Surgical Management of Interphalangeal Joint Deformities and Arthritis

Comprehensive Introduction and Patho-Epidemiology

The surgical management of interphalangeal (IP) joint pathology represents one of the most technically demanding and conceptually nuanced frontiers in hand surgery. Whether driven by post-traumatic deformity, inflammatory arthropathy, or primary osteoarthritis, the destruction of the proximal interphalangeal (PIP) or distal interphalangeal (DIP) joints profoundly disrupts the intricate kinematic chain of the hand. The delicate balance of the extensor mechanism, combined with the immense shear forces generated during grip and pinch, dictates that surgical interventions must be meticulously tailored to the specific digit, the underlying pathoanatomy, and the patient's functional demands.

Primary osteoarthritis of the hand exhibits a strong genetic predilection and a marked female predominance, particularly in post-menopausal populations. The patho-epidemiology of primary nodal osteoarthritis is characterized by the progressive degeneration of articular cartilage, subchondral sclerosis, and the formation of marginal osteophytes—clinically manifesting as Bouchard’s nodes at the PIP joints and Heberden’s nodes at the DIP joints. These osteophytic excrescences often lead to collateral ligament attenuation, asymmetric joint space narrowing, and subsequent coronal plane deformities. In contrast, post-traumatic arthritis typically presents as a monoarticular pathology secondary to intra-articular fractures, chronic fracture-dislocations, or untreated ligamentous ruptures, leading to rapid, asymmetric chondral wear and profound joint stiffness.

Inflammatory arthropathies, most notably rheumatoid arthritis (RA), present a distinctly different patho-epidemiological profile. The primary insult in RA is synovial proliferation and pannus formation, which enzymatically degrades articular cartilage and mechanically distends the joint capsule. This capsular distension inexorably leads to the attenuation of the stabilizing ligamentous structures and the delicate extensor apparatus. At the PIP joint, this frequently results in the classic boutonnière deformity or the swan neck deformity, depending on whether the central slip or the volar plate is the primary site of failure. The systemic nature of RA requires the surgeon to consider the entire hand as a functional unit, as isolated procedures may fail if adjacent joint deformities are not simultaneously addressed.

This comprehensive academic review explores two critical facets of interphalangeal joint surgery: the correction of mild boutonnière (buttonhole) deformities via distal extensor tenotomy, and the evidence-based decision-making process between PIP joint arthroplasty and arthrodesis. By synthesizing biomechanical principles, pathoanatomic realities, and landmark clinical outcomes, this chapter aims to provide the orthopedic surgeon with a definitive framework for navigating the complexities of interphalangeal joint reconstruction.

Detailed Surgical Anatomy and Biomechanics

A profound mastery of the osteology, ligamentous anatomy, and extensor mechanism of the interphalangeal joints is the absolute prerequisite for successful surgical intervention. The PIP joint is a ginglymus (hinge) joint, characterized by the bicondylar geometry of the head of the proximal phalanx articulating with the biconcave base of the middle phalanx. This congruent osseous architecture affords significant intrinsic stability in the sagittal plane while restricting motion in the coronal plane. The DIP joint shares a similar, albeit smaller, bicondylar morphology. The stability of these joints is further augmented by a robust soft-tissue envelope, primarily consisting of the proper collateral ligaments (which are maximally taut in flexion), the accessory collateral ligaments (taut in extension), and the thick fibrocartilaginous volar plate, which prevents hyperextension and is anchored proximally by the check-rein ligaments.

The extensor mechanism of the digit is an exceedingly complex, interconnected aponeurotic expansion that dictates the coordinated motion of the IP joints. At the level of the proximal phalanx, the extrinsic extensor tendon trifurcates into a central slip and two lateral slips. The central slip inserts into the dorsal base of the middle phalanx, serving as the primary extensor of the PIP joint. The lateral slips are joined by the tendinous contributions of the intrinsic muscles (lumbricals and interossei) to form the lateral bands. These lateral bands converge distally, dorsal to the PIP joint axis of rotation, to form the terminal tendon, which inserts into the dorsal base of the distal phalanx to extend the DIP joint.

