Markus Knupp and Beat Hintermann
DEFINITION
A supramalleolar osteotomy is an osteotomy at the level of the distal tibia with or without osteotomy of the fibula.
The correction is intended to normalize altered load distribution across the joint and may be indicated in cases of asymmetric osteoarthritis, malunited fractures of the distal tibial, and osteochondral lesions.
ANATOMY
Trauma and neurologic disorders leading to varus and valgus alignment around the ankle joint predispose to asymmetric joint load. This causes cartilage wear, in particular in the presence of associated ligamentous instability and muscular imbalance (FIG 1).
PATHOGENESIS
Various conditions, such as neurologic disorders, congenital and acquired foot deformities, posttraumatic malunions, and instability may be associated with malalignment of the ankle joint complex.
NATURAL HISTORY
Malalignment of the hindfoot may result from bony deformity above or below the level of the ankle joint.
Ligamentous instability or muscular imbalance may be a contributing or even an initiating factor in the natural history of malalignment around the ankle joint.
PATIENT HISTORY AND PHYSICAL FINDINGS
A thorough medical history should be taken.
Systemic diseases, such as diabetes mellitus (Charcot arthropathy), rheumatoid arthritis, and neurovascular disorders need to be assessed carefully.
FIG 1 • Weight-bearing radiograph of a 65-year-old man with a posttraumatic varus deformity after a fracture of the distal tibia and fibula 26 years ago. The anteroposterior view shows the asymmetric osteoarthrosis of his tibiotalar joint due to the altered load distribution.
Tobacco use should be considered a relative contraindication to supramalleolar osteotomy.
Disorders that alter the bone quality and healing capacity (medication, osteoporosis, age) should be assessed carefully.
Physical examination should include the following:
Drawer test and talar tilt test to assess ankle joint stability
Assessment of the inversion and eversion force to exclude peroneal tendon insufficiency
Subtalar range of motion
Coleman block test to exclude a forefoot driven hindfoot varus
IMAGING AND OTHER DIAGNOSTIC STUDIES
Weight-bearing radiographs of the entire foot, the ankle, the tibial shaft (full-length radiographs) and the Saltzman hindfoot view are necessary to assess the nature and location of the deformity. Unless deformity at the level of the knee joint or the femur can be excluded clinically, whole lower-limb radiographs are obtained.
Next to conventional radiography, computed tomography (CT) and magnetic resonance imaging are not routinely required. However, they could be of value when assessing osteochondral lesions and peroneal tendon disorders or evaluating the aspect of the ligament insufficiency.
SPECT-CT has been found to be a valuable tool for the assessment and staging of osteoarthritis in asymmetric osteoarthritis of the ankle joint.
DIFFERENTIAL DIAGNOSIS
Symmetric or end-stage osteoarthritis
Muscular imbalance (eg, in neurologic disease)
Forefoot-driven hindfoot deformities
NONOPERATIVE MANAGEMENT
Asymptomatic, moderate malalignment usually is treated conservatively.
Malalignment that is due to forces from the neighboring structures, such as plantarflexed first metatarsal or unbalanced muscle forces can be treated with physiotherapy or shoe wear modifications. Deforming forces, such as forefoot abnormalities or muscular imbalance, may require surgical procedures other than supramalleolar osteotomies.
Recommendations for asymptomatic but severe malalignment, such as experienced by the patient in Fig 1, are controversial (surgical versus conservative). Because the deformity is likely to lead to excessive wear, surgery should be considered.
An alternative surgical treatment is the calcaneal displacement osteotomy (medial or lateral). In my opinion, however, correction of malalignment is best performed at the level of the deformity.
SURGICAL MANAGEMENT
Supramalleolar osteotomies are divided into opening and closing wedge osteotomies.
Valgus deformities are usually addressed with a medial closing wedge osteotomy.
Varus malalignment is corrected with a medial opening wedge osteotomy or a lateral closing wedge osteotomy.
The decision between wedge removal laterally and wedge insertion is based on the amount of correction needed. In an extensive medial opening wedge osteotomy, the fibula may restrict the amount of correction possible, so deformities greater than 10 degrees are usually corrected through a lateral approach.
