Charles Cassidy and Jennifer Green
DEFINITION
Conditions resulting in the need for arthrodesis in the hand include arthritis, unreconstructable soft tissue problems, and certain neurologic conditions.
ANATOMY
The proximal (PIP) and distal (DIP) interphalangeal joint configurations are quite similar.
The condylar heads are biconvex but slightly asymmetric, being about twice as wide volarly as dorsally.
The reciprocal bases of the distal segment are biconcave, having a central ridge.
The volar plate extends from the neck of the phalanx to the volar base of the more distal phalanx, preventing joint hyperextension.
Radial and ulnar collateral ligaments provide additional joint stability. The “true” collateral ligaments have bony attachments at both ends, whereas the accessory collateral ligaments extend from the condylar head to the volar plate.
The axis of rotation and radius of curvature for a given interphalangeal joint are fairly constant. Consequently, the true collateral ligaments are effectively isometric, while the accessory collateral ligaments resist lateral translation when the joint is extended.
As a result of the ligamentous and bony architecture, the PIP and DIP joints normally function as highly constrained hinge joints.
The extensor tendon crosses the DIP joint dorsally as the terminal tendon, inserting slightly distal to the dorsal base of the distal phalanx.
The germinal matrix of the nailbed is close to the terminal tendon insertion (average of 1.3 mm distal).
The flexor digitorum profundus (FDP) tendon inserts broadly on the volar aspect of the distal phalanx, extending from the base to the midshaft.
Over the PIP joint, the extensor apparatus splits into thirds. Contributions from the extensor tendon, the interosseous tendons, and lumbricals form the central slip, which inserts onto the dorsal base of the middle phalanx. The lateral bands travel past the PIP joint along the lateral margins, and then combine to form the terminal tendon distally.
The flexor digitorum superficialis (FDS) tendon splits to insert on the volar lateral margins of the proximal shaft of the middle phalanx.
Unlike the interphalangeal joints, the metacarpophalangeal joints (MCP) are multiaxial, permitting motion in multiple planes.
The metacarpal head has a complex, convex shape. Viewed end-on, the metacarpal head is pear-shaped, being wider volarly. In the sagittal plane, the radius of curvature increases progressively from dorsal to volar.
The metacarpal attachment of the collateral ligaments is dorsal to the axis of rotation. The phalangeal and volar plate attachments are similar to the interphalangeal joint.
As a consequence of the metacarpal head shape and ligament attachments, the MCP joints are typically more lax in extension and tight in flexion.
Significant variability exists in the shape of the thumb metacarpal head. Some heads are more square than round, potentially limiting lateral translation and MCP flexion.
In the thumb, the extensor pollicis brevis (EPB) tendon inserts onto the dorsal base of the proximal phalanx. The size of the EPB tendon is variable.
For some patients, the extensor pollicis longus (EPL) tendon assumes the major role in MCP joint extension.
In the other digits, no direct extensor attachment exists. MCP joint extension occurs through a sling effect of the sagittal hood fibers lifting the proximal phalanx through the pull of the extensor tendon.
MCP joint flexion is produced through a combination of direct intrinsic tendon attachments to the volar-lateral phalangeal base and indirect actions of the intrinsics on the more distal transverse fibers of the extensor hood.
PATHOGENESIS
Arthritis is the principal indication for small joint arthrodesis.
Osteoarthritis (OA) most commonly affects the DIP joints. It is estimated that at least 60% of individuals over age 60 have DIP joint arthritis, which may not necessarily be symptomatic.
In the early stages, the joints may be painful and swollen in spite of normal radiographs. As the arthritis progresses, osteophytes and mucous cysts may develop. Bony prominences (Heberden nodes) and angular deformities in both the coronal and sagittal planes (mallet appearance) may develop. In the final stages, DIP joint motion may be severely restricted.
OA may also involve the PIP joints and the MCP joints, especially in the index and middle fingers.
Inflammatory arthritis may also affect the small joints of the hand. About 70% of rheumatoid patients have hand involvement. Synovitis may result in deformity due to attenuation of supporting structures (collateral ligaments, extensor tendons) long before arthritic changes are evident.
At the DIP joint, terminal tendon incompetence may result in a secondary swan-neck deformity.
At the PIP joint, central slip attenuation results in a boutonnière deformity.
At the MCP joint, collateral ligament involvement may contribute to ulnar drift. Persistent synovitis produces cartilage loss.
Hand involvement in systemic lupus erythematosus (SLE) may mimic rheumatoid arthritis. Supporting structures are affected principally in SLE, which may result in joint subluxation or dislocation with relatively normal-appearing articular cartilage. The capsuloligamentous problems may compromise attempts at joint salvage.
In contrast, psoriatic arthritis may produce a remarkable degree of bone loss as the arthritis progresses. Pencil-in-cup deformity is a characteristic feature of psoriatic arthritis of the interphalangeal joints. Severe bone resorption is the characteristic feature of arthritis mutilans, most commonly seen in patients with psoriatic arthritis. Arthrodesis is the most reliable method for halting this destructive process.
