Calcification of a hydrophilic acrylic intraocular lens: case report with laboratory analysis.

We analyzed a single-piece plate-type hydrophilic acrylic posterior chamber intraocular lens (IOL) that was explanted due to a progressive loss of vision, which occurred 6 years after uncomplicated phacoemulsification. Gross and light microscopy, as well as anterior segment optical coherence tomography (OCT) revealed granular deposits below the IOL surface. Light scattering, as measured with Scheimpflug photography and densitometry analyses was found to be increased; spectrophotometry demonstrated a decrease in the light transmittance of the explanted lens. The granular deposits within the IOL material were found to be composed of calcium by histochemical methods (alizarin red and Von Kossa stains). To our knowledge this is the only report of calcification of this IOL design.

Evidence of isometric function of the flexor hallucis longus muscle in normal gait.

Studying mechanics of the muscles spanning multiple joints provides insights into intersegmental dynamics and movement coordination. Multiarticular muscles are thought to function at "near-isometric" lengths to transfer mechanical energy between the adjacent body segments. Flexor hallucis longus (FHL) is a multiarticular flexor of the great toe; however, its potential isometric function has received little attention. We used a robotic loading apparatus to investigate FHL mechanics during simulated walking in cadaver feet, and hypothesized that physiological force transmission across the foot can occur with isometric FHL function. The extrinsic foot tendons, stripped of the muscle fibers, were connected to computer-controlled linear actuators. The FHL activity was controlled using force-feedback (FC) based upon electromyographic data from healthy subjects, and subsequently, isometric positional feedback (PC), maintaining the FHL myotendinous junction stationary during simulated walking. Tendon forces and excursions were recorded, as were the strains within the first metatarsal. Forces in the metatarsal and metatarsophalangeal joint were derived from these strains. The FHL tendon excursion under FC was 6.57+/-3.13mm. The forces generated in the FHL tendon, metatarsal and metatarsophalangeal joint with the FHL under isometric PC were not significantly different in pattern from FC. These observations provide evidence that physiological forces could be generated along the great toe with isometric FHL function. A length servo mechanism such as the stretch reflex could likely control the isometric FHL function during in vivo locomotion; this could have interesting implications regarding the conditions of impaired stretch reflex such as spastic paresis and peripheral neuropathies.

The injury risk associated with pes planus in athletes.

Despite the common prophylactic use of rigid orthotics in athletes with flat feet to prevent subsequent injury, there is little scientific data in the literature examining the relationship between pes planus and athletic injuries to the lower extremity. The current prospective study was undertaken to establish what relationship, if any, exists between foot morphology and subsequent lower extremity injury. A total of 196 subjects were enrolled in the study, of which 143 (73%) were male and 53 (27%) were female. Forty-two percent of the participants (83) engaged in contact sports. There were a total of 227 episodes of injury involving the lower extremity. Logistic regression using contact sports, gender, and all of the different foot contact areas that were measured at the beginning of the study was undertaken. Although gender and participation in contact sports was predictive of some lower extremity injuries, the existence of pes planus as measured by medial midfoot contact area as a percentage of total contact area was not a risk factor for any injury of the lower extremity. This study shows that in an athletic population that is representative of collegiate athletics, the existence of flat footedness does not predispose to subsequent lower extremity injury. The routine prophylactic use of orthotics in flat-footed athletes to prevent future injury may therefore not be justified based on the data available.

Foot and ankle injuries in motor vehicle accidents.

BACKGROUND: We studied foot and ankle (F/A) injuries that occurred in motor vehicle accidents treated in a Level 1 trauma center. METHODS: The records of F/A injuries of 2248 consecutive orthopedic patients were reviewed to find foot and ankle injuries. RESULTS: Pilon fractures were common. Motor Vehicle Accident (MVA) occupants with F/A injuries had a higher injury Severity Score than those without (17.9 vs. 11.6, p <. 001). MVA F/A injury risk was higher without restraint [relative risk ratio (rrr) 1.68, p <. 0032] than with restraint except for air bagged drivers who were similar to unrestrained drivers (rrr 1.18, p > .05, NS). CONCLUSION: Patients with F/A injuries may have serious associated injuries. Air bags may not protect feet.

Results of operative fixation of unstable ankle fractures in geriatric patients.

It is widely accepted that operative fixation of unstable ankle fractures yields predictably good outcomes in the general population. The current literature, however reports less acceptable results in the geriatric population age 65 years and older. The current study analyzes the outcome of the surgical treatment of unstable ankle fractures in patients at least 65 years old. Twenty three patient over 65 years old were surgically treated after sustaining 21 (91%) closed and 2 (9%) open grade II unstable ankle fractures. Fractures were classified according to the Danis-Weber and Lauge-Hansen schemes. Fracture type was predominantly Weber B (21/23, 91%), or supination external rotation stage IV (21/23, 91%). Fracture union rate was 100%. There were three significant complications including a lateral wound dehiscence with delayed fibular union in an open fracture dislocation, and two below knee amputations, neither of which was directly related to the fracture treatment. There were three minor complications; one superficial wound infection and two cases of prolonged incision drainage, all of which resolved without further surgical intervention. Complications were associated with open fractures and preexisting systemic disease. These results indicate that open reduction and internal fixation of unstable ankle fractures in geriatric patients is an efficacious treatment regime that with results that are comparable to the general population.

Diagnosing deltoid injury in ankle fractures: the gravity stress view.

