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Biomedical subjects

J D Heckman

Publications and source records attributed to J D Heckman.

At least 19 recordsLinked to original sources
PubMed2006

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Evidence-Based Medicine↗
PubMed2001

Pulsed electromagnetic fields increase growth factor release by nonunion cells.

The mechanisms involved in pulsed electromagnetic field stimulation of nonunions are not known. Animal and cell culture models suggest endochondral ossification is stimulated by increasing cartilage mass and production of transforming growth factor-beta 1. For the current study, the effect of pulsed electromagnetic field stimulation on cells from human hypertrophic (n = 3) and atrophic (n = 4) nonunion tissues was examined. Cultures were placed between Helmholtz coils, and an electromagnetic field (4.5-ms bursts of 20 pulses repeating at 15 Hz) was applied to 1/2 of them 8 hours per day for 1, 2, or 4 days. There was a time-dependent increase in transforming growth factor-beta 1 in the conditioned media of treated hypertrophic nonunion cells by Day 2 and of atrophic nonunion cells by Day 4. There was no effect on cell number, [3H]-thymidine incorporation, alkaline phosphatase activity, collagen synthesis, or prostaglandin E2 and osteocalcin production. This indicates that human nonunion cells respond to pulsed electromagnetic fields in culture and that transforming growth factor-beta 1 production is an early event. The delayed response of hypertrophic and atrophic nonunion cells (> 24 hours) suggests that a cascade of regulatory events is stimulated, culminating in growth factor synthesis and release.

Adult↗
PubMed2001

Expanding roles of the orthopaedic surgeon.

Many sources predict an oversupply of orthopaedic surgeons in the United States continuing into the next 30 years. The most attractive solution to this problem is to expand the scope of orthopaedic practice by regaining direct patient access to orthopaedic specialty care, by developing and bringing new technologies and treatments to the marketplace quickly, and by developing alternatives to the typical orthopaedic practice such as expanding nonoperative care, improving the quality of the office practice, and exploring volunteer opportunities.

Humans↗
PubMed1999

Osteochondral progenitor cells in acute and chronic canine nonunions.

This study examined the ability of cells isolated from early healing segmental defects and from tissue from chronic nonunions to support bone and cartilage formation in vivo and their response to transforming growth factor-beta1 in vitro. Ostectomies (3 mm) were created in the radial diaphysis of four dogs. The dogs were splinted 3-5 days postoperatively and then allowed to bear full weight. At 7 days, tissue in the defect was removed and any periosteum was discarded; cells in the defect tissue were released by enzymatic digestion. The dogs were splinted again and allowed to bear full weight for 12 weeks. Radiographs confirmed a persistent nonunion in each dog. Defect tissue was again removed, any periosteum was discarded, and cells were isolated. Cells were also obtained from the defect tissue by nonenzymatic means with use of explant cultures. One-half of the tissue and one-half of any preconfluent, first-passage cultures were shipped to Cleveland by overnight carrier. At second passage, cells were loaded into ceramic cubes and implanted into immunocompromised mice for 3 or 6 weeks. Harvested cubes were examined histologically for cartilage and bone with use of a semiquantitative scoring system. Confluent fourth-passage cultures of 7 and 84-day defect tissue cells were cultured with 0.03-0.88 ng/ml transforming growth factor-beta1 for 24 hours, and [3H]thymidine incorporation and alkaline phosphatase specific activity were determined. Donor-dependent differences were noted in the rate at which defect cells achieved confluence; in general, cells from 7-day tissue divided most rapidly. Seven-day defect cells formed less bone and at a slower rate than was seen in the ceramic cubes containing samples from day 84. Cells derived enzymatically behaved similarly to those from explant cultures. Ceramic cubes contained fibrous connective tissue, cartilage, bone, and fat, indicating that multipotent cells were present. Stimulation of [3H]thymidine incorporation in response to transforming growth factor-beta1 was donor dependent and variable; only two of six separate isolates of cells exposed to it had measurable alkaline phosphatase activity (which was relatively low), and none of the cultures exhibited an increase in response to transforming growth factor-beta1 for 24 hours. This indicates that mesenchymal progenitor cells are present in the healing defect tissue at 7 and 84 days and that the relative proportion of osteochondroprogenitor cells is greater at the later time. The response to transforming growth factor-beta1 is typical of multipotent mesenchymal cells but not of committed chondrocytes or osteoblasts, indicating that these committed and differentiated cells are not present in early stages of healing and suggesting that their differentiation is inhibited in chronic nonunion.

