Dega Osteotomy for the Treatment of Developmental Dysplasia of the Hip, a Clinical Evaluation and an Anatomic Study based on X-ray and CT Scan.

Background: Dega osteotomy is becoming more widely used for the treatment of developmental dysplasia of the hip (DDH). Objective: A thorough description of this procedure is needed as many of the technical aspects are not fully defined. Moreover, more follow-up series are also needed to evaluate its outcomes. Methods: In this study, we gave a detailed anatomic description for this procedure and also presented our experience as a retrospective radiographic and case-note study. We examined the clinical and radiographic records of 44 patients (48 hips) with varying degrees of DDH. Results: The average age of the patients was 2 months and 7 months while the average follow up period was 41 months. Clinical and radiographic assessment including CT with 3D reconstruction to examine the anatomic characteristics of the osteotomy were undertaken. We found that concentric reduction was achieved in 93.7% with excellent clinical and radiographic outcomes. Only 3 cases needed revision of the Dega osteotomy. The re-operation rate was 12.5%. CT scan revealed that the arcuate line was crossed by the osteotomy in the majority of cases. In 20.7% of cases, a bone cut that was intended to be a Dega osteotomy was found to have been inadvertently implemented as another osteotomy variant. However, this bore no significant effect on the outcome. Conclusion: We found that a well-implemented Dega osteotomy is a reliable tool to cope with the acetabular changes in DDH.

Frontotemporal Orbitozygomatic Transcavernous Approach: Stepwise Cadaveric Dissection for a Safe Corridor.

Background Advances in skull base surgery have increased the need for a detailed understanding of skull base anatomy and its intrinsic relationship to surrounding structures. This has resulted in an improvement in patient outcomes. The frontotemporal orbitozygomatic (FTOZ) transcavernous approach (TCA) is an excellent option for treating complex lesions involving multiple compartments of the skull base, including the sellar and parasellar, third ventricle, orbit, and petroclival region. Objective This article aimed to provide a detailed cadaveric dissection accompanying a thorough procedure description, including some tips and pitfalls of this technique. Methods Microsurgical dissection was performed in four freshly injected cadaver heads at the Cranial Base Neuroanatomy Laboratory, Cleveland Clinic Florida. The FTOZ TCA was performed on both sides of the four specimens. The advantages and disadvantages were discussed based on the anatomic nuances of this approach. Results The FTOZ TCA represented a wide access to the anterior, middle, and posterior fossa. When combined with an anterior clinoidectomy, it allowed for significant and safe internal carotid artery mobilization. This approach created numerous windows, including opticocarotid, carotid-oculomotor, supratrochlear, infratrochlear, anteromedial, anterolateral, and posteromedial triangles. The only drawback was the length of the dissection and the level of surgical acumen required to perform it. Conclusion Despite its technical difficulty, the FTOZ TCA should be considered for the surgical management of basilar apex aneurysms and tumors surrounding the cavernous sinus, sellar/parasellar, retrochiasmatic, and petroclival region. Continuous training and dedicated time in the skull base laboratory can help achieve the necessary skills required to perform this approach.

An anatomic study of the morphologic characteristics of the dorsal capitolunate ligament.

PURPOSE: There is consensus in favor of a description of the dorsal ligaments of the carpus as not including a direct ligament between the lunate and capitate. On the other hand, there is an anatomical formation which, according to the currently accepted description, corresponds to the dorsal midcarpal capsule, itself thickened by the dorsal intercarpal ligament. The question is whether the capsule at this point deserves to be called an individualizable ligament. In our operative experience of the dorsal carpus, we have encountered a stout structure adherent to the lunate and capitate. In this article, we present the anatomic evidence of this structure's existence. METHODS: Seven adult fresh frozen upper extremities were dissected. Three wrists were longitudinally sectioned in line with the middle finger metacarpal. The remaining 4 were dissected dorsally. Two representative samples of the stout structure connecting the lunate to the capitate were sent to pathology for histologic analysis and staining. RESULTS: In all 3 of the longitudinally sectioned wrists, a thick band of tissue could clearly be seen, originating on the lunate, spanning the dorsal interval between the lunate and the capitate, and inserting on the capitate. With this structure intact, dorsal dislocation of the capitate was not possible, but preliminary sectioning of the structure allowed dislocation. In the 4 dorsally dissected wrists, the same connection was observed, palmar to the dorsal intercarpal ligament, in every specimen. The average dimensions of the dorsal capitolunate were: 15.25 ± 1 mm long, 8.75 ± 1 mm wide at the midpoint, and 1.75 ± 1 mm thick. The two specimens sent to pathology after sectioning showed longitudinally oriented collagen fibers. This structure also stained positive for elastin and contained intrasubstance vascular structures. CONCLUSION: There is a stout ligamentous structure connecting the lunate to the capitate, palmar to the dorsal intercarpal ligament. Disruption of this structure appears to be necessary for dorsal dislocation of the capitate. Clinical studies are needed to gain better understanding of the exact function and importance of this structure.

