The mylohyoid line is highly variable but does not affect the microarchitecture of the edentulous alveolar bone - an anatomical micro-CT study.

OBJECTIVES: To evaluate in the absence of teeth the variability of the mylohyoid line (ML), the microarchitecture of the adjacent bone, and whether the variable prominence/width of the ML is associated with the quality of the adjacent bone. METHODS: µCT scans of 28 human mandibles from anatomical specimens were analyzed. The following parameters were assessed in four edentulous areas (first and second premolar (PM), first, second, and third molar (M1/2/3)): ML width, cortical thickness (CtTh), average cortical- (Avg.Ct.BV/TV), and trabecular bone volume fraction (Avg.Tb.BV/TV). RESULTS: The ML width increased from the PM towards the M2 region, which also showed the highest variance (range: 0.4-10.2 mm). The CtTh showed a decrease in the M3 region, while Avg.Ct.BV/TV and Avg.Tb.BV/TV hardly differed among the regions. In the multivariable model on the effect of the various parameters on the ML width, only gender and tooth region were significant. Specifically, male specimens were associated with a wider ML width compared to female specimens and the M2 region was associated with a wider ML width compared to the other tooth regions. CONCLUSION: The ML width was not associated with the cortical and trabecular bone quality in the adjacent bone, while gender and tooth region had a significant effect. Specifically, the ML width was lower in female, but peaked in the M2 region with a median width of 3-4 mm. CLINICAL RELEVANCE: From a clinical point of view, it was confirmed that the ML is in general a highly variable structure, especially in the M2 region, but the ML width does not allow any conclusions on the bone quality. Altogether, this underlines the need for an individual and accurate diagnostic prior to any surgical intervention.

Effect of hot water maceration, rehydration, and soft tissue presence on 3D geometry of bone.

PURPOSE: In forensic medicine, maceration is often essential for examining bone surfaces, serving purposes such as identifying cut marks, making geometric measurements, and determining the victim's age. While hot water maceration removes soft tissue effectively, it is known to cause bone surface shrinkage. This raises the question of whether this effect is permanent or if it can be partially reversed through rehydration, considering the presence of soft tissue. METHODS: Computed tomography (CT) scans were conducted on the radii of 20 paired human anatomic forearm specimens. Subsequently, the radii were extracted, macerated in 60 °C water, CT-scanned in an air environment, rehydrated, re-implanted into the forearms, and CT-scanned again. RESULTS: Maceration resulted in a mean shrinkage of 0.12 mm on the outer bone surface. This shrinkage was nearly fully recoverable for the diaphysis after rehydration and accounting for soft tissue surrounding the bone. In contrast, the epiphysis showed permanent shrinkage, likely due to the loss of small bone fragments. Analysis of the inner bone surface indicated a smaller effect, but with significant standard deviations, especially for the epiphysis, possibly related to the less well-defined nature of the inner bone surface. CONCLUSION: The epiphyseal surface of hot water-macerated bone will, on average, be approximately 0.15 mm deflated and cannot retain the original surface. On the other hand, the diaphyseal surface is less affected and can be nearly completely restored after rehydration and accounting for soft tissue surrounding the bone.

Microsurgical transcranial approaches to the posterior surface of petrosal portion of the temporal bone: quantitative analysis of surgical volumes and exposed areas.

Different microsurgical transcranial approaches (MTAs) have been described to expose the posterior surface of the petrous bone (PPB). A quantitative, anatomical comparison of the most used MTAs, for specific areas of the PPB, is not available. Anatomical dissections were performed on five formalin-fixed, latex-injected cadaver heads (10 sides). Six MTAs were analyzed: Kawase approach (KWA), retrosigmoid approach (RSA), retrosigmoid approach with suprameatal extension (RSAS), retrolabyrinthine approach (RLA), translabyrinthine approach (TLA), and transcochlear approach (TCA). Surgical volumes and exposed areas of each approach were quantified with a dedicated neuronavigation system (ApproachViewer, part of GTx-Eyes II, University Health Network, Toronto, Canada) and adjuvant software (ITK-SNAP and Autodesk Meshmixer 3.5). Areas and volumes were compared using linear mixed models. TCA provided the best exposure of Trautmann's triangle and the retromeatal, suprameatal, meatal, and premeatal regions. RSAs provided the best exposure of the inframeatal region, with RSAS gaining significant exposure of the suprameatal region. KWA had the highest surgical volume, and RLA the lowest. Transpetrosal approaches offer the widest exposure of PPB proportionally to their invasiveness. Retrosigmoid approaches, which get to the studied region through a postero-lateral path, are paramount for the exposure of the inframeatal and suprameatal region and, given the adequate exposure of the remaining PPB, represent an effective approach for the cerebellopontine angle (CPA). These anatomical findings must be considered with approach-related morbidity and the pathological features in order to choose the most appropriate approach in clinical practice.

