Contralateral sacral 1 root transection and transfer for lumbosacral plexus avulsion injuries: A systematic review

Pawan Agarwal; Dhananjaya Sharma

doi:10.4103/isj.isj_25_22

REVIEW ARTICLE

Year : 2023 | Volume : 6 | Issue : 1 | Page : 76-81

Contralateral sacral 1 root transection and transfer for lumbosacral plexus avulsion injuries: A systematic review

Pawan Agarwal, Dhananjaya Sharma
Plastic Surgery Unit, Department of Surgery, NSCB Government Medical College, Jabalpur, Madya Pradesh, India

Date of Submission	23-Mar-2022
Date of Decision	13-May-2022
Date of Acceptance	27-Jul-2022
Date of Web Publication	11-Feb-2023

Correspondence Address:
Pawan Agarwal
Plastic Surgery Unit, Department of Surgery, NSCB Government Medical College, 292/293, Napier Town, Jabalpur 482001, Madhya Pradesh
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/isj.isj_25_22

Abstract

Contralateral sacral roots (cS1) transfer to treat avulsion injuries of lumbosacral plexus (LSP) has been described, however; concerns about its safety remain. We performed a systematic review of a hypothesis regarding safety of cS1 transection and transfer for treatment of LSP avulsion injuries from available studies. A literature search on Pub Med, Cochrane database and Goggle scholar was performed using appropriate key words for choosing relevant articles. Two authors independently assessed the methodological quality of selected articles using Brink’s criteria and results were analysed using level of evidence. The literature search retrieved a total of 877 publications; out of which 9 articles met the inclusion criteria and were reviewed. 6 articles were investigated for both the reliability and validity and 3 articles evaluated qualitatively; all were of limited quality. Though all studies showed that cS1 nerve root transfer leads to improvement in motor power of muscles and sensory recovery neurotised by cS1 with transient donor site morbidity however; evidence is limited. cS1 nerve root transection and transfer for the repair of LSP avulsion injury appears to be a safe option but the evidence is limited and further validation of this finding is needed.

Keywords: Avulsion, contralateral cervical roots, contralateral sacral roots, lumbosacral plexus, S1 nerve root, systematic review

How to cite this article:
Agarwal P, Sharma D. Contralateral sacral 1 root transection and transfer for lumbosacral plexus avulsion injuries: A systematic review. Indian Spine J 2023;6:76-81

How to cite this URL:
Agarwal P, Sharma D. Contralateral sacral 1 root transection and transfer for lumbosacral plexus avulsion injuries: A systematic review. Indian Spine J [serial online] 2023 [cited 2023 Mar 27];6:76-81. Available from: https://www.isjonline.com/text.asp?2023/6/1/76/369570

Introduction

Sacral plexus injuries are uncommon due to their protected position within the pelvis but massive trauma to pelvis may lead to its traction injury in 40–52% cases.^[1],[2],[3] High velocity trauma causes sacral fractures and concomitant pelvic ring injury is associated with higher incidence of lumbosacral plexus (LSP) injury leading to major long-term morbidity.^[4]

The natural history of the sacral plexus injury denotes that full spontaneous recovery is rare. Therefore if untreated, LSP avulsion injury causes severe functional disabilities such as loss of motor function in the lower extremity, impaired bowel, bladder, sexual function and sensory disturbances such as burning, dysesthesia and causalgia.^[5],[6] The incidence of nerve damage in traumatic lesions is much higher than believed and many undiagnosed plexus injuries and limited treatment strategies could lead to insufficient functional recovery, poor results and unfavourable rehabilitation.^[6],[7]

There are very few articles on surgical treatment of lumbar and sacral plexus injury. Complexities of these injuries and limited surgical options demand out of box innovative thinking for their management. Nerve transfers can be used to treat these injuries however; in cases of avulsion injuries ipsilateral donor nerves are also damaged and not available.^[8],[9] Contralateral C7 (cC7) transfer is an established safe option for managing selected patients with brachial plexus avulsion injuries and gives good results.^[10] Apprehension about safety and loss of any function resulting from cS1 sacrifice are restraining many researchers to apply similar strategy to treat avulsion injuries of LSP by cS1transfer.^[11] This systematic review addresses this important gap on the subject.

