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.

Kinematics of a total arthroplasty of the ankle: comparison to normal ankle motion.

Although the concept of a total ankle arthroplasty has been advanced as a method for treating severe ankle arthritis, the clinical experience with all of the models developed has been discouraging. Both the constrained designs, which maximize joint contact area by restricting the available motion, and the unconstrained designs, which allow more normal motion at the expense of higher contact stresses, uniformly result in implant loosening, pain, and clinical failure in 2 to 7 years. This has led to the recommendation against the use of a total ankle arthroplasty except in very low-demand patients. Failure of ankle implants can be ascribed to either anatomic considerations (e.g.--the talus is too small to accommodate the stress transfers of a prosthesis), or mechanical etiologies. Abnormal 3-dimensional motion of the ankle following arthroplasty would fall into the latter category. This study examined the motion that occurs after implantation of an unconstrained-type total ankle arthroplasty. Using previously validated methodology, axially loaded ankle specimens were cycled through an arc of plantarflex/dorsiflexion while measuring the resulting coupled internal/external and varus/valgus rotations. The average coupled motions in prosthetic ankles were not significantly different than their intact controls. There was, however, a significantly increased amount of hysteresis (defined as the difference between the upper and lower pathways of coupled motion at any given sagittal position) that occurred as the ankle was dorsiflexed and plantar flexed. The increased hysteresis was seen in both the axial and coronal planes. This indicates that there was a greater permitted envelop of motion in the prosthetic ankles compared to normal ankles. It is hypothesized that this subtle change in ankle kinematics caused by the arthroplasty leads to abnormal stress transfer at the prosthesis-bone interface, thereby promoting early implant failure.

Psychogenic equinovarus: the importance of recognition and non-operative treatment.

Although the potential for musculoskeletal symptoms in hysteric conversion disorder was recognized by Sigmund Freud, reports of it in the orthopaedic literature have been limited to upper extremity manifestations. This study reports 3 cases which illustrate hysteric conversion presenting as primary foot and ankle complaints. Given its relative rarity, it is a diagnosis that is easy to miss. Clinical clues to its diagnosis and accepted methods of treatment are discussed. It is important to realize that this condition arises from an unconscious conflict and does not represent a voluntary falsification of symptoms. As such, confrontational treatment is not generally successful.

Defining flatfoot.

Pes planus is a term frequently used in describing flatfoot; however, no study has objectively defined flatfoot. We evaluated the single leg stance footprint of 40 feet in 21 people with no history of foot problems, using pressure-sensitive film and a Harris mat. The medial and lateral aspects of the forefoot, midfoot, and hindfoot were assessed. The midfoot was further analyzed by dividing the medial midfoot force by the total midfoot force. The mean medial midfoot force/total midfoot force was 11.1% (SD = 6.5%). Pes planus was defined as the medial midfoot force/total midfoot force > 24.0% (mean + 2 SD). A population associated with pes planus (124 feet in 63 patients with Marfan syndrome) was then evaluated in the same fashion. Although the mean medial midfoot force/total midfoot force was not statistically different (16.0%), a distinct group of patients (25%) had forces that were outside the range of normal midfoot forces.

Efficacy of three-phase bone scans in evaluating diabetic foot ulcers.

To evaluate the utility of bone scans in determining the treatment of diabetic patients with foot ulcers, a retrospective study was conducted. Medical records were reviewed for clinical signs of infection, laboratory data, and the radiologists' interpretations of imaging studies. During the study period, 34 bone scans were obtained by the treating physicians to evaluate diabetic foot ulcers. Among these, 22 of 34 bone scans were markedly confirmatory of being "consistent with osteomyelitis," 8 of 34 were moderately confirmatory ("indeterminate with regard to osteomyelitis"), and 4 of 34 were not confirmatory ("not consistent with osteomyelitis"). Of the 22 patients in the markedly confirmatory group, eight patients with clinical findings of uncontrolled infection or gangrene were treated with partial or complete amputation, whereas all others (14 patients) were treated with local wound care+/-intravenous antibiotics. Among the eight bone scans interpreted as indeterminate, three patients required partial or complete amputation, whereas the other five patients were managed with local wound care. Of the four patients with nonconfirmatory bone scans, two patients had evidence of dry gangrene and required amputation, whereas the other two patients did not have clinical evidence of infection or gangrene and were treated with local wound care. There was no significant difference in the amputation rate for patients with confirmatory, indeterminate, or nonconfirmatory bone scans for osteomyelitis (36%, 37%, and 50%, respectively) (P > 0.5). Therefore, the authors concluded that the ultimate treatment should be based on clinical indicators of the presence of uncontrolled infection or gangrene rather than on bone scan findings.

