Supramalleolar Osteotomy with Internal Fixation Perspective 1

Ankle arthritis is characterized by loss of joint cartilage and joint narrowing.

Primary ankle arthritis is relatively rare; most commonly, ankle arthritis is posttraumatic in origin. Inflammatory arthritides may also involve the ankle. Although ankle arthrodesis and total ankle arthroplasty are accepted surgical treatments for advanced ankle arthritis, joint-preserving supramalleolar osteotomy is an attractive alternative in select patients with advanced ankle arthritis, particularly in ankle arthritis associated with malalignment.^{5,17,25,27,31,37}

Supramalleolar osteotomy, whether opening or closing wedge, redistributes stresses on the ankle, transferring weight from an overloaded arthritic portion of the joint to a healthier aspect of the joint.^6,29,32,34 In theory, realignment also improves the biomechanics of the lower extremity³³ and may improve function and delay the progression of the degenerative process. Despite the fact that the later theoretical hypothesis sounds reasonable, Knupp et al¹¹ demonstrated, using an experimental cadaveric model, that the isolated supramalleolar varus or valgus deformities did not inevitably lead to a medial or lateral overload, respectively. They concluded that the alterations of force transmission and intra-articular pressure in the ankle joint occur with the combined alteration in both the bony alignment and the congruency of the ankle joint.¹¹

ANATOMY

The ankle joint is the articulation formed by the mortise (tibial plafond–medial malleolus and the distal part of the fibula) and the talus.

The ankle is a modified hinge joint with a slight oblique orientation in two planes: (1) posterior and lateral in the transverse plane and (2) lateral and downward in the coronal plane.

This sagittal plane orientation affords about 6 degrees of rotation and 45 to 70 degrees in the flexion–extension motion arc.

The tibiotalar joint functions as part of the ankle–subtalar joint complex during gait; portions of the medial and lateral collateral ligaments cross both the ankle and subtalar joints. The blood supply is provided by the anterior and posterior tibial arteries and the peroneal artery as well as their branches and anastomoses, forming a rich vascular ring.

The distal tibial plafond is slightly valgus oriented, in the coronal plane, with respect to the tibial diaphysis, forming an angle called the tibial ankle surface (TAS) with a value of 93 degrees.¹⁶

The same angle in the sagittal plane, with its apex posteriorly, is called the tibial lateral surface (TLS), with a value of 80 degrees.¹⁶

PATHOGENESIS

Idiopathic (primary) arthritis, or osteoarthrosis, is relatively rare in the ankle. The exact mechanism of cartilage degeneration and loss has not been clearly defined, although several theories have been proposed.

Secondary arthritic involvement is mainly posttraumatic, occurring after intra-articular fractures, chondral or osteochondral injuries, and chronic instability.

Other causes of ankle arthritis include peripheral neuropathy (neuroarthropathy) and various inflammatory disorders (such as rheumatoid arthritis, mixed connective tissue disorders, gout, and pseudogout), primary synovial disorders (pigmented villonodular synovitis), and septic arthritis as well as seronegative arthritides associated with psoriasis, Reiter syndrome, and spondyloarthropathy.

Distal tibial deformity may be a result of malunion of a distal tibial or pilon fracture, physeal disturbance from adjacent osteochondromata, physeal dysplasia, and so forth.

NATURAL HISTORY

Untreated ankle arthritis typically progresses, with worsening pain that eventually interferes with daily activities. Gradually, ankle stiffness in addition to pain leads to a disturbance of physiologic heel-to-toe gait.

Low-demand patients with isolated ankle arthritis may function surprisingly well because of the adaptive effect of the healthy subtalar and transverse talar joints. However, obesity, high-demand activity levels, and concomitant subtalar or transverse tarsal joint pathology typically contribute to the morbidity of ankle arthritis.

