Morphometric study of the equine navicular bone: variations with breeds and types of horse and influence of exercise. (1/103)

Navicular bones from the 4 limbs of 95 horses, classified in 9 categories, were studied. The anatomical bases were established for the morphometry of the navicular bone and its variations according to the category of horse, after corrections were made for front or rear limb, sex, weight, size and age. In ponies, navicular bone measurements were smallest for light ponies and regularly increased with body size, but in horses, navicular bone dimensions were smallest for the athletic halfbred, intermediate for draft horse, thoroughbreds and sedentary halfbreds and largest for heavy halfbreds. The athletic halfbred thus showed reduced bone dimensions when compared with other horse types. Navicular bones from 61 horses were studied histomorphometrically. Light horses and ponies possessed larger amounts of cancellous bone and less cortical bone. Draft horses and heavy ponies showed marked thickening of cortical bone with minimum intracortical porosity, and a decrease in marrow spaces associated with more trabecular bone. Two distinct zones were observed for the flexor surface cortex: an external zone composed mainly of poorly remodelled lamellar bone, disposed in a distoproximal oblique direction, and an internal zone composed mainly of secondary bone, with a lateromedial direction for haversian canals. Flexor cortex external zone tended to be smaller for heavy ponies than for the light ponies. It was the opposite for horses, with the largest amount of external zone registered for draft horses. In athletic horses, we observed an increase in the amount of cortical bone at the expense of cancellous bone which could be the result of reduced resorption and increased formation at the corticoendosteal junction. Cancellous bone was reduced for the athletic horses but the number of trabeculae and their specific surfaces were larger. Increased bone formation and reduced resorption could also account for these differences.  (+info)

Total dislocations of the navicular: are they ever isolated injuries? (2/103)

Isolated dislocations of the navicular are rare injuries; we present our experience of six cases in which the navicular was dislocated without fracture. All patients had complex injuries, with considerable disruption of the midfoot. Five patients had open reduction and stabilisation with Kirschner wires. One developed subluxation and deformity of the midfoot because of inadequate stabilisation of the lateral column, and there was one patient with ischaemic necrosis. We believe that the navicular cannot dislocate in isolation because of the rigid bony supports around it; there has to be significant disruption of both longitudinal columns of the foot. Most commonly, an abduction/pronation injury causes a midtarsal dislocation, and on spontaneous reduction the navicular may dislocate medially. This mechanism is similar to a perilunate dislocation. Stabilisation of both medial and lateral columns of the foot may sometimes be essential for isolated dislocations. In spite of our low incidence of ischaemic necrosis, there is always a likelihood of this complication.  (+info)

Does pulsed low intensity ultrasound allow early return to normal activities when treating stress fractures? A review of one tarsal navicular and eight tibial stress fractures. (3/103)

We sought to evaluate the efficacy of daily pulsed low intensity ultrasound (LIUS) with early return to activities for the treatment of lower extremity stress fractures. Eight patients (2 males, 6 females) with radiographic and bone scan confirmed tibial stress fractures participated in this study. Additionally, a case report of a tarsal navicular stress fracture is described. All patients except one were involved in athletics. Prior to the study, subjects completed a 5 question, 10 cm visual analog scale (VAS) regarding pain level (10 = extreme pain, 1 = no pain) and were assessed for functional performance. Subjects received 20-minute LIUS treatments 5 times a week for 4 weeks. Subjects maintained all functional activities during the treatment period. Seven patients with posterior-medial stress fractures participated without a brace. Subjects were re-tested after 4 weeks of treatment. Mann-Whitney U tests (VAS data) and paired t-tests (functional tests) assessed statistical significance (p<0.05). Although the intensity of practice was diminished in some instances, no time off from competitive sports was prescribed for the patients with the tibial stress fractures. The patient with the anterior tibial stress fracture underwent tibial intramedullary nailing at the conclusion of a season of play. In this uncontrolled experience, treatment of tibial stress fractures with daily pulsed LIUS was effective in pain relief and early return to vigorous activity without bracing for the patients with posterior-medial stress fractures.  (+info)

Combined cuboid/cuneiform osteotomy for correction of residual adductus deformity in idiopathic and secondary club feet. (4/103)