Alkaline Phosphatase↗
PubMed1999

Biomechanical evaluation of fixation of posterior acetabular wall fractures.

Reproducible fractures of the posterior wall of the acetabulum were created in 10 paired hemipelves from fresh human cadavers. Under anterior-to-posterior loading by a Materials Testing System machine, the load to failure of fixation of the acetabular fractures treated with steel pelvic reconstruction plates and steel screws was significantly higher than that of fixation with titanium ribbons and titanium screws. Forces as little as 725 newtons applied directly to the fragment caused fixation failure; even the most secure form of fixation failed when a relatively small force of 2,123 newtons was applied. These results emphasize the importance of appropriate postoperative measures, such as limitation of hip flexion and restricted weightbearing, to minimize the force directed against the posterior wall until the fracture has healed. Secure fixation of fractures of the posterior wall of the acetabulum is critical, since loss of fixation results in instability and joint incongruity, which limit the options for reconstruction.

Acetabulum↗
PubMed1999

Bone morphogenetic protein but not transforming growth factor-beta enhances bone formation in canine diaphyseal nonunions implanted with a biodegradable composite polymer.

BACKGROUND: The purpose of the present study was to create an effective bone-graft substitute for the treatment of a diaphyseal nonunion. METHODS: A standardized nonunion was established in the midportion of the radial diaphysis in thirty mongrel dogs by creating a three-millimeter segmental bone defect (at least 2 percent of the total length of the bone). The nonunion was treated with implantation of a carrier comprised of poly(DL-lactic acid) and polyglycolic acid copolymer (50:50 polylactic acid-polyglycolic acid [PLG50]) containing canine purified bone morphogenetic protein (BMP) or recombinant human transforming growth factor-beta (TGF-beta1), or both, or the carrier without BMP or TGF-beta1. Five groups, consisting of six dogs each, were treated with implantation of the carrier alone, implantation of the carrier with fifteen milligrams of BMP, implantation of the carrier with 1.5 milligrams of BMP, implantation of the carrier with fifteen milligrams of BMP and ten nanograms of TGF-beta1, or implantation of the carrier with ten nanograms of TGF-beta1. At twelve weeks after implantation, the radii were examined radiographically and the sites of nonunion were examined histomorphometrically. RESULTS: We found that implantation of the polylactic acid-polyglycolic acid carrier alone or in combination with ten nanograms of TGF-beta1 failed to induce significant radiographic or histomorphometric evidence of healing at the site of the nonunion. The radii treated with the carrier enriched with either 1.5 or fifteen milligrams of BMP showed significantly increased periosteal and endosteal bone formation on histomorphometric (p < 0.05) and radiographic (p < 0.02) analysis. CONCLUSIONS: Bone formation in a persistent osseous defect that is similar to an ununited diaphyseal fracture is increased when species-specific BMP incorporated into a polylactic acid-polyglycolic acid carrier is implanted at the site of the nonunion. TGF-beta1 at a dose of ten nanograms per implant did not induce a similar degree of bone formation or potentiate the effect of BMP in this model. CLINICAL RELEVANCE: The biodegradable implant containing BMP that was used in the present study to treat diaphyseal nonunion is an effective bone-graft substitute.

Absorbable Implants↗
PubMed1998

Case report: fracture of the posterior medial tubercle of the talus secondary to direct trauma.

