Sigmoid Notch Research Articles

Three Dimensional Morphological Grading of the Ankylosed TMJ for Surgical Planning: A Retrospective Observational Study

Introduction: Temporomandibular Joint (TMJ) ankylosis remains an enigma in craniofacial surgery due to the challenges encountered while restoring mouth opening, facial form and airway to normalcy. Though TMJ ankylosis is a relatively simple diagnosis to make, the specific surgical plan depends on the nature and extent of the fusion of the mandible with the cranial base. Aim: To classify the pattern of bone deformity found in TMJ ankylosis using three Dimensional (3D) Computed Tomography (CT) imaging and its role in determining the type of procedures required for effective gap arthroplasty. Materials and Methods: The 3D CT reconstructed images of 66 consecutive patients having 82 ankylosed joints treated from January 2007 to December 2019 with a standardised protocol was evaluated retrospectively. A grading system was used with the following criteria: coronoid hyperplasia, sigmoid notch to skullbase fusion and loss of residual joint space. The gap arthroplasty required for each grade of ankylosis was also analysed. The complete data in the present study was tabulated in Microsoft excel sheet and frequency (n) analysis was done for all variables. Results: Out of 66 patients (82 ankylotic joints) 37 males and 29 females), age range 2.5 years to 51 years, average age 18.2 years) 27% of the total joints surveyed belonged to grade 1 type of ankylosis. None of these joints had complete bony fusion (absence of the radiolucent zone between the cranium and condyle). A 10% of the joints had moderate ankylosis (grade 2). None of them revealed complete bony fusion (absence of the radiolucent zone) or fusion of the sigmoid with the cranial base. Grade 3 ankylosis was the most widely seen pattern of ankylosis (63% of the present study subjects) and 92% had a history of childhood onset. A 90% of the joints in this group had ipsilateral coronoid hyperplasia. A 48% of the joints with severe ankylosis (grade 3) showed bony fusion with the cranial base, with loss or absence of the radiolucent zone {Fusion Line (FL)} between the cranial base and the condyle. Conclusion: The extent and severity of TMJ ankylosis needs to be ascertained prior to planning TM Joint ankylosis surgery. A 3D CT assessment and subsequent radiologic grading provides a reliable guide for ankylosis release.

Osteometric Measures of Mandible on Its Various Aspects in South Indian Dry Skull

Introduction: Mandible is the single bone articulated with cranium forming a temporomandibular joint and it contributes to the lower jaw containing teeth. The mandible is composed of the body and the ramus.
 Aim: Aim of this study is to find the distance between each parameter in different mandibles.
 Materials and Methods: The present study has utilized 30 south indian dry skulls from the Anatomy Department of Anatomy, Saveetha Dental college. The following parameters are taken to measure by using vernier calipers. They are the maximum distance between the mandibular incisors, mandibular inter canine, mandibular 1st premolar, mandibular molar, mandibular coronoid process, mandibular condylar process, mandibular notch on either side. The results were analysed statistically by using t-test calculator in Graph pad.
 Results: From the study it was observed that the mean distance between the mandibular incisors is 15.658 ± 1.642416 , mandibular inter canine 29.0025 ± 9.04636, mandibular 1st premolar 40.746 ± 2.543341, mandibular molar 62.076 ± 3.4988, mandibular coronoid process 85.8735 ± 5.10615, mandibular condylar process 103.013 ± 3.794, mandibular notch on either side 88.368 ± 3.5832 (Table 1 & Figs. 1-6).
 Conclusion: The present study thus concluded that the morphometric analysis of the mandible is of utmost importance in determining the gender, anatomical studies, clinical and anthropometric studies.

