Work classification of known Co-Cs.
Abstract
A certain number of spontaneously recovering birth injuries to the brachial (BPI) plexus are known to be accompanied by muscle co-contractions (Co-Cs). The process of aberrant spontaneous regeneration contributes to the appearance of this phenomenon. Treatment strategies are mostly narrowed down to temporarily “switching off” the antagonist, allowing the agonist to perform. Less is known about the incidence of BPI-associated Co-Cs in adults (a-BPI), the control of which mainly presumes the extrapolation of a treatment strategy that has been shown to be effective in infants. Nowadays, surgical reconstruction of independent elbow flexion at BPIs relies heavily on redirection (transfer) of nerves that produce their own Co-Cs. These induced Co-Cs could potentially be reduced. Selecting the appropriate nerve transfer strategy (when the donor pool is narrowing), with its potential impact on the already complex and intricate global and segmental biomechanics of the upper extremity, becomes challenging. The chapter presents the anatomical background for the occurrence of muscular Co-Cs, a work on clinical classification of both regeneration associated and induced Co-Cs, possible surgical strategies, their benefits and limitations, in the presence of regeneration-associated muscle Co-Cs at a-BPI and clinical examples.
Keywords
- adult brachial plexus injury
- nerve transfer
- medial pectoral nerve
- oberlin transfer
- musculocutaneous nerve
- co-contraction
1. Introduction
Brachial plexus injury (BPI) in adults (a-BPI) remains one of the leading causes of permanent and severe disability among all injuries in the peripheral nervous system [1]. The evolution of treatment options from neurolysis through nerve grafting to nerve transfers has led to dramatic improvements in functional outcomes [2]. The timing of the surgical reconstruction has always been strongly dependent on the process of spontaneous regeneration [3]. As the time allotted for spontaneous regeneration passes and no clear clinical and electrophysiological signs of regeneration are seen, the majority of surgeons advocate for active surgical reconstruction [4].
The dynamics of spontaneous regeneration are well described in newborns with obstetric BPI [4, 5]. It is often accompanied by co-contractions (Co-C) of
A rational explanation of the origin of the Co-Cs could be a change in the predominance of root representation within the muscles of the upper extremity in the case of BPI (Figure 1). This predominance is present both under normal conditions (known as “luxury innervation” [9]) and becomes more evident under the described [10, 11] pathological conditions (known as injury/regeneration associated “simple and complex misdirection”). For instance, at nonfunctioning C5-C6 rootlets greater pectoral, triceps brachii, latissimus dorsi muscles, etc. receive motor fascicles from C7-8-Th1, thus, have or receive closely adjoined motor cortex representation. The activation of the closely adjoined motor cortex during voluntary contraction could possibly lead to their co-activation Co-C. The clinically apparent expression of Co-C most probably depends on how close the cortical centers are situated. Functional MRI (cortical mapping) findings partially explain this process [12].
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F1.png)
Figure 1.
Normal representation of the roots’ of the brachial plexus within the muscles of the upper extremity (a similar color represents the same innervation pattern or representation of roots in the muscles and is most likely responsible for the occurrence of co-contraction(s)). SS—suprascapular muscle; IS—infrascapular muscle; BR—brachioradialis; LD—latissimus dorsi muscle; SuppA—supinator antebrachii muscle; ECRL—extensor carpi radialis longus; ECRB—extensor carpi radialis brevis; EDC—extensor digitorum communis; EDP—extensor indicis and digiti minimi; ECU—extensor carpi ulnaris; APL—abductor pollicis brevis; EPB—extensor pollicis brevis; EPL—extensor pollicis longus; FCU—flexor carpi ulnaris; PT—pronator teres muscle; FDS—flexor digitorum superficilalis; FPL—flexor pollicis longus; FDP—flexor digitorum profundus.
2. From clinical observations to systematic approach to classification: what we know exactly
To date, there is no classification of muscular Co-Cs of the upper extremity associated with
Aberrant spontaneous | Induced | ||
---|---|---|---|
Proximal-Proximal | Proximal-Proximal | ||
Proximal-Distal* | Proximal-Distal | ||
Distal-Distal* | Distal-Distal | ||
Antagonistic | Extraplexal | ||
Non-antagonistic | Intraplexal | ||
Only intraplexal | Antagonism** |
Table 1.