The delicate interplay between the PIP and DIP joints is governed by critical retinacular structures. The triangular ligament prevents volar subluxation of the lateral bands during PIP flexion, while the transverse retinacular ligament prevents excessive dorsal subluxation during PIP extension. Furthermore, the oblique retinacular ligament (ORL) of Landsmeer originates from the volar aspect of the proximal phalanx and the flexor tendon sheath, courses volar to the PIP joint axis, and inserts dorsally into the terminal tendon. This unique anatomic trajectory links PIP joint extension with DIP joint extension; as the PIP joint extends, the ORL tightens, facilitating synchronous extension of the distal phalanx.

Biomechanically, the hand operates as an asymmetric functional unit, a concept that fundamentally dictates surgical decision-making. The radial digits (index and long fingers) are primarily responsible for precision handling and lateral key pinch. During key pinch, the thumb exerts immense radially directed shear forces against the index finger. The index PIP joint must possess absolute lateral stability to withstand these forces; failure to resist this shear results in rapid joint subluxation and functional collapse. Conversely, the ulnar digits (ring and small fingers) are responsible for power grip. The biomechanical forces exerted on the ulnar digits are predominantly in the sagittal plane (flexion and extension), with minimal coronal shear. Consequently, the ulnar digits require a supple, conforming arc of motion to wrap around objects, making them biomechanically tolerant of motion-preserving arthroplasty implants that might otherwise fail under the shear stresses of the radial digits.

Exhaustive Indications and Contraindications

The decision to proceed with surgical intervention—and the selection of the specific procedure—requires a rigorous algorithmic approach that weighs the patient's physiologic age, occupational demands, specific digit involved, and the precise pathoanatomy of the deformity. Distal extensor tenotomy (the Fowler procedure) is an elegant, minimally invasive operation, but it is entirely unforgiving of poor patient selection. The procedure is strictly indicated for mild, chronic boutonnière deformities characterized by a supple PIP joint (capable of full passive extension) and a rigid, symptomatic hyperextension contracture of the DIP joint that impairs pulp-to-pulp pinch. The fundamental prerequisite is that the PIP joint must be passively correctable; if a fixed PIP flexion contracture exists, releasing the terminal tendon will simply exacerbate the functional deficit, leaving the patient with persistent PIP flexion and a newly created iatrogenic mallet deformity at the DIP joint.

When interphalangeal joints are destroyed by arthritis, the dichotomy between arthroplasty and arthrodesis is governed by the biomechanical principles outlined previously. Arthrodesis is the undisputed gold standard for the index finger PIP joint, the thumb interphalangeal joint, and all distal interphalangeal joints. In the index finger, the necessity for absolute lateral stability during key pinch precludes the use of any currently available arthroplasty implant, as both silicone and articulated devices will inevitably fail under cyclic shear loading. For the DIP joints, the functional arc of motion is relatively small, and the loss of motion following arthrodesis is exceptionally well-tolerated, providing a durable, pain-free pinch.

Conversely, PIP joint arthroplasty is highly indicated for the ulnar digits (ring and small fingers), and occasionally the long finger in low-demand patients. Flexible silicone interpositional arthroplasty remains the benchmark procedure, indicated for patients with advanced osteoarthritis, rheumatoid arthritis, or post-traumatic arthritis who require preservation of power grip and possess an intact or reconstructable soft-tissue envelope. Surface replacement arthroplasties (utilizing pyrocarbon or metal-on-polyethylene) remain controversial; while theoretically preserving bone stock and collateral ligaments, they are generally contraindicated in patients with significant coronal plane deformities, inadequate bone stock, or massive ligamentous incompetence, as these devices lack intrinsic stability.

Pre-Operative Planning, Templating, and Patient Positioning

Meticulous pre-operative planning begins with a comprehensive clinical examination designed to isolate the exact pathoanatomy. For boutonnière deformities, the surgeon must perform the Elson test to evaluate the integrity of the central slip, and the Bouvier test to determine if the PIP joint capsule and extensor mechanism are supple enough to warrant soft-tissue reconstruction rather than salvage. Active and passive range of motion must be recorded with a goniometer. In the arthritic hand, the surgeon must assess for intrinsic tightness, collateral ligament competence, and the presence of compensatory deformities in adjacent joints (e.g., MCP joint subluxation), as an isolated PIP joint intervention will fail if proximal or distal kinematic links are ignored.