Morphometric Analysis of Dry Human Mandibles of Sri Lankans

<strong>Introduction: </strong>Variety of mandibular morphometric measurements determines the population and sex differences of facial skeleton. This study is aimed to determine the mandibular morphometric measurements of Sri Lankan population. <strong></strong><strong></strong> <strong><br /></strong> <strong>Materials and methods: </strong>Thirteen different mandibular measurements were obtained in 75 dry mandibles of which the gender and age were determined referring to the standard literature. Optimum measures were undertaken to reduce the intra and inter observer bias. The data were analysed using Minitab 19 version. Mean ± SD, mean difference and P- value of each morphometric parameter for both sexes were analysed separately by using Minitab 19 version. <strong><br /></strong> <strong>Results and discussion: </strong>The sample consisted of 40 male and 35 female mandibles, age ranging from 60 – 80 years with the mean age of 67.545 ±4.36765. The mean value of each morphometric parameter in males were higher except in the mandibular angle and the height and breadth of the mandibular body. The maximum mandibular length, bigonial width, maximum ramus height, bicondylar breadth, bicoronoid breadth, bimental breadth and mandibular notch depth of males showed statistical significance (P&lt;0.05). The mean values of all the parameters were different from values of the different populations. <strong></strong><strong></strong> <strong><br /></strong> <strong>Conclusions: </strong>Mandibular morphometric characteristics of Sri Lankans showed distinctiveness within the population and a direct relationship with the sex. These findings provide information for objective assessment facial skeletons of Sri Lankans.

Correlation between the Mandibular Lingula Position and Some Anatomical Landmarks in Cone Beam CT.

Background: the position of the mandibular lingula (Li) affects the success rate of the inferior alveolar nerve block (IANB) and ramus osteotomies. This study evaluated the position of the Li, to investigate the anatomical relationship between the Li and some anatomical measurements using cone beam computed tomography (CBCT). Methods: 201 hemimandibular CBCTs of 111 patients (43 males and 68 females; 18 to 88 years old) were retrospectively evaluated. The Li location was determined from the lingula tip to: the occlusal plane, the anterior and posterior borders of the mandibular ramus, the lower border of the mandible, the distal surface of the mandibular second molar, and the mandibular notch. We evaluated the correlations between the Li and the anteroposterior diameter of the mandibular ramus; the vertical distance between condyle and mandibular angle; the mesial–distal diameter of the first, second, and third mandibular molar, the intercanine distance, the intermolar distances among the first, second, and third mandibular molars; the distance between the intermolar line of the first molar and midline, and the length of the mandibular body. Results: the vertical distance of the Li from the occlusal plane was 11.22 ± 4.27 mm. Some parameters significantly correlated with the anatomical measurements taken into consideration. Conclusions: the present study provides new information concerning the Li and mandibular anatomy in the Italian population. Moreover, by correlating some anatomic measurements to the Li position, the localization of the Li is made possible, indirectly through the measurement of some distances between anatomical landmarks.

Topographical Landmarks for the Identification of Branches of Mandibular Nerve and Its Surgical Implications: A Cadaveric Study.

IntroductionBasic knowledge of anatomy is crucial in providing predictable, safe, and efficacious mandibular anesthesia as the mandibular nerve is vulnerable to injury during dental procedures and other surgical manoeuvers. The lack of availability of the appropriate topographical bony landmarks for the location of the branches of this nerve often accounts for iatrogenic injuries and the failure to obtain adequate local anesthaesia. Hence we aimed to describe the topographical landmarks of the branches of the mandibular nerve and their variations in the infratemporal fossa.MethodologyIn 16 formalin-fixed cadavers, irrespective of the sex of the cadavers, bilateral dissection of the infratemporal fossa was done after identifying the necessary bony landmarks. The mandibular nerve and its branches were traced out and the required measurements were taken using the digital vernier caliper. The results were statistically analysed for mean, range, and standard deviation.ResultsThe masseteric nerve is 15.87+/-1.64 mm superior to the lowest point on the mandibular notch. The lingual nerve in the third molar area is at the depth of 24.75+/-2.38 mm from the angle of the mandible (gonion), making an angle of 50° with the base of the mandible. 20.13+/-3.1 mm inferior to the mandibular notch is the precise location of the mandibular foramen which allows access to the inferior alveolar nerve. The incidence of accessory mandibular foramen in the dissected samples is 9.37%.ConclusionThe topography of the masseteric nerve, lingual nerve, and inferior alveolar nerve was studied using constant and reliable bony landmarks in the cadaver which might aid effective dental and facio-maxillary surgical procedures. However, the outcome of this study could not be applied to paediatric patients as the subjects were restricted to adult cadavers.

Computed tomography analysis of the relationship between the coronoid and the radial head.