Sequential Co-C (see description in the text)
Unknown.
BB—biceps brachii muscle; Pct—greater pectoral muscle; TB—triceps brachii muscle; ECRB/L—extensor carpi radialis brevis et longus; WE—wrist extensors; FE—finger extensors; FCU—flexor carpi ulnaris; FPD4–5—deep flexors of 4–5 fingers; EDC—extensor digitorum communis; Diaphr.—diaphragm; PM—pectoral nerves; MCN—musculocutaneous nerve; UN—ulnar nerve; MN—median nerve; PIN—posterior interosseous nerve.
Currently, injuries to BPI are mainly treated with nerve transfers (NT) [14]. The pool of traditional extra- and intraplexal donor nerves could be narrowed due to cranially (involvement of C4) and/or caudally expanded (involvement of C7-8) BPI, respectively. In most cases, it consists of Oberlin [15], double-fascicular [16], and medial pectoral [12] NTs.
It is well known that any type of NT, especially when a donor-nerve provides motor fascicles to more than a single muscle, could potentially produce co-activation (
Reconstructions strategies in BPI are prioritizing the reanimation of the elbow flexion [3, 19]. Active surgical reconstruction, with both tendon and NTs, provides active elbow flexion in either earlier or later terms [8]. The general principles of NTs are well known [20]. Reconstruction strategies of BPI are strongly dependent on the selection of an appropriate donor nerve, considering the possible functional advantages and disadvantages of each.
Hence, the evaluation of the efficacy of any type of NT is generally narrowed to the identification of either a muscular power (MRC) or a change in a joint angle produced by the recovered muscle, Oberlin or double-fascicular NT have become most popular and have established themselves as a “golden standard” [2]. The induced
On the other hand, the influence of a nerve transfer on the intimate biomechanical correlation between the upper arm and hand movements is underestimated in most cases. Only a few publications have attempted to characterize and define the real meaning of this coordination and the influence of induced proximal-distal co-activation on the affected limb on a global scale [17]. Escudero et al. [17] discovered that at least 39% of patients who received Oberlin transfer were unable to dissociate elbow flexion from wrist/finger flexion. From a biomechanical point of view, this meant that it deeply “confounded” the function of the hand during daily activities [17].
The interaction between aberrant and induced Co-C in the case of BPI, its influence on the global biomechanics of the upper extremity has not received any reflection in the scientific literature at all. This is most likely due to its extremely rare occurrence among all cases of a BPI. Moreover, since the use of reconstructive strategies presumes the return of lost functions and the preservation (or at least not the loss of the majority) of the preserved ones, the following clinical examples could potentially be of great interest.
3. Clinical examples
3.1 Clinical example 1
A 26-year-old man was admitted to our department 2 mos. after a traction-type injury to his right brachial plexus in a motorcycle accident; neurological examination revealed complete injury to the right brachial plexus. A C5-6-7-8 avulsion with no cranial expansion and preserved function to n.phrenicus (C4) was confirmed during the explorative surgery. None of the intra-plexal motor donor nerves were available for transfer at the time of surgery. In order to reanimate active elbow flexion, NT of n.phrenicus to the musculocutaneous nerve (distally to the branches of the coracobrachialis muscle) through approx. 12 cm sural nerve graft was performed. Another NT of the accessory to the suprascapular nerve [21] was performed to reanimate abduction and external rotation of the shoulder.
Physiotherapy was resumed 6 weeks later. 13 mos. after surgery, shoulder abduction (frontal plane) and external rotation were 80° and 40°, respectively. BB recovered to M4 and elbow flexion was near 90°, was associated with breathing “breathing hand”
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F2.png)
Figure 2.
“Breathing hand” andcorrelation between greater pectoral muscle function and finger flexion (late proximal-distal Co-C). EF—elbow flexion; Pct—greater pectoral muscle, FF—finger flexion; N—neutral position; R—rest; C—maximal contraction; max—maximal finger flexion/transverse volar grip.
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F3.png)
Figure 3.
