Biomimetic sensory feedback through peripheral nerve stimulation improves dexterous use of a bionic hand.

We describe use of a bidirectional neuromyoelectric prosthetic hand that conveys biomimetic sensory feedback. Electromyographic recordings from residual arm muscles were decoded to provide independent and proportional control of a six-DOF prosthetic hand and wrist-the DEKA LUKE arm. Activation of contact sensors on the prosthesis resulted in intraneural microstimulation of residual sensory nerve fibers through chronically implanted Utah Slanted Electrode Arrays, thereby evoking tactile percepts on the phantom hand. With sensory feedback enabled, the participant exhibited greater precision in grip force and was better able to handle fragile objects. With active exploration, the participant was also able to distinguish between small and large objects and between soft and hard ones. When the sensory feedback was biomimetic-designed to mimic natural sensory signals-the participant was able to identify the objects significantly faster than with the use of traditional encoding algorithms that depended on only the present stimulus intensity. Thus, artificial touch can be sculpted by patterning the sensory feedback, and biologically inspired patterns elicit more interpretable and useful percepts.

Restoring motor control and sensory feedback in people with upper extremity amputations using arrays of 96 microelectrodes implanted in the median and ulnar nerves.

OBJECTIVE: An important goal of neuroprosthetic research is to establish bidirectional communication between the user and new prosthetic limbs that are capable of controlling >20 different movements. One strategy for achieving this goal is to interface the prosthetic limb directly with efferent and afferent fibres in the peripheral nervous system using an array of intrafascicular microelectrodes. This approach would provide access to a large number of independent neural pathways for controlling high degree-of-freedom prosthetic limbs, as well as evoking multiple-complex sensory percepts. APPROACH: Utah Slanted Electrode Arrays (USEAs, 96 recording/stimulating electrodes) were implanted for 30 days into the median (Subject 1-M, 31 years post-amputation) or ulnar (Subject 2-U, 1.5 years post-amputation) nerves of two amputees. Neural activity was recorded during intended movements of the subject's phantom fingers and a linear Kalman filter was used to decode the neural data. Microelectrode stimulation of varying amplitudes and frequencies was delivered via single or multiple electrodes to investigate the number, size and quality of sensory percepts that could be evoked. Device performance over time was assessed by measuring: electrode impedances, signal-to-noise ratios (SNRs), stimulation thresholds, number and stability of evoked percepts. MAIN RESULTS: The subjects were able to proportionally, control individual fingers of a virtual robotic hand, with 13 different movements decoded offline (r = 0.48) and two movements decoded online. Electrical stimulation across one USEA evoked >80 sensory percepts. Varying the stimulation parameters modulated percept quality. Devices remained intrafascicularly implanted for the duration of the study with no significant changes in the SNRs or percept thresholds. SIGNIFICANCE: This study demonstrated that an array of 96 microelectrodes can be implanted into the human peripheral nervous system for up to 1 month durations. Such an array could provide intuitive control of a virtual prosthetic hand with broad sensory feedback.

The effects of drilling force on cortical temperatures and their duration: an in vitro study.

Bone loss due to thermonecrosis may weaken the purchase of surgically placed screws and pins, causing them to loosen post-operatively. The goal of this study was to determine how differences in applied drilling forces affect the temperature of cortical tissue near the drilling site. Results from thermocouples placed into fresh cortical bone indicate that increasing the applied drilling force resulted in a significant decrease (P=0.001) of maximum cortical temperatures. Furthermore, increasing the drilling force resulted in a significant decrease (P=0.001) in the average duration of temperature elevations above 50 degrees C. The results of the current study demonstrate that by the application of a larger force to the drill, both maximum cortical temperatures and their duration above 50 degrees C may be effectively reduced, decreasing the potential for thermal necrosis in the neighboring cortical bone.

Pins and plaster vs external fixation in the treatment of unstable distal radial fractures. A randomized prospective study.

90 unstable fractures of the distal radius were studied in a randomized, prospective manner. Follow-up consisted of patient questionnaire, medical record review, therapist evaluation and radiography at 4 months, 1 year and 2 years post-operatively. Overall results were good or excellent in 94%. No significant differences were found between treatment groups (external fixation and pins and plaster) in final results, range of motion, intrinsic tightness, grip strength, or the presence of arthritis. The complication rate was high for both groups (45%), and half of the complications were major. External fixation maintained radial length more effectively (significantly in those patients followed for 2 years) but was associated with higher initial costs (20 times) and a greater number of minor complications.

Color duplex imaging. Applications to upper-extremity and microvascular surgery.

Color duplex scanning is a relatively new noninvasive vascular test combining ultrasound, Doppler recording, and color. It has numerous documented applications to various other subspecialties but only recently has been used in upper-extremity and microvascular surgery. It is quite useful in evaluating masses, perfusion abnormalities, trauma, and aberrant or repaired vasculature in the upper extremity. Applications to rotational and free tissue transfers include preoperative evaluation of both the donor and recipient vessels as well as postoperative monitoring.