Scleroderma typically produces PIP flexion and MCP extension contractures. Impaired vascularity of the digits may result in dorsal PIP ulcer formation and central slip attenuation, compounding the PIP flexion deformity.
Presentations of crystalline arthropathy in the small joints of the hand may be varied. The process may be indolent, presenting as gouty tophi over the DIP joint, or acute, presenting as an exquisitely painful, swollen, tender joint. Untreated, gout results in a resorptive arthritis.
Infection is another cause of small joint arthritis.
A “fight bite” directly inoculates the MCP joint and, if undertreated, can result in rapid joint destruction.
Contiguous spread, for example, from a felon or a wound over the DIP or PIP joint, may destroy the adjacent joint.
Hematogenous spread is an uncommon cause of septic arthritis in the hand.
Trauma is another cause of unreconstructable problems in the small joints of the hand.
Intra-articular fractures and fracture-dislocations may result in arthritis, particularly in cases of residual joint incongruity. The PIP joint does not tolerate injury well.
Severe periarticular soft tissue injuries may cause severe joint stiffness, even if the underlying joint surface is not initially involved. Certain soft tissue injuries, such as central slip disruptions, may confound attempts at reconstruction.
Central or peripheral nerve injury may produce imbalances in the hand. Arthrodesis can potentially simplify reconstructions in an effort to improve function.
PATIENT HISTORY AND PHYSICAL FINDINGS
Pain is the most common complaint of patients who are candidates for arthrodesis. Ideally, the location of the pain should correlate with the joint in question.
In OA, multiple DIP joints may appear abnormal, although they may not necessarily be painful.
Polyarticular involvement is common in rheumatoid arthritis. A priority list should be elicited from the patient.
Handedness, occupation, and avocational activities should be documented.
The functional impact of the problem should be clearly defined.
When a single joint is involved, a history of trauma should be sought.
In cases of acute, painful swelling, a history of penetrating injury, gout, or recent infection should be considered.
The physical examination should include the appearance of joints and overlying skin, active and passive range of motion of the affected joints, stability, grip and pinch strength, and sensibility.
The status of adjacent joints should be evaluated.
For example, chronic DIP OA resulting in a DIP flexion deformity may produce a secondary hyperextension deformity of the PIP (swan-neck) that may be more disabling than the primary (DIP) problem.
Multiple DIP joint bumps (Heberden nodes) are a characteristic feature of OA.
Mucous cysts are suggestive of underlying DIP OA.
Onycholysis and eczema are suggestive of psoriatic arthritis.
Discrepancies between active and passive motion are indicative of an associated tendon problem.
Stress examination may demonstrate collateral ligament incompetence.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiographs (posteroanterior [PA], lateral, oblique) of the affected digit are usually sufficient to make the diagnosis.
In cases of suspected inflammatory arthritis, a collagen vascular screen is ordered. This blood panel includes a rheumatoid factor, ANA, complete blood count with differential, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).
A uric acid level may be drawn in cases of suspected gout.
Blood tests are not generally helpful in the setting of an acute finger infection.
MRI or ultrasound may rarely be ordered to evaluate tendon pathology if stiffness is associated with tendon abnormality.
DIFFERENTIAL DIAGNOSIS
OA
Inflammatory arthritis (rheumatoid, SLE, psoriatic arthritis)
Crystal arthritis
Posttraumatic arthritis
Infection
NONOPERATIVE MANAGEMENT
The mainstays of nonoperative treatment for unreconstructable small joint problems in the hand include oral medications, splints, and intra-articular corticosteroid injections.
For OA and posttraumatic arthritis, oral anti-inflammatory agents may reduce pain and stiffness.
Glucosamine and chondroitin sulfate appear to be of limited value for hand arthritis.
Rheumatoid patients can consider modifications in their medication regimen, supervised by a rheumatologist.
Resting splints may reduce pain and inflammation.
At the DIP and PIP joints, a simple padded aluminum splint may suffice.
Corrective splints, such as the safety pin static progressive or LMB dynamic splint (DeRoyal), will not be tolerated when the joint is inflamed.
For the thumb MCP joint, a hand-based thermoplast splint may lessen discomfort and improve function.
Buddy taping to the adjacent digit may be appropriate for some MCP joint problems. Dynamic MCP joint splints are usually reserved for postoperative protection.
Corticosteroid injections may provide temporary relief of pain and synovitis. The joint may be difficult to access and the joint capacity is quite small.
The surgeon should use a 27-gauge needle and inject 0.5 mL of Celestone Soluspan and 0.5 mL of 1% Xylocaine through a dorsal approach.
SURGICAL MANAGEMENT
Arthrodesis Versus Arthroplasty
Arthrodesis is a reliable procedure for managing arthritis and instability of the DIP joint. The functional impairment from loss of motion at the DIP joint is minimal.
At the PIP joint level, the surgeon and patient must weigh the potential benefits of stability and pain relief against the functional impairment resulting from the loss of PIP joint motion. For the index finger, PIP joint stability is critical for pinch. On the other hand, in the small finger, PIP joint mobility is necessary for grip.