The coronoid process is an important stabilizer of the elbow, and its anatomy has been extensively studied. However, data documenting the relationship of the coronoid relative to the radial head (RH) are limited. The latter is a good landmark for the surgeon when débriding or reconstructing the coronoid. This imaging-based study quantified the anatomic relationship between the coronoid and the proximal radius and ulna. We investigated 80 cadaveric upper extremities (18 paired elbows) by 3-dimensional digital analysis of computed tomography data. After construction of a standardized coordinate system, the relationships between the coronoid, the anterior-most point of the RH, the deepest point of the articular surface of the RH, the top of the lesser sigmoid notch, and the deepest point of the guiding ridge of the trochlear notch were analyzed. The mean height of the tip of the coronoid was 36 ± 4 mm (range, 26-43 mm). The mean height of the anterior-most point of the RH was 40 ± 4 mm (range, 28-47 mm). The mean distance between the tip of the coronoid and the anterior-most point of the RH was 4.5 ± 1 mm (range, 2-10 mm). For paired elbows, the heights of the tip of the coronoid and the anterior-most point of the RH were similar between sides. This study described the relationship between the coronoid and RH. This information should prove useful when reconstructing a coronoid from a medial approach in the case of an intact RH. The difference in radiographic height between the tip of the coronoid and anterior RH in the normal elbow averages 5 mm. However, when we account for the normal cartilage thickness of the RH and coronoid, a 3- to 6-mm difference in height would be seen at surgery depending on whether the cartilage of the coronoid process is intact or removed. The distance between the tip of the coronoid and the anterior-most point of the RH is similar to the size of shavers used when débriding osteophytes during arthroscopy.

Modified Gap Arthroplasty for Temporomandibular Joint Ankylosis Following Radiotherapy for Rhabdomyosarcoma: Report of an Unusual Case and Brief Literature Review.

Radiotherapy at the temporomandibular joint (TMJ) area often results in trismus, however, post radiation ankylosis is extremely rare and has not been previously reported in literature. Radiation is known to impact the vasculature of bony structures leading to bone necrosis with certain risk factors including surgical intervention, even teeth extraction, that could lead to osteoradionecrosis. Accordingly, gap arthroplasty for such case seemed rather challenging. In this report, we introduce for the first time, a rare case of temporomandibular joint ankylosis post radiotherapy for management of rhabdomyosarcoma in a 12 years-old boy. A modified gap arthroplasty technique combined simultaneously with pterygo-masseteric muscle flap was applied to lower the risk of osteoradionecrosis due surgical trauma at irradiated area. Computed tomographic scan on the head indicated that the TMJ architecture was completely replaced by bone, with fusion of the condyle, sigmoid notch, and coronoid process to the zygomatic arch and glenoid fossa. The patient’s problem was totally solved with no osteoradionecrosis or relapse of ankylosis observed at follow up visits. Herein, the modified gap arthroplasty combined with pterygo-masseteric muscle flap could be recommended to be applied on other cases of ankylosis especially after receiving radiotherapy.

Endonasal Free Flap Reconstruction Combined With Draf Frontal Sinusotomy for Complex Cerebrospinal Fluid Leak: A Technical Report &amp; Case Series

Frontal sinus cranialization with closure via bifrontal pericranial flaps is the gold standard for separating the nasofrontal recess from the intracranial cavity for posterior table defects. Despite the high success rate, cerebrospinal fluid (CSF) leak may persist and is particularly challenging when vascularized reconstructive options from the bicoronal incision are exhausted. To assess a novel endonasal technique using an adipofascial radial forearm free flap delivered to the frontal recess through a Draf sinusotomy to repair complex CSF leaks from the frontal sinus. A retrospective review of 3 patients (all male; ages 42, 43, and 69 yr) with persistent CSF leak despite frontal sinus cranialization and repair with bifrontal pericranium was performed. Etiology of injury was traumatic in 2 patients and iatrogenic in 1 patient after anaplastic meningioma treatment. To create space for the flap and repair the nasofrontal ducts, endoscopic Draf III (Case 1, 3) or Draf IIb left frontal sinusotomy (Case 2) was performed. The forearm flap was harvested, passed through a Caldwell-Luc exposure, and placed within the Draf frontal sinustomy. The flap vessels were tunneled to the left neck and anastomosed to the facial vessels by the mandibular notch. Intraoperatively, the flaps were well-seated and provided a watertight seal. Postoperative hospital courses were uncomplicated. There were no new CSF leaks or flap necrosis at 12, 14, and 16 mo. Endoscopic endonasal free flap reconstruction through a Draf procedure is a novel viable option for persistent CSF leak after failed frontal sinus cranialization.

