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Biomedical subjects

Lew C Schon

Publications and source records attributed to Lew C Schon.

31 records · Page 2Linked to original sources
PubMed2003

Arthrodesis of the fourth and fifth tarsometatarsal joints of the midfoot.

Maintaining mobility of the fourth and fifth tarsometatarsal joints has been reported to be important in arthrodesis of the midfoot. A review of the records at a tertiary care center of 23 patients (28 feet) with arthrodesis of these joints and a minimum 2-year follow-up showed that 22 complete midfoot arthrodeses were performed as part of the correction for a neuroarthropathic rocker-bottom deformity. Six arthrodeses of the fourth and fifth metatarsal joints were performed on normosensate feet with painful arthritis involving the lateral joints. Clinical and radiographic fusion occurred in 26 of 28 feet. Comparing average preoperative and postoperative scores, functional incapacity from lateral midfoot pathology decreased (8.4/10 to 2.2/10), overall pain scores improved (5.1/10 to 1.3/10), pain scores in the arthritic subgroup decreased (8.2/10 to 2.4/10), and the modified overall AOFAS midfoot score improved (35/100 to 78/100).

Aged↗
PubMed2003

Topography of the distal tibial nerve and its branches.

The tibial nerve trunk and its branches were dissected in 20 embalmed cadaver legs and the relative topographic anatomy was defined at 3-cm intervals up to 15 cm proximal to the medial malleolar-calcaneal (MMC) axis. Each nerve branch was found in various locations. The calcaneal nerve was found to descend from medial to posteromedial. It was never found anterolaterally and only rarely laterally. The lateral plantar nerve was found to rotate externally from lateral and posterolateral to lateral and posteromedial as it descends. This nerve was not found medially or anteromedially. The first branch of the lateral plantar nerve was indistinguishable from the trunk of the tibial nerve descending medially to between the lateral plantar and calcaneal nerves. The overall pattern of the medial plantar nerve was an internal rotation from anteromedial (proximal) to anterior (distally). It was not found posteriorly. The flexor hallucis longus motor branch was located an average of 17.9 cm (range, 10-24 cm) proximal to the MMC axis. Preliminary application of these data has facilitated surgical dissection and afforded an understanding of how tibial nerve trunk pathology correlates with clinical manifestations.

Cadaver↗
PubMed2003

Intramedullary rod fixation compared with blade-plate-and-screw fixation for tibiotalocalcaneal arthrodesis: a biomechanical investigation.

BACKGROUND: Achieving stable fixation when performing tibiotalocalcaneal arthrodesis can be challenging, especially in osteopenic bone. The purpose of the current investigation was to compare the stiffness and fatigue endurance of blade-plate-and-screw fixation with intramedullary rod fixation in a cadaveric model. METHODS: In ten matched pairs of fresh-frozen cadaveric legs, a tibiotalocalcaneal arthrodesis was performed with use of a blade-plate and a 6.5-mm sagittal screw in one leg and with use of an intramedullary rod in the contralateral leg. After an initial load-deformation curve was obtained, each specimen was loaded to 270 N through 250,000 cycles at a rate of 3 Hz. RESULTS: Blade-plate-and-screw fixation resulted in significantly higher mean initial and final stiffness and decreased plastic deformation than did intramedullary rod fixation. In addition, there was an inverse correlation between bone-mineral density and the difference in plastic deformation noted between the specimens of each pair. CONCLUSIONS: Blade-plate fixation is biomechanically superior to intramedullary fixation for tibiotalocalcaneal arthrodesis.

Analysis of Variance↗
PubMed2003

Controversies in amputation surgery.

Amputation surgery should be the first step in the rehabilitation of a patient with a nonfunctional limb, rather than the final step in treatment. When faced with a difficult decision regarding lower extremity amputation compared with attempted limb reconstruction, expectations for a reasonable outcome must be determined. After reasonable goals have been set, the surgery should be directed toward interfacing with a prosthetic limb. Current surgical techniques of lower extremity amputation, paying special attention to transosseous versus disarticulation amputation, help to optimize prosthetic limb fitting and functional rehabilitation. With the evolution of end-bearing amputation levels, there is resurgent interest in the bone bridging technique of Johann Ertl and interest in a new pneumatic immediate postoperative prosthetic limb fitting system.

Amputation, Surgical↗
PubMed2002

The acquired midtarsus deformity classification system--interobserver reliability and intraobserver reproducibility.

A radiographic classification (Schon's) divides Charcot midtarsus deformities into four types identified by Roman numerals (I to IV), according to the anatomical location of the pathological process,11 and an objective method of severity staging using radiographic criteria is introduced and tested. A beta stage is assigned if one of the following criteria is met: 1. a dislocation is present; 2. the lateral talar-first metatarsal angle is > or = 30 degrees; 3. the lateral calcaneal-fifth metatarsal angle > or = 0; or 4. the AP talar-first metatarsal angle is > or = 35 degrees. An alpha stage can be assigned when all four features are absent. Clinical features useful in assessing and managing these deformities have been associated with the various types and stages. To determine whether the classification system is valid, a study was performed. Two examination booklets and an instructional booklet designed to teach the method were distributed to 75 orthopaedic surgeons at the AOFAS summer meeting to test for intraobserver reproducibility and interobserver reliability. Information about the participants was recorded, and the tests were scored. The highest scores for correct responses were achieved by foot and ankle fellows, followed by orthopaedic residents. Attending orthopaedic surgeons achieved the lowest scores. The most common error was a type I deformity misidentified as a type II. The interobserver reliability for correctly classifying the deformities was 81%, and the intraobserver reproducibility was 97%. We concluded that this classification system, intended to clarify the patterns of acquired midfoot collapse, permits assignment of both anatomic type (I to IV) and degree of severity (alpha-beta) with high reliability and reproducibility. It can therefore be used as a tool for diagnosis, planning treatment, and assessing the prognosis.

