Mesenchymal Stem Cell Treatment Perspectives in Peripheral Nerve Regeneration: Systematic Review.

Traumatic peripheral nerve lesions affect hundreds of thousands of patients every year; their consequences are life-altering and often devastating and cause alterations in movement and sensitivity. Spontaneous peripheral nerve recovery is often inadequate. In this context, nowadays, cell therapy represents one of the most innovative approaches in the field of nerve repair therapies. The purpose of this systematic review is to discuss the features of different types of mesenchymal stem cells (MSCs) relevant for peripheral nerve regeneration after nerve injury. The published literature was reviewed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A combination of the keywords "nerve regeneration", "stem cells", "peripheral nerve injury", "rat", and "human" were used. Additionally, a "MeSH" research was performed in PubMed using the terms "stem cells" and "nerve regeneration". The characteristics of the most widely used MSCs, their paracrine potential, targeted stimulation, and differentiation potentials into Schwann-like and neuronal-like cells are described in this paper. Considering their ability to support and stimulate axonal growth, their remarkable paracrine activity, their presumed differentiation potential, their extremely low immunogenicity, and their high survival rate after transplantation, ADSCs appear to be the most suitable and promising MSCs for the recovery of peripheral nerve lesion. Clinical considerations are finally reported.

Comparison of Theiler's Murine Encephalomyelitis Virus Induced Spinal Cord and Peripheral Nerve Lesions Following Intracerebral and Intraspinal Infection.

Hallmarks of Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease (TMEV-IDD) include spinal cord (SC) inflammation, demyelination and axonal damage occurring approximately 5-8 weeks after classical intracerebral (i.c.) infection. The aim of this study was to elucidate the consequences of intraspinal (i.s.) TMEV infection and a direct comparison of classical i.c. and intraspinal infection. Swiss Jim Lambert (SJL)-mice were i.s. infected with the BeAn strain of TMEV. Clinical investigations including a scoring system and rotarod analysis were performed on a regular basis. Necropsies were performed at 3, 7, 14, 28 and 63 days post infection (dpi) following i.s. and at 4, 7, 14, 28, 56, 98, 147 and 196 dpi following i.c. infection. Serial sections of formalin-fixed, paraffin-embedded SC and peripheral nerves (PN) were investigated using hematoxylin and eosin (HE) and immunohistochemistry. I.s. infected mice developed clinical signs and a deterioration of motor coordination approximately 12 weeks earlier than i.c. infected animals. SC inflammation, demyelination and axonal damage occurred approximately 6 weeks earlier in i.s. infected animals. Interestingly, i.s. infected mice developed PN lesions, characterized by vacuolation, inflammation, demyelination and axonal damage, which was not seen following i.c. infection. The i.s. infection model offers the advantage of a significantly earlier onset of clinical signs, inflammatory and demyelinating SC lesions and additionally enables the investigation of virus-mediated PN lesions.

Electrophysiological and etiological evaluation of 119 cases of wrist drop: A single center study.

OBJECTIVE: To explore the pattern of electrodiagnostic findings in cases of wrist drop and compare gender, involved side of the body, and military versus civilian population for the aetiology of wrist drop. METHODS: This cross-sectional study was conducted at Armed Forces Institute of Rehabilitation Medicine Rawalpindi, Pakistan, from August 2013 to December 2014, and comprised wrist drop cases regardless of age or gender. Evaluation was done using XLTEK Neuromax 1004 EMG unit in line with the recommended protocol for electrodiagnostic evaluation of a suspected radial nerve injury(RNI). SPSS 20 was used for data analysis. RESULTS: Of the 119 patients, 97(81.5%) were males, 66(55.5%) were in the 16-30 years' age group, and 96(80.7%) were military personnel. RNI at the mid-arm level was the commonest cause in 88(73.9%) cases. The frequent inciting event was trauma with fracture of the humerus in 39(32.8%) cases. Eighty-four (70.6%) lesions were axonal. Ninety-four (79%) individuals had no associated injury to other nerves. Injuries due to trauma were more frequent in males (p<0.001), on the right side (p=0.046), and in the military population (p=0.05). CONCLUSIONS: RNI at the mid arm level was the commonest cause of wrist drop in our sample and fracture of the humerus was the main inciting event..

Risk of ulnar nerve injury during cross-pinning in supine and prone position for supracondylar humeral fractures in children: a recent literature review.