Visualization of the Third Ventricle, the Future Cavum Septi Pellucidi, and the Cavum Veli Interpositi at 11+3 to 13+6 Gestational Weeks on 3D Transvaginal Ultrasound Including Normative Data.

OBJECTIVES: To show the development of the third ventricle, commissural plate, future cavum septi pellucidi, and cavum veli interpositi in weeks 12-14 by transvaginal 3D ultrasound. METHODS: This is a prospective transvaginal 3D study carried out to define the third ventricle and the diencephalic midline structures surrounding it. 93 of 387 fetuses in which the commissural plate with the future cavum septi pellucidi, cavum veli interpositi, and the roof of the third ventricle could be well visualized, were selected with the choroid plexus of the third ventricle and the pituitary gland serving as leading structures. In a small number of fetuses, the optic chiasm could also be displayed. In addition, the following measurements were performed: third ventricle craniocaudal and anteroposterior, roof of the third ventricle/cavum veli interpositi, and fcsp. RESULTS: The sonomorphologic characteristics of the commissural plate, the future cavum septi pellucidi, and the cavum veli interpositi are described IN 9% OF THE FETUSES examined. Measurements of the third ventricle, cavum veli interpositi, and the roof of the third ventricle show the following results: 3rd V cc = 3.895 + 0.091*CRL mm; 3rd V ap = 4.175 + 0.036*CRL mm; CVI ap = 2.223 + 0.029*CRL mm; CVI cc = 0.139 + 0.02*CRL mm. CONCLUSION: Transvaginal neurosonography enables visualization and measurement of the normal fetal third ventricle at 12-14 weeks of gestation including visualization of the future cavum septi pellucidi and the cavum veli interpositi. BEFORE USE IN PATIENTS CAN BE CONSIDERED, FURTHER SCIENTIFIC WORK IS REQUIRED.

Sensory Innervation of the Upper Eyelid and Its Implication for Upper Eyelid Surgery.

PURPOSE: Sensory alterations of the upper eyelid skin and eyelashes are frequently encountered after upper eyelid surgery. The objective of this study was to provide information on the exact course and distribution of sensory nerve fibers through the anatomic planes in the upper eyelid. METHODS: Ten formalin-fixed hemifaces were dissected. The nerve branches of the ophthalmic nerve in the upper eyelid were traced in an anterograde fashion. RESULTS: A total of 151 nerve fibers were recorded during dissection. The infratrochlear, supratrochlear, supraorbital, and lacrimal nerve contributed each to both the upper eyelid skin innervation and the upper eyelid rim plexus in different distribution patterns. The mean distance from the eyelid margin at which nerve fibers pierced from preseptal into the orbicularis muscle was 14 ± 1.1 mm for nerve fibers targeting the eyelid dermis and 3.7 ± 1.2 mm for nerve fibers targeting the eyelid rim plexus ( p < 0.001). The mean intraorbicular course of nerve fibers was 3 mm (0-17; standard deviation 4.1). The mean distance from the eyelid margin at which nerve fibers pierced from the orbicularis muscle into the preorbicular plane was 10 ± 1 mm for nerve fibers innervating the eyelid dermis and 1.3 ± 0.8 mm for nerve fibers innervating the eyelid rim plexus ( p < 0.001). The mean distance of the preorbicular course of nerve fibers was 2 mm (0-15; standard deviation 3.6). CONCLUSIONS: Based on the findings, a certain degree of postoperative eyelid skin numbness is inevitable while eyelash innervation may be spared in upper blepharoplasty.