As a general rule, for isolated unreconstructable PIP problems, the index finger gets arthrodesis, the middle finger gets arthrodesis or arthroplasty, and the ring and small fingers get arthroplasty.
Exceptions to the rule include associated unsalvageable tendon problems and soft tissue coverage issues, in which arthrodesis may be preferred.
The status of the adjacent joints is an important factor in deciding whether to perform arthrodesis or arthroplasty. In the rheumatoid patient with both MCP and PIP involvement, the temptation is to perform arthroplasties of all involved joints. So-called double-row arthroplasties tend to compromise the results at both the MCP and PIP joints. In such instances, the goal is stability at the PIP joint (arthrodesis) and motion at the MCP joint (arthroplasty).
Arthrodesis of the thumb MCP joint is a reliable procedure for managing arthritis and unreconstructable ligament problems. Arthrodesis is a far superior procedure to arthroplasty for the thumb. However, before undertaking this, it is important to ensure adequate motion and function of the adjacent joints (interphalangeal, carpometacarpal).
The chronic radial collateral ligament tear with static volarulnar subluxation is a good indication for thumb MCP fusion.
Arthrodesis of the digital MCP joints is not commonly performed. Indications include multiply failed arthroplasty or inadequate bone stock for arthroplasty, unrelenting infection, refractory instability of the index MCP, and an unreconstructable extensor mechanism.
Candidates for arthrodesis must understand that all motion in the affected joint will be eliminated, and that the principal goals are pain relief and stability.19
Arthrodesis Position
The fusion position varies with the digit and joint involved. Invariably, the decision is a compromise between appearance and function. The ideal posture should replicate the normal digital cascade (FIG 1).
In general, the DIP joints and thumb interphalangeal joint should be fused in 0 to 10 degrees of flexion.14
For the PIP joint, some authors recommend a uniform 40-degree flexion position for all digits,6 while others recommend 40 degrees for the index finger, progressing ulnarward in 5-degree increments to 55 degrees in the small finger.17
Many prefer a slightly more extended position for the index PIP that will still allow functional tip-to-tip pinch.
The recommended fusion angle of the MP joints is a cascade from 25 degrees of flexion in the index digit, progressing ulnarward in 5-degree increments to 40 degrees in the small finger.14
FIG 1 • Recommended positions for digital joint fusion.
The recommended fusion angle of the MP joint of the thumb is 10 to 15 degrees of flexion.14
Fixation Options
The choice of surgical technique depends on a number of factors, including the affected joint to be fused, the availability and cost of implants, the adequacy of bone stock, and the comfort of the surgeon. The goal is to achieve a solid fusion of the affected joint in a timely manner. Bone preparation is essential.
The specific method of fixation may be less important in obtaining union than specific patient factors such as bone quality. Certain constructs, such as the tension band, are more rigid but may be associated with more hardwarerelated problems.
The biomechanical issues must be weighed against potential soft tissue problems when deciding on a form of fixation. Maintenance of motion in the adjacent joints is critical.
Kirschner wire fixation has been associated with fusion rates of up to 99%.
Advantages
Simplicity of the technique
Ready availability of low-cost implants
Disadvantages
Infection risk, including superficial pin site and deep wound infections, osteomyelitis; pin migration; minimal compression across the fusion site
Less rigid fixation,9 requiring additional external immobilization to enhance stability, possibly leading to stiffness of surrounding joints8,15
Interosseous wiring has been found to be biomechanically stronger than Kirschner wire fixation.18 It is especially useful for PIP fusion and thumb interphalangeal fusion.
Advantages
Biomechanically stronger than Kirschner wire fixation18
Readily available low-cost implants
Disadvantages
Large amount of soft tissue stripping for appropriate placement of drill holes
Higher rate of nonunion, up to 9%11
Tension band fixation is a biomechanically stable method of fixation16 combining parallel Kirschner wires for rotational control and interosseous wiring for compression. This technique is especially useful for MCP, PIP, and thumb interphalangeal arthrodesis.
The tension band construct converts the strong distracting force created by the finger flexors to a compressive force across the arthrodesis interface.
This technique is relatively simple, with a high fusion rate and reliable outcomes,1,16 especially when used for arthrodesis of the MCP and PIP joints.
Postoperative immobilization is necessary only in the immediate postoperative period to allow for healing of the incision.1,8
Advantages
Simplicity of the procedure
Low rate of infection16
High fusion rates, reportedly 97% to 100%1,16
Readily available, low-cost implants
Enhanced biomechanical stability and strength of the construct, allowing for early active range of motion16 The tension band construct for small joint arthrodesis has been shown to be biomechanically superior compared to crossed Kirschner wire fixation and intraosseous wiring, especially in anteroposterior bending and in axial torsion.9
Disadvantages
Increased soft tissue dissection to place the drill holes, with resultant increased risk of soft tissue and tendon scarring
Difficult to remove fully internalized hardware if necessary
Plate fixation provides biomechanically strong fixation, especially useful for PIP and MCP joint arthrodesis.4,19
Advantages
Excellent fusion rate by 6 weeks, 96% to 100%16
Ability to correct deformity
Useful in cases with segmental bone loss4
Disadvantages
Technically demanding
Time-consuming
Extensor tendon adhesions, possibly necessitating hardware removal and tenolysis16 ; stiffness in adjacent joints
Hardware prominence
Compression screw fixation is a biomechanically strong fixation technique20 that is especially useful for arthrodesis of the finger DIP and PIP joints, as well as the thumb interphalangeal joint.