To our knowledge, there are no absolute numbers for tibiotalar angular alignment that predispose an ankle to the development of arthritis. Several authors have reported that angulation exceeding 10 degrees was compatible with long-term normal function and absence of pain in the ankle joint,^12,18 whereas biomechanical studies on cadavers have shown that there is a decrease of the contact surface area in the ankle joint of up to 40% in the presence of malalignment,^35,36 with the distal tibial deformities significantly altering total tibiotalar contact area, contact shape, and contact location.³⁵

PATIENT HISTORY AND PHYSICAL FINDINGS

A complete examination of the ankle and hindfoot joints should include the following:

Soft tissue condition: previous scars, callosities, ulcers, fistulas, and so forth

Vascular status: peripheral pulses, microcirculation (capillary refill), ankle–brachial index

Sensation: light touch and, if indicated, Semmes-Weinstein monofilament testing to rule out a peripheral neuropathy. A joint-preserving realignment supramalleolar osteotomy is feasible in select patients with peripheral neuropathy, but the potential for Charcot neuroarthropathy and failure of the procedure must be considered.

Stability: Anterior drawer test and inversion and eversion stress evaluations are performed to evaluate the integrity of the ankle and hindfoot ligaments. Realignment osteotomy with unstable or incompetent ankle or hindfoot ligaments may fail to improve function.

Motor strength: Manual motor testing of the major muscle groups is performed. Realignment in patients lacking essential motor function at the ankle will improve function in stance phase but will typically necessitate bracing for effective gait.

Alignment: The angle made by the Achilles and the vertical axis of the calcaneus is normally 5 to 7 degrees of valgus. Altered alignment to varus or increased valgus position indicates either abnormal tilt of the talus within the ankle mortise (eg, unicompartmental cartilage wear) or abnormality of the subtalar joint.

Effusion testing: Elimination or fullness of the gutters indicates intra-articular fluid accumulation or hypertrophied capsular tissue.

Normal ankle and hindfoot range of motion (ROM) in the sagittal plane is 20 degrees of dorsiflexion to 50 degrees of plantarflexion. Normal values of hindfoot motion are difficult to measure because the motion is triplanar. A reasonable reference is 5 degrees of eversion and 20 degrees of inversion.

• Isolated supramalleolar osteotomy for a stiff ankle rarely improves ROM; a stiff, diffusely arthritic and malaligned ankle may be best treated with realignment.

Hindfoot stiffness must also be documented. In patients with malaligned ankles, the hindfoot compensates. For example, a varus ankle will generally be associated with a compensating hindfoot in excessive valgus. If the hindfoot has lost its flexibility due to long-standing compensation for ankle malalignment, then supramalleolar osteotomy may realign the tibiotalar joint but create hindfoot malalignment. With a flexible hindfoot, this is generally not a problem.

IMAGING AND OTHER DIAGNOSTIC STUDIES

Weight-bearing anteroposterior (AP), lateral, and mortise ankle and foot radiographs determine the extent of arthritic involvement, deformity, bone defects in the distal tibial plafond or talus, and the presence of arthritis in the adjacent hindfoot articulations. Radiographs may also suggest avascular necrosis (AVN) of the talus or distal tibia.

With deformity, a minimum of full-length, weight-bearing AP and lateral tibial radiographs must be obtained. If more proximal deformity is suspected, then mechanical axis, full-length hip-to-ankle radiographs should be considered to accurately plan realignment. More comprehensive full-length, weight-bearing radiographs are required to measure the TAS and TLS angles, the level of center of rotation of angulation (CORA) in case of existing deformity, and the preoperative leg length discrepancy because any substantial discrepancy may have an impact to the choice of osteotomy.

Diagnostic injection. If there is uncertainty over whether the pain is originating from the ankle or hindfoot, selective injections may be of use in distinguishing the source of pain.

DIFFERENTIAL DIAGNOSIS

Bone marrow edema

Soft tissue pathology

Distal tibial plafond or talar AVN

Osteochondritis

NONOPERATIVE MANAGEMENT

Nonoperative treatment of ankle arthritis includes pharmacologic agents, intra-articular corticosteroid injections, shoe wear modifications, and orthoses.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used and have proven efficacy in the management of arthritis, including ankle arthritis. In select patients with gastrointestinal irrigation, COX-2 inhibitors may offer a reasonable alternative to NSAIDs. Inflammatory arthritides are managed with immunosuppressive agents.

