Effect of shape and size of supraspinatus tears on rotator cuff strain distribution: an in vitro study.

BACKGROUND: The impact of the size and shape of a supraspinatus tear on the strain of the intact rotator cuff and the kinematics of the shoulder is still unknown. This, however, can be relevant when deciding whether surgical reconstruction is required to prevent an increase in a tendon defect. In this study, the effect of tear width and shape on rotator cuff strain and glenohumeral kinematics was evaluated during active abduction. METHODS: Twelve fresh-frozen cadaveric shoulders with intact rotator cuffs were used in this study. We created 50% and 100% wide (full-thickness) crescent-shaped (CS) tears (n = 6) and reverse L-shaped (rLS) tears (n = 6) in the supraspinatus tendon and measured strain and kinematics during active humeral elevation until 30°. RESULTS: Both tear shapes and sizes led to an increase in internal rotation, supraspinatus loading force, and superior translation of the humerus. For the 100% wide tear size, anterior translation was observed in the CS tear group, whereas in the rLS tear group, this translation occurred mainly in the posterior direction. Strain was higher in the infraspinatus during the first 25° of abduction in comparison with the supraspinatus tendon in both tear shape groups. An analysis of the anterior and posterior tear borders showed a higher strain concentration on the same side of the tear in the CS tear group with 50% and 100% wide tears. CONCLUSIONS: The influence of different tear shapes on translation in the anterior-posterior direction was evident as both CS and rLS tears led to an oppositely directed translation of the humeral head. The strain analysis showed a stress-shielding effect of the infraspinatus at the beginning of abduction. Therefore, special attention must be paid to correctly identify the tear extension and adequately reconstruct the rotator cuff footprint. Moreover, the constant location of maximum strain in the CS tear group may lead to an earlier progression than in the rLS tear group.

Anatomical and biomechanical evaluation of the lateral calcaneo-cuboid and bifurcate ligaments.

BACKGROUND: This study aims to analyze the ligaments of the dorso-lateral calcaneo-cuboid joint and to assess the biomechanical relevance of the bifurcate ligament. METHODS: 16 specimens were analyzed for their ligamentous anatomy of the dorso-lateral calcaneo-cuboid joint and side-alternating assigned to two groups with varying ligamentous dissection order. The Chopart joint was stressed in plantar, medial, and lateral direction measuring the displacement by an 3D motion tracker for every dissection step. RESULTS: 37.5% of specimens had all ligaments (lateral calcaneo-cuboid, dorsal calcaneo-cuboid, bifurcate calcaneo-cuboid, bifurcate calcaneo-navicular), 37.5% were lacking bifurcate´s calcaneo-cuboid-portion, and 25% presented without dorsal calcaneo-cuboid. Biomechanical testing revealed no significant displacement within the calcaneo-cuboid or talo-navicular joint for any stressed state except for axial compression with dissected dorsal talo-navicular joint capsule in Group 2. CONCLUSION: Broad morphological variability and missing significant displacement regardless of its integrity, make the bifurcate ligament appear of limited biomechanical relevance.

Minimally Invasive Approaching in Hip Surgery-An Anatomical Investigation of 20 Specimens.

Background and objectives: Based on the preparation of 20 formalin-fixed anatomical cadavers, the feasibility of the anterior, minimally invasive approach to the hip joint was investigated in each side of the body. The hypothesis of the study was that the Lateral Femoral Cutaneous Nerve can be spared under the use of this approach. Materials and Methods: The anterior approach to the hip was performed via an incision of 8 cm. The position of the nerve was noticed in relation to the skin incision, and the distance was measured in millimeters. The nerves main, gluteal and femoral trunk were distinguished and investigated for injury. Results: No injury of the main trunk was noticed. The average distance of the main trunk to the skin incision was 14.9 and 15.05 mm in the medial direction, respectively (p < 0.001). Injury of the gluteal branch has to be considered at an overall rate of 40%. Conclusions: The anterior, minimally invasive approach to the hip joint can be performed without injury of the Lateral Femoral Cutaneous Nerve.