Autologous replacement of the head of the radius-proximal fibula versus second metatarsal base: an anatomic feasibility study.

INTRODUCTION: This study investigated the anatomic feasibility of a new surgical therapy option for radial head arthrosis using an autologous vascularized bone graft of the second metatarsal and proximal fibula to recreate the proximal radiohumeral joint. MATERIALS AND METHODS: Upper and lower extremities of eleven body donors were evaluated using CT prior to anatomic dissection. Several distinct anatomic parameters were measured on the ipsi- and contralateral radial and fibular head and the second metatarsal base: bone diameter, articular surface diameter, head height, metaphyseal (neck) diameter, articular surface radius, total articular surface area, and angulation of the articular surfaces (facet). Each dissection phase was photographed in a standardized fashion and all measurements were repeated by direct caliper-measurements. RESULTS: When comparing the proximal radius and fibula to search for anatomic similarities, similar values were found in the maximum articular surface diameter and minimum and maximum measures of the neck diameter. Comparing the proximal radius and the second metatarsal, statistically similar values were found in the maximum neck diameter performing direct measurements and CT evaluation, the maximum head diameter in CT evaluation and the articular facet angulation. CONCLUSIONS: Neither the proximal fibula nor the base of the second metatarsal are ideal bone grafts for replacement of the head of the radius. The base of the second metatarsal might be a bit more suitable as a potential donor since the angulation of the proximal articular facet is similar to that of the radius. LEVEL OF EVIDENCE: Level IV, anatomic study.

Patient-Specific Guides for Accurate and Precise Positioning of Osseointegrated Implants in Transfemoral Amputations: A Proof-of-Concept In Vitro Study.

Background and Objectives: The treatment of transfemoral amputees using osseointegrated implants for prosthetic anchorage requires accurate implant positioning when using threaded bone-anchoring implants due to the curvature of the femur and the risk of cortical penetration in misaligned implants. This study investigated the accuracy and precision in implant positioning using additively manufactured case-specific positioning guides. Materials and Methods: The geometry and density distribution of twenty anatomic specimens of human femora were assessed in quantitative computed tomography (QCT) scanning. The imaging series were used to create digital 3D specimen models, preoperatively plan the optimal implant position and manufacture specimen-specific positioning guides. Following the surgical bone preparation and insertion of the fixture (threaded bone-anchoring element) (OPRA; Integrum AB, Mölndal, Sweden), a second QCT imaging series and 3D model design were conducted to assess the operatively achieved implant position. The 3D models were registered and the deviations of the intraoperatively achieved implant position from the preoperatively planned implant position were analyzed as follows. The achieved, compared to the planned implant position, was presented as resulting mean hip abduction or adduction (A/A) and extension or flexion (E/F) and mean implant axis offset in medial or lateral (M/L) and anterior or posterior (A/P) direction measured at the most distal implant axis point. Results: The achieved implant position deviated from the preoperative plan by 0.33 ± 0.33° (A/A) and 0.68 ± 0.66° (E/F) and 0.62 ± 0.55 mm (M/L) and 0.68 ± 0.56 mm (A/P), respectively. Conclusions: Using case-specific guides, it was feasible to achieve not only accurate but also precise positioning of the implants compared to the preoperative plan. Thus, their design and application in the clinical routine should be considered, especially in absence of viable alternatives.

Transverse Relaxation Anisotropy of the Achilles and Patellar Tendon Studied by MR Microscopy.

