Summary Metacarpophalangeal (MCP) Joint arthritis typically presents with pain, swelling, and limited motion. Inflammatory etiology is much more common than osteoarthritis Diagnosis is made with a combination of physical exam and radiographs which may demonstrate ulnar deviation of the digits with possible volar subluxation of the proximal phalanx on the metacarpal head Treatment occurs on a spectrum of non-operative and operative measures including observation, Disease-modifying antirheumatic drugs (DMARDs), silicone or pyrolytic carbon implants, and arthrodesis Epidemiology Incidence Less common than other joints of the hand DIPJ > Thumb CMC > PIPJ > MCPJ Prevalence primarily affects patients with pre-existing inflammatory arthropathies primary osteoarthritis (OA) is rare 6.1% in males 1.4% in females post-traumatic arthritis is rare Demographics more likely to occur in the 4th or 5th decade of life OA and post-traumatic arthritis more likely to occur in men at an earlier age inflammatory arthritis more frequently occurs in women Risk factors basic risk factors previous trauma intra-articular fractures dislocations advanced risk factors rheumatic or inflammatory disease Etiology Pathophysiology trauma intra-articular fractures without anatomic reduction leading to incongruent joint space rheumatoid and inflammatory arthritides joint destruction and cartilage loss cell biology rheumatoid arthritis (RA) egress of neutrophils which migrate to synovial fluid and produce proteases and reactive oxygen species causing cartilage destruction diffuse, polyarticular synovial hypertrophy that results in capsular and ligamentous laxity, degenerative arthritis, and tendon rupture Gout deposition of monosodium urate crystals triggers an increase in IL-1β and IL-1 receptor activation leading to transcription of pro-inflammatory cytokines driving joint destruction Calcium Pyrophosphate Deposition Disease (CPPD) deposition of calcium pyrophosphate within the synovium which up-regulates the inflammatory cascade Systemic Lupus Erythematosus (SLE) significant up-regulation of pro-inflammatory interferon-inducible genes which down-regulate extracellular matrix homeostasis leading to decreased tissue repair and increased cartilage destruction Hemochromatosis intra-articular iron deposition increases IL-1 receptor activity leading to up-regulation of the inflammatory cascade and subsequent joint destruction Anatomy Arthrology MCP joint consists of the proximal phalanx and the corresponding metacarpal diarthrodial joint convex head of the distal aspect of the metacarpal articulates with the concave proximal phalanx base MCP joint contributes 77% of the total arc of finger flexion, although most functional daily activities can be performed with 35° or 50% of the normal range of motion thumb MCP joint volar aspect of the joint capsule has 2 sesamoid bones larger range of motion in comparison to other MCP joints Ligament volar plate increases overall joint congruence and prevents MCP joint hyperextension volar accessory ligament attaches on the middle of the metacarpal head and extends to the volar plate and deep transverse metacarpal ligament, which tightens during finger extension deep transverse metacarpal ligament connects the 2nd to 5th metacarpal heads together at the volar plate function to increase joint stability and aid in joint dynamics radial and ulnar collateral ligaments accessory component provides radial and ulnar stability with the digit in extension proper component provides radial and ulnar stability with the digit in 30 degrees of flexion Tendons volar digits 2-5 MCP joint receive support from flexor digitorum superficialis (FDS), flexor digitorum profundus (FDP), lumbricals, interossei, flexor digiti minimi (FDM) thumb MCP joint receives support from flexor pollicis longus (FPL), and flexor pollicis brevis (FPB) dorsal digits 2-5 MCP joint are reinforced by the extensor digitorum communis (EDC), extensor indicis (EIP), extensor digiti minimi (EDM) thumb MCP joint is reinforced by extensor pollicis longus (EPL), abductor pollicis brevis (APB), adductor pollicis and extensor pollicis brevis (EPB) adductor pollicis inserts on ulnar sesamoid FPB inserts on radial sesamoid Classification Larsen Radiographic Scale for Grading Joint Involvement in RA Grade 0 no change Grade I slight changes, including periarticular swelling Grade II erosions, with definitive joint-space narrowing Grade III medium destructive changes with erosions and joint spaces poorly defined Grade IV severe destructive changes and collapse with significant erosions Grade V mutilating changes, original articulating surfaces have disappeared, and there is gross bony deformation Presentation History prior trauma past medical history of rheumatic disease or inflammatory arthritides Symptoms common symptoms of OA pain deformity common symptoms of inflammatory arthritis intermittent inflammatory episodes waxing and waning clinical course other joint involvement Physical exam inspection erythema gout or CPPD deformity RA can