Using a headless screw keeps the fixation hardware low profile and prevents the problems associated with prominent hardware.
PIP joint fusion uses the same principles but has a slightly different surgical technique.2
Advantages
Fusion rates 85% to 98%2,3
Hardware is buried and low profile.
Disadvantages
Risk of infection
Risk of penetration and fracture of the dorsal cortex,3 especially with screw fixation of the PIP joint,20 resulting in poor fixation
Risk of nail irregularities from disturbance of germinal matrix3 in DIP fusion
Complications
Risk of infection, hardware complications, nail irregularities secondary to penetration of the dorsal cortex of the distal phalanx by the screw, and fractures of the dorsal cortex from screw breakthrough3
Easily avoided by maintaining adequate space between the dorsal proximal entry site and the arthrodesis site
For DIP arthrodesis, the nail-associated complications usually occurred in the small finger because of the large diameter of the screw used relative to the size of the small finger distal phalanx medullary canal.20 This is less of a problem in the distal phalanges of the other fingers or thumb.2,3
Preoperative Planning
Radiographs of the affected joint must be reviewed before operative management. Assessment of the bone stock, quality, and size is useful in helping to determine the optimal type of surgical fixation.
Should a fusion screw be considered, templates may be used to determine the appropriate screw length and diameter.
Positioning
The patient is placed in the supine position, with the affected limb resting on a hand table. Sterile preparation and draping is performed.
For arthrodesis of the PIP and DIP joints, local anesthesia with or without sedation is adequate.
Two percent mepivacaine provides a rapid rate of onset and lasts about 1 hour.
For the PIP joint, a web space block is performed, including the dorsal cutaneous branches.
For the DIP joint, the flexor tendon sheath is injected.
For the MCP joint, either regional or general anesthesia is necessary.
TECHNIQUES
DIP JOINT ARTHRODESIS
Exposure
A digital tourniquet is used.
Center a dorsal H-shaped incision over the DIP joint (TECH FIG 1A).
Transect the terminal tendon (TECH FIG 1B).
Release the collateral ligaments from the middle phalanx, using a no. 15 blade directed dorsally, parallel to the sides of the phalanx (TECH FIG 1C).
Preparation of the DIP Joint
Hyperflex the DIP joint and remove peripheral osteophytes with a small rongeur.
Remove the volar condyles of the head of the middle phalanx with the rongeur.
Identify the periphery of the base of the distal phalanx with a no. 15 blade, protecting the germinal matrix and the neurovascular bundles.
TECH FIG 1 • A. Dorsal H-shaped incision, centered over the distal interphalangeal joint. B. The terminal tendon is transected and flaps are elevated. The probe is under a large dorsal loose body. C. The collateral ligaments are released from the head of the middle phalanx by orienting a no. 15 blade upward and parallel to the ligament recesses.
Remove bone necessary to correct any joint malalignment, but minimize loss of digital length.
Dechondrify and decorticate the opposing surfaces until healthy-appearing bone is present.
Contour the head of the middle phalanx into a transversely oriented cylindrical shape (TECH FIG 2A), and fashion the base of the distal phalanx into a reciprocal shape.
Alternatively, create flat opposing surfaces perpendicular to the shafts.
On occasion, the base of the distal phalanx is eburnated. Multiple 0.035-inch drill holes may be placed (“pepperpot” technique), which may then be connected with a small rongeur to unveil subchondral bone (TECH FIG 2B,C).
Reduction and Fixation
The type of fixation depends on the size of the bone. An Acutrak fusion screw (Acumed, Hillsboro, OR) is preferred when the diameter of the middle and distal phalanges is sufficient to accommodate the screw.
Insert a 0.062-inch Kirschner wire antegrade beginning at the base of the distal phalanx and exiting the tip of the distal phalanx, just volar to the nail plate (TECH FIG 3A).
If the Kirschner wire penetrates the nail plate, discard it and use another to minimize the likelihood of contamination.
Drive a smooth 0.062-inch Kirschner wire retrograde into the center of the middle phalanx to create a pilot hole, and then remove it (TECH FIG 3B).
Reduce and compress the joint and then advance the wire retrograde across the DIP joint into the middle phalanx (TECH FIG 3C).
Assess the reduction and Kirschner wire position clinically and fluoroscopically (TECH FIG 3D).
While manually maintaining the joint position, remove the Kirschner wire and replace it with the appropriate drill bit.
Proper drill bit size is based on preoperative templating as well as an estimate of the available space based on the lateral fluoroscopic image with the 0.062-inch Kirschner wire in place.
While maintaining compression across the joint, advance the drill retrograde by hand along the path created by the removed Kirschner wire (TECH FIG 3E).