Schematic explanation of the occurrence of late proximal-distal Co-C (Pct-FF) associated with aberrant spontaneous regeneration of initially complete a-BPI (a similar color represents the same innervation pattern or representation of roots within muscles and is most likely responsible for the emergence of co-contraction). SS—suprascapular muscle; IS—infrascapular muscle; BR—brachioradialis; LD—latissimus dorsi muscle; SuppA—supinator antebrachii muscle; ECRL—extensor carpi radialis longus; ECRB—extensor carpi radialis brevis; EDC—extensor digitorum communis; EDP—extensor indicis and digiti minimi; ECU—extensor carpi ulnaris; APL—abductor pollicis brevis; EPB—extensor pollicis brevis; EPL—extensor pollicis longus; FCU—flexor carpi ulnaris; PT—pronator teres muscle; FDS—flexor digitorum superficilalis; FPL—flexor pollicis longus; FDP—flexor digitorum profundus.
3.2 Clinical example 2
A 28-year-old man was admitted to our department 3 mos. after a traction-type injury to the left brachial plexus in a motorcycle accident; neurological examination revealed the complete injury to the left brachial plexus. A C5-6 avulsion with no cranial expansion and preserved function to n.phrenicus (C4) was confirmed during the explorative surgery. None of the intraplexal motor donor nerves were available for transfer at the time of surgery. In order to reanimate active elbow flexion, NT of n.phrenicus was transferred to the musculocutaneous nerve (distally to the branches of the coracobrachialis muscle) through a sural nerve graft approximately 12 cm long. Two other NTs were performed to reanimate flexion, abduction, and external rotation of the shoulder: pars sternocleidomastoideus of the accessory nerve to the axillary nerve through approx. 14 cm sural nerve graft and suprascapular nerve [21] NT, respectively.
Physiotherapy was resumed 6 weeks later. 17 mos. after surgery, shoulder abduction (frontal plane) was 90°. BB recovered to M4, and elbow flexion was near 110°, was associated with breathing—the “breathing hand”
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F4.png)
Figure 4.
“Breathing hand”, shoulder abduction and correlation between greater pectoral muscle function and wrist extension (late proximal-distal* Co-C before wrist arthrodesis). EF—elbow flexion; ABD—shoulder abduction; Pct—greater pectoral muscle, WE—wrist extension; R—rest; C—maximal contraction; max—maximal wrist extension mediated by ECRB.
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F5.png)
Figure 5.
Schematic explanation of the occurrence of late proximal-distal Co-C (Pct-WE) associated with aberrant spontaneous regeneration of initially complete a-BPI (a similar color represents the same innervation pattern or root representation within the muscles and is most likely responsible for the emergence of co-contraction). SS—suprascapular muscle; IS—infrascapular muscle; BR—brachioradialis; LD—latissimus dorsi muscle; SuppA—supinator antebrachii muscle; ECRL—extensor carpi radialis longus; ECRB—Extensor carpi radialis brevis; EDC—Extensor digitorum communis; EDP—Extensor indicis and digiti minimi; ECU—Extensor carpi ulnaris; APL—Abductor pollicis brevis; EPB—Extensor pollicis brevis; EPL—extensor pollicis longus; FCU—flexor carpi ulnaris; PT—pronator teres muscle; FDS—flexor digitorum superficilalis; FPL—flexor pollicis longus; FDP—flexor digitorum profundus.
3.3 Clinical example 3
A 33-year-old man was admitted to our department 5 mos. after a traction-type injury to the left brachial plexus in a motorcycle accident; neurological examination revealed non-functioning supraspinatus and infraspinatus, teres major and minor, deltoid and serratus anterior, biceps brachii (BB), coracobrachialis and brachialis muscles (0 points on the MRC scale—M0); latissimus dorsi muscle—M3; greater pectoral (Pct), all heads of triceps brachii (TB) muscles—M4; wrist (WE) and finger (FE) extensors—M4; wrist and finger flexors, intrinsics of the hand—M5. Clinically visible
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F6.png)
Figure 6.
