Surgical Management of Interphalangeal Joint Deformities and Arthritis

Introduction to Interphalangeal Joint Reconstruction

The surgical management of interphalangeal joint pathology—whether driven by post-traumatic deformity, inflammatory arthropathy, or primary osteoarthritis—demands a profound understanding of 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 and the patient's functional demands.

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 proximal interphalangeal (PIP) joint arthroplasty and arthrodesis.

Correction of Mild Boutonnière Deformity by Extensor Tenotomy

Pathoanatomy and Biomechanics

The boutonnière deformity is characterized by flexion of the proximal interphalangeal (PIP) joint and hyperextension of the distal interphalangeal (DIP) joint. The primary pathoanatomic event is the attenuation or rupture of the central slip of the extensor mechanism at its insertion into the base of the middle phalanx. Following this disruption, the lateral bands subluxate volar to the axis of rotation of the PIP joint.

Once the lateral bands fall volar to the PIP joint axis, they transition from being extensors of the PIP joint to flexors. Consequently, the entire force of the extrinsic extensor mechanism is transmitted distally to the terminal tendon, resulting in a rigid hyperextension contracture of the DIP joint. Over time, the oblique retinacular ligaments contract, fixing the deformity.

For mild, chronic deformities where the PIP joint remains relatively supple but the DIP joint is locked in hyperextension, a distal extensor tenotomy (often referred to as a Fowler tenotomy) is a highly effective, minimally invasive procedure. By releasing the terminal tendon, the lateral bands are permitted to retract proximally. This proximal migration reduces the extensor tension on the DIP joint (allowing flexion) and simultaneously increases extensor tension at the PIP joint, thereby correcting the boutonnière posture.

Indications and Patient Selection

Distal extensor tenotomy is not a panacea for all boutonnière deformities. Strict adherence to indications is required for optimal outcomes.

• Indications: Mild, chronic boutonnière deformities with a supple PIP joint (capable of passive extension) and a rigid, symptomatic hyperextension contracture of the DIP joint that impairs pulp-to-pulp pinch.
• Contraindications: Fixed PIP joint flexion contractures, severe joint destruction requiring arthrodesis, or acute central slip ruptures (which should be managed with splinting or direct repair).

💡 Clinical Pearl: The Supple PIP Joint

The success of a distal extensor tenotomy relies entirely on the passive mobility of the PIP joint. If the PIP joint cannot be passively extended to neutral, releasing the terminal tendon will fail to correct the proximal deformity, leaving the patient with persistent PIP flexion and a newly created extensor lag at the DIP joint.

Surgical Technique: Distal Extensor Tenotomy

The procedure is typically performed under local anesthesia with a digital block, allowing for intraoperative assessment of active motion and tensioning.

1. Incision and Exposure:
   • Make a dorsal transverse or oblique incision over the distal third of the middle phalanx.
   • Carefully dissect through the subcutaneous tissue to expose the terminal extensor tendon just proximal to the DIP joint. Preserve the dorsal sensory branches.
2. The Oblique Tenotomy:
   • Identify the terminal extensor tendon.
   • Divide this tendon obliquely. An oblique division is biomechanically superior to a transverse cut because it enables the tendon to lengthen while remaining partially in apposition after the DIP joint is flexed. This partial apposition provides a scaffold for healing and prevents a complete loss of terminal extension.
3. Controlled Articular Stretching:
   • Once the tendon is divided, carefully stretch the DIP joint into flexion.
   • Assess the resting posture of the digit. The PIP joint should now rest in greater extension, and the DIP joint should rest in slight flexion.
4. Wound Closure:
   • Do not suture the extensor tendon. The goal is controlled lengthening through secondary healing.
   • Close the skin with non-absorbable monofilament sutures (e.g., 5-0 nylon).