BACKGROUND: T2 * anisotropy affects the clinical assessment of tendons (magic-angle artifact) and may be a source of T2 *-misinterpretation. PURPOSE: To analyze T2 *-anisotropy and T2 *-decay of Achilles and patellar tendons in vitro at microscopic resolution using a variable-echo-time (vTE) sequence. STUDY TYPE: Prospective. SPECIMEN: Four human Achilles and four patellar tendons. FIELD STRENGTH/SEQUENCE: A 7 T MR-microscopy; 3D-vTE spoiled-gradient-echo-sequence (T2 *-mapping). ASSESSMENT: All tendons were measured at 0° and 55° relative to B0 . Additional angles were measured for one Achilles and one patellar tendon for a total of 11 angles ranging from 0° to 90°. T2 *-decay was analyzed with mono- and bi-exponential signal fitting. Mono-exponential T2 *-values (T2 *m ), short and long T2 *-components (T2 *s , T2 *l ), and the fraction of the short component Fs of the bi-exponential T2 *-fit were calculated. T2 *-decay characteristics were compared with morphological MRI and histologic findings based on a region-of-interest analysis. STATISTICAL TESTS: Akaike information criterion (AICC ), F-test, and paired t-test. A P value smaller than the α-level of 0.05 was considered statistically significant. RESULTS: T2 *m -values between fiber-to-field angles of 0° and 55° were increased on average from T2 *m (0°) = 1.92 msec to T2 *m (55°) = 29.86 msec (15.5-fold) in the Achilles and T2 *m (0°) = 1.46 msec to T2 *m (55°) = 23.33 msec (16.0-fold) in the patellar tendons. The changes in T2 *m -values were statistically significant. For the whole tendon, according to F-test and AICC , a bi-exponential model was preferred for angles close to 0°, while the mono-exponential model tended to be preferred at angles close to 55°. CONCLUSION: MR-microscopy provides a deeper insight into the relationship between T2 *-decay (mono- vs. bi-exponential model) and tendon heterogeneity. Changes in fiber-to-field angle result in significant changes in T2 *-values. Thus, we conclude that awareness of T2 *-anisotropy should be noted in quantitative T2 *-mapping of tendons to avoid T2 *-misinterpretation such as a false positive detection of degeneration due to large fiber-to-field angles. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

The intercondylar fossa-A narrative review.

The intercondylar fossa ("intercondylar notch," IN) is a groove at the distal end of the femur, housing important stabilizing structures: cruciate ligaments and meniscofemoral ligaments. As the risk for injury to these structures correlates with changes to the IN, exact knowledge of its morphology, possible physiological and pathological changes and different approaches for evaluating it are important. The divergent ways of assessing the IN and the corresponding measurement methods have led to various descriptions of its possible shapes. Ridges at the medial and lateral wall are considered clinically important because they can help with orientation during arthroscopy, whereas ridges at the osteochondral border could affect the risk of ligament injury. Changes related to aging and sex differences have been documented, further emphasizing the importance of individual assessment of the knee joint. Overall, it is of the utmost importance to remember the interactions between the osseous housing and the structures within.

Delamination in rotator cuff tears: Explanation of etiology through anatomical dissection.

The prognostic significance of delaminated rotator cuff tears remains controversial. However, as the surgical goal is to maximize the contact area between layers, the macroscopic appearance of partial delaminated rotator cuff tears is essential. The aim of this anatomical study was to investigate the morphology of delaminated rotator cuff tears. We hypothesized that delamination zones at the intersection of the supraspinatus and infraspinatus tendon fibers are the origin of articular-side degenerative rotator cuff tears. Forty anatomical specimens were evaluated in this study. The supraspinatus and infraspinatus muscles were dissected, the origins were meticulously worked out and followed to their insertions at the humeral head. Fiber exchanges, overlays and delamination zones between the supraspinatus and infraspinatus muscles were photographically documented and measured. Delamination of rotator cuff tears can be classified into articular-side and bursal-side tears. The articular-layer consists of capsuloligamentous tissue, which included the rotator-cable/rotator-crescent complex, the joint capsule and a small part of the supraspinatus tendon. The bursal-side layer represents the tendinous tissue, which consists of the parallel, tendinous parts of the supraspinatus and infraspinatus muscles. Delamination of rotator cuff tears can be classified into articular-side and bursal-side tears. Present model of degenerative tears might explain the high prevalence of articular-side tears, which expand into the rotator-cable/rotator-crescent complex. It may be important for surgeons to incorporate these anatomical findings and considerations into the surgical planning.

Biomechanical evaluation of the proximal chevron osteotomy in comparison to the Lapidus arthrodesis for the correction of hallux valgus deformities.