Accuracy of Cone Beam CT Measurements for Assessment of Posterior Mandible: A Cadaver Study

Objectives: This study is aimed at analysing the accuracy and reliability of the cone beam CT (CBCT) measurements and direct physical measurements of the posterior mandible. Materials and methods: Eighteen cadaveric hemi-mandibles were dissected from the soft tissues and the CBCT images of the mandibles were taken. Direct physical and cone beam CT measurements of six landmarks which includes height of ramus (R), distance of lingula to sigmoid notch (LS), distance of lingula to inferior border (LI), position of lingula in relation to occlusal plane (L-OP), ramus thickness at crestal level (RT-C), and ramus thickness at midway between sigmoid notch and lingula (RT-M) were determined. Accuracy and reliability of the measurements were tested. Results: Four landmarks showed high accuracy when measuring the posterior mandible, while two landmarks, LI and RT-M, showed statistically significant weaker accuracy (p&lt;0.05). Inter-reliability were good for all landmarks when measured directly physically on mandibles (ICC&gt;0.7 and p&gt;0.05), but were low on two landmarks, LI and RT-C, on CBCT measurement (ICC&lt;0.5 and p&lt;0.05). Conclusion: A generally strong accuracy between direct physical and CBCT measurements for most landmarks on posterior mandible were found. Reliability between two researchers were high on direct physical measurements. Meanwhile, two landmarks on CBCT which include LI and RT-C showed low inter-reliability. Hence, CBCT measurements proved to be a good tool for pre-operative assessment, since high inter-reliability and strong accuracy corresponding to direct physical were recorded.

Posterior auricular artery helix root free flap—part II: clinical application

The surgical repair of full-thickness defects involving the alae nasi is complex. Pedicle flaps such as frontal and nasolabial flaps can be used, but require several interventions with different techniques. In contrast, free flaps from the foot of the ear helix allow the three layers of the nasal wings to be reconstructed in a single operation. Nevertheless, in the classical approach, the vascular pedicle is short. Although some authors have proposed raising the flap in a retrograde manner, this still yields a relatively short pedicle with narrow vessels. In the companion paper, we demonstrated that a posterior auricular artery helix root free flap (PAAHF) can be harvested from the posterior auricular vessels, thus increasing the useful pedicle length. The case of a patient with basal cell carcinoma of the left ala is presented here. A right helix root free flap was anastomosed with the facial vessels at the left mandibular notch. This new flap overcomes the main limitation of the classical helix root flap, namely the length of the pedicle. It has all of the morphological qualities of the classical flap, but with simpler vascular assembly, since autologous venous grafts and complex anastomoses are not required.

Clinical, radiological and patient-rated outcome comparison between total and partial ulnar head implants.

This study aimed to analyse the clinical and radiological outcomes after ulnar head replacement and to compare partial and total ulnar head implants. Twenty-two patients with 23 implants were available with a mean follow-up time of 7years (range 1.3 to 17) after distal radioulnar joint arthroplasty. At the final follow-up, patients had a low level of pain at rest and during effort, a median Disabilities of the Arm, Shoulder, and Hand (DASH) score of 12 and Patient-Rated Wrist Evaluation score of 12 with partial ulnar head implants, and scores of 20 and 22 in total ulnar head implants, respectively. While the range of motion in patients with partial ulnar head implants was slightly reduced in comparison with the preoperative condition and to the patients with total ulnar head implants, there was a tendency to a higher grip strength and rotational torque. Both types of prosthesis showed sigmoid notch resorptions and resorptions around the neck. We conclude that the results after partial ulnar head replacement do not significantly differ from the total ulnar head implants in many aspects.Level of evidence: III.