We used a combined cuboid/cuneiform osteotomy to treat residual adductus deformity in idiopathic and secondary club feet. The mean follow-up for 27 feet (22 idiopathic, four arthrogrypotic and one related to amniotic band syndrome) was 5.0 years (2.0 to 9.8). All healed uneventfully except for one early wound infection. No further surgery was required in the 22 idiopathic club feet but four of five with secondary deformity needed further surgery. At follow-up all patients with idiopathic and two with secondary club feet were free from pain and satisfied with the result. In the idiopathic feet, adductus of the forefoot, as measured by the calcaneal second metatarsal angle, improved on average from 20.7 +/- 2.0 degrees to 8.9 +/- 1.8 degrees (p < 0.05). In four feet, with a follow-up of more than six years, there was complete recurrence of the deformity. In the secondary club feet, there was no improvement of the adductus. We conclude that in most, but not all, idiopathic club feet a cuboid/cuneiform osteotomy can provide satisfactory correction of adductus deformity. Those with secondary deformity require other procedures.  (+info)

MRI study of talonavicular alignment in club foot. (5/103)

We studied in vivo the talonavicular alignment of club foot in infants using MRI. We examined 26 patients (36 feet) with congenital club foot. The mean age at examination was 9.0 months (4 to 12). All analyses used MRI of the earliest cartilaginous development of the tarsal bones in the transverse plane, rather than the ossific nucleus. The difference in the mean talar neck angle (44.0 +/- 8.1 degrees) in club foot was statistically significant (p < 0.001) when compared with that of the normal foot (30.8 +/- 5.5 degrees). The difference between the mean angles in the group treated by operation (47.9 +/- 6.7 degrees) and those treated conservatively (40.1 +/- 7.5 degrees) was also statistically significant. The anatomical relationship between the head of the talus and the navicular was divided into two patterns, based on the position of the mid-point of the navicular related to the long axis of the head. In the operative group, 18 feet were classified as having a medial shift of the navicular and none had a lateral shift. In the conservative group, 12 showed a medial shift of the navicular and six a lateral shift. All nine unaffected normal feet in which satisfactory MRI measurements were made showed a lateral shift of the navicular. Club feet had a larger talar neck angle and a more medially deviated navicular when compared with normal feet. This was more marked in the surgical group than in the conservative group.  (+info)

Origin of whales from early artiodactyls: hands and feet of Eocene Protocetidae from Pakistan. (6/103)

Partial skeletons of two new fossil whales, Artiocetus clavis and Rodhocetus balochistanensis, are among the oldest known protocetid archaeocetes. These came from early Lutetian age (47 million years ago) strata in eastern Balochistan Province, Pakistan. Both have an astragalus and cuboid in the ankle with characteristics diagnostic of artiodactyls; R. balochistanensis has virtually complete fore- and hind limbs. The new skeletons are important in augmenting the diversity of early Protocetidae, clarifying that Cetacea evolved from early Artiodactyla rather than Mesonychia and showing how early protocetids swam.  (+info)

Tarsal navicular stress fracture in a young athlete: case report with clinical, radiologic, and pathophysiologic correlations. (7/103)

BACKGROUND: Tarsal navicular fractures are uncommon but important causes of foot pain. Being alert to this condition can help prevent a delay in the diagnosis. METHODS: A literature search of MEDLINE was undertaken, and a case report of an adolescent with tarsal navicular stress fracture is described. RESULTS AND CONCLUSIONS: Tarsal navicular fractures are often misdiagnosed for months. Because plain radiographs are unreliable, the diagnosis of tarsal navicular fractures requires the use of bone scan, fine-cut computed tomographic scans, or magnetic resonance imaging. Treatment requires strict non-weight-bearing activities to avoid complications. When the alert primary care physician can diagnose this condition, treatment of tarsal navicular fractures can be effective and rewarding.  (+info)

Tarsal navicular stress fractures. (8/103)

Stress fractures of the tarsal navicular bone are being recognized with increasing frequency in physically active persons. Diagnosis is commonly delayed, and outcome often suffers because physicians lack familiarity with the condition. Navicular stress fractures typically present in a running athlete who has gradually increasing pain in the dorsal mid-foot with occasional radiation of pain down the medial arch. Because initial plain films are often normal, the next diagnostic test of choice is triple-phase bone scan, which is positive early in the process and localizes the lesion well. After a positive bone scan, a computed tomographic scan should be obtained to provide anatomic detail and guide therapy. Nondisplaced, noncomminuted fractures respond well to six weeks of non-weight-bearing cast immobilization. Displacement, comminution, and delayed or nonunion fractures are indications for surgical open reduction internal fixation.  (+info)