PURPOSE: The proximal chevron osteotomy and the modified Lapidus arthrodesis are both procedures utilized for deformity correction in patients with severe symptomatic hallux valgus. The aim of the current study was to compare their biomechanical stability when using locking plate fixation. METHODS: Twelve matched pairs of human anatomical lower leg specimens underwent on one side a proximal chevron osteotomy with a medial locking plate and on the other side a modified Lapidus arthrodesis with a plantar locking plate utilizing an interfragmentary compression screw. All specimens underwent bone mineral density (BMD) assessment and were tested in a servohydraulic load frame which applied a load on the centre of the metatarsal head over 1000 loading cycles with subsequently ultimate load testing. Displacement of the proximal and distal bone segment, ultimate load, and bending stiffness were analyzed. RESULTS: Mean displacement of both procedures showed no statistically significant difference throughout all the loading cycles (0.213 ≤ p ≤ 0.834). The mean ultimate load of the proximal chevron osteotomy was 227.9 N (± 232.4) and of the modified Lapidus arthrodesis 162.9 N (± 74.6) (p = 0.754). The proximal chevron osteotomy (38.2 N/mm (± 24.9)) had a significantly higher bending stiffness compared to the modified Lapidus arthrodesis (17.3 N/mm (± 9.9)) (p = 0.009). There was no correlation between BMD and displacement in all loading cycles, ultimate load, and bending stiffness of either procedure (p > 0.05). CONCLUSION: Although the bending stiffness of the chevron osteotomy was higher, there was no statistically significant difference between the surgical techniques in mean displacement and ultimate load. The BMD did not influence the overall stability of either reconstruction. Locking plate fixation increases the clinical value of the modified Lapidus arthrodesis by outweighing most of the biomechanical disadvantages in comparison to the proximal chevron osteotomy.

Anatomical basis of retrograde thoracic veins flow and its implications in complex thoracic wall reconstructive surgery.

PURPOSE: Internal thoracic veins are increasingly used as recipient's vessels in chest wall reconstructive surgery due to their predictable anatomy and to the possibility to make a double venous anastomosis, exploiting the retrograde flow within them. Over the years, retrograde flow had been explained by the absence of valves in internal thoracic veins, which have been found recently instead. Therefore, our aim is to analyze the retrograde flow and its relationship with valves in the internal thoracic veins. METHODS: We evaluated 32 internal thoracic veins of 16 fresh-frozen specimens with undamaged thoracic cages by dynamic analysis focused on retrograde flow assessment through a partial external circulation system obtained cannulating the subclavian veins. Gross anatomical and morphological evaluations about the presence of valves and their pattern were then made. RESULTS: Efficient, partial, and absent retrograde flow was, respectively, found in 17/30, 8/30 and ITVs and 5/30 internal thoracic veins. Following Arnez's classification, 20/32 Type I and 12/32 Type II internal thoracic veins were identified. Valves were observed in 10/16 specimens (62.50%) corresponding to 36.67% of examined veins (11/30). Three valves were found between the 2nd intercostal space and 12 valves in the 3rd intercostal space. 13/15 valves were bicuspid, 2/15 tricuspid. A significant correlation (p < 0.001) between the retrograde flow and the presence of valves in internal thoracic veins was observed. CONCLUSION: Our study suggests a possible influence of the presence and the number of valves in the efficient retrograde flow of the internal thoracic veins, suggesting that, especially for more complex cases, a preoperative or intraoperative evaluation of the chest wall drainage should be recommended.

Arthroscopic accessibility of the first metatarsophalangeal joint for osteochondral defects of the metatarsal head by two-portal technique - comparing joint distraction and plantarflexion.

BACKGROUND: Several techniques and approaches for first metatarsophalangeal (MTP1) joint arthroscopy have been reported, where joint accessibility plays a key role. This study aimed to evaluate differences in arthroscopic accessibility of the first metatarsal head (MTH1) comparing non-invasive distraction and maximum plantarflexion in a two-portal approach. METHODS: Forty fresh-frozen lower leg specimens were included and divided into a distraction group (D-group) and a plantarflexion group (PF-group). A two-portal technique (1.9 mm-30°-scope) was used for arthroscopy, maximum reach at the MTH1 was marked. Following arthroscopy, specimens were dissected and examined for iatrogenic injuries. The reached area at the chondral surface was pinned and accessibility calculated. RESULTS: Accessibility of the MTH1 was 58.03 % ± 13.64 (D-group) and 55.93 % ± 10.30 (PF-group, p = 0.51). The dorsomedial hallucal nerve was injured in one specimen (2.5 %). CONCLUSION: Maximum plantarflexion showed no difference in arthroscopic MTP1 joint accessibility compared to non-invasive distraction in a two-portal approach. During dorsomedial portal placement, the dorsomedial hallucal nerve is at risk for iatrogenic injury.