The foot in Marfan syndrome: clinical findings and weight-distribution patterns.

The feet of Marfan patients are typically described as pes planovalgus. We evaluated the single-leg-stance footprint of 124 feet in 63 patients with the Marfan syndrome by using pressure-sensitive film and a Harris mat. Forty feet in 21 people with no history of foot problems were evaluated as normal controls. The medial and lateral aspects of the fore-, mid-, and hindfoot were assessed. The midfoot was further analyzed by dividing the medial midfoot force by the total midfoot force. The mean medial midfoot force/total midfoot force (MM/TM) in the control population was 11.1% (SD, 6.5%). Pes planus was defined as the MM/TM force > 24.0% (mean + 2 SD). The mean MM/TM force in the Marfan group was not statistically different (16.0%) from controls. The distribution, however, revealed two distinct types of weight-bearing patterns. Of the Marfan group, 74.8% had medial forces within the standard distribution of the normal control population. Only 25.2% of the Marfan patients had forces that were outside the range of normal midfoot forces and were defined as pes planus. Analysis of the patient's ligamentous laxity and the foot function in the Marfan population revealed no statistically significant correlation to the type of weight-bearing pattern of the foot.

Effect of medial displacement calcaneal osteotomy on ankle kinematics in a cadaver model.

Although medial displacement calcaneal osteotomy has been advocated for treatment of acquired pes planus, no studies have determined the biomechanical consequences at the ankle of such a procedure. The present investigation examined the alteration in ankle motion that resulted from a medial sliding calcaneal osteotomy. In dorsiflexion, the ankle specimens were found to have altered internal rotation and varus alignment. At maximal dorsiflexion, there was a 76% increase in internal rotation (4.4 degrees +/- 2.5 degrees versus 2.5 degrees +/- 1.7 degrees for intact ankles, P < 0.0004) and an increase of 425% in varus (0.42 degrees +/- 0.56 degrees versus 0.08 degrees +/- 0.34 degrees for intact ankles, P < 0.003). There were no significant differences seen in plantar flexion. Based on these results, caution is advised in the indiscriminate use of medial sliding osteotomies, because this procedure may predispose the patient to premature ankle arthritis as a consequence of the altered ankle motions.

Thromboembolism after foot and ankle surgery. A multicenter study.

Thromboembolic disease presents a potentially fatal complication to patients undergoing orthopaedic surgery. Although the incidence after hip and knee surgery has been studied and documented, its incidence after surgery of the foot and ankle is unknown. For this reason, a prospective multicenter study was undertaken to identify patients with clinically evident thromboembolic disease to evaluate potential risk factors. Two thousand seven hundred thirty-three patients were evaluated for preoperative risk factors and postoperative thromboembolic events. There were six clinically significant thromboembolic events, including four nonfatal pulmonary emboli, after foot and ankle surgery. The incidence of deep vein thrombosis was six of 2733 (0.22%) and that of nonfatal pulmonary emboli was four of 2733 (0.15%). Factors found to correlate with an increased incidence of deep vein thrombosis were nonweightbearing status and immobilization after surgery. On the basis of these results, routine prophylaxis for thromboembolic disease after foot and ankle surgery probably is not warranted.

Nonsurgical treatment of monarticular nontraumatic synovitis of the second metatarsophalangeal joint.

Thirteen patients with second metatarsophalangeal joint synovitis in 14 feet were seen during 4.5 years for monarticular nontraumatic synovitis of the metatarsophalangeal joint. They were treated with a nonsurgical regimen of intra-articular corticosteroids, along with the modification of a regular laced shoe to provide a rockerbottom effect. Nine feet of 8 patients were available for follow-up at an average of 75 months. Seven feet were asymptomatic, with no recurrence. One patient with bilateral involvement continued with symptoms unchanged. There were no recurrences. The treatment was unsuccessful for one patient who underwent surgical synovectomy. The above regimen seems to satisfactorily resolve the symptoms in 70% of the patients treated.

Peroneal tendon bupivacaine injection: utility of concomitant injection of contrast material.

