Patellar Tendon Allograft Reconstruction

Abstract

Background:

Chronic patellar tendon injuries can cause significant functional deficits due to anterior knee pain, extension weakness, and extensor lag. With chronic injuries, the tissue is inadequate and of poor quality. Chronic injuries require autograft or allograft for augmentation or reconstruction. We present reconstruction of a chronic patellar tendon injury with Achilles tendon allograft.

Indications:

Chronic patellar tendon injuries causing functional deficits, including knee extension weakness, extensor lag, and anterior knee pain.

Technique Description:

A longitudinal incision is made over the patellar tendon, and the patellar tendon is excised. Two guide pins are drilled in a retrograde fashion through the patella and are overdrilled with a reamer. A trough is made at the tibial tubercle using an oscillating saw. The Achilles allograft calcaneal bone block is contoured to the appropriate size, and then press fit into the trough. Two 4.0-mm fully threaded cannulated screws with washers are used to secure the bone block. The fresh frozen Achilles allograft is doubled over, and a double Krackow running locking suture is placed. A V-Y advancement of the quadriceps tendon is performed to ensure adequate advancement of the patella. The limbs of the Krackow suture are pulled through the patella drill holes and tied with knee in full extension.

Results:

At 1 year, patients can expect near full range of motion with minimal extensor lag. Reconstruction results in improved pain and function as compared with preoperatively, as well as return to activities.

Conclusion:

Achilles tendon allograft is a good option for reconstructing chronic patellar tendon injuries. Advantages of the Achilles allograft include the bone-to-bone healing at the tibia, lack of donor site morbidity, and the large amount of tissue available for reconstruction.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

Patellar tendon allograft reconstruction: a surgical technique for management of chronic patellar tendon insufficiency. This video is presented by the listed authors from VCU Sports Medicine and the Virginia Commonwealth University Department of Orthopaedic Surgery in Richmond, Virginia. We have no disclosures.

Chronic patellar tendon insufficiency is a difficult problem due to the functional deficits caused and the challenges with reconstruction. Management can be challenging due to inadequate tissue and poor tissue quality, as well as elongation of the tendon. Treatment requires augmentation or reconstruction using autograft or allograft tissue. We will present a demonstrative case of this difficult problem and discuss our indications, surgical technique for patellar tendon allograft reconstruction, and postoperative rehabilitation.

The patient presented is a 58-year-old man with a complaint of limited right knee extension. He underwent a primary patellar tendon repair 7 years previously after a traumatic injury. He complained of decreased knee range of motion with limited extension, difficulty ambulating, and difficulty climbing and descending stairs.

On examination, he had passive range of motion from 0° to 130°, active range of motion from 20° to 130° with a 20° extensor lag, a stable ligamentous examination, and 4+/5 quadriceps strength. His radiographs showed no significant osteoarthritis, patella alta, and calcifications within remaining patellar tendon. His Insall-Salvati ratio was 2.0.

The surgical indications for patellar tendon reconstruction are chronic patellar tendon injury with functional deficits, full passive range of motion with no flexion contracture, a stable knee, good quadriceps strength, and minimal osteoarthritis. The contraindications to patellar tendon reconstruction are knee flexion contracture and concomitant ligamentous injury.

Key physical examination findings for the purposes of preoperative planning include the evaluation of knee range of motion to ensure there is no significant flexion contracture and a thorough ligamentous examination to rule out concomitant injury. On radiographs, it is critical to evaluate anteroposterior and lateral views of the affected and unaffected knees to compare patellar height.

On the lateral radiographs, we measure and compare Insall-Salvati ratios and the apparent length of the intact patellar tendon. The unaffected knee and patellar tendon are used as a template for reconstruction.

The procedure is performed with the patient in a supine position. A bump is placed under ipsilateral hip so that the knee is not externally rotated. The knee is elevated to facilitate intraoperative fluoroscopy. If a tourniquet is used, it may need to be deflated during the case to allow full excursion of the quadriceps and patella. Key operative supplies and equipment include the fresh frozen Achilles tendon allograft with calcaneal bone block, Kirschner wires, a cannulated 4-mm reamer, an oscillating saw with a blade no more than 10-mm wide, curved 0.5- and 0.25-inch osteotomes, 4.0-mm fully threaded cannulated screws and washers, and specialty sutures. We have used #5 and #2 FiberWire and FiberTape (Arthrex).

