Archives of Physical Medicine and Rehabilitation
Volume 90, Issue 5 , Pages 741-744, May 2009

Accuracy of Manual Needle Placement for Gastrocnemius Muscle in Children With Cerebral Palsy Checked Against Ultrasonography

Department and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine, Seoul, South Korea

Article Outline

Abstract 

Yang EJ, Rha D, Yoo JK, Park ES. Accuracy of manual needle placement for gastrocnemius muscle in children with cerebral palsy checked against ultrasonography.

Objective

To investigate the accuracy of manual needle placement into gastrocnemius muscle (GCM) for botulinum toxin type A (BTX-A) injection in children with spastic cerebral palsy (CP).

Design

Prospective clinical study.

Setting

University-affiliated hospital.

Participants

A total of 272 injections in GCMs of 39 children with spastic CP who were scheduled to receive BTX-A injections in GCMs.

Intervention

Not applicable.

Main Outcome Measures

The accuracy of manual needle placement was checked against ultrasonography.

Results

The needle was accurately inserted into GCM muscles in 78.7% of cases. Accuracy was 92.6% into gastrocnemius medialis (GM) and 64.7% into gastrocnemuis lateralis (GL). Muscle thickness at the needle insertion site was significantly thinner in GL than GM. Accuracy of GL in the younger age group (<4y, 57.6%) was lower than in the older age group (≥4y, 78.1%). For GM, accuracy in both younger and older age groups was good (>90%).

Conclusions

Injection of the toxin into GCMs through the use of anatomic landmark was acceptable in GM, but not acceptable in GL, especially in young children.

Key Words: Botulinum toxins, Cerebral palsy, Gastrocnemius muscle, Rehabilitation

List of Abbreviations: BTX-A, botulinum toxin type A, CI, confidence interval, CP, cerebral palsy, EMG, electromyograph, GCM, gastrocnemius muscle, GL, gastrocnemius lateralis, GM, gastrocnemius medialis, OR, odds ratio

 

BOTULINUM TOXIN TYPE A produces reversible chemodenervation of muscles, leading to a dose-dependent decrease in muscle spasticity and strength. BTX-A has become widely accepted as a safe, effective approach for managing focal spasticity in children with CP, although many variables influence the outcome of treatment with intramuscular BTX-A.1, 2

One important factor influencing the treatment outcome is the accuracy in delivering the toxin to the target muscle. A wide range of injection techniques has been described, such as manual needle placement using surface anatomy landmarks or palpation, electromyographic guidance, electrical stimulation of muscle, and ultrasonographic guidance.3, 4, 5, 6, 7, 8, 9, 10 Of these, manual needle placement is the most common injection technique used to control spasticity in children with CP.1, 2, 10, 11, 12, 13 In general, manual needle placement is considered to be an acceptable technique for delivering the toxin to large, superficial muscles, but not to small, deeply seated muscles.14, 15, 16, 17, 18, 19

Because spastic equinus is the most common pathologic pattern in the lower limbs of patients with CP,20, 21 the GCM is selected most frequently for BTX-A injections in children. Because it has a clear anatomic structure, manual needle placement is commonly used to deliver the toxin to the GCM. A previous study found that the accuracy of manual needle placement in the GCM was acceptable in juvenile CP,22 while the accuracy of manual needle placement in the GCMs in young children has not been reported. In addition, determining the difference in accuracy between the GL and GM is important because of possible anatomical differences in the 2 bellies of the GCM.

The muscles of young children are smaller than those of adults, and several studies have revealed that all of the muscles in a paretic lower limb were smaller than the nonparetic muscles in adult and juvenile spastic hemiplegic CP.23, 24, 25 Using magnetic resonance imaging, Lampe et al23 reported that the volume of the calf musculature of paretic limbs in children with spastic hemiplegic CP was 73% of the volume of nonparetic limbs in young adults. In addition, Mohagheghi et al24 noted that the GCM thickness in paretic limbs was 20% less in the GL and 10% lower in the GM than in nonparetic limbs. These findings suggest that the size and thickness of the GCM in the paretic limbs of young children with CP are quite small compared with those in adults, and that the GL is smaller and thinner than the GM.26 Therefore, we postulated that the accurate placement of needles for injecting BTX-A into the GCM is not always achieved easily in young children, especially when injecting into the GL.

