Tom F. Novacheck
DEFINITION
Psoas and adductor contractures are most common in cerebral palsy but can occur in any neuromuscular condition owing to disuse, muscular imbalance, or spasticity.
The degree of contracture varies depending on the patient's age and the severity of neuromuscular dysfunction.
Detecting hip flexion contracture (psoas) is challenging.
The challenge for the adductors is deciding which muscles to lengthen and how much lengthening to do.
ANATOMY
The psoas is part of the primary hip flexor group, the iliopsoas.
The psoas muscle originates from the transverse processes of the lumbar vertebrae. The muscle belly passes over the sacrum into the pelvis (FIG 1A).
At the level of the pelvic brim (superior pubic ramus), the intramuscular tendon can be found.
At this level, the psoas lies underneath the muscle belly of the iliacus. The femoral neurovascular bundle is superficial to the iliacus (FIG 1B,C).
The psoas and iliacus tendons combine below the level of the pelvic brim to form a common tendon that inserts on the lesser trochanter.
The adductor longus, adductor brevis, adductor magnus, and gracilis are clinically considered the adductor group of the hip. Their origins arise from the pubic and ischial rami as well as the pubic tubercle and they insert medially on the femur (adductors) and proximal tibia (gracilis) (FIG 1D).
The adductor longus has a tendinous origin, the gracilis has a muscular fascia, and the adductor brevis and magnus have muscular origins.
The anterior branch of the obturator nerve lies in the interval deep to the adductor longus and superficial to the adductor brevis, while the posterior branch of the obturator nerve lies in the interval deep to the adductor brevis and superficial to the adductor magnus.
PATHOGENESIS
Hip flexion and adduction contractures develop over time due to:
Lack of typical functional activities
Muscular imbalance between these muscle groups and their antagonists, the hip extensors and abductors, due to either weakness of the antagonists or spasticity of the agonists
A hip flexion contracture is typical at birth and persists in infancy up until the time the child begins to stand and walk. In an older child who has not achieved standing and walking ability, a hip flexion contracture therefore may represent a persistence of the normal fetal alignment.
At birth, the normal amount of hip abduction range of motion is 60 to 90 degrees, significantly greater than the expected range of motion of adults.
Appropriate musculotendinous length develops during growth as the muscle responds to bone growth and stretch associated with typical childhood activities such as walking, running, and playing. Growth occurs at the musculotendinous junction because of the addition of new sarcomeres.
Contractures of these structures do not allow the joint to achieve normal positions for daily activities.
NATURAL HISTORY
Contractures, if severe and persistent, can lead to hip subluxation, hip dysplasia, and ultimately hip dislocation.
Hip dysplasia and especially hip dislocation are most common with more severe cerebral palsy (quadriplegia, minimally ambulatory or nonambulatory, Gross Motor Function Classification System [GMFCS] IV and V) and in L2 or L3 level myelodysplasia because muscular imbalance at the hip is most severe (innervated hip flexors and adductors, paralyzed abductors and extensors).
In more functionally mobile children with cerebral palsy (GMFCS I, II, and III), psoas and adductor contractures lead to anterior pelvic tilt, excessive pelvic motion, and lack of hip extension in terminal stance and contribute to crouch.
Although a scissoring gait is commonly considered to be due to adductor contractures, this visual appearance most commonly results from the combination of hip and knee flexion with internal hip malrotation due to excessive femoral anteversion.
In longstanding cases, hip dysplasia can lead to degenerative arthrosis.
PATIENT HISTORY AND PHYSICAL FINDINGS
Physical examination methods include the following.
Hip flexion–extension range of motion: Normal walking function requires 7 degrees of extension beyond neutral pelvic position. Therefore, even small contractures limit functional range of motion, shorten step length, and induce compensatory movements.
Hip abduction–adduction range of motion: Maximum abduction range of motion during typical walking is only 5 degrees. Therefore, even moderate limitations of hip abduction range of motion may not have functional significance (unless spasticity is also present). Normal hip development may not occur if abduction range of motion is limited.
If resistance is felt as the hip is extended and abducted, spasticity is present. Increasingly severe spasticity increases the risk of development of subsequent contracture. For ambulation, spasticity (even in the absence of contracture) can limit movement.
Hip flexion and hip adduction strength are tested in the supine position. Lengthening a contracted and weak muscle may adversely affect function. Weak, antagonistic muscle groups (hip extensors, hip abductors) predispose to flexion and adduction contractures and contribute to muscle imbalance.
FIG 1 • A. Hip flexor anatomy. The psoas arises from the lumbar spine transverse processes. At the level of the pubic ramus, as it exits the pelvis, it has an intramuscular tendon. Note the proximity of the femoral nerve and artery anteriorly. B,C. Transverse plane anatomy of the hip. B. Even though this cross section is slightly distal to the pubic ramus, the reason for recommending an approach underneath (lateral) to the iliacus is clear. C. If the iliacus is retracted anteriorly and medially, the femoral neurovascular structures are protected by the muscle belly of the iliacus. The psoas muscle and tendon can be directly visualized. D. Adductor anatomy. The surgeon can orient himself or herself by identifying the tendinous adductor longus origin. The pectineus is lateral and the gracilis medial. The anterior branch of the obturator nerve lies on the anterior surface of the adductor brevis (deep to the adductor longus) after emerging from the obturator foramen just lateral to the pectineus.
