Characterizing dynamic balance during adaptive locomotor learning.

In recent years, adaptation to walking on a split-belt treadmill has been used as a common paradigm to explore how humans and other vertebrates adapt to walking in an asymmetric environment. When people walk on a split-belt treadmill, they initially walk with an asymmetry characterized by steps of unequal length, then gradually adopt a symmetric walking pattern characterized by steps of the same length. Although it has been proposed that the adoption of a symmetric walking pattern may result from a desired to maintain dynamic balance, this has yet to be investigated. Therefore, we used a model and experiment to explore how dynamic balance is influenced by spatiotemporal asymmetry during walking on a split-belt treadmill. The model was constructed based on a two-state exponential model which updates foot placement at each step based on the asymmetry from the previous. In the experiment, participants adapted to walking on a split-belt treadmill with the left belt moving at 1.5 m/s and the right belt moving at 0.5 m/s. Retroreflective markers were used to measure lower extremity kinematics and to compute spatiotemporal metrics such as step length, dynamic margins of stability, and time-to-contact. We found that people showed greater margins of stability on the fast belt than on the slow belt during adaptation. This was accomplished by adjusting the angle of the leading limb, which determined the placement of their feet relative to the body's center of mass. The results also showed greater times to contact on the slow belt than on the fast belt during adaptation and the difference between the fast and slow belt decayed during adaptation. These experimental results were consistent with the simulation using the computational model. Our results help to improve our understanding of the role of biomechanics in driving adaptive changes to coordination when walking in novel environments.

The effectiveness of the clinical self-assessment (MHAQ) compared with other clinical and laboratory tests used to monitor the activity of rheumatoid arthritis by consensus analysis.

Disease activity in rheumatoid arthritis (RA) is difficult to measure objectively. Both clinical and laboratory measures were evaluated by the statistical method of consensus analysis. In the literature, laboratory tests as a group have proved more effective; however, studies did not include self-assessment questionnaires. We evaluated the effectiveness of a Modified Health Assessment Questionnaire (MHAQ) relative to other clinical and laboratory tests measuring disease activity in 100 patients with RA. Hemoglobin, hematocrit, mean corpuscular volume, fibrinogen level, Wes-tergren erythrocyte sedimentation rate and C-reactive protein tests, along with tests of morning stiffness, visual analog pain scale, Ritchie index, total joint count, and MHAQ, were evaluated simultaneously. The erythrocyte sedimentation rate was confirmed as a highly effective test to follow disease activity. The MHAQ was the best clinical test; in the methotrexate-treated subgroup it ranked as highly as the most effective laboratory assays. MHAQ is a more effective tool than many laboratory tests currently ordered for monitoring RA disease activity and should be a part of the record of each visit of an arthritis patient.

Restoring the edentulous maxilla using an implant-supported, matrix-assisted secondary casting.

The selection of appropriate implant treatment modalities for the edentulous maxillary arch is complex. Although many patients are candidates for an implant-supported removable prosthesis, two major considerations affecting choice of treatment type are the amount of residual alveolar bone and soft tissue, and cost. A technique is described that employs a cast milled primary bar and a secondary casting constructed using a vacuum-formed 0.040-in plastic matrix. The secondary casting is intimately adapted to the primary bar and incorporates the retentive elements within it. The resulting prosthesis is less expensive than comparable designs, and retentive elements are easily replaceable. The technique is adaptable to most implant systems. The matrix-assisted secondary casting technique provides a design that is esthetic and hygienic. The prosthesis may also be easier to insert and remove than implant-supported removable prostheses that use plunger- or latch-type retention.

Palatal extension of removable prostheses related to implant positions.

Once the decision has been made to construct a maxillary implant-supported overdenture prosthesis, implant location and number are important determining factors for palatal design. Eight clinical scenarios are described. Four cases require full palatal coverage, and four cases permit modified palatal coverage. Only two, with an increased number of implants and more posterior locations, permit a completely open palatal design similar to fixed prostheses.

Proper function, phonetics, and aesthetics achieved with implant-supported restorations: a multidisciplinary approach.

