Search PubMed⌕ Search

Biomedical subjects

J D Heckman

Publications and source records attributed to J D Heckman.

At least 37 records · Page 2Linked to original sources
PubMed1995

Protein release kinetics of a biodegradable implant for fracture non-unions.

Non-union of long bone fractures is often a serious complication of fracture healing. It is estimated that 100 000 non-unions occur in the united States annually and result in the loss of function of the involved limb. The present study was performed to develop a microporous polylactic acid-polyglycolic acid (PLA-PGA) implant for the delivery of bone morphogenetic protein (BMP) to sites of fracture non-unions, and to characterize the protein release kinetics of such an implant in vitro. A 50:50 copolymer of PLA-PGA was used to fabricate the implants using a gel formation technique. The implants were subjected to hydrolytic degradation in phosphate-buffered saline at 37 degrees C for up to 72 d. The protein release and the polymer degradation were monitored during this time period. The release kinetics of these implants were studied using a model protein, soybean trypsin inhibitor (TI), as well as BMP. The results indicate that there is a burst release of the proteins in the initial 48 h followed by a lower elution rate. The release of both the proteins followed similar trends. The molecular weight of the polymer decreased at a faster rate compared to its mass.

Animals↗
PubMed1994

Severe open fractures of the lower extremity: a retrospective evaluation of the Mangled Extremity Severity Score (MESS)

Recent reports using the Mangled Extremity Severity Score (MESS) suggest that a score of > or = 7 is 100% accurate in predicting the need for amputation of severely injured lower extremities. To further evaluate the value of the MESS in predicting amputation, specifically with respect to type IIIB and type IIIC (Gustilo and Anderson) open fractures of the tibia, we retrospectively evaluated 24 patients with these injuries. A significant difference (p = 0.001) between MESS values of 13 salvaged (6.36 +/- 0.35 SEM) and 11 amputated limbs (6.36 +/- 0.54 SEM) was found. A MESS value of > or = 4 was most sensitive (100%); a MESS value of > or = 7 was most specific, and a MESS value of > or = 7 was found to have a positive predictive value of 100%. Subsequently, we addressed recent criticisms of the MESS by including nerve injury in the scoring system and by separating soft-tissue and skeletal injury components of the MESS. We modified the MESS with a score called the NISSSA and applied it retrospectively to our cases. After careful statistical comparison we found both the MESS and NISSSA to be highly accurate (p < 0.005) in predicting amputation. The NISSSA was found to be more sensitive (81.8% versus 63.6%) and more specific (92.3 versus 69.2%).

Adolescent↗
PubMed1994

Acceleration of tibial fracture-healing by non-invasive, low-intensity pulsed ultrasound.

Sixty-seven closed or grade-I open fractures of the tibial shaft were examined in a prospective, randomized, double-blind evaluation of use of a new ultrasound stimulating device as an adjunct to conventional treatment with a cast. Thirty-three fractures were treated with the active device and thirty-four, with a placebo control device. At the end of the treatment, there was a statistically significant decrease in the time to clinical healing (86 +/- 5.8 days in the active-treatment group compared with 114 +/- 10.4 days in the control group) (p = 0.01) and also a significant decrease in the time to over-all (clinical and radiographic) healing (96 +/- 4.9 days in the active-treatment group compared with 154 +/- 13.7 days in the control group) (p = 0.0001). The patients' compliance with the use of the device was excellent, and there were no serious complications related to its use. This study confirms earlier animal and clinical studies that demonstrated the efficacy of low-intensity ultrasound stimulation in the acceleration of the normal fracture-repair process.

Adult↗
PubMed1992

Gel casting of resorbable polymers. 2. In-vitro degradation of bone graft substitutes.