The sellar barrier on preoperative imaging predicts intraoperative cerebrospinal fluid leak: a prospective multicenter cohort study.

BACKGROUND: The type of sellar barrier observed between a pituitary tumor and cerebrospinal fluid (CSF) on preoperative magnetic resonance imaging (MRI) may predict intraoperative CSF leak during endonasal pituitary surgery. This is the first multicentric prospective cohort trial to study the sellar barrier concept and CSF leak rate during endoscopic pituitary surgery. METHODS: This multi-center, international study enrolled patients operated for pituitary adenomas via fully endoscopic endonasal surgery over a period of 4 months. The independent variable was the subtype of sellar barrier observed on preoperative MRI (strong, mixed or weak); the dependent variable was the presence of an intraoperative CSF leak. The primary goal was to determine the association between a particular type of sellar barrier and the risk of intraoperative CSF leak. Appropriate statistical methods were then applied for data analysis. RESULTS: Over the study period, 310 patients underwent endoscopic endonasal surgery for pituitary tumor. Preoperative imaging revealed a weak sellar barrier in 73 (23.55%), a mixed sellar barrier in 75 (24.19%), and a strong sellar barrier in 162 (52.26%) patients. The overall rate of intraoperative CSF leak among all patients was 69 (22.26%). A strong sellar-type barrier was associated with significantly reduced rate of intraoperative CSF leak (RR = 0.08; 95% CI 0.03-0.19; p < 0.0001), while a weak sellar barrier associated with higher rates of CSF leak (RR = 8.54; 95% CI 5.4-13.5; p < 0.0001). CONCLUSIONS: The preoperative MRI of pituitary patients can suggest intraoperative CSF leak rates, utilizing the concept of the sellar barrier. Patients with a weak sellar barrier carry a higher risk for an intraoperative CSF leak, whereas a strong sellar barrier on MRI seems to mitigate intraoperative CSF leak. We propose that preoperatively assessment of the sellar barrier can prepare surgeons for intraoperative CSF leak repair.

Resonance frequency analysis of implants placed in condensed bone.

OBJECTIVES: Resonance frequency analysis (RFA) is used to monitor implant stability. Its output, the Implant Stability Quotient (ISQ), supposedly correlates with insertion torque, a common measurement of primary stability. However, the reliability of RFA in condensed bone remains unclear. MATERIAL AND METHODS: In this human cadaver study in edentulous jaws and fresh extraction sockets, implants were inserted using a split-mouth approach into condensed or untreated bone. Mean ISQ, peak insertion torque, and pre- and postoperative bone volume fractions (BV/TV) were assessed. RESULTS: In edentulous jaws, insertion torque and ISQ correlated both in untreated (r = 0.63, p = 0.02) and in condensed (r = 0.82, p  < 0.01) bone. In extraction sockets, insertion torque and ISQ only correlated in untreated (r = 0.78, p < 0.01), but not in condensed bone (r = 0.15, p = 0.58). In all edentulous jaws, preoperative BV/TV correlated with insertion torque (r = 0.90, p < 0.0001), ISQ (r = 0.64, p < 0.001), and changes in BV/TV (r = -0.71, p < 0.01). In all extraction sockets, preoperative BV/TV did not correlate with either insertion torque (r = 0.33, p = 0.15), ISQ (r = 0.38, p = 0.09), or changes in BV/TV (r = -0.41, p = 0.09). Joint analysis identified preoperative BV/TV as a predictor of postoperative BV/TV (p < 0.001), insertion torque (p < 0.001), and ISQ (p < 0.001). CONCLUSIONS: RFA is feasible for monitoring stability after late implant placement into condensed bone, but not after immediate placement into condensed fresh extraction sites.