Defining sexual dimorphism in masculinizing chest surgery using 3-dimensional imaging.

There is no consensus on the ideal scar location and inframammary fold (IMF) placement in the gender-affirming double-incision mastectomy technique. Recent advances in imaging technology have facilitated noninvasive investigations into anatomic variability, in many cases, obviating the traditional approach of cadaveric dissection to answer anatomic questions. A better understanding of chest wall sexual dimorphism may allow surgeons who perform gender-affirming procedures to achieve more natural-appearing results. A total of 60 chests were analyzed using either cadaveric dissection (n = 30) or virtual dissection with 3-dimensional (3-D) reconstructions of computed tomography (CT) images (n = 30) using the Vitrea® software. Chest proportions were recorded using each technique, correlating surface anatomy with muscular and bony landmarks. Cadaveric and 3-D radiography chest analysis revealed that natal male chest walls are, on average, wider and longer than natal female chest walls. The pectoralis major muscle dimensions and the location of its insertion were not found to significantly differ between male and female chests. The male nipple-areolar complex (NAC) tended to be narrower in length and width, with a less projecting nipple than the female NAC. Finally, the IMF was found to lie over the interspace between the fifth and sixth rib in both male and female chests. Our findings confirm natal male and female IMF are positioned between the 5th and 6th ribs. This fact affirms the senior author's technique of masculinizing the chest, keeping the masculinized IMF at approximately the same level as the natal female IMF and following the pectoralis major muscle edges to define the resulting scar in a way that differs from previously reported techniques.

Reanalysis of the Posterior Oblique Ligament: Quantitative Anatomy, Radiographic Markers, and Biomechanical Properties.

Background: The posterior oblique ligament (POL) is the largest structure of the posteromedial knee that is at risk of injury in conjunction with the medial collateral ligament (MCL). Its quantitative anatomy, biomechanical strength, and radiographic location have not been assessed in a single investigation. Purpose: To evaluate the 3-dimensional and radiographic anatomy of the posteromedial knee and the biomechanical strength of the POL. Study Design: Descriptive laboratory study. Methods: Ten nonpaired fresh-frozen cadaveric knees were dissected and medial structures were elevated off bone, leaving the POL. The anatomic locations of the related structures were recorded with a 3-dimensional coordinate measuring machine. Anteroposterior and lateral radiographs were taken with radiopaque pins inserted into the pertinent landmarks, and the distances between the collected structures were calculated. Each knee was then mounted to a dynamic tensile testing machine, and pull-to-failure testing was performed to record the ultimate tensile strength, stiffness, and failure mechanism. Results: The POL femoral attachment was a mean of 15.4 mm (95% CI, 13.9-16.8 mm) posterior and 6.6 mm (95% CI, 4.4-8.8 mm) proximal to the medial epicondyle. The tibial POL attachment center was a mean of 21.4 mm (95% CI, 18.1-24.6 mm) posterior and 2.2 mm (95% CI, 0.8-3.6 mm) distal to the center of the deep MCL tibial attachment and a mean of 28.6 mm (95% CI, 24.4-32.8 mm) posterior and 41.9 mm (95% CI, 36.8-47.0 mm) proximal to the center of the superficial MCL tibial attachment. On lateral radiographs, the femoral POL was a mean of 17.56 mm (95% CI, 14.83-21.95 mm) distal to the adductor tubercle and 17.32 mm (95% CI, 14.6-21.7 mm) posterosuperior to the medial epicondyle. On the tibial side, the center of the POL attachment was a mean of 4.97 mm (95% CI, 3.85-6.79 mm) distal to the joint line on anteroposterior radiographs and 6.34 mm (95% CI, 5.01-8.48 mm) distal to the tibial joint line on lateral radiographs, at the far posterior tibial aspect. The biomechanical pull-to-failure demonstrated a mean ultimate tensile strength of 225.2 ± 71.0 N and a mean stiffness of 32.2 ± 13.1 N. Conclusion: The anatomic and radiographic locations of the POL and its biomechanical properties were successfully recorded. Clinical Relevance: This information is useful to better understand POL anatomy and biomechanical properties as well as to clinically address an injury with repair or reconstruction.

