Orthotic devices. Degenerative disorders of the foot and ankle.

Orthotic devices are an effective method of treating degenerative arthrosis of the foot and ankle. When combined with appropriate medications and activity modifications, operative intervention may be postponed or rendered unnecessary. A thorough comprehension of relevant anatomy, biomechanics, and available devices is crucial to maximize the benefits of this modality.

Morphology of tibiotalar osteophytes in anterior ankle impingement.

The purpose of this study was to document radiographic trends in the size and location of osteophytes occurring in patients who have undergone surgical treatment of bony anterior ankle impingement. All patients over a period of 31 months who had undergone surgical excision of anterior ankle osteophytes were identified. 9 patients (10 ankles) in whom preoperative CT scans were available were selected as the study group. This group was retrospectively reviewed in terms of basic preoperative characteristics (age, sex, symptomatology, sports history, systemic disease, passive dorsiflexion). Osteophyte size was measured on plain lateral radiographs, and axial CT images were used to determine both tibial and talar osteophyte location by referencing them to the midline of the talar dome. 95% confidence intervals demonstrated that the talar spur peak lies medial to the midline, the tibial spur peak lies lateral to the midline, and the spurs typically do not overlap each other. Further, the tibial spur is wider than the talar spur, and the talar spur usually protrudes medially off the medial edge of the talar neck. Thus, there is evidence that anterior tibiotalar osteophytes may have a relatively consistent pattern of formation, with the talar spur occurring on the medial aspect of the talar neck, and the tibial spur peaking lateral to the midline.This information, if substantiated with additional patients, may provide insight into the pathophysiology of anterior ankle impingement, as well as facilitate the open and arthroscopic approaches toward resection of these lesions.

Missed and associated injuries after subtalar dislocation: the role of CT.

Subtalar joint dislocation (STJD) is an uncommon injury, but carries with it a potential for significant functional disability. We hypothesized that a significant number of injuries associated with subtalar joint dislocation may be unrecognized by plain radiographic examination. Therefore, we reviewed the records of all STJDs over a three-year period, identifying nine cases. The majority of injuries occurred in men (78%) with a mean age of 29 years. Overall, the mean age at injury was 32 years. The right lower extremity was most frequently injured (87.5%). Plain films initially diagnosed a STJ dislocation in all patients. A CT scan was performed in all cases. In 100% of patients, CT identified additional injuries missed on initial plain radiographs. In 44% of patient, new information gathered by CT dictated a change in treatment. Based on our findings, we conclude that CT is an invaluable tool to assess for associated injuries in STJ dislocation, and should be performed in all cases of STJ dislocation.

Use of bone morphogenetic protein-2 in the rabbit ulnar nonunion model.

The ability of the osteoinductive protein and recombinant human bone morphogenetic protein-2, combined with polylactic glycolic acid porous microspheres and autologous blood clot to heal a large segmental defect was tested in a rabbit diaphyseal defect model. Two centimeter nonuniting defects were surgically created in the bilateral ulnae of 50 male New Zealand white rabbits. Each defect was then implanted with a pastelike polylactic glycolic acid/blood clot combination that was mixed with 5 different concentrations of recombinant human bone morphogenetic protein-2. The forearms were radiographically assessed on a biweekly schedule for 8 weeks. At 8 weeks, all animals were sacrificed and forearms radiographed. Radiographs were then scored by 3 independent observers for bone formation and union rates. United limbs were tested in torsion for mechanical strength using a Burstein torsion tester. All nonunited limbs were analyzed histologically as were 2 united limbs from each dosage group. Radiographic evaluation revealed that there was a dose dependent response in healing of the ulnar defect with a higher bone formation rate in the 2 higher dose limbs than in the lower dose limbs. Union was achieved in 100% of the highest dose limbs, whereas only 50% of the lowest dose limbs achieved bony union. No defects implanted with carrier alone achieved union. Biomechanical studies revealed significantly stiffer bone than age matched controls. Histologic analysis demonstrated normal bone formation with abundant normal appearing osteoid. These dose response data further support the role of recombinant human bone morphogenetic protein-2 as a potent morphogen in bone regeneration.

Immunolocalization and expression of bone morphogenetic proteins 2 and 4 in fracture healing.