Transorbital endoscopic approaches to the skull base: a systematic literature review and anatomical description.

Transorbital endoscopic approaches are increasing in popularity as they provide corridors to reach various areas of the ventral skull base through the orbit. They can be used either alone or in combination with different approaches when dealing with the pathologies of the skull base. The objective of the current study is to evaluate the surgical anatomy of transorbital endoscopic approaches by cadaver dissections as well as providing objective clinical data on their actual employment and morbidity through a systematic review of the current literature. Four cadaveric specimens were dissected, and step-by-step dissection of each endoscopic transorbital approach was performed to identify the main anatomic landmarks and corridors. A systematic review with pooled analysis of the current literature from January 2000 to April 2020 was performed and the related studies were analyzed. Main anatomical landmarks are presented based on the anatomical study and systematic review of the literature. With emphasis on the specific transorbital approach used, indications, surgical technique, and complications are reviewed through the systematic review of 42 studies (19 in vivo and 23 anatomical dissections) including 193 patients. In conclusion, transorbital endoscopic approaches are promising and appear as feasible techniques for the surgical treatment of skull base lesions. Surgical anatomy of transorbital endoscopic approaches can be mastered through knowledge of a number of anatomical landmarks. Based on data available in the literature, transorbital endoscopic approaches represent an important complementary that should be included in the armamentarium of a skull base team.

Which experimental procedures influence the apparent proximal femoral stiffness? A parametric study.

BACKGROUND: Experimental validation is the gold standard for the development of FE predictive models of bone. Employing multiple loading directions could improve this process. To capture the correct directional response of a sample, the effect of all influential parameters should be systematically considered. This study aims to determine the impact of common experimental parameters on the proximal femur's apparent stiffness. METHODS: To that end, a parametric approach was taken to study the effects of: repetition, pre-loading, re-adjustment, re-fixation, storage, and µCT scanning as random sources of uncertainties, and loading direction as the controlled source of variation in both stand and side-fall configurations. Ten fresh-frozen proximal femoral specimens were prepared and tested with a novel setup in three consecutive sets of experiments. The neutral state and 15-degree abduction and adduction angles in both stance and fall configurations were tested for all samples and parameters. The apparent stiffness of the samples was measured using load-displacement data from the testing machine and validated against marker displacement data tracked by DIC cameras. RESULTS: Among the sources of uncertainties, only the storage cycle affected the proximal femoral apparent stiffness significantly. The random effects of setup manipulation and intermittent µCT scanning were negligible. The 15∘ deviation in loading direction had a significant effect comparable in size to that of switching the loading configuration from neutral stance to neutral side-fall. CONCLUSION: According to these results, comparisons between the stiffness of the samples under various loading scenarios can be made if there are no storage intervals between the different load cases on the same samples. These outcomes could be used as guidance in defining a highly repeatable and multi-directional experimental validation study protocol.

Maximum Ankle Plantarflexion and Dorsiflexion Allow for Optimal Arthroscopic Access to the Talar Dome: An Anatomic 3-Dimensional Radiography Study.

