Issue: June 2006

ByRodney K. Alan, MD

ByAlfred J. Tria Jr, MD

June 01, 2006

6 min read

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Technique tailored for quadriceps-sparing TKA

Although implants that substitute or retain the cruciate are amenable to this approach, the authors prefer posterior cruciate-substituting designs.

Issue: June 2006

ByRodney K. Alan, MD

ByAlfred J. Tria Jr, MD

Quadriceps-sparing total knee arthroplasty is one of several techniques orthopedic surgeons use for minimally invasive knee replacement. It is the least invasive approach but perhaps the most difficult one as well, and is not meant for all patients or all surgeons.

However, in the right setting, quadriceps-sparing TKA can lead to less pain, quicker recovery, greater motion and similar clinical results to those of standard TKA at two years’ follow-up.

Patients who are best suited for the quadriceps-sparing TKA include those who weigh less than 225 pounds, have a knee range of motion of at least 105°, had no previous osteotomy or reconstructive arthrotomy, demonstrate a deformity of less than 15° in all planes, are younger than 80 years old and have minimal osteoporosis. Patella baja and a low insertion of the vastus medialis make the procedure more difficult.

Figure 1: The leg holder (Innovative Medical Products) enables the surgeon to position the knee in any degree of flexion and holds the position.

Figure 2: The MIS incision extends from the top of the patella to 2 cm below the tibial joint line.

Figure 3: The patellar resector fits around the patella and indicates the amount of resected bone and the amount of bone remaining.

Figure 4: The metal patellar protector prevents injury to the cut surface throughout the remainder of the operation.

Figure 5: The anteroposterior axis of the femur (Whiteside’s line).

Figure 6: The intramedullary femoral guide has an arm that rests on the medial femoral condyle.

Figure 7: The extramedullary tibial cutting guide.

Figure 8: The proximal tibia can be cut in two or more pieces to facilitate removal of the fragment. Here, the medial one-half of the tibia has been removed and the saw blade is set into the remaining slot beneath the lateral section.

Images: Alan RK, Tria AJ

Patient preparation

For the surgery, the patient is placed supine with an arterial tourniquet applied to the thigh. A leg holder is now routinely used to assist with positioning the limb throughout the procedure (Figure 1). The medial skin incision is then made from the superior pole of the patella to 2 cm below the tibial joint line (Figure 2). The arthrotomy is made in line with the skin incision and is not extended into the quadriceps tendon, the vastus medialis or the subvastus interval.

The extremity is next brought into full extension, the patellar fat pad is excised and the patellar thickness is recorded. Then the MIS patellar guide is used to remove a measured amount of bone (Figure 3). A metal protector is placed over the patellar surface for the remainder of the procedure (Figure 4). Patellar resection is not mandatory but it does facilitate subsequent retractor positioning for knee exposure.

The anterior cortical surface above the sulcus of the femur is cleared for sizing and component placement. The knee is flexed to 45° and both the anterior and posterior cruciate ligaments are resected from the intercondylar notch. Cruciate-substituting and cruciate-retaining knee replacements are amenable to the quadriceps-sparing approach, but we prefer the posterior cruciate-substituting design.

Figure 9: The femoral tower has foot pads that sit beneath the posterior condyles and should be parallel to Whiteside’s line.

Figure 10: The sliding stylus references the anterior surface of the femur.

Figure 11: The preliminary (or “external rotation”) cut is made with a slotted cutting block that is attached to the femoral tower.

Figure 12: The femoral finishing block is lowered into the knee in full extension and the attached plate rests on the external rotation cut surface.

Images: Alan RK, Tria AJ

The anteroposterior axis (Whiteside’s line) is drawn (Figure 5) and an intramedullary rod is introduced into the femur through a hole just above the notch (Figure 6). A side-cutting guide is attached to the intramedullary reference and a distal cut is made across both femoral condyles. The saw blade should be left captured as long as possible when cutting the lateral condyle to assure accuracy of the resection.

The tibial surface is cut using an extramedullary alignment guide, with the proximal portion of the guide positioned over the tibial tubercle in the pretibial space beneath the skin. The cutting guide attachment projects medially so that the final cut is made in a medial-to-lateral direction (Figure 7). Varus/valgus alignment, posterior slope and depth are measured and adjusted in a manner similar to that of standard TKA.

Tibial surface removed

Figure 13: The knee is flexed to 70° and the finishing cuts are completed on the femur.

Figure 14: The box cut for the posterior stabilized knee.

Images: Alan RK, Tria AJ

After setting and securing the extramedullary alignment guide on the tibia, the cut on the proximal tibia is started with the knee in 70° of flexion. It is not possible to flex the knee to 90° and subluxate the tibia in front of the femur with the quadriceps-sparing approach. The tibial surface is removed as a single piece, although in the tight knee the tibial surface can be cut into one or two pieces to facilitate removal (Figure 8).