Preoperative Planning
The most important aspect of the preoperative planning is the assessment of the origin of the deformity. Different entities need to be distinguished, and it is mandatory to separate the isolated frontal plane deformity of the hindfoot from complex deformities involving the transverse, sagittal, and coronal planes with or without muscular dysfunction and imbalanced ligamentous structures.
To determine the size of the wedge that should be added or removed to restore anatomic alignment in the ankle, the tibiotalar angle should be measured.
On a standard anteroposterior image of the ankle joint, the tibiotalar angle is the angle between the tibial axis and the tibial joint surface. The wedge to be corrected can be measured out of the radiographs or calculated with the mathematical formula tan θ= H/W, where α is the angle to be corrected, H is the wedge height in millimeters, and W is the tibial width (FIG 2).
An overcorrection of 3 to 5 degrees is recommended by most authors for asymmetric osteoarthritis.
Additional deviation (eg, rotational or translational deformities) must be taken into consideration during the planning of the osteotomy.
Positioning
Positioning of the patient depends on the surgical approach:
Anterior approach: supine position
Lateral approach: lateral decubitus position or supine with a sandbag under the buttock of the affected limb
Medial approach: supine, ipsilateral knee in slight flexion with a sandbag under the calf
Approach
An anterior, lateral, or medial approach can be chosen to correct the deformity. The choice depends on the nature of the deformity, the local soft tissue conditions, and previous approaches.
FIG 2 • Planning of the correction: measuring of the deformity and planning of the wedge to be inserted (lower line of the white triangle indicating the level of the osteotomy).
TECHNIQUES
LATERAL CLOSING WEDGE OSTEOTOMY TO CORRECT VALGUS
Details of Approach
After exsanguination of the leg, a pneumatic tourniquet is inflated on the thigh.
A 10-cm longitudinal slightly curved incision is made along the anterior margin of the distal fibula. If the incision needs to be extended distally, it is curved ventrally to end just distal to and anterior of the lateral malleolus (TECH FIG 1).
The fibula and the tibia are then exposed laterally. To avoid devascularization of the bone, stripping of the periosteum is not performed.
At the distal end of the incision, the anterior syndesmosis is exposed.
The lateral branch of the sural nerve and the short saphenous vein run dorsal to the line of incision and are usually not seen during this procedure. Extended proximal dissection may require identification, exposure, and protection of the branches of the superficial peroneal nerve, however. Cauterization of some of the branches of the peroneal artery, which lie deep to the medial surface of the distal fibula, may be necessary.
TECH FIG 1 • Lateral approach to the distal fibula and tibia.
TECH FIG 2 • Drawing illustrating the Z-shaped osteotomy for shortening of the fibula.
Fibular Osteotomy
In most cases in which a varus deformity is addressed with a lateral closing wedge osteotomy, the fibula needs to be shortened to preserve the congruency in the ankle joint. The shortening can be done by simple bone block removal or a Z-shaped osteotomy. I prefer the Z-shaped fibular osteotomy, which confers greater control of rotation and primary stability compared to a block resection for fibular shortening.
The length of the Z-shaped fibular osteotomy is approximately 2 to 3 cm, starting distally at the level of the anterior syndesmosis.
Kirschner wires can be placed as a reference at the level of the transverse cuts to confirm the location of the osteotomy fluoroscopically.
The osteotomy is then carried out with an oscillating saw.
After the fibula has been mobilized, bone blocks are resected on both ends of the Z based on the amount of the planned shortening (TECH FIG 2).
To avoid interference from the dense syndesmotic ligaments when performing the Z-osteotomy, I routinely direct the proximal transverse cut anteriorly and the distal cut (which typically sits at the syndesmosis) posteriorly.
Lateral Closing Wedge Tibial Osteotomy
To define the desired osteotomy, two Kirschner wires are drilled through the tibia, with the tips converging at the medial cortex, making sure that the angle between the K wires corresponds with the preoperative planning (see Tech Fig 2).
Unless the deformity is located proximal to the supramalleolar area, the wires are directed from proximal to the anterior syndesmosis to the medial physeal scar (TECH FIG 3A).
After fluoroscopic verification of the location of the wires (TECH FIG 3B), the periosteum is incised only at the level of the planned osteotomy and carefully mobilized with a scalpel or periosteal elevator.
The osteotomy is then performed using an oscillating saw cooled with saline or water irrigation to limit thermal injury to bone.