Materials and Methods

Search strategy

Systematic literature search was performed and the PRISMA guidelines were followed.^[12] Google search was used to look for the relevant articles in Pub Med, Cochrane database and Google scholar using following keywords: lumbosacral plexus, avulsion, contralateral sacral roots transfer combined with “Or” and “And” [Figure 1]. For Cochrane handbook for systematic review, sources to search included bibliographic databases, journals, and other non-bibliographic-database sources. All articles in English language from January 1980 to December 2020 were included. The collected articles were assessed on following criteria: articles must have motor power recovery of muscles and sensory recovery of recipient nerve of cS1 and donor site morbidity as an outcome and contralateral sacral 1 root transection/ transfer as an intervention. The recovery must be objectively scored using a clinical MRC scale or electrodiagnostic studies data. Some electrodiagnostic studies assessing the S1 innervated muscles by electric stimulation which gives indirect evidence of morbidity of cS1 transection were reported separately in the results section.

Figure 1: Showing PRISMA flow chart

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Inclusion and exclusion criteria

Original experimental/clinical studies reporting results of cS1 nerve transection and transfer for LSP injury, donor site morbidity, and clinical and electrodiagnostic improvement in muscles power supplied by S1 root were included. Studies with unclear results, lack of extractable data about lumbosacral plexopathy, ventral root re-implantation, stem cell therapy, imaging studies, neuropathic pain, gene therapy, unpublished and ongoing studies and articles without English full text were excluded. Descriptive data were extracted; these included the injury type, type of surgery, donor site morbidity, sensory/ muscles strength recovery and final results.

Data extraction

Two authors independently assessed titles and abstracts of all included articles. All articles that were not relevant to this study were excluded. All the articles relevant to the study were included and reviewed. After review of articles disparity was resolved through discussion with a third evaluator. The reference list of included articles was also searched, and those references that fit the inclusion criteria were also included. The data were extracted and recorded: the first author, year of publication, origin/country, study design, study sample, measurement method and valid information for evaluating the reliability and validity of cS1 nerve transfer were analysed.

Quality assessment

The methodological quality of each selected article was assessed using the criteria proposed by Brink et al.^[13] The Brink criteria include 13 items scored as ‘yes’, ‘no’ or ‘n/a’ and a score of <60% was considered as low quality. Two authors assessed the methodological quality of selected articles and disparity was resolved through discussion with a third evaluator [Table 1].

Table 1: Methodological quality of the selected articles as per Brink et al.^[13]

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Data analysis

A meta-analysis was not attempted due to the heterogeneity of tests, small number of patients, no numerical value of results leading to direct comparison of reliability studies inappropriate.

Results

Articles selection

The review process of the articles is depicted as PRISMA flow diagram^[12] [Figure 1]. The systematic literature review retrieved a total of 877 publications; out of which 9 publications met the inclusion criteria and were analysed.

Methodological quality of selected articles

All 9 studies which assessed the effects of transection /transfer of cS1 were of low quality (score <60%). The raters were not defined, examination order was variable or no description of reference test or standard procedure, hence blinding was not done.

Characteristics of selected articles

Out of 9 selected articles published between 1983 and 2015 most were from China (6 studies), USA (2 studies) and Denmark (1 study). All the 9 articles were prospective. Only 6/ 9 assessed the transection /transfer of cS1 while 3 were electrodiagnostic studies assessing the S1 innervated muscles by electric stimulation which gives indirect evidence of morbidity of cS1 transection.

The recipient nerve of cS1 nerve root was inferior gluteal nerve and the branch of the sciatic nerve innervating the hamstrings. Motor power recovery of muscles and sensory recovery were graded with Medical Research Council (MRC) scale.^[14] These recoveries were considered to be effective only when the scores were equal to or greater than M3 and S3, respectively. At the same time donor site morbidity of cS1 was also analysed. Following were the main conclusions from 9 studies (6 clinical and experimental, 3 electrodiagnostic).

S1 root does not contribute to any specific motor action that is controlled solely by S1.

S1 mainly innervates the peroneus longus, gluteus medius/ maximus, biceps femoris, medial/ lateral gastrocnemius and extensor digitorum brevis. However, innervation by S1 to each muscle is not its sole supply but is supplemented by L4, L5, S2 and S3.^[15] When S1 root is injured, fibres from the L4, L5, S2 and S3 nerve roots can regenerate and re-innervate the affected muscles. The highest percentage supplied by S1 is 51.38% to the lateral gastrocnemius which is an expendable muscle.^[16]

Formation of brachial and lumbosacral plexuses are similar and C7 and S1 roots form the central root of each plexus with considerable cross-innervation with upper and lower roots. Therefore after sacrifice of C7 and S1 roots, neighbouring roots can compensate for the lost functions.^[10],[17]

S1 nerve transection results in weakness of ankle plantar flexion (gastrocnemius muscle being partially innervated by S1), possible weakness of toe flexion, loss of sensation on the lateral edge of the foot and loss of ankle reflex. However loss of this reflex does not create loss of function. Both sensory and motor functions recover gradually, clinically and electro-physiologically, to normal within 1.5 year.^[18]

It is now known that muscles receive innervation from 3 to 4 spinal segments.^[15]

The multiple roots division in rats on function of lower extremity concluded that cutting one nerve root did not show an evident functional loss in the experimental limb.

