Effects of the Short Foot Exercise With Neuromuscular Electrical Stimulation on Navicular Height in Flexible Flatfoot in Thailand: A Randomized Controlled Trial

OBJECTIVES

Flatfoot, or low medial longitudinal arch, contributes to back and lower extremity injuries and is caused by weak abductor hallucis (AbdH) muscles. The purpose of this study was to investigate the effects of short foot exercise (SFE) alone or with neuromuscular electrical stimulation (NMES) on navicular height, the cross-sectional area (CSA) of the AbdH muscle, and AbdH muscle activity in flexible flatfoot.

METHODS

Thirty-six otherwise healthy people with flexible flatfoot were randomly assigned to a group that received SFE with placebo NMES treatment (the control group) or a group that received both SFE and NMES treatment (the experimental group). Each group received 4 weeks of treatment (SFE alone or SFE with NMES). Navicular height, the CSA of the AbdH muscle, and AbdH muscle activity were assessed before and after the intervention.

RESULTS

No significant differences were found in navicular height or the CSA of the AbdH muscle between the control and experimental groups, while AbdH muscle activity showed a statistically significant difference between the groups (SFE=73.9±11.0% of maximal voluntary isometric contraction [MVIC]; SFE with NMES=81.4±8.3% of MVIC; p<0.05). Moreover, the CSA of the AbdH muscle showed a statistically significant increase after treatment in the SFE with NMES group (pre-treatment=218.6±53.2 mm2; post-treatment=256.9±70.5 mm2; p<0.05).

CONCLUSIONS

SFE with NMES was more effective than SFE alone in increasing AbdH muscle activity. Therefore, SFE with NMES should be recommended to correct or prevent abnormalities in people with flexible flatfoot by a physiotherapist or medical care team.

[Use of bisphosphonates in horses - a review]

Systemic administration of tiludronate or clodronate decreases lameness in some horses suffering from navicular syndrome within 2-6 months of treatment. In horses that fail to respond to the first treatment, a follow-up treatment may still improve the lameness. Horses with a lameness duration of less than 6 months have better odds of experiencing improvement in lameness. Bisphosphonate (BP) treatment can result in renal damage, and it is recommended to assess renal function prior to and after treatment. Horses with pre-existing renal compromise should not be treated with BP, as this may promote deterioration of their renal status. Furthermore, BP should not be administered concurrently with non-steroidal antiinflammatory medications or other nephrotoxic drugs. One of the most common side effects of BP treatment in the horse is development of colic signs, which usually resolves with hand walking. In cases where medical treatment is warranted, N-butylscopolamine, xylazine, detomidine or butorphanol should be administered alone or in combination. The treatment with non-steroidal antiinflammatory medications is not recommended. In horses with muscle fasciculations, plasma electrolyte concentrations should be determined. The route of administration for BP should follow manufacturer recommendations, as local applications such as intraarticular injections or administration via regional limb perfusion may not be safe and are thus currently not recommended.

[Outcome of accessory navicular fusion for the treatment of the painful accessory navicular bone of type II in adults]

OBJECTIVE

To evaluate the clinical outcome of accessory navicular fusion for treatment of the painful accessory navicular bone of type II in adults.

METHODS

From June 2006 to June 2012, a total of 38 feet (in 35 adult patients) with painful accessory navicular with type I underwent an fusion operation of the primary and accessory navicular bones,including 26 males and 9 females with a mean age of (32.4±7.3) years old ranging from 18 to 44 years old. The course of disease ranged from 3 to 10 months. The perioperative complications and radiological outcomes were observed and recorded. The foot function before and after operation were assessed by the American Orthopedic Foot and Ankle Society (AOFAS) midfoot score, and the easement of the pain was evaluated by visual analog score (VAS).

RESULTS

Two patients had transient superficial inflammation of the incision, no obvious perioperative complications occurred. All patients were follow-up for (53.5±14.7) months (12 to 84 months). Bone union was confirmed on plain radiography in 32 cases (35 feet). The mean time from the operation to union was (13.7±2.3) weeks (9 to 18 weeks). Postoperative pain VAS score was improved obviosly than preoperative (V=12.14,P< 0.01). The talar-to-first metatarsal angle [(9.4±3.5)° vs (8.3±2.7)°, t=0.736, P>0.05)], calcaneal tilt angle [(17.7±2.2)° vs (18.9±3.4)°, t=0.794, P>0.05],talonavicular uncoverage angle [(14.3±3.4)° vs(12.5?4.6)°,t=0.947, P>0.05) ],and height of the first tarsometatarsal joint [(14.8±3.1) mm vs (15.9±2.8) mm,t=0.814,P>0.05)] before and after operations had no statistic difference. The AOFAS midfoot score was improced from preoperative 45.6±5.3 to postoperative 82.5±7.4 (t=3.214,P< 0.01).

CONCLUSION

For the painful accessory navicular bone of type II in adults, if the patient has a large navicular bone and not complicated with rigid flatfoot, once the conservative treatment fails, fusion of the primary and accessory naviculars may be a successful intervention. Overall, the procedure provides reliable pain relief, definite foot function improvement, and good patient satisfaction.

Taking out the tarsal coalition was easy: but now the foot is even flatter. What now?

Patients with a preexisting hindfoot deformity, who undergo resection (with or without soft tissue interposition) of a tarsal coalition, may present with recurrent pain and worsening planovalgus deformity. This is due to the secondary effect of soft tissue contractures (lateral ligaments, peroneal tendons, calf muscles) "pulling" the foot into more valgus. Physiotherapy and insoles may help some patients. Depending on the flexibility of the hindfoot and the presence or otherwise of joint degeneration, joint-preserving corrective procedures or corrective joint fusions may be needed. Gastrocnemius, Achilles, and/or peroneal tendon releases may be required, to avoid equinus or further recurrence.

Acute fractures of the tarsal navicular

The tarsal navicular plays an integral role in hind-foot motion and gait, and is the keystone of the foot's medial longitudinal arch. As such, injuries to the navicular can be devastating. Acute avulsion, tuberosity, and body fractures have been described. Fractures of the body result from high-energy trauma and are often seen in conjunction with additional ipsilateral foot injuries. Plain radiographs are the gold standard for diagnosis, with computed tomography helpful in the presence of intra-articular fracture extension. Non-operative treatment is reserved for avulsion injuries and non-displaced body fractures. Open reduction and internal fixation must be performed for all other types, as failure to achieve an anatomic reduction can impede proper locomotion. Complications following operative intervention include pain, stiffness, posttraumatic arthritis, avascular necrosis, nonunion, and hindfoot deformity.