Charcot-Marie-Tooth Disease↗
PubMed2002

Arthrodesis of the first metatarsophalangeal joint: a biomechanical study comparing memory compression staples, cannulated screws, and a dorsal plate.

Arthrodesis of the first metatarsophalangeal joint of 21 matched pairs of cadaver toes was performed in order to compare the strength of three methods of internal fixation: 1. two crossed cannulated screws, 2. a dorsal plate with an oblique 0.062 K-wire, and 3. two compression staples with an oblique 0.062 K-wire. Biomechanical testing with plantar force was carried out, and gapping across the fusion site was measured. Stiffness, load to 1-mm displacement, and force to failure was determined for each specimen. Both the plate and screw constructs were statistically stronger in force to failure and initial stiffness than the compression construct. Compression staples have an advantage in their ease of insertion and theoretical continuous compressive force across an arthrodesis site, but should be supplemented with a cast or other external immobilization until union is achieved.

Arthrodesis↗
PubMed2002

Two modifications of the Weil osteotomy: analysis on sawbone models.

Second metatarsal osteotomies (30 degrees angle to shaft) were performed in 40 sawbones with: 1. head shifted proximally 5 mm; 2. head shifted proximally 10 mm; 3. 5-mm slice resected and head shifted proximally 5 mm; or 4. 5-mm dorsally based wedge resected and head shifted proximally 5 mm. Bone slice resection resulted in shortening (16.4+/-1.7 mm) and mild plantar displacement of the head (3.5+/-0.8 mm). Bone wedge excision resulted in moderate shortening (7.8+/-0.9 mm) and essentially no plantar displacement of the head (0.8+/-1.4 mm).

Humans↗
PubMed2002

A biomechanical study of two postoperative prostheses for transtibial amputees: a custom-molded and a prefabricated adjustable pneumatic prosthesis.

We evaluated an adjustable pneumatic prefabricated prosthesis and a rigid custom-molded prosthesis for immediate postoperative use. Twelve transtibial amputations were performed on cadaver limbs. Differential variable reluctance transducers were placed subcutaneously across the wound edge medially and laterally. The limbs were then placed in either the pneumatic prosthesis (five limbs) or the rigid prosthesis (seven limbs). The specimens underwent static and cyclic loading to simulate weight bearing. The strain readings for static and cyclic loading were greater in the rigid prosthetic group. Only the mean medial strain measurement after cyclic loading was statistically significant. The results demonstrate that the pneumatic prosthesis places less strain across the wound than a rigid prosthesis.

Air↗
PubMed2002

Benefits of early prosthetic management of transtibial amputees: a prospective clinical study of a prefabricated prosthesis.

To evaluate the use of an immediate postoperative prosthesis (IPOP) for transtibial amputees, we compared patient outcomes from a prospective clinical study of 19 patients managed with an IPOP with those of a retrospective review of a matched historic control group of 23 patients managed with standard soft dressings. Data were analyzed with the Student's t-test, and significance was set at P = 0.05. The IPOP patients had no surgical revisions, whereas the patients with standard soft dressings had 11. This was a significant difference. IPOP patients also had significantly fewer postoperative complications and shorter times to custom prosthesis than did controls.

Accidental Falls↗
PubMed2002

Pedobarographic and musculoskeletal examination of collegiate dancers in relevé.

Twenty-one collegiate ballet pupils were evaluated via history/questionnaire, musculoskeletal assessment, and pedobarographs, focusing on factors (e.g., alignment of hip, knee, and foot) thought to affect the important and common second-position relevé in dance. In a blinded manner, three observers classified the pedobarographs (obtained by an independent examiner) according to force distribution through the foot. Most dancers bore weight through the toes and transmitted force on both the medial and central metatarsal heads, and some transmitted force through only one of these rays, but none transmitted force through the lateral ray alone. This analysis provides a baseline for future assessment of normal or abnormal dance maneuvers.

Adolescent↗
PubMed2002

Mechanical comparison of cyclic loading in five different first metatarsal shaft osteotomies.

The purposes of the current study were: 1. to analyze the relative fatigue endurance of five different first metatarsal shaft osteotomies (proximal crescentic, proximal chevron, Ludloff, Mau, and Scarf), as performed on sawbone models using the most common fixation techniques (part I); and 2. to compare the two more commonly used techniques (per part I results) in matched-pair cadaver specimens (part II). In part I, the proximal chevron and Mau osteotomies were significantly more stable (P < or = 0.005) than all other osteotomies except the Ludloff. In part II, there was no significant difference in fatigue endurance between the proximal chevron and Ludloff osteotomies.

Analysis of Variance↗
PubMedDate not supplied

Three-dimensional reconstruction of magnetic resonance images of a displaced flexor hallucis longus tendon in hallux valgus.

By using three-dimensional magnetic resonance image reconstruction, lateral displacement of the flexor hallucis longus tendon and sesamoid bones was made clearly visible in a living patient. This finding supports a biomechanical model related to disturbed muscle balance at the first metatarsophalangeal joint, which could play an important role in the pathogenesis of hallux valgus and metatarsus primus varus.

Computer Simulation↗