Extra-articular Deformity

Alan K. Sutak

Matthew P. Abdel

Key Concepts

Deformities at the knee can either be intra-articular or extra-articular in nature.
Extra-articular deformities can be on either the femoral side (Figure 57.1A) or tibial side (Figure 57.1B). Moreover, they can be near the joint (Figure 57.2A) or far from the joint (Figure 57.2B). In general, deformities that are further from the joint are less likely to impact total knee surgical technique.
Preoperative planning with a long-leg standing film (Figure 57.3) is critical to understanding the deformity and type of correction needed (intra-articular correction versus osteotomy versus use of hinged total knee arthroplasty [TKA]).

If planned resection would damage the collateral ligaments on the distal femur (Figure 57.4A) or the tibial diaphyseal line (Figure 57.4B) passes outside of the tibial plateau, an extra-articular osteotomy is indicated in younger or more active patients. In elderly patients who are low demand, sacrificing the collateral ligaments and using a hinged TKA (Figure 57.5) without an osteotomy can be considered.

Figure 57.1 ▪ A, Anteroposterior (AP) knee radiograph of a 55-year-old man with a left distal femoral deformity secondary to a distal femur fracture with subsequent nonunion treated with revision open reduction and internal fixation. B, AP knee radiograph of a 51-year-old man with a right proximal tibial deformity secondary to a high tibial osteotomy completed 18 years previously.

Figure 57.2 ▪ A, AP radiograph of an 81-year-old woman with a right distal femoral deformity near the joint secondary to a distal femur fracture. B, This long-leg standing hip-knee-ankle radiograph shows a 62-year-old woman with 2 extra-articular deformities in the right femur (one far from the joint and one near the joint) secondary to spondyepiphyseal dysplasia.

Figure 57.3 ▪ This long-leg standing hip-knee-ankle radiograph reveals a significant left tibial deformity near the joint secondary to Blount disease in a 53-year-old woman. However, the overall mechanical alignment is near neutral.

Figure 57.4 ▪ If templating on standing long-leg hip-knee-ankle radiograph indicates compromise of the collateral ligaments on the femoral side (A) or the tibial diaphyseal line does not intersect the tibial plateau (B), then an osteotomy should be considered. (Redrawn with permission from Wang JW, Wang CJ. Total knee arthroplasty for arthritis of the knee with extra-articular deformity. J Bone Joint Surg Am. 2002;84-A(10):1769-1774.)

Figure 57.5 ▪ This left lateral radiograph depicts a primary hinge TKA completed in a 91-year-old woman with a significant deformity that would have required an osteotomy.

Regardless of technique, component position should be correct in all planes, and the joint line should be perpendicular to the mechanical axis (Figure 57.6).

The focus of this chapter will be on nonosteotomy solutions.

Figure 57.6 ▪ With adequate planning and use of extramedullary alignment and intraoperative fluoroscopy, the patient from Figure 57.3 underwent an unremarkable left primary TKA without an osteotomy. The postoperative long-leg standing hip-knee-ankle radiograph reveals a neutral mechanical alignment with a joint line that is perpendicular to the mechanical axis.

Sterile Instruments and Implants

Instruments

Standard TKA instrumentation
Appropriate tools and instruments to remove prior hardware and/or implants, including diamond-cutting burrs and wheels and broken screw removal set
Intraoperative radiographs or fluoroscopy to verify alignment
Consider use of the following:
- Extramedullary guide rods for alignment (Figure 57.7)
- Handheld navigation (Figure 57.8)
- Computer-assisted/robotically assisted surgery (Figure 57.9)

Implants

Implants with varying levels of constraint should be available during all cases, from posterior-stabilized to varus-valgus constraint to rotating-hinge constructs.

Surgical Approaches

In most cases, a medial parapatellar approach can be used. Occasionally, an extensile exposure such as a quadriceps snip may be required (Figure 57.10).

Preoperative Planning

In patients with extra-articular deformities, a detailed preoperative planning is imperative for 3 reasons:

Previous skin incisions and compromised soft-tissue flaps will need to be addressed in many cases.
Previous hardware and/or instruments may need to be removed.

The extra-articular deformity will have to be addressed to optimize component positioning in all planes while having a joint line perpendicular to the mechanical axis.

Figure 57.7 ▪ Intraoperative picture of the patient from Figures 57.3 and 57.6 depicting the use of extramedullary alignment to obtain a neutral mechanical axis irrespective of the tibial deformity.

Figure 57.8 ▪ This intraoperative picture depicts the use of handheld navigation on the femur for a patient with an extra-articular distal femoral deformity with in situ femoral hardware.

Figure 57.9 ▪ The patient from Figure 57.2B with spondyepiphyseal dysplasia and 2 extra-articular femoral deformities underwent an uncomplicated right primary TKA utilizing robotically assisted surgery.

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