Nonorthotic Modalities Encountered in the Management of Cerebral Palsy

By Phil Stevens, MEd, CPO, FAAOP

PERHAPS MORE THAN ANY OTHER POPULATION SEEN WITHIN ORTHOTIC PRACTICE, PATIENTS WITH CP REQUIRE TEAM MANAGEMENT.

Introduction

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In contemplating writing an article on the management of cerebral palsy (CP), I realized I had neglected the topic for too long after I pulled out my copy of The Identification and Treatment of Gait Problems in Cerebral Palsy, and discovered a rather large and still inhabited spider web suspended against the bottom of the book between its front and back covers. Apparently, I was a bit overdue in reviewing the material. At well over 600 pages, the book is not only comprehensive enough to provide ample space for a female Parasteatoda tepidariorum to take up residence, but also canvasses the complexities and considerations associated with a comprehensive understanding of the gait variations in patients with CP.

Within the text, the authors characterize the various attributes encountered in people with CP as primary, secondary, and tertiary abnormalities of gait. Within this construct, primary abnormalities are those that occur as a direct result of the initial brain injury. As complex as the presentations of CP can be in these children, primary abnormalities are limited to the loss of selective motor control, impaired balance, and abnormal tone (Table 1).1

table 1

Table 1: Class, cause, examples, and duration of gait abnormalities in patients with CP.1

Secondary abnormalities occur as the results of the abnormal forces that are imposed upon the developing skeleton due to the primary abnormalities. These are broadly categorized as muscle contracture and abnormal bone growth. In contrast to primary abnormalities, which occur immediately, secondary abnormalities develop over time, consistent with the growth of the child. Similarly, in contrast to primary gait abnormalities, which are permanent, secondary gait abnormalities are, at least theoretically, correctable.

Succinctly put, tertiary gait abnormalities occur as an individual with CP attempts to adapt to his or her primary and secondary gait abnormalities. These visible gait compensations last as long as they are needed and can be reduced or eliminated by the management of the primary and secondary abnormalities that created them.

Among such complexities, it would be the height of both arrogance and naiveté for the clinical orthotist to assume that these primary, secondary, and tertiary abnormalities can be comprehensively managed by orthotic intervention alone. Perhaps more than any other population seen within orthotic practice, patients with CP require team management. This article introduces the pharmaceutical, surgical, and orthopedic modalities that are commonly used with this population to facilitate a broader understanding of the nonorthotic interventions orthotists may encounter when treating patients with CP.

Pharmaceutical Treatments

A number of strategies have been developed to address the abnormal muscle control observed among patients with CP. The most common presentation is hypertonia, which can be managed globally and locally.

Generalized Management

A number of oral medications are frequently used to manage generalized spasticity. The most familiar of these is baclofen, but other medications that may be used include diazepam, dantrolene sodium, tizanidine, clonazepam, and clonidine.2 Importantly, all of these medications have side effects, the most common of which is sedation. As a result, it is not uncommon for the treating physicians to try different medications at different dosages in ongoing attempts to maximize the benefits of spasticity management while minimizing the sedatory and other side effects of the drugs.

Localized Management

When hypertonicity is localized to certain muscle groups, the medical team will often choose to manage it through chemodenervation with localized injections. Intramuscular botulinum toxin (Botox) injections are the most commonly used. Diving briefly into the underlying physiology, Botox works by blocking the acetylcholine receptors at the neuromuscular junction.2 The term Botox is generally reserved for the most common commercial preparation, botulinum toxin- A, whereas the related botulinum toxin-B is commercially referred to as MYOBLOC. Other related preparations include Dysport, Xeomin, and HengLi.2

The dosages of such injections will depend upon variables such as the child's age and weight, the severity of his or her hypertonicity, and the number and locations of the muscles requiring injection.2 The duration of the resulting muscle relaxation is generally between three and four months. Therefore, it is not uncommon for children to receive quarterly injections to maintain the desired effects.

In addition to Botox and its related variants, phenol injections are used, but less commonly. Unlike the selective action of Botox in targeting chemical receptors at the neuromuscular junction, phenol destroys the nerve pathways, though they eventually grow back.2 In contrast to Botox, which requires three to seven days to take effect, the effects of phenol are immediate. Phenol injections are also comparatively less expensive, longer lasting, and more painful, which usually requires the patient to be sedated.

Surgical Treatments

Intrathecal Baclofen Pumps

In addition to its use as an oral medication, baclofen can be administered directly into the intrathecal space of the spinal canal. Because of this direct administration, the required dosage for intrathecal baclofen is calculated in micrograms, which is much less than the dosage required for oral baclofen, which is calculated in milligrams.2 As a result, the undesired lethargy associated with oral baclofen is reduced.

