Allograft Resurfacing of the Tibiotalar Joint

CHAPTER PREVIEW

CHAPTER SYNOPSIS:

Biological alternatives to inorganic implant arthroplasty exist in the form of allograft implants to resurface the ankle. The talar and tibial bone–cartilage grafts are freshly harvested from cadaveric patients, and the technique described models the Agility implant. This may be particularly helpful in young patients with posttraumatic degenerative arthritis.

IMPORTANT POINTS:

1

Alignment issues must be corrected before allograft resurfacing.
2

Allografts are size-matched based on radiographs.
3

Tissue typing and immunosuppressive therapy are not needed.

CLINICAL PEARLS

1

An external fixator for intraoperative distraction is needed (to be removed at the end of the procedure).
2

Symmetric space is required with distraction.
3

Lavage the specimens before implantation to help remove remnants of blood or tissue.
4

Immobilize postoperatively until sutures are out and the wound is well healed, then early range of motion. Patient must be non–weight-bearing for 3 months.

CLINICAL/SURGICAL PITFALLS:

1

Most early failures are technical errors—poor bone cuts and fixation.
2

Special care given to the bone cuts in the patient to avoid malleolar fracture.

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HISTORY/INTRODUCTION/SCOPE OF THE PROBLEM

Tibiotalar arthritis in young active patients is a challenging problem for both patients and orthopedic surgeons. Although primary ankle arthritis is rare, it can be debilitating for patients. Inflammation, synovitis, and other pathologic conditions, such as rheumatoid arthritis, can lead to destruction of the ankle joint. However, the most common causes of degenerative changes in the ankle are trauma and abnormal ankle mechanics. Posttraumatic arthritis is correlated to the severity of the ankle fracture pattern and congruity of the articular surfaces. These disease processes can lead to loss of joint space, subchondral cysts, osteophyte formation, loss of motion, pain, and disability.

Ankle arthritis can be treated by nonsurgical management with the use of anti-inflammatory medicine, orthoses, and intra-articular steroid injections. However, ankle arthritis can be difficult to treat with nonoperative management. Surgical options to treat ankle arthritis encompass a wide variety of procedures. Arthroscopic debridement of loose bodies or impinging osteophytes may relieve pain temporarily, as well as provide a diagnostic evaluation of the articular surfaces. Ankle arthrodeses and ankle arthroplasty were the traditional surgical options for advanced tibiotalar arthritis. Ankle arthrodesis has been shown to be very successful at alleviating pain; however, the patient may continue to have loss of range of motion, functional limitations, possible limp, and pseudoarthrosis. There is also the risk of secondary progressive arthritis in the midfoot and hindfoot. Advancements in surgical technique and design implant have made total ankle arthroplasty an encouraging alternative to arthrodesis. However, studies have reported that younger patients have a higher risk of failure and reoperation rate.

The use of fresh ankle osteochondral allograft transplantation for the treatment of end-stage tibiotalar arthritis is an attractive alternative in young or active patients. This technically demanding procedure replaces damaged articular cartilage and preserves range of motion and ankle function.

Fresh allografts have been used successfully in the knee and have increased their role for select patients with end-stage tibiotalar arthritis. Structural allografting maintains the bone stock of the ankle and provides congruent articular surface. Also, this procedure prevents the secondary degeneration of the surrounding joints that can be seen after an ankle arthrodesis.

The unique characteristics of the osseous and chondral tissue components allow for successful transplantation. Unlike fresh-frozen allografts, fresh allografts contain viable chondrocytes that survive transplantation. Studies have shown that 70% of chondrocytes are still viable at 28 days in storage media. The allograft bone allows for support and fixation of the chondral surfaces. The transplanted subchondral bone is slowly replaced by the host bone by creeping substitution. However, during this time of revascularization, the graft is at risk of collapse.

Size-matched osteochondral allografts are obtained from regional tissue banks using anteroposterior (AP) weight-bearing radiographs of the host and allograft specimen. The measurement of the mediolateral width of the talus, 0.5 cm below the talar dome on the x-ray, is used to size-match the host to the graft. All patients are counseled that the risk of disease transmission is similar to that of homologous blood transfusion. However, there are no reports of transmission of diseases when using ankle allograft replacement. Graft specimens are cultured and tested for bacteria, antibodies to HIV, hepatitis, and syphilis. No tissue or blood type matching is necessary because immunologic response to unmatched allografts has not proved to be of clinical significance.

Fresh allografts are harvested within 24 hours of death and take approximately 21 days to be tested and released. Grafts are placed in sterile bags and immersed in culture medial solution containing 1 g/L cephalothin and 10 mg/L gentamicin. They are stored at 4°C until use. Fresh allografts should be implanted within 28 days of procurement.

INDICATIONS/CONTRAINDICATIONS

Young, active patients with end-stage tibiotalar arthritis are most likely to benefit from the allograft procedure. A thorough orthopedic history and physical examination must be performed and other sources of hindfoot pain must be excluded. Ligamentous instability, malalignment, and other deformities of the foot and ankle must be evaluated clinically and radiographically. Also, if the ankle cannot be brought to at least neutral position during active-assisted dorsiflexion, then Achilles contracture, posterior capsule contracture, or gastrocnemius contracture must be considered. Ankle alignment must be checked for any varus or valgus deformity that may need to be corrected at the time of surgery to prevent unnecessary forces across the graft. Computed tomography and magnetic resonance imaging can be obtained if necessary to assess the bony architecture and/or subchondral cysts of the tibia or talus. Coexisting foot deformities or malalignment must be addressed before ankle allograft replacement and may need corrective osteotomies.

Contraindications for shell allograft ankle reconstruction are an inexperienced surgeon, significant peripheral vascular disease, varus or valgus malalignment of the tibiotalar joint greater than 10 degrees, large cystic lesions, instability of the ankle joint, and obesity.

SURGICAL TECHNIQUE

An external fixator or distraction device is useful during the operation. DePuy Agility (DePuy, Warsaw, IN) ankle arthroplasty jigs are used to increase the precision of the cuts.

Positioning

Patient is supine on a radiolucent operating table and a soft bolster is placed under the ipsilateral hop. A thigh tourniquent is placed and the toes are covered with plastic adhesive or Coban wrap.

Approach/Debridement and Distraction of the Ankle Joint

Prior to inflating the tourniquent, a uniplane, unilateral external fixator is placed on the medial side of the ankle for the purposes of distraction during the surgery. Pins are placed medially into the calcaneal body, the talar neck and (two pins) the tibia ( Fig. 7-1 ). The external fixator position is locked in position and then removed from the pins. The leg is exsanguinated and the tourniquet is inflated to 275 mm Hg. The ankle joint is entered through the standard anterior approach between the tibialis anterior and extensor hallucis longus tendon. The extensor retinaculum is incised directly over the extensor hallucis longus tendon. The neurovascular bundle is revealed with deep dissection and retracted laterally for protection. The tibialis anterior tendon is retracted medially, and the ankle is exposed with subperiosteal dissection. The distal tibia, fibula, and taus are exposed from the medial malleolus to the syndesmosis. Debridement of the joint osteophytes is performed with rongeurs and osteotomes. Next, an external fixator is replaced to distract the joint symmetrically approximately 1 cm. Distraction is checked with an image intensifier to ensure it is symmetric. In the unlikely event that the ankle was distracted asymmetrically (excessive valgus), the external fixator can be adjusted to compensate.