The association between unilateral high-riding vertebral artery and atlantoaxial joint morphology: a multi-slice spiral computed tomography study of 396 patients and a finite element analysis.

BACKGROUND CONTEXT: A high-riding vertebral artery (HRVA) can deviate too medially, too posteriorly, or too superiorly to allow the safe insertion of screws. However, it is unknown whether the presence of a HRVA is associated with morphological changes of the atlantoaxial joint. PURPOSE: To investigate the association between HRVA and atlantoaxial joint morphology in patients with and without HRVA. STUDY DESIGN: A retrospective case-control study and finite element (FE) analysis. PATIENT SAMPLE: A total of 396 patients with cervical spondylosis underwent multi-slice spiral computed tomography (MSCT) of cervical spine at our institutions from 2020 to 2022. OUTCOME MEASURES: A series of atlantoaxial joint morphological parameters, including C2 lateral mass settlement (C2 LMS), C1-2 sagittal joint inclination (C1-2 SI), C1-2 coronal joint inclination (C1-2 CI), atlanto-dental interval (ADI), lateral atlanto-dental interval (LADI), and C1-2 relative rotation angle (C1-2 RRA) were measured, and lateral atlantoaxial joints osteoarthritis (LAJs-OA) was recorded. The stress distribution on the C2 facet surface under different torques of flexion-extension, lateral bending, and axial rotation was analyzed by FE models. A 2-Nm moment was applied to all models to determine the range of motion (ROM). METHODS: A total of 132 consecutive cervical spondylosis patients with unilateral HRVA were enrolled in the HRVA group, and 264 patients without HRVA matched for age and sex were enrolled in the normal (NL) group. Atlantoaxial joint morphological parameters were compared between two sides of C2 lateral mass within HRVA or NL group, and between HRVA and NL groups. A 48-year-old woman with cervical spondylosis without HRVA was selected for cervical MSCT. A three-dimensional (3D) FE intact model of the normal upper cervical spine (C0-C2) was created. We established the HRVA model by simulating atlantoaxial morphological changes of unilateral HRVA with FE method. RESULTS: The C2 LMS was significantly smaller on the HRVA side than that on the non-HRVA side in the HRVA group, but C1-2 SI, C1-2 CI, and LADI on HRVA side were significantly larger than those on non-HRVA side. There was no significant difference between left and right sides in the NL group. The difference in C2 LMS (d-C2 LMS) between HRVA side and non-HRVA side in the HRVA group was larger than that in the NL group (P < 0.05). Meanwhile, the differences in C1-2 SI (d-C1/2 SI), C1-2 CI (d-C1/2 CI), and LADI (d-LADI) in the HRVA group were significantly larger than those in the NL group. The C1-2 RRA in the HRVA group was significantly larger than that in the NL group. Pearson correlations showed that d-C1/2 SI, d-C1/2 CI, and d-LADI were positively associated with d-C2 LMS (r=0.428, 0.649, 0.498, respectively, p<.05 for all). The incidence of LAJs-OA in the HRVA group (27.3%) was significantly larger than that in the NL group (11.7%). Compared with the normal model, the ROM of C1-2 segment declined in all postures of the HRVA FE model. We found a larger distribution of stress on the C2 lateral mass surface of the HRVA side under different moment conditions. CONCLUSIONS: We suggest that HRVA affects the integrity of the C2 lateral mass. This change in patients with unilateral HRVA is associated with the nonuniform settlement of the lateral mass and an increase in the lateral mass inclination, which may further affect the degeneration of the atlantoaxial joint because of the stress concentration on the C2 lateral mass surface.

Measurement of the gluteal compartment pressures: A cadaveric study describing safety and reproducibility of two methods.

