BIOMECHANICAL SIMULATION OF RADIAL HEAD SUBLUXATION IN CADAVERIC PEDIATRIC ELBOWS

Background: Radial head subluxation, known as pulled elbow or Nursemaid’s elbow, is a common pediatric condition that occurs when a longitudinal traction force is applied to an elbow that is pronated and extended. Although the stability of the proximal radioulnar joint has been previously examined in cadaveric models, there are no current studies quantifying the biomechanics of nursemaid’s elbow. The purpose of our study was to demonstrate and quantify the axial traction force required to produce a nursemaid’s elbow in a pediatric cadaver specimen. Methods: Two fresh-frozen cadaveric elbows from a single 3 year-old male donor were dissected by a fellowship-trained orthopedic surgeon. An Instron 5944 testing machine with a 2 kN load cell was used to perform uniaxial testing. The radius and humerus were mounted to the Instron machine, and loaded in the axial direction with the elbow in full extension. Loading occurred at a rate of 10 mm/sec for 4 seconds, during which the force and actuator displacement were continuously recorded. The local instantaneous load and extension displacement at the time of subluxation were recorded, and data was synced with high-frame-rate video footage used to confirm the annular ligament subluxation. Results: The load to failure required to produce the nursemaid’s elbow injury in the first elbow was 31N, with a failure displacement of 4.6mm. The second elbow demonstrated a load to failure of 26N, with a failure displacement of 4.6mm. After subluxation, we reduced the annular ligament from the first specimen. The elbow was then re-tested and demonstrated a load to failure of 20N, with a failure displacement of 2.6mm. Conclusion: Axial traction applied to a pediatric cadaver specimen results in subluxation of the annular ligament into the radiocapitellar joint. The mean load to failure is 28.5N, and a lower load to failure was required to produce a recurrent subluxation in a previously injured specimen. Lower load for a recurrent subluxation may be attributed to damage on the annular ligament due to the first subluxation. [Figure: see text]

Multimodal control of neck muscles for vestibular mediated head oscillation damping during walking: a pilot study

Purpose It is still in question whether head oscillation damping during walking forms a part of the vestibular function. The anatomical pathway from the vestibular system to the neck muscles via the medial vestibulospinal tract (MVST) is well known but there is a lack of knowledge of the exact influence and modulation of each other in daily life activities. Methods (I) We fixed a head–neck unit of a human cadaver specimen in a steal frame to determine the required pitch-torque for a horizontal head position. The mean value of the acquired pitch-torque was 0.54 Nm. (II) On a motorized treadmill we acquired kinematic data of the head, the sternum and both feet by wireless 3D IMUs for seven asymptomatic volunteers. Subsequently three randomized task conditions were performed. Condition 1 was walking without any irritation. Condition 2 imitated a sacculus irritation using a standardized cVEMP signal. The third condition used an electric neck muscle-irritation (TENS). The data were analyzed by the simulation environment software OpenSim 4.0. Results 8 neck muscle pairs were identified. By performing three different conditions we observed some highly significant deviations of the neck muscle peak torques. Analysing Euler angles, we found during walking a LARP and RALP head pendulum, which also was strongly perturbated. Conclusion Particularly the pitch-down head oscillation damping is the most challenging one for neck muscles, especially under biomechanical concerns. Mainly via MVST motor activity of neck muscles might be modulated by vestibular motor signals. Two simultaneous proprioceptor effects might optimize head oscillation damping. One might be a proprioceptive feedback loop to the vestibular nucleus. Another might trigger the cervicocollic reflex (CCR).