result in ulnar deviation of digits at the MCP joint ulnar deviation can also be secondary to proximal malalignment, such as radial deviation of the wrist inflammatory arthritis leads to MCP joint synovitis which attenuates the dorsal capsule and extensor mechanism, resulting in volar translation of the proximal phalanx isolated laxity of the volar MCP joint capsule leads to progressive pull of the intrinsic and extrinsic musculature resulting in a swan neck deformity thumb deformity observed in inflammatory arthritis EPL tendon is displaced ulnarly and volarly, which leads to the inability to actively extend the MCP joint flexion at the MCP joint with coinciding IP hyperextension leads to a Boutonniere deformity aberrant pull of both the EPL and intrinsics results in interphalangeal joint hyperextension 90/90 deformity can result progressive adduction and flexion of the metacarpal then results in secondary hyperextension and volar plate laxity at the MCP joint gamekeeper's deformity is a result of synovitic attrition of the UCL with this laxity comes radial deviation of the proximal phalanx and secondary adduction of the metacarpal a first web space contracture can develop gout periarticular tophi Imaging Radiographs recommended views AP, lateral and oblique of hand findings basic abnormal findings OA joint space narrowing, osteophytes, subchondral sclerosis, subchondral cysts advanced abnormal findings RA substantial bone loss of the dorsal base of the proximal phalanx gout punched-out or "rat-bite" erosions with overhanging edges and sclerotic margins SLE deforming nonerosive arthropathy Jaccoud’s arthropathy (JA) erosive arthropathy also referred to as rhupus hemochromatosis symmetrical loss of joint space, subchondral cysts close association with CPPD characteristic hook-like osteophytes projecting from radial ends of 2nd and 3rd metacarpals CPPD more extensive involvement from the 2nd to the 5th MCP and radial hook-like osteophytes Studies Labs RA RF Anti-cyclic citrullinated peptide antibody (anti-CCP) SLE Antinuclear antibody (ANA) hemochromatosis serum transferrin saturation, serum ferritin Invasive studies synovial aspiration Gout monosodium urate (MSU) crystals thin, tapered, needle-shaped intracellular crystals yellow when aligned parallel to red compensator blue when aligned across the direction of polarization strongly negatively birefringent CPPD rhomboid-shaped crystals weakly positively birefringent Diagnosis confirmed by history, physical exam and radiographs Treatment Nonoperative observation, NSAIDs, DMARDs, splinting, corticosteroid injections indications first line of treatment for mild symptoms outcomes inconclusive evidence to suggest that pain or functional improvement is predictable in patients with RA Operative arthrodesis of thumb MCP joint indication persistent symptoms, synovitis, or swelling despite a 3- to 6-month course of nonsurgical interventions techniques Kirschner wire (K-wire), tension band, plate, intramedullary screw outcomes K-wire fixation 83-100% fusion rate high incidence of reported decreased pinch strength, thumb opposition, interphalangeal joint flexion, and overall dexterity tension banding lower rates of infection, nonunion, and revision surgery when compared to k-wire fixation overall success rate of 95% plate fixation time to union of 11.8 weeks on average at 1 year follow-up, no instances of broken implants, symptomatic implants, or infection intramedullary screw fixation mean fusion angle of 18 degrees 96% of patients report adequate pain relief and return to work time to union averaged 10 weeks arthrodesis of finger MCP joint indication persistent symptoms, synovitis, or swelling despite a 3 to 6-month course of nonsurgical interventions index finger: higher demand patients, younger patients with significant joint instability overall, finger MCP joint arthroplasty is preferred to arthrodesis in ordered to preserve motion techniques index finger plate fixation tension band fixation outcomes index finger 84.6% union rate at 11.6 weeks arthroplasty of thumb MCP joint indication MCP arthroplasty in OA or posttraumatic arthritis is limited, specific indications have not been well-established patients with RA and painful deformity with destruction or subluxation of the joint and fixed deformity that cannot be corrected with soft-tissue reconstruction alone techniques silicone implants pyrolytic carbon (pyrocarbon) implants outcomes postoperative function appears to improve in appropriately selected patients not likely to achieve full range of motion of the MCP joint primary survivorship of silastic implants was 83% at mean follow-up of 5.8 years reliable reduction in pain arthroplasty of finger MCP Joint indications allows for the preservation of some degree of flexion-extension and abduction-adduction arthroplasty is favored over arthrodesis for arthritis of the index through small finger MCP joints techniques silicone implants pyrocarbon implants contraindicated in the setting of collateral ligament insufficiency metal-plastic