INTRODUCTION: Gluteal compartment syndrome is an uncommon entity and physicians may use intracompartmental pressure measurements for confirmation of the clinical diagnosis, or in cases where the physical exam is indeterminate. However, there is a paucity of literature describing a safe and reproducible technique to measure gluteal intracompartmental pressures during the diagnosis of gluteal compartment syndrome. The purpose of this cadaveric study is to evaluate the sole previous technique described in the literature to measure gluteal intracompartmental pressures and provide a modified technique which can be safely and reliably utilized clinically. METHODS: A cadaveric study with three phases was performed in 16 gluteal regions in 8 cadavers. In the first phase, the previously described technique was assessed. In the second phase, a modified set of techniques was created and evaluated. In the third phase, inter-user reliability of the modified set of techniques was assessed and calculated using Cohen's ĸ coefficient. In all three phases, methylene blue was injected through pressure monitoring needles into the gluteus maximus (GMax), gluteus medius/minimus (GMM), and the tensor fascia lata (TFL) compartments. Following dissection, rate of successful penetration into each targeted compartment and distance from the neurovascular structures was recorded. RESULTS: The previously described set of techniques was found to be variable. The modified set of techniques was effective, successfully reaching the GMax, GMM, and TFL compartments in 100%, 100%, and 81% of attempts, respectively. Inter-user reliability was excellent (ĸ = 1) for the techniques to reach both the GMax and GMM compartments, and moderate (ĸ = 0.54) for the technique to reach the TFL compartment. Within the GMax, the pressure monitoring needle was at a mean of 5.4±0.6 cm, 4.1±0.7 cm, 6.4±0.5 cm from the sciatic nerve (SN), superior gluteal nerve (SGN), and inferior gluteal nerve (IGN), respectively. Within the GMM, the pressure monitoring needle was at a mean of 9.7±1.4 cm, 7.4±1.3 cm, 11.1±1.7 cm from the SN, SGN, and IGN, respectively. CONCLUSION: The modified set of techniques presented allows the three gluteal compartments to be safely and reproducibly reached to measure intracompartmental pressures during the diagnosis of gluteal compartment syndrome.

Comparison of three surgical techniques of posterolateral knee reconstruction: A cadaver study.

BACKGROUND: Injuries to the posterolateral corner (PLC) of the knee are often overlooked but, require reconstruction in order to restore stability in varus and external rotation. Among the many anatomic and non-anatomic PLC reconstruction techniques available, the modified Larson (mLR), LaPrade (LPR) and Versailles reconstruction (VR) procedures are widely used. HYPOTHESIS: The hypothesis was that anatomic PLC reconstruction (VR and LPR procedures) provides better restoration and control of external rotation. PATIENTS AND METHODS: Fifteen fresh-frozen cadaveric knees were tested to compare the 3 procedures. Varus laxity on stress radiographs in full knee extension and external rotatory laxity on dial test at 30° flexion were quantified at 3 phases: intact knee, PLC sectioned and PLC reconstructed. RESULTS: Mean varus laxity did not differ significantly between techniques in intact knees (p=.14), after PLC sectioning (p=.14) or after PLC reconstruction (p=.17). After PLC reconstruction, varus laxity was restored, with no statistical difference between mLR, VR and LPR compared to intact test values (respectively, -1.0, -1.3 and -1.5; p=.98). In all 3 groups, mean external rotation laxity on dial test at 30° flexion did not significantly differ between intact knees (p=.32) and after PLC sectioning (p=.15). After PLC reconstruction, the mLR technique was significantly less effective in restoring rotational stability than the VR and LPR techniques (p=.025). DISCUSSION: The VR technique provided similar outcomes to LPR for restoring stability in varus and external rotation. The 2 "anatomic" reconstruction procedures (VR and LPR) were significantly more effective than the modified Larson technique for external rotation control, confirming the study hypothesis. Consequently, it remains preferable to use anatomic techniques in multiligament injuries involving the PLC. LEVEL OF EVIDENCE: IV, cadaver study.

Anatomic Study of the Medial Collateral Ligament in Thai Population: A Cadaveric Study of 56 Elbows.

Purpose: This study aims to elucidate basic anatomic and geometric features of MCL, providing more accurate and detailed information, as guidance for surgeons, to improve patient's outcome of the treatment. Methods: The anterior bundle (AB), posterior bundle (PB) and transverse bundle (TB) ligament of 56 fresh frozen Thai cadaveric elbows, were measured and recorded, comprise key ligament's geometric features, footprints and dimensions, and its relation to bony landmarks. Sagittal and coronal planes were used in respect of the anatomical position. Results: The mean distance between the center of AB origin and the apex of medial epicondyle is as follows: 2.97 ± 2.21 mm anteriorly, 4.73 ± 1.60 mm inferiorly in the sagittal plane, and 4.23 ± 1.13 mm deep from the epicondyle in the coronal plane. Its dimension is 6.23 ± 1.02 mm in width and 45.97 ± 6.75 mm in length. The ligament's insertion triangular shape has its base located 28.44 ± 3.51 mm anterior from the posterior olecranon border, and 22.52 ± 2.49 mm superior from the inferior ulnar border. The tip located 50.79 ± 4.86 mm anterior from the posterior olecranon border and 17.64 ± 2.80 mm superior from the inferior ulnar border. Conclusion: Apprehension of the precise geometries and distances of the ligament's footprint relative to key anatomical point is crucial. This stereographically comprehended data are useful for surgeon as reference points to obtain stability, motion, kinetic, and kinematic properties of the elbow. Level of Evidence: Level V evidence. Supplementary Information: The online version contains supplementary material available at 10.1007/s43465-022-00648-x.