⚠️ Surgical Warning: Iatrogenic Mallet Deformity

When stretching the DIP joint into flexion following the tenotomy, apply gentle, controlled force. Uncommonly, the extensor mechanism may become overstretched, resulting in a complete loss of terminal extension—an iatrogenic mallet deformity. If this occurs, immediate postoperative splinting of the DIP joint in extension is mandatory.

Postoperative Protocol

The postoperative rehabilitation protocol is designed to encourage immediate dynamic remodeling of the extensor apparatus.

• Early Motion: Begin active range of motion (ROM) exercises within the next several days. Ensure that active motion is carried out by the patient to prevent adhesions and to encourage the proximal migration of the lateral bands.
• Splinting: Routine splinting is generally avoided to promote motion. However, splint only if there is evidence of an iatrogenic mallet deformity, in which case the DIP joint should be splinted in neutral extension for 4 to 6 weeks while allowing full PIP joint motion.

Proximal Interphalangeal Joint Arthroplasty versus Arthrodesis

When interphalangeal joints are destroyed by osteoarthritis, rheumatoid arthritis, or post-traumatic arthropathy, the surgeon must choose between motion-preserving arthroplasty and stability-providing arthrodesis. This decision is highly nuanced and depends heavily on the specific digit involved, the patient's functional demands, and the integrity of the surrounding soft tissues.

Biomechanical Considerations by Digit

The hand operates as an asymmetric functional unit. The radial digits (thumb, index, and long fingers) are primarily responsible for precision handling and lateral key pinch, whereas the ulnar digits (ring and small fingers) are responsible for power grip.

During lateral key pinch, immense radial-to-ulnar shear forces are applied to the index finger PIP joint. Motion-preserving implants generally lack the intrinsic lateral stability required to withstand these forces over time, leading to early catastrophic failure. Conversely, the ulnar digits experience primarily flexion-extension forces during power grip, making them highly amenable to arthroplasty.

• Index Finger: Arthrodesis is the undisputed gold standard.
• Middle, Ring, and Small Fingers: PIP joint arthroplasty is highly satisfactory and often the procedure of choice.
• DIP and Thumb IP Joints: Arthroplasty of these joints is rarely necessary. Arthroplasty here results in severely limited motion, whereas function after arthrodesis is highly predictable, durable, and functionally satisfactory.
• Multiple Joints: Metacarpophalangeal (MCP) joint and PIP joint arthroplasties of the same finger are rarely indicated, as the kinematic chain becomes profoundly unstable.

Flexible Silicone Implant Arthroplasty

Silicone interpositional arthroplasty, pioneered by Swanson, remains the benchmark against which all other PIP joint arthroplasties are measured. The implant acts as a dynamic spacer, maintaining joint alignment while a fibrous pseudocapsule forms around it.

The Volar Approach (Schneider Technique)

Historically, silicone arthroplasty was performed via a dorsal approach, which required splitting or tenotomizing the central slip. This often led to postoperative extensor lags and prolonged rehabilitation.

In a landmark review, Lin, Wyrick, and Stern reported on 69 proximal interphalangeal silicone arthroplasties, highlighting the superiority of the anterior (volar) approach described by Schneider.
* Central Slip Preservation: The volar approach completely preserves the extensor central slip, allowing for immediate, early active motion without the risk of an extensor lag.
* Outcomes: Pain relief was achieved in 67 of the 69 patients.
* Limitations: The study noted that coronal plane deformities (e.g., severe ulnar or radial deviation) were not easily corrected with silicone implants. Furthermore, total arc of motion was not significantly improved postoperatively; rather, the arc of motion was shifted to a more functional, pain-free range.

Surface Replacement Arthroplasty

Alternative arthroplasty implants continue to evolve with variable success. Surface replacement arthroplasty devices are generally two-piece constructs (often utilizing metal-on-polyethylene or pyrocarbon) designed to anatomically replace the normal joint surfaces.