High-Resolution Ultrasonography of the Transverse Cervical Nerve.

The transverse cervical nerve (TCN) is a superficial cutaneous branch of the cervical plexus that innervates the skin of the anterolateral neck. Therefore, it is exposed to injury in anterolateral cervical surgery, which can cause neuropathic pain. To provide a method with which to relieve patients' pain, this study aimed to evaluate the possibility of visualization, diagnostic assessment and blockade of the TCN with high-resolution ultrasound (HRUS). HRUS with high-frequency probes (15-22 MHz), guided ink-marking and consecutive dissection on both sides in nine fresh cadaver necks (n = 18) was conducted. On both sides of 20 healthy volunteers (n = 40), the distances between the greater auricular nerve (GAN) and the TCN at the posterior border of the sternocleidomastoid muscle were measured. Finally, cases referred to HRUS examinations because suspected TCN lesions were assessed. The TCN was visible in all anatomic specimens and in healthy volunteers. Dissection confirmed HRUS findings in all anatomic specimens (100%). In healthy volunteers, the mean distance between the GAN and the TCN was 10.42 ± 3.20 mm. The median visibility, rated on a five-point Likert scale, was four, reflecting good diagnostic quality. There were six patients with visible abnormalities on HRUS. This study confirmed the reliable visualization of the TCN with HRUS in anatomic specimens, healthy volunteers and patients.

The vascularized fascia lata free flap: an anatomical study and clinical considerations.

PURPOSE: Fascia lata (FL) is often used as fascial component of the anterolateral thigh (ALT) flap in head and neck reconstruction. No distinct data exist on whether the FL has its own reliable vascular supply and whether the fascia alone can be harvested as a fascia lata free flap. METHODS: We dissected 25 thighs of 15 cadavers. The lateral circumflex femoral artery (LCFA) was identified, and the size of stained fascia and skin were measured after injection of methylene blue into the descending branch (DB). Finally, topography of fascial vessels was determined. RESULTS: Staining of fascia and skin paddle was found in all 25 cases. Ascending skin perforators of the DB of the LCFA gave off branches for supply of the FL enabling harvest of a fascia lata free flap. Septo- or musculocutaneous perforators pierced FL and entered skin within the proximal 38.6-60% of the thigh. The mean length and width of stained FL was 15.8 ± 4.1 cm and 8.7 ± 2.0 cm, respectively, and size of stained FL ranged from 40.0 to 336.0 cm2. In 20 cases (80%), skin paddles were 2.4 times larger on average compared to corresponding FL. CONCLUSION: We could demonstrate that the FL receives its own vascular supply from perforators of the DB originating from the LCFA. Hence, harvest of a fascia lata free flap is possible, reliable, and the size of the fascia is suitable for reconstruction of small and large defects of the head and neck.

Design of skin islands for a myocutaneous serratus anterior free flap-An anatomical study and clinical implication for pharyngeal reconstruction after laryngopharyngectomy.

OBJECTIVES: The main purpose of this study was to evaluate flap size and flap design of skin islands in myocutaneous serratus anterior free flaps (SAFFs) in fresh cadavers and to further investigate whether myocutaneous SAFFs are suitable flaps for pharyngeal reconstruction after laryngopharyngectomy. METHODS: Dissection and injection of methylene blue were performed in 20 hemithoraces of 13 fresh cadavers to evaluate flap size and location of skin islands. Based on these pre-clinical data, we performed pharyngeal reconstruction with myocutaneous SAFF in five patients after laryngopharyngectomy. RESULTS: Perfused skin paddles were found in all specimens with a mean size of perfused skin islands of 85.6 ± 49.8 cm2 . Lengths and widths of skin islands ranged from 10-21 cm and 6-20.5 cm respectively. Flap size did not significantly differ between males and females (P = 0.998), left compared to right hemithoraces (P = 0.468) and between paired specimens (P = 0.915). All skin islands were found within the upper 29.3%-51.7% of hemithorax (calculated from axilla to costal arch), and between latissimus dorsi muscle posteriorly and anterior axillary line anteriorly. Accordingly, myocutaneous SAFFs were used for pharyngeal reconstruction after laryngopharyngectomy in five patients with advanced hypopharyngeal carcinomas. Three patients had uneventful courses, while one patient developed immediate intraoperative flap loss and another patient developed partial necrosis of SAFF on postoperative day 7. CONCLUSION: Skin islands of SAFF have reliable blood supply, which allow harvest of large myocutaneous SAFFs that can be used also for pharyngeal reconstruction after laryngopharyngectomy.

