Revision knee replacement is a challenging operation that sometimes requires special attention to old surgical scar formation and fibrous adhesions. Complications such as avulsion of the patellar tendon off of its tibial tubercle insertion may occur as the result of a vigorous effort to retract the patella laterally in order to gain more exposure. This complication leads to a devastating clinical outcome that is difficult to manage. With this in mind, a key step to achieve success in revision total knee arthroplasty (TKA) is adequate and safe surgical exposure.
Exposure is one of the most important requirements in accomplishing a successful revision surgery. It should provide enough surgical visualization to carefully and safely remove the components from bone and accurately assess collateral ligament health. In most revision surgeries, exposure can be obtained by careful and patient dissection in a manner similar to that used in primary TKA. Whenever possible, the previous skin incision should be used. In the standard approach, the medial parapatellar arthrotomy is extended down to an area 1 cm medial to the tibial tubercle. The tissue lateral to this incision is undermined periosteally, which preserves some of the soft tissue sleeve medial to the patellar tendon. This maneuver permits retention of extra tissue to protect the patellar tendon during attempted eversion of the patella. It is important to create the dissection plane between the anterior flare of the proximal tibia and the posterior aspect of the patellar tendon in order to remove any tethering effect of scar tissue that has developed there. A subperiosteal medial dissection should be performed around the medial flare of the tibia, extending to the posterior aspect where the semimembranosus insertion may be released. Release of the semimembranosus tendon facilitates exposure of the proximal tibia for tibial component removal by permitting the medial portion of the tibia to come farther anteriorly from underneath the femoral component. If the tibial component is modular, the polyethylene insert should be removed. At this time, the surgeon should be able to more easily see the proximal portion of the tibial plate and can proceed with further dissection and soft tissue release from the posterior aspect of the tibia. If the exposure still appears inadequate, it is necessary to change to another, more extensile surgical method of exposure.
There are many options available to provide an extensile exposure in revision TKA. The quadriceps snip is one of the most popular and simple approaches to gain an adequate anatomic view of the knee joint. However, for patients with a severely stiff knee that has fulminant scar and a contracted quadriceps muscle, the quadriceps snip technique might not provide adequate exposure. Another approach is the tibial tubercle osteotomy (TTO), which can also provide excellent exposure but is more technically difficult to perform. It requires extra hardware, usually wires to secure the osteotomy site. Some incidences of tubercle fixation failure and fracture of the tibia have been reported with this technique.
There are rare occasions when scarring is extensive and TTO may not be the proper choice of exposure. In these cases, the V-Y quadriceps turndown technique may be used. This technique was initially developed in 1943 by Coonse and Adams. They originally described two incisions—one made from a center point in the quadriceps tendon across the lateral retinaculum and joint capsule distally and the other beginning at the starting point in the quadriceps tendon and extending distally through the quadriceps muscle—resulting in an inverted “V” shape with symmetric distal medial and lateral limbs ( Fig. 8.1 ). However, this concept could not be applied with the standard medial parapatellar incision that was commonly used for knee replacement.
In 1983, John Insall modified the incision to preserve the patellar blood supply from the inferior lateral genicular artery and to avoid violation of the vastus medialis ( Fig. 8.2 ). The modified V-Y quadriceps turndown enables extension of the proximal portion of the standard medial parapatellar approach in cases in which more exposure is required. This is done by making another incision directed distally and laterally away from the proximal end of the medial parapatellar arthrotomy incision, across the quadriceps tendon and vastus lateralis into the lateral retinaculum approximately 2 to 4 cm lateral to the superior pole of the patella ( Fig. 8.3 ).
A benefit of the V-Y quadriceps turndown over other approaches is that it allows the surgeon to lengthen the quadriceps tendon during repair, permitting additional flexion. However, this may alter the resting length of the muscle–tendon unit and weaken effective muscle contraction and strength despite the improved motion.
Whenever possible, the original midline skin incision should be used. If there are multiple prior incisions, the most lateral incision should be used to avoid risk of skin necrosis. However, use of an old skin incision scar that is located too far laterally could limit exposure, and a new incision may be required. The skin should be undermined medially and laterally just above the quadriceps extensor mechanism under the skin to avoid risk of vascular interruption of the skin circulation. It is important to obtain adequate medial and lateral exposure to permit creation of the quadricepsplasty incisions ( Fig. 8.4 ). The quadriceps tendon origin must be clearly visualized. Frequently in revision cases, it is easier to start undermining the skin in the normal, unscarred tissue deep to the proximal limb of an old surgical scar, where the dissection plane is more easily defined. A medial parapatellar capsular incision is made, beginning at the proximal portion of the quadriceps tendon and continuing distally to the medial border of the tibial tubercle. Ideally, this distal incision should lie 1 cm medial to the edge of the tibial tubercle. Any thick, fibrous adhesions between the quadriceps muscle and the femur should be excised or released. A dissection plane should be created along the medial and lateral anatomic gutters adjacent to the femur. A wide osteotome can be used during this exposure to re-create these gutters and define a proper dissection plane to free up the quadriceps muscle that is scarred to the medial and lateral aspects of the femur. Scar located between the posterior aspect of the patellar tendon and the anterior aspect of the tibia should be excised.