Recently, it has become increasingly evident that fracture healing involves a complex interaction of many local and systemic regulatory factors. The roles of some of these growth factors have been described; however, little is understood about the presence of the bone morphogenetic proteins in fracture repair, despite the fact that they are the most potent osteoinductive proteins known. This study defines and characterizes the physiologic presence, localization, and chronology of the bone morphogenetic proteins in fracture healing with an established rat fracture healing model. With use of a recently developed monoclonal antibody against bone morphogenetic proteins 2 and 4 developed with standard avidin-biotin complex/immunoperoxidase protocols, frozen undecalcified fracture calluses were analyzed semiquantitatively for the percentage of various types of fracture cells staining positively. During the early stages of fracture healing, only a minimum number of primitive cells stained positively in the fracture callus. As the process of endochondral ossification proceeded, the presence of bone morphogenetic proteins 2 and 4 increased dramatically, especially in the primitive mesenchymal and chondrocytic cells. While the cartilaginous component of the callus matured with a concomitant decrease in the number of primitive cells, there was a concomitant decrease in both the intensity and the number of positively staining cells. As osteoblasts started to lay down woven bone on the chondroid matrix, these osteoblastic cells exhibited strong positive staining. The intensity of this staining decreased, however, as lamellar bone replaced the primitive woven bone. A similar observation was noted for the areas of the callus undergoing intramembranous ossification. Initially, within several days after the fracture, periosteal cells and osteoblasts exhibited intense staining for bone morphogenetic proteins 2 and 4. As the woven bone was replaced with mature lamellar bone, this staining decreased. These data, and the awareness of the strong osteoinductive capacities of bone morphogenetic protein, suggest that bone morphogenetic proteins 2 and 4 are important regulators of cell differentiation during fracture repair.

A biomechanical evaluation of the long stem intramedullary hip screw.

Despite the advantages associated with short-stem intramedullary hip screw devices for the treatment of intertrochanteric fractures, recent reports have shown an increased incidence of femoral shaft fractures after their insertion. These findings led to the hypothesis that an intramedullary hip screw with a longer stem may more effectively redistribute loads to the distal end of the femoral shaft, where they may be more readily absorbed by the increased bony cross-sectional area. To characterize the load patterns of a long-stem device in the femur, 10 fresh-frozen adult femurs were instrumented with unidirectional strain gauges. A total of eight strain gauges were placed in the direction of principal femoral strains on the medial and lateral surfaces of each femur. Each femur was held in a steel vice at 15 degrees of adduction in the coronal plane and vertical in the sagittal plane. The femurs were then subjected to successively increasing vertically applied compressive loads from 0 N to 1,400 N at 200-N increments using a servohydraulic testing machine. Strain values were recorded at each load after a 5-min equilibration period. Each femur was tested under five conditions: (a) intact, (b) after insertion of the long-stem intramedullary hip screw device, (c) with an experimentally created two-part fracture, (d) with a stable four-part fracture, and (e) with an unstable four-part fracture with the posteromedial fragment removed. Half the femurs were randomly assigned to have two distal interlocking screws placed before fracture. The remaining half were loaded without distal interlocking screws.(ABSTRACT TRUNCATED AT 250 WORDS)

Fatigue testing of cerclage stainless steel wire fixation.

Because wire fixation continues to be used extensively in the practice of orthopaedic surgery, despite a high incidence of wire breakage, understanding the mechanism of this failure is of important clinical interest. The aim of this study was to investigate the failure of cerclage stainless steel wire using an in vitro cyclic loading device. A stainless steel testing fixture consisting of two half cylinders with a combined diameter of 2.5 cm was mounted in a servo hydraulic testing machine. Specimens of number 18 gauge (0.97 mm diameter) and number 16 gauge (1.22 mm diameter) 316L stainless steel wire were mounted around the two half cylinders in a cerclage manner using three different fastening methods: a uniform symmetrical twist, a knot twist, and a square knot. Single-load-to-failure and cyclic load tests were performed under controlled tensile displacement. The cerclage wire system fastened with a twist resulted in failure at loads significantly lower than systems fastened with the knot twist and the square knot. Cyclic loading of the wire fastened with twists also showed decreased fatigue properties when compared to those fastened with the knot twist and the square knot. In all tests, the 16-gauge wire was found to be clearly superior to the 18-gauge wire. For both wires, fatigue strengths at 100,000 cycles were only 30-37% of the static ultimate strength. These results show that wire diameter and fastening system are two important factors affecting the mechanical properties of the resulting fixation.