Endoprosthesis

Endoprosthesis

Prepared by Dr. Serkan BAYRAM

Endoprosthetic reconstruction is a cornerstone technique in musculoskeletal oncology, allowing immediate restoration of skeletal continuity and early mobilization after wide tumor resection. Modern modular megaprostheses, made of titanium or cobalt-chromium alloys, are designed for durability, functional recovery, and ease of revision. They are primarily indicated for periarticular or diaphyseal bone loss following tumor excision, failed fixation, or pathological fractures. Cemented fixation ensures immediate stability, while press-fit and porous-coated designs promote biological integration. Despite excellent limb salvage rates (>90%), complications such as infection, aseptic loosening, and mechanical failure remain challenges. Advances including silver-coated implants, expandable pediatric prostheses, and improved soft-tissue reattachment techniques continue to enhance long-term outcomes and quality of life for oncology patients.

Definition 

An endoprosthesis is a modular metallic implant used to reconstruct bone and joint defects following wide resection of primary or metastatic musculoskeletal tumors. The aim is to achieve immediate structural stability, preserve limb function, and allow early mobilization, particularly in cases where biological reconstruction (allograft or autograft) is not feasible.

Indications

• Segmental bone loss after tumor resection, particularly in the proximal humerus, distal femur, and proximal tibia.
• Periarticular destruction due to primary bone sarcomas (e.g., osteosarcoma, Ewing sarcoma) or metastatic disease.
• Reconstruction after pathological fractures or failed fixation in oncologic bone.
• Salvage after infection or mechanical failure of previous reconstruction.

Design and Components

Modern tumor prostheses are modular megaprostheses made from titanium or cobalt-chromium alloys, often with:

• Cemented or press-fit stems for fixation into the remaining diaphysis.
• Rotating hinge joints (knee and elbow) to reduce torque and wear.
• Porous-coated or hydroxyapatite collars to promote soft-tissue and bone integration.
• Expandable designs for skeletally immature patients, allowing non-invasive limb-length adjustment.

Cemented fixation offers immediate stability, while cementless (press-fit) fixation supports long-term biological fixation and easier revision.

Surgical Principles

1. Wide oncologic margins are mandatory to minimize local recurrence.
2. Preservation of neurovascular structures and soft-tissue coverage is essential.
3. Stable fixation and restoration of limb length should be achieved intraoperatively.
4. Reconstruction of muscle attachments (especially in proximal humerus and tibia) improves functional outcome.
5. Prophylactic antibiotic cement or silver-coated implants are used to reduce infection risk in high-risk cases.

Advantages

• Immediate load-bearing capability.
• Shorter operative time compared to biological reconstructions.
• Predictable early function and pain relief.
• Can be revised modularly if components wear or fracture.

Complications

• Infection (5–15%); more common in immunocompromised or irradiated patients.
• Mechanical failure (loosening, stem breakage).
• Aseptic loosening due to stress shielding.
• Periprosthetic fracture and soft-tissue failure (e.g., extensor mechanism insufficiency).

Outcomes and Prognosis

Endoprosthetic reconstructions provide excellent pain relief and limb salvage rates exceeding 90% in modern series.
Five-year implant survival is around 70–80%, depending on site and indication. Long-term durability is enhanced by improved modular designs, better fixation strategies, and multidisciplinary care.

References

1. Rizzo SE, Kenan S. Pathologic Fractures. StatPearls Publishing, 2025.
2. Fields RC et al. Management of Pathological Fractures: Current Consensus. Knee Surg Sports Traumatol Arthrosc, 2024.
3. Boussouar S et al. Tailored Approach for Appendicular Pathologic Fractures from Metastatic Bone Disease. Cancers (Basel), 2022.
4. Jeys L, Grimer R. Endoprosthetic Reconstruction After Tumor Resection. J Bone Joint Surg Br, 2019.
5. Henderson ER et al. Failure Mode Classification for Tumor Endoprostheses: An International Consensus. Clin Orthop Relat Res, 2017.

Quick Facts

Feature	Details
Purpose	Reconstruction of segmental bone or joint defects after tumor resection
Main Indications	Primary or metastatic bone tumors, failed fixation, post-infection salvage
Common Sites	Distal femur, proximal tibia, proximal humerus, proximal femur
Design Type	Modular or custom-made megaprostheses (cemented or press-fit fixation)
Expandable Prostheses	Used in skeletally immature patients to allow limb-length adjustment
Key Materials	Titanium, cobalt-chromium alloys, silver-coated or hydroxyapatite collars
Advantages	Immediate stability, early mobilization, predictable limb function
Common Complications	Infection (5–15%), aseptic loosening, mechanical failure, periprosthetic fracture
Functional Outcome	Limb salvage rate >90%; 5-year implant survival 70–80%
Preferred in	Large bone defects or periarticular resections where biological grafting is not feasible