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Consider quadriceps snip or tibial tubercle osteotomy for revision TKA exposure
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In many revision total knee arthroplasty cases, the knee can be exposed through a medial parapatellar approach. However, sometimes lateral patellar retraction during the medial parapatellar approach can put too much tension on the extensor mechanism and, should this happen, there is a risk of avulsion of the tibial tubercle. Therefore, you should consider using one of two extensile exposures in these cases.
In my practice, about one-third of revision total knee arthroplasty (TKA) cases necessitate that I either go proximally and perform an oblique quadriceps tenotomy “quad snip” or that I extend the exposure distally and perform a tibial tubercle osteotomy. Both techniques are reviewed in this article, which is intended to help physicians determine which to use and when.
Parapatellar arthrotomy
After choosing the appropriate skin incision and raising medial and lateral subcutaneous flaps, the first step in the deep exposure is the medial parapatellar arthrotomy.
I have found that you can accomplish a lot when you excise the scar tissue circumferentially around the patella, in the medial and lateral gutters, and in the suprapatellar pouch. Then, you should raise a subperiosteal soft tissue sleeve from the proximal medial tibia and externally rotate the tibia. Next, remove the tibial insert as soon as this can be safely accomplished and complete the synovectomy. If necessary, you can perform a lateral release to get the patella into a lateral position.
The next step is to flex the knee and sublux the patella. However, if the extensor mechanism is contracted or scarred and the patella will not readily sublux, the options are to extend the exposure either distally with a tibial tubercle osteotomy (TTO) or proximally with a rectus snip. Historically, transection of the extensor mechanism proximally with a V-Y quadricepsplasty had been done, but this frequently results in extensor lag. My decision of which technique to use is based mainly on the quality of the patient’s bone. I do not asses the quality of bone quantitatively, but primarily rely on the lateral X-ray view of the proximal tibia to determine the amount of available bone anterior to the tibial component and cement mantle, and relative severity of osteoporosis seen radiographically.
If the proximal tibial bone stock is good and osteotomy will result in a mechanically strong, well-vascularized bone fragment, I prefer the osteotomy because it provides a wider exposure than the rectus snip. However, if the proximal tibial bone is osteoporotic or osteolytic, or full of cement, then osteotomy may result in fracture or poor fixation of the bone fragment. In that situation, I prefer to use a rectus snip to avoid these problems.
TTO technique
The osteotomy is carried out in a medial to lateral direction, which helps maintain continuity of the anterior compartment muscles to the bone fragment. I prefer to use a thin saw blade to minimize bone loss.
Figure 1. The orientation of the planned osteotomy is illustrated in this preoperative lateral knee radiograph.
Images: Ries MD
I recommend planning for a bone fragment that is about 6 cm to 10 cm long and 1.5 cm to 2 cm thick at the level of the tibial tubercle. A chevron shaped osteotomy (Figure 1) that is thickest at the level of the tibial tubercle and tapered proximally and distally provides an interference fit that helps stability and minimizes the risk of a tibia fracture that initiates at the distal osteotomy.
Figure 2. This intraoperative view of a tibial tubercle osteotomy (TTO) shows the attached anterior compartment muscles and the extensor mechanism, which is retracted to expose the knee and proximal tibial intramedullary canal.
To maintain soft tissue attachment to the anterior compartment muscles, the fragment is hinged in a medial to lateral direction and can provide access to the intramedullary canal of the proximal tibia to facilitate removal of stemmed components and cement (Figure 2). Fixation can be achieved with a number of methods, but I prefer a proximal screw that is directed posteromedially around the keel of the tibial component and two distal wires placed through the anterior osteotomy and out the posteromedial tibial cortex (Figure 3).
Figure 3. A postoperative lateral radiograph made after the TTO repair with a proximal screw and two distal medial wires is shown.
Figure 4. An intraoperative view of the medial parapatellar arthrotomy done with a rectus snip (between the two rows of arrows) is the oblique transection of the rectus tendon, which was performed in a distal medial to proximal lateral direction.
Rectus snip indications
If the proximal tibial bone stock is poor and complications of osteotomy fracture or nonunion are a concern, then extension of the exposure proximally with a rectus snip is a safe alternative. The medial parapatellar arthrotomy is made in the usual fashion. The rectus tendon is then tenotomized in a medial to lateral direction. A transverse tenotomy is undesirable since this may put high tension on the tenotomy suture repair or lead to quadriceps rupture.
The proximal portion of the arthrotomy should extend obliquely through the rectus tendon into the vastus lateralis muscle. I illustrate with this article an oblique arthrotomy made in a medial direction through the rectus tendon, which is outlined by arrows. The arthrotomy is repaired in a side-to-side fashion with non-absorbable sutures.
With either TTO or rectus snip, the knee should be flexed after the arthrotomy closure to ensure the integrity of the repair. If there is limited motion or excess tension on the repair, then it may be necessary to restrict motion after surgery.
In general, however, both of these methods will provide reliable fixation, and therefore, restriction in weight-bearing, active or passive knee range of motion is usually not required.
References:
Whiteside LA. Clin Orthop Relat Res. 1995;321:32-35.
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Disclosure: Ries is a consultant to and receives intellectual property (royalties) from Smith & Nephew and Stryker.