Properties and Implementation of 3-Dimensionally Printed Models in Spine Surgery: A Mixed-Methods Review With Meta-Analysis.

OBJECTIVE: Spine surgery addresses a wide range of spinal pathologies. Potential applications of 3-dimensional (3D) printed in spine surgery are broad, encompassing education, planning, and simulation. The objective of this study was to explore how 3D-printed spine models are implemented in spine surgery and their clinical applications. METHODS: Methods were combined to create a scoping review with meta-analyses. PubMed, EMBASE, the Cochrane Library, and Scopus databases were searched from 2011 to 7 September 2021. Results were screened independently by 2 reviewers. Studies utilizing 3D-printed spine models in spine surgery were included. Articles describing drill guides, implants, or nonoriginal research were excluded. Data were extracted according to reporting guidelines in relation to study information, use of model, 3D printer and printing material, design features of the model, and clinical use/patient-related outcomes. Meta-analyses were performed using random-effects models. RESULTS: Forty articles were included in the review, 3 of which were included in the meta-analysis. Primary use of the spine models included preoperative planning, education, and simulation. Six printing technologies were utilized. A range of substrates were used to recreate the spine and regional pathology. Models used for preoperative and intraoperative planning showed reductions in key surgical performance indicators. Generally, feedback for the tactility, utility, and education use of models was favorable. CONCLUSIONS: Replicating realistic spine models for operative planning, education, and training is invaluable in a subspeciality where mistakes can have devastating repercussions. Future study should evaluate the cost-effectiveness and the impact spine models have of spine surgery outcomes.

Nerve Transfers in Patients with Brown-Séquard Pattern of Spinal Cord Injury: Report of 2 Cases.

BACKGROUND: Use of distal nerve transfer for improving upper limb function has been well described for patients with tetraplegic spinal cord injury and brachial plexus injuries but has not previously been described for Brown-Séquard type spinal cord injury. We describe our experience with 2 cases of combined Brown-Séquard injury and unilateral brachial amyotrophy. CASE DESCRIPTION: Patient 1, a 43-year-old woman, was involved in a motor vehicle accident and sustained left-side C5-7 level hemicord injury causing ipsilateral proximal arm weakness and sensory loss with contralateral hemisensory changes, neuropathic pain, and spasms. At 6 months after injury, she underwent a spinal accessory to suprascapular nerve, radial nerve triceps branch to axillary nerve, and ulnar fascicle to biceps transfer. At 2-year follow-up, she had improved function with Medical Research Council grade 4 power of shoulder abduction, elbow flexion, and internal and external rotation. Patient 2, a 38-year-old man, sustained a C4-5 fracture-dislocation in a motor vehicle accident and associated right-side hemicord injury involving the C5 and C6 myotomes with relatively preserved distal function. At 9 months after injury, he underwent radial nerve triceps branch to axillary nerve division and ulnar nerve fascicle to musculocutaneous nerve brachialis branch transfer. At 8 months after surgery, electromyography demonstrated evidence of further reinnervation of the deltoid muscle. CONCLUSIONS: Our early experience of nerve transfer with 2 patients with combined Brown-Séquard cord injury and brachial amyotrophy indicated acceptable surgical safety and demonstrated encouraging results.

Morphometric Analysis of the Thoracic Intervertebral Foramen Osseous Anatomy in Adolescent Idiopathic Scoliosis Using Low-Dose Computed Tomography.