A pump approximating the size of a hockey puck is surgically inserted in the abdominal wall and connected to a catheter that routes the baclofen to the desired location in the spinal canal. The pump and the dosage can be adjusted nonsurgically by the treating physician and other members of the treatment team. Nonsurgical refilling of the pump is required every two to six months. The pump itself eventually requires replacement. Because abrupt baclofen withdrawal constitutes a medical emergency, the use of baclofen pumps is reserved for patients whose families will be compliant with the ongoing follow-up required for its use.2

table 2

Table 2: Pharmaceutical interventions used to decrease hypertonicity in patients with CP.2

Selective Dorsal Rhizotomy

Selective dorsal rhizotomy (SDR) represents another surgical procedure used to manage spasticity. In this procedure the dorsal nerve roots of the lower spine (L2-S2) are surgically exposed and selectively cut to reduce spasticity. General candidacy includes children between the ages of three and eight with diplegic CP. Candidates are generally higher functioning, with Gross Motor Function Classification System (GMFCS) levels I-III; children with greater levels of disability are preferentially managed with intrathecal baclofen as previously described.2 However, progressive centers are also selectively performing this procedure on young adults with CP and patients with hemiplegic CP.

Many patients who undergo SDR relied, to some extent, on their spasticity for function and mobility prior to the procedure. SDR often reveals underlying weakness that was masked preoperatively by spasticity. As a result, extensive physical therapy and strengthening are frequently required post-SDR. Timed correctly, SDR can reduce the risks of subsequent soft tissue contracture and bony deformity.

Orthopedic Procedures

The restrictions in range of motion (ROM) caused by hypertonicity, coupled with the musculoskeletal growth experienced during childhood, results in the secondary abnormalities of gait, muscle contracture, and bony deformities. These can be managed orthopedically through such procedures as muscle releases and lengthening, tendon transfers, and osteotomies. In doing so, surgeons are generally guided by the reasonable goals associated with an individual child's presentations. For ambulatory children functioning at GMFCS levels I-III, procedures are aimed at improving ambulation. For children with more severe limitations, functioning at GMFCS levels IV-V, surgeries are targeted toward improving the comfort of the child and the ability of caregivers to manage the child's overall well-being.2 For example, contractures that interfere with hygiene or threaten to cause potentially painful joint subluxation or dislocation are often managed orthopedically for this group.

Because of the prolonged rehabilitation and recovery that accompany these procedures, when multiple procedures are deemed necessary, they are often performed simultaneously in singleevent, multilevel surgeries. However, this is not absolute, and many patients will undergo orthopedic treatments throughout their growing years.

Variations in surgical preferences and ideologies are common. The chapter in The Identification and Treatment of Gait Problems in Cerebral Palsy by pediatric orthopedic surgeon Tom Novacheck, MD, is used to describe the associated indications and considerations as well as the procedures themselves.3

Triceps Surae Lengthening

A static evaluation of the triceps surae is conducted using the Silfverskiold test to differentiate between contractures of the gastrocnemius (knee extended) and the soleus (knee flexed).3 In children with diplegia and quadriplia, there is almost always a clear distinction between them-contractures of the gastrocnemius are common while contractures of the soleus are rare.

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Dynamically, a differential diagnosis between real and apparent equinus is important. Both are characterized by an initial contact with forefoot and premature heel rise. However, in apparent equinus the pathology is located proximal to the ankle as a lack of ipsilateral knee extension fails to allow initial contact with the hindfoot. The visual misperceptions of apparent equinus have been the cause of many inappropriate heel cord lengthening surgeries.3

Importantly, the integrity of the midfoot throughout stance needs to be considered. In the absence of adequate ROM at the gastrocnemius, many children will obtain the necessary sagittal advancement in gait through midfoot collapse. Thus, they may appear to have adequate ROM at the ankle when it is actually coming at the expense of the structural integrity of the foot.

Finally, the fact that the gastrocnemius is a two-joint muscle must be considered. During midstance, the gastrocnemius reaches its greatest length as the ankle reaches its greatest dorsiflexion, while the knee joint nears maximal extension. As a result, gastrocnemius contracture can manifest at this stage of gait by contributing to excessive knee flexion (i.e., crouch gait).3

A number of lengthening procedures have been developed. True tendo-Achilles lengthening of both the gastrocnemius and soleus are infrequently indicated because of the relative infrequency of soleus contractures and its important role as a posture stabilizing muscle. Rather, targeted gastrocnemius recession is the more common procedure in which the gastrocnemius is divided at its distal insertion, recessed through intraoperative extension of the knee and dorsiflexion of the ankle, and surgically sutured to the underlying soleus fascia. The typical amount of recession required is 2cm.3

