Costumbres y tradiciones

Surgical intervention aims to improve function, not restore normality. In upper trunk lesions the main surgical goal is restoration of shoulder function and elbow flexion while for complete lesions it is to restore hand function. Overall, primary nerve reconstruction was more successful in upper trunk lesions

compared with complete lesions (Shenaq et al., 2004, Birch et al., 2005, Terzis and Kokkalis, 2010). Microsurgical procedures for OBPP include direct repair, neurolysis, nerve graft or neurotisation (nerve transfer). This section provides a brief description of microsurgery and its role in management of OBPP.

1.9.2.1 Direct repair and neurolysis

Direct repair is rarely used as the gap to be bridged results in excess tension on the nerve. Neurolysis alone, which involves resection of scar tissue from

around and within the nerve, is no longer indicated in OBPP. It has been shown to have inferior outcomes compared with resection and nerve grafting (Clarke et al., 1996, Capek et al., 1998, Lin et al., 2009).

1.9.2.2 Nerve graft

Neuroma resection and nerve grafting is the gold standard for treatment of rupture injuries (Waters and Bae, 2005). A neuroma-in-continuity, often seen in OBPP, is due to failure of the regenerating nerve growth cone to reach

peripheral targets. The criteria supporting resection, or not, of a neuroma-in- continuity varied. Intraoperative nerve action potentials have been used as a prognostic aid. If the nerve action potential dropped more than 50% then neuroma resection and grafting was performed (Shenaq et al., 2004). Other investigations used to guide surgical techniques were: intraoperative inspection of the muscle response to electrical stimulation on the nerve root proximal to the neuroma; pre-operative muscle strength; EMG results and MRI findings

(O'Brien et al., 2006). Nerve grafting is an anatomical reconstruction of the nerve from a viable proximal nerve to one or more distal targets, using a nerve graft. The distal recipient can be at the level of the trunk, division, cord or terminal nerve. The sural nerve is the most commonly harvested nerve for grafting as its removal has minimal impact on sensation in the lower leg.

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Surgical techniques depend on the findings during surgery with a combination of nerve graft and transfer commonly used.

1.9.2.3 Neurotisation (nerve transfer)

The aim of a nerve transfer is to improve axonal flow to a muscle to enhance function. It is used when a nerve graft would be ineffective. Two important considerations when choosing a donor nerve are: it must be expendable,

meaning that its selection will not have a negative impact on its original function, it should provide synergistic function with the intended action as this facilitates relearning post re-innervation (Kozin, 2008).

Improvements in microsurgical techniques have provided greater options for nerve transfers in OBPP. Mostly, they were the only option for re-innervation in complete palsies where avulsion injuries were more prevalent (Waters, 2005, Kozin, 2008). Their use in upper and middle trunk lesions was more

controversial. While indicated in the following scenarios, the final decision varies with individual surgeons. 1) Late presentation of a child i.e. over one year of age, this is because the transfer will reach the muscle before a graft thereby minimising denervation time; 2) conservatively managed children who do not have a good spontaneous recovery; 3) in the presence of good shoulder function but no biceps activity, then an isolated nerve transfer for elbow function can be performed preserving shoulder function; 4) if intraoperative assessment reveals poor root quality or avulsions; 5) at a later stage if initial surgery did not yield a good functional outcome (Kawabata et al., 2001, Kozin, 2008). The next section briefly evaluates current literature on microsurgery outcomes.

1.9.2.4 Evaluation of outcomes in microsurgical intervention

The objective of microsurgery is to improve upper limb function through facilitation of nerve regeneration. The majority of surgical interventions are a combination of techniques. This is reflected in the literature with no studies directly comparing outcomes of one surgical option over another. To ensure the child can use their affected hand to assist in bimanual activity, restoration of hand function is the initial goal of surgery in complete lesions (Krumlinde-

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sundholm and Eliasson, 2003). Improved shoulder and elbow function is the primary goal in upper trunk lesions and a second goal in complete lesions. Substantial improvements in muscle strength have been reported with

combinations of neurolysis, nerve grafting and neurotisation in children with less than antigravity strength in biceps, triceps and deltoid at 6 months (O'Brien et al., 2006). Donor nerves often used to enhance shoulder function are the spinal accessory to suprascapular (Birch et al., 2005) and radial nerve to axillary (Kozin, 2008). Microsurgery has had reported success in useful reanimation of the hand in complete lesions when performed within the first few months of life (Pondaag and Malessy, 2006, Mencl et al., 2015).

Active elbow flexion is crucial for effective functional ability and lack of biceps return presents a challenge to surgeons in the management of OBPP. The transfer of some fascicles of the intact ulnar nerve to the nerve of the biceps was first described by Oberlin in adults (Oberlin et al., 1994). Its use in children with OBPP has been explored in the literature. While the groups have been heterogeneous and small in number they have demonstrated that Oberlin’s procedure was a valid option for elbow flexion recovery in OBPP with good functional outcomes (Al-Qattan, 2002, Noaman et al., 2004). Further larger studies are recommended to strengthen the support for the procedure. Lack of elbow extension can also present a functional problem for children with OBPP. A retrospective study examining restoration of elbow extension using nerve graft or transfer found that lesion type, timing of surgery and surgical technique influenced outcome (Terzis and Kokkalis, 2010). In early cases, <6 months old, intraplexus reconstruction of posterior cord using nerve grafts demonstrated good to excellent results. Extraplexus motor donors in late presentation >7 months or multiple avulsions had more variable results. The average denervation time between birth and surgery for all patients was 18 months (range, 2 months-9 years). The long denervation time in the older group

confounded results and any interpretations should acknowledge this limitation. However, it did highlight the importance of early surgery in appropriate patients to minimise denervation time due to its impact on the success of nerve surgery.

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In conclusion, the role of microsurgery in enhancing nerve regeneration and functional ability in children with OBPP is well recognised. The importance of patient selection, timing of and type of surgical procedure performed is

emphasised with further work necessary to determine the most effective procedures and patient groups.