Patellar Tendon

FIGURE 1: Patellar tendon graft. Tendonis portion in middle with bone plugs (the red areas) at either end.

The majority of the ACL reconstruction technique is the same regardless of the tissue used (patellar tendon, hamstring, or Achilles). We will describe the surgical technique associated with a patellar tendon graft (Fig 1) in this section. The patellar tendon attaches your kneecap (patella) to your upper shin (tibia). It transmits forces from the quadriceps muscles to the shin which allows you to extend (straighten) your leg. To replace the torn ACL the middle 1/3 of the patellar tendon is used.

FIGURE 2: The two incisions that are used to harvest the middle 1/3 of the patellar tendon.

If an allograft (from a donor) patellar tendon is used, the graft harvest steps are skipped. However, if an autograft (from you) patellar graft is used it is harvested from the front of your knee through two 1″ incisions. A vertical incision is made just to the side of the tibial tubercle and 1″ below the jointline (Fig 2). Likewise a patellar incision is made beginning at bottom of the patella and extending to the the midline. The two small incisions are more cosmetic and produce less pain than one large one.

FIGURE 3: An oscillating surgical saw is used to harvest the bone plugs.

As mentioned before the patellar tendon is attached to the patella and runs down and attaches to your tibia. Small plugs of bone where the tendon attaches to the patella and tibia are harvested along with the tendon itself. The bone plugs are removed with the aide of a surgical saw (Fig 3). The bone plug from the tibial is typically 10mm in width and the plug from the patella is 11mm. Both plugs are about 25mm (1″) long.

FIGURE 4: The specially designed two bladed harvester is used to accurately remove the middle 1/3 of the patellar tendon.

After creating the bone plugs, the middle third of the patella tendon is harvested using a Parasmillie tendon harvester. This special double bladed knife cuts exactly 1/3 of the patellar tendon with one pass (Fig 4). The medial and lateral thirds of the patellar tendon are left intact. The sharp corners of the defect where the bone plugs were harvested are rounded with a high speed burr and the patellar defect is filled with bone chips.

The rest of the technique is the same for both the allograft and autograft patellar tendons. At a side table the tendon with the attached bone plugs is shaped appropriately to replace the torn ACL.

FIGURE 5: Bone is removed from the femoral notch during the notch / roofplasty.

At this point the reconstruction moves to the inside of the knee and the arthroscope is used. Using the scope a thorough examination of the knee is performed. Meniscal tears or other intra- articular injuries are addressed. The Anterior Cruciate Ligament is confirmed to be torn and the knee unstable . Once the ACL is confirmed to be insufficient, the reconstruction is undertaken.First, a notch/ roofplasty is performed . The anterior cruciate ligament attaches to the femur within the intercondylar notch . During the notch and roofplasty s small amount of bone is removed from the notch so that no portion of the graft rubs against the femur during flexion or extension (Fig 5). Additionally the notch / roofplasty allows accurate visualization of the site where the graft will be placed .

FIGURE 6: The tibial tunnel is placed with aid of a specially designed drill guide.

Tunnels are drilled into both the femur and tibia during the reconstruction. The placement of these tunnels is critical. The tibial tunnel is positioned with the aid of an arthroscopic drill guide that we developed. The guide (Fig 6) positions the tunnel at the anatomic center of the native ACL. Inaccurate placement of the graft will result in failure due to either excess graft looseness or graft stretching. To drill the tunnel an incision is made just to the side of the tibial tubercle.

FIGURE 7a: T The location femoral tunnel is determined with the aid of an endoscopic drill guide.

Another specially designed guide is used to place the femoral tunnel, this guide is called an endoscopic femoral aimer (EFA). The femoral tunnel is drilled within the femoral notch through the tibial tunnel (Fig 7a and b). Therefore no separate incision is needed to make the femoral tunnel. Using the EFA a guide wire is drilled into the femur. The guide wire allows us to check for proper tunnel placement before the final tunnel is drill. If the placement is correct an appropriately sized reamer (typically 11mm) is drilled over the guide wire to create the final tunnel.

FIGURE 8: The graft is pulled into place. One bone plug is positioned within the femoral tunnel and the other within the tibial tunnel. The tendonis portion spans the gap.

Using a long needle the graft with the attached bone plugs is pulled into place. One of the bone plugs is pulled into the femoral tunnel and the other fits into the tibial tunnel (Fig 8). The tendonis portion runing between the two bone plugs is now located where the torn ACL once was. The bone plugs are secured within the tunnels with an interference screw (Fig 9). The screws can be made of either metal or a bioabsorbable material. Since 1992 we have used the bioabsorbable screws exclusively.

FIGURE 9: The bone plugs are secured within the tunnels with interference screws.

The femoral bone plug is secured first. With the femoral side secured the knee is flexed and extended. There should be no streching or loosening of the graft as the knee is flexed an extended. If there is this motion is usually caused by inappropriate tunnel placement and must be corrected. If everything looks correct the tibial bone plug is secured with an interference screw thereby completing the reconstruction.

At this point the knee is flushed with saline to remove any loose bits of bone or tissue and the incisions are closed with sutures and steri strips. The incisions are covered with a sterile dressing and an ace type wrap. A cold cuff and brace are placed on the knee. The patient is then moved to the recovery room.