• Theoretical Advantages: Features common to these devices include minimal bone resection, recreation of the anatomic center of rotation, and preservation of the collateral ligaments and soft tissues.
• Clinical Reality: Despite these intuitive biomechanical advantages, surface replacements have categorically not proven superior to flexible silicone implant arthroplasty. Complications such as dislocations, implant squeaking, subsidence, loosening, and high revision rates are not uncommon.

The Pelligrini and Burton Study

The high failure rate of articulated implants was starkly highlighted by Pelligrini and Burton, who compared the results of arthroplasty and arthrodesis in 43 PIP joints.
* Cemented Articulated Devices: All cemented arthroplasty devices in their series failed at an average of 2.25 years after surgery.
* Silicone Implants: None of the flexible silicone interposition arthroplasties in the ulnar digits required revision, though progressive bone resorption (silicone synovitis/osteolysis) was evident radiographically adjacent to the implant over time.
* Conclusion: They concluded that no currently available cemented articulated device provides adequate lateral stability in the radial PIP joints. Consequently, arthrodesis remains their procedure of choice for the index finger—and occasionally the long finger—when osteoarthritic involvement interferes with lateral pinch.

💡 Clinical Pearl: Implant Selection

When counseling a patient with index finger PIP osteoarthritis, the surgeon must be unequivocal: an implant will likely fail under the stress of key pinch. Arthrodesis at 40 degrees of flexion provides a stable, pain-free post that will last a lifetime. Reserve silicone arthroplasty for the ulnar digits where power grip and conformability are paramount.

Volar Plate Interposition Arthroplasty

For selected individuals, the proximal interphalangeal joint volar plate may be utilized as an autologous interposition arthroplasty. This biological alternative is particularly useful for younger patients, manual laborers who require motion but would rapidly destroy a silicone implant, or patients who have strict contraindications to nonbiological implants.

• Technique Overview: The procedure involves releasing the collateral ligaments, resecting the osteophytes and the articular surface of the proximal phalanx, and advancing the volar plate dorsally over the resected bone end, securing it to the dorsal neck of the proximal phalanx.
• Outcomes: Although technically demanding, small patient series evaluating PIP joint volar plate arthroplasty have reported excellent pain reduction and the maintenance of preoperative strength and motion. Because it utilizes autologous tissue, there is no risk of implant fracture, squeaking, or silicone synovitis.

Arthrodesis of the Interphalangeal Joints

When arthroplasty is contraindicated, arthrodesis provides a reliable, definitive solution for pain relief and stability.

• Index PIP Joint: Fused at approximately 40 degrees of flexion to optimize lateral pinch with the thumb.
• Middle PIP Joint: Fused at 45 degrees.
• Ring PIP Joint: Fused at 50 degrees.
• Small PIP Joint: Fused at 55 degrees to facilitate tight power grip.
• DIP Joints: Fused at 0 to 10 degrees of flexion. As noted previously, DIP joint arthroplasty is rarely indicated due to poor functional gains; arthrodesis provides excellent, predictable outcomes.

Fixation techniques vary and may include crossed Kirschner wires, intra-osseous wiring (e.g., 90-90 wiring), headless compression screws, or dorsal tension band plating. The choice of fixation is dictated by bone quality and surgeon preference, but the biological principles of meticulous cartilage resection and rigid compression remain universal.

Conclusion

The surgical management of interphalangeal joint pathology requires a highly individualized approach. For the correction of mild, supple boutonnière deformities, the distal extensor tenotomy offers an elegant biomechanical solution to restore DIP joint flexion without the need for complex reconstruction.

In the realm of joint destruction, the dichotomy between arthroplasty and arthrodesis is dictated by the digit's role in the kinematic chain. While modern surface replacements offer theoretical anatomic advantages, flexible silicone arthroplasty via a volar approach remains the most reliable motion-preserving procedure for the ulnar digits. For the index finger, where the immense shear forces of lateral pinch guarantee the eventual failure of any current implant, arthrodesis remains the undisputed gold standard, providing patients with a stable, pain-free, and highly functional digit.