Naveen N. Somia

The motion path of the digits

This study investigates whether the path taken by the fingertips of the human hand during unrestricted flexion and extension follows a precise mathematical pattern: an equiangular spiral. Eight normal subjects participated in the study. Subjects performed numerous flexion and extension trials at a random speed. Motion was recorded by a 6-camera, 3-dimensional motion analysis system with 24 retroreflective markers affixed to the dominant hand at predetermined locations. Four hundred eighty flexion-extension arcs were analyzed. We used the coefficient of multiple determination to compare the flexion and extension motion arc of each finger to an equiangular spiral curve derived mathematically. Our results indicate that the path of the hand during flexion and extension closely follows the path of an equiangular spiral with the coefficient of multiple determination values consistently above 0.95.

The initiation and sequence of digital joint motion: A three-dimensional motion analysis

We studied the initiation and sequence of digital joint motion during unrestricted flexion and extension using a 3-D motion analysis of all fingers moving simultaneously. Our results showed that motion started in a single joint in 83% of flexion and 80% of extension cycles. The DIP joint initiated flexion and extension in the index, middle, and ring fingers, but in the little finger, flexion started in the PIP joint, and extension in the MP joint. The two most frequent sequences of joint movement during flexion of the three radial fingers were DIP-PIP-MP and PIP-DIP-MP. The two most frequent sequences during extension of the three radial fingers were DIP-MP-PIP followed by DIP-MP/PIP. In the little finger, however, the most frequent sequences during flexion were PIP-DIP-MP followed by DIP-PIP-MP and during extension, DIP-MP/PIP followed by PIP/DIP-MP

A computer analysis of reflex eyelid motion in normal subjects and in facial neuropathy

OBJECTIVE To demonstrate how computerized eyelid motion analysis can quantify the human reflex blink. DESIGN Seventeen normal subjects and 10 patients with unilateral facial nerve paralysis were analyzed. BACKGROUND Eyelid closure is currently evaluated by systems primarily designed to assess lower/midfacial movements. The methods are subjective, difficult to reproduce, and measure only volitional closure. Reflex closure is responsible for eye hydration, and its evaluation demands dynamic analysis. METHODS A 60Hz video camera incorporated into a helmet was used to analyze blinking. Reflective markers on the forehead and eyelids allowed for the dynamic measurement of the reflex blink. Eyelid displacement, velocity and acceleration were calculated. The degree of synchrony between bilateral blinks was also determined. RESULTS This study demonstrates that video motion analysis can describe normal and altered eyelid motions in a quantifiable manner. CONCLUSIONS To our knowledge, this is the first study to measure dynamic reflex blinks. Eyelid closure may now be evaluated in kinematic terms. This technique could increase understanding of eyelid motion and permit more accurate evaluation of eyelid function. Dynamic eyelid evaluation has immediate applications in the treatment of facial palsy affecting the reflex blink. Relevance No method has been developed that objectively quantifies dynamic eyelid closure. Methods currently in use evaluate only volitional eyelid closure, and are based on direct and indirect observer assessments. These methods are subjective and are incapable of analyzing dynamic eyelid movements, which are critical to maintenance of corneal hydration and comfort. A system that quantifies eyelid kinematics can provide a functional analysis of blink disorders and an objective evaluation of their treatment(s).

Sequential segmental neuromuscular stimulation : an effective approach to enhance fatigue resistance

Electrical stimulation of skeletal muscle flaps is used clinically in applications that require contraction of muscle and force generation at the recipient site, for example, to assist a failing myocardium (cardiomyoplasty) or to reestablish urinary or fecal continence as a neo-sphincter (dynamic graciloplasty). A major problem in these applications (muscle fatigue) results from the nonphysiologic manner in which most of the fibers within the muscle are recruited in a single burst-like contraction. To circumvent this problem, current protocols call for the muscle to be put through a rigorous training regimen to transform it from a fatigue-prone to a fatigue-resistant state. This process takes several weeks during which, aside from becoming fatigue-resistant, the muscle loses power and contraction speed. This study tested the feasibility of electrically stimulating a muscle flap in a more physiologic way; namely, by stimulating different anatomical parts of the muscle sequentially rather than the entire muscle all at once. Sequential segmental neuromuscular stimulation (SSNS) allows parts of the muscle to rest while other parts are contracting. In a paired designed study in dogs (n = 7), the effects of SSNS on muscle fatigability and muscle blood perfusion in gracilis muscles were compared with conventional stimulation: SSNS on one side and whole muscle stimulation on the other. In SSNS, electrodes were implanted in the muscles in such a way that four separate segments of each muscle could be stimulated separately. Then, each segment was stimulated so that part of the muscle was always contracted while part was always resting. This type of stimulation permitted sequential yet continuous force generation. Muscles in both groups maintained an equal amount of continuous force. In SSNS muscles, separate segments were stimulated so that the duty cycle for any one segment was 25, 50, 75, or 100 percent, thus varying the amount of work and rest that any segment experienced at any one time. With duty cycles of 25, 50, and 75 percent, SSNS produced significantly (p < 0.01) enhanced resistance to fatigue. In addition, muscle perfusion was significantly (p < 0.01) increased in these sequentially stimulated muscles compared with the controls receiving whole muscle stimulation. It was concluded that SSNS reduces muscle fatigue and enhances muscle blood flow during stimulation. These findings suggest that using SSNS in clinical myoplasty procedures could obviate the need for prolonged training protocols and minimize problems associated with muscle training.

