Total Ankle Arthroplasty: Indications, Survivorship, and the Modern Era

Visual Element: An anatomical diagram comparing "Ankle Arthrodesis" (screws crossing the joint) vs "Total Ankle Arthroplasty" (implant in situ), highlighting the preserved subtalar joint motion in the TAR group.

The Renaissance of the Ankle

For decades, the ankle was the "forgotten joint" of arthroplasty. While hip and knee replacements became the surgeries of the century, ankle arthritis was largely managed with a single, definitive hammer: Arthrodesis (Fusion).

Fusion is a reliable operation. It eliminates pain by eliminating motion. But the cost is high: a rigid ankle alters gait mechanics, impairs walking on uneven ground, and places catastrophic stress on the adjacent joints (subtalar and talonavicular), leading to adjacent segment arthritis in nearly 100% of patients within 10-20 years.

Total Ankle Arthroplasty (TAR) promises to solve this by preserving motion. But can it deliver? After a rocky history of early failures, modern TAR has entered a golden era.

A History of Failure (and Redemption)

To understand modern TAR, one must understand why earlier versions failed.

1st Generation (1970s)

• Design: Constrained, cemented designs (like upside-down hip replacements).
• Failure: Massive osteolysis and loosening because the ankle could not handle the rotational forces. Failure rates >50%.

2nd Generation (1980s-90s)

• Design: Less constrained, but often required massive bone resection.
• Failure: Subsidence and instability.

3rd & 4th Generation (Modern)

• Design: Anatomic resurfacing, minimal bone resection, uncemented (biologic fixation), mobile bearing (mostly outside US) or fixed bearing (US).
• Success: Survivorship now rivals early hip/knee data.

Modern Implant Design Features

Current implants (e.g., Infinity, STAR, Vantage) share key philosophies:

1. Bone Sparing: Resections are minimal, preserving the malleoli and talar body. This keeps the door open for fusion if the implant fails ("burning bridges" is a thing of the past).
2. Biologic Fixation: Porous titanium or plasma spray coatings encourage rapid bone ingrowth, eliminating the need for cement.
3. Instrumentation: Patient-specific instrumentation (PSI) with 3D printed cutting blocks has revolutionized alignment accuracy.

Visual Element: A chart showing the "Survival Curve" of modern TARs from the AOANJRR, showing ~85-90% survival at 10 years.

Indications: The "Goldilocks" Patient

Patient selection in TAR is far more critical than in TKA. The envelope of success is narrower.

The Ideal Candidate

• Age: Older (>50-60 years), though indications are lowering.
• Body Habitus: Normal BMI (Obesity exerts exponential force on the small talar surface area).
• Demand: Low to moderate demand (Golf, walking, cycling are OK; Marathon running is not).
• Alignment: Correctable deformity (<15° varus/valgus).
• Pathology: Post-traumatic arthritis (most common), Rheumatoid arthritis (excellent candidates due to low demand), Haemophilia.

Absolute Contraindications

• Active Infection.
• Charcot Neuroarthropathy: The bone quality and sensory loss guarantee failure.
• Severe Avascular Necrosis (AVN): The talus collapses under the implant (though custom talar body replacements exist).
• Neuromuscular Imbalance: Drop foot or spasticity will rock the implant loose.
• Poor Soft Tissue Envelope: Previous flaps or scarring.

Surgical Trap: The Equinus Contracture. Failing to correct a tight gastrocnemius/achilles complex will lead to anterior impingement and early loosening. Almost all TARs require a concomitant gastroc release or TAL.

Outcomes: TAR vs. Arthrodesis

The "TAR vs. Fusion" debate is settled not by one beating the other, but by understanding they serve different goals.

Pain Relief

• Fusion: Slightly superior reliability for complete pain elimination.
• TAR: Good pain relief, but "awareness" of the joint often persists.

Function and Gait

• TAR: Significantly superior. Patients walk faster, with a more symmetrical gait, and can manage stairs and slopes better.
• Fusion: Patients often walk with a distinct limp and struggle on uneven ground.

Survivorship

• Fusion: Lifetime solution (usually). Non-union rate is ~5-10%.
• TAR: 5-year survival >90%. 10-year survival ~80-85%.
  • Note: A "failed" TAR can often be revised to another TAR or converted to a fusion.

Evidence Corner: The TARVA Trial (Total Ankle Replacement Versus Arthrodesis) is a landmark RCT comparing the two. Results showed that both groups improved significantly, but TAR had better functional PROMs at the cost of higher complication rates.

Complications and Management

1. Wound Healing: The anterior ankle skin is precarious (angiosome watershed). Careful handling is mandatory.
2. Malleolar Fracture: Intra-operative fracture occurs in ~5-10% of cases due to saw cuts. Must be fixed immediately.
3. Gutter Impingement: Bone overgrowth in the medial/lateral gutters causes pain. Requires arthroscopic debridement.
4. Cysts: Peri-prosthetic cysts are common (seen on X-ray). Most are benign, but large ones indicate particle disease or instability.

Conclusion

Total Ankle Arthroplasty has graduated from "experimental" to "established." It is no longer a question of if it works, but who it works for.

For the active, older patient who values motion and wants to protect their other joints, TAR is an excellent choice. For the young manual labourer or the patient with severe deformity, fusion remains the champion. As surgeons, having both tools in our arsenal—and knowing when to use which—is the key to mastering ankle arthritis.

References

1. Zaidi R, et al. "Total ankle replacement versus ankle arthrodesis (TARVA): a randomised controlled trial." Annals of Internal Medicine. 2023.
2. Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Annual Report 2024.
3. Clough T, et al. "The evolution of total ankle arthroplasty." Bone & Joint Journal. 2020.