James J. McCarthy and David A. Spiegel
DEFINITION
Lengthening of the gastrocnemius fascia is commonly performed for conditions in which the patient positions the foot in equinus either while standing or walking.
Equinus is defined as plantarflexion of the ankle. It can be measured both clinically and radiographically.
The most common condition in which this procedure is performed is cerebral palsy, but other disorders, such as idiopathic toe walking, posttraumatic or surgical treatments, and other neuromuscular disorders, such as Duchenne muscular dystrophy, can also result in an equinus of the foot.
Patients with some disorders, such as Charcot-Marie-Tooth disease, may appear to have equinus, but the true deformity is plantarflexion of the midfoot.
ANATOMY
The medial and lateral heads of the gastrocnemius muscles, the soleus and the plantaris muscles, form the triceps surae. Although all are part of the same muscle group, their structure and function differ.
The larger medial head of the gastrocnemius arises from the popliteal surface of the femur just above the medial femoral condyle, and the lateral head originates from the superolateral surface of the lateral femoral condyle.
The medial and lateral muscle bellies insert into a midline tendinous raphe that widens into the aponeurosis of the gastrocnemius at or just above the midcalf. This tendon unites with the soleus and forms the conjoined tendon, which inserts into the calcaneus by way of the tendo Achilles.
The gastrocnemius spans the ankle and knee joint and therefore can plantarflex the ankle or flex the knee.
It typically has fast twitch type II muscle fibers, which are responsible for short, powerful bursts of activity, such as running and jumping.
The soleus lies deep (anterior) to the gastrocnemius muscle. It originates on the proximal tibia and inserts with the gastrocnemius into the conjoined tendon. Contraction results in only ankle plantarflexion. It is made up of primarily slow twitch type I muscle fibers and is responsible for primarily postural control.
The plantaris arises just above the lateral head of the gastrocnemius and inserts into the calcaneus. It is largely vestigial and should be released at the time of surgery.
The gastrocnemius can be selectively released or lengthened either at its origin, which is uncommonly done, or the tendon of the gastrocnemius, proximal to the conjoined tendon.
Lengthening at or below the conjoined tendon (ie, the tendo Achilles) lengthens the entire triceps surae.
PATHOGENESIS
Equinus positioning of the foot can occur due to:
Increased tone or spasticity of the triceps surae muscles
Shortening of some or all of the muscles
Joint contracture
Bony deformity
It is critical to determine the cause of the equinus because the treatment options differ in each circumstance.
The initiating cause of this disorder varies.
Spasticity, weakness, and subsequent shortening of the muscle group can occur secondary to neuromuscular disorders such as cerebral palsy.
Relative shortening of the triceps surae, as occurs when the tibia is lengthened, or fixed positioning of the foot in equinus, such as prolonged casting in plantarflexion, can result in equinus of the ankle.
Bony changes at the ankle due to trauma or congenital disorders may also result in equinus.
NATURAL HISTORY
The natural history varies according to each disease process and the prior treatment history.
In patients with cerebral palsy, equinus tends to worsen if untreated. It may progress from increased tone to muscle tightness, joint contracture, and eventually bony deformity if untreated.
Other disorders, such as idiopathic toe walking, often improve as the patient matures into adulthood.
PATIENT HISTORY AND PHYSICAL FINDINGS
Range of motion of the ankle should be assessed with the ankle in a neutral position.
Hindfoot valgus will allow for false (pseudo) dorsiflexion.
The examination should be performed with the knee extended to assess gastrocnemius tightness and flexed to assess the soleus.
If the foot remains in equinus with the knee flexed, there is shortening of the soleus or joint contracture or bony deformity.
If the ankle can be dorsiflexed with the knee flexed, but not extended, then the equinus is due to gastrocnemius tightness only (Silfverskiöld test).
Observational or instrumented gait analysis is important to integrate the physical findings with functional deficits. The patient should be evaluated walking and running.
Small limitations in dorsiflexion range may have little functional deficit.
Standing and walking or running foot position may differ greatly.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Standard standing lateral radiographs of the feet are the best method to assess ankle equinus.
