Proximal Tibial Resection and Reconstruction

Robert K. Heck Jr, MD, FAAOS

Patrick C. Toy, MD, FAAOS

Dr. Toy or an immediate family member has received royalties from Innomed. Neither Dr. Heck nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.

ABSTRACT

The proximal tibia is second to the distal femur as the most common site of primary bone sarcomas. Oncologic cure is most important, and preservation of function is of secondary importance; however, there are certain challenges unique to this particular anatomic location when considering treatment and outcomes. Limb salvage of the proximal tibia is considered a reasonable option when the tumor can be resected with negative margins and the appropriate neurovascular structures, adequate distal tibia, and soft-tissue coverage options exist. Reconstruction after wide resection of proximal tibia sarcomas is associated with high complication rates. The proximal tibia can be replaced with a tumor prosthesis, or an allograft-prosthesis composite, or an allograft. Each of these options is associated with advantages and complications specific to each type of reconstruction. Most patients with proximal tibia sarcomas are limb salvage candidates and are able to retain a functional limb.

INTRODUCTION

The proximal tibia is second to the distal femur as the most common site of primary bone sarcomas. As with any patient who presents with a neoplastic process, oncologic cure is the priority, with preservation of function being of secondary importance. However, the proximal tibia presents challenges unique to this particular anatomic location when considering an adequate resection, subsequent limb salvage, and function. Although amputation can be performed with ease and result in negative oncologic margins, the advent of adjuvant chemotherapy has provided an opportunity to consider limb salvage as a viable option. Successful limb salvage is difficult because of factors in this anatomic location that are independent of the tumor characteristics and location. These factors include the superficial location of the bone, the difficulty with adequate soft-tissue coverage after resection, preservation of neurovascular structures, and reconstruction of the extensor mechanism of the knee.

RESECTION

Evaluation

A standard thorough evaluation and staging should be performed on any patient presenting with a new bone lesion in the proximal tibia. Plain radiographs in combination with history and physical examination often provide clues that allow the oncologic surgeon to develop a concise differential diagnosis. Axial imaging, such as MRI, provides detail to the extent and location of the tumor within the tibia. Soft-tissue extension also can be evaluated, and the best location to perform a biopsy can be determined.

Limb Salvage Versus Amputation

Limb salvage of the proximal tibia is considered a reasonable option when the tumor can be resected with negative margins and the appropriate neurovascular structures, adequate distal tibia, and soft-tissue coverage remain. Limb salvage techniques with wide resection should be considered for some benign aggressive tumors (eg, giant cell tumors), low-grade bone sarcomas (eg, low-grade osteosarcoma), and most high-grade bone sarcomas. In the case of high-grade bone sarcomas, the timing of
resection depends on the treatment protocol involving neoadjuvant chemotherapy. Factors that determine limb salvage feasibility include the patient’s ability to tolerate and recover from a surgical procedure, the location of the biopsy site, the extraosseous extension and potential involvement of the neurovascular structures, the ability to reconstruct the extensor mechanism, soft-tissue coverage, and the patient’s functional demands.

Negative margins are technically easier to achieve with amputation. Amputation is considered a better option than limb salvage in the case of presentation with pathologic fracture, a poorly placed biopsy site, soft-tissue compromise, and infection.

Skeletally immature patients present a challenge because the proximal tibial physis is usually sacrificed during the resection. Expandable prostheses have been introduced as a potential solution to minimize problems related to limb-length discrepancy. If oncologically possible, an amputation in a skeletally immature patient should be completed at the level of the knee joint to preserve the distal femoral physis.

Potential Complications

The surgeon performing the biopsy should follow proper techniques to avoid oncologic compromise, and often should be the same surgeon who will be involved in the definitive resection. An errantly placed biopsy incision may result in an inability to perform successful resection if vital structures (eg, patellar tendon, joint, neurovascular structures) are contaminated. Because the anteromedial aspect of the tibia is subcutaneous, the biopsy should be in this location whenever possible.

Compared with other anatomic sites where sarcomas occur relatively frequently, the proximal tibia is in a superficial location. This difference has been thought to be a significant factor in the higher rate of infection following reconstruction and potentially compromises limb retention. The risk of infection is further increased when adjuvant chemotherapy is part of the treatment protocol. Rotation of the medial gastrocnemius flap anteriorly has become a routine part of reconstruction to minimize this problem. This flap also serves to help anchor the patellar tendon to allow restoration of the extensor mechanism. The union achieved between the patellar tendon and rotational flap will eventually allow some active extension at the knee, but extensor lag is common.

Technique

A longitudinal incision that ellipses the biopsy scar is made on the tibia, most commonly anteromedially (Figure 1). Large fasciocutaneous flaps are raised both medially and laterally, and the posterior neurovascular structures are evaluated. The trifurcation of the popliteus artery into the anterior tibial artery, the posterior tibial artery, and the peroneal artery begins at the inferior border of the popliteus muscle. The popliteus muscle covers the posterior surface of the tibia and often acts as an effective barrier to posterior extension of the tumor. As a result, the neurovascular structures often are more easily preserved. The anterior tibial artery and vein pass anteriorly through the interosseous membrane and can be sacrificed in the resection, if necessary, without vascular compromise to the limb distally. The posterior tibial vessels must be preserved for limb viability.

FIGURE 1 Intraoperative photographs.

A, The incision is designed to ellipse around the biopsy track on the anteromedial aspect of the proximal tibia. B, The plane between the tumor and the posterior neurovascular structures is developed through a medial approach. C, Laterally, the peroneal nerve is dissected out, leaving a cuff of muscle to serve as a margin around the proximal tibia. D, The patellar tendon is released from its insertion, and a circumferential capsulotomy is made. The final step of the resection is to osteotomize the tibia distal to the tumor.