Determine the proper depth by fluoroscopy, using the external drill bit markings as a reference.
Remove the drill bit and insert the appropriate-sized fusion screw (TECH FIG 3F) while maintaining manual compression across the joint.
Final seating of the screw is based on the external reference used for the drill bit.
TECH FIG 2 • A. The distal interphalangeal joint is hyperflexed. Peripheral osteophytes and the volar condyles are removed. The remaining articular surface is dechondrified and decorticated with a rongeur, fashioning reciprocal surfaces. B. Placing multiple small drill holes facilitates débridement of eburnated bone at the base of the distal phalanx. C. Appearance after preparation of the distal interphalangeal joint.
TECH FIG 3 • A. A 0.062-inch Kirschner wire is driven antegrade through the center of the distal phalanx. B. A second 0.062-inch Kirschner wire is driven retrograde down the center of the middle phalanx to prepare a path for the screw. C. The distal interphalangeal joint is reduced and the distal Kirschner wire is driven retrograde into the middle phalanx. D. Proper alignment is confirmed fluoroscopically. The diameter of the intramedullary Kirschner wire is used as a reference for determining the screw diameter, based on the lateral radiograph. E.The Kirschner wire is removed. While maintaining manual compression across the joint, the appropriate drill bit is advanced by hand retrograde through the Kirschner wire path under fluoroscopic control. External markings on the drill bit serve as a reference for depth. F. The appropriate-sized screw is selected and secured to the driver. External markings on the driver correlate with the drill bit. G,H. PA and lateral radiographs during screw insertion. I. An alternative method of fixation involves the use of two or three Kirschner wires. J. Clinical appearance after fixation and closure.
Avoid inadvertent malrotation of the distal segment as the screw is tightened.
Obtain final radiographs and evaluate the stability (TECH FIG 3G,H).
Insert a supplemental 0.035-inch oblique Kirschner wire if necessary for stability.
If Kirschner wires are used as the sole form of fixation, drive an appropriate-diameter pin antegrade into the distal phalanx, reduce the joint, and advance the pin retrograde, preferably into the subchondral plate at the base of the middle phalanx.
One or two additional Kirschner wires are inserted obliquely in a retrograde fashion.
Final radiographs are obtained, and the pins are cut beneath the skin (TECH FIG 3I).
Completion
Remove the digital tourniquet and achieve hemostasis using bipolar electrocautery.
Irrigate the wound copiously.
Approximate the skin with 5-0 nylon interrupted sutures
(TECH FIG 3J).
Repair of the terminal tendon is unnecessary.
Apply a sterile dressing and dorsal aluminum DIP splint, leaving the PIP joint free.
Instruct the patient on PIP exercises.
PIP JOINT ARTHRODESIS
Exposure
Make a longitudinal dorsal incision.
The surgical approach is similar to the thumb MCP arthrodesis (discussed later).
In the multiply operated finger, a pre-existing midaxial scar may be used.
The central slip and capsule are split longitudinally and elevated subperiosteally.
The collateral ligaments are released from the middle phalanx, using a no. 15 blade directed dorsally, parallel to the sides of the phalanx.
Preparation of the PIP Joint
Hyperflex (shotgun) the PIP joint and prepare the joint in the manner detailed for the DIP joint.
Correct joint malalignment but minimize loss of digital length.
As for the DIP joint, contour the head of the proximal phalanx into a transversely oriented cylindrical shape, and fashion the base of the distal phalanx into a reciprocal shape.
Alternatively, use a water-cooled sagittal saw to cut flat surfaces perpendicular to the phalangeal shafts in the coronal plane, and with an appropriate degree of flexion in the sagittal plane.
The flexion angle is built into the proximal phalanx saw cut. The middle phalanx cut is perpendicular to the axis of the phalanx in the sagittal plane.
There is little room for error with the bone cuts. Commitment to the final position of the arthrodesis is made when the bone cuts are made. Any change may result in excessive shortening of the bone.7
On occasion, as with the DIP joint, the base of the middle phalanx is eburnated. Multiple 0.035-inch drill holes may be placed (“pepperpot” technique), which may then be connected with a small rongeur to unveil subchondral bone.
TECH FIG 4 • A. Preoperative PA radiograph demonstrating advanced osteoarthritis of the index proximal interphalangeal joint. Note the angular deformity, joint space loss, and large subchondral cyst. B. Postoperative PA radiograph demonstrating proximal interphalangeal arthrodesis with tension band fixation.
Kirschner Wire Fixation
In patients with inflammatory arthritis, the overlying skin is quite thin and may not tolerate prominent hardware. In those instances, crossed 0.035to 0.045-inch Kirschner wires are used.
Preset the appropriately sized Kirschner wires into the sides of the middle phalanx.
Reduce and compress the joint manually, then advance the Kirschner wires in a retrograde manner into the proximal phalanx.
If the skin is very thin, it may be impossible to cut the Kirschner wires beneath the skin. In those instances, the Kirschner wires are simply bent and left exposed.
Tension Band Fixation
A tension band technique is used for posttraumatic and OA cases, particularly those involving the index PIP joint (TECH FIG 4A).