Placing the K-wires accurately avoids cutting through the medial cortex; ideally, the medial cortex should serve as a hinge.
Correction of the deformity must be performed at the center of rotation and angulation of the deformity to avoid relative translational malpositioning of the distal (ankle) and proximal (tibial shaft) fragments.
The gap is then closed, and the osteotomy is secured with a plate. I prefer locking plates that afford optimal primary stability; however, it is imperative that the osteotomy is completely closed when employing locking plate technology (TECH FIG 3C,D).
Prior to locking the plate both proximal and distal to the osteotomy, I use a tensioning device to optimally compress the osteotomy.
I routinely close the periosteum over the osteotomy with 2-0 absorbable sutures.
TECH FIG 3 • A. Placement of the K-wires for guidance of the osteotomy. B. Intraoperative radiograph showing the guide-wires for the tibial osteotomy after the Z-shaped fibula osteotomy. Distal tibia/fibula before (C) and after (D) closure of the osteotomy. Note the shortening of the fibula.
Optimizing Joint Congruity and Securing the Fibula
Fluoroscopically, optimal tibiotalar joint congruity and fibular osteotomy reduction are determined.
Once the joint is congruent, the fibula is secured with screws (in the longitudinal limb of the Z-osteotomy) or a one-third tubular plate (TECH FIG 4).
The subcutaneous tissues and the skin are closed with interrupted sutures.
TECH FIG 4 • Fixation of the fibula with a plate.
MEDIAL OPEN WEDGE OSTEOTOMY FOR CORRECTION OF VARUS DEFORMITY
Anterior Approach
The limb is exsanguinated and the thigh tourniquet is inflated.
The anterior incision is made anteriorly over the distal tibia and ankle, immediately lateral to the tibial crest. The superficial peroneal nerve will cross the distal aspect of the incision and must be protected.
The extensor retinaculum is then divided longitudinally to expose the extensor tendons. The approach uses the interval between the tibialis anterior and extensor hallucis longus tendons.
A longitudinal incision in the extensor retinaculum is made between the anterior tibial tendon and the extensor hallucis longus tendon, starting 10 cm proximal to the joint, about midway between the malleoli (TECH FIG 5)
The anterior tibial tendon is retracted medially, and the tendon of the extensor hallucis longus is retracted laterally, if possible, without opening the tendon sheaths.
The deep neurovascular bundle (anterior tibial artery and deep peroneal nerve), located in the lateral aspect of the approach, must be identified and protected.
The ankle joint is covered by an extensive fat pad that contains a venous plexus and requires partial cauterization.
If tibiotalar joint debridement or exostectomy is required, I make an anterior capsulotomy at this time. If only a supramalleolar osteotomy is planned, however, there is no need to expose the joint.
With all soft tissues and neurovascular structures protected, the anterior surface of the tibia can be exposed. To promote healing of the osteotomy, periosteal stripping should be limited to the osteotomy site.
TECH FIG 5 • Anterior approach to the distal tibia with the interval between the extensor hallucis longus and the anterior tibial tendon and the neurovascular bundle lying lateral to it.
The osteotomy is carried out as described below under Tibial Osteotomy.
Medial Approach
The patient is positioned supine on the operating table; a bump placed under the contralateral hip may improve exposure.
The limb is exsanguinated and the tourniquet is inflated.
The great saphenous vein and the saphenous nerve usually lie anterior to the incision. A 10-cm longitudinal incision is made beginning over the medial malleolus and extending proximally over the distal tibia (TECH FIG 6A).
The skin flaps are mobilized, with care taken not to damage the neurovascular bundle, which runs along the anterior border of the medial malleolus (TECH FIG 6B).
The posterior tibial tendon, which lies immediately on the posterior aspect of the medial malleolus, must be identified and retracted posteriorly. It needs to be exposed, its sheath incised, and the tendon retracted posteriorly to visualize the dorsal surface of the distal tibia.
Tibial Osteotomy
The tibia is exposed with minimal periosteal stripping (TECH FIG 7A).
The plane of the osteotomy is determined under image intensification, and a K-wire is placed from the medial cortex into the physeal scar or, in case of a malunion, at the apex of the deformation (TECH FIG 7B).