The pool of available intraplexal motor donor nerves in clinical example 3. Donor(s) are outlined in green; recipient(s) for the corresponding donornerves are outlined inorange: 1—ulnar nerve fascicles to m. flexor carpi ulnaris; 2—1 + proximal median nerve branch to m. pronator teres (double fascicular NT); 3 and 4—lateral and medial pectoral nerves respectively; 5—both lateral and medial pectoral nerves. *- injured roots are represented in black and gray; **—non-injured roots are represented in color; ***—similar color (thus, roots representation) represents same innervation-pattern of the muscles and is responsible, with great probability, for emergence of co-contraction; SS—suprascapular muscle; IS—infrascapular muscle; BR—brachioradialis; LD—latissimus dorsi muscle; SuppA—supinator antebrachii muscle; ECRL—extensor carpi radialis longus; ECRB—extensor carpi radialis brevis; EDC—extensor digitorum communis; EDP—extensor indicis and digiti minimi; ECU—extensor carpi ulnaris; APL—abductor pollicis brevis; EPB—extensor pollicis brevis; EPL—extensor pollicis longus; FCU—flexor carpi ulnaris; PT—pronator teres muscle; FDS—flexor digitorum superficilalis; FPL—flexor pollicis longus; FDP—flexor digitorum profundus.
The patient was diagnosed with cranially expanded C5-6 BPI, C4-5-6 avulsion was confirmed during the explorative surgery. The pool of available intraplexal motor donor nerves is shown in Figure 6.
In order to reanimate active elbow flexion, NT of ulnar nerve fascicles (m.flexor carpi ulnaris) to the musculocutaneous nerve (branches to biceps brachii muscle) or Oberlin 1 transfer was performed. Two other NTs were performed to reanimate flexion, abduction, and external rotation of the shoulder: Somsak [22, 23] and Bahm [21] NT, respectively.
Physiotherapy was resumed 6 weeks later. 15 mos. after surgery, shoulder flexion (sagittal plane), shoulder abduction (frontal plane), and external rotation were within normal ROM values. BB recovered to M4 and elbow flexion was near 90°, was independent. Hand function was severely impaired by the
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F7.png)
Figure 7.
Correlation between BB function and wrist/finger biomechanics (proximal-distal* Co-C during active elbow flexion). ShF—shoulder flexion; ABD—shoulder abduction; IR—shoulder internal rotation; ER—external rotation; EF—elbow flexion; WE—wrist extension; FE—finger extension; N—neutral position; * Induced or regeneration associated proximal-distal Co-C.
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F8.png)
Figure 8.
Function of proximal and distal segments of the upper extremity in case of BPI with Co-C following Oberlin or double-fascicular NT (hypothesis). EXT—elbow extension, reaching an object; FLX—elbow flexion, pulling an object; TB—triceps brachii muscle; Pct—greater pectoral muscle; BB—biceps brachii muscle; FE—finger extensors; WE—wrist extensors; FF—finger flexors; WF—wrist flexors; A—aberrant
This clinical example reflects the
PRO | CONTRA |
---|---|
Oberlin NT could potentially lead to BB recovery with power exceeding M4 and, without confronting function of TB, could possibly produce higher degree of elbow flexion. | Basically, patients without aberrant spontaneous Co-C compensate for the inability to dissociate movements in the proximal and distal segments (the Oberlin phenomenon or effect [8] in almost one-third of cases [6]) with an independent function of wrist extensors, which provides stability and helps to avoid hyperflexion in the wrist joint when reaching (elbow extension) and pulling (elbow flexion) an object. The main contra argument against Oberlin is the occurrence of |
Table 2.
3.4 Clinical example 4
A 37-year-old man was admitted to our department 7 mos. after traction-type injury to left brachial plexus in a motorcycle accident; neurological examination revealed non-functioning supraspinatus and infraspinatus muscles, teres major and minor, deltoid and serratus anterior, biceps brachii (BB), coracobrachialis and brachialis muscles (0 points on the MRC scale—M0); latissimus dorsi muscle—M3; greater pectoral (Pct), all heads of triceps brachii (TB) muscles—M4; wrist (WE) and finger (FE) extensors—M4; wrist and finger flexors, intrinsics of the hand—M5. Clinically visible
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F9.png)
Figure 9.