Trends in Ancient Populations’ Osteobiography during the Holocene: the Levantine Perspective

Abstract. The rapid changes in our surroundings during the Holocene challenge the human body. The current study, carried out on the terminal Pleistocene-Holocene populations of the Levant, presents several examples of how changes in the habitation and diet have affected the disease patterns and the gross morphology of long bones and mandibles. Our major findings were that the prehistoric Natufian (67%) and the protohistoric Chalcolithic (80%) populations exhibited a much higher rate of ear inflammation (otitis media) than all other populations: Neolithic, Roman/Byzantine, and Ottoman (50% ± 5%). A general continuous significant decrease in the relative femoral bone cortical area from the Natufian (77.8%) to present times (64.7%) was noticed (the Chalcolithic population was the exception). Mandibular shape has changed considerably, mainly between the pre-agricultural population (the Natufian) and the succeeding ones (i.e., the ramus became taller and narrower, the coronoid higher and pointed, the mandibular notch narrower and deeper, and the body more triangular). Possible behavioral, economic, and environmental factors associated with these changes are discussed.

Morphologic Characteristics of the Sigmoid Notch of the Distal Radius for Patients With Peripheral Triangular Fibrocartilage Complex Tear.

The distal radioulnar joint (DRUJ) is stabilized by the bony anatomy of the contact surfaces. The authors analyzed the morphologic characteristics and radiologic parameters at the sigmoid notch of patients with a peripheral triangular fibrocartilage complex (TFCC) tear compared with asymptomatic patients. Preoperative axial computed tomography scans were reviewed for 76 wrists with peripheral TFCC injuries, including foveal avulsion, and 76 wrists of age- and sex-matched control subjects. The authors used axial computed tomography scans of the DRUJ to classify the patients into 4 groups according to the type of sigmoid notch, namely, flat face, ski-slope, C-type, and S-type. They also measured the tilting angle, depth, width of the sigmoid notch, and radioulnar ratio (RUR). Statistical analyses were performed with the chi-square test or paired t test (P<.05). The mean proportions of flat face, ski-slope, C-type, and S-type sigmoid notches among patients with peripheral TFCC injuries were 42%, 22%, 29%, and 7%, respectively, whereas those for the control group were 33%, 1%, 65%, and 1%, respectively (P<.05). The tilting angle was lower (TFCC injury, 84.5°; control, 86.2°; P<.05) and the RUR was significantly higher (TFCC injury, 0.67; control, 0.56) in the TFCC group, particularly for men (P<.05). Depth (TFCC injury, 1.0 mm; control, 1.3 mm; P>.05) and width (TFCC injury, 14.8 mm; control, 14.5 mm; P>.05) were similar between the groups. Patients with ski-slope or dorsally tilted sigmoid notches may be at greater risk for peripheral TFCC injuries. [Orthopedics. 2021;44(6):e729-e734.].

Evaluation of the position of lingula mandible, mental foramen and lingual foramen of individuals in the 7-17 age groups via Cone-Beam Computed Tomography

Objective: The identification of landmarks in mandible is an important stage before dental procedures ın pediatric patients. The purpose of this study was to determine the location of lingula mandible, mental foramen (MF) and lingual foramen (LF) in a paediatric population. &#x0D; Methods: The distance of lingula mandible to the anterior, posterior, superior, and inferior borders of mandible and to distal edge of the alveolar socket of the 1st molar tooth were measured. MF and LF distance to the top of the alveolar crest and the inferior edge of the basis mandibulae were determined. The horizontal location of MF was evaluated. &#x0D; Results: The distance between lingula mandible and the sigmoid notch, the inferior border of the ramus, the anterior border of the ramus and the posterior border of the ramus was 18.63±4.52 mm, 24.81 ± 5.19 mm 14.67±2.39 mm, and 15.14 ± 3.06 mm respectively. The MF was mostly located between long axes of first and second premolar teeth. LF is closer to the inferior edge of the basis mandibulae. &#x0D; Conclusion: It is necessary to determine anatomical landmarks in children prior to the surgical operations to prevent the possible neurovascular complications.