Radiographic evaluation requires high-quality, true posteroanterior (PA), lateral, and oblique views of the specific digit, rather than a generic hand series. The surgeon must scrutinize the radiographs for the extent of joint space narrowing, the presence and location of osteophytes, subchondral cyst formation, and coronal or sagittal plane subluxation. When planning for arthroplasty, digital templating is mandatory. For silicone implants, the medullary canals of the proximal and middle phalanges must be measured to ensure they can accommodate the stems of the Swanson or similar implants. The surgeon must also assess bone stock; severe cystic degeneration or profound osteopenia may dictate the use of longer-stemmed implants, cementation (in articulated devices), or a pivot to arthrodesis.

Systemic optimization is particularly critical in the rheumatoid population. Coordination with the patient's rheumatologist is essential to manage disease-modifying antirheumatic drugs (DMARDs) and biologic therapies perioperatively. While methotrexate is often continued, biologic agents (e.g., TNF-alpha inhibitors) typically require cessation prior to surgery to mitigate the risk of catastrophic postoperative infection, balancing this against the risk of a systemic disease flare. Furthermore, a thorough discussion regarding the realistic expectations of surgery—specifically that arthroplasty provides pain relief and functional arc relocation rather than a normal, full range of motion—must be documented.

Patient positioning and anesthesia are tailored to the specific procedure. Distal extensor tenotomies are exceptionally well-suited for the Wide Awake Local Anesthesia No Tourniquet (WALANT) technique. Utilizing a mixture of lidocaine and epinephrine allows the surgeon to assess active, dynamic motion intraoperatively, ensuring the tenotomy has adequately corrected the deformity without inducing an iatrogenic mallet finger. For arthroplasties and arthrodeses, a regional block (axillary or supraclavicular) combined with a well-padded upper arm tourniquet is standard. The patient is positioned supine with the operative extremity on a radiolucent hand table. Loupe magnification (minimum 2.5x to 3.5x) is indispensable for the delicate dissection of the extensor apparatus and the preservation of the dorsal sensory nerve branches.

Step-by-Step Surgical Approach and Fixation Technique

Distal Extensor Tenotomy (Fowler Procedure)

The distal extensor tenotomy is performed under local anesthesia (WALANT) to facilitate intraoperative dynamic assessment. A dorsal transverse or slightly oblique incision is made over the distal third of the middle phalanx, carefully avoiding the germinal matrix of the nail and preserving the delicate dorsal sensory branches. The subcutaneous tissue is bluntly dissected to expose the terminal extensor tendon just proximal to the DIP joint capsule.

Once identified, the terminal tendon is divided obliquely. An oblique tenotomy is biomechanically far superior to a transverse division; it allows the tendon ends to slide and lengthen while maintaining partial apposition when the DIP joint is flexed. This partial contact provides a critical scaffold for secondary healing, preventing a complete, catastrophic loss of terminal extension. Following the tenotomy, the surgeon applies controlled, gentle force to stretch the DIP joint into flexion. The patient is then asked to actively extend and flex the digit. The resting posture should demonstrate improved PIP extension and slight DIP flexion. The skin is closed with non-absorbable monofilament sutures (e.g., 5-0 nylon), and crucially, the tendon itself is left unsutured to heal via secondary intention.

Silicone Interpositional Arthroplasty (Volar Approach)

The volar approach (Schneider technique) has largely superseded the dorsal approach for silicone PIP arthroplasty due to its absolute preservation of the central slip, thereby eliminating the risk of postoperative extensor lag. A Bruner zig-zag or mid-lateral incision is utilized. The flexor tendon sheath is exposed, and the C3 and C4 pulleys are incised, allowing the flexor tendons to be retracted laterally. The volar plate is identified, detached from its proximal origin at the check-rein ligaments, and reflected distally, exposing the articular surfaces of the PIP joint.

The collateral ligaments are carefully assessed; if contracted, they may be partially released from their proximal attachments to allow joint delivery. Using a microsaw, the head of the proximal phalanx is resected perpendicular to the long axis of the shaft, removing the minimal amount of bone necessary to accommodate the implant hinge. The base of the middle phalanx is minimally debrided of osteophytes, preserving the subchondral bone to prevent implant subsidence. The medullary canals are sequentially broached using specialized rasps, ensuring a rectangular configuration to prevent implant rotation. A trial silicone implant is inserted, and the joint is assessed for stability, impingement, and arc of motion. The definitive implant is inserted using a no-touch technique. The volar plate is loosely repaired to prevent hyperextension, the flexor tendons are reduced, and the skin is closed.

