Biomedical subjects
R C Schenck
Publications and source records attributed to R C Schenck.
Successful revascularization of a partially avulsed foot in a 6-year-old child.
The foot of a 6-year-old child was revascularized successfully following an avulsion and partial amputation through the tibiotalar joint. Partial degloving had disrupted the anterior and posterior tibial arteries with resultant ischemia. We excised the entire damaged segment of the posterior tibial artery and performed a reverse saphenous vein graft, end-to-end reconstruction of the defect. Peroneal and tibial nerve function returned within 5 months. Four years later, the patient has regained full, painless range of motion and normal strength and sensibility with no evidence of premature growth plate closure or avascular necrosis of the talus.
Fractures of the hand.
In managing any fractures of the hand, the basic principles of fracture management are the same whether treatment is closed or open. They are 1. Accurate reduction and stabilization of the fracture 2. Elevation and edema control 3. Mobilization of the unaffected joints 4. Early range of motion of the injured digit or digits when healing processes permit. Special situations and injuries require amendments to the basic principles. Open fractures require early and thorough wound debridement. Early fixation and serial wound debridement to assure a proper environment for bone or skin grafting are essential in caring for these severe injuries (Figs. 13-15). Numerous fixation techniques ranging from simple plaster splints, K-wires, external fixators, and small plates and screws are available for fracture care. Fractures of the hand are very common injuries that demand early recognition and treatment. The majority of fractures can be treated with closed methods. Recognition of those injuries that require operative treatment and prompt attention to detail and surgical technique will prevent many of the complications associated with these frequently encountered problems.
The versatility of the gastrocnemius muscle flap.
The gastrocnemius muscle rotation flap is a utilitarian procedure for management of soft-tissue defects about the knee. Ten patients underwent medial gastrocnemius muscle rotation flaps at our institution during a 24-month period. Four of the 10 patients underwent primary muscle rotation-plasty for reconstruction following tumor resection; 3 patients had soft-tissue defects following trauma; 2 patients had skin ischemia following total knee arthroplasty; and 1 patient had a soft-tissue defect from scar formation. All procedures were performed by an orthopaedic surgeon. At follow-up of 6 to 24 months, the soft-tissue coverage was maintained in all patients. All of the muscle rotation flaps survived. The gastrocnemius rotation flap provides reliable anterior knee soft-tissue coverage and can be performed by most orthopaedic surgeons.
A biomechanical analysis of articular cartilage of the human elbow and a potential relationship to osteochondritis dissecans.
A cadaveric study of the articular surfaces of the radiocapitellar joint was undertaken to identify a biomechanical mechanism of osteochondritis dissecans of the humeral capitellum. The articulating radial head and capitellum of fresh anatomic specimens were dissected and tested for intrinsic mechanical properties. Significant differences exist in the mechanical properties and thickness of cartilage topographically in the capitellum and radial head, and between the two surfaces. The medial portion of the radial head is the softest of all radiocapitellar osteochondral segments tested. Comparing medial to lateral sites of the capitellum, there is a trend of decreased stiffness; lateral segments are softer than medial ones. The central section of the radial head is significantly stiffer than the lateral capitellum. There is no significant difference between the stiffness of the radial head sites and the medial capitellum. The disparity in the mechanical properties of the central radial head and lateral capitellum would increase strain in the lateral capitellum. During high-valgus stress activities such as throwing, this increased strain may be a factor in the initiation and localization of the dissecans lesion observed in osteochondritis dissecans of the elbow.
Immediate vascular and ligamentous repair in a closed knee dislocation: case report.
Traumatic dislocation of the knee is a significant injury, and concomitant neurovascular injury generally occurs in greater than one in three cases reported. This paper describes a patient with multiple injuries who sustained a traumatic knee dislocation with vascular compromise. Initial treatment included a vein graft of the arterial injury and reconstruction and reattachment of injured ligaments at the same time as joint stabilization with a Steinmann pin. If arterial injury is present it must be repaired first.
Pseudothrombophlebitis in an adolescent without rheumatic disease. A case report.
Pseudothrombophlebitis syndrome is the occurrence of calf pain and swelling caused by extrinsic compression of the popliteal vessels by an enlarging Baker's cyst or by calf inflammation that occurs as the result of a ruptured Baker's cyst. Few cases of pseudothrombophlebitis syndrome have been reported in patients less than 18 years of age, and nearly all these young patients had juvenile rheumatoid arthritis. Reported here is the case of a 17-year-old male patient without rheumatic disease who presented to the outpatient clinic with a 1-week history of an increasingly painful swelling of the right calf without any history of precipitating factors for a deep vein thrombosis.
The incomplete bicruciate knee injury. A report of two cases.
Two patients suffered similar knee injuries due to valgus stress and hyperextension. Examination under anesthesia and arthroscopic evaluation revealed a previously unreported ligament injury pattern. Both patients had a complete tear of the anterior cruciate ligament and a partial tear of the posterior cruciate ligament; neither was noted to have a dislocation. The descriptive term identifying this injury pattern is "incomplete bicruciate knee injury." The purpose of this report is to identify this knee-injury complex, which appears to be part of the sequence that leads to complete tears of both cruciate ligaments--the classic knee dislocation.
