Proximal Tibial Resection for Bone Tumor and Prosthetic Reconstruction Combined with Medial Gastrocnemius Flap.

Background: Primary bone tumors frequently occur in the proximal tibia, ranking as the second most common location after the distal femur¹. Challenges to treatment include the proximity of neurovascular structures, limited soft-tissue coverage, compromised knee extension, and postoperative complications^1-8. The present video article describes proximal tibial resection for the treatment of a bone tumor and prosthetic reconstruction combined with a medial gastrocnemius flap.

Description: Proximal tibial resection is performed with use of an anteromedial approach. After defining the resection level, the tumor is removed en bloc with wide free margins. Reconstruction is performed with use of a megaprosthesis, and the medial gastrocnemius flap is utilized for covering the prosthesis and for reconstruction of the extensor apparatus.

Alternatives: Osteoarticular allografts and allograft-prosthesis composites allow restoration of bone stock and direct biological reattachment of host tendons, ligaments, and capsule. Autografting is performed using the fibula as a donor site. Custom-made implants can be designed according to the patient's anatomy. Amputation should be considered when the neurovascular bundle is widely involved by the tumor.

Rationale: In contrast to alternative treatments, megaprosthetic reconstructions offer several advantages: technical simplicity, immediate weight-bearing, and shorter immobilization. Additionally, megaprostheses do not carry the risk of allograft-related complications, such as nonunion, fracture, subchondral collapse, articular cartilage degeneration, and instability.

Expected outcomes: Patients with metallic endoprostheses demonstrate lower rates of complications and amputation, as well as higher patient survival rates, compared with those treated with allograft reconstructions^7,9,10. The advancements in technology and design since 1977 have contributed to reduced mechanical stress at the bone-prosthesis interface and decreased rates of mechanical or structural failure^3,11,12. However, despite advancements in design, proximal tibial prosthetic reconstructions continue to exhibit the least favorable outcomes and function among all limb-salvage procedures, accompanied by the highest rate of complications^1,9-11. Studies report survival rates ranging from 45% to 82% at 5 years and 45% to 78% at 10 years^1,13, with rates of revision for infection and loosening ranging from 40% at 5 years to 73% at 15 years^1,10,13. Various techniques are utilized for attaching the extensor mechanism of the knee and providing coverage for proximal tibial reconstructions^7,8,10,14,15. Various studies have emphasized the importance of direct attachment of the extensor mechanism to the megaprosthesis, which facilitates initial mechanical stability crucial for healing and scarring^7,10,16. Pedicled muscle flaps, particularly the medial or lateral gastrocnemius, have commonly been utilized to supply blood to aid wound healing and to biologically reconstruct the extensor mechanism^7-9. Despite some patients experiencing increased extension lag, gradual improvement in function¹⁷ was observed during follow-up. In our experience with 225 proximal tibial resections, survival of megaprosthetic reconstructions was 82% and 78% at 5 and 10 years, respectively, without any difference between the use of a fixed versus rotating hinge¹. However, the rate of good or excellent functional outcomes, as measured according to the Musculoskeletal Tumor Society (MSTS) system¹⁷, was significantly higher with use of a rotating hinge. Infection was, as expected, the most frequent complication, occurring in 27 patients (12%), followed by aseptic loosening (13 patients, 6%), rupture of the extensor mechanism (6 patients, 3%), breakage of the prostheses (4 patients, 1.6%), and wound dehiscence (4 patients, 1.6%)¹.

Important tips: Preoperative evaluation and imaging. Perform a thorough history and physical examination, assess for evidence of a syndrome or family history, and utilize imaging studies to evaluate the tumor.Patient positioning and incision planning. Position the patient supine to ensure full access to the proximal tibia. Prepare and drape the patient; center the incision on the mass through an anteromedial approach including the biopsy tract and perform a longitudinal incision.Harvest the gastrocnemius flap. After identifying the proximal vessels, proceed to dissect the gastrocnemius flap, which is typically straightforward and rapid (even after tumor removal).Dissection of soft tissue and definition of the tumor resection margin. Protect and retract the medial gastrocnemius flap and then isolate and protect the popliteal and posterior tibial vessels.Deep dissection and articular resection. If staging and preoperative planning indicated no evidence of tumor inside the joint, intra-articular knee resection should be conducted. Arthrotomy is performed through a parapatellar approach, and the cruciate ligaments are cut close to the femoral attachment.Tumor removal. After the specimen with the tumor is freed circumferentially, identify the osteotomy level and dissect any remaining structures connected with proximal tibia to remove the entire tumor.Inspection and hemostasis. Evaluate for hemostasis and send the specimen for pathologic analysis. Prepare for the reconstructive phase and close the surgical site.Proximal tibial reconstruction with a modular endoprosthesis. Tumor mega-endoprostheses are appealing because of their versatility, ability to yield favorable functional outcomes, ability to allow immediate weight-bearing, and possible cost-effectiveness.Reconstruction of the extensor mechanism. The commonly utilized approach involves employing a medial gastrocnemius flap.Monitoring and postoperative care. Postoperative monitoring is crucial. A strict rehabilitation protocol with immobilization in full extension for 4 weeks followed by progressive mobilization for 3 months is critical to guarantee better functional results.

Acronyms and abbreviations: GCT = giant cell tumorHIV = human immunodeficiency virusHBV = hepatitis B virusHCV = hepatitis C virusf-up = follow-upCT = computed tomographyMRI = magnetic resonance imagingPET = positron emission tomographySUV = standardized uptake valueCht (ISG/OS2) = chemotherapyMTX-HD = high-dose methotrexateCDP = cisplatinADM = doxorubicinKMFTR = Kotz Modular Femur-Tibia Reconstruction systemHMRS = Howmedica Modular Resection SystemGMRS = Global Modular Replacement System.