MCP Joint Anatomy

The metacarpophalangeal joint is a condyloid (ellipsoid) joint permitting flexion, extension, abduction, adduction, and limited rotation. Key anatomical structures include the collateral ligaments (taut in flexion, lax in extension - critical for rehabilitation), accessory collateral ligaments, volar plate, and the dorsal extensor hood mechanism. In rheumatoid arthritis, synovitis leads to progressive destruction with stretching of the radial sagittal band, ulnar subluxation of the extensor tendons, and the characteristic ulnar drift deformity. The intrinsic muscles (interossei and lumbricals) contribute to deformity through their altered line of pull.

PIP Joint Anatomy

The proximal interphalangeal joint is a bicondylar hinge joint with primary motion in the sagittal plane (flexion-extension). Stability is provided by proper and accessory collateral ligaments, the volar plate, and the central slip of the extensor mechanism. The PIP joint withstands forces up to 3 times body weight during pinch grip. In osteoarthritis, marginal osteophytes (Bouchard nodes) form dorsally and laterally. In rheumatoid arthritis, progressive synovitis leads to boutonniere deformity (central slip attenuation, PIP flexion, DIP hyperextension) or swan neck deformity (PIP hyperextension, DIP flexion).

CMC Joint Anatomy

The thumb carpometacarpal joint is a saddle (sellar) joint between the trapezium and first metacarpal base, permitting opposition, flexion, extension, abduction, and adduction. The joint is stabilized by the anterior oblique (beak) ligament (most important for stability), dorsoradial ligament, posterior oblique ligament, and intermetacarpal ligament. Primary osteoarthritis preferentially affects this joint in postmenopausal women due to ligamentous laxity and repetitive loading. Pantrapezial arthritis extends to the scaphotrapezial and trapeziotrapezoid joints.

Indications for Small Joint Arthroplasty

MCP Arthroplasty:

• Rheumatoid arthritis with painful joint destruction and ulnar drift (primary indication)
• Post-traumatic arthritis with preserved bone stock
• Osteoarthritis (less common, generally good bone stock)
• Failed previous arthroplasty requiring revision

PIP Arthroplasty:

• Osteoarthritis with stiffness greater than 30 degrees flexion contracture (motion desired)
• Rheumatoid arthritis (more guarded outcomes than MCP)
• Post-traumatic arthritis
• Select cases of psoriatic arthritis with adequate bone stock

Thumb CMC Arthroplasty:

• Eaton Stage II-IV thumb CMC osteoarthritis refractory to conservative management
• Post-traumatic arthritis of first CMC
• Failed previous CMC surgery
• Pantrapezial arthritis (may require STT arthrodesis in addition)

Contraindications

Absolute Contraindications:

• Active infection (local or systemic)
• Absent or severely deficient extensor mechanism
• Severe bone loss precluding implant fixation
• Fixed deformity not correctable at surgery (consider arthrodesis)
• Non-functional hand (no reconstructive benefit)

Relative Contraindications:

• Young, high-demand manual laborers (consider arthrodesis)
• Index finger PIP (arthrodesis preferred for pinch stability)
• Severe soft tissue contractures
• Inadequately controlled inflammatory arthritis
• Non-compliant patient unable to follow postoperative protocol

Before committing to arthroplasty, confirm the correct diagnosis and joint. Several conditions mimic primary degenerative or rheumatoid joint destruction and change the operation entirely.

Implant-Related Complications

Silicone Implant Fracture:

• Incidence: 50-70% at 10-year follow-up
• Often asymptomatic due to maintained capsular integrity
• Clinical significance: Only treat if symptomatic (pain, instability, crepitus)
• Management: Observation if asymptomatic; revision arthroplasty or arthrodesis if symptomatic

Silicone Synovitis:

• Incidence: 5-10% of silicone arthroplasties
• Pathophysiology: Foreign body reaction to silicone particles
• Clinical features: Swelling, pain, osteolysis on radiographs, may mimic infection
• Management: Synovectomy with implant exchange or conversion to arthrodesis; titanium grommets may reduce wear particle generation

Implant Subsidence/Loosening:

• More common with anatomic designs (SRA, pyrocarbon) than silicone
• Risk factors: Poor bone quality, malalignment, high activity level
• Presents with progressive pain and loss of motion
• Management: Revision with bone grafting or conversion to arthrodesis

Deformity Recurrence

Recurrent Ulnar Drift (MCP):

• Results from inadequate soft tissue balancing at index surgery
• Progressive stretching of radial sagittal band repair
• Continued rheumatoid disease activity
• Prevention: Meticulous soft tissue technique, disease control
• Management: Revision soft tissue procedure or revision arthroplasty

Boutonniere or Swan Neck Recurrence (PIP):

• Central slip attenuation leads to boutonniere recurrence
• Lateral band subluxation causes swan neck
• May require extensor reconstruction or conversion to arthrodesis

Other Complications

Infection:

• Early: Wound infection, treat with antibiotics and wound care
• Deep/chronic: Implant removal, debridement, delayed reconstruction
• Rheumatoid patients at higher risk due to immunosuppression

Stiffness:

• Common, especially at PIP level
• Prevention: Early protected motion, compliant patient
• Treatment: Aggressive therapy; manipulation under anesthesia rarely helpful

Instability:

• Results from ligament insufficiency or bone loss
• May require revision with constrained implant or arthrodesis

MCP Arthroplasty Outcomes

Swanson Silicone (RA) - what the literature actually shows:

• Early gains: arc of motion improves (around 30 to 46 degrees) and ulnar drift and extensor lag correct substantially in the first year
• Deterioration with time: by 14 years arc falls back toward 36 degrees, extension deficit recurs to around 23 degrees, and ulnar drift recurs to a mean of 16 degrees (Goldfarb & Stern)
• Long-term satisfaction is modest - patients satisfied with only 38% of hands and 27% pain-free at 14 years in the Goldfarb series
• Implant survival: 63% at 17 years (failure = revision or radiographic fracture; Trail)
• Implant fracture: roughly 60-67% radiographically by long-term follow-up, but frequently clinically silent
• Despite this, prospective comparison with medical therapy alone shows surgery still improves patient-reported hand function and corrects deformity better than non-operative management (Chung, level II)

Predictors of Good Outcome:

• Rheumatoid arthritis (better than OA or post-traumatic)
• Adequate bone stock
• Good soft tissue quality
• Compliant with therapy protocol
• Well-controlled systemic disease

PIP Arthroplasty Outcomes

Silicone (RA and OA):

• Motion gain: Modest (average arc 40-50 degrees)
• Pain relief: 75-80%
• Stiffness more common than at MCP level

Surface Replacement / Pyrocarbon (OA):

• Outcomes are inconsistent and series-dependent; pain relief can be good but motion often does not improve
• In a single-surgeon pyrocarbon PIP series (Sweets & Stern), arc of motion actually FELL from 57 to 31 degrees, with frequent loosening, migration, dislocation and squeaking - the authors abandoned the implant
• Higher reoperation and loosening rate than silicone; best reserved for OA with intact collateral ligaments and good bone stock
• Counsel patients that motion preservation is not guaranteed and that arthrodesis is a reliable fallback

Thumb CMC Arthroplasty Outcomes

Trapeziectomy (with or without LRTI):

• Good pain relief in roughly 78% of patients in long-term RCT follow-up (Gangopadhyay), and higher in observational series
• Grip and pinch strength recover, although pinch may decline slowly over years irrespective of technique
• Subsidence (proximal metacarpal migration) is near-universal but correlates poorly with symptoms
• Return to function: 3-6 months (longer than digit arthroplasty)
• Total joint (dual-mobility) prostheses show faster early recovery in some series but lack the long-track-record durability data of trapeziectomy

1. Swanson AB. Flexible implant resection arthroplasty. Hand. 1972;4(2):119-134.

2. Goldfarb CA, Stern PJ. Metacarpophalangeal joint arthroplasty in rheumatoid arthritis. A long-term assessment. J Bone Joint Surg Am. 2003;85(10):1869-1878.

3. Trail IA, Martin JA, Nuttall D, Stanley JK. Seventeen-year survivorship analysis of silastic metacarpophalangeal joint replacement. J Bone Joint Surg Br. 2004;86(7):1002-1006.

4. Vermeulen GM, Slijper H, Feitz R, et al. Surgical management of primary thumb carpometacarpal osteoarthritis: a systematic review. J Hand Surg Am. 2011;36(1):157-169.

5. Gangopadhyay S, McKenna H, Burke FD, Davis TRC. Five- to 18-year follow-up for treatment of trapeziometacarpal osteoarthritis. J Hand Surg Am. 2012;37(3):411-417.

6. Sweets TM, Stern PJ. Pyrolytic carbon resurfacing arthroplasty for osteoarthritis of the proximal interphalangeal joint of the finger. J Bone Joint Surg Am. 2011;93(15):1417-1425.

7. Chung KC, Burns PB, Wilgis EFS, et al. A multicenter clinical trial in rheumatoid arthritis comparing silicone metacarpophalangeal joint arthroplasty with medical treatment. J Hand Surg Am. 2009;34(5):815-823.

8. Eaton RG, Glickel SZ. Trapeziometacarpal osteoarthritis. Staging as a rationale for treatment. Hand Clin. 1987;3(4):455-471.

9. Squitieri L, Chung KC, Hutton DW, et al. A 5-year cost-effectiveness analysis of silicone metacarpophalangeal arthroplasty in patients with rheumatoid arthritis. Plast Reconstr Surg. 2015;136(2):305-314.

10. Burton RI, Pellegrini VD Jr. Surgical management of basal joint arthritis of the thumb. Part II. Ligament reconstruction with tendon interposition arthroplasty. J Hand Surg Am. 1986;11(3):324-332.

Global Epidemiology

• Thumb CMC (trapeziometacarpal) osteoarthritis is the most common small-joint indication worldwide, with a strong female and post-menopausal predominance; radiographic basal-joint OA is found in roughly a third of post-menopausal women.
• Rheumatoid arthritis affects approximately 0.5-1% of adults globally. The classic severely deformed rheumatoid MCP hand requiring arthroplasty is becoming less common as early biologic and conventional DMARD therapy controls disease before joint destruction.
• Erosive/inflammatory hand OA and post-traumatic arthritis make up most remaining PIP and MCP arthroplasty caseload.

Side-by-Side Guidance

Registry and Evidence Notes

• Unlike hip and knee arthroplasty, small joint arthroplasty is poorly captured by national joint registries; most outcome data come from single-centre series and a small number of RCTs (Gangopadhyay; Chung). This limits implant-level comparative survivorship data.
• The consistent registry-independent message: trapeziectomy-based procedures are durable and additional ligament reconstruction adds morbidity without benefit; silicone MCP implants fracture frequently but the encapsulation arthroplasty continues to function.

High- vs Limited-Resource Practice Variation

• In well-resourced settings, certified hand therapists and dynamic splinting protocols are integral to MCP arthroplasty outcomes, and pyrocarbon or total joint implants are available at higher cost for selected motion-preserving indications.
• In limited-resource settings, arthrodesis and simple trapeziectomy are favoured because they are cheap, reliable, and require less specialised post-operative therapy and follow-up. The reduced dependence on hand-therapy infrastructure is a legitimate driver of procedure choice, not a compromise of standards.