Three electrodiagnostic studies of lower lumbar and sacral roots concluded that S1 innervated muscles are gluteus maximus, medial and lateral gastrocnemius.^{[15],[19],[20]}

The basic characteristics and main conclusions of these 9 publications are shown in [Table 2].

Table 2: Results of various experimental studies after severing normal S1 root

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Reliability and validity

Level of evidence

Limited evidence for safety was found for cS1 root transection and transfer. The low level of evidence was due to the low reliability, validity and availability of limited number of articles on this topic.

Discussion

In such a scenario of preganglionic injury of multiple spinal nerves root avulsion of LSP, the only viable option is nerve transfer using extra/intra-plexal nerves. Neurotization of LSP using transfer of extra-plexal (obturator/genito-femoral or intercostal nerves) is feasible^[21],[22] and has been tried, although with inconsistent results.^[22],[23] One major limitation of ipsilateral intra-plexal donor nerve transfer is that they are also damaged in cases of avulsion injuries and therefore not available. Interest in cS1 for transfer was prompted by the safety and success of cC7 transfer in brachial plexus injuries.^[10] However, obvious concerns about safety of S1 harvest and transfer are donor-site morbidity, a poor rate of recovery of distal extremity function, and inability to control contralateral muscles independently due to co-contraction.^[24],[25] Key prerequisite for any such transfer include a functional donor nerve and its transection should not lead to significant motor or sensory deficit; as sacrificing a major nerve root from the uninjured side may appear unscrupulous. Plantar-flexion in 53% of cases and saddle anaesthesia in all cases has been reported when cS1 roots are injured during higher sacral resection.^{[11],[26],[27],[28]} This is contradicted by safe and successful use of cS1 transfer by some authors.^[16],[29] Such inconsistency in available literature prompted this systematic review.

Clinical and research implications

Many experimental studies in cats, rats and monkeys have shown that cutting L6 nerve root (analogous to S1 in humans) of lumbosacral plexus does not affect lower limb function.^{[17],[28],[30],[31]} In clinical studies cS1 has been transferred to inferior gluteal nerve and the branch of the sciatic nerve which innervate the hamstrings muscles. All patients recovered with the M3 motor function of hamstrings and the glutei so patients could stand and walk without support.^[16],[29] Reinnervation of the muscles was demonstrated by electromyography and there was no residual deficit in function in contralateral limb [Table 1]. Half of cS1 root transfer has been done in order to reduce donor site complications; however, transfer of the entire root is shown to achieve significantly better recovery.^[32],[33] S1 is a suitable donor in treating LSP injuries because its ventral root has a large diameter (2.95 ± 0.57 mm) for anastomosis and it contains large number (41543 ± 3036) of nerve fibres thus providing a good source of axons.^[34] The number of donor nerve fibres is an important determinant for the efficacy of nerve transfer. However, it is not necessary to restore 100% of the receptor nerve fibres to recover the normal function. In fact only 37–40% fibres are required to be restored to maintain the target muscle function.^[34],[35]

After cS1 transfer there is potential for definite improvement of motor function in gluteal and thigh muscles which are the basic requirements for standing and walking however distal leg muscles gain minimal benefits.^[6],[36] But any gain in motor power in these proximal muscles is a strong argument in favour of this neurotization; as return of ability to stand and walk are top priorities of these patients and will add to their quality of life.^[37]

To the authors’ knowledge, this is the first systemic review on this subject. However; this review found that the evidence about reliability and validity is of limited quality.

Limitations

Only 6/ 9 studies directly assessed the effect of transection and transfer of cS1 (4 animal studies and 2 human studies). Other 3 studies were electrophysiological studies. There is a strong need for further studies to assess the reliability and validity of cS1 nerve root transection and transfer for LSP avulsion injuries.

Conclusion

cS1 nerve root transection and transfer for the repair of LSP avulsion injury appears to be a safe option but the evidence is of low quality and further validation of this finding need to be done.

Financial support and sponsorship

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Conflicts of interest

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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