Biomedical subjects

L C Schon

Publications and source records attributed to L C Schon.

At least 37 records · Page 2Linked to original sources

PubMed1998

Tibiotalocalcaneal arthrodesis: anatomic and technical considerations.

In the first of this two-part cadaver investigation, we inserted a specially designed, pointed device (simulating a 12-mm nail) in an antegrade fashion in each of eight fresh-frozen cadaver tibial specimens; the tibial isthmus was used as a centralizing guide. The exit point was noted, and the specimen was dissected to identify the structures at risk. In all specimens, we found that the device placed the lateral plantar artery and nerve at risk (average minimal distance from device to structure, 0 mm) and that damage to the flexor hallucis brevis and plantar fascia occurred. In addition, in six of the eight specimens, the device skewered or skived the flexor hallucis longus tendon. We also noted that in each specimen the exit point was the sustentaculum tali, not the body of the calcaneus as expected. Thus, there was less calcaneal bone-to-rod interface for stability, and distal locking would be less effective in the lateral-to-medial direction because of the lack of medial bone stock. On the basis of the results of the first portion of the study, we investigated an alternative approach to retrograde tibial nailing to reduce the risk of injury to the plantar and medial structures of the foot. We performed a medial malleolar resection, medially displaced the talus, inserted the device in an antegrade fashion, and dissected the specimens to analyze the structures at risk. We found that malleolar resection and medial translation of the distal extremity an average of 9.3 mm (range, 7-11 mm) increased the average minimal distance from the tip of the device to the neurovascular bundle to 18.4 mm (range, 14-32 mm). We also found that there was no damage to the flexor hallucis longus and that all eight specimens demonstrated bony contact completely surrounding the nail device within the tuberosity portion of the calcaneus (assessed by postoperative radiographs). The results of this study suggest that malleolar resection and medial translation of the distal extremity before retrograde nailing of the tibia may reduce the risk of vital structure injury and enhance the rigidity of the fixation.

Arthrodesis↗

PubMed1998

Radiographic and clinical classification of acquired midtarsus deformities.

To develop a classification of midtarsus deformities, clinical examination and weightbearing radiographs were used to evaluate 131 feet in 109 patients (average age, 59+/-11 years) with those deformities. Patients were classified into four types based on anatomic location of the maximum deformity. Type I (N=43) showed deformity at the metatarsocuneiform joints medially and the fourth and fifth metatarsocuboid joints laterally, with plantarmedial and/or medial prominence. Type II (N= 60) had deformity at the naviculocuneiform joint medially and the fourth and fifth metatarsocuboid joints laterally; plantarlateral prominence was characteristic, although one-third had isolated or additional medial prominences. Type III (N=17) had major deformity in the perinavicular region, with a prominence plantarcentrally or plantarlaterally. Type IV (N=11) had deformity at the transverse tarsal joints with variable prominences. Each type was further subdivided into stages A, B, and C based on the severity of the deformity. In stage B, the midtarsus was coplanar with the metatarsocalcaneal plane. In stage A, the midtarsus was above this plane. In stage C, the midtarsus was below this plane. We concluded that midtarsus deformities can be classified as one of four types and one of three stages. Additional study is warranted to correlate this system with prognosis and treatment for this pathologic process.

Adult↗

PubMed1998

Midfoot fusion technique for neuroarthropathic feet: biomechanical analysis and rationale.

To test the hypothesis that a plate applied to the plantar (tension) side of the medial midfoot provides stronger fixation than midfoot fusion with screw fixation, we biomechanically compared the two constructs for midfoot fusion. We created a model of midfoot instability in eight matched pairs of cadaver legs by section of joint capsule, ligaments, and tendons about Lisfranc's joints, and then performed a load-to-failure study to compare the fixation provided by a plantarly applied third tubular plate with that by cortical screws. After an initial load deformation curve to 1000 N was obtained, specimens were cyclically loaded at 200 to 750 N for 3000 cycles and then loaded to failure (screw pullout, fracture, or deformation >3 mm). Comparing the plantar plate and midfoot fusion with screw fixation constructs, a plate applied to the plantar (tension) aspect of the medial midfoot provides a stronger, sturdier construct than does midfoot fusion with screw fixation.