Aim of this review article is to evaluate the percentage of ulnar nerve lesion during cross-pinning considering the patient's position (supine or prone) on the surgical bed. Comprehensive research was performed by searching in PUBMED, Cochrane Library, ISI Web of Science, SCOPUS and Clinicaltrials.gov from 2005. Children with extension type supracondylar humeral fractures without clinical signs of ulnar nerve lesion at presentation were included. A total of 28 papers were examined including 2147 patients; 1541 underwent a closed reduction and cross-pinning in supine position and 606 in prone position. Among 1541 patients in supine position, 69 (4.5%) suffered from a ulnar nerve injury while among the 606 patients treated in prone position none ulnar nerve lesions were reported. Despite the apparent safety of prone position, further larger studies, comparing the patient's position on the surgical bed, need to be carried out in order to confirm this likelihood.

The distance of the gluteal nerve in relation to anatomical landmarks: an anatomic study.

INTRODUCTION: Gluteal insufficiency is of concern with lateral approaches to total hip arthroplasty. Damage to the branches of the superior gluteal nerve may cause degeneration of the innervated muscles. The direct anterior approach exploits the intermuscular and internerval interval between tensor fasciae latae laterally and sartorius and rectus femoris muscle medially. In this study, the distance of the superior gluteal nerve in relation to anatomical landmarks was determined. MATERIALS AND METHODS: Two experienced surgeons implanted trial components in 15 alcohol glycerol fixed cadavers with 30 hips. The trials were removed, and the main branch of the superior gluteal nerve and muscular branches of the nerve were exposed from lateral. RESULTS: No visual damage to the main nerve branches and the location of the nerve in relation to the greater trochanter were noted by an experienced surgeon. The superior gluteal nerve and its muscular branches crossed the muscular interval between the gluteus medius and tensor fasciae latae muscles at a mean distance of 39 mm from the tip of the greater trochanter. CONCLUSIONS: The direct anterior approach for total hip arthroplasty minimizes the risk of injuring the superior gluteal nerve, which may result in a gluteal insufficiency. Special care should be paid on avoiding overstretching the tensor fasciae latea muscle using minimum force on retractors during surgery and by taking care of the entrance point of the superior gluteal nerve to the tensor fasciae latae.

Retracting Soft Tissue in Minimally Invasive Hip Arthroplasty Using a Robotic Arm: A Comparison Between a Semiactive Retractor Holder and Human Assistants in a Cadaver Study.

BACKGROUND: All surgical procedures in orthopedics involve the retraction of soft tissue. In this study, the performance of 3 assistants holding the medial retractor during minimally invasive hip arthroplasty was compared with a semiactive retractor holder in a cadaver setup. METHODS: A total of 40 measurements on 3 cadavers were carried out with each subject (3 human, 1 robot) measuring each cadaver 10 times. The retractor was equipped with a sensor array on both sides, to measure variations of the retracting pressures over a 2-minute interval. RESULTS: The semiactive retractor holder showed an almost constant performance compared with the test subjects. There was no significant reduction of the applied pressure and almost no variation during the 2-minute interval and across all measurements. CONCLUSIONS: The performance of the semiactive retractor holder was more stable than that of a human assistant, making it suitable for intraoperative usage.

Chitosan nanoparticles loaded with Foeniculum vulgare extract regulate retrieval of sensory and motor functions in mice.

In this study, chitosan nanoparticles (CSNPs) encapsulating Foeniculum vulgare (FV) seed extract (SE) were prepared for the controlled delivery of bioactive phytoconstituents. The prepared CSNPs encapsulating FVSE as sustain-releasing nanoconjugate (CSNPs-FVSE) was used as a potent source of functional metabolites including kaempferol and quercetin for accelerated reclamation of sensory and motor functions following peripheral nerve injury (PNI). The nanoconjugate exhibited in vitro a biphasic diffusion-controlled sustained release of quercetin and kaempferol ensuring prolonged therapeutic effects. The CSNPs-FVSE was administered through gavaging to albino mice daily at a dose rate of 25 mg/kg body weight from the day of induced PNI till the end of the experiment. The conjugate-treatment induced a significant acceleration in the regain of motor functioning, evaluated from the sciatic function index (SFI) and muscle grip strength studies. Further, the hotplate test confirmed a significantly faster recuperation of sensory functions in conjugate-treated group compared to control. An array of underlying biochemical pathways regulates the regeneration under well-optimized glucose and oxidant levels. Therefore, oxidant status (TOS), blood glycemic level and total antioxidant capacity (TAC) were evaluated in the conjugate-treated group and compared with the controls. The treated subjects exhibited controlled oxidative stress and regulated blood sugars compared to the non-treated control. Thus, the nanoconjugate enriched with polyphenolics significantly accelerated the regeneration and recovery of functions after nerve lesions. The biocompatible nanocarriers encapsulating the nontoxic natural bioactive constitutents have great medicinal and economic value.