The influence of brain iron and myelin on magnetic susceptibility and effective transverse relaxation - A biochemical and histological validation study.

Quantitative susceptibility mapping (QSM) and effective transverse relaxation rate (R2*) mapping are both highly sensitive to variations in brain iron content. Clinical Magnetic Resonance Imaging (MRI) studies report changes of susceptibilities and relaxation rates in various neurological diseases which are often equated with changes in regional brain iron content. However, these mentioned metrics lack specificity for iron, since they are also influenced by the presence of myelin. In this study, we assessed the extent to which QSM and R2* reflect iron concentration as well as histological iron and myelin intensities. Six unfixed human post-mortem brains were imaged in situ with a 7 T MRI scanner. After formalin fixation, the brains were sliced axially and punched. 671 tissue punches were subjected to ferrozine iron quantification. Subsequently, brain slices were embedded in paraffin, and histological double-hemispheric axial brain slices were stained for Luxol fast blue (myelin) and diaminobenzidine (DAB)-enhanced Turnbull blue (iron). 3331 regions of interest (ROIs) were drawn on the histological stainings to assess myelin and iron intensities, which were compared with MRI data in corresponding ROIs. QSM more closely reflected quantitative ferrozine iron values (r = 0.755 vs. 0.738), whereas R2* correlated better with iron staining intensities (r = 0.619 vs. 0.445). Myelin intensities correlated negatively with QSM (r = -0.352), indicating a diamagnetic effect of myelin on susceptibility. Myelin intensities were higher in the thalamus than in the basal ganglia. A significant relationship was nonetheless observed between quantitative iron values and QSM, confirming the applicability of the latter in this brain region for iron quantification.

Novel Demonstration of the Anterior Femoral Cutaneous Nerves using Ultrasound.

PURPOSE: Neuropathy of the intermediate (IFCN) and medial femoral cutaneous nerve (MFCN) is a potential iatrogenic complication of thigh surgery and its diagnosis is limited. This study aimed to evaluate the possibility of the visualization and diagnostic assessment of the IFCN and MFCN with high-resolution ultrasound (HRUS). MATERIALS AND METHODS: In this study, HRUS with high-frequency probes (15 - 22MHz) was used to locate the IFCN and the MFCN in 16 fresh cadaveric lower limbs. The correct identification of the nerves was verified by ink-marking and consecutive dissections at sites correlating to nerve positions (R1 - 3), namely, the origin, the mid portion, and the distal portion, respectively. 12 cases with suspected IFCN and MFCN lesions referred to our clinic for HRUS examinations were also assessed. RESULTS: Anatomical dissection confirmed the correct identification of the IFCN in 16/16 branches at all of the different locations (100 %). MFCN was correctly identified at R1 + 3, in all cases (16/16; 100 %), and in 14/16 cases (88 %) at (R2). 12 cases of patients with IFCN and MFCN pathologies (all of iatrogenic origin) were identified. 9 instances of structural damage were visible on HRUS, and all pathologies were confirmed by almost complete resolution of symptoms after selective HRUS-guided blocks with 0.5 - 1 ml lidocaine 2 %. CONCLUSION: This study confirms that the IFCN and the MFCN can be reliably visualized with HRUS throughout the course of these nerves, both in anatomical specimens and in patients.

Evaluation of an experimental oblique plate for osteosynthesis of mandibular condyle fractures.