Purse-String Nipple Areolar Reconstruction

We present a surgical technique of nipple areolar reconstruction that uses a purse-string to increase areolar projection while reducing loss of nipple projection. A permanent purse-string is used around a modified CV flap to advance tissue centrally to the base of the nipple reconstruction. Two opposing hemiareolar island flaps are advanced toward the base of the nipple to add tissue volume. The resulting circumareolar full thickness skin is closed using a permanent purse-string suture. Synching the purse-string suture produces an effect similar to that of a periareolar mastopexy and enhances areolar projection. Eighty-two patients underwent 108 nipple areola reconstructions. Ninety-six percent of the patients achieved good results without any flap loss or suture infections. Revision surgery was necessary in 4 patients for minor problems including asymmetry or loss of projection. The purse-string nipple areolar reconstruction method described results in a high rate of maintenance of projection and patient satisfaction.

Sequential segmental neuromuscular stimulation reduces fatigue and improves perfusion in dynamic graciloplasty.

&NA; Dynamic graciloplasty is used as a treatment modality for total urinary incontinence caused by a paralyzed sphincter. A problem with this application is undesirable fatigue of the muscle caused by continuous electrical stimulation. Therefore, the neosphincter must be trained via a rigorous regimen to transform it from a fatigue‐prone state to a fatigue‐resistant state. To avoid or shorten this training period, the application of sequential segmental neuromuscular stimulation (SSNS) was examined. This form of stimulation proved previously to be highly effective in acutely reducing fatigue caused by electrical stimulation. The contractile function and perfusion of gracilis muscles employed as neosphincters were compared between conventional, singlechannel, continuous stimulation, and multichannel sequential stimulation in 8 dogs. The sequentially stimulated neosphincter proved to have an endurance 2.9 times longer (as measured by halftime to fatigue) than continuous stimulation and a better blood perfusion during stimulation (both of which were significant changes, p < 0.05). Clinically, this will not antiquate training of the muscle, but SSNS could reduce the need for long and rigorous training protocols, making dynamic graciloplasty more attractive as a method of treating urinary or fecal incontinence. Zonnevijlle EDH, Somia NN, Abadia GP, Stremel RW, Maldonado CJ, Werker PMN, Kon M, Barker JH. Sequential segmental neuromuscular stimulation reduces fatigue and improves perfusion in dynamic graciloplasty. Ann Plast Surg 2000;45:292‐297

Optimizing blepharoplasty outcomes in patients with previous laser vision correction.

Background: Dry eye syndrome, often referred to as dysfunctional tear syndrome, can occur following laser vision correction surgery and routine blepharoplasty. Identifying patients prone to developing or worsening of dysfunctional tear syndrome following blepharoplasty can help optimize surgical outcomes. Methods: The authors highlight the salient features of the dysfunctional tear syndrome including key steps in identifying at-risk patients. The authors discuss changes in the cornea that occur with keratorefractive surgery and their significance in patients seeking blepharoplasty. The authors suggest guidelines for blepharoplasty in these patients and discuss the timing of surgery. Results: After blepharoplasty, lagophthalmos of the upper lid is a common temporary finding. This change in eyelid function may unmask underlying deficiencies in the tear film or corneal sensation. Coexisting lower lid malposition can displace the existing tear meniscus and increase exposure of the cornea. Whether in combination or alone, these findings can create a dry eye problem. Dysfunctional tear syndrome should be considered in all patients with a history of laser vision correction during the preoperative evaluation for blepharoplasty. Surgeons should rely on preoperative history and physical examination, including assessment of preoperative eyelid anatomy and the status of the ocular surface. Patients with prior laser vision correction should wait at least 6 months before undergoing blepharoplasty because of the effects on corneal sensation, tear production, and tear film alteration. Conclusions: Identification and appropriate treatment of dysfunctional tear syndrome together with intraoperative modifications will optimize postoperative outcomes and avoid a potentially disabling condition after blepharoplasty in patients with previous laser vision correction surgery.

A technique for sequential segmental neuromuscular stimulation with closed loop feedback control.

In dynamic myoplasty, dysfunctional muscle is assisted or replaced with skeletal muscle from a donor site. Electrical stimulation is commonly used to train and animate the skeletal muscle to perform its new task. Due to simultaneous tetanic contractions of the entire myoplasty, muscles are deprived of perfusion and fatigue rapidly, causing long-term problems such as excessive scarring and muscle ischemia. Sequential stimulation contracts part of the muscle while other parts rest, thus significantly improving blood perfusion. However, the muscle still fatigues. In this article, we report a test of the feasibility of using closed-loop control to economize the contractions of the sequentially stimulated myoplasty. A simple stimulation algorithm was developed and tested on a sequentially stimulated neo-sphincter designed from a canine gracilis muscle. Pressure generated in the lumen of the myoplasty neo-sphincter was used as feedback to regulate the stimulation signal via three control parameters, thereby optimizing the performance of the myoplasty. Additionally, we investigated and compared the efficiency of amplitude and frequency modulation techniques. Closed-loop feedback enabled us to maintain target pressures within 10% deviation using amplitude modulation and optimized control parameters (correction frequency = 4 Hz, correction threshold = 4%, and transition time = 0.3 s). The large-scale stimulation/feedback setup was unfit for chronic experimentation, but can be used as a blueprint for a small-scale version to unveil the theoretical benefits of closed-loop control in chronic experimentation.

TRIGGERING CAUSED BY COMPLETE TRANSECTION OF ONE SLIP OF THE FLEXOR DIGITORUM SUPERFICIALIS TENDON: A CASE REPORT

Trigger finger was observed in a patient with a healed laceration at the palmar-digital crease of the left long finger. Examination revealed complete transection of the ulnar slip of the FDS tendon. The proximal ulnar slip was excised and the cut edge tapered, which restored a full range of motion without triggering.