When examining a child for hip flexion contracture, the examiner should not be misled by the presence of a knee flexion contracture that prevents full extension of the leg. This can be avoided by moving the patient to the side of the examination table and allowing the lower leg to drop off the side of the table.
Femoral anteversion must also be examined for and ruled out (see Chap. PE-27).
Accurately identifying and controlling pelvic position is crucial for evaluating hip extension and abduction range of motion.
For the nonambulatory patient, the examiner should look for hyperlordosis and a flexed, adducted, internally rotated hip. For the ambulatory patient, observation of gait may show hyperlordosis, limited step length, scissoring gait, or crouch gait.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Supine anteroposterior (AP) pelvis radiograph (FIG 2).
Pelvic obliquity
Adducted hip
Lordotic pelvis
Varying degrees of hip dysplasia
Gait analysis may reveal.
Pelvic obliquity with affected side elevated
Limited hip abduction range of motion in late stance and during swing phase
Excessive anterior pelvic tilt with or without excessive pelvic range of motion
Limited hip extension range of motion in terminal stance
FIG 2 • AP pelvis radiographs. A. Common findings of coxa valga (although femoral anteversion cannot be eliminated as a possibility): break in the Shenton line indicating subluxation, incomplete femoral head coverage, pelvic obliquity (right side elevated), mild windswept hips (right adducted), and mild acetabular dysplasia (right greater than left). B. In this case, severe hip flexion contractures result in anterior pelvic tilt. The AP pelvis radiograph results in an inlet view (obturator foramina are not visible).
DIFFERENTIAL DIAGNOSIS
Hip dysplasia or dislocation
Knee flexion deformity
Hip abductor or extensor weakness
Excessive femoral anteversion
Contracture of secondary hip flexors (eg, myelodysplasia)
NONOPERATIVE MANAGEMENT
Physical therapy for range of motion and strengthening
Positioning aids:
Standers
Sleeping prone
Hip abduction pillow, Scottish Rite brace with thoracolumbar extension
Botulinum toxin injections
SURGICAL MANAGEMENT
Preoperative Planning
The AP pelvis radiograph is reviewed to rule out hip dysplasia.
Examination under anesthesia is performed as described above. Under general anesthesia, hypertonicity is no longer present and the true difference between restricted range due to high muscle tone versus musculotendinous contracture can be appreciated.
Also, the secondary hip flexors (tensor fascia lata and sartorius) can be palpated to rule out secondary contracture (uncommon in cerebral palsy but common in myelodysplasia).
Positioning
The patient is positioned supine.
The leg is draped free to allow flexion and extension of the hip and knee joints as well as abduction of the hip.
Care must be taken with draping to ensure access to the anterior pelvis up to the groin crease to allow adequate surgical exposure.
Approach
Various approaches have been described for psoas lengthening.
My preferred incision is a 3to 4-cm oblique incision along the inguinal ligament that starts at the anterior superior iliac spine and is directed inferomedially.3
Surgeons less comfortable with dissecting the abdominal musculature near the inguinal ligament prefer a more proximal incision at the iliac crest with the abdominal musculature taken off the subcutaneous border of the ilium. The psoas tendon is approached at the same level (the pelvic brim) and therefore the exposure of the tendon is more difficult from this more proximal incision.
Sutherland preferred an exposure distal to the inguinal ligament.5
All approaches use the same deep tissue plane underneath (lateral) to the iliacus muscle belly.
The proximity of the femoral neurovascular structures has been well documented and is a cause for caution.4
The surgical concept of psoas lengthening at the pelvic brim was adapted from Salter's description of lengthening the psoas tendon while performing a Salter pelvic osteotomy.
TECHNIQUES
PSOAS LENGTHENING AT THE PELVIC BRIM
Incision and Dissection
An oblique incision is made along the inguinal ligament starting at the anterior superior iliac spine and extending distal and medial (TECH FIG 1A–C).
The external oblique fascia is identified and divided just above its attachment on the inguinal ligament (TECH FIG 1D).
Blunt dissection through the internal oblique and transversus abdominis just medial and adjacent to the anterior superior iliac spine allows access to the inner table of the ilium extraperiosteally (TECH FIG 1E).
The lateral femoral cutaneous nerve typically crosses the surgical wound and is identified and protected, but sometimes it is medial and not encountered.
Tendon Identification and Division
With the hip flexed, a finger is passed down along the superior pubic ramus underneath the iliacus and psoas to identify the psoas tendon by palpation (TECH FIG 2A).
The psoas tendon is visualized by retracting the iliacus medially with an Army-Navy retractor (TECH FIG 2B).
A right-angled clamp is passed around the psoas tendon (TECH FIG 2C).
By isolating it from the surrounding muscle, the structure is confirmed to be the psoas tendon.