Proximal Interphalangeal Joint Arthrodesis

Arthrodesis of the PIP joint is typically performed via a dorsal longitudinal or lazy-S incision. The extensor mechanism is split longitudinally through the central slip, exposing the joint. The articular cartilage and subchondral bone of both the proximal and middle phalanges are meticulously resected. The surgeon may choose between flat planar cuts or a cup-and-cone reaming technique; the latter provides excellent cancellous bone contact and allows for infinite angular adjustments prior to fixation.

The angle of fusion is paramount and must be tailored to the specific digit to optimize the cascade of the hand. The index finger is fused at 40 degrees of flexion to provide a stable post for lateral pinch. The middle finger is fused at 45 degrees, the ring finger at 50 degrees, and the small finger at 55 degrees to facilitate a tight power grip. Fixation techniques vary based on bone quality and surgeon preference. Crossed Kirschner wires combined with a dorsal intra-osseous tension band wire (90-90 wiring) provide excellent, cost-effective biomechanical compression. Alternatively, modern headless compression screws offer rigid internal fixation with zero hardware prominence, allowing for immediate early motion of adjacent joints.

Volar Plate Interposition Arthroplasty

For selected younger patients or manual laborers with severe PIP osteoarthritis who would rapidly destroy a silicone implant, the volar plate interposition arthroplasty provides a robust biological alternative. Through a volar approach, the collateral ligaments are released, and the joint is fully exposed. The osteophytic articular surface of the proximal phalanx is resected, creating a smooth, concave trough.

The volar plate, which is thick and fibrocartilaginous, is mobilized proximally by releasing the check-rein ligaments. It is then advanced dorsally over the resected end of the proximal phalanx. Drill holes are made through the dorsal neck of the proximal phalanx, and the volar plate is secured into the trough using non-absorbable sutures or suture anchors. This interposes a durable biological spacer between the osseous surfaces. The collateral ligaments may be reattached if necessary. While technically demanding, this procedure eliminates the risks of implant fracture and silicone synovitis, offering excellent pain relief and functional preservation.

Complications, Incidence Rates, and Salvage Management

The surgical management of interphalangeal joints is fraught with potential complications, ranging from minor wound healing issues to catastrophic implant failures. General complications such as superficial infection, complex regional pain syndrome (CRPS), and profound postoperative stiffness can occur with any of the aforementioned procedures. Strict adherence to atraumatic soft-tissue handling, meticulous hemostasis, and early, supervised hand therapy are the primary defenses against these ubiquitous risks.

Following distal extensor tenotomy, the most feared complication is the iatrogenic mallet deformity, which occurs if the terminal tendon is completely transected or overstretched during the intraoperative flexion maneuver. This complication necessitates immediate, rigid splinting of the DIP joint in full extension for 6 to 8 weeks. Conversely, under-correction of the boutonnière deformity can occur if the PIP joint was not truly supple preoperatively, or if the lateral bands fail to migrate proximally due to severe adhesions. In cases of failure, salvage options are limited and typically require progression to PIP joint arthrodesis.

Arthroplasty complications are device-specific. Flexible silicone implants are prone to fatigue fracture over time, with radiographic fracture rates reported as high as 30% at 10 years, though clinical failure (pain and instability) is significantly lower. Silicone particulate debris can incite an aggressive foreign-body macrophage response, leading to silicone synovitis and progressive osteolysis. Surface replacement arthroplasties (pyrocarbon) suffer from high rates of subsidence, dislocation (due to inherent coronal instability), and a unique phenomenon of implant "squeaking." Salvage for any failed PIP arthroplasty is almost universally conversion to an arthrodesis, which may require structural intercalary bone grafting (e.g., iliac crest) to restore digital length lost to osteolysis or previous bone resection.

Phased Post-Operative Rehabilitation Protocols

The success of interphalangeal joint reconstruction is inextricably linked to the postoperative rehabilitation protocol. Hand therapy must strike a delicate, individualized balance between protecting the surgical repair and preventing the rapid onset of peritendinous adhesions and capsular contractures. The involvement of a certified hand therapist (CHT) is mandatory, and protocols must be explicitly communicated by the operating surgeon.