PURPOSE: (1) to improve the comprehension of the topographical position of the talar dome beneath the inferior articular surface of the tibia and, (2) to illustrate the changes of possible access to the articular surface of the talar dome during arthroscopic treatment of talar osteochondral defects in an anatomical model. METHODS: Twenty matched pairs (n = 40) of anatomical ankle specimen were used. All specimens were mounted in a standardized fashion, 3-dimensional radiography was performed in 4 defined positions (maximum dorsiflexion, neutral position, noninvasive distraction, and maximum plantarflexion). All radiographs were analyzed and statistically compared. RESULTS: Anterior accessibility was highest in maximum plantarflexion (medial: 49.20 ± 9.86%, lateral: 48.19 ± 8.85%), followed by non-invasive distraction (medial: 33.60 ± 7.96%, lateral: 31.98 ± 8.30%). Neutral position (medial: 19.34 ± 6.90%, lateral: 17.54 ± 6.63%) and dorsiflexion (medial: 15.36 ± 5.03%, lateral: 13.88 ± 4.33%) were not able to significantly increase accessibility. Posterior accessibility was greatest in maximum dorsiflexion (medial: 56.69 ± 9.65%, lateral: 46.82 ± 8.36%), followed by neutral position of the ankle joint (medial: 40.95 ± 8.28%, lateral: 31.06 ± 6.92%). Noninvasive distraction (medial: 31.41 ± 8.18%, lateral: 22.99 ± 7.63%) was still significantly better than plantarflexion (medial: 14.54 ± 5.10%, lateral: 13.89 ± 3.14%) and slightly increased accessibility to the talar dome. Medially, a central area of 5.89 ± 9.76% was accessible by maximum plantarflexion and maximum dorsiflexion from anterior and posterior, respectively, laterally a central blind spot of 4.99 ± 8.61% was detected. CONCLUSIONS: From an anatomical point of view, maximum joint positions of the ankle (i.e., plantarflexion and dorsiflexion) allow for better access to the talar dome in anterior and posterior ankle arthroscopy. Noninvasive distraction may increase accessibility in anterior approaches, but has no benefit from posterior. CLINICAL RELEVANCE: This study provides insight into the morphology of the ankle joint in a standardized laboratory setup and illustrates the influence of different surgically relevant ankle joint positions. The presented data allow for better preoperative planning for the arthroscopic treatment of talar osteochondral defects.

On Measuring Implant Fixation Stability in ACL Reconstruction.

Numerous methods and devices are available for implant fixation in anterior cruciate ligament (ACL) reconstruction. Biomechanical data indicate high variability in fixation stability across different devices. This study aims to provide a better insight into measuring the structural characteristics and mechanical behavior of ACL implant fixations. Fourteen human tibial specimens with reconstructed ACLs were subjected to progressively increasing dynamic loading until failure. The motions of the tibia, the proximal and distal graft ends, as well as the testing frame and actuator, were continuously recorded via a motion tracking system. Significantly higher displacements of the machine actuator (1.0 mm at graft slippage onset, and 12.2 mm at ultimate load) were measured compared to the displacements of the proximal (0.8 and 4.3 mm, respectively) and distal graft (0.1 and 3.4 mm, respectively) ends. The displacements measured at different sites showed significant correlations. The provided data suggest significant and systematic inaccuracies in the stiffness and slippage of the fixation when using machine displacement, as commonly reported in the literature. The assessment of the distal graft displacement excludes the artifactual graft elongation, and most accurately reflects the graft slippage onset indicating clinical failure. Considering the high displacement at the ultimate load, the ultimate load could be used as a standardized variable to compare different fixation methods. However, the ultimate load alone is not sufficient to qualitatively describe fixation stability.

Thermal Effects during Bone Preparation and Insertion of Osseointegrated Transfemoral Implants.

BACKGROUND: The preparation of bone for the insertion of an osseointegrated transfemoral implant and the insertion process are performed at very low speeds in order to avoid thermal damages to bone tissue which may potentially jeopardize implant stability. The aim of this study was to quantify the temperature increase in the femur at different sites and insertion depths, relative to the final implant position during the stepwise implantation procedure. METHODS: The procedure for installation of the osseointegrated implant was performed on 24 femoral specimens. In one specimen of each pair, the surgery was performed at the clinically practiced speed, while the speed was doubled in the contralateral specimen. Six 0.075 mm K fine gauge thermocouples (RS Components, Sorby, UK) were inserted into the specimen at a distance of 0.5 mm from the final implant surface, and six were inserted at a distance of 1.0 mm. RESULTS: Drilling caused a temperature increase of <2.5 °C and was not statistically significantly different for most drill sizes (0.002 < p < 0.845). The mean increase in temperature during thread tapping and implant insertion was <5.0 °C, whereas the speed had an effect on the temperature increase during thread tapping. CONCLUSIONS: Drilling is the most time-consuming part of the surgery. Doubling the clinically practiced speed did not generate more heat during this step, suggesting the speed and thus the time- and cost-effectiveness of the procedure could be increased. The frequent withdrawal of the instruments and removal of the bone chips is beneficial to prevent temperature peaks, especially during thread tapping.