Stress distribution pattern in the distal radioulnar joint before and after ulnar shortening osteotomy in patients with ulnar impaction syndrome

Ulnar shortening osteotomy (USO) for ulnar impaction syndrome potentially leads to degenerative changes of the distal radioulnar joint (DRUJ). This study was performed to evaluate the effect of the sigmoid notch morphology on the stress distribution pattern of the DRUJ using computed tomography (CT) osteoabsorptiometry (CT-OAM). We reviewed the pre- and postoperative transverse CT images of 15 wrists that had undergone USO. The examined wrists were classified into two groups based on the sigmoid notch morphology: the linear-type notch (type L) and the curved-type notch (type C). We calculated and statistically compared the percentage of the high-density area (%HDA) in each divided region of the sigmoid notch. In type L, %HDA was significantly larger in the distal-dorsal region of the sigmoid notch before USO. Postoperatively, in type L, no specific regions showed a significantly different %HDA. In type C, %HDA was significantly larger in the distal-volar region of the sigmoid notch before USO. Postoperatively, %HDA of type C was significantly larger in the proximal-volar region. Our results suggest that in patients with ulnar impaction syndrome, morphological evaluation of the sigmoid notch can serve as a predictor of osteoarthritis in the DRUJ with or without USO.

The radiological findings in complex elbow fracture-dislocation injuries.

Elbow fracture-dislocation is a complex injury which can lead to significant bony and soft tissue damage. Surgical intervention is guided towards restoring joint stability, allowing early mobilization and preventing long-term joint stiffness. The most common types are posterolateral, posteromedial, Monteggia type (and variants), and anterior trans-olecranon fracture-dislocations. Posterolateral fracture-dislocation is characterized by a radial head fracture (± anterolateral coronoid fracture) and typically capsuloligamentous disruption (lateral collateral ligaments injury is the most common). A posterolateral fracture-dislocation with radial head and coronoid anterolateral facet fractures is termed a terrible triad injury. In posteromedial fracture-dislocation, there is a fracture of the anteromedial facet of the coronoid, typically with proximal avulsion of the lateral collateral ligaments (± injury to the posterior bundle of the ulnar collateral ligament). Monteggia fracture-dislocation injuries demonstrate proximal ulnar fracture (with possible involvement of the olecranon and the coronoid) and radial head dislocation. These can be divided into apex anterior or apex posterior variants. The latter are commonly associated with radial head fractures and lateral ligamentous injury, and have a worse prognosis. In trans-olecranon fracture-dislocation, there is significant disruption of the greater sigmoid notch and the olecranon, with various involvement of the coronoid and the proximal ulna. The article describes the radiological findings and outlines the management principles in complex elbow fracture-dislocation injuries.

Radiographic changes in the distal ulna in non-rheumatoid patients with extensor digitorum communis ruptures.

Osteoarthritis of the distal radioulnar joint (DRUJ) is relatively common in elderly people. Extensor digitorum communis (EDC) ruptures occasionally and occurs with or without prior signs in these people. The purpose of this study was to clarify the radiographic changes in the distal ulna associated with EDC rupture. We analyzed plain radiographs of 71 patients with non-rheumatoid arthritis and 40 controls. Radiographic changes in the distal ulna were categorized into normal, osteoarthritic-change (OA-change), and taper. We measured the ulnar variance (UV) and ulnar bowing angle in the posteroanterior radiographs and the dorsal bowing angle (DBA) and dorsal protrusion (DP) in the lateral radiographs. The shape of the sigmoid notch (SN) was categorized into flat, radial inclination, and dimple. The primary outcome was a comparison of radiographic parameters between the patient and the control groups. The secondary outcome was an analysis of the type of SN to investigate factors affecting ulnar deformation. The ratio of the radiographic change in the ulna, UV, DBA, and DP was significantly larger in the patient group than in the control group. Patients with the radial inclination type of SN showed a greater UV than those with the dimple type. Deformation of the distal ulna, a large UV, dorsal penetration, and dorsal bowing was related to EDC rupture. Regarding the large UV, the lunate shaved the upper half of the distal ulna, whereas the DRUJ shaved the lower half. These processes formed a tapered ulna head. A large UV and an inclination of the DRUJ played a role in ulnar head deformation.

Distal Radioulnar Joint, Distal Ulna Injury, and Lunate Facet Considerations in Distal Radius Fractures.

