fusion, bone graft (iliac crest or distal radius) often needed because of the bone loss, and a plate applied, in the cascading positions of a primary arthrodesis. Fusion is achieved in 80-90%, with excellent pain relief and a loss of motion the patient accepts.