The appropriate number of injection sites usually depends on the size of the muscle. Injecting a small volume at several sites is preferable, rather than a large volume at a single site. When injecting BTX-A in the GCM, 1 or 2 sites in each head of the GCM are injected.27, 28 A proximal site near the muscle origin (near the motor point) and a distal site at midbelly (near the neuromuscular junction) are commonly chosen to enhance the response.29, 30 The accuracy of manual needle placement into the proximal and distal sites in each head of the GCM has not yet been studied.

Therefore, this study investigated the accuracy of manual needle placement for toxin injection into the GCM and sought to determine whether any differences in accuracy existed between the GM and GL and between proximal and distal sites in children with spastic CP.

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Methods 

The study recruited all children with spastic CP scheduled for BTX-A injections into the GCM who were under the age of 8 years and seen between March 2007 and July 2007. Informed consent was obtained from the parents or guardians before the procedure.

First, topical anesthesia or an oral sedative was administered to ease the pain and anxiety of the subjects. The injection site was determined using anatomic landmarks and palpation. Injections were performed at 2 sites in each head of the GCM: a proximal site near the muscle origin or motor point where the motor nerve enters the muscle and a distal site at midbelly of the muscle bulk near the neuromuscular junction.8 One of the authors (E.J.Y.) inserted a needle into the proximal and distal parts of both heads of the GCM using anatomic landmarks and palpation without radiographic or electrophysiologic guidance. She was not informed whether the needle was inserted in the target muscle accurately during the procedure. Another author (E.S.P.) checked the accuracy of manual needle placement using ultrasonography and repositioned the needle under ultrasound guidance if it was outside the target muscles, and then injected the toxin into the target muscle under ultrasonographic guidance.

We performed B-mode, real-time ultrasonography of the GCM using the Accuvix XQ systema interfaced with a linear transducer (scanning frequency, 8MHz) to check the accuracy of needle placement. All subjects remained in the prone position with their legs straight during the procedure. The location of the needle was confirmed in the transverse view, and the transducer was tilted slightly to check the position of the needle tip precisely if necessary. The transducer was positioned perpendicular to the muscle surface and placed gently on the skin using water-soluble transmission gel to avoid any pressure-induced alterations of the muscle tissue dimensions. Ultrasonographic images captured at the site of needle insertion were used to measure muscle thickness, which was defined as the distance from the superficial to the deep aponeurosis at the thickest portion of muscle in the transverse view (fig 1).

  • View full-size image.
  • Fig 1. 

    Ultrasonographic images of GCM. Thickness is the distance from superficial aponeurosis to deep aponeurosis of inserted muscle. Abbreviations: L, gastrocnemius lateralis; M, gastrocnemius medialis.

To determine the effects of age on the accuracy of manual needle placement, the subjects were classified into a younger age group (age <4y, n=23) and an older age group (age ≥4y, n=16).

Statistical Analysis 

The statistical analysis followed a prespecified analysis plan using the Statistical Analysis System, version 9.1.b We assessed the effect of age (younger vs older), muscle (GM vs GL), and site (proximal vs distal) on the accuracy of placement (accurate vs inaccurate) and muscle thickness. A 3-factor factorial analysis of variance design was employed to investigate the effects of (1) age, (2) muscle, and (3) site on muscles thickness. We determined the effect sizes (partial eta squared, ηp2) for the measures, where the partial eta squared is the proportion of the effect and error variance that is attributable to the effect. Conditional logistic regression was used to compute adjusted ORs and 95% CIs to investigate the effects of (1) age, (2) muscle, and (3) site on accuracy. For all of the tests used, P<.05 was considered statistically significant.