Primary Radial Nerve Lesions in Humerus Shaft Fractures-Revision or Wait and See.

Background: This study investigates the surgical state-of-the-art procedure for humeral shaft fractures with primary radial nerve palsy based on its own case series in relation to the current and established literature. Methods: Retrospective review of treated cases between January 2018 and December 2022 describing radial nerve palsy after humerus shaft fractures, radiological fracture classification, intraoperative findings, surgical procedure, patient follow-up and functional outcome. Results: A total of 804 patients (463 women and 341 men) with humerus shaft fractures were identified. A total of 33 patients showed symptomatic lesions of the radial nerve (4.1%). The primary lesion was identified in 17 patients (2.1%). A broad and inhomogeneous distribution of fractures according to the AO classification was found. According to the operative reports, the distraction of the radial nerve was found eleven times, bony interposed three times and soft tissue constricted/compressed three times. In every case the radial nerve was surgically explored, there was no case of complete traumatic nerve transection. Four intramedullary nails and thirteen locking plates were used for osteosynthesis. Complete recovery of nerve function was seen in 12 cases within 1 to 36 months. Three patients still showed mild hypesthesia in the thumb area after 18 months. Two patients were lost during follow-up. Conclusions: With this study, we support the strategy of early nerve exploration and plate osteosynthesis in humeral fractures with primary radial nerve palsy when there is a clear indication for surgical fracture stabilisation. In addition, early exploration appears sensible in the case of palsies in open fractures and secondary palsy following surgery without nerve exposure as well as in the case of diagnostically recognisable nerve damage. Late nerve exploration is recommended if there are no definite signs of recovery after 6 months. An initial wait-and-see strategy with clinical observation seems reasonable for primary radial nerve palsies without indication for surgical fracture stabilisation.

"Knowing It Before Blocking It," the ABCD of the Peripheral Nerves: Part D (Approach to the Patient With Nerve Injuries).

"Prevention is always better than cure." However, despite all precautions or preventive measures, sometimes patients develop neurodeficits due to suspected nerve injury in the perioperative period. Assessment and evaluation of the patient's symptoms can provide clues to the causative factors. Such causative factors can be corrected immediately to avoid further deterioration, or some may require further workup. The management plan for such a diagnosed nerve injury depends on the symptoms, the finding of the medical history, and the diagnostic imaging and tests. Simultaneous symptomatic relief in the form of pain medications, steroids, anti-inflammatory drugs, psychological counseling, and reassurance is essential to expedite treatment goals. Diagnosing and treating nerve injuries cannot be laid down as a straightforward part. It is a zigzag puzzle in its own right, playing with time and injury progression. Careful assessment to diagnose the extent of nerve damage plays an important role in treatment plans. It helps decide when to proceed and when to postpone, whether conservative strategies would suffice, or surgical repair would be required. Although most nerve injuries are self-limiting, some cases require surgical intervention that needs to be diagnosed early. The revolution was started by Sunderland in 1945 when he described neurosurgical techniques that drastically changed the entire scenario of nerve repairs. The ultimate effective treatment and full recovery may not be guaranteed, but attempts must be made to achieve the best results. With the patient's interests in mind, it is important to formulate a plan ensuring a good quality of life with minimal impact on their daily activities. Multifactorial nerve injury requires a multidisciplinary approach that primarily includes reassuring, psychological counseling, multimodal analgesia, and neurological and occupational consultations. This article describes the step-by-step approach known as the symptoms categorization-history taking-examination-diagnostic evaluations (SHED) approach to managing patients with peripheral nerve injuries. It also details the various modalities for diagnosing nerve injuries, sequential electrodiagnostic studies, and treatment plans depending on the type and extent of nerve injuries. It will help readers to design a treatment plan based on the patient's symptoms and evaluation results.

Spatial Distribution and Long-Term Alterations of Peripheral Nerve Lesions in Schwannomatosis.