Use a 0.035-inch Kirschner wire to make a transverse hole in the middle phalanx, dorsal to the mid-axis, about 8 mm distal to the joint.
Pass a 26-gauge surgical steel wire through the hole.
With the joint manually reduced, drive parallel 0.035to 0.045-inch Kirschner wires antegrade across the PIP joint into the subchondral head of the middle phalanx.
Begin the Kirschner wires on the dorsoradial and dorsoulnar margins of the proximal phalanx, about 10 mm proximal to the fusion site.
The Kirschner wires should remain intramedullary in the middle phalanx.
Loop the 26-gauge wire into a figure 8 configuration around the Kirschner wires proximally and tighten carefully with a needle driver.
A gentle distraction force on the needle holder as the device is used to turn the wire and compress the fusion site helps avoid wire breakage.
Remove the excess knot and impact the knot into bone.
Withdraw the Kirschner wires slightly, bend them as close to the bone as possible so they can capture the 26gauge wire, cut the Kirschner wires just distal to the bend, and advance them using the needle holder.
Obtain final radiographs (TECH FIG 4B) and assess stability.
Remove the tourniquet, achieve hemostasis, and irrigate the wound.
Reapproximate the extensor tendon using interrupted inverted 4-0 nonabsorbable sutures. Close the skin with 5-0 nylon interrupted sutures.
Place a sterile dressing and dorsal aluminum splint, leaving the DIP joint free. Instruct the patient on DIP joint exercises.
THUMB MCP JIONT ARTHRODESIS
Exposure
Make a longitudinal dorsal incision over the MCP joint (TECH FIG 5A).
Incise the extensor apparatus longitudinally between the EPB and EPL tendons (TECH FIG 5B). This will reveal the joint capsule (TECH FIG 5C).
Perform a longitudinal capsulotomy and subperiosteally dissect around the dorsal base of the middle phalanx (TECH FIG 5D).
Release the collateral ligaments from the metacarpal head (TECH FIG 5E), and hyperflex the MCP joint (TECH FIG 5F).
Joint Preparation
Dechondrify the articular surfaces and remove peripheral osteophytes as well as the volar condyles of the metacarpal head with a rongeur (TECH FIG 6A).
Decorticate and prepare the fusion surfaces in a “cupand-cone” configuration7,12 using Coughlin reamers (Howmedica, Rutherford, NJ) (TECH FIG 6B,C).
This method allows for maintenance of thumb length and subtle adjustments in joint position while still maintaining optimal bone contact.
The 14and 16-mm sizes are most often appropriate. Size selection is usually based on the size of the metacarpal head in order to avoid notching.
The same dimensions must be used for both metacarpal and phalangeal reaming or the surfaces will be incongruent.
Ream the base of the middle phalanx first to avoid iatrogenic injury to the metacarpal head.
Place an elevator anterior to the base of the proximal phalanx to deliver the phalanx away from the metacarpal head and to protect the flexor pollicis longus.
Advance a 0.062-inch Kirschner wire antegrade into the proximal phalanx, centered in the coronal plane (TECH FIG 6D) and slightly flexed (Kirschner wire tip dorsal) in the sagittal plane (TECH FIG 6E).
Ream the base of the middle phalanx over the Kirschner wire using the selected phalangeal “cup” reamer until uniform cancellous bone is exposed (TECH FIG 6F). Remove the reamer and the pin.
Prepare the metacarpal head by first advancing a 0.062inch Kirschner wire retrograde from the center of the head, angled slightly radially (TECH FIG 6G) and dorsally (TECH FIG 6H).
Ream the metacarpal head using the matching metacarpal “cone” reamer (TECH FIG 6I) until healthy subchondral bone is exposed (TECH FIG 6J). Then remove the reamer and the Kirschner wire.
Fixation and Reduction
Tension band fixation is performed to stabilize the thumb MCP joint fusion in much the same manner as detailed for arthrodesis of the PIP joint.
Alternative methods of fixation include Kirschner wires alone, headed or headless screw fixation, and plate fixation.
TECH FIG 5 • A. A longitudinal incision is centered over the metacarpophalangeal joint. B. The extensor hood is incised between the extensor pollicis longus and brevis tendons (dotted line). C. The hood has been split, revealing the dorsal joint capsule. D. The capsule has been incised longitudinally and reflected subperiosteally from the dorsal base of the proximal phalanx. Note the full-thickness cartilage loss along the ulnar aspect of the metacarpal head and dorsal base of the proximal phalanx secondary to volar-ulnar subluxation. E. The collateral ligaments are released from the metacarpal head. F. The metacarpophalangeal joint is now hyperflexed.