The extension space can now be checked with a spacer block and an extramedullary rod. The alignment and balance in extension is confirmed, and if any releases are required, they can be carried out at this time.

The femoral tower references the posterior condyles of the femur and Whiteside’s line (Figure 9). It is pinned onto the previously cut femoral surface with the knee in 90° of flexion. If there is a posterior deficiency of the medial or lateral condyle, the tower is rotated to realign it parallel to the AP axis. The level of the anterior femoral resection and the size of the femoral component are determined by flexing the knee 15° and attaching the sliding stylus to the tower (Figure 10).

A preliminary cutting block is attached to the tower and the anterior cortical resection is completed (Figure 11). This cut sets the external femoral rotation and the position of the femoral component versus the anterior cortex. The femoral finishing block is placed into the extension gap and centered medial to lateral on the distal femur with the attached plate flat against the anterior surface cut (Figure 12). We flex the knee to 70° and complete the femoral finishing cuts and peg holes (Figure 13). If a posterior cruciate-substituting implant is chosen, we finish the box cut for the femoral component (Figure 14).

The flexion and extension gaps can now be compared with spacer blocks and appropriate adjustments can be made without difficulty because 10 mm of bone has been resected from the distal femur and the proximal tibia, providing additional space for the instruments.

The tibial finishing guide has two deployable pins that reference the posterior cortex (Figure 15). The instrument is centered medial to lateral and externally rotated, referencing the tibial tubercle, the femoral box cut and the malleoli of the ankle.

Tibial broaching is completed for a two-piece MIS tibia (Figures 16A-16B). We then remove the patellar protector and complete the peg holes.

All of the components are inserted using Palacos cement because of its prolonged doughy stage, which provides more time for placement and allows easier removal of excess cement.

The tibial component is inserted in full extension and the knee is flexed to 70° to introduce the stem (Figure 17). The femur is inserted with a holder designed for the limited incision (Figure 18). The polyethylene surface is locked into the tibial tray and the patellar component is inserted into the prepared bed. The knee is held in extension and the tourniquet is released.

We now implant the knees with electromagnetic navigation, which decreases X-ray outliers. We attach dynamic reference frames directly to the femoral and tibial surfaces (Figure 19), and the emitter is kept in the field for computer visualization (Figure 20).

Figure 15: The tibial finishing guide has two deployable pins that can reference the posterior cortex of the tibia.

Figure 16A: The MIS tibial broach.

Figure 16B: The two-piece MIS tibial component (Zimmer).

Images: Alan RK, Tria AJ

Full weight-bearing ambulation and range of motion exercises are instituted on the same afternoon as surgery. Low-molecular-weight heparin is used for deep vein thrombosis prophylaxis, but we are considering a transition to a new oral factor Xa inhibitor.

Patients are discharged on the second day postop, and we perform a Doppler ultrasound on day 10. If the Doppler study is negative above the popliteal space, anticoagulation is discontinued.

Alan has received nothing of value for this. Tria is a consulting surgeon for Zimmer and IMP.

Rodney K. Alan, MD, is an orthopedic fellow at Robert Wood Johnson Medical School in New Brunswick, N.J. Alfred J. Tria Jr., MD, is chief of orthopedics and director of orthopedic fellowship training at Robert Wood Johnson Medical School.

Figure 17: The tibial stem is screwed into the component from above.

Figure 18: The femoral holder is steadied for insertion of the component.

Figure 19: The dynamic reference frames are attached with small screws to the medial side of the femur and the tibia.

Figure 20: The emitter must be covered with a sterile bag.

Images: Alan RK, Tria AJ

For more information:
Boerger TO, Aglietti P, Mondanelli N, Sensi L. Mini-subvastus versus medial parapatellar approach in total knee arthroplasty. Clin Orthop. 2005;440:82-87.
Laskin RS, Beksac B, Phongkukakorn A, et al: Minimally invasive total knee replacement through a mini-midvastus incision: An outcome study. Clin Orthop. 2004;428:774-781.
Sporer SM. The minimally invasive subvastus approach for primary total knee arthroplasty. J Knee Surg. 2006;19(1):58-62.
Tenholder M, Clarke HD, Scuderi GR. Minimal-incision total knee arthroplasty: The early clinical experience. Clin Orthop. 2005;440:67-76.
Tria AJ, Coon TM. Minimal incision TKA: Early experience. Clin Orthop. 2003;416:185-190.
Tria AJ. Advancements in minimal invasive total knee arthroplasty. Orthopedics. 2003;26(8)(supplement):s859-s863.

Tria AJ. MIS TKA — The importance of instrumentation. Orthop Clin North Am. 2004;35:227-234.