Pool of available intraplexal motor donor nerves in clinical example 4. Donor(s) are outlined in green; recipient(s) for the corresponding donor nerves are outlined in orange): 1—ulnar nerve fascicles to m. flexor carpi ulnaris; 2—1 + proximal median nerve branch to m. pronator teres (double fascicular NT); 3 and 4—lateral and medial pectoral nerves, respectively; 5—both lateral and medial pectoral nerves. *—Injured roots are shown in black and gray; **—intact roots are represented in color; ***—a similar color (thus, the representation of roots) represents same innervationpattern of muscles and is most likely responsible for theemergence of co-contraction; SS—suprascapular muscle; IS—infrascapular muscle; BR—brachioradialis; LD—latissimus dorsi muscle; SuppA—supinator antebrachii muscle; ECRL—extensor carpi radialis longus; ECRB—extensor carpi radialis brevis; EDC—extensor digitorum communis; EDP—extensor indicis and digiti minimi; ECU—extensor carpi ulnaris; APL—abductor pollicis brevis; EPB—extensor pollicis brevis; EPL—extensor pollicis longus; FCU—flexor carpi ulnaris; PT—pronator teres muscle; FDS—flexor digitorum superficilalis; FPL—flexor pollicis longus; FDP—flexor digitorum profundus.
The patient was diagnosed with cranially expanded C5-6 BPI, C4-5-6 avulsion was confirmed during the explorative surgery. The pool of available intraplexal motor donor nerves is shown in Figure 9.
In order to reanimate active elbow flexion, there was performed an NT of medial pectoral to musculocutaneous nerve distally to the branches of the coracobrachialis muscle. Two other NTs were performed to reanimate flexion, abduction, and external rotation of the shoulder: Somsak [22, 23] and Bahm [21] NT, respectively.
Physiotherapy was resumed 6 weeks later. 14 mos. after the surgery, abduction of the shoulder in the frontal plane was 75°, external rotation was 20°. BB recovered to M3 and elbow flexion was near 40°. Elbow flexion was severely burdened by the conversion from
The injection of botulinum toxin A at the appropriate dose into the long head of the TB was performed. Significant weakening of the long head of the TB was observed 3 mos. after injection. Physiotherapy proceeded and 19 mos. after surgery, the power of BB increased to M4, elbow flexion increased to 90° and BB became partially independent (Figure 10).
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F10.png)
Figure 10.
Correlation between BB function and wrist/finger biomechanics (proximal-distal* Co-C during active elbow flexion). ABD—shoulder abduction; IR—shoulder internal rotation; EF—elbow flexion; WE—wrist extension; FE—finger extension; N—neutral position.
![](http://cdnintech.com/media/chapter/79557/1512345123/media/F11.png)
Figure 11.
Function of proximal and distal segments of the upper extremity in case of BPI with Co-C following medial pectoral to musculocutaneous NT (result). TB—triceps brachii muscle; Pct—greater pectoral muscle; BB—biceps brachii muscle; FE—finger extensors; WE—wrist extensors; FF—finger flexors; WF—wrist flexors; A—aberrant spontaneous non-antagonistic proximal-proximal and induced antagonistic proximal-proximal Co-C; B—aberrant spontaneous proximal-distal sequential Co-C (arrow indicates the direction of action of primary Co-C initiator); C—aberrant spontaneous proximal-distal sequential Co-C associated with elbow flexion (arrow indicates the direction of action of primary Co-C initiator); D—aberrant spontaneous distal-distal sequential Co-C; E—elbow; blue—primary co-contractors; green—independent movement; both colors—partially independent. *—Aggravation of wrist extension.
This clinical example reflects the
The conversion of | The conversion of the |
Table 3.
Pro and contra arguments of utilization of the medial pectoral nerve in case of a-BPI accompanied by aberrant spontaneous proximal-distal Co-C.
4. Summary
We believe that, regardless of all existing limitations, we provide an interesting insight in terms of a compromise solution for a specific case of BPI accompanied by Co-Cs of different types. The study of the natural history of the individual regeneration process, a thorough preoperative evaluation of
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