Ankle sprains and instability

Ankle injuries are among the most common injuries presenting to primary care providers and emergency departments and may cause considerable time lost to injury and long-term disability. Inversion injuries about the ankle involve about 25% of all injuries of the musculoskeletal system and 50% of all sports-related injuries. Medial-sided ankle sprains occur less frequently than those on the lateral side. High ankle sprains occur less frequently in the general population, but do occur commonly in collision sports. Providers should apply the Ottawa ankle rules when radiography is indicated and refer fractures and more severe injuries to orthopedic surgery as needed.

Peritalar destabilisation syndrome (adult flatfoot with degenerative glenopathy)

In cases of adult acquired flatfoot associated with peritalar destabilisation, special reference is made to the plantar calcaneo-navicular (spring) ligament's degenerative disease (degenerative glenopathy) and to the presence of the accessory navicular bone as a possible pathogenic cause. Peritalar destabilization syndrome is proposed for the articular (subtalar and talo-navicular joints) or tendinosis (tibialis posterior tendon) separately or in association with degenerative glenopathy of the coxa pedis. In degenerative glenopathy surgical reconstruction of the glenoid also makes use of a posterior tibial split to create a new tibial-navicular ligament. The concept of pronatory syndrome deemed as the root the pathological subtalar pronation, which is an entirely secondary factor in peritalar destabilisation, must be questioned. We must keep in mind that subtalar pronation and supination are respectively subsequent to opening and closing of the coxa pedis (talo-calcaneo-navicular joint) kinetic chain.

Relationship of foot conformation and force applied to the navicular bone of sound horses at the trot

REASONS FOR PERFORMING STUDY

Collapsed heels conformation has been implicated as causing radical biomechanical alterations, predisposing horses to navicular disease. However, the correlation between hoof conformation and the forces exerted on the navicular bone has not been documented.

HYPOTHESIS

The angle of the distal phalanx in relation to the ground is correlated to the degree of heel collapse and foot conformation is correlated to the compressive force exerted by the deep digital flexor tendon on the navicular bone.

METHODS

Thirty-one shod Irish Draught-cross type horses in routine work and farriery care were trotted over a forceplate, with 3-dimensional (3D) motion analysis system. A lateromedial radiograph of the right fore foot was obtained for each horse, and various measurements taken. Correlation coefficients were determined between hoof conformation measurements and between each of these and the force parameters at the beginning (15%) of stance phase, the middle of stance (50%) and at the beginning of breakover (86% of stance phase). Significance was defined as P<0.05.

RESULTS

The force exerted on the navicular bone was negatively correlated (P<0.05) to the angle of the distal phalanx to the ground and to the ratio between heel and toe height. This was attributed to a smaller extending moment at the distal interphalangeal joint. There was not a significant correlation between the angle of the distal phalanx and the degree of heel collapse, and heel collapse was not significantly correlated to any of the force parameters.

CONCLUSIONS

Hoof conformation has a marked correlation to the forces applied to the equine foot. Heel collapse, as defined by the change in heel angle in relation to toe angle, appears to be an inaccurate parameter. The forces applied on the foot are well correlated to the changes in the ratio of heel to toe heights and the angles of the distal phalanx.

POTENTIAL RELEVANCE

Assessment of hoof conformation should be judged based on these parameters, as they may have clinical significance, whereas parallelism of the heel and toe is of less importance.

[Treatment of syndesmosis diastasis with screw fixation in ankle fractures]

OBJECTIVE

To explore the operative method for the treatment of syndesmosis injury in ankle fractures.

METHODS

A retrospective study was done on 21 ankles of 20 patients included male 11 and female 9;the range of age were from 27 to 52 years with an average of 36 years) with syndesmosis injury in closed ankle fractures from September 2005 to December 2007. All patients with ankle fractures and syndesmosis injury were diagnosed by the history, physical examination and radiology, then treated with open reduction, internal fixation, and syndesmotic stabilization with a three-cortices syndesmotic screw according to the Lauge-Hansen classification system. Radiological evaluation comprised tibiofibular overlap, total clear space and medial clear space. The clinical effects were evaluated according to modified Baird-Jackson standard.

RESULTS

All patients were followed up from 1.0 to 2.2 years with an average of 1.3 years. Radiographic measurements were detailed as follows: tibiofibular overlap averaged (0.46 +/- 3.56) mm in preoperative and (7.14 +/- 0.62) mm in postoperative; mean total clear space (5.69 +/-0.88) mm in preoperative and (3.28 +/- 0.39) mm in postoperative; medial clear space averaged (5.67 +/- 1.23) mm in preoperative and (3.12 +/- 0.33) mm in postoperative; tibiofibular overlap in mortise view averaged (-0.87 +/- 0.96) mm in preoperative and (2.91 +/- 0.30) mm in postoperative. There was significant difference above data between preoperative and postoperative (P < 0.01). Four cases were confirmed minor tibiofibular diastasis through CT scans during postoperative. The modified Baird-Jackson scoring was from 62 to 98 scores with an average of (86.24 +/- 13.26) score at the final review. Of them, 13 ankles had not pain; 16 ankles reported no instability complaints; 11 ankles gained normal walking ability; 8 ankles could run normally; 11 ankles could return work without any restrictions. Activity of ankle in dorsiflexion, plantar flexion, inversion and eversion were respectively (21.05 +/- 5.00) degrees, (33.57 +/- 5.76) degrees, (19.48 +/- 4.57) degrees and (24.05 +/- 4.86) degrees. Three cases had radiological and clinical manifestations of osteoarthritis, but no breakage of syndesmotic screw in all cases. There were excellent results in 12 cases, good in 2, fair in 4, poor in 3.

CONCLUSION

The treatment for the syndesmosis diastasis with a three-cortices screw fixation in ankle fractures is effective. Good functional outcome can be obtained with anatomical restoration of the tibiofibular syndesmosis. The repair of deltoid ligament is important for stability of the lower tibiofibular syndesmosis. Removal of the screw before weight loading should be performed to avoid possible screw breakage.

A single-blind pilot study to determine risk and association between navicular drop, calcaneal eversion, and low back pain

OBJECTIVE

Syndromes causing mechanical low back pain (MLBP) continue to plague the US health care system. One hypothesis is that flatfeet are a risk factor for MLBP. This pilot study evaluated whether subjects with flatter feet are at greater risk for MLBP than subjects without flatter feet.

METHODS

Fifty-eight subjects (16-70 years old) were allocated to a group diagnosed with 2 or more episodes of MLBP or with no history of MLBP. A blind assessor measured navicular drop (ND) using navicular height (NH) and calcaneal eversion (CE). Based on a range of reported data, flatfoot was defined as a possible risk factor for MLBP with ND greater than 3, 8, and/or 10 mm, and/or greater than 6 degrees CE.

RESULTS

According to chi2 analysis, risk of MLBP appeared similar between groups (P > .05). There was no significant difference (P > .05) between continuous variables (t tests, Pearson r and r2) with one exception, correlation of increasing CE with increasing ND (P = .0001). Power was generally low (<0.80). Likelihood ratios and Fisher exact tests supported the chi2 analysis.

