Total Ankle Shell Allograft Reconstruction

Articular defects of the tibiotalar joint, posttraumatic arthritis, and osteoarthritis can limit activity, make walking difficult, and lead to severe pain.

Unlike the knee and hip, primary arthritis rarely affects the ankle. The most common causes of degenerative changes in the ankle are secondary to trauma and abnormal ankle mechanics. Posttraumatic arthritis is correlated to the severity of the fracture pattern and nonanatomic reduction of articular surfaces.¹⁹

Rheumatoid or other inflammatory arthropathies and infection can also cause significant ankle pain, deformities, and arthritis.

Osteoarthritis is described by degradation of the articular cartilage, subchondral sclerosis, and subchondral cyst and osteophyte formation. Changes seen on radiographs include joint space narrowing, osteophytes, and subchondral bone sclerosis.

Treatment options for patients who fail to respond to conservative treatment for ankle arthrosis are tibiotalar arthrodesis, total ankle arthroplasty, and fresh ankle osteochondral shell allografts.^{1,2,9,11,12,16} Tibiotalar osteochondral shell allografts are a reasonable alternative to tibiotalar arthrodesis and total ankle arthroplasty in young patients with posttraumatic ankle arthropathy.^9,12,16

ANATOMY

The ankle joint is complex, but its complexity may be simplified if the ankle is thought of as a single-axis joint in an oblique path from medial to lateral and oriented downward and backward. The main motion is dorsiflexion and plantarflexion, with some inversion and eversion of the tibiotalar joint.³

The bones that make up the ankle joint are the tibia, fibula, and talus. The tibia plafond is concave anteroposteriorly and mediolaterally.

The talus has no muscular or tendinous attachments and 60% of its surface is covered by articular cartilage.

In addition to the bony support of the ankle, the medial and lateral ligamentous complexes provide stability to the ankle and hindfoot.

PATHOGENESIS

The predominant collagen in articular cartilage is type II collagen. Articular cartilage has limited blood supply, cannot proliferate, and has little reparative potential.

Type 1 injury to articular cartilage involves microscopic disruption of chondrocytes and the extracellular matrix, whereas type 2 injuries involve macroscopic damage to the surface. Because the subchondral bone is not involved in these injuries, there is little inflammatory response and therefore poor healing of these injuries. Type 3 injuries involve the subchondral bone as well as the surface and thus heal with a fibrocartilage, consisting mainly of type I collagen.¹⁵

Ankle arthritis may cause loss of motion, pain, deformity, and instability.

NATURAL HISTORY

Tibiotalar arthritis may result from trauma, inflammatory diseases, and osteoarthritis. Posttraumatic arthritis is the most common cause of ankle arthritis despite advances in open reduction and internal fixation of ankle and pilon fractures. Most likely, the tibiotalar chondral surfaces are injured at the time of injury and do not have the capacity to heal.

Posttraumatic tibiotalar arthrosis often fails to respond to nonoperative management, and definitive surgical treatment has been ankle arthrodesis in a majority of patients and total ankle arthroplasty in select patients.^{1,2,5,7,11,16}

Ankle arthrodesis has been shown to alleviate pain in the arthritic ankle. However, loss of range of motion, functional limitation, and secondary progressive arthritis in the hindfoot and midfoot have been found in long-term follow-up studies on patients with isolated ankle arthrodesis.^2,6

Current total ankle prosthetic designs are a promising alternative to arthrodesis, but the patient’s age has an adverse effect on the risk of failure and reoperation rate.^10,16,17

Osteochondral shell allografting, in which the tibial plafond and talar dome are replaced with a donor ankle matched for size affords relief of pain, congruent articular surfaces, maintenance of bone stock, and preservation of surrounding joints. Recent improvements in surgical techniques and experience with allografts have improved short-term outcomes with this technique. Recent studies advocate the use of fresh osteochondral allografting as an alternative treatment for selected individuals with end-stage tibiotalar arthrosis.^9,12,20

PATIENT HISTORY AND PHYSICAL FINDINGS

A thorough history and physical examination of both lower extremities must be performed for any deformities or malalignment to identify multiple joint involvement, symmetric involvement, family history, and a history of trauma. The function and stability of the ligaments and tendons surrounding the ankle should be tested. This includes assessment for an equinus contracture or pes planus or pes cavus deformities. A neurovascular examination must also be performed before surgery.

Physical examination methods include the following¹⁴:

Anterior drawer test to evaluate the anterior talofibular ligament and ankle stability. The surgeon should look for a difference of 3 to 5 mm in the relationship between the lateral talus and the anterior aspect of the fibula.

Inversion stress test to evaluate talar instability (somewhat difficult due to subtalar motion). Compared to the contralateral ankle, a difference of more than 15 degrees is significant.

Equinus contracture assessment. A gastrocnemius recession or Achilles lengthening procedure may be required concomitantly if there is 5 degrees of equinus in the ankle.

Range of motion: Normal total range of motion of the tibiotalar joint is from 20 degrees of dorsiflexion to 50 degrees of plantarflexion. Normal subtalar joint motion is about 20 degrees from maximal inversion to eversion.

Contraindications for shell allograft ankle reconstruction are as follows:

Diminished peripheral pulses

Varus or valgus malalignment of the tibiotalar joint of more than 10 degrees

Instability of the ankle joint

IMAGING AND OTHER DIAGNOSTIC STUDIES

Weight-bearing radiographs of the ankle, including anteroposterior (AP), lateral, and mortise views, are obtained (FIG 1).

When indicated, AP stress radiographs may be obtained to confirm instability. Anterior translation between the talus and tibia of 3 to 5 mm greater than the contralateral ankle indicates instability.³

Talar tilt on stress radiographs with the ankle internally rotated 30 degrees: A difference greater than 15 degrees compared to the contralateral ankle indicates instability.³

DIFFERENTIAL DIAGNOSIS

Ankle instability or deformities

Anterior or posterior impingement syndrome

Osteochondritis dissecans (OCD) lesions of talus or tibia

Subtalar joint osteoarthritis

Sinus tarsi syndrome

NONOPERATIVE MANAGEMENT

Conservative treatment includes mechanical aids (such as ankle–foot orthoses [AFOs] and shoe modifications), anti-inflammatories, and intra-articular steroid injections.

SURGICAL MANAGEMENT

For young healthy individuals who need alleviation of pain and retention of motion and function, osteochondral shell allografts represent an alternative to ankle arthrodesis and total ankle replacement.

Preoperative Planning

Standard radiographs on the ankle are needed for preoperative planning. In our opinion, an external fixator or distraction device is useful during the operation. We routinely use the DePuy Agility (DePuy, Warsaw, IN) ankle arthroplasty cutting block to increase the precision of cuts.

Size-matched osteochondral allografts, based on radiographs, are procured from one of several regional tissue banks.

Positioning

The patient is supine on a radiolucent operating table.

Approach

A standard anterior approach to the ankle is used between the tibialis anterior and extensor hallucis longus tendons while protecting the superficial peroneal nerve. The deep neurovascular bundle (deep peroneal nerve and anterior tibial and dorsalis pedis artery) is retracted laterally and dissection is carried through the joint capsule to expose the ankle.