surface replacement arthroplasty (SRA) implants outcomes silicone arthroplasty Patients reliably report markedly improved pain and motion after silicone arthroplasty, and long-term survival from revision surgery has been reported from 63% to 97% pyrocarbon arthroplasty Ten and 16-year survivorship in patients with RA has been reported at 81% and 70% osteoarthritis has resulted in better survivorship at 10 years compared with inflammatory arthritis metal-plastic SRA implants in RA, notable improvements in pain relief, grip strength, and range of motion at an average follow-up of 9.5 years in RA 10 and 20-year survivorship was 95% and 85% noninflammatory arthritis treated with SRA implants demonstrated improvements in pain and function, but overall satisfaction was 72% in noninflammatory arthritis, 10-year survivorship was 76% in patients with a substantial extensor lag or ulnar deviation, the arc of motion may be only minimally increased key and tip pinch also improve because the index finger is brought over into radial position reported mean postoperative range of motion arcs vary from 27° to 60° extension lags also vary, from 9° to 22° a loss of approximately 12° of active motion from an early postoperative arc of motion of 51° has been documented at a mean follow-up of 63 months Techniques Nonoperative observation, NSAIDs, DMARDs, splinting, corticosteroid injections technique NSAIDs OA or inflammatory arthritis in patients without gastrointestinal, or renal compromise topical anti-inflammatories can be used in patients with gastrointestinal or renal compromise as there is limited systemic absorption DMARDs examples: oral corticosteroids, Methotrexate, Azathioprine, Sulfasalazine, Tacrolimus and Leflunomide commonly co-managed by rheumatologist common medications that may be continued without change through the perioperative period include Methotrexate and Sulfasalazine Cyclosporine and Tacrolimus may be continued in cases where symptoms are severe biologic DMARDs should be discontinued, and surgery should be scheduled at the end of the dosing cycle intra-articular corticosteroid injections conservative treatment option for the treatment of osteoarthritis and RA well-tolerated but effects are frequently temporary static and dynamic splinting load sharing and help relieve pain by immobilizing the joint thumb MCP joint resting splints can be lower profile and less limiting than most splints for the fingers MCP joint blocking intrinsic-plus splinting combined with dexterity exercises improved range of motion, strength, pain, and dexterity pros/cons patients on DMARDs have higher risks of infection and delayed wound healing which can be avoided with nonoperative management long term NSAID use can lead to renal and gastrointestinal pathology Arthrodesis of thumb MCP joint indications persistent symptoms, synovitis, or swelling despite a 3- to 6-month course of nonsurgical interventions maintained motion at carpometacarpal (CMC) and interphalangeal (IP) joints majority of thumb mobility stems from CMC thumb MCP joint approach dorsal incision, exploiting extensor interval longitudinally gain access to dorsal capsule technique denude all diseased cartilage preparation of the remaining subchondral bone with cup and cone reamers the optimal biomechanical position is 20-25 degrees of flexion and 15° of pronation k-wire fixation utilization of chevron osteotomy with k-wires positioned orthogonally to fusion position tension banding plate fixation joint is positioned in 10° to 15° of flexion and a k-wire is introduced retrograde for provisional reduction while the plate is applied two screws with washers are placed diagonally across the joint while under compression intramedullary screw fixation osteotomy is performed with the goal of placing the thumb in 20° of flexion guidewire is placed for provisional fixation followed by the cannulated screw in the case of advanced trapeziometacarpal (TMC) disease, increasing the flexion angle to 20° to 40° may offload the TMC by decreasing the amount of motion required for thumb opposition patient is typically immobilized for 4-6 weeks or until radiographic union occurs complications k-wire overall 16.7% complication rate nonunions and EPL ruptures with the latter secondary to suboptimal K-wire placement intramedullary screw metacarpal head fracture screw cut-out dorsal cortex perforation all surgical modalities infection, nonunion, revision surgery Arthrodesis of finger MCP joint indications persistent symptoms, synovitis, or swelling despite a 3 to 6-month course of nonsurgical interventions approach longitudinal dorsal-ulnar curvilinear incision is utilized index finger midline extensor splitting approach is utilized extending from the natural split between the EIP and the EDC technique index finger: 20-25 degrees of flexion k-wire templates are created to achieve 20-25 degrees fusion position or angle is measured with a sterile goniometer once the appropriate position is determined, a smooth 0.045-inch K-wire is placed obliquely across the MCP