CONCLUSIONS

In this study, flatfeet did not appear to be a risk factor in subjects with MLBP. However, small sample size, low power, broader age range, low prevalence of flatfeet (>10 mm ND), and lesser back pain severity make these data tentative. Further research is needed.

Morphologic changes associated with functional adaptation of the navicular bone of horses

Failure of functional adaptation to protect the skeleton from damage is common and is often associated with targeted remodeling of bone microdamage. Horses provide a suitable model for studying loading-related skeletal disease because horses are physically active, their exercise is usually regulated, and adaptive failure of various skeletal sites is common. We performed a histologic study of the navicular bone of three groups of horses: (1) young racing Thoroughbreds (n = 10); (2) young unshod ponies (n = 10); and (3) older horses with navicular syndrome (n = 6). Navicular syndrome is a painful condition that is a common cause of lameness and is associated with extensive remodeling of the navicular bone; a sesamoid bone located within the hoof which articulates with the second and third phalanges dorsally. The following variables were quantified: volumetric bone mineral density; cortical thickness (Ct.Th); bone volume fraction, microcrack surface density; density of osteocytes and empty lacunae; and resorption space density. Birefringence of bone collagen was also determined using circularly polarized light microscopy and disruption of the lacunocanalicular network was examined using confocal microscopy. Remodeling of the navicular bone resulted in formation of transverse secondary osteons orientated in a lateral to medial direction; bone collagen was similarly orientated. In horses with navicular syndrome, remodeling often led to the formation of intracortical cysts and development of multiple tidemarks at the articular surface. These changes were associated with high microcrack surface density, low bone volume fraction, low density of osteocytes, and poor osteocyte connectivity. Empty lacunae were increased in Thoroughbreds. Resorption space density was not increased in horses with navicular syndrome. Taken together, these data suggest that the navicular bone may experience habitual bending across the sagittal plane. Consequences of cumulative cyclic loading in horses with navicular syndrome include arthritic degeneration of adjacent joints and adaptive failure of the navicular bone, with accumulation of microdamage and associated low bone mass, poor osteocyte connectivity, and low osteocyte density, but not formation of greater numbers of resorption spaces.

Return-to-activity levels in 96 athletes with stress fractures of the foot, ankle, and leg: a retrospective analysis

Stress fractures of the foot and ankle are common in the athletic population. Because this population is especially eager to return to activity, such fractures can be challenging to treat. If the biomechanical faults are not addressed or gradual return to activity is not monitored appropriately, fractures occasionally recur. A retrospective analysis was conducted of 96 athletes who presented to a podiatric sports medicine practice over the course of 10 years with stress fractures confirmed by radiograph or bone scan. The most common type of fracture sustained by this population was tibial stress fracture, followed by second metatarsal fracture. Marathon training was the most common pre-injury activity overall, although fitness walking was the most common activity among those with metatarsal fractures. This study relates the most common types of stress fractures of the foot, ankle, and leg to certain athletic activities and correlates duration of symptoms before presentation with return-to-activity time.

Drug resistant tuberculous osteomyelitis of small bones of foot

Drug resistant tubercular osteomyelitis of small bones of foot is not reported frequently. The case described here had isoniazid resistant tuberculous osteomyelitis of small bones of foot. The probable mechanism was endogenous reactivation of previously disseminated foci of drug resistant bacilli from the primary site in the lung.

Navicular drop measurement in people with rheumatoid arthritis: interrater and intrarater reliability

BACKGROUND AND PURPOSE

Navicular drop (ND) measurement may be a valuable examination technique for patients with rheumatoid arthritis (RA). However, no data exist on reliability for this technique in patients with RA. The purposes of this study were: (1) to determine interrater and intrarater reliability of ND measurements in people with RA, (2) to compare ND values of people with RA with published normative data, and (3) to investigate ND measurement error associated with the use of skin markings.

SUBJECTS

Ten women (20 feet) with RA consented to participate.

METHODS

Patients completed demographic and function questionnaires. Navicular height (NH) measurements were taken by 2 physical therapists and 1 physical therapist student, following four 1-hour training sessions, using standardized methods and a digital height gauge. Four different NH measurements were taken 3 times on each foot by each of the 3 examiners during a morning session and then repeated during an afternoon session on the same day. Navicular drop values were calculated, including ND1 (as reported in the literature), ND2 (compensating for skin error), and ND3 (single-limb stance). Intraclass correlation coefficients (ICCs) and standard errors of measurement (SEMs) were used to establish reliability.

RESULTS

Means (+/-SD) for each ND measure for sessions 1 and 2, respectively, were as follows: ND1=8.36+/-5.29 mm and 8.29+/-5.24 mm, ND2=9.95+/-5.44 mm and 9.57+/-5.37 mm. The ICCs (2,1 and 2,k, respectively) for all interrater measurements ranged from .67 to .92 (SEM=2.0-3.3 mm) and from .85 to .97 (SEM=1.1-2.0 mm). The ICCs (2,1 and 2,k, respectively) for intrarater measurements ranged from .73 to .95 (SEM=1.3-2.8 mm) and from .90 to .98 (SEM=0.7-1.6 mm). Paired t tests showed the means of ND1 and ND2 for each examiner and for both sessions were significantly different.

DISCUSSION AND CONCLUSION

The results suggest that ND measurements for people with RA can be taken reliably by clinicians with varied experience. The ND values for our subjects were slightly greater than reported normal values of 6 to 8 mm. Error associated with skin markings was statistically significant for all sessions and examiners.

Biomechanics of the first ray part V: The effect of equinus deformity. A 3-dimensional kinematic study on a cadaver model

The positional change of the medial column of the foot in closed kinetic chain with variable Achilles tendon tension was investigated in seven fresh frozen cadaver specimens using a 3-dimensional radio wave tracking system. The distal tibia and fibula and the intact ankle and foot and were mounted on a non-metallic loading frame. The frame allowed positioning of the foot to simulate midstance phase of gait while the tibia and fibula were axially loaded to 400 N. To record osseous motion, receiving transducers were attached to the first metatarsal, medial cuneiform, navicular, and talus. Movements of these bones in 3-dimensional space were measured as specimens were axially loaded and midstance motor function was simulated using pneumatic actuators. To simulate a progressive equinus influence, force was applied to the Achilles tendon at tensile loads of 0%, 30%, and 60% of predicted maximum strength during each test trial. Osseous positions and orientations were collected and analyzed in all three cardinal planes utilizing data recorded. As Achilles load increased, the position of the first metatarsal became significantly more inverted ( P < .05). Although not statistically significant, remarkable trends of arch flattening motion were detected in the distal segments of the medial column with varied Achilles load. Increased Achilles load reduced the influence of peroneus longus on the medial column.