Purpose To examine the spatial distribution and long-term alterations of peripheral nerve lesions in patients with schwannomatosis by in vivo high-resolution magnetic resonance neurography (MRN). Methods In this prospective study, the lumbosacral plexus as well as the right sciatic, tibial, and peroneal nerves were examined in 15 patients diagnosed with schwannomatosis by a standardized MRN protocol at 3 Tesla. Micro-, intermediate- and macrolesions were assessed according to their number, diameter and spatial distribution. Moreover, in nine patients, peripheral nerve lesions were compared to follow-up examinations after 39 to 71 months. Results In comparison to intermediate and macrolesions, microlesions were the predominant lesion entity at the level of the proximal (p < 0.001), mid- (p < 0.001), and distal thigh (p < 0.01). Compared to the proximal calf level, the lesion number was increased at the proximal (p < 0.05), mid- (p < 0.01), and distal thigh level (p < 0.01), while between the different thigh levels, no differences in lesion numbers were found. In the follow-up examinations, the lesion number was unchanged for micro-, intermediate and macrolesions. The diameter of lesions in the follow-up examination was decreased for microlesions (p < 0.01), not different for intermediate lesions, and increased for macrolesions (p < 0.01). Conclusion Microlesions represent the predominant type of peripheral nerve lesion in schwannomatosis and show a rather consistent distribution pattern in long-term follow-up. In contrast to the accumulation of nerve lesions, primarily in the distal nerve segments in NF2, the lesion numbers in schwannomatosis peak at the mid-thigh level. Towards more distal portions, the lesion number markedly decreases, which is considered as a general feature of other types of small fiber neuropathy.

Long-term Follow-up and Histological Correlation of Peripheral Nervous System Alterations in Neurofibromatosis Type 2.

PURPOSE: To examine long-term alterations of the dorsal root ganglia (DRG) and the peripheral nerve in patients with neurofibromatosis type 2 (NF2) by in vivo high-resolution magnetic resonance neurography (MRN) and their correlation to histology. METHODS: In this prospective study the lumbosacral DRG, the right sciatic, tibial, and peroneal nerves were examined in 6 patients diagnosed with NF2 and associated polyneuropathy (PNP) by a standardized MRN protocol at 3 T. Volumes of DRG L3-S2 as well as peripheral nerve lesions were assessed and compared to follow-up examinations after 14-100 months. In one patient, imaging findings were further correlated to histology. RESULTS: Follow-up MRN examination showed a non-significant increase of volume for the DRG L3: +0.41% (p = 0.10), L4: +22.41% (p = 0.23), L5: +3.38% (p = 0.09), S1: +10.63% (p = 0.05) and S2: +1.17% (p = 0.57). Likewise, peripheral nerve lesions were not significantly increased regarding size (2.18 mm2 vs. 2.15 mm2, p = 0.89) and number (9.00 vs. 9.33, p = 0.36). Histological analyses identified schwannomas as the major correlate of both DRG hyperplasia and peripheral nerve lesions. For peripheral nerve microlesions additionally clusters of onion-bulb formations were identified. CONCLUSION: Peripheral nervous system alterations seem to be constant or show only a minor increase in adult NF2. Thus, symptoms of PNP may not primarily attributed to the initial schwannoma growth but to secondary long-term processes, with symptoms only occurring if a certain threshold is exceeded. Histology identified grouped areas of Schwann cell proliferations as the correlate of DRG hyperplasia, while for peripheral nerve lesions different patterns could be found.

Nerve lesions during arthroscopic procedure: a literature overview.

Arthroscopy is more and more popular. Although minimally-invasive, it's not completely free of complications as nerves lesions which can be invalidating for the patient and frustrating for the surgeon with significant economic, psychological and medico-legal implications. The purpose was to review the literature about nerve injuries related to arthroscopy. A scientific literature review was performed in PubMed/Medline, including articles dealing with cases of iatrogen lesions of the peripheral nerves occurred during arthroscopic procedures. These lesions are mainly due to direct damage by nerve section while cutting for making the portals or during surgical maneuvers, or indirect damage due to traction or pressure mechanisms especially for errors in patient positioning. Also the tourniquet can lead to compression and ischemic nerve injury. Arthroscopy can cause both transient and permanent neurological lesions manifested with dysesthesia up to paralysis according to Seddon's classification in neuroapraxia, axonotmesis and neurotmesis. Incidence of complications in general and of nerve injuries during arthroscopy are reported by joint. A rigorous respect for surgical technique and all perioperative precautions, particularly in relation to the positioning of the patient, greatly reduce the risk of nerve injury. The suggested waiting time before surgical nerve revision is 6 months. In the meanwhile the patient should perform physiotherapy constantly and improvements should be evaluated with clinical examination and electromyography 15-20 days after the lesion, and thereafter at 3 and 6 months.