Aged↗

PubMed1998

Histopathologic findings in autogenous saphenous vein graft wrapping for recurrent tarsal tunnel syndrome: a case report.

Autogenous saphenous vein graft wrapping of the tibial nerve has been described as an effective treatment option for failed tarsal tunnel decompression. Various theories have been proposed to explain how this method works, with little histologic evidence to date. A pathologic investigation of a sectioned nerve that had been previously wrapped provides some insight into these proposals.

Adult↗

PubMed1998

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.

Adolescent↗

PubMed1997

Clinical and radiographic outcome of revision surgery for failed triple arthrodesis.

Between 1987 and 1994, we treated 33 patients with surgical revision for failed triple arthrodesis, 28 (29 feet) of whom returned for final examination (mean, 4.4 years; range, 2-7 years). The average age of these 16 women and 12 men was 46 years (range, 14-69 years). Before the revision procedure, patients had undergone nonoperative therapies for an average of 3.7 years (range, 0.5-12 years) and an average of three foot operations (range, 1-6 operations) after the primary triple arthrodesis. All patients were managed with rigid internal fixation via cannulated screws and power staples. Calcaneal osteotomy and/or revision of the transverse tarsal arthrodesis via appropriate saw cuts and bone wedges were used. Iliac crest bone graft was added, when a bone block arthrodesis was required, for those patients with nonunion or ankle impingement. Arthrodesis was achieved in all 29 feet, although 4 patients (4 feet) (14%) required additional procedures for malunion (2 patients), deformity recurrence (1 patient), deep infection (1 patient), and skin graft (1 patient). Comparison of the average pre- (retrospective) and postoperative American Orthopaedic Foot and Ankle Society 94-point hindfoot and ankle scores showed a significant improvement: 31 points (range, 13-61 points) versus 59 points (range, 24-91 points), respectively (P < 0.05). On a scale of 0 to 10 points, average patient satisfaction was 7.8 points (range, 2-10 points). This study demonstrated a satisfactory improvement in patient outcome after surgical correction of failed triple arthrodesis. We conclude that such a revision, although complex, may be attempted to establish a plantigrade foot free of infection and able to wear shoes without and orthosis or brace.

Adolescent↗

PubMed1997

Salvage of pseudoarthrosis after tibiotalar arthrodesis.

We retrospectively reviewed the treatment of a selected group of 23 patients with pseudoarthrosis after ankle arthrodesis who underwent revision arthrodesis at an average of 1.7 years (range, 0.3-17.0 years) after the initial, unsuccessful procedure. Fourteen patients underwent isolated revision tibiotalar arthrodesis, and 9 had an additional hindfoot arthrodesis (7 tibiotalocalcaneal, 2 pantalar) performed at the time of the procedure. Rigid internal fixation with screws was performed when possible, and, in patients with poor bone quality, an external fixator was used. Autogenous bone grafting was used in 14 patients where bone loss was present. Twenty-one of 23 patients had successful union (average, 14 weeks; range, 6-48 weeks). Two patients underwent successful arthrodesis but had persistent pain from reflex sympathetic dystrophy. Overall, 19 of 23 patients were satisfied with the surgery. We conclude that revision arthrodesis for tibiotalar pseudoarthrosis is a worthwhile procedure.

Adult↗

PubMed1996

Lower extremity musculoskeletal problems in dancers.

Ankle and foot problems are extremely common in the high-performance dance population. To adequately evaluate and treat these problems, the physician must possess knowledge of how the physical demands of dance affect the performer's body. A routine evaluation of the dancer, involving a team of orthopedists, dance instructors, and physical therapists familiar with dance mechanics, has been developed to facilitate recognition of the abnormal mechanics responsible for injury. This technique can be useful in prevention and early diagnosis of injury, thus minimizing lost performance time.

Back↗

PubMed1996

Avascular necrosis of the talus treated by core decompression.

We reviewed 11 patients (17 ankles) who had had core decompression for symptomatic avascular necrosis of the talus before collapse. The Mazur grading system was used to assess function preoperatively and at final follow-up, and radiographs were graded according to the Ficat and Arlet (1980) classification modified for the ankle. At a mean follow-up of seven years (2 to 14) 14 ankles (82%) had an excellent or good outcome (Mazur scores > 80 points; pain scores > 40 points (41 to 50). The other three ankles required tibiotalar fusion at a mean of 13 months (5 to 20) after core decompression. We conclude that core decompression is a viable method of treatment for symptomatic avascular necrosis of the talus before collapse.

