Chao, Edmund Y.S.

Summary Modular, porous-coated, titanium segmental endoprostheses were implanted bilaterally in the femoral diaphysis of 7 adult mixed-breed dogs. Autogenous bone graft in particle form was placed around the implant and bone. In 1 limb, homologous fibrin adhesive was mixed with the graft in situ before soft tissue closure. The contralateral limb was grafted in identical manner, but without fibrin adhesive, and served as a control. Radiography was performed immediately after surgery and 1, 2, 3, 4, 6, 8, 10, and 12 weeks later to assess callus area and bone remodeling. At 12 weeks, dogs were euthanatized and bone/implant fixation strength was tested under torsion and compared with values for 6 in vitro controls. Histomorphometric and microradiographic analyses of transverse sections of the distal portion of the implanted femurs were performed. Radiographic callus area was significantly (P < 0.05) smaller in the femurs grafted with fibrin adhesive, compared with the contralateral control. New bone formation (21.4 ± 1.8% vs 19.2 ± 2.4%), unlabeled bone (64.8 ± 3.0% vs 67.9 ± 4.2%), porosity (13.9 ± 0.7% vs 12.9 ± 0.8%), and bone ingrowth into the porous coating (10.3 ± 0.9% vs 10.0 ± 1.2%) were not significantly different between fibrin- and nonfibrin-grafted implants, respectively. There were no significant differences in torsional strength of implant fixation between the fibrin- and nonfibrin-grafted femurs or between the in vivo implanted femurs and the in vitro controls. These data indicate that fibrin adhesive may have been advantageous in maintaining apposition of bone graft adjacent to the endoprosthesis, but it probably did not have an enhancing effect on extracortical bone bridging or ingrowth over a porous-coated segmental bone replacement endoprosthesis.

Summary Quantitative computed tomography has been used extensively to measure bone mineral density; particularly in the vertebral column and in the proximal portion of the femur in human beings with osteoporosis. Other potential applications of this technique include evaluation of bone adjacent to metallic endoprostheses and evaluation of fractures as they heal. Unfortunately, metal causes severe image degradation, principally seen as starburst streaking. One method used to decrease these artifacts is by imaging less-attenuating materials, such as titanium alloy. Titanium decreases image degradation sufficiently to allow accurate determination of the geometric properties of cadaveric bone. In our study, the effect of a titanium segmental endoprosthesis on bone mineral density measurement was determined by use of bone specimens from dogs and calibration standards. Titanium decreased the bone mineral density of calibration solutions from 6.8 (500 mg/cm3) to 17.7% (250 mg/cm3), and increased bone mineral density of cortical bone by 5.3%. Titanium did not affect the repeatability of these scans, indicating that the error caused by titanium was systematic and can be corrected. Our data were suggestive that quantitative computed tomography can be used to measure bone mineral density of cortical bone adjacent to titanium endoprostheses, with a predictable increase in density measurement.

Summary The purpose of this study was to determine the precision and accuracy of quantitative computed tomography bone mineral analysis in dogs in coronally reconstructed images. Nonhomogeneous tissues, such as bones with fractures or deformities, may be better analyzed if multiplanar reconstruction of the transaxial data could be performed without degradation of information. Our analysis demonstrated that coronal reconstruction of quantitative-computed tomography data was precise (1.2 to 4.7%) and accurate (1.3 to 7.5%) in vitro. The technique displays high-quality images, which can be analyzed at any location within the volume scanned. Quantitative computed tomography of canine osteotomy healing in vivo accurately determined bone mineral density of selected regions of interest. Bone mineral density correlated highly with calcium content of the tissue (R2 = 0.76, P < 0.0001).

Abstract An efficient 2-D continuum finite element method (FEM), including the rigid body algorithm and our previously developed contact element, was formulated for the contact stress analysis of articular joints. This FEM can calculate the contact pressure distribution on articular surfaces and stress distribution inside of cartilage. This method can model geometric and material nonlinearities for both the static and dynamic situations. The major advantage of this method is that only the soft cartilage requires finite element (FE) mesh, while the bony structure can be modeled as a rigid body due to its relatively rigid nature. Since much less degrees of freedom are now required in FEM, much faster computing speed can be achieved.