OBJECTIVE: The aim of this study was to test the bone thickness and potential screw length for osteosynthesis of condylar base fractures (according to the Loukota classification) with an experimental titanium plate, placed in an ideal position against 2 types of conventional plates. STUDY DESIGN: After exclusion of completely edentulous mandibles, 28 dentate macerated mandibles available at the time of the study were included. Linear regression models 1 and 2 compared the sums of the 2 cranial bone thicknesses and the 3 caudal thicknesses among the 3 different plate designs, and linear models 3 and 4 tested the bone thickness in the 2 most cranial screw axes. RESULTS: Linear models 1 and 2 revealed significantly higher potential screw lengths for the experimental oblique plate. Equally, linear models 3 and 4 indicated significantly higher bone thickness for the novel oblique plate. CONCLUSION: The novel proposed oblique plate allows for favorable plate positioning in a biomechanically ideal location with sufficient amounts of local bone for stable plate fixation. When plates with 15-degree angulated screw holes are used, stable bicortical plate fixation can be achieved.

Post Mortem Validation of MRI-Identified Veins on the Surface of the Cerebral Cortex as Potential Landmarks for Neurosurgery.

Background and Objective: Image-guided neurosurgery uses information from a wide spectrum of methods to inform the neurosurgeon's judgement about which tissue to resect and which to spare. Imaging data are registered to the patient's skull so that they correspond to the intraoperative macro- and microscopic view. The correspondence between imaging and optical systems breaks down during surgery, however, as a result of cerebro-spinal fluid drain age, tissue resection, and gravity-based brain shift. In this work we investigate whether a map of surface veins, automatically segmented from MRI, could serve as additional reference system. Methods: Gradient-echo based [Formula: see text]-weighted imaging was performed on two human cadavers heads using a 7 Tesla MRI scanner. Automatic vessel segmentation was performed using the Frangi vesselness filter, and surface renderings of vessels compared with photographs of the surface of the brain following craniotomy. Results: A high level of correspondence was established between vessel maps and the post autopsy photographs. Corresponding veins, including the prominent superior anastomotic veins, could be identified in all brain lobes. Conclusion: Automatic surface vessel segmentation is feasible and the high correspondence to post autopsy photographs indicates that they could be used as an additional reference system for image-guided neurosurgery in order to maintain the correspondence between imaging and optical systems.This has the advantage over a skull-based reference system that veins are clearly visible to the surgeon and move and deform with the underlying tissue, potentially making this surface net of landmarks robust to brain shift.

The influence of distal screw length on the primary stability of volar plate osteosynthesis--a biomechanical study.

BACKGROUND: Extensor tendon irritation is one of the most common complications following volar locking plate osteosynthesis (VLPO) for distal radius fractures. It is most likely caused by distal screws protruding the dorsal cortex. Shorter distal screws could avoid this, yet the influence of distal screw length on the primary stability in VLPO is unknown. The aim of this study was to compare 75 to 100% distal screw lengths in VLPO. METHODS: A biomechanical study was conducted on 11 paired fresh-frozen radii. HRpQCT scans were performed to assess bone mineral density (BMD) and bone mineral content (BMC). The specimens were randomized pair-wise into two groups: 100% (group A) and 75% (group B) unicortical distal screw lengths. A validated fracture model for extra-articular distal radius fractures (AO-23 A3) was used. Polyaxial volar locking plates were mounted, and distal screws was inserted using a drill guide block. For group A, the distal screw tips were intended to be flush or just short of the dorsal cortex. In group B, a target screw length of 75% was calculated. The specimens were tested to failure using a displacement-controlled axial compression test. Primary biomechanical stability was assessed by stiffness, elastic limit, and maximum force as well as with residual tilt, which quantified plastic deformation. RESULTS: Nine specimens were tested successfully. BMD and BMC did not differ between the two groups. The mean distal screw length of group A was 21.7 ± 2.6 mm (range: 16 to 26 mm), for group B 16.9 ± 1.9 mm (range: 12 to 20 mm). Distal screws in group B were on average 5.6 ± 0.9 mm (range: 3 to 7 mm) shorter than measured. No significant differences were found for stiffness (706 ± 103 N/mm vs. 660 ± 124 N/mm), elastic limit (177 ± 25 N vs. 167 ± 36 N), maximum force (493 ± 139 N vs. 471 ± 149 N), or residual tilt (7.3° ± 0.7° vs. 7.1° ± 1.3°). CONCLUSION: The 75% distal screw length in VLPO provides similar primary stability to 100% unicortical screw length. This study, for the first time, provides the biomechanical basis to choose distal screws significantly shorter then measured.