TECH FIG 6 • A. The remaining articular cartilage is removed. Peripheral osteophytes and the volar condyles are trimmed with a rongeur. B. Coughlin cup and cone reamers. Care must be taken to ensure that the same-sized reamer is used for both sides to maximize bone contact. C. The metacarpal head is used as a reference in determining reamer size. The smallest reamer that will not notch the cortex is selected. D,E. A 0.062-inch Kirschner wire is advanced antegrade in the proximal phalanx to be used as a guidewire. The pin is positioned in the center of the bone in the coronal plane (dot in the center of the interphalangeal joint) and in slight flexion in the sagittal plane. F. The “cup” reamer is placed over the Kirschner wire under power with frequent irrigation until bleeding subchondral bone is revealed. The asymmetry of the base of the proximal phalanx due to chronic subluxation is corrected. G,H. A 0.062-inch Kirschner wire is then inserted retrograde into the metacarpal head. The pin is positioned in slight flexion and slight ulnar deviation. I. The matching “cone” reamer is placed over the Kirschner wire under power with frequent irrigation until bleeding subchondral bone is apparent. J. Appearance of the surfaces after joint preparation.
The tension band construct is strong enough to allow for early motion with a hand-based splint.
Plate fixation is reserved for cases of bone loss requiring supplemental grafting.
Use a 0.045-inch smooth Kirschner wire to create a transverse hole in the proximal phalanx, about 1 cm distal to the joint and dorsal to the midline.
Pass a 24 or 26-gauge surgical steel wire though the tunnel (TECH FIG 7A).
Anticipating the ultimate position of the thumb fusion, advance parallel 0.054 or 0.062-inch Kirschner wires retrograde, exiting dorsally along the metacarpal shaft (TECH FIG 7B).
Reduce the MCP joint in slight (less than 25 degrees) flexion, abduction (5 degrees), and pronation (5 degrees), and drive the preset Kirschner wires antegrade.
Take care to avoid perforating the volar cortex into the flexor tendon sheath.
TECH FIG 7 • A. A 24-gauge wire is passed through a drill hole in the proximal shaft of the proximal phalanx, dorsal to the midline and parallel to the joint. B. A 0.062-inch Kirschner wire is then driven retrograde in the metacarpal head, exiting dorsally, anticipating the ultimate position of the metacarpophalangeal joint. C. The 24-gauge wire is looped around the base of the Kirschner wires in figure 8 fashion and tensioned. The Kirschner wires are cut short and the wire knot is tamped against the cortex.
Loop the wire in a figure 8 configuration around the Kirschner wires, and tighten using a needle driver.
Trim excess wire and impact the knot into the bone.
Pull back, bend, cut, and advance the Kirschner wires (as detailed earlier) to secure the tension band wire (TECH FIG 7C).
Completion
Remove the tourniquet, achieve hemostasis, and irrigate the wound.
Close the capsule over the hardware using absorbable 4-0 suture and then close the extensor mechanism using 4-0 nonabsorbable interrupted inverted stitches (TECH FIG 8A).
Approximate the skin using 5-0 nylon interrupted suture, and apply a sterile dressing and radial gutter splint.
The interphalangeal joint is left free, and the patient is instructed on interphalangeal motion exercises.
Obtain final radiographs (TECH FIG 8B,C).
TECH FIG 8 • A. The capsule and extensor hood are repaired in layers. B,C. Postoperative PA and lateral radiographs demonstrate good joint apposition and alignment.
INDEX THROUGH SMALL FINGER MCP JOINT ARTHRODESIS
The approach and bone preparation mirror those described for the thumb.
Fixation may be achieved with Kirschner wires alone, a tension band construct, screws, or plates (TECH FIG 9).
Keep in mind the anticipated deforming forces, which may be out of plane with the fixation.
Immobilization should protect the fused joint from stress, while simultaneously permitting motion of the PIP and DIP joints. We prefer to apply a short-arm cast extending out to the PIP joints, allowing PIP and DIP motion.
TECH FIG 9 • A, B. PA and lateral radiographs showing chronic right index metacarpophalangeal volar-ulnar subluxation in patient who had undergone two previous attempts at radial collateral ligament reconstruction. C,D. Postoperative PA and lateral radiographs demonstrating loss of fixation after cup-and-cone tension band arthrodesis. E,F. PA and lateral radiographs after successful revision of the index metacarpophalangeal arthrodesis. This included redébridement of the bone ends and repeat tension band fixation as well as supplemental fixation using a 2-mm plate to control outof-plane forces perpendicular to the tension band. G. Clinical photograph after index metacarpophalangeal fusion. For this patient, a professional photographer, the metacarpophalangeal joint position was chosen to permit optimal control of the camera shutter.
ADDITIONAL FIXATION METHODS
The surgical approach, bone preparation, and closure are performed as detailed earlier.
Most frequently, flat bone cuts are used with these fixation techniques.
Interosseous Wiring
Drill two parallel holes from dorsal to volar, each 3 to 4 mm away from the arthrodesis site, using a 0.035-inch Kirschner wire.
Drill two additional holes, this time in the radioulnar plane, again about 3 to 4 mm on either side of the arthrodesis site.
Thread two 26-gauge surgical steel wires through the drill holes.
A 20-gauge hypodermic needle may be used to facilitate wire placement.
Pass one wire from dorsal to volar through one drill hole, and then volar to dorsal in the parallel drill hole, forming a loop.
Pass the second 26-gauge steel wire through the drill holes in the coronal plane, forming a second loop.
