Proximal Hamstring and Adductor Lengthening
DEFINITION
Proximal hamstring lengthenings are primarily performed in the treatment of spastic hip subluxation, mainly in children prior to adolescence.
Based on modeling studies, the hamstrings are a significant contribution to increasing the force in spastic hip disease, which causes hip subluxation. They are also a component that keeps the knees flexed and secondarily encourages flexion combined with spastic hip flexors, which causes the knee to fall into internal rotation and adduction, magnifying the influence of the concomitant spastic adductors.
This posture of hip flexion and internal rotation and adduction, with the addition of high muscle force, tends to drive the hip posterosuperiorly out of the acetabulum.
The primary period during which spastic hip disease occurs is 2 to 8 years of age, although some children are still at risk through their adolescent growth spurt and need to be monitored.
ANATOMY
Hamstring attachments on the pelvis are very broad muscular attachments and do not have a substantial amount of tendon.
The exception to this is that the semimembranosus tends to have a tendinous insertion and may be confused with the sciatic nerve if care is not taken.
There tends to be some broad fascial insertion with both the biceps and the semitendinosus.
PATHOGENESIS
Spastic hip disease is a pathologic force that has both an abnormal direction of the vector and a force vector that is too high caused by spastic muscles.
The muscles, in order of their importance, are the adductor longus, the gracilis, the proximal insertion of the hamstrings, and the iliopsoas.
An important cause of spastic hip subluxation is positioning of the hip into internal rotation and hip flexion and adduction for a significant component of the child's daily posturing.
NATURAL HISTORY
Abnormal hip subluxation typically begins around 2 years of age and then has a progression of about 10% of migration every 6 months if the progression is occurring.
Therefore, physical examination, monitoring of the hip in abduction, and an anteroposterior (AP) pelvis radiograph in which the Reimer migration index is measured every 6 months would be sufficient to pick up early spastic hip disease.
PATIENT HISTORY AND PHYSICAL FINDINGS
The concern for spastic hip disease is primarily present in children with spasticity, although some adolescents will be at risk.
The primary physical examination finding is the limitation of hip abduction with hips extended and knees extended.
Also, a child whose predominant posture both in sitting and lying is with hip flexion, adduction and internal rotation is at high risk.
IMAGING AND OTHER DIAGNOSTIC STUDIES
The primary radiographic investigation is a supine AP pelvic radiograph in which the Reimer migration index is measured.
Normal should be 25% or less at all ages. Abnormal is greater than 30%.
If there is a question whether this is the standard hip subluxation predominantly occurring in the posterosuperior aspect of the acetabulum, a computed tomography (CT) scan may be obtained to fully evaluate the position of the hip joint. However, this is not routinely required.
DIFFERENTIAL DIAGNOSIS
Hip subluxation secondary to developmental hip dysplasia Congenital hip dislocation
Hypotonic hip dislocation
NONOPERATIVE MANAGEMENT
No conservative treatment options have been documented to be efficacious.
There have been several attempts at treating spastic hip subluxation with botulinum toxin injection; however, preliminary evidence suggests that the failure rate is high and the need for later reconstruction will be higher than with adequate surgical release.
SURGICAL MANAGEMENT
Preoperative Planning
The indications for the procedure are a migration index of 30% to 60% in a child who is younger than 8 to 10 years of age and has limited hip abduction, meaning less than 30 degrees of hip abduction with hips and knees extended.
This examination should be performed under anesthesia.
P.602
The goal of the treatment is to have the child lie without any force or pushing with bilateral hip abduction of more than 45 degrees at the end of the operative procedure.
The indication for proximal hamstring lengthening is a popliteal angle of greater than 45 degrees with the child under anesthesia.
Positioning
Proximal hamstring release combined with adductor lengthening is performed with the patient supine and with an adhesive drape placed over the groin.
Approach
There are two approaches to proximal hamstring release.
One is a straight posterior approach. However, this approach has the negative consequences of going through the area of major weight bearing for sitting.