Twenty patients received the installation of contrast material into the peroneal tendons while local anesthetic was injected as a diagnostic test. In three patients (15%), communication with the ankle joint and subtalar joint was noted, as well as failure of the contrast to fill the distal tendon. Injection of local anesthetic into the peroneal tendons as a diagnostic measure, therefore, may not have 100% sensitivity of specificity. Simultaneous injection of contrast material can be used to alert the clinician to a lack of specificity of the anesthetic test injection.

Clinical safety and efficacy of calf tourniquets.

A clinical study was undertaken to ascertain the utility and complication rate of proximal calf tourniquet use for foot and ankle surgery. The surgical and clinical records of 446 patients undergoing foot and ankle surgery between March 1992 and December 1994 were examined for details pertaining to intraoperative tourniquet use and postoperative evidence of neurologic or vascular complications. All patients who had surgery performed under tourniquet control were included in the study. A total of 454 limbs were operated on: 8 patients underwent bilateral surgical procedures. The patients comprised 172 men and 274 women. The average age was 48.9 (+/-16.0 SD) years. Surgery was completed in one tourniquet period in 435 cases (95.8%) and in two periods of tourniquet inflation in 19 cases (4.2%). The average duration of tourniquet ischemia was 49.2 minutes (+/-30.7 SD) for one tourniquet period and 131.1 minutes (+/-46.0 SD) for two tourniquet periods. No postoperative compromise to either neurologic or vascular function was detected. Specifically, no alteration in peroneal nerve function was seen. We conclude that a calf tourniquet placed proximally with adequate cast padding is a safe and effective method to achieve a bloodless surgical field for foot and ankle surgery.

An axially loaded model of the ankle after pronation external rotation injury.

Using a testing apparatus that allows axial loading and displacement in the sagittal, axial, and coronal planes, 6 ankles were tested under experimental conditions intended to model the Lauge-Hansen pronation external rotation injury. All specimens were rotated through a continuous range of sagittal motion with the ankle under 300 N of axial load as the coupled motion of the ankle in the coronal and axial axes was recorded. Combinations of fibular osteotomy, disruption of the syndesmosis up to 6 cm above the plafond, and deltoid transection were tested to mimic Stages I to III of the pronation external rotation ankle fracture. The effects of stabilization of the fibula and syndesmosis also were examined. Neither fracture of the fibula 4 cm above the plafond nor disruption of the syndesmosis to 6.0 cm resulted in a significant change in coupled motion of the talus. When the superficial deltoid was sectioned, the ankle had increased external rotation in plantar flexion. When the deep deltoid was sectioned, the ankle dislocated in plantar flexion unless the fibula was stabilized. This prevented dislocation but failed to restore normal talar kinematics. This study found no biomechanical support for placement of a syndesmotic screw unless the medial side cannot be stabilized anatomically.

Osteonecrosis of the talus: treatment by hindfoot fusion.

The results were reviewed for 11 ankles (10 patients) that had been treated with various hindfoot arthrodeses because of symptomatic osteonecrosis of the talus. Follow-up averaged 6.5 years (range, 2-15 years). A functional assessment using a modified Mazur grading system was performed both before surgery and at final follow-up. Data were also collected on the duration of the procedure, intraoperative findings, and the patient's assessment of postoperative cosmesis (excellent, good, fair, or poor). Radiographs were analyzed to determine the interval from the procedure until bony union. Nine of the 11 arthrodeses (82%) fused with the primary procedure and achieved excellent Mazur ratings (mean, 86 points; range, 81-90 points). The average interval until radiographic fusion was 7 months (range, 4-13 months). All eight patients (nine fusions) with successful fusions graded their cosmetic outcomes as excellent or good. The average length of the procedure was 148 minutes (range, 130-300 minutes), compared with an average of 92 minutes (range, 62-151 minutes) for ankle arthrodeses performed by the same surgeons in rheumatoid or osteoarthritic ankles (P < 0.001) and 102 minutes (range, 75-164 minutes) from a report in the literature. Two of the procedures were complicated by nonunions secondary to infections. In one patient, after treatment by debridement and intravenous antibiotics, reinfection and chronic osteomyelitis developed with a subsequent below-knee amputation. The other patient was treated successfully with debridement, antibiotics, and subsequent revision arthrodesis, which fused solidly at 9 months with an excellent result. We conclude that hindfoot arthrodeses for osteonecrosis can be technically demanding, but, despite having a long time to bony union, they can have an excellent clinical outcome.