The key steps in the procedure are patellar tendon exposure, evaluation, and excision; inferior patellar pole preparation; tibial tubercle preparation; Achilles tendon allograft preparation and tibial fixation; quadriceps tendon V-Y advancement; fixation of the allograft tendon to the inferior pole of the patella; and a layered closure.

A longitudinal incision is made over the patellar tendon. Dissection is carried down to the paratenon, which is incised and flaps are mobilized to facilitate layered closure at the end of the case. The residual patellar tendon is evaluated. In this case, as should be anticipated in chronic patellar tendon injuries, the tendon was found to have significant laxity, mucoid degeneration, and scarring. The tissue was of poor quality and not amenable to direct repair. The patellar tendon is excised in whole. The retropatellar fat pad should be left intact if possible, as this preserves a deep capsular layer between the allograft tendon and the knee joint.

The inferior pole of the patella is debrided of remaining soft tissue using a scalpel and a rongeur. The inferior pole of the patella is decorticated to expose bleeding cancellous bone. This step is critical for maximizing healing at the allograft-bone interface. Note that tibial tubercle preparation, which we will describe in detail momentarily, may be accomplished simultaneously as shown here if a second surgeon or appropriate assistant is available.

Two guide pins are drilled in retrograde fashion through the patella. In the sagittal plane, the guide pins should be placed within the central third of the patella in order to ensure that the articular surface is not violated. In the coronal plane, the guide pins should be placed longitudinally along the medial and lateral edges of the central third of the patella. An Army-Navy retractor used as shown to stabilize the patella and depress the quadriceps tendon can be helpful in identifying the exit point of the guide pins. Short longitudinal incisions are made in the quadriceps tendon in line with its fibers over the guide pin exit points so that they can be clearly visualized. This is critical to ensure that there is no soft tissue bridge beneath the transosseous sutures when they are tied, as this can lead to gapping at the allograft-bone interface after reconstruction. The small incisions in the quadriceps tendon will be repaired later after the transosseous sutures are tied.

The guide pins are overdrilled with a cannulated 4-mm reamer. Passing sutures are placed through the drill tunnels.

The tibial tubercle is sharply exposed using a scalpel for subperiosteal elevation of the overlying soft tissue envelope. Ideally, the full thickness of this tissue is preserved so that it can be closed later on as a deep layer over the tibial allograft fixation.

A trough measuring 15-mm wide, 20-mm long, and 10-mm depth is made at the tibial tubercle. An oscillating saw blade is used to perforate the cortex along the borders of the trough at the appropriate length, width, and depth. A ruler is used to ensure that the cuts have been made to the appropriate depth. Curved 0.25- and 0.5-inch osteotomes are used to carefully remove the corticocancellous fragment.

The calcaneal bone block of the Achilles tendon allograft is cut and contoured to the appropriate size for inlay into the trough.

The allograft bone block is then press fit into the tibial bone trough and seated gently using a bone tamp.

The allograft bone block is fixed in place. Two parallel anterior to posterior Kirschner wires are placed through the bone block into the proximal tibia. Appropriate positioning is confirmed intraoperatively on fluoroscopic imaging, and the depth of the wires is measured. The allograft cortex is predrilled with a cannulated drill for placement of two 4.0-mm fully threaded cannulated screws with washers over the Kirschner wires, fixing the allograft bone block in place in the tibial trough.

Appropriate position of the allograft bone block fixation hardware is confirmed fluoroscopically.