Bony deformity can also be evaluated from this examination.
FIG 1 • Radiographic measures. Standard standing lateral radiographs of the feet. Angle A: the distal tibial should angle open anteriorly 10 degrees (the angle between a line drawn through the tibia and along the distal surface of the tibia should measure 80 degrees anteriorly, or 78 to 82 degrees). Angle B: the angle between horizontal and a line drawn to the plantar aspect of the os calcis should be 15 degrees (0 and 30 degrees).
The angle between horizontal and a line drawn to the plantar aspect of the os calcis should be 15 degrees (0 and 30 degrees) (FIG 1).
The distal tibial should angle open anteriorly 10 degrees (the angle between a line drawn through the tibia and along the distal surface of the tibia should measure 80 degrees anteriorly).
DIFFERENTIAL DIAGNOSIS
Cerebral palsy, Duchenne muscular dystrophy, and other neuromuscular disorders
Idiopathic toe walking
Congenital (fibular hemimelia)
Bony deformity (posttraumatic, malalignment, asymmetric growth arrest)
Prior immobilization
Prior tibial lengthening
NONOPERATIVE MANAGEMENT
Physical therapy and stretching is the most common form of treatment for mild deformities and is used in an attempt to maintain range gained by other methods.
The knee must be extended and the hindfoot placed in a neutral position when stretching the ankle.
Bracing, nighttime splinting, or both can be used in combination with other techniques. It is primarily used to maintain gains or prevent worsening deformity.
Botulinum toxin causes paralysis by blocking acetylcholine release at the neuromuscular junction.
It can be injected into the gastrocnemius muscle bellies in an attempt to decrease tone.
The effect lasts about 3 months, and therapy or casting can be combined with it.
Serial casting involves a series of short-leg casts that are placed with the knee flexed and gentle dorsiflexion pressure.
They are changed weekly or biweekly, each time with increasingly greater dorsiflexion.
Usually three or four casts are used until satisfactory range is obtained.
Recurrence is common, and if not carefully performed, skin breakdown can occur.
SURGICAL MANAGEMENT
The surgical management of equinus varies depending on the cause.
Lengthening of gastrocnemius fasciae is indicated if.
The gastrocnemius is selectively tight
This results in functional deficits
Conservative (nonoperative) treatment has failed
Preoperative Planning
Planning should involve assessment of the entire patient, especially in patients with underlying neuromuscular disorders.
Isolated lengthening of the gastrocnemius fascia in patients with cerebral palsy and tight hamstrings may result in a crouch gait.
The Silfverskiöld test should be repeated under anesthesia.
The surgeon should be prepared to do additional procedures if lengthening of the gastrocnemius fascia does not result in sufficient dorsiflexion range.
Positioning
The patient can be positioned either supine, with the leg externally rotated to gain access to the posterior medial calf, or prone.
Supine positioning allows other concomitant procedures to be done, but prone positioning allows for easier access.
We typically perform this procedure with the patient in the supine position, with tourniquet control.
Approach
The procedure is classically performed through a 2- to 4-inch incision made posteriorly over the midcalf, with the patient prone.
An incision can be made posteromedially with the patient supine (FIG 2).
FIG 2 • Incision with the patient in the supine position.
TECHNIQUES
STRAYER PROCEDURE
Dissection is carried down to the facial posterior fascia. This should not be confused with the gastrocnemius tendon (TECH FIG 1A).
The saphenous vein must be protected medially and the sural nerve laterally (TECH FIG 1B).
The fascia overlying the (superficial) posterior compartment is divided and the underlying tendon is identified. Often the muscle bellies of the medial and lateral head of the gastrocnemius overlie the tendon and need to be carefully retracted (TECH FIG 1C).
The tendon of the gastrocnemius is identified proximal to the conjoined tendon and the interval in between the gastrocnemius tendon and the underlying soleus fascia may need to be developed. It can be isolated with an instrument (TECH FIG 1D) and carefully divided, avoiding injury to the underlying soleus fascia and muscle (TECH FIG 1E).