Peroneal nerve palsy after early cast application for femoral fractures in children.
The incidence and contributing factors associated with post-casting peroneal nerve palsy were examined in a series of 110 consecutive pediatric femoral shaft fractures treated with early hip spica cast application. Four patients with peroneal nerve palsy were identified. All four had 90 degrees/90 degrees casts placed and underwent cast wedging for alignment. All palsies resolved with immediate cast removal. Other treatment options for certain femur fractures with significant initial shortening should be considered. We advise pre- and post-cast neurologic examination and avoidance of forceful distraction. Fracture manipulation, through wedging, should be delayed.
Biomechanical topography of human ankle cartilage.
The material properties of normal cadaveric human cartilage in the ankle mortice (tibiotalar articulation) were evaluated to determine a possible etiologic mechanism of cartilage injury of the ankle when an obvious traumatic episode is not present. Using an automated indentation apparatus and the biphasic creep indentation methodology, creep indentation experiments were performed in five sites in the distal tibia, one site in the distal fibula, and eight sites in the proximal talus of 14 human ankles (seven pairs). Results showed significant differences in the mechanical properties of specific human ankle cartilage regions. Topographically, tibial cartilage is stiffer (1.19 MPa) than talar cartilage (1.06 MPa). Cartilage in the anterior medial portion of the tibia has the largest aggregate modulus (HA = 1.34 MPa), whereas the softest tissue was found to be in the posterior lateral (0.92 MPa) and the posterior medial (0.92 MPa) regions of the talus. The posterior lateral ridge of the talus was the thickest (1.45 mm) and the distal fibula was the thinnest (0.95 mm) articular cartilage. The largest Poisson's ratio was found in the distal fibula (0.08). The lowest and highest permeability were found in the anterior lateral regions of the astragalus (0.80 x 10(-15) m4N-1sec-1) and the posterior medial region of the tibia (1.79 x 10(-15) m4N-1sec-1), respectively. The anterior and posterior regions of the lateral and medial sites of the tibia were found to be 18-37% stiffer than the anatomically corresponding sites in the talus. The biomechanical results may explain clinically observed talar dome osteochondral lesions when no obvious traumatic event is present. Cartilage lesions in a repetitive overuse process in the ankle joint may be related to a disparity of mechanical properties between the articulating surfaces of the tibial and talar regions.
Human articular cartilage biomechanics of the second metatarsal intermediate cuneiform joint.
Intrinsic material properties and histomorphometry of freshly frozen, human cadaveric cartilage from the second metatarsal intermediate cuneiform (SMIC) articulation were obtained to provide biomechanical mapping of the surfaces. The biphasic creep indentation methodology and an automated creep indentation apparatus were used to measure aggregate modulus, Poisson's ratio, permeability, shear modulus, and thickness. Biomechanical experiments were performed on four sites of the SMIC joint in 14 specimens (seven pairs): two sites in the second metatarsal base and two sites in the intermediate cuneiform head. Results of the study indicate that no significant variations exist in the biomechanical comparisons between specific articulations, gross articulations, and left and right joints. For example, cartilage from the second metatarsal base and intermediate cuneiform head had an aggregate modulus of 0.99 MPa and 1.05 MPa, respectively. The Poisson's ratio and permeability of all test sites grouped together were found to be 0.08 and 3.05 x 10(-15) m4/N.s, respectively. Cartilage thickness was measured at 0.61 mm. This biomechanical study suggests that similarities in cartilage properties may be beneficial in preventing the human SMIC articulation from developing early degenerative changes. Histological evaluation demonstrated that SMIC cartilage exhibits structural characteristics (such as the absence of chondrocyte columnar arrangement in the deep zone) which may be typical of cartilage that does not experience habitually high compressive stresses. This knowledge could aid surgeons in generating a deeper perspective of the relationship between clinical pathologies of articular cartilage and intrinsic biomechanical etiologies of degenerative joint diseases.
Cruciate injury patterns in knee hyperextension: a cadaveric model.
We created an experimental model to evaluate the effects of strain rate on the mechanism of combined cruciate ligament injuries in knee hyperextension. Using straight knee hyperextension to rupture the anterior and posterior cruciates, two strain rates (approximately 100% per second and 5400% per second) were applied to reproduce two clinical injury patterns of the knee: low energy (sporting) and high energy (pedestrian-motor vehicle accident). Ten pairs of fresh-frozen cadaveric knees were injured to 45 degrees of hyperextension. Strain rate sensitivity of the posterior cruciate ligament was shown in this model, with midsubstance tears occuring in specimens tested at a low rate and avulsion "stripping" injuries from the femoral side occuring at a high rate. A variable pattern of anterior cruciate ligament tears at both high and low rates suggests that the specific injury mechanism may also involve other factors including notch morphology. We present a simplified mathematic model used to estimate posterior cruciate ligament strain during knee hyperextension.
Stress fracture of the humerus in a collegiate baseball pitcher. A case report.
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