Superior mesenteric artery syndrome in pediatric orthopedic patients.

Superior mesenteric artery (SMA) syndrome is a rare cause of small bowel obstruction in both adult and pediatric populations. Of 14 patients with the diagnosis from 1979 to 1987, eight had confirmatory upper gastrointestinal studies and were able to be followed for an average of 32 months. All eight were of similar age (range, 14.2 to 19 years), body build (asthenic), and clinical presentation. The presentation included nausea and intermittent, voluminous, bile-stained vomiting, despite intervening periods of normal appetite and bowel sounds. The average delay in diagnosis was five days. Nasogastric drainage and intravenous fluids were the mainstay of treatment and were successful in every case. Fifty percent of the patients had more than one episode requiring treatment; each episode resolved with simple treatment. Two of three patients with body casts required cast removal. No patient required intravenous hyperalimentation, removal of spinal instrumentation, or abdominal surgery to relieve the obstruction. Three of the eight patients had not had spinal surgery or cast immobilization.

Longitudinal observation of pediatric hand and wrist ganglia.

The purpose of this study was to examine the behavior of ganglia of the hand and wrist in young children treated without surgery. Fourteen consecutive children, less than 10 years of age, who presented with cysts of the hand and wrist were followed up by a single surgeon. The average age of the patient at the time of diagnosis was 38 months (range, 2 months to 9 years 3 months). The masses included 7 retinacular cysts, 5 volar wrist ganglia, and 2 dorsal wrist ganglia. These cysts had been present for an average of 3.3 months (range, 1-12 months) before medical advice was sought. None of the cysts were painful. Follow-up averaged 33 months (range, 9-112 months), with 79% of all cysts spontaneously resolving, the majority within a year. We believe that a child presenting with a benign hand lesion characteristic of a ganglion cyst should initially be treated by observation.

Upper extremity tourniquet tolerance.

Twenty unsedated volunteers were tested to compare the relative tolerance of an arm tourniquet on one side and of a forearm tourniquet on the other. The forearm tourniquet was tolerated an average of 13 minutes (45%) longer and was consistently rated as less painful during and immediately after the test. No subject tolerated the arm tourniquet longer than the forearm tourniquet. Two peaks of discomfort were found, one just before deflation beneath the tourniquet and one in the hand 2 minutes later. Ulnar nerve distribution paresthesias were the earliest changes experienced; however, complete numbness occurred first in the median nerve distribution. Complete paralysis occurred 7 minutes later (24%) with the forearm tourniquet. Pulse rate did not correlate with tourniquet pain, but blood pressure did. No measurable tourniquet-induced edema occurred on either side.

Subperiosteal ganglion of the distal radius: a case report.

We present an unusual case of a subperiosteal ganglion of the distal radius.

One-bone forearm fusion for pediatric supination contracture due to neurologic deficit.

The purpose of this study was to review the construction of a one-bone forearm performed to change the position of the forearm in children with fixed supination deformity due to upper extremity neurologic deficit. The one-bone forearm arthrodesis has been previously described in treating trauma, tumors, infection, and congenital deformities. It has not been described to improve forearm position in neurologically impaired upper extremities. We retrospectively evaluated 6 pediatric patients with upper extremity weakness and severe supination contracture who underwent forearm arthrodesis in neutral or slight pronation. Five patients achieved fusion, and 1 patient had an atrophic nonunion (17% nonunion rate). Average follow-up was 6 years 6 months (range 1 year 9 months to 11 years 2 months), and all patients were satisfied with their new forearm position.

Crack-growth properties of various elastomers with potential application in small joint prostheses.

Silastic small joint spacers for the metacarpophalangeal joint fail catastrophically at a reported rate ranging from 2 to 26%. Although the exact cause of this problem is not known, it is speculated that failure is due to the propagation of flaws generated in the material surface. In addition to wear secondary to bony impingement, these flaws can be introduced through manufacturing, surgical handling, and in vivo frictional wear. In an effort to identify an elastomeric material that will function similarly to Silastic as a self-hinging joint spacer but provide an increased functional life, we have investigated and compared the crack-growth properties of two polyurethanes, ChronoFlex and Medicaflex, and a thermoplastic elastomer, Santoprene, with those of Silastic. The materials were evaluated after sterilization by either ethylene oxide or gamma irradiation in an ASTM standard flexing machine under conditions of high humidity and body temperature both before and after artificially aging. In each case, the materials investigated presented significantly lower crack-growth rates than Silastic (p < 0.001).

External fixation of the distal radius: to predrill or not to predrill.