For this reason, it is preferred to do an approach through the medial groin as part of an adductor lengthening going through the fascial compartment of the gracilis.
Only the approach to the gracilis as part of a full adductor lengthening is described here.
TECHNIQUES
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Exposure
An incision is made from the anterior border of the adductor longus for 2 cm posterior in a transverse plane (TECH FIG 1A).
The adductor longus is identified with a longitudinal opening of the fascia realigning the adductor longus and is completely transected, with vigilance to ensure that the anterior branch of the obturator nerve is protected by visualizing it (TECH FIG 1B).
TECH FIG 1 • A. The incision is made from the anterior border of the adductor longus for 2 cm posterior in a transverse plane. B. The adductor longus is exposed and completely transected, making sure the anterior branch of the obturator nerve is protected. (From Miller F. Cerebral Palsy. New York: Springer-Verlag, 2005. Copyright Springer Science and Business Media, Inc.)
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Myotomy
The gracilis fascia is opened and a complete gracilis myotomy is performed (TECH FIG 2A).
If the hip abduction with hip extended and under minimal force is now less than 45 degrees, the anterior branch of the obturator nerve is protected and the adductor brevis is identified, and sequential myotomy is performed until more than 45 degrees of abduction is obtained.
TECH FIG 2 • A. The gracilis is identified and a complete gracilis myotomy performed. B. The anterior branch of the obturator nerve is protected and the adductor brevis identified. A sequential myotomy is performed of the adductor brevis until more than 45 degrees of abduction is possible with minimal force. If the child is not and will not be ambulatory and the hip migration is over 50%, the anterior branch of the obturator nerve is transected. (From Miller F. Cerebral Palsy. New York: Springer-Verlag, 2005.
Copyright Springer Science and Business Media, Inc.)
If the child is not and will not be ambulatory and the hip migration is over 50%, the anterior branch of the obturator nerve is transected (TECH FIG 2B).
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Iliopsoas Tenotomy
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The interval between the adductor brevis and pectineus or the interval between the pectineus and the neurovascular bundle is opened to the iliopsoas tendon.
TECH FIG 3 • The interval between the pectineus and the neurovascular bundle is opened to the iliopsoas tendon. A complete tenotomy of the iliopsoas tendon is performed if the child is nonambulatory. (From Miller F. Cerebral Palsy. New York: Springer-Verlag, 2005. Copyright Springer Science and Business Media, Inc.)
A complete tenotomy of the iliopsoas tendon is performed if the child is nonambulatory. If the child is ambulatory, the tendon is retracted proximally until only the fascia of the psoas is tenotomized, leaving intact the large muscular iliacus (TECH FIG 3).
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Hamstring Lengthening
The fascial compartment of the gracilis is opened posteriorly, and, with digital dissection, the posterior compartment muscles of the hamstrings are separated (TECH FIG 4A).
The interval between the adductor magnus, which does not contract with knee flexion-extension, is separated from the semimembranosus and semitendinosus (TECH FIG 4B).
The femur is palpated with the finger, and then the semimembranosus and semitendinosus and biceps muscles are all separated, leaving the sciatic nerve against the femur (TECH FIG 4C).
The sciatic nerve can be palpated on the posterior aspect of the femur along the linea aspera.
TECH FIG 4 • A. The fascial compartment of the gracilis is opened posteriorly, and the posterior compartment muscles of the hamstrings are separated using digital dissection. B. The interval between the adductor magnus, which does not contract with knee-flexion extension, is separated from the semimembranosus and semitendinosus. C. The femur is palpated with the finger and then the semimembranosus and semitendinosus and biceps muscles are all separated, leaving the sciatic nerve against the femur. D. A right-angled clamp is then placed around the muscle mass and it is pulled anterior into the surgical wound for visualization with the hip extended and the knees flexed. Electrocautery is used and the muscle is transected. (From Miller F. Cerebral Palsy. New York: Springer-Verlag, 2005.
Copyright Springer Science and Business Media, Inc.)
A right-angled clamp is then placed around the muscle mass and it is pulled anteriorly into the surgical wound for visualization with the hip extended and the knees flexed (TECH FIG 4D).