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Results 

The study population consisted of 39 children (20 boys, 19 girls) with spastic CP. Twenty-six patients had spastic diplegia, 10 had spastic hemiplegia, and 3 had spastic quadriplegia. The mean age was 3 years, 8 months (range, 1–7y). In total, 272 needle insertions into the GCM of the subjects were investigated in this study.

The GL muscle was significantly thinner than the GM muscle (F=46.301; P<.01; effect size ηp2=0.153; table 1). No significant differences in muscle thickness were detected between the proximal and distal sites for each head of the GCM (F=0.009; P=.927; see table 1). The thicknesses of both the GM and GL in the older group were significantly greater than in the younger group (F=27.097; P<.01; effect size ηp2=0.096; see table 1). Most interactions between the muscle (GM vs GL) and the others (site and age) are not significant (muscle × site F=0.130, P=.719; muscle × age F= 2.256, P=.134; muscle × site × age F=2.347, P=.127).

Table 1. Comparison of Thickness and Accuracy of Manual Needle Placement
Gastromedialis (n=136)Gastrolateralis (n=136)
Thickness⁎ (mm)Accuracy† (%)Thickness⁎ (mm)Accuracy† (%)
Proximal site
Younger group (n=41)8.7±1.887.86.9±1.8‡46.3
Older group (n=27)9.4±1.6†96.38.2±1.7‡§81.5
Total (n=68)9.0±1.791.37.4±1.9‡59.7
Distal site
Younger group (n=41)8.4±1.890.27.0±1.6‡65.9
Older group (n=27)9.6±1.4§1008.1±1.6‡§74.1
Total (n=68)8.9±1.894.07.5±1.7‡69.6

NOTE. N=272. Values are means ± SDs. Comparisons of muscle thicknesses were made by 3-factor factorial analysis of variance.

⁎Thickness is distance from superficial aponeurosis to deep aponeurosis of inserted muscles.

†Accuracy (%) = (number of accurate insertions/total number of insertions) × 100.

‡P<.05, gastromedialis vs gastrolateralis.

§P<.05, younger group vs older group.

The overall accuracy of manual needle placement in the GCM was 78.7%. The accuracy of manual needle placement in the GL was significantly lower than in the GM (64.7% vs 92.6%; P<.01; OR, 0.21; 95% CI, 0.10–0.43; see table 1; table 2). No significant differences were observed between the accuracy at the proximal part of each head of the GCM and at the distal part at midbelly (see Table 1, Table 2). In addition, the accuracy of manual needle placement was greater for the GM than the GL irrespective of proximal or distal sites (see table 1). The accuracy in the younger group was significantly lower than the values in the older group (P<.01; OR, 3.45; 95% CI, 1.68–7.08; see Table 1, Table 2). In particular, manual needle placement in the GL had low accuracy (56.1%) for the exact location in the younger group. The rate of accurate placement in the GL in the older group was also not high (77.8% accuracy). However, the accuracy in the GM was relatively high in both the younger and older groups (91.3% and 94.0%; see table 1).

Table 2. Multivariate Models of Important Covariates Influencing the Accuracy of Manual Needle Placement
FactorNo. (%) (n=272)PAdjusted OR (95% CI)
Gastromedialis muscle136(50).0000.21(0.10–0.43)
Proximal site136(50).1921.54(0.81–2.94)
Younger group164(60).0013.45(1.68–7.08)

NOTE. Comparisons were made by conditional logistic regression analysis.

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Discussion 

Botulinum toxin injection is widely used in children with CP to manage focal spasticity. It is logical to assume that the accurate delivery of BTX-A is inherently important to good treatment outcomes for reducing the spasticity of the selected muscles because BTX-A has a dose-dependent effect on muscle spasticity and strength. In this study, we determined the overall accuracy of manual needle placement for toxin injection into the GCM and identified significant differences in accuracy between the GM and GL in children with spastic CP.