Calcaneal lengthening: investigation of deformity correction in a cadaver flatfoot model

BACKGROUND

Evans showed that lengthening the lateral column by inserting structural bone graft into the anterior calcaneus could correct abduction and valgus deformity in flatfoot. To better understand the mechanism of correction and the three-dimensional effect of this procedure a cadaver study was done.

METHODS

Three cadaver flatfoot models were used. Computed tomographic (CT) scans were made of each specimen before and after lengthening. Data from these scans were used to determine the center of volume of the talus, navicular, cuboid, and calcaneus. The angular and translational motions for each bone were determined.

RESULTS

On average, relative to the talus, the navicular moved 18.6 degrees of rotation in adduction, 2.6 degrees of rotation in pronation, and 3.4 degrees in plantarflexion. The average translation was 5.6 mm medial, 0.4 mm posterior, and 1.8 mm plantar. The cuboid moved an average of 24.2 degrees of rotation in adduction and lengthening, 13.9 degrees in pronation, and 1.9 degrees in plantarflexion. The average translation was 9.4 mm medial, 2.6 mm distal, and 1.5 mm plantar. The calcaneus moved an average of 4.4 degrees of rotation in adduction, 0.1 degrees of rotation in eversion, and 1.3 degrees of plantarflexion. The average translation was 3 mm medial and 0.7 mm posterior with no plantar translation.

CONCLUSIONS

The mechanism of Evans calcaneal lengthening involves adduction and plantarflexion of the midfoot relative to the hindfoot. The cuboid and navicular appear to move as a unit. The shape of the talar head, axis of the subtalar joint, degree of initial deformity, competence of plantar soft tissues, such as the long plantar ligament, and adequate length of the Achilles tendon are important. Knowing what qualitative three-dimensional changes take place allows a better understanding of the mechanics of the procedure and its possible applications.

The effect of low-Dye taping on plantar pressures, during gait, in subjects with navicular drop exceeding 10 mm

STUDY DESIGN

A preintervention and postintervention, repeated-measures experimental design.

OBJECTIVES

To investigate the immediate effect of low-Dye taping on peak and mean plantar pressures during gait in subjects with navicular drop exceeding 10 mm.

BACKGROUND

Low-Dye taping is commonly used to support the longitudinal and transverse arches of the foot in an attempt to reduce the effects of symptoms associated with excessive pronation. Plantar pressure measurement has been used as an indirect indicator of pronation during gait. METHOD AND MEASURES: The right foot of 60 subjects was tested using the Emed-AT system to obtain plantar pressure values. Subjects performed 6 barefoot walks over the Emed pressure platform while taped and a further 6 walks while untaped. Plantar pressures were recorded. Each footprint obtained was divided into 10 sections or 'masks.' Average peak and mean plantar pressure values (N/cm2) were calculated for both taped and untaped walks for each mask.

RESULTS

Paired t tests demonstrated significant changes in peak plantar pressure in 8 of the 10 areas of the foot and significant changes in mean plantar pressure in 9 of the 10 areas of the foot. Low-Dye taping significantly decreased pressure under the heel and the medial and middle forefoot, while increasing pressure under the lateral midfoot and under the toes. A significant decrease in mean plantar pressure was observed under the lateral forefoot, while no significant difference was demonstrated in peak plantar pressure under this area. The area under the medial midfoot demonstrated no significant change in either peak or mean pressure.

CONCLUSIONS

Low-Dye taping significantly altered peak and mean plantar pressure values in subjects with navicular drop exceeding 10 mm. In particular, peak and mean plantar pressure increased under the lateral midfoot and under the toes, and decreased under the heel and forefoot, suggesting that a decrease in the amount of pronation occurred.

The accessory navicular

The accessory navicular is a common presence in the human foot and must be included in the differential diagnosis of medial foot pain in patients who are of appropriate age. Imaging modalities aid in diagnosis of a symptomatic ossicle and guide classification and treatment. Often, a combination of studies is needed to establish an accessory navicular as the source of foot pathology. Although conservative measures always are the first line of treatment, the benefits of surgical management are well-defined in the literature. Most foot surgeons rely on resection procedures with varied handling of the PTT insertion, although newer modifications that use bony fusion techniques are being investigated. As with any musculoskeletal condition, proper diagnosis and individually-tailored treatment plans are of the utmost importance to a satisfactory outcome. With meticulous patient selection and a thorough understanding of the condition, management of the painful accessory navicular often is successful in alleviating the disability it causes.

Müller-Weiss disease: clinical and biomechanical features

Müller-Weiss disease is a rare condition that is characterized by an odd deformation of the tarsal navicular, which may appears queezed and eventually fragmented between the talar head and the lateral cuneiforms. Because the head of the talus protrudes laterally, the subtalar joint remains in an inverted position. The plantar arch may correspond to that of a normal, cavus, or flat foot. The disease is not the consequence of a osteonecrotic process but results from impaired development of the bone, in most instances because of stressing environmental factors during childhood. Isolated cases that are due to individual predisposing factors are rare, although most of the patients can be grouped together as late collateral damage of war or poverty.

The effects of local anaesthetic solution in the navicular bursa of horses with lameness caused by distal interphalangeal joint pain

REASONS FOR PERFORMING STUDY

Analgesia of the palmar digital (PD) nerves has been demonstrated to cause analgesia of the distal interphalangeal (DIP) joint as well as the sole. Because the PD nerves lie in close proximity to the navicular bursa, we suspected that that analgesia of the navicular bursa would anaesthetise the PD nerves, which would result in analgesia of the DIP joint.

OBJECTIVES

To determine the response of horses with pain in the DIP joint to instillation of local anaesthetic solution into the navicular bursa.

METHODS

Lameness was induced in 6 horses by creating painful synovitis in the DIP joint of one forefoot by administering endotoxin into the joint. Horses were videorecorded while trotting, before and after induction of lameness, at three 10 min intervals after instilling 3.5 ml local anaesthetic solution into the navicular bursa and, finally, after instilling 6 ml solution into the DIP joint. Lameness scores were assigned by grading the videorecorded gaits subjectively.

RESULTS

At the 10 and -20 min observations, median lameness scores were not significantly different from those before administration of local anaesthetic solution into the navicular bursa (P > or = 0.05), although lameness scores of 3 of 6 horses improved during this period, and the 20 min observation scores tended toward significance (P = 0.07). At the 30 min observation, and after analgesia of the DIP joint, median lameness scores were significantly improved (P < or = 0.05).

CONCLUSIONS

These results indicate that pain arising from the DIP joint can probably be excluded as a cause of lameness, when lameness is attenuated within 10 mins by analgesia of the navicular bursa.

POTENTIAL RELEVANCE

Pain arising from the DIP joint cannot be excluded as a cause of lameness when lameness is attenuated after 20 mins after analgesia of the navicular bursa.