Electrocautery is used and the muscle is transected.
Any fascial or tendinous material is carefully inspected and stimulated with a nerve stimulator to make absolutely sure that it is not the sciatic nerve.
It must be clear that the anesthesiologist has not had the child under paralysis, and there should be good muscle twitches documented by the anesthesiologist.
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Completion and Wound Closure
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The popliteal angle is checked again.
It should have gone from greater than 45 degrees to about 20 to 30 degrees.
The surgeon should not stretch the popliteal angle without palpating the sciatic nerve, which tends to become very tight, and must be careful not to overstretch the hamstrings at this point for fear of causing sciatic nerve palsy.
The wounds are closed with a longitudinal closure of the fascial wound and a transverse closure of the subcutaneous wound and skin wound.
Avoiding
paralytic anesthesia
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Ensure the child is not under paralytic anesthesia so you can use nerve
stimulator to test the sciatic nerve or know that you are close to a nerve when you use electrocautery.
Muscle
release
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Ascertain that enough muscle is released.
Indications for
surgery completion
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When the surgery is complete, the hip should rest at 45 degrees of abduction
with no force in full hip and knee extension.
Avoiding
heterotopic bone formation
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Do not do a complete release of the iliopsoas through the apophysis of the
lesser trochanter, which will lead to heterotopic bone formation.
The popliteal
angle
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Ensure the hamstring release gets the popliteal angle to at least 20 degrees,
but do not stretch hard because this will cause a sciatic nerve stretch.
PEARLS AND PITFALLS
POSTOPERATIVE CARE
The patient is placed in knee immobilizers.
Pain is controlled typically with morphine and spasticity with diazepam given orally or rectally. Diazepam should be used on a standing order for 48 hours.
Care is taken not to overstretch the hamstrings, especially in the first 2 or 3 weeks, for fear of causing sciatic nerve palsy, particularly in individuals with severe contractures.
Removable Velcro enclosed knee immobilizers are used 8 to 12 hours a day.
OUTCOMES
The goal of the surgical treatment is primarily to improve the child's standing ability, if the child is able,
and secondly to treat the spastic hip disease. About two-thirds of patients whose migration index is 30%
to 60% and who are 2 to 8 years old will not require further treatment for their spastic hip disease, and the hip subluxation will resolve either completely or to a major level.
For children whose hip subluxation does not resolve, reconstruction with femoral and pelvic osteotomy may be required.
It is important to monitor hip radiographs in individuals, even those who have responded well at an early age, throughout their whole adolescent growth because recurrent subluxation may occur as late as the adolescent growth period.
After complete maturation of growth, hips should have a migration percentage of less than 40%. There does not need to be further monitoring or concern after the completion of skeletal growth.
COMPLICATIONS
The primary complication is sciatic nerve palsy. If it occurs, sciatic nerve palsy tends to occur from overstretching the nerve in the postoperative period.
Wound infections are rare and can usually be treated with local care.
Heterotopic ossification may occur, especially if the iliopsoas is released through the apophysis of the lesser trochanter.
Proximal hamstring lengthenings during adolescence also run an increased risk of developing heterotopic ossification in the proximal muscle release site.
SUGGESTED READINGS
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Elmer EB, Wenger DR, Mubarak SJ, et al. Proximal hamstring lengthening in the sitting cerebral palsy patient. J Pediatr Orthop 1992;12:329-336.
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Miller F, Cardoso Dias R, Dabney KW, et al. Soft-tissue release for spastic hip subluxation in cerebral palsy. J Pediatr Orthop 1997;17:571-584.
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Miller F, Slomczykowski M, Cope R, et al. Computer modeling of the pathomechanics of spastic hip dislocation in children. J Pediatr Orthop 1999;19:486-492.
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Presedo A, Oh CW, Dabney KW, et al. Soft-tissue releases to treat spastic hip subluxation in children with cerebral palsy. J Bone Joint Surg Am 2005;87(4):832-841.