In pediatric clinical practice, the GCM is the muscle most often treated in patients with CP.8 Most clinical studies of BTX-A injection into the GCM have used manual needle placement without radiologic and electrophysiological guidance.4, 30, 31 Moreover, a recent study showed that manual needle placement was an acceptable technique for injecting toxin into the GCM in juvenile CP.22 In that study, the accuracy of manual needle placement was 78% in the gastrocsoleus when manual needle placement was checked against electrical stimulation. The overall accuracy of manual needle placement in the GCM in our study was 78.7% when it was checked against ultrasound. The overall accuracy in both studies was quite similar, although we found a significant difference in the accuracy of manual needle placement between the GL and GM. The accuracy of manual needle placement was quite high for the GM, but not for the GL. These findings suggest that manual needle placement for toxin injection has a high possibility of improper placement in the GL muscle, especially in young children with CP. To our knowledge, this is the first trial of the accuracy of manual needle placement in each head of the GCM. Because our subjects were under the age of 8 years, we do not know if any differences exist in the accuracy of manual needle placement between the GL and GM in adults or children with CP who are older than 8 years. Further investigation of the accuracy of needle placement in juvenile CP or adults with CP is needed to determine whether manual needle placement is suitable for the GL.

Based on the literature, children with spastic CP have a relatively thin GM and GL compared with normally developing children.24, 32 In addition, the thickness in the paretic limb was lower in the GL than in the GM.24 The thinner GL than the GM observed in our study is in line with previous studies. The difference in thickness of the GL and GM may have led to the difference in the accuracy of manual needle placement between the GL and GM observed in our study. The thickness at the insertion sites for both the GM and GL in the younger group (<4y) was smaller than in the older group (≥4y). The accuracy of manual needle placement was also lower in the younger group than in older group for both the GM and the GL. This age criterion was based on our preliminary experience that there were tendencies of decreasing the accurate injection rate into the lateral head of the GCM, especially when children were younger than 4 years. It was one of our limitations of this study, and a future study is needed to justify this threshold value theoretically.

Furthermore, the thickness of the GM in the younger group was greater than that for the GL in the older group, and the accuracy of manual needle placement for the GM in the younger children was greater than that for the GL in older children. These findings imply that the laterality of each belly of the GCM is more important for placing the needle properly than other factors, such as age and intramuscular location. Therefore, when the toxin is injected into the GL, especially in children younger than 4 years, we recommend that technical guidance methods, such as EMG or ultrasonography, be used to increase the accuracy of muscle localization.

The fact that the BTX-A needles were placed by a single practitioner is another limitation of this study. The accuracy of injection may differ among practitioners and with the practitioner's experience. Although the overall accuracy of injection into the GCM in our study is quite similar to that of a previous study,22 we believe that interpractitioner variability would affect the reliability of an accuracy assessment. Variable needle placement by several practitioners is required to give more weight to our conclusions. Therefore, a future study should check the accuracy of manual needle placement in the target muscle by several practitioners.

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Conclusions 

The accuracy of manual needle placement was assessed using ultrasonography for 272 sites in the GCM of 39 children with spastic CP. The accuracy exceeded 90% for the GM in both the younger and older groups, while it was unacceptable for the GL, especially in the younger group. The accuracy of manual needle placement appears to be related to the muscle thickness at the needle insertion site. These findings suggest that one use technical methods to guide the injection of toxin into the GL, such as electrical stimulation, EMG, or ultrasonography, especially in young children with CP.

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  • a Accuvix XQ system; Medison, Discusser & MEDISON Building, 1003 Daechi-dong Gangnam-gu, Seoul, Korea.
  • b Statistical Analysis System, version 9.1; SAS Institute Inc, 100 SAS Campus Dr, Cary, NC 27513-2414.

 No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated.

 Reprints are not available from the author.

PII: S0003-9993(09)00073-2

doi:10.1016/j.apmr.2008.10.025

Archives of Physical Medicine and Rehabilitation
Volume 90, Issue 5 , Pages 741-744, May 2009

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