A Frontal Route to Middle and Posterior Cranial Fossa: Quantitative Study for the Lateral Transorbital Endoscopic Approach and Comparison with the Subtemporal Approach.

BACKGROUND: Skull base lesions within the middle cranial fossa (MCF) remain challenging. Recent reports suggest that transorbital endoscopic approaches (TOEAs) might be particularly suitable to access the MCF and expose the lateral wall of the cavernous sinus and the Meckel's cave. METHODS: The present study was developed to compare the nuances of the subtemporal approach (STA) with those of the lateral TOEA (LTOEA) to the MCF and posterior cranial fossa (PCF) in cadaveric specimens. After orbital craniectomy, interdural opening of the cavernous sinus lateral wall (CSlw), exposure of the Gasserian ganglion, and extradural elevation of the temporal lobe was performed. Next, anterior endoscopic petrosectomy was performed and the PCF was accessed. We quantitatively analyzed and compared the angles of attack and distances between LTOEA and STA to different structures at the CSlw, petrous apex (PA), and PCF. RESULTS: Cadaveric dissection through the LTOEA completely exposed the CSlw and PA. LTOA exhibited larger distances than the STA to all targets. Importantly, these differences were greater at the PA and its surrounding key anatomic landmarks. The horizontal and vertical angles of attack allowed by the LTOA were smaller both for the CSlw and PA. However, these differences were not significant for the vertical angle of attack at the CSlw. CONCLUSIONS: LTOEA provides a direct ventral route to the medial aspect of MCF, PA, and PCF. Although TOEAs are versatile approaches, the unfamiliar surgical anatomy and limited instrument maneuverability demand extensive cadaveric dissection before moving to the clinical setting.

An anatomic and 3D study of the development of the proximal humeral physis.

PURPOSE: During maturation, the ossification centers of the proximal humerus form a characteristic pattern consisting of a metaphyseal peak and corresponding epiphyseal valley. The surface topographies of the metaphyseal peak and epiphyseal valley are not well described and may have variation with age and structural importance to the pathogenesis of proximal humeral epiphysiolysis. METHODS: High-resolution 3-dimensional surface scans of 24 cadaveric proximal humeral epiphyses and metaphyses in specimens aged 3 to 18 years were obtained. Computer modeling software was used to measure the peak height of the metaphysis and maximal depth of the epiphysis relative to a perpendicular line drawn across the proximal humeral physis. RESULTS: The metaphyseal peak had a mean height of 12.7 ± 1.6 mm while the epiphyseal valley had a mean depth of 13.1 ± 2.1 mm, both consistently positioned in the posterolateral quadrant. Both the absolute metaphyseal peak height (R2 = 0.536; p < 0.001) and absolute epiphyseal valley depth (R2 = 0.524; p < 0.001) increase with advancing age. Multiple linear regression analysis demonstrated that normalized metaphyseal peak height + sex (adjusted R2 = 0.408; p < 0.002) correlated more with age than normalized epiphyseal valley depth + sex (adjusted R2 = 0.128; p < 0.091). CONCLUSION: Prominence of the metaphyseal peak and epiphyseal valley both increase with advancing age, with a lower correlation between normalized sizes with age as compared to the absolute sizes, suggesting that these structures stay relatively proportional with growth.

Risks of injury in distal metatarsal minimally invasive osteotomy when comparing standard and modified techniques: A cadaveric study.

BACKGROUND: The objectives of the study were to evaluate the structures at risk in distal metatarsal mini-invasive osteotomy (DMMO) and to compare standard and intraosseous approaches. METHODS: DMMO was performed on the second and fourth metatarsals of 11 fresh-frozen cadaveric specimens. The standard technique was performed in 11 metatarsals. It was then compared to a modified intraosseous technique that entails starting inside the bone in 11 other metatarsals. The cadavers were dissected to identify unintentional injury to soft tissue structures. RESULTS: In the standard group the most injured structures were the metatarsal joint capsules (MJC) (27%), extensor digitorum longus (EDL) (18%), and extensor digitorum brevis (EDB) (9%). The modified intraosseous group injured the EDL (27%), not the MJC (0%) and the EDB (0%). Distances between osteotomies and the dorsal metatarsal head articular surface (DMHAS) were 6.08 ± 3.99 mm in the standard and 9.92 ± 3.42 mm in the modified (p = 0.02). CONCLUSION: The DMMO techniques most frequently injured the EDL. Intra-articular positioning of the osteotomy was more observed in the standard. Overall, it appears the modified method could be an alternative to the standard DMMO. CLINICAL RELEVANCE: The modified minimally invasive DMMO has a comparable rate of potential iatrogenic injuries. This intraosseous procedure may present as an option when planning surgery to the lesser metatarsals. LEVEL OF EVIDENCE: Level III. Comparative Cadaveric Study.

