To correct deformity in TKA, the angle of the distal femoral and tibial cuts can be achieved through the use of intramedullary or extramedullary alignment systems, computer-assisted surgery (CAS), or patient-specific instrumentation (PSI) . Intramedullary and extramedullary systems are dependent on the degree to which each guide rod approximates the anatomic axes of the femur and tibia. Intramedullary alignment of the femur in TKA has been generally accepted as superior to extramedullary alignment, as the femoral shaft is difficult to locate through a large, surrounding soft tissue envelope. Additionally, femoral extramedullary alignment systems require estimation of the center of the femoral head. Radiographic skin markers or intraoperative fluoroscopy often can be used; however, bulky surgical drapes and obesity may present problems. A long-term follow-up study by Meding et al. found overall alignment was not as precise using the extramedullary system, but found no significant statistical difference in postoperative Knee Society scores, pain, or stair-climbing abilities of patients between intramedullary or extramedullary alignment guide use [16].

On the tibial side, there is considerable debate as to whether intramedullary or extramedullary alignment is superior. Tibial intramedullary alignment devices are based on the assumption that the angle between the anatomical and the mechanical axis is not significantly different from zero in either the coronal or sagittal planes [17–21]. This chapter seeks to define the indications and emphasize the contraindications for intramedullary alignment of the tibia in revision total knee arthroplasty. Furthermore, specific case examples are reviewed that illustrate the pitfalls of and alternatives to intramedullary alignment of the tibia in total knee arthroplasty.

In our previous report, 44 adult cadaveric tibiae without obvious clinical deformity were harvested [22]. Using a stepped drill bit, the proximal medullary canal was entered anterior to the tibial attachment of the anterior cruciate ligament. The starting hole was oversized with a rasp, and a long 8-mm diameter solid intramedullary fluted guide rod was passed down the medullary canal until it was firmly engaged distally. The bone cut was made referencing off the intramedullary cutting jig. Anteroposterior and lateral radiographs were taken, and the anatomical, mechanical, and guide rod axes were assessed on each radiograph. The accuracy of the guide rod was assessed by measuring how closely the guide rod axis approximated the anatomic and mechanical axis in both the anteroposterior and lateral planes. The difference between the anatomic axis and the guide rod axis was measured and defined as the axis angle.

Observations obtained from this cadaveric study revealed that certain deformities and clinical situations would preclude the use of intramedullary alignment of the tibia in total knee arthroplasty. The clinician needs to be aware of the contraindications and alternatives to intramedullary alignment of the tibia in total knee arthroplasty.

Alternatives to intramedullary and extramedullary alignment systems include CAS and PSI . These newer technologies aim to improve limb alignment and component position, with the goal of decreasing overall operative time and instrument trays required and avoiding intramedullary instrumentation. Studies assessing CAS have been mixed, with some meta-analyses finding an improvement in mechanical axis and component orientation, while others have found no significant difference in alignment or functional outcomes [23–27]. Drawbacks of CAS may be increased cost, difficulty with intraoperative landmark registration, increased setup and intraoperative time, and pin site loosening or even fracture. PSI, which utilizes a preoperative CT or MRI to create personalized cutting blocks based on a patient’s anatomy, has failed to show any significant clinical or radiographic benefit over standard intramedullary alignment in several studies and may be associated with an increased cost [28–30]. However, both computer-assisted surgery and PSI may reduce the number of outliers in regard to mechanical axis and may be useful in cases with severe deformity or when intramedullary instrumentation is not possible. In addition, Nam et al. studied a handheld, accelerometer-based navigation device and compared this to extramedullary alignment guides. They found that, compared to extramedullary guides, use of the handheld device decreased outliers in tibial component alignment in TKA [31].