In the lateral malleolar ankle fracture without talar shift there is much uncertainty regarding the diagnosis of deltoid ligament injury severe enough to require surgical treatment. The current study evaluated the mechanical integrity of the ankle using a novel gravity-stress mortise radiographic view, which is practical for clinical use. Eight cadaveric lower extremities were tested under the following conditions: (1) intact ankle, (2) distal fibular oblique osteotomy, (3) plated fibula after osteotomy, (4) transection of the superficial deltoid with fibula osteotomized or plated, and (5) all possible combinations of deep deltoid transection with superficial deltoid transected or repaired and fibula osteotomized or plated. For each condition, a mortise radiograph was taken of the specimen while it was mounted horizontally, lateral side down. Fibular osteotomy with or without transection of the superficial deltoid did not alter the mortise radiograph appearance of the ankles. With combined deep and superficial deltoid transection and fibular osteotomy, the talus always (eight of eight specimens) showed a lateral shift of 2 mm or greater and a valgus tilt of 15 degrees or more. The gravity stress view of the ankle was found to reproducibly document destabilizing deltoid ligament damage.

Intra-articular load distribution in the human ankle joint during motion.

The rational treatment of injuries to the ankle is predicated on an understanding of biomechanics of the ankle. While several investigators have reported on three-dimensional dynamic kinematics of the ankle and on the static distribution of pressure within the ankle, it has not been possible to measure intra-articular forces reliably under dynamic conditions. The assumption that the distribution of forces under dynamic conditions is well represented by statically determined forces has not been validated, leaving in question the applicability to dynamic conditions of data obtained under static conditions. This study characterizes an electro-mechanical thin-membrane force transducer with potential for intra-articular use. The sensor was found to yield a reproducible linear response to loads experienced in the ankle, and was insensitive to both a moist environment and shearing forces. On the basis of these results, these force-transducers were placed in axially loaded cadaveric ankles that were either statically or dynamically cycled through a physiologic range of motion. In each of six specimens, sensors were secured to the medial and lateral malleolar articular surfaces, and to articular surfaces of the medial and lateral tibial plafond. Both medial and lateral malleolar-talar forces increased with dorsiflexion. Moving from plantarflexion to dorsiflexion caused an increase in lateral tibio-talar load accompanied by a decrease in the medial tibio-talar loading. There was no significant hysteresis in force-distribution with respect to the direction of sagittal motion. There was no difference between the forces measured under static or dynamic conditions. This study validates the use of static loading methodologies in future studies of force-distribution. Our data in intact ankles closely corresponded to data on forces under dynamic conditions. Dorsiflexion caused an increase in both medially and laterally directed forces towards the malleoli. This is the first demonstration of such forces, which are responsible for the external rotation and lateral translation of the distal fibula that occurs in dorsiflexion of the ankle.

Tarsal coalition in adults.

32 feet in 27 adults, seen at The Johns Hopkins Hospital Foot and Ankle Clinic from 1993-1998, with the diagnosis of tarsal coalition were retrospectively reviewed. There were 18 subtalar coalitions, 14 calcaneonavicular coalitions and 1 naviculocuneiform coalition. The average age was 40 years. Clinically, 22 feet had a neutral heel, 7 had a valgus heel with flattening of the longitudinal arch, 1 had a varus heel and 2 heels had an unknown position. Subtalar motion was decreased in 23 feet. Peroneal spasm was only seen in 2 patients. 11 feet were asymptomatic. Nonoperative treatment consisting of activity modification, nonsteroidal anti-inflammatory medications and casting was successful in the majority of patients. Subtalar fusion was performed in 4 feet and coalition resection in 1. The treatment of a symptomatic tarsal coalition in the adult is as in children but the clinical presentation may differ.

Sensory thresholds of normal human feet.

HYPOTHESES/PURPOSE: Although several studies in the literature have evaluated the abnormal sensory thresholds of diabetic feet to Semmes-Weinstein monofilament testing, there is very limited data on the sensory thresholds of individuals without diabetes or peripheral neuropathy. The purpose of this study was to assess the dorsal and plantar sensation of the feet from 40 healthy, college-aged volunteers using Semmes-Weinstein monofilaments. CONCLUSIONS/SIGNIFICANCE: Semmes-Weinstein testing is a useful tool in predicting which diabetic patients may be at risk for ulceration of the feet. Several studies have determined 5.07 to be the threshold for protective sensation. Based on the normal values derived in this study, the inability to feel a Semmes-Weinstein monofilament of 5.07 (as in diabetic neuropathy) represents a sensory threshold that is more than 50 times greater than normal. This means that roughly 98% of the sensory ability has been lost. METHODS: 20 male and 20 female volunteers between the ages of 18 to 22 years old were selected. None had a history of any significant injury or previous surgery to the foot or ankle. There were no known medical conditions associated with decreased foot sensation, (e.g.- diabetes, syphilis, leprosy, myelomeningocele, syringomyelia, or hereditary neuropathy). Volunteers were also questioned regarding participation in athletic activities. The subjects were blindfolded with the leg resting comfortably on a chair as 14 plantar and 5 dorsal locations were tested on each foot. The right foot was always tested first. Each site on the foot had the Semmes-Weinstein monofilaments applied to it first, in an order of increasing stiffness, then repeated in decreasing order, using all twenty monofilaments in the set. A positive threshold response was recorded when the subject could feel the filament and could accurately locate where on the foot the stimulus had been applied. The left foot was then tested in an identical fashion. RESULTS: The mean sensitivity for all sites was 3.63 (0.0075 SEM). There were significant differences between sites, between using increasing or decreasing monofilament stiffness, between subjects, and in some instances, between right foot and left foot values. When testing was performed from the higher to lower monofilament stiffness, subjects were found to have significantly better sensitivity, which indicates the importance of a consistent testing protocol (either all up or all down). Sensation in the lesser toes and the arch were the most sensitive followed by the hallux and the plantar metatarsal heads. The least sensitive site was the heel, with 1/6th the sensitivity of the most sensitive toes.