Isolated fracture of the posterior medial tubercle of the talus is a rare injury, generally thought to result from a pronation-dorsiflexion force causing avulsion of the insertion of the posterior talotibial ligament. Originally described by Cedell, the fracture has subsequently been reported three times to our knowledge, with all cases being attributed to indirect trauma. We describe an isolated fracture of the posterior medial tubercle of the talus caused by direct trauma. The fracture of the posterior medial tubercle remained ununited, failed to respond to conservative therapy, and was treated successfully with surgical excision.

Adult↗
PubMed1997

Acceleration of tibia and distal radius fracture healing in patients who smoke.

A low intensity ultrasound device was investigated as an accelerator of cortical and cancellous bone fracture healing in smokers and nonsmokers. Statistically significant reductions in healing time for smokers and nonsmokers were observed for tibial and distal radius fractures treated with an active ultrasound device compared with a placebo control device. The healing time for a tibial fracture was reduced 41% in smokers and 26% in nonsmokers with the active ultrasound device. Similarly, distal radius fracture healing time was reduced by 51% in smokers and 34% in nonsmokers with the active device. Treatment with the active ultrasound device also substantially reduced the incidence of tibial delayed unions in smokers and nonsmokers. The use of the active ultrasound device accelerates cortical and cancellous bone fracture healing, substantially mitigates the delayed healing effects of smoking, speeds the return to normal activity, and reduces the long-term complication of delayed union.

Adult↗
PubMed1997

Femoral-sided fracture-dislocation of the knee.

OBJECTIVE: To document a previously undescribed fracture-dislocation of the knee that involves a femoral condyle and associated ligaments yet spares the tibial joint surface. DESIGN: Retrospective. SETTING: University. PATIENTS: Four cases of fracture-dislocation of the knee that involve ligamentous injury and fracture of the femoral condyle(s). RESULTS: At a minimum two-year follow-up (average 28.8 months, range 26 to 37 months), overall functional outcome is only fair to good in this injury pattern. The Lysholm knee rating averaged 60 (range 39 to 74) and KT-1000 I-N testing averaged three millimeters at thirty pounds. CONCLUSION: Despite treatment of this fracture-dislocation with internal fixation of the femoral condyle(s) and repair of the ligament(s), functional deficits occur in this severe knee injury patterns.

Adult↗
PubMed1997

The economics of treating tibia fractures. The cost of delayed unions.

The tibia, being the most commonly fractured long bone, is associated with a high incidence of delayed union and non-union. A previously published prospective, randomized, double-blind and placebo-controlled tibia study demonstrated that pulsed, low-intensity ultrasound shortened the time to a healed fracture and significantly reduced the incidence of delayed union. The economics of treating tibia fractures has never been calculated. We have reviewed the literature pertaining to the tibia, the results of the above published tibia study, and stratified the data from that study for those patient and fracture co-morbidity factors that can influence healing of tibia fractures. Three economic models are presented with the total costs of treating a pool of 1,000 patients with tibial shaft fractures divided into two treatment paths--operative and conservative. These costs include surgery and recovery, outpatient costs, and Workers' Compensation costs for both the primary and secondary procedures, and emergency room and disability costs. The first model does not use low-intensity ultrasound and provides a summary of the costs associated with fracture treatment for each treatment path. The second model uses low-intensity ultrasound adjunctively with the conservatively treated group while the third model uses ultrasound adjunctively in both the operative and conservative groups. When comparing the conservative treatment path of Model 2 to Model 1 a cost savings of over $15,000 per case (40%) is realized by dramatically lowering secondary procedures and Workers' Compensation costs when pulsed low-intensity ultrasound is used adjunctively with conservative treatment. A similar savings of over $13,000 per case results from the use of ultrasound in the operative treatment path of Model 3 when compared with the standard operative care of Model 1. The total savings realized is over $14.6 million when adjunctively using low-intensity ultrasound in both the conservative and operative treatment paths. These analyses demonstrate that reduced healing time could yield substantial cost savings for third party payors, employers, and government agencies by lessening the need for secondary procedures and reducing the amount of Workers' Compensation payments.

Adult↗