The ankle should now dorsiflex to 10 degrees with the knee extended (TECH FIG 1F).
The subcuticular closure is performed in layers, and a cast is placed with the foot in neutral or slight dorsiflexion.
TECH FIG 1 • The Strayer technique. A. Applied surgical anatomy. Accurate incision size is shown in Band in Fig 1. B. Exposure with the sural nerve identified. C. The fascia of the gastrocnemius exposed below the muscle belly. The tendon of the gastrocnemius is isolated with a hemostat (D) and divided with the soleus muscle (and its overlying fascia intact; E). F. Ankle range of motion is now increased to 10 to 15 degrees of dorsiflexion with the knee extended.
BAKER PROCEDURE
This technique is identical to the Strayer technique with the exception of the cut through the aponeurosis of the gastrocnemius tendon.
An inverted-U incision is made through the aponeurosis; the lateral and medial portions remain intact with the underlying soleus muscle (TECH FIG 2A).
The middle (or tongue) portion is dissected from the soleus, and the distal attachments of the lateral and medial portions of the aponeurosis are freed from the tendon (TECH FIG 2B).
After lengthening, the four corners of the overlapping portion of the tendon are secured with sutures (TECH FIG 2C).
The closure and postoperative care are similar to the Strayer procedure.
TECH FIG 2 • The Baker technique. A. Incision. B. The “box” cut in the gastrocnemius fascia. C. The lengthened tendon, with sutures placed.
VULPIUS PROCEDURE
This technique is similar to the Baker technique, except that an inverted-V incision is used to divide the aponeurosis of the gastrocnemius tendon (TECH FIG 3A).
More than one incision can be used if needed (TECH FIG 3B).
TECH FIG 3 • The Vulpius technique. A. Applied surgical anatomy. Accurate incision size is shown in TECHNIQUES FIGURE 2A and reflected in B. The incision in the gastrocnemius is indicated by the dashed line. B.With the fascia of the gastrocnemius and soleus divided, the muscle of the soleus is exposed.
POSTOPERATIVE CARE
Although Strayer and Baker originally described a “toeto-groin cast,” typically a short-leg weight-bearing cast is worn for 4 weeks, with knee immobilizers to keep the knees extended when not ambulatory.
Bracing and nighttime splinting can be used to help maintain foot position.
OUTCOMES
Significant improvements in range of motion, dynamic joint motion during gait, and electromyographic pattern are typically seen.
Little difference has been shown between the different techniques for lengthening the gastrocnemius fascia.
COMPLICATIONS
Lengthening of the gastrocnemius fascia is generally a safe procedure, with few complications.
Overlengthening of the triceps surae is considered to be less likely with this technique than by lengthening more distally at the Achilles tendon. Overlengthening is difficult to treat.
Injury to the sural nerve or saphenous vein is possible but uncommon and carries few long-term deficits.
Recurrence is the most common concern and is probably related more to poor postoperative therapy and splinting than surgical technique.
REFERENCES
· Baker LE. A rational approach to the surgical needs of the cerebral palsy patient. J Bone Joint Surg Am 1956;38A:313–323.
· Etnyre B, Chamber CS, Scarborough NH, et al. Preoperative and postoperative assessment of surgical intervention for equinus gait in children with cerebral palsy. J Pediatr Orthop 1993;13:24–31.
· Javors JR, Klaaren HE. The Vulpius procedure for correction of equinus deformity in cerebral palsy. J Pediatr Orthop 1987;7:191–193.
· Pohl M, Ruckriem S, Mehrholz J, et al. Effectiveness of serial casting in patients with severe cerebral spasticity: a comparison study. Arch Phys Med Rehabil 2002;83:784–790.
· Sharrard WJW, Bernstein S. Equinus deformity in cerebral palsy: a comparison between elongation of the tendo calcaneus and gastrocnemius recession. J Bone Joint Surg Br 1972;54B:272–276.
· Strayer LM. Recession of the gastrocnemius: an operation to relieve spastic contracture of the calf muscle. J Bone Joint Surg Am 1950; 32A:671–676.