joint oscillating saw is used to start parallel cuts at the proximal aspect of the proximal phalanx and distal metacarpal to expose healthy metaphyseal bone fusion surfaces are brought together and congruence/alignment checked with fluoroscopy 2.0 mm locking compression plate of appropriate length is bent to 30-degree using the K-wire template to allow for even compression Long finger: 30 degrees of flexion Ring finger: 35 degrees of flexion Small finger: 40 degrees of flexion complications loss of motion Arthroplasty is favored over arthrodesis for arthritis of the index through small finger MCP joints allows for the preservation of some degree of flexion-extension and abduction-adduction nonunion, hardware failure, neuroma Arthroplasty of thumb MCP joint indications less commonly utilized than arthrodesis can be indicated as motion preserving procedure if motion is limited at IP or CMC joints approach dorsal incision, exploiting extensor interval longitudinally gain access to dorsal capsule technique silicone implants pyrocarbon implants complications silicone MCP joint implants are associated with low rates of complications most frequently reported complication was change in the bone surrounding the implant, found in 4% of silicone rubber implants implant fracture rates average 2% infection is rare, seen in 0.1% to 1% of reported implants Arthroplasty of finger MCP joint indications Patients with pain that have failed nonsurgical treatment measures such as nonsteroidal anti-inflammatory medications, injections, splinting, and hand therapy are candidates for surgery approach dorsal approach allows the surgeon to tailor the extensor hood and sagittal band split based on any finger deformity or planned concomitant tendon centralization procedure, as in the cases of RA in patients with osteoarthritis, a tendon-splitting approach can be used. in cases with metacarpal volar dislocation, the volar plate can be released after bony resection to allow for relocation of the joint with arthroplasty insertion the collateral ligaments are often tensioned on the radial side and may require release on the ulnar side, to help restore coronal plane alignment the capsule and sagittal band are repaired, and the extensor tendon is centralized if needed to prevent recurrent deformity intrinsic release or transfer will help restore alignment and correct potential distal swan neck deformity techniques silicone arthroplasty functions as a spacer that is stabilized by a fibrous capsule that develops around the implant hinged one-piece stemmed implant that inherently provides coronal stability by the hinge mechanism newer implant designs have a preformed 30° flexion resting position to account for the functional resting position of MCP joints pyrocarbon arthroplasty biologically inert and has a high resistance to wear—minimizing the potential risk of particulate related inflammation and osteolysis nonconstrained anatomic implants with stems that lack bony ingrowth and require preservation of the collateral ligaments for stability metal-plastic SRA arthroplasty similar to pyrocarbon in that it better mimics the anatomy and kinematics of the native MCP joint when compared with silicone porous-coated, titanium metacarpal component with a cobalt-chromium articulation onto an all-polyethylene phalangeal component that requires cementing complications silicone arthroplasty revision surgery, infection pyrocarbon arthroplasty higher rates of failure and recurrent deformity in patients with inflammatory arthritis metal-plastic SRA revision surgery, infection Complications Nonunion incidence thumb MCP joint arthrodesis 9% rate risk factors tension band fixation smoking or nicotine use diabetes mellitus diagnosis radiographs or CT scan treatment revision arthrodesis if symptomatic ipsilateral distal radius autograft or allograft can be utilized to increase fusion mass Surgical Site Infections incidence rare, seen in 0.1% to 1% of reported implants Staphylococcus Aureus was the most common organism isolated risk factors DMARD therapy inflammatory arthritis comorbidities such as diabetes mellitus diagnosis physical exam inflammatory lab analysis treatment superficial antibiotic therapy, average 2 week course deep surgical irrigation and debridement, hardware removal, antibiotics with subsequent revision procedure after infection is cleared Hardware Failure incidence MCP joint arthroplasty implant instability in patients with RA occurred in up to 31% of SRA implants and 19% of pyrocarbon implants 4% required combined dislocation rate for all implants, however, pyocrabon implants had highest rate of acute dislocation risk factors MCP Joint arthroplasty soft-tissue deficiency collateral ligament imbalance intrinsic tightness diagnosis radiographs physical exam treatment MCP joint arthroplasty revision arthroplasty has a 71% success rate if the index procedure did not involve a silicone implant, revision to silicone arthroplasty in the setting of instability may provide the best chance of achieving a stable MCP joint