Neurovascular anatomy of pronator quadratus for reanimation of blepharoptosis.

PURPOSE: Pronator quadratus (PQ) is a quadrilateral muscle on a volar distal side of the forearm. The purpose of this study was to establish a novel surgical technique for reanimation of the upper eyelid for severe ptosis using PQ functional free muscle flap. METHODS: The current study is a cadaveric study, designed to assess a PQ free flap transfer that lies between the frontalis muscle and the upper eyelid. Fourteen PQ from fourteen embalmed cadavers were dissected, and their neurovascular pedicles were isolated. Then they were transferred to the area on the contralateral side between the frontalis muscle and upper eyelid tarsal cartilage. Measurements of the PQ flap, antebrachial region, orbitofrontal region, recipient vessels, and motor nerve were performed using a caliper. The extendibility of neurovascular pedicles was evaluated by measurements of lengths. In addition, the diameter of PQ flap vascular pedicle vessels was compared with recipient vessels. RESULTS: The mean width of the proximal border of PQ was 41.92 ± 2.05 mm and the distal border of the PQ was 42.84 ± 4.04 mm. The mean PQ artery (type II, Mathes-Nahai flap classification) length was found to be 117.72 ± 7.77 mm. The mean diameter of the anterior interosseous nerve was 1.89 ± 0.08 mm. The mean diameter of the uppermost branch of the frontal branch of the facial nerve was 1.18 ± 0.25 mm. The length and diameter of neurovascular pedicles of muscle flaps were adequate for microvascular anastomoses and neurorrhaphy. CONCLUSIONS: The results of this anatomical study demonstrate that the PQ free flap transfer has anatomical features that are suitable and compatible with the surgical treatment of blepharoptosis.

Anatomic Study Quantifying the Relationship Between the Arcuate Eminence and the Root of the Zygoma: Application to Skull Base Surgery.

OBJECTIVE: The aim of this study was to define the structural relationship between the arcuate eminence (AE) and a known fixed external bony landmark, the root of the zygoma (ZR), and to determine its reliability as a consistent guide for guiding surgical approaches. To our knowledge, this is the only anatomic study to quantify the relationship between the AE and ZR. METHODS: Twenty-one dry temporal bones were measured using digital calipers. The distance from the posterior aspect of the ZR to the midpoint of the AE was measured. Additionally, the anteroposterior distance between the ZR and AE and vertical distance between the 2 structures were measured. Student's t-test was used to compare the left and right sides. RESULTS: An AE was found in every specimen. The mean ZR to AE distance was 30.9 mm. On most sides (91%), the ZR was located more inferiorly than the AE with a mean distance of 3 mm between the 2 structures. The mean distance between the AE and ZR was 17 mm. On all sides, the AE was located posterior to the ZR. No significant differences were found between sides. No anatomic variations or pathologic conditions were noted in any of the specimens. CONCLUSIONS: The ZR is an easily identifiable and consistent bony landmark often used by skull base surgeons. In this investigation, we measured the anatomic relationships between the ZR and AE. Such data might assist in planning surgical trajectories and minimizing complications when skull base pathologies are approached.

Comparative Analysis of Pterional, Supraorbital, Extended Supraorbital, and Transtubercular-Transplanum Approaches for Exposing the Anterior Communicating Artery Complex: A Cadaveric Study.