Bilateral Köhler's disease in identical twins

Köhler's disease is an uncommon idiopathic osteochondrosis of the tarsal navicular bone. The diagnosis is clinical and the natural history is benign. The treatment is symptomatic, including shoe supports when the symptoms are mild and initial cast immobilization for at least 8 weeks when the symptoms are more intense. The final clinical outcome is always favorable. This article reviews the development of bilateral Köhler's disease in identical twin brothers with simultaneous onset and parallel clinical course. Bilateral involvement in identical twins, to the authors' knowledge, has not been reported in the literature. Although this is a preliminary finding, it can imply that an unknown genetic predilection may exist and relate to the appearance of this rare disease.

[Pathologic anatomy of congenital clubfoot--review of the literature and personal observations]

The authors present a review of literature of the past 40 years, relevant to the pathological anatomy of congenital clubfoot and their own views--based on intra-operative observations. Performing Goldner's procedure the authors noted the talar bone was rotated internally, as a whole and externally in relation to the forefoot. The head and neck of the talar bone were deviated medially in relation to the trochlear axis. These deformities lead to pronation and supination movements instead of the normal flexion and extension of the foot. The authors believe a wide capsulotomy with resection of the ligaments is necessary to achieve proper clubfoot correction.

The association of hallux limitus with the accessory navicular

Hallux limitus is one of the most prevalent, debilitating disorders of the first metatarsophalangeal joint, and it has many proposed etiologies. This article reviews these etiologies, focusing primarily on the pes planus foot. The pes planus foot type is often associated with symptomatic hallux limitus and the accessory navicular. This article discusses this correlation, although a causal relationship has not been proven. The prevalence and classification of the accessory navicular are also discussed. Clinical cases involving symptomatic hallux limitus occurring concomitantly with an accessory navicular are reviewed, including radiographic findings, symptoms, and surgical treatment.

Plantar impact causing midfoot fractures result in higher forces in Chopart's joint than in the ankle joint

PURPOSE

Force effect (impact, extent of foot compartment deformation) and result (fracture pattern) for midfoot fractures in car occupants is known. An analysis of the processes in the foot was intended to improve car safety.

MATERIALS AND METHODS

Eleven fresh, unfrozen, unpreserved intact human cadavers (age: 36.8 (16-61) years, gender: male, race: Caucasian) were studied 24-72 h after death. In 3 cadavers (5 feet) the experimental design was established: entire cadaver fixed on a special tray in supine position, pendulum with bar impactor hitting the foot plantar to Lisfranc's joint. A custom-made pressure sensor was inserted in the ankle (A), talonavicular (TN) and calcaneocuboid (CC) joints (resolution: 1 cm2, sampling rate: 500/s).

RESULTS

Sixteen feet were measured: midfoot fractures were induced in 11 feet. The maximum pressure amounted to 1.22-2.55 MPa (2.04+/-0.412) at 0.005 0.195 s (0.067+/-0.059) after impact. The maximum pressure occurred in 8 (50%) cases in the ankle, in 7 (44%) of the TN and 1 (6%) of the CC joints. A comparison of the first 200 pressure samples after impact of all sensor fields resulted in higher forces in Chopart's joint than in the ankle (t-test: p < 0.001). These force differences were higher in cases with midfoot fractures (mixed model analysis of variance: p = 0.003).

CONCLUSION

Due to considerable forces in Chopart's joint we recommend a modification of the actual crash test dummy lower extremity model with an additional load cell that detects forces in the longitudinal direction of the foot axis.

Subjective and quantitative scintigraphic assessment of the equine foot and its relationship with foot pain

It was hypothesised that in solar bone images of the front feet of clinically normal horses, or horses with lameness unrelated to the front feet, there would be less than a 10% difference in the ratio of uptake of radiopharmaceutical in either the region of the navicular bone, or the region of insertion of the deep digital flexor tendon (DDFT), compared to the peripheral regions of the distal phalanx. Nuclear scintigraphic examination of the front feet of 15 Grand Prix show jumping horses, all of which were free from detectable lameness, was performed using dorsal, lateral and solar images. The results were compared with the examinations of 53 horses with primary foot pain, 21 with foot pain accompanying another more severe cause of lameness and 49 with lameness or poor performance unrelated to foot pain. None of the horses with foot pain had radiological changes compatible with navicular disease. All the images were evaluated subjectively. The solar views were assessed quantitatively using regions of interest around the navicular bone, the region of insertion of the deep digital flexor tendon and the toe, medial and lateral aspects of the distal phalanx. In 97% of the feet of normal showjumpers, there was <10% variance of uptake of the radiopharmaceutical in the navicular bone, the region of insertion of the DDFT and the peripheral regions of the distal phalanx. There was a significant difference in uptake of radiopharmaceutical in the region of the navicular bone in horses with foot pain compared to normal horses. There was a large incidence of false positive results related to the region of insertion of the DDFT. Lateral pool phase images appeared more sensitive in identifying potentially important DDFT lesions. There was a good correlation between a positive response to intra-articular analgesia of the distal interphalangeal joint and intrathecal analgesia of the navicular bursa and increased uptake of radiopharmaceutical in the region of the navicular bone in the horses with primary foot pain. It is concluded that quantitative scintigraphic assessment of bone phase images of the foot, in combination with local analgesic techniques, can be helpful in the identification of the potential source of pain causing lameness related to the foot, but false positive results can occur, especially in horses with low heel conformation.

Factors contributing to the development of medial tibial stress syndrome in high school runners

STUDY DESIGN

Predictive correlational study.

OBJECTIVES

To identify the incidence of medial tibial stress syndrome (MTSS) in a group of high school cross-country runners and to determine if a relationship exists between lower extremity structural measures and the incidence of MTSS.

BACKGROUND

Medial tibial stress syndrome is an overuse injury that occurs in long-distance runners. Literature exists that implicates structural deformity as a contributor to MTSS, but no studies have developed a predictive model.

METHODS AND MEASURES

We measured 125 high school cross-country runners for tibiofibular varum, resting calcaneal position during stance, and gastrocnemius length. Runners developing MTSS over an 8-week period were placed in the injured group (2 men, 13 women; age 15.3 years 1.0), and 21 randomly selected uninjured runners were placed in the uninjured group (13 men, 8 women; age 15.7 years +/-1.5). Navicular drop was measured for runners in both groups. Reliability of measures was determined using an intraclass correlation coefficient (ICC 3,1). Paired t tests were used to compare the injury and noninjury groups. A logistic regression analysis was used to establish if the descriptive data could accurately predict the development of MTSS.

RESULTS

Paired t tests showed a significant difference in navicular drop test measures between the injured (6.8 mm 3.7) and noninjured (3.6 mm 3.3) groups. Logistic regression analysis revealed navicular drop test measurements and sex correctly identified athletes who developed MTSS with 76% accuracy.