Hamstring Tenotomy

While the hamstrings have often been implicated as an underlying cause of crouch gait in patients with CP, a number of gait analysis studies have failed to observe a correlation between static hamstring length (i.e., popliteal angle) and crouch gait. Therefore, dynamic observations are often given greater consideration.3 During the late swing phase of gait, the two-joint hamstrings reach their greatest length as they must allow both hip flexion and knee extension in preparation for loading response. Therefore, the second half of swing phase is the best opportunity to identify spasticity or contracture of the hamstrings.3 The traditional approach of simply assigning hamstring tightness as the cause of crouch gait (stance phase knee flexion) is oversimplified and fails to consider the numerous other potential influences of knee position during midstance.3

Surgical lengthening of the hamstrings is usually confined to medial hamstrings, through intramuscular lengthening of the semitendinosus and fascial stripping of the semimembranosus (leaving the muscle itself intact). The gracilis is also generally released with its distal insertion utilized as part of a rectus femoris transfer. The amount of lengthening performed is decided intraoperatively by achieving a popliteal angle of 30 degrees.3

Rectus Femoris Transfer

Limitations to knee flexion when the patient is prone is suggestive of rectus femoris tightness. Dynamically, the presence of diminished or delayed peak swing phase knee flexion is the accepted indication for a rectus femoris transfer if rectus femoris activity is confirmed through electromyographic (EMG) activity.3 However, other causes of limited swing phase knee flexion are also considered. For example, compromises to hip flexion power at toe-off and ankle plantarflexion power during preswing can also lead to inadequate hip and knee flexion during swing.3

Rather than simply lengthening a spastic rectus femoris, or releasing it altogether, the consensus among orthopedic surgeons is that the best results are obtained when it is transferred distally to one of the hamstrings, converting the two-joint muscle from a hip flexor/knee extensor to a hip flexor/knee flexor. The most common procedure is intramuscular transfer to the distal portion of the gracilis, which is often released as part of a medial hamstring tenotomy. However, transfers to the semimembranosus, semitendinosus, biceps femoris, and iliotibial band have also been used and advocated.3 The tension is set with the knee at 30 degrees, with full knee extension still possible after the transfer.

Psoas Tenotomy

Excessive hip flexor tightness is determined with the Thomas test, ensuring the correct position of the pelvis in which the anterior superior iliac spines are positioned vertically above the posterior superior iliac spines. Excessive lumbar lordosis when a child is lying supine is also suggestive of hip flexor tightness. Dynamically, excessive psoas tightness is suggested by excessive anterior tilting of the pelvis and limited extension of the hip during midstance and terminal stance.3

Lengthening of the psoas is obtained through a tenotomy performed at the pelvic brim, sparing the muscle belly itself to preserve hip flexor function.3

Adductor Tenotomy

Unless severe, static limitations to abduction ROM are rarely sufficient to warrant adductor tenotomy. Because ambulation requires only 10 degrees of hip abduction, even a 15 degree abduction contracture is compatible with gait.3 The greater concern is hip adductor spasticity. Dynamically, the presence of adduction contracture is best suggested by reduced abduction in swing phase as excessive stance phase adduction can be due to a number of confounding influences, including hip joint instability, hip abductor weakness, or leg length discrepancy.3

Surgical lengthening of the adductors among ambulatory patients is generally confined to a tenotomy at the proximal insertion of the adductor longus.3

Conclusion

Given the complexities that result when a child's growth is confounded by abnormal muscle tone and decreased selective motor control, the clinical presentation of CP can be overwhelming. Fortunately, other members of the rehabilitation team have pharmaceutical modalities and surgical procedures to help address these confounding challenges. When asked to care for patients with CP, it is helpful for orthotists to understand the benefits of these modalities and procedures.

Phil Stevens, MEd, CPO, FAAOP, is in clinical practice with Hanger Clinic, Salt Lake City. He can be reached at .

References

  1. Gage, J. R., M. H. Schwartz, S. E. Koop, and T. F. Novacheck, eds. 2009. The Identification and Treatment of Gait Problems in Cerebral Palsy, 2nd ed. London: Mac Keith Press.
  2. Niedzwecki, C. M., D. L. Roge, A. L. Schwabe. 2016. Cerebral palsy. In Braddom's Physical Medicine and Rehabilitation, ed. D. X. Cifu, 1053-72, 5th ed. Philadelphia: Elsevier.
  3. Novacheck, T. F. 2009. Orthopaedic treatment of muscle contracture. In The Identification and Treatment of Gait Problems in Cerebral Palsy, ed. J. R. Gage, M. H. Schwartz, S. E. Koop, and T. F. Novacheck, 445-72, 2nd ed. London: Mac Keith Press.