New Adjustable Unloader Knee Brace and Its Effectiveness

Unloader knee braces are prescribed for patients with unicompartmental osteoarthritis of the knee. These braces aim to reduce pain in patients by applying a coronal moment to the knee to unload the symptomatic knee compartment. However, existing unloading mechanisms use straps that go directly behind the knee joint, to apply the needed moment. This can impinge on the popliteal artery and peroneal nerves thereby causing discomfort to the patient. Hence, these braces cannot be worn for prolonged periods of time. This research focused on developing a new knee brace to improve comfort while unloading the osteoarthritic knee. A new knee brace was developed that uses a four-point bending approach to unload the knee. In this brace, unloading can be adjusted, and the unloading mechanism is away from the joint. The new brace was tested on a cadaver specimen to quantify its capability to unload the knee compartment. The brace was also worn by a patient with osteoarthritis who subjectively compared it to his existing unloader brace. During cadaver testing, the new brace design could reduce the force exerted on the medial condyle by 25%. Radiographic images of the patient's knee confirmed that the brace unloaded the medial condyle successfully. The patient reported that the new brace reduced pain, was significantly comfortable to wear and could be used for a longer duration in comparison to his existing brace.

Plantar Fascia Release Through a Single Lateral Incision

Category: Hindfoot, Midfoot/Forefoot, Cadaver Study Introduction/Purpose: Plantar fascia release (PFR) and calcaneal slide osteotomy (CSO) are often components of surgical management for cavus deformities of the foot. In this setting, the PFR has traditionally been performed through an incision over the medial calcaneal tuberosity, while the CSO is performed through a lateral incision. Two separate incisions can potentially increase surgical morbidity. We hypothesized that the plantar fascia could be fully released from the same lateral based incision that is used for the CSO, obviating the need for a medial incision. Methods: Six cadaver feet were dissected. A medial sided dissection was performed to isolate the tibial, medial plantar, lateral plantar, and calcaneal nerves, and the origin of the plantar fascia. Next, an incision was made on the lateral aspect of the ankle inferior and parallel to the peroneus longus tendon. Dissection was carried to bone. A curved face osteotome was utilized to sweep the plantar fascia off the calcaneus just distal to its proximal insertion. A #10 scalpel was inserted into this space, parallel to the plantar fascia and was directed towards the plantar fascia insertion; it was then turned ninety degrees so that the blade was perpendicular to the plantar fascia. The ankle was dorsiflexed until a full release was achieved. A Stryker oscillating saw was used to create a CSO through the lateral incision. We then inspected the medial structures in their relationship to the PFR and CSO. Results: In all six cadavers, the plantar fascia was fully released from its origin at the medial calcaneal tuberosity through the lateral incision. There was no obvious damage to the medial and lateral plantar nerves with this lateral based PFR. The CSO made through the lateral incision reliably crossed the calcaneal branch of the tibial nerve in all specimens and the osteotomy was posterior to the lateral and medial branches of the tibial nerve. Conclusion: PFR through a lateral incision is a safe and reliable method as part of the surgical treatment for cavus deformities of the foot. We achieved a full PFR in each cadaver specimen. An added benefit is that PFR through a lateral incision avoids the morbidity of an additional surgical incision. Further, a calcaneal slide osteotomy performed through a lateral based incision reliably crosses the calcaneal branch of the tibial nerve. Both PFR and CSO can be safely performed through a lateral incision; however, care must be taken when completing the CSO to ensure that the medial neurovascular structures remain uninjured.

The Subtalar Joint Axis Palpation Technique

Background Clinically locating the point of no rotation to determine the subtalar joint axis location by applying pressure on the plantar surface of the foot was described by Kirby in 1987 but was never validated. We sought to extend a previously validated mechanical model to cadaver feet and to examine the intratester and intertester reliability. Methods Four testers with different levels of experience determined the subtalar joint axis location and moved the subtalar joint through its range of motion, capturing the movement using kinematic analysis. The comparison of the spatial subtalar joint axis location as determined by palpation between and within testers determined the intertester and intratester reliability. The helical axis method was performed to validate the model. Results The intrarater reliability varied from a high of α = 0.96 to a low of α = 0.26 for the slope and was, in general, high (α = 0.78–0.95) for the intersection. The interrater reliability scored moderate to high, depending on the specific cadaver specimen. Concerning the exact location of the subtalar joint axis, no significant difference was found between the results determined by different testers and the helical axis method. Conclusions The palpation technique as part of the subtalar joint axis location and rotational equilibrium theory proposed by Kirby is a reliable and valid clinical tool. Experience in performing the palpation technique has a positive influence on the accuracy of the results. In the context of evidence-based practice, this technique could be a standard tool in the examination of patients with lower-limb–related pathologic disorders.