CONCLUSION

Our study supported the hypothesis that a pronatory foot type is related to MTSS. The combination of sex and navicular drop test measures provides an accurate prediction for the development of MTSS. Clinical measures that identify biomechanical risk factors for MTSS may allow prevention or early intervention.

Risk factors for recurrent stress fractures in athletes

Our aim was to identify factors predisposing athletes to multiple stress fractures, with the emphasis on biomechanical factors. Our hypothesis was that certain anatomic factors of the ankle are associated with risk of multiple stress fractures of the lower extremities in athletes. Thirty-one athletes (19 men and 12 women) with at least three separate stress fractures each, and a control group of 15 athletes without fractures completed a questionnaire focusing on putative risk factors for stress fractures, such as nutrition, training history, and hormonal history in women. Bone mineral density was measured by dual-energy x-ray absorptiometry in the lumbar spine and proximal femur. Biomechanical features such as foot structure, pronation and supination of the ankle, dorsiflexion of the ankle, forefoot varus and valgus, leg-length inequality, range of hip rotation, simple and choice reaction times, and balance in standing were measured. There was an average of 3.7 (range, 3 to 6) fractures in each athlete, totaling 114 fractures. The fracture site was the tibia or fibula in 70% of the fractures in men and the foot and ankle in 50% of the fractures in women. Most of the patients were runners (61%); the mean weekly running mileage was 117 km. Biomechanical factors associated with multiple stress fractures were high longitudinal arch of the foot, leg-length inequality, and excessive forefoot varus. Nearly half of the female patients (40%) reported menstrual irregularities. Runners with high weekly training mileage were found to be at risk of recurrent stress fractures of the lower extremities.

The relationship between excessive pronation as measured by navicular drop and isokinetic strength of the ankle musculature

EMG research has shown that excessive pronation affects the timing and magnitude of extrinsic muscle activity. This study was designed to investigate the relationship between excessive pronation and isokinetic strength of the ankle. The following measures were performed on 24 subjects (12 pronators, 12 normals) matched for gender and weight: 1) plantarflexion, dorsiflexion, inversion and eversion strength, both eccentrically and concentrically, determined by isokinetic peak torque at 30 degrees/sec; and 2) excessive pronation determined by navicular drop. Subjects with excessive pronation were found to have no difference in invertor strength, but decreased concentric plantarflexion strength when compared to normals. This finding agrees with biomechanical theory suggesting that a pronated foot is less rigid and generates less torque. Differences in strength ratios in excessive pronators were also observed and attributed to the decrease in plantarflexion strength.

Calcaneocuboid joint pressure after lateral column lengthening in a cadaveric planovalgus deformity model

The purpose of this study is twofold: first, to measure the joint contact pressure across the calcaneocuboid joint in a planovalgus deformity and compare the results to pressures measured in a normal foot; and second, to determine the change in pressure across the calcaneocuboid joint after an Evan's-type calcaneal lengthening osteotomy. The effect of this procedure on the calcaneocuboid joint was evaluated using seven cadaver feet to measure peak pressure across the calcaneocuboid joint under a constant load. Each foot was sectioned medially to reproduce a deformity consistent with an adult, acquired flatfoot. Each flatfoot deformity was then corrected using a ten-millimeter lateral column lengthening osteotomy. Joint pressures were measured in the normal foot, the created flatfoot and then in the corrected flatfoot. Peak pressures across the joint increased significantly from baseline in the flatfoot (p <0.05). However, the change in pressure from the flatfoot to the corrected foot was not significant, and in some cases peak pressures in the corrected foot were actually lower than in the flatfoot. These findings indicate that calcaneal lengthening through an Evan's osteotomy does not increase pressure across the calcaneocuboid joint beyond physiologic loads in the flatfoot.

Effect of antipronation tape and temporary orthotic on vertical navicular height before and after exercise

STUDY DESIGN

A randomized controlled, crossover, within-subjects study evaluating 2 antipronation treatments.

OBJECTIVES

To investigate the antipronation effect of 2 treatments designed to reduce abnormal pronation, and the effect of an exercise challenge on the treatments.

BACKGROUND

Control of abnormal pronation in order to ameliorate inappropriate stresses on injured soft tissues is frequently sought in the treatment of overuse injuries of the lower limb. Tape and temporary soft orthotics are used to control abnormal pronation. The effects of these treatments remain largely untested.

METHODS AND MEASURES

Fourteen subjects (age = 23.8 +/- 3.5 years) who had at least a 10-mm navicular drop were studied. The dependent variable was vertical navicular height. The two independent variables were the treatment conditions (temporary felt orthotics, augmented LowDye tape, and control) and the exercise challenge (0, 10, and 20 minutes of controlled jogging). The subjects' vertical navicular height was measured before and after the application of the treatment conditions, and then after 10 and 20 minutes of jogging.

RESULTS

Tape and orthotic treatments produced approximately a 19% and 14% increase in vertical navicular height, respectively, which were both significantly greater than the control condition (0%). The treatment effect, although significantly diminished following exercise challenge, remained superior to control (6.5% for orthotic and 3.5% for tape compared to -7.3% for control).

CONCLUSION

Antipronation tape and temporary orthotics help to control excessive foot pronation initially after application and following exercise. These treatments may be useful in the assessment and treatment of lower limb injuries that are associated with abnormal foot pronation.

The reliability and validity of a first ray measurement device

The need for measuring the mobility of the first ray has been identified. The purpose of this study was to test the reliability and validity of a device built to measure the relative vertical displacement of the first ray. Twenty fresh frozen cadaver feet were sampled (mean age of donor was 70+/-13 years). Dorsal mobility of the first ray was measured by device over three trials of repeated loading using 20 N, 35 N, 55 N and 85 N of force. Radiographs served as the criterion standard for validation of the device. Vertical displacement was measured from x-ray by a digitizing procedure that recorded movement of the first ray during loading. Reliability of the device assessed by intraclass correlation coefficients (ICC) was .98 with standard errors of the measurement calculated to be 0.35 mm. A correlation of agreement value of .97 was determined for the two methods of measurement. Analysis of variance testing found a significant interaction between force and method of measurement. Tukey post-hoc analysis found no difference (F<1.70) between the two methods of measuring first ray displacement in cadaver specimens when the force applied did not exceed 55 N. At 85 N of force (F = 10.05), unwanted movement of the second metatarsal caused the device to overestimate the amount of displacement that occurred specific to the first ray. This measure of first ray mobility should help clinicians and researchers to better investigate foot pathology resulting from faulty mechanics of the first ray.