For the distal extensor tenotomy, the postoperative protocol is designed to encourage immediate, dynamic remodeling of the extensor apparatus. Routine splinting is completely avoided. The patient is instructed to begin active range of motion (ROM) exercises of both the PIP and DIP joints within 24 to 48 hours postoperatively. Active motion is critical; it forces the lateral bands to migrate proximally, thereby increasing extensor tension at the PIP joint while allowing the healing terminal tendon to lengthen in a controlled fashion. The surgeon and therapist must closely observe the DIP joint for any signs of an extensor lag. If an iatrogenic mallet deformity begins to develop, the protocol is immediately altered to splint the DIP joint in neutral extension while continuing to encourage full, active PIP joint motion.

Rehabilitation following silicone interpositional arthroplasty via the volar approach is markedly accelerated compared to historical dorsal approaches. Because the central slip is perfectly preserved, there is no risk of inducing an extensor lag. A bulky soft dressing is applied postoperatively, and within 3 to 5 days, a custom thermoplastic splint is fabricated. Early active and active-assisted range of motion is initiated. If the patient demonstrates any tendency toward a flexion contracture, a dynamic extension splint (e.g., a Capener splint) is utilized between exercise sessions and at night. Crucially, the therapist must educate the patient to strictly avoid lateral shear forces (such as lateral key pinch in the operative digit) for a minimum of 6 to 8 weeks, allowing the fibrous pseudocapsule to mature and stabilize the implant.

Following PIP joint arthrodesis, the goal is absolute mechanical stability to facilitate primary or secondary bone healing. The digit is immobilized in a custom static splint or a short-arm cast incorporating the operative digit and an adjacent buddy digit. Pin tract care is initiated if percutaneous K-wires were utilized. Edema control using compressive wraps and elevation is paramount to prevent stiffness in the unoperated MCP and DIP joints, which are left free and mobilized immediately. Radiographic evaluation is performed at 4 and 6 weeks. Rigid immobilization is maintained until unequivocal clinical union (absence of pain on stress) and radiographic union (bridging trabeculae) are achieved, typically between 6 and 8 weeks, after which progressive strengthening is initiated.

Summary of Landmark Literature and Clinical Guidelines

The evolution of interphalangeal joint surgery is deeply rooted in several landmark studies that have shaped modern clinical guidelines. The pioneering work of Alfred Swanson in the 1960s and 1970s established the flexible silicone hinge as the gold standard for small joint arthroplasty. Swanson’s concept of "resection arthroplasty with an implant spacer" revolutionized the treatment of the rheumatoid hand, demonstrating that a dynamic spacer could maintain alignment while a functional pseudocapsule formed, providing predictable pain relief and functional, albeit not normal, motion.

The surgical approach to silicone arthroplasty was profoundly influenced by the landmark review by Lin, Wyrick, and Stern. Reporting on 69 proximal interphalangeal silicone arthroplasties, they highlighted the definitive superiority of the anterior (volar) approach described by Schneider. Their study demonstrated that by preserving the central slip, patients achieved immediate, early active motion without the debilitating extensor lags that plagued the dorsal approach. They also established the clinical reality that silicone implants do not significantly increase the total arc of motion, but rather shift the arc to a more functional, pain-free range, a critical point for preoperative patient counseling.

The critical decision-making matrix between arthroplasty and arthrodesis was starkly illuminated by the pivotal study of Pelligrini and Burton. In their comparison of arthroplasty and arthrodesis in 43 PIP joints, they reported a catastrophic 100% failure rate of cemented articulated devices at an average of 2.25 years. Conversely, flexible silicone implants in the ulnar digits performed exceptionally well. Their study unequivocally concluded that no currently available implant can withstand the lateral shear forces of the radial digits, cementing arthrodesis as the absolute procedure of choice for the index finger PIP joint.

Modern consensus guidelines, including those endorsed by the American Academy of Orthopaedic Surgeons (AAOS) and the American Society for Surgery of the Hand (ASSH), continue to reflect these foundational principles. While tissue engineering and advanced biomaterials (such as pyrocarbon) represent exciting frontiers, clinical guidelines mandate extreme caution, reserving these newer devices for highly selected patients due to their unforgiving nature and high complication rates. Ultimately, the successful management of IP joint pathology relies on the surgeon's unwavering adherence to biomechanical principles, meticulous surgical technique, and rigorous patient selection.