Adult↗

PubMed1995

Branches of the tibial nerve: anatomic variations.

Anatomic variations in tibial nerve branches may help explain discrepancies between clinical examination and electrophysiologic tests as to the location of neuronal lesions. Dissection of 20 cadaveric feet (10 pair) along the course of the tibial nerve and its branches confirmed that it bifurcates within 2 cm of the medio-malleolar-calcaneal axis in 90% (18/20) and that it gives off frequent small branches with its accompanying vascular structures. Unlike other studies, however, we found that 60% had multiple calcaneal branches off the tibial nerve and that 20% evidenced previously undescribed accessory innervation to the abductor hallucis muscle from other than the medial plantar nerve.

Foot↗

PubMed1995

Tendon transfer combined with calcaneal osteotomy for treatment of posterior tibial tendon insufficiency: a radiological investigation.

We present the radiographic results after flexor digitorum longus tendon transfer combined with a medial displacement calcaneal osteotomy for the treatment of posterior tibial tendon insufficiency. Eighteen patients with posterior tibial tendon insufficiency were reviewed from 12 to 26 months after surgery. The 15 women and 3 men had a mean age of 54 years (range, 38-72 years). The talar-first metatarsal and talonavicular coverage angles were measured before and after surgery on the anteroposterior weightbearing radiographs. The mean preoperative talar-first metatarsal and talonavicular coverage angles were 21 degrees (range, 3-45 degrees) and 34 degrees (range, 0-55 degrees), respectively. The mean postoperative values for these angles were 8.5 degrees (range, 0-35 degrees) and 21 degrees (range, -30-45 degrees), respectively. The mean talar-first metatarsal angle decreased from 21 degrees to 8.5 degrees, a mean improvement of 12.5 degrees, and the mean talonavicular coverage angle decreased from 34 degrees to 21 degrees, a mean improvement of 13 degrees. On the lateral weightbearing radiographs, the talar-first metatarsal angle and the distance from the medial cuneiform to the floor were measured before and after surgery. The mean preoperative values were -22 degrees (range, -10 to -40 degrees) and 9 mm (range, 1-19 mm), respectively. The mean postoperative values were -9 degrees (range, +5 to -25 degrees) and 16 mm (range, 10-28 mm), respectively. The mean talar-first metatarsal angle decreased from -22 to -9 degrees (a mean improvement of 13 degrees), and the distance from the medial cuneiform to the floor increased from 9 to 16 mm (a mean improvement of 7 mm). We conclude that the use of a combined medial displacement osteotomy of the calcaneus with a tendon transfer for treatment of posterior tibial tendon insufficiency may offset the inherent weakness of the flexor digitorum longus transfer by reducing the antagonistic deforming force of heel valgus.

Adult↗

PubMed1995

The management of neuroarthropathic fracture-dislocations in the diabetic patient.

Appropriate management for the diabetic patient with a fracture or sprain depends on recognition of "at-risk" factors. For patients with stable, minimally displaced injuries, conservative modalities (prolonged immobilization and non-weight-bearing) are sufficient. For patients with unstable or displaced fracture-dislocations, and whose general condition does not contraindicate surgery, open reduction and internal fixation, at times combined with external fixation, is recommended. Initial aggressive management can avoid or minimize the disastrous sequelae of a destructive neuroarthropathic process and can effect a biomechanically sound plantigrade, braceable, and shoeable lower extremity.

Adult↗

PubMed1994

Clinical results following revision tibial nerve release.