Mechanics of tarsal disintegration and plantar ulcers in leprosy by stress analysis in three dimensional foot models

This paper describes three dimensional two arch models of feet of a normal subject and two leprosy subjects, one in the early stage and the other in the advanced stage of tarsal disintegration, used for analysis of skeletal and plantar soft tissue stresses by finite element technique using NISA software package. The model considered the foot geometry (obtained from X-rays), foot bone, cartilages, ligaments, important muscle forces and sole soft tissue. The stress analysis is carried out for the foot models simulating quasi-static walking phases of heel-strike, mid-stance and push-off. The analysis of the normal foot model shows that highest stresses occur at push-off over the dorsal central part of lateral and medial metatarsals and dorsal junction of calcaneus and cuboid and neck of talus. The skeletal stresses, in early state leprosy with muscle paralysis and in the advanced stage of tarsal distintegration (TD), are higher than those for the normal foot model, by 24% to 65% and 30% to 400%, respectively. The vertical stresses in the soft tissue at the foot-ground interface match well with experimentally measured foot pressures and for the normal and leprosy subjects they are the highest in the push-off phase. In the leprosy subject with advanced TD, the highest soft tissue stresses and shear stresses (about three times the normal value) occur in push-off phase in the scar tissue region. The difference in shear stresses between the sole and the adjacent soft tissue layer in the scar tissue for the same subject is about three times the normal value. It is concluded that the high bone stresses in leprosy may be responsible for tarsal distintegration when the bone mechanical strength decreases due to osteoporosis and the combined effect of high value of footsole vertical stresses, shear stresses and the relative shear stresses between two adjacent soft tissue layers may be responsible for plantar ulcers in the neuropathic leprosy feet.

Assessing sesamoid subluxation: how good is the AP radiograph?

Subluxation of the metatarsosesamoid joints frequently occurs with the development of hallux valgus deformity, and the restoration of a normal metatarsosesamoid articulation has been proposed as essential for achieving a biomechanically sound operative result. The position of the sesamoid bones on the AP radiograph is used often to assess the pre- and postoperative relationship between the hallucal sesamoids and the metatarsal sulci. We evaluated the validity of this approach. Thirty subjects with hallux valgus and 30 control subjects participated in this study by undergoing both AP and tangential weightbearing radiographs. The sesamoid station on the AP radiographs was compared with the position of the sesamoids on tangential radiographs, using a new continuous measure to estimate subluxation. In approximately half of the cases, we found a difference between the apparent sesamoid station on the AP radiograph and the true position on the tangential one. Increased metatarsal rotation was associated with misclassification of the sesamoid station on the AP radiograph. We conclude that the standard method for measuring the sesamoid station on the AP radiograph is not valid. Surgeons wishing to evaluate the metatarsosesamoid joint should obtain weightbearing tangential radiographs.

Gross, histological and histomorphometric features of the navicular bone and related structures in the horse

Forelimb navicular bones and associated soft tissues were collected from 3 groups of horses and subjected to pathological examinations. The groups consisted of 38 horses with clinical navicular disease (ND) and 2 control groups, with no history of forelimb lameness, consisting of 25 age-matched mature horses (A-MC) and 9 immature horses (IC). Histological and histomorphometric studies were performed on tissue samples from 10 ND, 10 A-MC and 5 IC horses. Gross changes seen only in ND horses included: full thickness defects in the palmar surface fibrocartilage, palmar cortex erosion, medullary lysis, flexor digitorum profundus tendon (FDPT) surface fibrillation, FDPT core lesions and adhesions between the FDPT and navicular bone. Palmar surface partial thickness fibrocartilage loss and distal border fragmentation were seen with a significantly greater incidence in ND than in A-MC and not observed in IC. Remodelling of the proximal border, FDPT surface colouration, palmar surface fibrocartilage colouration and proximal border entheseous bone were identified in ND and A-MC but not in IC. Mid-ridge synovial fossae and horizontal depressions in the palmar surface were identified in all groups. Histologically palmar fibrocartilage thinning and loss were associated with reduced palmar fibrocartilage cell density and chondrocyte cluster formation. Palmar fibrocartilage fibrillation, palmar cortical bone defects, fibromyxoid stromal change in the medulla, medullary pseudocyst formation and entheseous new bone formation were all seen in ND. The adjacent FDPT showed fibrillation, tag formation and degeneration of the dorsal surface. Necrotic foci were also present within the body of the tendon. Although not always present, medullary bone pseudocysts, separate mineralised foci and most changes on the dorsal surface of the FDPT were specific to ND. Bone histomorphometric parameters were compared among groups. Cross-sectional area reduced from the sagittal ridge to the medial and lateral margins of each navicular bone. IC navicular bones had a smaller subchondral area, subchondral bone volume and a greater osteoid volume than in the AC, indicating that these differences were age-related. In ND the medullary area was decreased but the trabecular bone volume increased. The palmar subchondral area was increased but contained bone with an increased porosity and osteoid volume. Changes occurred from the medial to the lateral margins of the bone in horses with ND indicating remodelling of the bony elements throughout the bone in ND. The histological and histomorphometric changes in the navicular bone and palmar fibrocartilage were considered similar of those found in articular hyaline cartilage and subchondral bone in osteoarthritis.

The treatment of Lisfranc injuries

Thirty-one patients with fracture-dislocations of the tarsometatarsal joint were examined to assess the functional end results after a mean follow-up of 2.9 years (range 20 to 56 months). Sixty-one percent were polytrauma patients; 39% suffered isolated fractures. Forty-five percent had associated lesions of the tarsal joint complex (Chopart and subtalar joint). According to the Baltimore Painful Foot Scoring System (PFS), 52% achieved an excellent or good result and 48% a fair or poor result. Of the four different treatment modalities, open reduction and temporary screw or K-wire fixation yielded the best results. The major determinants of acceptable results were the type of treatment, type of lesions, the quality of initial reduction and associated involvement of the tarsal joint complex. The extent of the initial injury was the determining factor in the development of late degenerative arthritis. Degenerative changes of the tarsal joint were seen in almost all cases (94%). Such changes were more frequent after temporary screw fixation but did not seem to influence the final results. An initial anatomical reduction did not guarantee excellent results but minimized the chance of late degenerative arthritis. Primary arthrodesis demonstrated no advantage in our series. Although partial arthrodesis may be necessary in severely comminuted joints, it cannot be routinely advocated and should be used as a salvage procedure.

Effects of anesthesia of the palmar digital nerves on kinematic gait analysis in horses with and without navicular disease

OBJECTIVE

To determine the effect of local anesthesia of the palmar digital nerves on forelimb kinematics in Quarter Horses with and without navicular disease.

ANIMALS

12 adult Quarter Horses; 5 clinically normal (sound) and 7 with navicular disease.

PROCEDURE

Kinematic measurements were made on adult horses trotting on a treadmill, before and after palmar digital nerve block (PDNB). Twenty-three displacement, joint angle, and temporal gait measurements of the right forelimb and head were made for 5 strides in each horse. Initial (before local anesthesia) right forelimb measurements were obtained after a left forelimb PDNB. Kinematic measurements were compared before and after PDNB of the right forelimb by multiple ANOVA with an alpha = 0.05, adjusted for posthoc comparisons by Bonferroni correction.