Using preoperative templating, the distance from the distal pole of the patella at its native height to the insertion of the patellar tendon is measured. A V-Y quadriceps advancement may need to be performed at this point to allow for adequate patellar advancement to recreate the native patellar height. A V-shaped incision is made in the quadriceps tendon, and any deep adhesions to the underlying femur are freed. In general, the knee is typically flexed to 60° and the tendon is repaired in its lengthened state in a Y-shaped fashion. In this case, because the patellar tendon has been excised, the patella can be manipulated with a towel clamp or similar instrument to advance it to the appropriate level. It is helpful to wait to repair the quadriceps tendon at the appropriate length once the patellar allograft reconstruction has been secured at the inferior patellar pole.

The fresh frozen Achilles allograft is measured and doubled over at the appropriate length for the reconstructed patellar tendon. Excess allograft tendon may be trimmed with a scalpel or Metzenbaum scissors. A double row of running, locking Krackow sutures are placed into the allograft using #5 FiberWire. This begins at the medial and lateral portions of the allograft tendon with each FiberWire suture, approximately 1 cm from the proximal end of the doubled-over allograft tendon. The suture is introduced from the deep aspect of the allograft to ensure that its determined length is maintained.

The locking Krackow stitches are thrown 5 to 10 mm apart, running distally to a distance of 1 cm from the calcaneal allograft bone block. The sutures are then run back proximally within the medial and lateral central quartiles of the tendon. Typically, the construct will require 5 to 8 throws in each direction. It is important to pull the sutures tight after each throw, ensuring that they are locked without slack between them.

The free limbs of the FiberWire sutures are drawn through the patellar bone tunnels using the previously placed passing sutures. The sutures are tied proximally with the knee held in full extension and appropriate tension to secure the allograft tendon to the inferior patellar pole. Again, it is important to ensure that there is no soft tissue bridge between the proximal pole of the patella and the FiberWire sutures being tied over it. If performed, the quadriceps tendon V-Y advancement is repaired at this point using #2 FiberWire. If a thigh tourniquet is being used, it may need to be let down at this point to allow for full quadriceps excursion to facilitate the repair.

The knee is gently flexed to 90° to ensure a strong reconstruction with no gapping at the allograft-bone interface at the inferior patellar pole. Restoration of appropriate patellar height is confirmed on a lateral view of the knee with intraoperative fluoroscopy.

The allograft tendon can be reinforced centrally with a FiberTape suture, securing the superficial and deep portions of the allograft to one another to strengthen the construct. The ends of the FiberTape suture can be passed through the patellar bone tunnels and tied over the proximal pole for further reinforcement against gapping. Alternatively, interrupted figure-of-eight sutures using #2 FiberWire can be used along the medial and lateral borders of the allograft to secure its superficial and deep portions to one another. These sutures can also be used to secure the allograft tendon to the retinaculum. Once again, the knee is carefully flexed, and the allograft-bone interface is observed closely to ensure no gapping.

The paratenon and periosteal flap preserved during exposure of the tibial tubercle are closed over the reconstructed tendon, followed by a layered closure of the subcutaneous tissues and skin.

The quadriceps tendon V-Y advancement is often a critical step for allowing sufficient patellar excursion to restore the native patellar height and avoid persistent patella alta and maltracking. The V-Y advancement is repaired after securing the allograft to the patella at the appropriate length. Keys for preventing gapping and poor healing at the allograft-bone interface include decorticating the interior patellar pole to optimize healing potential, tying the transosseous sutures with the knee in full extension, and ensuring that no soft tissue bridge is interposed beneath the sutures as they are tied over the proximal pole of the patella.

Our postoperative rehabilitation plan is shown here. The patient is allowed weight bearing as tolerated in a hinged knee brace, kept locked in extension for 6 weeks. After that, a progressive knee range of motion therapy protocol is begun. The patient should be rehabilitated gradually with the target for return to all activities around 9 to 12 months postoperatively.

There have been several methods described in the literature for reconstruction of chronic patellar tendon injuries. Reconstruction with Achilles tendon allograft provides good outcomes with near full extension, minimal extensor lag, and good quadriceps strength. The advantages of the Achilles allograft include the bone-to-bone healing at the tibia, lack of donor site morbidity, and a robust tendon allograft for reconstruction.

Our references are listed. Thank you.