Lymph Node Dissection Morbidity in Thyroid Cancer: An Integrative Review.

Cervical lymphadenectomy is a common procedure for thyroid cancer. Some of the complications are congruent with the complications of thyroid surgery, in particular recurrent laryngeal nerve paresis and hypoparathyroidism as well as bleeding and wound infection. Specific complications of lateral cervical lymph node dissection are injuries to the accessory, phrenic and hypoglossal nerves, and the cervical plexus trunk and injuries, the salivary glands, and the lymphatic system, especially the ductus thoracicus. Most of these complications are very rare with an incidence of <1%. Profound anatomical knowledge and a careful dissection technique make a decisive contribution to minimizing complications.

[Complications of lymph node dissection in thyroid cancer]. / Komplikationen der Lymphknotendissektion beim Schilddrüsenkarzinom.

Cervical lymphadenectomy in thyroid cancer is a frequent intervention with around 20,000 operations per year in Germany. Some of the complications are identical with those in thyroid surgery, such as recurrent laryngeal nerve palsy and hypoparathyroidism as well as postoperative bleeding and wound infection. Specific complications of lateral lymphadenectomy are lesions of the accessory, phrenic and hypoglossal nerves, the sympathetic trunk and cervical plexus as well as lesions of the salivary glands and lymphatic vessels, in particular the thoracic duct. Most of these complications are rare with a frequency of less than 1%. Profound knowledge of the anatomy and a meticulous dissection technique make a decisive contribution to minimizing these complications.

Little finger abduction and adduction testing in ulnar nerve lesions.

We aimed to evaluate the abduction and adduction of the little finger based on a new clinical test in the context of ulnar nerve lesions. We tested little finger abduction and adduction in 34 patients with an isolated ulnar nerve injury and 20 patients with cubital tunnel syndrome. With their forearms supinated, patients were asked to fully abduct their little finger. Then, the examiner held the patients' index, middle, and ring fingers in extension and maximal radial deviation, and then asked the patients to touch their little finger to their radially deviated ring finger. In patients with ulnar nerve injuries, either above or below the elbow, little finger abduction and adduction were impossible. In the patients with cubital tunnel syndrome, 19 had partial paralysis of little finger adduction and one patient had complete paralysis. Abduction and adduction of the little finger is not possible when the ulnar nerve is transected. In cubital tunnel syndrome, this little finger adduction test was able to identify decreased range of motion, possibly indicating muscle weakness.

Novel coronavirus infection and its vaccination-related ocular disease / 国际眼科杂志(Guoji Yanke Zazhi)

The continuous pandemic coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)is a serious threat to human life and health because of high infectious pathogenicity, and it also has posed a new challenge to the current medical model. Many literatures have shown that these changes range from the more common ocular surface diseases such as inflammation of the cornea, conjunctiva, and sclera, to the relatively rare paracentral acute middle maculopathy and acute macular neuroretinopathy. For patients with ocular symptoms as the first or accompanying symptoms of SARS-CoV-2 infection, how to identify the correlation between ocular manifestations and SARS-CoV-2 infection is undoubtedly a serious challenge for ophthalmologists. In this review, the ocular pathology caused by both SARS-CoV-2 infection and vaccination was discussed, covering pathological changes in the ocular surface, uvea, retina and macula, and cranial nerves.

Median Nerve Cavernous Hemangioma.

Hemangiomas of the median nerve are extremely rare; only 12 cases have been reported in the literature. We discuss a patient who presented with paresthesia and pain along the distribution of the left median nerve secondary to a cavernoma of the proximal part of the nerve as suspected on MRI scan. Total removal of the mass was achieved with immediate relief of the symptoms and no neurologic deficit. We conclude that despite being quite rare, the diagnosis of occult vascular lesions of peripheral nerves such as the median nerve, should be considered, especially when other common pathologies are excluded.

Mid-calf level as a puncture site is not safe enough for thermal ablation of the small saphenous vein.