The results following revision tarsal tunnel release in 12 patients (13 feet), including three men and nine women aged 28 to 66 years, are presented. The indication for surgery was incapacitating focal pain, associated with paresthesias and hyperesthesias, refractory to nonoperative treatment modalities. Electrodiagnostic studies were abnormal in nine and normal in four cases. Revision surgery was performed a mean 3.5 years (range 1-10 years) after the initial tarsal tunnel release. Epineurolysis was performed in nine of the 13 cases where the nerve was encased in a scar. An insufficient previous distal release was identified in nine of the 13 cases. Wound infection occurred in two patients, one of whom ultimately underwent a below the knee amputation. With the exception of this patient, all patients were evaluated a mean 31 months (range 12-59 months) after the revision surgery. Three groups of patients were identified based on similarities in presentation, intraoperative findings, and clinical outcome. The first group (four feet), characterized by encasement of the tibial nerve in scar and an adequate distal release at the previous tarsal tunnel surgery, did poorly. The second group (five feet), with both scarring of the tibial nerve and an inadequate prior distal release, had somewhat mixed results, but overall were improved. The final group (four feet), who had no significant tibial nerve scarring but had had an inadequate prior distal release, did well. Clinical history and physical examination were more helpful than electrodiagnostic studies in determining the extent and location of the tibial nerve irritation following previous tarsal tunnel release surgery.

Activities of Daily Living↗

PubMed1994

Dance screen programs and development of dance clinics.

Dance movements can be stressful to the body, and the required extreme positions may place physiologic structures at risk for acute, subacute, or chronic injury. The authors designed a screening program, conducted by a team of physical therapists, orthopedists, and dance instructors, to evaluate dancers for musculoskeletal problems and to make recommendations that would improve movement compensation, strength, endurance, and mobility.

Ankle↗

PubMed1994

Nerve entrapment, neuropathy, and nerve dysfunction in athletes.

Nerve entrapment, neuropathy, and nerve dysfunction in the legs, ankles, and feet of athletes are not uncommon conditions. Frequently, the conditions are overlooked as the more obvious musculoskeletal injury draws the physician's attention. Typically, with conservative treatment, including an occasional injection of local anesthetic with and without corticosteroid, resolution is achieved. Rarely, symptoms are severe and diffuse enough to require administration of a tricyclic antidepressant medication to decrease the nerve irritability. In cases that fail to respond to conservative treatment and have well-localized neurologic findings, surgery may be indicated. During surgery, the nerve should be minimally manipulated. The surrounding veins, arteries, and fat should be relatively undisturbed. Critical to understanding and treating these problems is a thorough knowledge of the peripheral neuroanatomy.

Adult↗

PubMed1993

Foot and ankle problems in dancers.

Lower extremity problems, specifically in the feet and ankles, are common in dancers. This is not surprising considering the repetitive and acute stresses applied to lower limbs during this rigorous performing arts activity. When evaluating a dancer with lower extremity complaints, the nature of these demands must be appreciated. In addition to routine physical examination, static and dynamic biomechanical evaluation is paramount to analysis and treatment of leg, foot, and ankle conditions. Although a particular problem, such as painful bunion, may seem localized, it is often related to other factors, such as weak posterior tibial tendon, tight heel cords, or inadequate or forced turnout. It is incumbent on the physician to treat the specific area and, more importantly, to discover contributing factors that may be corrected by changes in technique or training. The physician caring for dancers should communicate with the instructor, physical therapist, or choreographer to facilitate the process. An overview of some common maladies and their characteristics findings are presented.

Ankle Injuries↗

PubMed1991

Reconstruction for subtalar instability: a review.

Instability of the subtalar joint has become a more well-defined clinical entity in recent years. While there have been several articles which have discussed diagnosis of this condition, there has been little written on the surgical treatment. Reconstructive techniques with which we have had experience are presented. Technical aspects of these methods are described in detail.

Humans↗

PubMed1990

Neuropathies of the foot and ankle in athletes.

Although neuropathies in the athlete's foot and ankle are uncommon, they are often underdiagnosed. This is primarily due to the complex interplay of factors that are required for their presentation. The most frequently encountered entrapment syndromes (in decreasing order) involve the interdigital nerves, first branch of the lateral plantar nerve, isolated medial or lateral plantar nerves, posterior tibial nerve, deep peroneal nerve, superficial peroneal nerve, sural nerve, and saphenous nerve. A thorough knowledge of peripheral nerve anatomy is essential in establishing the diagnosis. Roentgenograms may reveal bony abnormalities that are the diagnosis. Roentgenograms may reveal bony abnormalities that are commonly contributory. Electrodiagnostic tests may be normal because these dynamic syndromes often resolve at rest. In most cases, correction of underlying etiologies combined with rest, NSAIDs, and occasionally injections will allow resolution of the syndrome. Recalcitrant cases may require surgical decompression, which frequently provides satisfactory results.

Adult↗