After the wires are placed, tighten the ends of the wires sequentially and shorten and bend them to decrease their profile.
This configuration results in two perpendicular loops providing compression and fixation across the arthrodesis interface.
Plate Fixation
Fill bone defects with intercalary grafts as needed (TECH FIG 10A,B).
Select the largest compression plate that will not be prominent.
These range in size from 1.5 to 2.7 mm.
The plate is precontoured to match the angle of the fusion.
A slight increase in concavity is created to allow compression of the volar cortex when the plate is applied (TECH FIG 1C).
Insert a bicortical screw through the plate into the distal fragment.
Be certain that this and other screws do not penetrate the volar cortex and impair the function of the flexor tendons.
Using AO compression technique, place a screw through the plate into the proximal fragment.
Drill as proximally and eccentrically as possible within the plate’s screw hole so that when the screw is tightened, compression is obtained.
Place the remaining screws (TECH FIG 1D).
Four to six cortices on either side of the fusion site provides adequate fixation.14
Compression Screw Fixation
In much the same manner as described for placement of Kirschner wires for tension band fusion of the thumb MCP joint, the guidewire is introduced into the proximal fragment in a retrograde manner, exiting the dorsal cortex at least 5 mm proximal to the arthrodesis site.
TECH FIG 10 • A,B. After silicone implant arthroplasty, rigid swanneck deformities developed. Conversion to arthrodesis in a more functional position was complicated by large bone defects resulting from removal of the implants. C. A prebent 2-mm dynamic compression plate is applied to the dorsal surface for the proximal and middle phalanges. D. Lateral radiograph depicts placement of intercalary bone graft and compression plate fixation. Screw length is carefully determined to avoid irritation of the flexor tendons. (Copyright Thomas R. Hunt III, MD.)
This protects against inadvertent fracture of the dorsal cortex.
Manually reduce and compress the prepared joint.
It may be helpful to place a small (0.028to 0.035-inch) provisional Kirschner wire away from the anticipated screw site to provide rotational stability.
Advance the guidewire antegrade from proximal to distal, perpendicular to the fusion interface, and into the medullary canal of the distal segment.
Advance the wire just beyond the mid-diaphyseal region of the distal fragment.
Evaluate clinically and fluoroscopically to ensure proper position (TECH FIG 11).
Measure the guidewire and choose the appropriatelength screw to ensure that after compression, the distal screw threads will engage the endosteal cortex and the proximal aspect of the screw will be buried.
Remove the derotation Kirschner wire.
TECH FIG 11 • PA and lateral radiographs demonstrating arthrodesis of proximal interphalangeal joints with cannulated, headless compression screws. (Copyright Thomas R. Hunt III, MD.)
POSTOPERATIVE CARE
Postoperative management depends on the involved joint and method of fixation. Early motion of the adjacent joints is critical to minimize stiffness.
For DIP joint arthrodesis, protection with a simple aluminum splint is sufficient. PIP motion is encouraged. Splinting may be unnecessary if a fusion screw is used. Radiographs are taken at 6 weeks postoperatively. Buried pins may be removed once the fusion is radiographically solid (at least 8 weeks postoperatively).
For PIP joint arthrodesis, tension band, screw, and plate constructs are usually strong enough to obviate the need for supplemental splinting. Early MCP and DIP motion is encouraged; however, the patient is advised against lateral stress or forceful grip with the affected digit. With simple pin fixation, a supplemental dorsal aluminum or thermoplast PIP splint is used until radiographs demonstrate union.
For the thumb MCP joint treated with tension band fixation, a protective custom-molded thermoplast hand-based MCP splint is used for about 6 weeks. Early IP joint motion is encouraged.
In general, arthrodesis of the other MCP joints must be protected with a handor forearm-based splint, regardless of the type of fixation. Significant flexion and lateral stresses must be neutralized while simultaneously allowing for PIP and DIP motion. It may be necessary to splint the PIP joint in extension part-time to prevent an extensor lag from developing.
OUTCOMES
Multiple studies have evaluated the biomechanical advantages of one type of surgical technique versus another in order to establish the most rigid type of fixation that will allow a rapid and complete arthrodesis.
A comparison between the failure load of a Herbert screw and the failure load of a tension band construct showed no significant difference between the two2 ; the authors concluded that these two methods of fixation have similar biomechanical strength.
A comparison of multiple fixation techniques showed that arthrodesis by screw fixation had a better fusion rate than Kirschner wires, tension band construct, and plate fixation.10
A comparison of tension band constructs versus Kirschner wire fixation for PIP joint arthrodesis concluded that tension bands provide more rigid fixation.9
Biomechanical testing comparing the Herbert screw and tension band construct for DIP arthrodesis showed that the Herbert screw has significantly higher bending strength as well as more rigidity against axial torsion, although no difference was noted in the bending stiffness between these two methods of fixation.20
COMPLICATIONS
Pin tract infection
Nonunion
Malunion
Vascular insufficiency
Skin necrosis
Cold intolerance
Stiffness of adjacent digits
Painful hardware
REFERENCES
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