Judicious use of intra-articular corticosteroid injections may temporize inflammation associated with intra-articular ankle pathology. Moreover, initial injections of the ankle or hindfoot may serve a diagnostic purpose to distinguish ankle from hindfoot pain. Indiscreet use of corticosteroid injections may have a deleterious effect on the residual joint cartilage as a result of the steroid, the anesthetic, or perhaps the accompanying preservative.

Bracing to immobilize and support the arthritic ankle may provide some pain relief with weight bearing and ambulation. Specifically, polypropylene ankle–foot orthoses (AFOs), double metal upright braces, and lace-up braces, combined with the use of a stiff-soled rocker bottom shoe, may be of benefit. Bracing tibial and tibiotalar malalignment is challenging. With a flexible hindfoot, some axial realignment may be feasible, but correction is generally not possible at the focus of deformity.

SURGICAL MANAGEMENT

We use the supramalleolar osteotomy for the following indications^2,3,30:

Realignment of distal tibia fracture malunion without or with mild osteoarthritic changes of the ankle joint

Realignment of distal tibia malunion with mild to moderate osteoarthritic changes of the ankle joint

Ankle fusion malunion

Ankle arthritis with deformity secondary to intra-articular trauma or AVN of the distal tibia

Correction of valgus deformity associated with a ball-and-socket ankle joint configuration secondary to tarsal coalition

Tibiotalar osteoarthritis resulting from chronic lateral ankle instability or a cavovarus foot deformity

Restoration of a plantigrade foot position in ankle deformity resulting from Charcot neuroarthropathy to create ankle and hindfoot alignment that may be safely braced

Correction of limb alignment in adolescents and young adults due to growth plate injury

Correction of lower limb alignment as staged planning for a total ankle replacement

As a rule, we reserve supramalleolar osteotomy using internal fixation for mild to moderate angular deformities in the coronal or the sagittal plane. Severe angular deformities with concomitant translation of the distal segment or shortening are, in our opinion, better managed using external fixation and the principles of Ilizarov.^8,26

Moreover, gradual correction of severe deformity with formation of a regenerate avoids large plates under a wound and typically thin soft tissues that would be under tension with acute correction using internal fixation.

Lee et al¹⁵ warned out that a supramalleolar osteotomy is indicated for the treatment of ankle osteoarthritis in patients with minimal talar tilt and neutral or varus heel alignment.

Comparing closing and opening wedge supramalleolar osteotomies: A closing wedge osteotomy may result in limb shortening when compared to opening wedge osteotomies. Conflicting reports exist regarding healing rates between the two methods. Studies suggest that closing wedge osteotomies exhibit delayed healing when compared to opening wedge osteotomies,³³ but other reports demonstrate more rapid healing using a closing wedge osteotomy.^28–30 One advantage of a closing wedge osteotomy is that it does not necessitate incorporation of cancellous or structural interpositional graft. Although an opening wedge osteotomy may preserve limb length, resultant skin tension from acute correction may create problems with wound healing and potential vascular compromise if the vessels are put on sudden stretch. Gradual correction with external fixation may be a safer option in cases with severe deformity.

In the absence of appreciable preoperative leg length discrepancy, we recommend correcting distal tibial varus deformities with a medial opening wedge osteotomy and valgus deformities with a medial closing wedge osteotomy.

Knupp et al¹⁰ reported that the decision for the type of osteotomy was based on the amount of correction needed. Thus, in the presence of severe varus deformities, the authors preferred a lateral closing osteotomy instead of a medial opening wedge because the fibula, in the late scenario, would restrict the potential for adequate correction.¹⁰

Preoperative Planning

We routinely obtain bilateral, full-length, weight-bearing radiographs of the tibia including the knee and ankle joints.

We draw two lines on the preoperative radiographs: (1) the tibial mechanical axis (which for the tibia coincides with the anatomic axis) and (2) the distal tibial articular surface. On the AP view, the angle formed by these lines is the TAS angle (FIG 1). On the lateral view, these lines form the TLS angle.