Patient-specific polyetheretherketone facial implants in a computer-aided planning workflow.

PURPOSE: In the present study, we report an innovative workflow using polyetheretherketone (PEEK) patient-specific implants for esthetic corrections in the facial region through onlay grafting. The planning includes implant design according to virtual osteotomy and generation of a subtraction volume. The implant design was refined by stepwise changing the implant geometry according to soft tissue simulations. MATERIALS AND METHODS: One patient was scanned using computed tomography. PEEK implants were interactively designed and manufactured using rapid prototyping techniques. Positioning intraoperatively was assisted by computer-aided navigation. Two months after surgery, a 3-dimensional surface model of the patient's face was generated using photogrammetry. Finally, the Hausdorff distance calculation was used to quantify the overall error, encompassing the failures in soft tissue simulation and implantation. RESULTS: The implant positioning process during surgery was satisfactory. The simulated soft tissue surface and the photogrammetry scan of the patient showed a high correspondence, especially where the skin covered the implants. The mean total error (Hausdorff distance) was 0.81 ± 1.00 mm (median 0.48, interquartile range 1.11). The spatial deviation remained less than 0.7 mm for the vast majority of points. CONCLUSIONS: The proposed workflow provides a complete computer-aided design, computer-aided manufacturing, and computer-aided surgery chain for implant design, allowing for soft tissue simulation, fabrication of patient-specific implants, and image-guided surgery to position the implants. Much of the surgical complexity resulting from osteotomies of the zygoma, chin, or mandibular angle might be transferred into the planning phase of patient-specific implants.

Split-thickness flap with a semicircular punched-ridge pedicled periosteal flap for implant restoration in highly atrophic patients: a technical note.

Attached gingiva is a crucial aspect of healthy peri-implant tissue. Severely atrophied jaws have minimal quantities of attached gingiva. Any surgical procedure bears the potential risk of further loss of attached gingiva. The split-thickness flap described here provides excellent access. Using a biopsy punch, the periosteum is easily cut in semicircular fashion on the labial surface of the bone so that it remains pedicled on the lingual or palatal ridge. The split-thickness flap permits fixation of the gingival flap to the periosteum. The periosteal flap is closed with sutures to achieve soft tissue closure over the implants even in case of simultaneous vestibuloplasty.

Splint sterilization--a potential registration hazard in computer-assisted surgery.

PURPOSE: Registration of preoperative targeting information for the intraoperative situation is a crucial step in computer-assisted surgical interventions. Point-to-point registration using acrylic splints is among the most frequently used procedures. There are, however, no generally accepted recommendations for sterilization of the splint. An appropriate method for the thermolabile splint would be hydrogen peroxide-based plasma sterilization. This study evaluated the potential deformation of the splint undergoing such sterilization. Deformation was quantified using image-processing methods applied to computed tomographic (CT) volumes before and after sterilization. MATERIALS AND METHODS: An acrylic navigation splint was used as the study object. Eight metallic markers placed in the splint were used for registration. Six steel spheres in the mouthpiece were used as targets. Two CT volumes of the splint were acquired before and after 5 sterilization cycles using a hydrogen peroxide sterilizer. Point-to-point registration was applied, and fiducial and target registration errors were computed. Surfaces were extracted from CT scans and Hausdorff distances were derived. Effectiveness of sterilization was determined using Geobacillus stearothermophilus. RESULTS: Fiducial-based registration of CT scans before and after sterilization resulted in a mean fiducial registration error of 0.74 mm; the target registration error in the mouthpiece was 0.15 mm. The Hausdorff distance, describing the maximal deformation of the splint, was 2.51 mm. Ninety percent of point-surface distances were shorter than 0.61 mm, and 95% were shorter than 0.73 mm. No bacterial growth was found after the sterilization process. CONCLUSION: Hydrogen peroxide-based low-temperature plasma sterilization does not deform the splint, which is the base for correct computer-navigated surgery.