BACKGROUND: Endovenous thermal ablation of the small saphenous vein carries a risk for sural nerve injury. Ablation above mid-calf level is recommended to avoid it. However, this strategy could not eradicate this complication. We present our results of consecutive 30 small saphenous vein thermal ablations which are performed after ultrasonographic identification of the sural nerve. METHODS: We studied 26 consecutive subjects with a total of 30 limbs. Ablation was performed proximal to the risk point by a 1470-nm diode laser. Patients were asked to attend follow-up outpatient controls at 7 days, 30 days, and 180 days postoperatively. Rate of identification of the sural nerve by ultrasonography, safety of the mid-calf level as a puncture site and postoperative sural nerve damage were assessed. RESULTS: The sural nerve identification was achieved by ultrasonography in all patients except for one. Mid-calf level as a puncture site was not safe in three (10%) extremities. None of the patients showed any evidence suggesting postoperative sural nerve damage. CONCLUSION: Choosing the puncture site according to the risk point may be more reasonable than general mid-calf level which is being used.

[Pituitary syndrome caused by neoplasia in a 17-month-old Holstein Friesian heifer]. / Hirnbasissyndrom infolge eines Tumors bei einer 17 Monate alten Deutsch-Holstein-Färse.

A 17-month-old Holstein Friesian heifer was presented after one day with dysphagia, slight paralysis of the tongue and swelling of the eyelids. Clinical examination of the animal revealed an extended posture of the head and neck, severely increased salivation, reduced lingual tone and mandibular paralysis with complete absence of the swallowing reflex. The right eye showed a drooping eyelid, mucopurulent discharge, exposure keratitis, corneal opacity and miosis. On the left side, a moderate exophthalmos and slight mucous discharge from the nostril were observed. Neurological examination revealed the absence of multiple cranial nerve reflexes suggesting a pituitary syndrome. On X-rays, a soft-tissue opacity with sharp margins and a diameter of approximately 5 cm was seen. It was located ventral to the ethmoid bone with possible intraneurocranial origin. Rhinoscopically, a mass located distal to the ethmoid bone with an uneven, slightly reddish surface partly covered by purulent exudate was visualised. Post-mortem examination of the euthanized animal confirmed neoplasia, which ranged from the fossa hypophysialis of the corpus ossis basisphenoidalis to the ethmoid bone. Histopathologic findings matched a small, round, blue cell tumour.

Safe zone for transacetabular screw fixation using a Kerboull cross-plate: A CT-scan templating prospective study.

BACKGROUND: Implantation of Kerboull acetabular reinforcement cross-plates (Kerboull plate) carries a risk for injury to vascular structures and pelvic organs. To our knowledge, there is no study assessing anatomical assessment related to this risk with this specific design. Therefore, we performed a prospective study to answer the following four questions: 1) What is the minimum distance and angle between the plate and iliac vessels? 2) What is the distance between the plate and the inner cortex of the ilium? 3) What is the ratio of views with muscle tissue present on the inner surface of the ilium? 4) What are the boundaries of the safe zone for transacetabular screw fixation for a Kerboull plate? HYPOTHESIS: A safe zone for fixation screws would be defined by a narrow range of insertion angles. MATERIALS AND METHODS: This is a CT-based 3D templating prospective study. Simulations were performed for 18 patients fitted with a Kerboull plate. An original Kerboull plate (Stryker, Mahwah, NJ, USA) was placed at a 45° abduction angle relative to the X-axis (alignment A) and the palette was placed vertically to the X-axis (alignment B). We measured the distance from the centre of the plate to the inner surface of the cortex of the ilium, the shortest distance to vessels and the angle of existing vessels, and the ratio of muscles on the inner surface of the ilium. RESULTS: The shortest distance to the vascular structures increased with increasing angle of insertion of the fixation screws, 85.8±12.1mm for A and 111.4±12.0mm for B at 45°. The distance to the inner cortex was further increased for screws inserted in posterior direction. At insertion angles ≥40°, the screws passed through muscle before invading the pelvis in most cases. However, at anterior-posterior angle (AP angles) ≤-10°, the risk of direct insertion of screws into the sacroiliac joint increased. DISCUSSION: The safe zone for transacetabular screws would be insertion at an angle≥40°, with an AP angle between 0° and -10° (slight posterior direction). LEVEL OF EVIDENCE: Level IV prospective diagnostic study.