The periosteum is then incised at the level of the osteotomy and elevated off the bone using a scalpel or a periosteal elevator. The osteotomy must be planned carefully because placing it inaccurately may lead to relative translation of the distal and proximal fragments, malaligning the ankle joint under the tibial shaft axis.
I recommend using a wide saw blade to create a congruent osteotomy (TECH FIG 7C,D).
Alternatively, a chisel or osteotome may be used instead of the oscillating saw to limit thermal injury to bone.
The correction is based on preoperative planning.
The gap can be filled with allograft (I use Tutoplast Spongiosa; Tutogen Medical GmbH, Neunkirchen, Germany) or autograft iliac crest bone (TECH FIG 7E).
We typically secure the osteotomy with a medial locking plate, but plates with an integrated spacer (eg, Puddu plate; Arthrex, Naples, FL) can be used instead (TECH FIG 7F).
TECH FIG 6 • A, B. Medial approach to the distal tibia.
TECH FIG 7 • A. Intraoperative picture of the K-wire placement. B. Incision and careful stripping of the periosteum. C. Osteotomy of the tibia with an oscillating saw. D. Drawing of the saw cut for a medial opening wedge osteotomy. E. Fill the gap. F. Plate fixation of the osteotomy.
Fixation of the osteotomy is as described for the lateral osteotomy (see earlier).
The tendon sheath of the posterior tibial tendon is reapproximated with 2-0 absorbable sutures, and the subcutaneous tissues and the skin are closed with interrupted sutures. Do not overtighten the posterior tibial tendon sheath because it may create stenosing flexor tenosynovitis.
Case results are shown in TECH FIG 8.
TECH FIG 8 • Preand postoperative radiographs (weight-bearing anteroposterior, lateral, and Saltzman views, respectively) of a 62-year-old male patient with varus osteoarthritis of his ankle joint. The postoperative images are made 1 year after a medial opening wedge osteotomy.
MEDIAL CLOSING WEDGE OSTEOTOMY FOR CORRECTING VALGUS MALALIGNMENT
The technique essentially is the same as for the opening wedge osteotomy described in the previous section with removal of a bone wedge.
K-wire placement is done according to the planned correction (TECH FIG 9A).
The bone wedge is then removed (TECH FIG 9B) and the correction secured with a medial plate.
A clinical example is shown in TECH FIG 10.
TECH FIG 9 • A. K-wire placement for a medial closing wedge osteotomy. B. Wedge removal in a medial closing osteotomy.
TECH FIG 10 • Preand postoperative radiographs (weight-bearing anteroposterior, lateral, and Saltzman views, respectively) of a 58-year-old male patient with valgus osteoarthritis of his ankle joint. The postoperative images are made 1 year after a medial closing wedge osteotomy.
POSTOPERATIVE CARE
The leg is elevated in the immediate postoperative period.
A compressive dressing and splint are maintained for 2 days to diminish swelling.
A short leg non–weight-bearing cast is used for 6 to 8 weeks.
If radiologic evidence of consolidation is present after 6 weeks, partial weight bearing is allowed for 2 weeks, after which the patient advances gradually to full weight bearing.
A rehabilitation program for strengthening, gait training, and range of motion is prescribed 8 weeks after surgery, with gradual return to full activities as tolerated.
OUTCOMES
We have been observing our first series of 74 patients with a varus or valgus deformity of the ankle joint for 49 months (range of 24 to 146 months).
For correction of a varus hindfoot malalignment, a medial opening wedge osteotomy was performed in 14 patients, and a combined lateral closing wedge osteotomy with a correction of the fibula in 13 patients.
Valgus hindfeet were addressed with a medial closing wedge osteotomy in 42 cases and a lateral opening wedge in 5 cases.
At the radiographic assessment after 6 months, all osteotomies showed complete consolidation. Pain reduction was found in all patients, which is similar to earlier reports. Improved radiographic osteoarthritis scores were noted in 75% of the patients. Additionally, patients exhibited a trend toward normalization of gait and function.
COMPLICATIONS
Apart from perioperative complications such as delayed wound healing problems or infection, postoperative concerns include delayed union or nonunion of the osteotomy.
Another potential complication is malunion, resulting from inaccurate alignment of the osteotomy at the time of surgery or postoperative loss of position.
Intraoperative complications include nerve or tendon injury. We ensure that all adjacent neurovascular structures and tendons are identified and protected.
REFERENCES
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