OBJECTIVE: We aimed to quantify and compare surgical exposure and freedom at the anterior communicating artery (ACoA) complex using pterional (PT), supraorbital (SO), extended supraorbital withorbital osteotomy (SOO), and endonasal endoscopic transtubercular-transplanum (EEATT) approaches. METHODS: Right-sided PT, SO, SOO, and EEATT approaches were performed using 10 cadaveric heads. Surgical exposure and freedom (horizontal and vertical attack angle) at the ACoA complex were measured. The farthest clipping distance from ACoA to A1 (precommunicating segment of the anterior cerebral artery)/A2 (postcommunicating segment of the anterior cerebral artery) was also quantified. RESULTS: There was a significantly greater exposure length of right A1 in the PT approach (12.20 ± 2.48 mm) compared with the EEATT approach (9.52 ± 2.09 mm; P = 0.029). Among the 4 approaches, EEATT provided the shortest clipping distance for right A1 (6.56 ± 1.33 mm; P = 0.001) and the longest clipping distance for right A2 (3.36 ± 1.24 mm; P = 0.003). SO, SOO, and PT approaches (2.9 ± 0.9) had more observations on perforators from ACoA than did the EEATT approach (2.0 ± 0.66; P = 0.029). The EEATT approach (50.90 ± 17.45 mm2) provided better exposure of the superior part of the ACoA complex compared with the SO approach (29.37 ± 17.27 mm2; P = 0.05). PT and SOO approaches provided the greatest horizontal (36.88° ± 5.85°) and vertical (19.37° ± 4.70°) attack angle, respectively. CONCLUSIONS: The SO, SOO, and PT approaches provided a better hemilateral view of the ACoA complex and similar surgical exposure, whereas the EEATT approach offered greater exposure in the upper part of the ACoA complex, with relatively limited exposure of perforators from ACoA and surgical freedom. The EEATT approach can play a role in exposure of lesion involving the ACoA complex.

Minimally Invasive Approaches to the Lateral Cavernous Sinus and Meckel's Cave: Comparison of Transorbital and Subtemporal Endoscopic Techniques.

BACKGROUND: Transorbital and subtemporal keyhole approaches have recently been proposed to approach lesions in the lateral wall of the cavernous sinus (CS) and Meckel's cave (MC). Our goal was to compare these approaches and suggest indications for each of them. METHODS: Five cadaver heads (10 sides, 40 procedures) were used. The lateral transorbital approaches were carried out without and with the removal of the lateral orbital rim, herein referred to as the lateral transorbital approach (LTOA) and the lateral orbital wall approach (LOWA). The subtemporal approaches were performed without and with the removal of the zygomatic arch, referred to as the subtemporal approach (STA) and the subtemporozygomatic approach (STZA). Five targets were chosen and 2 triangles were created representing the lateral wall of the CS and MC. Stereotactic measurements were quantified to calculate angles of attack, surgical freedom, and temporal lobe retraction for each approach. RESULTS: LTOA presented the smaller horizontal angles of attack. LOWA increased the angles to the same level of STA and STZA. STA and STZA presented larger vertical angles of attack. The surgical freedom presented gradual increase from LTOA to LOWA, STA, and STZA. STA and STZA needed greater temporal lobe retraction for most targets. CONCLUSIONS: LTOA is a good option to biopsy a lesion in the lateral wall of the CS and LOWA increased the surgical corridor to work with microsurgical techniques. STA and STZA could be better options when wide exposure is necessary, but temporal lobe retraction should be taken into consideration.

Biportal endoscopic transorbital approach: a quantitative anatomical study and clinical application.

BACKGROUND: We devised a biportal endoscopic transorbital approach (BiETOA) to gain surgical freedom by making a port for the endoscope and investigated the benefits and limitations of BiETOA. METHODS: A cylindrical port was designed and 3-D printed using biocompatible material. The port was inserted through a keyhole between the superolateral side of the orbital rim and the temporal muscle. An endoscope was inserted through the port, and other instruments were inserted through the conventional transorbital route. BiETOA was used to dissect eight cadaveric heads, and the angle of attack and surgical freedom were assessed. RESULTS: The mean maximal angle of attack was significantly different in BiETOA and endoscopic transorbital approach (ETOA) (P < 0.01) but not in BiETOA and ETOA lateral orbital rim (LOR) osteotomy (P = 0.207, P = 0.21). The mean surgical freedom was significantly different in BiETOA and ETOA (P < 0.01) and in BiETOA and ETOA LOR osteotomy (P < 0.01). In the clinical cases, tumors were removed successfully without any complications. CONCLUSIONS: BiETOA provided increased surgical freedom and better visibility of deep target lesion and resulted in good surgical and cosmetic outcomes.

Ulnar facet locking screw locations of volar locking plates placed without flexor pollicis longus tendon contact: A cadaver study.