PURPOSE: The dimensions of the thoracic intervertebral foramen in adolescent idiopathic scoliosis (AIS) have not previously been quantified. Better understanding of the dimensions of the foramen may be useful in surgical planning. This study describes a reproducible method for measurement of the thoracic foramen in AIS using computed tomography (CT). METHODS: In 23 preoperative female patients with Lenke 1 type AIS with right-side convexity major curves confined to the thoracic spine the foraminal height (FH), foraminal width (FW), pedicle to superior articular process distance (P-SAP), and cross-sectional foraminal area (FA) were measured using multiplanar reconstructed CT. Measurements were made at entrance, midpoint, and exit of the thoracic foramina from T1-T2 to T11-T12. Results were also correlated with dependent variables of major curve Cobb angle measured on X-ray and CT, age, weight, Lenke classification subtype, Risser grade, and number of spinal levels in the major curve. RESULTS: The FH, FW, P-SAP, and FA dimensions and ratios are all significantly larger on the convexity of the major curve and maximal at or close to the apex. Mean thoracic foraminal dimensions change in a predictable manner relative to position on the major thoracic curve. There was no statistically significant correlation with the measured foraminal dimensions or ratios and the individual dependent variables. The average ratio of convexity to concavity dimensions at the apex foramina for entrance, midpoint, and exit, respectively, are FH (1.50, 1.38, 1.25), FW (1.28, 1.30, 0.98), FA (2.06, 1.84, 1.32), and P-SAP (1.61, 1.47, 1.30). CONCLUSION: Foraminal dimensions of the thoracic spine are significantly affected by AIS. Foraminal dimensions have a predictable convexity-to-concavity ratio relative to the proximity to the major curve apex. Surgeons should be aware of these anatomical differences during scoliosis correction surgery.

Trigeminal neuralgia associated with Chiari 1 malformation: symptom resolution following craniocervical decompression and duroplasty: Case report and review of the literature.

BACKGROUND: Trigeminal neuralgia (TN) may rarely be the presenting or only symptom of Chiari 1 malformation (CM). Isolated case reports have described resolution of TN following craniocervical decompression where TN is present in association with CM. CASE REPORT: This report discusses an unusual case of pure TN associated with CM that was successfully treated with craniocervical decompression and duroplasty and reviews the limited literature on the subject. CONCLUSION: TN may be the sole presenting symptom of CM and can be successfully managed with craniocervical decompression. Clinicians should be aware of the association of TN with CM and consider surgical management.

Nerve stimulation in thyroid surgery: is it really useful?

BACKGROUND: Monitoring of the recurrent laryngeal nerve (RLN) has been claimed in some studies to reduce rates of nerve injury during thyroid surgery compared with anatomical dissection and visual identification of the RLN alone, whereas other studies have found no benefit. Continuous monitoring with endotracheal electrodes is expensive whereas discontinuous monitoring by laryngeal palpation with nerve stimulation is a simple and inexpensive technique. This study aimed to assess the value of nerve stimulation with laryngeal palpation as a means of identifying and assessing the function of the RLN and external branch of the superior laryngeal nerve (EBSLN) during thyroid surgery. METHODS: This was a prospective case series comprising 50 consecutive patients undergoing total thyroidectomy providing 100 RLN and 100 EBSLN for examination. All patients underwent preoperative and postoperative vocal cord and voice assessment by an independent ear, nose and throat surgeon, laryngeal examination at extubation and all were asked to complete a postoperative dysphagia score sheet. Dysphagia scores in the study group were compared with a control group (n = 20) undergoing total thyroidectomy without nerve stimulation. RESULTS: One hundred of 100 (100%) RLN were located without the use of the nerve stimulator. A negative twitch response occurred in seven (7%) RLN stimulated (two bilateral, three unilateral). Postoperative testing, however, only showed one true unilateral RLN palsy postoperatively (1%), which recovered in 7 weeks giving six false-positive and one true-positive results. Eighty-six of 100 (86%) EBSLN were located without the nerve stimulator. Thirteen of 100 (13%) EBSLN could not be identified and 1 of 100 (1%) was located with the use of the nerve stimulator. Fourteen per cent of EBSLN showed no cricothyroid twitch on EBSLN stimulation. Postoperative vocal function in these patients was normal. There were no instances of equipment malfunction. Dysphagia scores did not differ significantly between the study and control groups. CONCLUSION: Use of a nerve stimulator did not aid in anatomical dissection of the RLN and was useful in identifying only one EBSLN. Discontinuous nerve monitoring by stimulation during total thyroidectomy confers no obvious benefit for the experienced surgeon in nerve identification, functional testing or injury prevention.