For intra-articular resections, the ligaments of the knee are divided and the patellar tendon is released from the tibial tubercle without contamination. The level of the tibial diaphyseal osteotomy is determined based on preoperative MRI. The proximal tibiofibular joint is resected as part of the specimen, along with a short segment of proximal fibula. The common peroneal nerve rarely is involved with the tumor and must be identified and protected. The specimen is delivered en bloc and evaluated by a pathologist to determine margin status.

If adequate margins are thought to be obtainable by preoperative MRI studies, an attempt can be made to preserve the knee joint. An intercalary resection can be performed by making a second osteotomy just distal to the proximal tibial articular surface rather than a circumferential capsulotomy as described earlier. Intercalary reconstruction can be performed using a size-matched proximal tibia with its associated patellar tendon allograft. When technically possible and safe from an oncologic standpoint, this technique can be used in hopes of achieving a more durable and better-functioning reconstruction.

RECONSTRUCTION

Reconstruction after wide resection of proximal tibia sarcomas can be extremely challenging. Historically, complication rates have been relatively high in this location compared with oncologic reconstructions in other locations. High complication rates are due to two major factors. First, soft-tissue coverage in this area usually is very tenuous after wide resection of the proximal tibia. Most proximal tibia sarcomas have extension into the soft tissues. After wide resection, there is limited soft tissue available for coverage of the reconstruction. Because most of these patients also are undergoing chemotherapy, wound complications are frequent, and the risk of infection is high. However, in this setting, a deep infection can be devastating, often leading to amputation of the limb. Second, reconstruction of the knee extensor mechanism poses unique challenges. Resection of sarcomas of the proximal tibia usually requires resection of the tibial tubercle and usually a portion of the patellar tendon as well. Secure reattachment of the extensor mechanism can be difficult and frequently results in quadriceps weakness and an extensor lag. Fortunately, modern surgical techniques have helped to partially overcome some of these problems. Routine use of a gastrocnemius flap has helped to address both issues.¹^,²^,³ The gastrocnemius flap improves soft-tissue coverage and facilitates wound healing, thus decreasing the infection rate. The gastrocnemius flap also provides a biologic attachment for the patellar tendon. The proximal tibia can be replaced with an allograft, a tumor prosthesis, or an allograft-prosthesis composite (APC). Each of these options is associated with advantages as well as complications specific to each type of reconstruction. Fortunately, with modern surgical techniques, most patients are able to retain a functional limb.

Osteoarticular Allograft

One option for reconstructing the proximal tibia is by using an osteoarticular allograft. This option provides restoration of the tibial joint surface as well as attachments for the ligaments and joint capsule. A major advantage of this technique is the capability to provide a secure attachment of the extensor mechanism to the allograft patellar tendon. Another major advantage is complete preservation of the distal femur. This can be extremely important for pediatric patients in whom preservation of the distal femoral physis will minimize future limb-length discrepancy.

Osteoarticular allograft reconstruction is performed by first locating an allograft that matches the size of the tibia that will be resected. Ideally the joint surfaces should match as closely as possible. It is acceptable for the allograft joint surface to be slightly larger than that of the resected bone, but it should not be smaller. After resection of the proximal tibia, the allograft is opened onto the field. It should be cut to match the length of the resected specimen. In pediatric patients, the allograft can be cut slightly longer (1 cm) to provide some additional length to compensate for the lost physis. An attempt to gain too much length can cause injury to neurovascular structures and can increase the risk of wound-healing complications. Host knee ligaments are repaired to the allograft ligaments using nonabsorbable sutures. The diaphyseal graft-host junction is then fixed with compression plating
along the lateral surface. The patellar tendon is repaired with the knee in full extension. Care should be taken to close the wound without tension. Use of a medial gastrocnemius flap can help with soft-tissue coverage as well as with healing of the extensor mechanism. Postoperatively, the knee is usually braced in full extension for 6 weeks to protect the extensor repair. The brace is then adjusted gradually over the next 6 weeks to slowly allow progressive flexion. Touchdown weight-bearing status is recommended until there is evidence of union at the graft-host junction.

Although this technique has the potential to restore adequate knee function, complications are unfortunately frequent. Infection rates have been reported ranging from 12% to 25%.⁴^,⁵^,⁶^,⁷^,⁸^,⁹^,¹⁰^,¹¹^,¹² Risk of infection can be minimized by attention to tension-free soft-tissue closure, use of a gastrocnemius flap to improve coverage, perioperative antibiotic prophylaxis, and postoperative wound care. Fracture of bulk allografts have been reported to occur in up to 13% to 80% of cases, depending on the technique.⁷^,⁸^,¹⁰^,¹¹^,¹²^,¹³^,¹⁴ Risk of fracture can be minimized by protecting as much of the allograft as possible with metal hardware. Even with prophylactic fixation, however, subchondral fractures still are common, usually requiring treatment by placement of arthroplasty components. Finally, delayed union or nonunion of the graft-host junction is very common, occurring in 11% to 50% of cases.⁸^,¹⁰^,¹³^,¹⁴^,¹⁵ This risk can be minimized by maximizing graft-host contact and using rigid internal fixation. Primary autogenous bone grafting of the graft-host junction can be used at the index procedure; however, most patients also are undergoing intense chemotherapy regimens and complication rates remain high. Because of this, if an allograft is used, a more common approach is to use an endoprosthesis in composite, which overcomes some of the allograft limitations.

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