Rarefaction of the peripheral nerve network in diabetic patients is associated with a pronounced reduction of terminal Schwann cells.

OBJECTIVE: Peripheral neuropathy is the most frequent neurological complication in diabetic patients. The diagnosis is established by both clinical neurological examination and demonstration of reduced epidermal nerve fibers in skin biopsies (1). Whereas the decrease of free nerve endings has been extensively studied in diabetic patients (2,3), no data are available on possible changes of terminal Schwann cells. Besides their role as scaffold for peripheral nerves, they also play an important role in supporting survival and function of peripheral nerves (4). RESEARCH DESIGN AND METHODS: We analyzed the subepidermal nerve plexus in dermal sheet preparations of deceased diabetic and nondiabetic patients by immunostaining for detection of the neural cell adhesion molecule and quantification of the subepidermal nerve plexus. RESULTS AND CONCLUSIONS: The subepidermal nerve plexus, comprising nerve fibers and ensheathing Schwann cells, was significantly reduced in diabetic patients. Whether the reduction in terminal Schwann cells is cause or consequence of the loss of peripheral nerve fibers remains to be investigated.

Evaluation of bone surface registration applying a micro-needle array.

AIM: In this study we present and evaluated a new registration technology for the jaw-bone surface. It is based on a micromechatronic device for the generation of a "mechanical image" of the bone surface by means of an array of micro-needles that are penetrating the soft tissue until they touch the surface of the bone. This "mechanical impression image" is aligned with the CT data set. MATERIAL AND METHODS: Based on laboratory measurements on 10 specially prepared jawbone models we evaluate the accuracy of this new registration method. RESULTS: Our measurements of the 10 specimens revealed a maximum overall location error of 0.97 mm (range: 0.35-0.97 mm). CONCLUSIONS: From the technical point of view the presented registration technology has the potential to improve the performance (i.e. accuracy and avoidance of errors) of the registration process for bony structures in selected applications of image-guided surgery.

Applying circular posterior-hinged craniotomy to malignant cerebral edemas.

Malignant brain edemas are often fatal, regardless of whether they are treated conservatively with sedation, blood pressure management, mannitol-therapy, hyperventilation and hypothermia, or non-conservatively with routine trepanation. Unfortunately, temporal trepanation may result in significant brain damage through herniation of the cerebrum at the edges of the trepanation openings. In one case of a 26-year-old male with severe head injury, a circular posterior-hinged craniotomy (CPHC) was performed after an ineffective unitemporal trepanation for evacuation of an acute subdural hematoma. This ultimately successful operation prompted experimental and morphologic investigations on a new surgical procedure for lowering intracranial pressure (ICP). In 12 of 15 human cadavers, an experimentally ICP was lowered by a CPHC with between 9-21 mm of frontal elevation of the calvaria. Using computer simulation, the frontal elevations of the calvaria were "virtually" performed on 3D reconstructions from CT scans of skulls, and the intracranial volume gained was measured with a computer software program. The volume increase of the cranial cavity showed a relatively constant relation to the cranial capacity and was increased by 6.0% (+/-0.4%) or 78 cm(3) with a 10 mm elevation and by 12.4% (+/-0.7%) or 160 cm(3) with a 20 mm elevation. There were no significant differences with skulls of different ages or ethnic origin; however, a significant effect of gender (F = 7.074; P < or = 0.013) on the gained volume in percent of the cranial capacity for the 20 mm elevation was observed. This difference can be explained by the inverse relationship between volume increase and cranial capacity (r = -0.507; P < or = 0.004).