Injuries to the distal aspect of the ulna and the distal radioulnar joint (DRUJ) commonly occur concurrently with distal radius fractures. These fractures may also involve the sigmoid notch of the lunate facet of the radius. Each of these structures merits consideration when managing ulnar-sided injuries associated with distal radius fractures. Improper management of distal radioulnar complex injuries may result in limited wrist motion, persistent DRUJ instability, and pain despite successful fracture union. The distal ulna is the keystone of the distal radioulnar articulation. An understanding of the components of the distal radioulnar complex and methods to manage injuries of each of these components contributes to improved functional outcomes by restoring this keystone effect. The classification of distal radioulnar injuries discussed herein provides a framework for understanding the disruption of the ligamentous stabilizers of the DRUJ and identifying residual distal radioulnar instability after fracture fixation. Proper treatment of residual DRUJ instability will restore stability and minimize persistent functional impairment.

A preliminary review of Nephelomys albigularis (Tomes, 1860) (Rodentia: Cricetidae), with the description of a new species from the Peruvian montane forests.

Nephelomys albigularis is a sigmodontine rodent of the tribe Oryzomyini distributed in the Andean forests from central Ecuador to central Peru. Although several studies recognize this species as monotypic, significant morphological variation has been reported in Peruvian populations that were not properly assessed by direct comparisons with the type series from central Ecuador. We present a preliminary review of N. albigularis with an integrative approach and emphasis on Peruvian populations. We analyzed specimens using morphological and morphometric methods, complemented with phylogenetic analyses and species delimitation using sequence data from the cytochrome-b gene. Our results reveal that N. albigularis (sensu lato) comprises two taxa: N. albigularis s.s., from the montane forests in central and southern Ecuador and northwestern Peru, and Nephelomys sp. nov. from montane forest east of the Maran River. These taxa are morphologically distinct and are separated by a genetic distance of 5.90 1.01%. Nephelomys sp. nov. differs from N. albigularis s.s. by longer rump hairs, narrow hypothenar pads, faintly bicolor tail; absent interorbital ridges, low zygomatic plates, smoothly squared posterior margin of the hard palate or with a small median postpalatal process, smoothly edged ventral margin of the external auditory meatus, and slightly angular mandibular sigmoid notches. In this work, we present a diagnosis and description of the new species of Nephelomys and discuss the role of the Maran River as a potential driver for speciation in the genus Nephelomys.

MORPHOLOGIC VARIATIONS OF THE INFERIOR ALVEOLAR NERVE CANAL THROUGH THREE-DIMENSIONAL COMPUTED TOMOGRAPHY

<h3>BACKGROUND</h3> The Inferior alveolar nerve is the main nerve supply to the mandible, and its location and position related to the surrounding structures are critical during surgical procedures. The introduction of cone beam computed tomography (CBCT) with low radiation dose and high resolution has improved the anatomic visualization of the canal. <h3>OBJECTIVE(S)</h3> The aim of this study was to investigate the morphologic variations of the inferior alveolar canal in 10 CBCT data sets through 3D computed tomography assessment. <h3>STUDY DESIGN</h3> Ten CBCT scans were randomly selected from the archived cases database of the Oral and Maxillofacial Radiology Department at The University of Iowa. Institutional review board approval was obtained. The inclusion criteria consisted of visualization of the complete inferior alveolar canal and the third molar bilaterally, no pathosis associated with the mandible, and no motion or metallic artifacts that might affect the image quality. The distance between 10 fixed anatomic landmarks (lingula, sigmoid notch, angle of mandible, mental foramen, buccal cortex of the mandible, symphysis, mandibular foramen, posterior surface of the most distal molar, condyle, and inferior border of the mandible) were measured and the length and angulation of the inferior alveolar canal were measured. All measurements were performed by an OMR twice with at least 1 week between measurements. <h3>RESULTS</h3> There were variations in the inferior alveolar canal length and angulation between the right and left sides of the mandible. The right mental foramen was located slightly posteriorly from the symphysis compared with the left side. The mandibular canal was around 30 mm away from the distal aspect of the presented molars on the both sides. <h3>DISCUSSION/CONCLUSIONS</h3> Three-dimensional imaging obtained from CBCT scans provides comprehensive knowledge of the anatomic location and the course of the canal within the mandible.