Gap Arthroplasty: Understanding This Joint Surgery, Its Uses, and Outcomes

What is gap arthroplasty?

Gap arthroplasty is a surgical procedure involving the removal of bone from an articulating joint surface to create a space, or "gap," thereby preventing bone-on-bone contact and allowing for the formation of fibrous tissue within the created void.

Understanding Joint Arthroplasty

Arthroplasty, derived from the Greek words "arthron" (joint) and "plassein" (to form or mold), broadly refers to any surgical procedure that reconstructs or reforms a joint. The primary goal of arthroplasty is to restore joint function, reduce pain, and improve range of motion in joints affected by conditions like arthritis, trauma, or congenital deformities. While modern arthroplasty often involves the implantation of prosthetic components (e.g., total knee or hip replacement), historical and specific contemporary approaches utilize different techniques, one of which is gap arthroplasty.

The Concept of Gap Arthroplasty

Gap arthroplasty is a simpler, less invasive form of joint reconstruction compared to total joint replacement. Its fundamental principle is to create a deliberate space between two formerly articulating bone surfaces to prevent their direct contact and subsequent friction, pain, or fusion (ankylosis).

• Historical Context: This technique predates modern prosthetic joint replacements. In the early 20th century, before advanced biomaterials and surgical techniques for implants were developed, gap arthroplasty was a common approach to address severe joint pain and immobility. It was a pioneering effort to restore some degree of movement where none existed.
• Mechanism: The surgeon removes a segment of bone from one or both sides of the joint, effectively widening the joint space. This void is then allowed to fill with fibrous connective tissue, which forms a pseudoarthrosis (false joint). This fibrous tissue, while not as robust or smooth as articular cartilage, can provide a degree of movement and reduce pain by preventing direct bone-on-bone grinding.

Indications for Gap Arthroplasty

While largely superseded by more advanced joint replacement techniques for major weight-bearing joints, gap arthroplasty still holds specific indications in modern orthopedic and oral-maxillofacial surgery.

• Temporomandibular Joint (TMJ) Ankylosis: One of the most common current applications is in the treatment of TMJ ankylosis, where the jaw joint has fused, severely limiting opening and function. Creating a gap allows for improved jaw mobility.
• Elbow Joint Contractures: In cases of severe elbow contractures or ankylosis, particularly when prosthetic options are not ideal due to infection or patient-specific factors, gap arthroplasty can restore some functional range of motion.
• Infected Joints: In situations where a joint is severely infected, making prosthetic implantation risky, gap arthroplasty (or a similar resection arthroplasty) can be performed as a salvage procedure to remove infected bone and provide pain relief and some mobility.
• Resource-Limited Settings: In areas where advanced surgical facilities or prosthetic implants are not readily available, gap arthroplasty may be a pragmatic solution for severe joint conditions.
• Pediatric Cases: Sometimes considered in growing children where prosthetic implants might interfere with bone growth or require multiple revisions.

The Surgical Procedure

The specifics of gap arthroplasty vary depending on the joint involved, but the core principle remains consistent.

• Key Steps:
  1. Incision: An incision is made to expose the affected joint.
  2. Bone Resection: The surgeon carefully removes a precise amount of bone from the articulating surfaces. The amount removed is critical: enough to prevent re-fusion but not so much as to destabilize the joint excessively.
  3. Gap Creation: The goal is to create a clear, measurable space between the remaining bone ends.
  4. Closure: The surgical site is then closed. No prosthetic implants are typically inserted into the gap itself.
• Materials: Unlike total joint replacement, gap arthroplasty does not involve the implantation of artificial materials within the joint space. The "new" joint surface is formed by the patient's own fibrous connective tissue that develops in the created gap. Sometimes, interpositional materials like fascia, fat, or muscle flaps might be placed in the gap to encourage fibrous tissue formation and prevent re-fusion, blurring the lines with interposition arthroplasty.

Advantages and Disadvantages

Like any surgical procedure, gap arthroplasty has distinct pros and cons.

• Advantages:
  • Simplicity: Generally a less complex procedure than total joint replacement.
  • No Implant Failure: Eliminates risks associated with prosthetic implant wear, loosening, or infection.
  • Salvage Option: Can be a viable option in cases of severe infection or when other options are contraindicated.
  • Cost-Effective: Typically less expensive due to the absence of costly prosthetic components.
• Disadvantages:
  • Limited Motion and Stability: The fibrous tissue that forms is not as smooth or durable as natural cartilage or prosthetic implants, often resulting in less range of motion and potentially less stability compared to a healthy joint or a successful total joint replacement.
  • Pain Persistence: While pain is often reduced, it may not be entirely eliminated, and some patients may experience chronic discomfort.
  • Risk of Re-Ankylosis: There is a risk that the bone ends may re-fuse, especially if insufficient bone is removed or if proper rehabilitation is not followed.
  • Limb Length Discrepancy: In weight-bearing joints like the hip (e.g., Girdlestone procedure), significant bone removal can lead to limb shortening and gait abnormalities.

Rehabilitation and Recovery

Post-operative rehabilitation is crucial for the success of gap arthroplasty, particularly to prevent re-ankylosis and maximize the development of the fibrous pseudoarthrosis.

• Early Mobilization: Often, early and consistent passive and active range of motion exercises are initiated to encourage the formation of a mobile fibrous joint and prevent the re-fusion of the bone ends.
• Physical Therapy: A structured physical therapy program is essential to strengthen surrounding muscles, improve joint stability, and optimize functional outcomes.
• Pain Management: Managing post-operative pain is vital to facilitate adherence to the rehabilitation protocol.

Modern Context and Alternatives

In contemporary orthopedic practice, gap arthroplasty's role is quite specialized.

• Current Role: It is primarily reserved for specific joints (like the TMJ) or as a salvage procedure in complex cases where prosthetic options are not feasible or have failed.
• Alternatives:
  • Total Joint Arthroplasty (Replacement): For major joints (hip, knee, shoulder), total joint replacement with prosthetic implants is the gold standard, offering superior pain relief, range of motion, and durability.
  • Hemiarthroplasty: Replacement of only one side of the joint (e.g., femoral head replacement in the hip).
  • Interposition Arthroplasty: Similar to gap arthroplasty, but a biological (e.g., fascia, muscle) or synthetic material is intentionally placed within the gap to act as a cushion and prevent bone-on-bone contact, encouraging a smoother pseudoarthrosis.

Conclusion

Gap arthroplasty, a historical yet still relevant surgical technique, addresses severe joint dysfunction by creating a space between articulating bones to allow for fibrous tissue formation and restore limited mobility. While its applications are now largely niche, particularly in the TMJ and as a salvage option for infected joints, understanding this procedure provides valuable insight into the evolution of joint surgery and the diverse approaches employed to alleviate pain and improve function in compromised joints. As fitness educators, recognizing the limitations and unique outcomes of such procedures is vital when working with individuals who have undergone these interventions, ensuring rehabilitation strategies are tailored to the specific biomechanical realities of a gap arthroplasty.