Using both clinical and laboratory studies we investigated whether predrilling before insertion of external fixation pins is necessary for use in treating distal radius fractures. Our clinical study included 50 consecutive external fixators (4.0- and 2.5-mm pins) using 100 predrilled and 100 direct-drilled pins placed in a randomized manner. There was no increased incidence of pin track infection or other pin problem with the direct-drilled technique. There were, however, significantly elevated temperatures with the direct-drilled technique. We therefore recommend predrilling even though the temperature differences in this bone with this fixator were not clinically evident.

Materials testing protocol for small joint prostheses.

In this article, a protocol for the evaluation of new materials for small joint prostheses is introduced. The testing methods employed in the protocol were developed by reviewing reported clinical failure modes and conditions found in vivo. The methods developed quantitatively evaluates the fatigue, fatigue crack propagation, and wear resistance properties of materials. For this study, a silicone elastomer similar to Dow Corning Silastic HP100, a radiation stable polypropylene, and a copolymer of polypropylene and ethylene propylene-diene monomer (EPDM) are evaluated. None of the materials tested demonstrated the ideal properties that are sought in a self-hinging joint prostheses. The silicone elastomer had excellent wear properties; however, cracks quickly propagated, causing catastrophic failure when fatigued. Conversely, the copolymer showed excellent fatigue crack propagation resistance and less than favorable wear properties. The polypropylene did not perform well in any evaluation.

Biomechanics of pulley reconstruction.

The biomechanics of the reconstructed flexor retinacular pulley system are poorly defined. We used a mathematical theoretical model, confirmed by a cadaver model, and a clinical radiographic model to evaluate a variety of different joint and pulley combinations. We examined twenty-four sets of radiographs of 12 fingers in 9 patients for whom excursion was measured and predicted by the mathematical model. The 30 pulley combinations evaluated in the in vitro cadaver model showed statistical correlation with the biomechanical mathematical model. Recommendations of clinical application on the basis of this information include the following: (1) Two pulleys should be placed, one proximal and one distal to each joint. (2) These two pulleys should be balanced about the joint axis both in distance from the axis and in pulley height. (3) They should be positioned at the edge of the flare of the metaphysis. (4) The three individual joints can be balanced, one to another, by maintaining minimal bowstringing at all three joints. In this way, the relative excursion at the joint and torque at the joint will be maintained in a physiological ratio as close to normal as possible.

Drug and alcohol use in emergency hand patients.

Two hundred eleven adult emergency hand patients were prospectively tested over a 1-year period for drug and alcohol use. On admission, blood and urine samples were sent for quantitative alcohol and qualitative toxicology screens, respectively. In 44% of all patients tests were positive for one or more drugs or alcohol. Tests were positive in 43% of those with traumatic injuries. Of patients injured on the job, 33% had positive tests. Tests were positive in 63% of those patients with hand infections. One third of the patients with positive toxicology screens were multiple drug users. These findings have obvious implications for the patient, the physician, and society as a whole.

Rapid onset of ulnar nerve dysfunction during transient occlusion of the brachial artery.

UNLABELLED: Perioperative ulnar neuropathy is a complication that occurs even in patients who seem to be appropriately padded and positioned. The disproportionately high incidence of postoperative ulnar nerve injury compared with the median and radial nerves has largely been attributed to its vulnerability to compression or stretch at the cubital tunnel. Some clinical and laboratory evidence suggests that compromise of perfusion to the upper extremity may also play a role in this complication. To determine whether the ulnar nerve is more sensitive to ischemia of the upper extremity, we studied 10 men during general anesthesia. Somatosensory evoked potentials of the radial, median, and ulnar nerves were simultaneously recorded during general anesthesia with the brachial artery occluded proximal to the cubital fossa. All three nerves showed rapid changes in signal amplitude in response to occlusion of the brachial artery, but the amplitude of the ulnar nerve was affected earlier and to a greater degree. Compared with the median nerve, the change in ulnar nerve signal amplitude during ischemia was significantly greater after 4 min (P = 0.002). This trend persisted at 6 and 8 min (P = 0.008). At 4, 6, and 8 min of ischemia, the ulnar nerve likewise showed a greater decrease in amplitude compared with the radial nerve, with corresponding P values of 0.015, 0.008, and 0.008. We conclude that the ulnar nerve is more sensitive to ischemia of the upper extremity compared with the radial and median nerves. In addition to its increased vulnerability at the elbow, compromise of arterial flow may contribute to some cases of postoperative ulnar neuropathy. IMPLICATIONS: Postoperative ulnar neuropathy is thought to result from compression or stretch of the ulnar nerve at the elbow. However, patients may sustain this complication despite careful padding and positioning. This study suggests that the ulnar nerve may also be unusually sensitive to decreases in blood supply to the arm. Care should not only to properly position and pad the elbows, but also to ensure adequate perfusion of the upper extremities.