RESULTS

In sound horses, the only significant change in kinematic measurements after PDNB nerve block was in the maximum extension of the metacarpophalangeal joint at mid-stance, which was decreased by an angle of 2 degrees. In horses with navicular disease, mean maximum extension of the metacarpophalangeal joint during stance phase and maximum flexion of the carpal joint during swing phase were significantly increased after PDNB. Also, total stance phase, cranial stance phase, and break-over durations were significantly shorter. In horses with navicular disease, differences between minimum head heights during stance phase of each forelimb and total vertical head excursion during a complete stride were significantly smaller after PDNB.

CONCLUSION

Several kinematic measurements of gait can be used to determine improvement of lameness in horses with navicular disease after PDNB block while trotting on a treadmill.

[Muscular spasms associated with a reflex sympathetic dystrophy]

The appearance of involuntary movements in the clinical course of reflex sympathetic dystrophy (DSR) constitutes a rare clinical entity. In this context, the most frequent changes in movements are muscle spasms and focal dystonia, although postural tremor, muscle weakness and rhythmic myoclonus have also been described. The disorder is more frequent in young women and in the lower limbs. It may have a focal, segmental, multifocal, hemicorporal or symmetrical distribution. It is almost always secondary to local trauma. The pathogenesis and most effective treatment are unknown. We present the case of a 62 year old woman with muscle spasms of both legs and feet as a complication of spontaneously appearing DSR. The electromyogram showed continuous non-rhythmic discharges with morphologically normal motor unit potentials in both anterior tibial muscles. The clinical course and symptomatic improvement following treatment with benzodiazepine seems to suggest that the disorder is of central origin.

Radiographic assessment of the second metatarsal: measure of first ray hypermobility

Hypermobility of the first metatarsal cuneiform joint has been implicated as a cause of the hallux valgus deformity. The objective definition of hypermobility at this joint, however, has not been clearly defined. We used a modified Coleman block test to accentuate motion at the first metatarsal cuneiform joint in order to measure physiologic limits of motion in vivo. This motion was compared with radiographic analysis of the feet, which included the hallux valgus angle, intermetatarsal angle, and medial cortical thickening at the midshaft of the second metatarsal. This assessment was performed on 100 feet (50 right feet and 50 left feet in 50 patients). The average intermetatarsal angle was 8.7 degrees (range, 4-14 degrees), the average hallux valgus angle was 11 degrees (range, 4 degrees of varus to 30 degrees of valgus), and the average midshaft medial cortical thickness was 3.2 mm (range, 2.0-5.5 mm). Pearson's correlation coefficient was calculated to compare these factors. The relationship between variables was found to be small (r < or = 0.2). Motion was noted to occur in the normal foot at this joint and a range of normal values for medial cortical thickness was identified.

Talonavicular coalition. Objective gait analysis

Talonavicular coalitions, a rarely reported fusion between the talus and navicular, are often an incidental radiographic finding that may be asymptomatic or associated with peroneal spasm. The authors present a review of literature and case report based on clinical evaluation and instrumented gait analysis. Specifically, a patient presenting with a bilateral talonavicular coalition was objectively evaluated with kinetic, kinematic, muscle dynamometry, and pedobarographic testing to understand the biomechanical limitations related to this pathology. An excessive passive component of ankle torque, a high first metatarsophangeal joint plantar pressure, and a diminished time in the midstance portion of stance phase were measured and compared to those of healthy individuals.

[Stress fractures of the navicular bone--biomechanical and densitometry studies]

One of the most important pathogenetic mechanisms regarding stress fractures of the navicular bone lies in the hyperpronation movement of the foot. For recording the impacts of the pronation movement on the talonavicular joint, stress and pressure experiments are carried out and the radii of curvature as well as the bone density are measured. The stress experiments show a rotation movement of the talar head in a medioplantar direction of about 20 degrees. The radii of curvature of the articulating joint surfaces do not differ to a great extent. A possible incongruency in the joint therefore has to be attributed to the rotation movement of the talus during pronation of the foot. The pressure experiments show a very irregular distribution of pressure in the joint presenting a lateral and medial pressure maximum. Fractures preferably occur in the area in between these maxima. Areas of high subchondral bone density in the densitometric results are found in the central part of the talar head as well as in the medial part of the navicular bone. Within the functional adaptation the distribution of bone density expresses the rotation movement of the talus during pronation of the foot.

The influence of an ankle orthosis on the talar and calcaneal motions in chronic lateral instability of the ankle. A stereophotogrammetric analysis

The mechanical support provided by a semirigid ankle orthosis was tested in 14 ankles with symptoms of chronic lateral instability by use of stereophotogrammetric analysis. Talar and calcaneal rotations were measured with and without the Strong ankle orthosis during manual adduction test and adduction test with a predetermined torque (5 N-m). Significant reduction of talar and calcaneal plantar flexion, internal rotation, and varus angulation was noted when the orthosis was applied. The results of this study suggest that the semirigid orthosis may provide enough external support to prevent ankle sprains and to protect ligament reconstructions.

Intraosseous pressure and pathologic changes in horses with navicular disease

Navicular bone intraosseous pressure, gross pathologic, histologic, and histochemical data were collected from 8 horses with navicular disease and 4 control horses. Simultaneous navicular bone intraosseous, medial palmar arterial, and saphenous venous pressures were measured for the left and right forelimbs of each horse under general anesthesia. Gross pathologic evaluation included grading of changes on the flexor surface of the navicular bone. Safranin-O-fast green-stained sections were used for histologic-histochemical grading of the hyaline articular and fibrocartilage surfaces of the navicular bones. Hematoxylin and eosin-stained sections were used for morphologic evaluation of the marrow spaces of navicular bones. Mean navicular bone intraosseous pressure for horses with navicular disease was significantly (P < 0.001) higher than that for controls. Differences in medical palmar arterial or saphenous venous pressures were not significant between groups. The median flexor surface gross pathologic and histologic-histochemical fibrocartilage scores for horses with navicular disease were significantly (P < 0.001) more severe than those for control horses. The histologic-histochemical hyaline cartilage scores for control horses and those for horses with navicular disease were not significantly different. Fibrosis of the marrow spaces beneath the flexor cortex of horses with navicular disease was more pronounced than that of control horses.

Stress fractures of the tarsal navicular in long-distance runners

The authors report on a study that attempted to (1) determine anatomic variations that predispose runners to tarsal navicular stress fractures; (2) study that loading responses of runners with stress fractures and of uninjured runners; (3) study the mechanical factors and biomechanics of the foot during running; (4) define a population at risk for developing stress fractures; and (5) propose an alteration in footwear that may reduce the force across the talonavicular joint.