Creating Physiologically Realistic Vertebral Fractures in a Cervine Model

Approximately 50% of women and 25% of men will have an osteoporosis-related fracture after the age of 50, yet the micromechanical origin of these fractures remains unclear. Preventing these fractures requires an understanding of compression fracture formation in vertebral cancellous bone. The immediate research goal was to create clinically relevant (midvertebral body and endplate) fractures in three-vertebrae motion segments subject to physiologically realistic compressional loading conditions. Six three-vertebrae motion segments (five cervine, one cadaver) were potted to ensure physiologic alignment with the compressive load. A 3D microcomputed tomography (microCT) image of each motion segment was generated. The motion segments were then preconditioned and monotonically compressed until failure, as identified by a notable load drop (48–66% of peak load in this study). A second microCT image was then generated. These three-dimensional images of the cancellous bone structure were inspected after loading to qualitatively identify fracture location and type. The microCT images show that the trabeculae in the cervine specimens are oriented similarly to those in the cadaver specimen. In the cervine specimens, the peak load prior to failure is highest for the L4–L6 motion segment, and decreases for each cranially adjacent motion segment. Three motion segments formed endplate fractures and three formed midvertebral body fractures; these two fracture types correspond to clinically observed fracture modes. Examination of normalized-load versus normalized-displacement curves suggests that the size (e.g., cross-sectional area) of a vertebra is not the only factor in the mechanical response in healthy vertebral specimens. Furthermore, these normalized-load versus normalized-displacement data appear to be grouped by the fracture type. Taken together, these results show that (1) the loading protocol creates fractures that appear physiologically realistic in vertebrae, (2) cervine vertebrae fracture similarly to the cadaver specimen under these loading conditions, and (3) that the prefracture load response may predict the impending fracture mode under the loading conditions used in this study.

Mechatronic Feasibility of Minimally Invasive, Atraumatic Cochleostomy

Robotic assistance in the context of lateral skull base surgery, particularly during cochlear implantation procedures, has been the subject of considerable research over the last decade. The use of robotics during these procedures has the potential to provide significant benefits to the patient by reducing invasiveness when gaining access to the cochlea, as well as reducing intracochlear trauma when performing a cochleostomy. Presented herein is preliminary work on the combination of two robotic systems for reducing invasiveness and trauma in cochlear implantation procedures. A robotic system for minimally invasive inner ear access was combined with a smart drilling tool for robust and safe cochleostomy; evaluation was completed on a single human cadaver specimen. Access to the middle ear was successfully achieved through the facial recess without damage to surrounding anatomical structures; cochleostomy was completed at the planned position with the endosteum remaining intact after drilling as confirmed by microscope evaluation.

The “Skull Flap” a new conceived device for decompressive craniectomy/cranioplasty: Feasibility study on cadaver specimen

ABSTRACT Background: Decompressive craniectomy (DC) is a procedure that is currently performed with increasing frequency. The reason is that its indications have become much broader. This procedure may be associated with the relevant morbidity in the postoperative stage due to the creation of a large bone defect. On the other hand, cranioplasty is associated too with some of the common complications related to any reconstructive head surgery. The authors present a newly developed device: The “Skull Flap” (SF). This new device allows the surgeon to complete a DC, yet providing at the same time a cranial reconstruction that will not require the patient to undergo a second reconstructive procedure. Materials and Methods: Different size and location craniectomies were carried out on four human cadaveric heads; the bone flaps were then repositioned in a more elevated position with respect to the skull edges. The flaps were placed at a distance of 12 and 15 mm from the skull edges using the SF system. Crash tests were conducted on each flap while in open and closed positions to assess its reliability and efficacy. Results: SF was shown to be a strong fixation device that allows satisfactory brain decompression by keeping the original bone flap away from the swollen brain; at the same time, in a later stage, it allows cranial reconstruction in a simple way. Conclusion: The SF device was shown to be very easy to use, adaptable, and practical to apply; thus, allowing both satisfactory brain decompression as well as bone flap repositioning at a later time after the brain swelling has subsided.