Muscle fibers are retracted and the tendon is divided with electrocautery, leaving the muscle intact (TECH FIG 2D).
Any inflexible (tendinous or myofascial tissues) should be divided. Many patients have a psoas minor tendon, which must also be identified and divided. Muscular tissues are left intact to maintain hip flexor function.
TECH FIG 1 • Incision and dissection for psoas lengthening. A. Right hip (patient supine, feet to the left); ilium, and inguinal ligament are marked. B. Skin incision along inguinal ligament starting just distal to anterior superior iliac spine and extending distally 3 to 4 cm. C. Adson forceps identify the inguinal ligament with the external oblique fascia proximal and medial. D. External oblique fascia is divided along the inguinal ligament and retracted by Army-Navy retractors to visualize the internal oblique. E. A hemostat bluntly pierces the internal oblique and transversus abdominis just medial to the anterior superior iliac spine and is passed along the inner table of the ilium extraperiosteally (in this case, the lateral femoral cutaneous nerve was not encountered).
External oblique fascia
TECH FIG 2 • A. With the hip flexed, the interval between the superior pubic ramus and the iliacus is developed with blunt finger dissection to palpate the psoas tendon. B. The psoas tendon is visualized by retracting the iliacus medially with an Army-Navy retractor. C. A right-angled clamp is passed around the psoas tendon. D. The tendon is divided with electrocautery, leaving the muscle intact.
ADDUCTOR LENGTHENING
For the adductors, a short transverse (most often) or longitudinal incision over the palpable origin of the adductor longus is used (TECH FIG 3A).
The adductor longus tendon is separated from the surrounding tissues (pectineus laterally, gracilis medially [TECH FIG 3B], and adductor brevis and anterior branch of the obturator nerve deep).
The adductor longus tendon is divided as proximally as possible (TECH FIG 3C,D). For ambulatory patients, this is typically the only tissue that should be lengthened.
If necessary, for nonambulatory patients and for more severe neuromuscular hip dysplasia, a partial or complete division of the adductor brevis and other contracted tissues can be performed.
TECH FIG 3 • Adductor longus tenotomy. A. A short transverse incision (pubis left, knee right) exposes the tendinous origin of the adductor longus (pectineus laterally, gracilis medially). B. A right-angled clamp isolates the adductor longus tendon and muscle. C. As proximally as possible, the origin is divided. D. The preserved anterior branch of the obturator nerve lies on the adductor brevis.
POSTOPERATIVE CARE
Psoas lengthenin.
Postoperative elevation of the leg is avoided because it leads to a flexed hip position.
Prone positioning is done two or three times a day for at least 30 minutes.
A knee immobilizer promotes not only an extended knee but also an extended hip.
After 3 weeks, an active hip flexor strengthening program is instituted.
Adductor lengthenin.
An abductor pillow is used full time for 3 weeks and part time for the next 3 weeks, and early range of motion is instituted.
After 3 weeks, an adductor strengthening program is instituted.
For both procedures, weight bearing can be instituted as tolerated. These procedures are commonly performed in conjunction with osteotomy surgery, in which case weight bearing is typically begun 3 to 4 weeks postoperatively.
OUTCOMES
Psoas lengthening is commonly performed in conjunction with femoral osteotomy with or without pelvic osteotomy for treatment of hip dysplasia in nonambulatory patients. A redislocation rate of less than 10% can be expected.2
In ambulatory cerebral palsy patients, psoas surgery improves dynamic hip dysfunction. There is no evidence that psoas lengthening causes hip flexor weakness.3
Power production (H3 power burst) is maintained.
When psoas lengthening is performed in conjunction with femoral derotation osteotomy, excessive anterior pelvic tilt may also improve.
COMPLICATIONS
Excessive hip flexor weakness with tendon release at the lesser trochanter1
Femoral neurovascular injury
Early recurrence of flexion–adduction deformity
Worsened anterior pelvic tilt and forward trunk lean when hip flexion deformity is not recognized and treated
Pelvifemoral instability if scissoring gait is treated with inappropriate adductor surgery
REFERENCES
· Bleck EE. Postural and gait abnormalities caused by hip-flexion deformity in spastic cerebral palsy: treatment by iliopsoas recession. J Bone Joint Surg Am 1971;53A:1468–1488.
· McNerney N, Murbarak S, Wenger D. One-stage correction of the dysplastic hip in cerebral palsy with the San Diego acetabuloplasty: results and complications in 104 hips. J Pediatr Orthop 2000;20:93–103.
· Novacheck TF, Trost JP, Schwartz MH. Intramuscular psoas lengthening improves dynamic hip function in children with cerebral palsy. J Pediatr Orthop 2002;22:158–164.
· Skaggs DL, Kaminsky CK, Eskander-Richards E, et al. Psoas over the brim lengthenings: anatomic investigation and surgical technique. Clin Orthop Relat Res 1997;339:174–179.
· Sutherland DH, Zilberfarb JL, Kaufman KR, et al. Psoas release at the pelvic brim in ambulatory patients with cerebral palsy: operative technique and functional outcome. J Pediatr Orthop 1997;17:563–570.