In a multidisciplinary restoration of the edentulous patient, close cooperation of involved personnel is essential during the treatment planning and the restorative procedures. This presentation is an overview of the rehabilitation of the edentulous maxilla, posterior maxilla, and the challenges of the single tooth implant-supported restorations. The prerequisite of teamwork is emphasized, past achievements and benefits of this treatment modality are reviewed, and three prosthetic challenges addressed. Clinical cases are used to illustrate the presentation.

Breast cancer after mammary augmentation.

Augmentation mammoplasty has been said to reduce the risk for subsequent development of mammary gland carcinoma, but it may confer a worse prognosis should breast cancer develop. Nine patients who had breast cancer after augmentation mammoplasty were treated at the Ochsner Foundation Hospital and Clinic. The mean interval between augmentation and the development of a palpable mass was 6.8 years (range, 2 to 20 years). Four patients were treated with modified radical mastectomy, one was treated with radical mastectomy, and four were treated with tylectomy, axillary dissection, and radiotherapy. One of the four treated with tylectomy required salvage mastectomy. Reconstructions were done in all except one mastectomy patient. Five patients had stage I disease and four had stage II disease at the time of diagnosis. Over a mean follow-up of 4.75 years from the time of diagnosis of carcinoma of the breast, three of the four patients with stage II disease have either had recurrent disease or died of breast cancer, and one of the patients with stage I disease died with hepatic metastases. Mammography was not found to be useful for the detection of masses after augmentation mammoplasty. Needle aspirations were useful for diagnosis of nodal disease outside the breast, but not helpful in diagnosis of the breast lesion proper. Our analysis suggests that breast augmentation and the patient's psychologic considerations may delay the diagnosis of breast cancer. Additionally, patients may fare worse when breast cancer develops after mammary augmentation. We recommend preoperative mammography in most patients before mammary augmentation, particularly in those over the age of 30 years and those with a family history of breast cancer.

Roentgenographic evaluation of the augmented breast.

We performed a retrospective study to determine the sensitivity of mammography in detecting breast cancer arising in women with augmented breasts. Of eight women with breast implants in whom breast cancer developed, six had mammograms before biopsy. Only two of the six cancers were identified mammographically (sensitivity = 33%), and one of these two was seen only in retrospect. In both cases, the mammographic findings suggested a benign rather than a malignant process. All eight women had a palpable mass and early disease, and all are clinically disease-free at present. The sensitivity of mammography in detecting palpable cancers in a control group of women without implants was 92% (118 of 128). For tumors of 2 cm or less, the sensitivity was 88% (58 of 66). These results suggest that the sensitivity of mammography in detecting breast cancer is decreased when implants are present. Further investigations are needed to determine the effects of prostheses on mammographic evaluations.

Wound healing. Helping a natural process.

Wound healing calls for little outside interference. All the physician need do is ensure that the wound is clean and debrided and decide whether closure by suture or by granulation tissue formation is indicated. Suture repair should be delayed if the wound is heavily contaminated. Use of skin tapes or of constant-pressure garments may enhance results.

Osteogenesis from periosteal autografts in ulnar defects in dogs.

The quantity of new bone formed by revascularized periosteal grafts was compared with that formed by nonvascularized periosteal grafts in ulnar diaphyseal defects in dogs. Although in general the revascularized periosteal grafts produced a greater quantity of bone than their nonvascularized counterparts, this osteogenic behavior was not consistent. The results, however, are sufficiently encouraging to merit further investigation into the free transfer of revascularized periosteal autografts.

Revascularized periosteal grafts--a new method to produce functional new bone without bone grafting.

Rib periosteum was transplanted to the groins of 9 dogs. In half of the periosteal grafts, no microvascular anastomoses were done (free grafts); at 6 weeks after grafting they had become resorbed. The other periosteal grafts were revascularized by microvascular anastomoses of the intercostal vessels to local muscular vessels; at 6 weeks those with confirmed vascular patency had all formed substantial amounts of new bone. Five cm, full-thickness defects were created in the tibias of 10 dogs. The control animals (without grafting) did not heal in two months. However, the experimental dogs, with vascularized periosteal grafts in the defects regenerated their tibias with healthy new bone by 6 weeks--and were walking on them then.