We have reviewed 30 patients at a mean of 36 months after free vascularised fibular transfer to reconstruct massive skeletal defects after resection of primary bone tumours. There were 23 malignant and 7 benign neoplasms, half in the lower limb and half in the upper. Arthrodesis was performed in 15 and intercalary bone replacement in 15. The mean fibular graft length was 189 mm. Union was achieved in 27 (90%) at an average of 7.6 months, and the 3-year survival was 89%. There was a high complication rate (50%), but most resolved without greatly influencing the final outcome. There was local recurrence in two (6.7%), but 16 of the 24 assessed patients (67%) had satisfactory functional results. This is a reasonably effective means of reconstruction for limb salvage after resection of tumours.

The biomechanical evaluation of patients with painful heels has received only limited attention although the potential morbidity and disability associated with such an ailment can be severe. An objective analysis of the patient's foot function during gait can produce useful information to assess the underlying pathology. This method can also help to evaluate the efficacy of various existing treatment protocols. The impulse distribution based on foot-floor vertical reaction force and time under the hind-, mid-, and forefoot was determined in 32 normal subjects while walking in their usual street shoes. Variations related to shoe types were noted, with high heeled shoes causing the most significant deviations from normal. The same technique was applied to 13 painful heel syndrome patients. Characteristic deviations from the normal impulse distribution were noted in these patients which provided the basis for differentiating the pathological condition between the patients with painful heel pads and those with plantar fasciitis. The effectiveness of using heel cups as a therapeutic device was also assessed. Although significant gait changes were not associated with the insertion of heel cups, they did seem to shift the foot-floor impulse forward from the heel region, which made them effective in patients afflicted with localized heel pain, but not in those with plantar fasciitis.

Eleven patients who were treated for talonavicular arthrosis with a talonavicular arthrodesis between 1961 and 1979 at the Mayo Clinic have been reviewed. Follow-up from surgery ranged from 2.5 to 21 years with a mean of 9.5 years. Clinical, radiographic, and gait analyses were obtained. All patients had satisfactory pain relief, but all noted difficulty in ambulating on irregular ground. Three patients had roentgenographic evidence of arthrosis affecting other tarsal joints that had not been involved before arthrodesis. Gait analysis revealed decreased terminal stance-phase plantarflexion and pronounced reduction of subtalar motion. Talonavicular arthrodesis does give predictable union and patient satisfaction but results in limitation of subtalar motion and loss of stance-phase plantarflexion.

In spite of the common occurrence of pes planus and multiple operations that have been reported to relieve the associated symptoms, there is little published on the relative contribution of various structures to stabilization of the arch of the foot. Twelve fresh-frozen human cadaveric feet were loaded along the tibial axis with compressive loads of 230, 460, and 690 newtons with the specimens intact and after sequential sectioning of plantar fascia, plantar ligaments, and spring ligament. Structures were sectioned in six different sequences and changes in vertical and horizontal dimensions of the medial arch were measured. The highest relative contribution to arch stability was provided by the plantar fascia, followed by plantar ligaments and spring ligament. Plantar fascia was a major factor in maintenance of the medial longitudinal arch. Its division in the cadaveric feet decreased arch stiffness by 25%.

Implant removal and synovectomy were used to treat the failure of 14 first metatarsophalangeal joint implant arthroplasties. Revision surgery was performed at an average of 3.1 years after arthroplasty. Follow-up (average 4.9 years) was possible in 10 patients, and clinical results were excellent in seven patients, good in one patient, fair in one patient, and poor in one patient. No significant changes in alignment occurred, although a trend toward toe extension was noted. Dynamic force plate studies in these patients demonstrated less pressure under the first metatarsal head and greater loading under the lateral forefoot. The great toe had less contact time during gait in the involved feet than in the control feet.

Thirteen consecutive patients underwent plantar fasciotomy in 16 feet for intractable plantar fasciitis and had follow-up from 4.5 to 15 years. Plantar fasciotomy was successful (good or excellent results) for 71% of the 14 feet operated on and for which follow-up data were available. However, time to full recovery was prolonged, additional treatment was frequently required, and abnormalities of foot function persisted. Flattening of the longitudinal arch occurred. Dynamic force-plate studies showed differences in peak vertical, fore-aft, and lateralmedial forces between patients and matched controls. More rapid progression of weightbearing along the longitudinal axis of the foot during stance phase in patients indicated avoidance of heel loading.