BACKGROUND: The volar locking plate (VLP) system provides stable fixation and is widely used for distal radius fractures. Studies have shown that irritation of the implant prominence is a risk factor for flexor tendon rupture, especially of the flexor pollicis longus (FPL). Contact between VLPs and flexor tendons should be avoided. We aimed to investigate the ulnar facet locking screw locations of various VLPs placed without FPL tendon contact in cadaver wrists. HYPOTHESIS: We hypothesized that ulnar facet locking screws would be in the vicinity of the subchondral bone when the plate is placed in the most distal position without FPL tendon contact. MATERIALS AND METHODS: The study assessed two variable-angles and four fixed locking plates. We placed each plate in six different cadavers, resulting in 36 different plate-cadaver combinations. Plates were placed in the most distal position without FPL tendon contact. We drilled the most ulnar hole (hole A) and the second ulnar hole (hole B) of the distal row. All drilling procedures were performed using a specific jig for each fixed locking plate. For variable-angle locking plates, we drilled with a fixed jig for each plate. We obtained lateral radiographs when the drill penetrated the dorsal cortex and measured the distance between the drill and the articular surface. RESULTS: With regard to hole A, the mean distances between the drill and the center of the articular surface were 2.6-5.2mm for the four fixed locking plates and 4.9-5.6mm for the two variable-angle locking plates. With regard to hole B, the mean distances between the drill and the center of the articular surface were 3.8-5.9mm for the four fixed locking plates and 5.5-5.9mm for the two variable-angle locking plates. DISCUSSION: When clinicians place a VLP without FPL tendon contact, the distance between the ulnar facet screws and the center of the articular surface is over 3mm in most cases. Surgeons should select variable-angle drilling for strong articular support when using variable-angle locking plates. LEVEL OF EVIDENCE: III, diagnostic Level.

What is the difference in morphologic features of the lumbar vertebrae between Caucasian and Taiwanese subjects? A CT-based study: implications of pedicle screw placement via Roy-Camille or Weinstein method.

BACKGROUND: Safe placement of pedicle screws without jeopardizing neurovascular structures medially and anteriorly is important during spine surgery. Inferior breach of pedicle is also dangerous due to low margin of error. Lumbar morphology and identical pedicle orientation at L1 to L5 shown on CT scan of young Taiwanese patients (90 patients) were analyzed and compared with findings reported for Caucasian subjects. METHODS: Previously reported techniques were employed to quantitatively elucidate the parameters regarding lumbar morphology and identical pedicle orientation at each vertebra. The parameters for pedicle angle (PA), pedicle diameter (PD), pedicle axis distance (PAD), midline axis distance (MAD), transverse pedicle axis distance (TPAD) and transverse intertangential angle (TITA) were measured. RESULTS: Taiwanese subjects had different PA, PD, PAD, MAD at L1 to L5 and TITA at L3 to L5 compared with Caucasian subjects. L5 had the most convergent pedicle axis, the widest PD and the shortest antero-posterior axis morphology. CONCLUSIONS: This study provides detailed information for identifying pedicle orientation during pedicle screw placement and elucidate racial differences in lumbar morphology and pedicle orientation between Taiwanese and Caucasian populations.

The distance from the peroneal tendons sheath to the sural nerve at the posterior tip of the fibula decreases from proximal to distal.

PURPOSE: The aim of this study is to compare the distance from the peroneal tendons sheath to the sural nerve in different points proximally and distally to the tip of the fibula. METHODS: Ten fresh-frozen lower extremities were dissected to expose the nerves and tendons. Having the posterior tip of the fibula as a reference, the distance between the tendons sheath and the sural nerve was measured in each point with a tachometer with three independent different observers. Two measures were taken distally at 1.5 and 2 cm from fibula tip and 3 measures were performed proximally at 2, 3, and 5 cm from fibula tip. Data were described using means, standard deviations, medians, and minimum and maximum values. RESULTS: The average distance between distance between the fibula tip and sural nerve is 16.6 ± 4.4 mm. The average distance between peroneal tendons sheath and the sural nerve at 5 cm, 3 cm, and 2 cm from the proximal fibular tip was 29.6 ± 3.2 mm, 24.2 ± 3.6 mm, and 19.7 ± 2.7 mm, respectively. The average distance between the peroneal tendons sheath and the sural nerve at 2 cm and 1.5 cm distal to fibular tip was 9.1 ± 3.5 mm and 7.8 ± 3.3 mm, respectively. CONCLUSION: The distance from the peroneal tendons sheath to the sural nerve decreases from proximal to distal. As the distance between the peroneal tendons sheath and the sural nerve decreases from proximal to distal, performing the tendoscopy portal more distally would increase the risk of nerve iatrogenic injury.