Gel cast microporous materials produced from: slow resorbing, poly(L-lactide); fast resorbing, 50:50 poly(DL lactide coglycolide); and blends of these polymers have been characterized by weight loss, compression testing and thermal analysis after immersion in phosphate buffered saline (37 degrees C, pH 7.4) for times up to 6 months. Increasing weight loss and reduction in compressive properties with immersion time were measured. Blending reduces the rate of weight loss and material shrinkage relative to the copolymer. Thermal analysis of degraded samples revealed evidence of reorganization of the crystalline phase in poly(L-lactide) and a crystalline component in the 50:50 copolymer, estimated at 5-7% of the original material content, which is probably responsible for gel formation. Thermograms of the blend are effectively a superposition of thermograms of the individual components. Gel casting shows potential for varying the resorption rate, form stability and compressive properties of micro/macroporous bone graft substitutes.

Biocompatible Materials↗
PubMed1992

Gel casting of resorbable polymers. 1. Processing and applications.

A gel casting technique based on resorbable, synthetic, alpha-polyesters (or lactide-glycolide polymers) is described for producing medical implants such as bone graft substitutes and timed-release carriers for medication. This solution-based method enables production of thick-section solid and microporous materials, and blending of polymers and particulate fillers. Implant degradation rate, for example, may be adjusted by variation of polymer type, molecular weight range, crystallinity and morphology. Gel casting conditions are reported for solid and microporous materials and processing characteristics are interpreted in terms of established crystallization and dissolution behaviour of polymers.

Biodegradation, Environmental↗
PubMed1992

Excision of ununited fractures of the posterior process of the talus: a treatment for chronic posterior ankle pain.

The cases of nine patients with ununited fracture of the posterior process of the talus were reviewed. The most common mechanism of injury was forced plantarflexion. All patients had pain in the posterior ankle region. Common physical findings included tenderness between the lateral malleolus and the Achilles tendon and pain on forced plantarflexion. Of the radiographic imaging modalities used, 99Tc bone scan was found to be the most helpful in diagnosis. All nine patients eventually underwent surgical excision at a mean period of 9.4 months post injury. At average follow-up of 27 months after surgery (range 7-69 months), six of nine patients had good or excellent results with respect to pain relief and return to function. There were two complications of sural neuroma formation, one of which resulted in severe persistent pain after surgery. Based on these findings, we believe the differential diagnosis of chronic posttraumatic ankle pain should include fracture of the posterior process of the talus. Furthermore, excision of an ununited fragment through a lateral approach, taking care to preserve and protect the sural nerve, should lead to the return of painless function in the majority of cases.

Adult↗
PubMed1992

Initial effects of partially purified bone morphogenetic protein on the expression of glycosaminoglycan, collagen, and alkaline phosphatase in nonunion cell cultures.

Bone morphogenetic protein (BMP) stimulates mesenchymal cells to differentiate, resulting in de novo endochondral ossification in vivo. The response of fibrocartilage and periosteal cells from human and canine nonunion tissues to partially purified BMP was examined in culture. Cells derived from neonatal rat muscle explants were used for comparison. Alkaline phosphatase activity and expression of alkaline phosphatase and Types I and II collagen mRNAs were compared to that of rat chondrocytes. Synthesis of Type II collagen by the muscle cells was verified by enzyme-linked immunosorbent assay (ELISA). Addition of BMP to the muscle cell and nonunion cell cultures resulted in a dose-dependent decrease in cell number. There was a decrease in matrix vesicle and plasma membrane alkaline phosphatase activity concomitant with an increase in mRNA levels for alkaline phosphatase and collagen genes. Synthesis of immunoreactive Type II collagen increased. These data indicate that neonatal rat muscle cells and nonunion cells may respond in a similar fashion to BMP. Bone morphogenetic protein stimulated hyaluronic acid synthesis at three days, but chondroitin sulfate synthesis did not increase until ten days exposure to BMP. These data, together with those summarized above, suggest that more than three days may be required for complete expression of the chondrocyte phenotype typical of endochondral ossification.

Alkaline Phosphatase↗
PubMed1991

The use of bone morphogenetic protein in the treatment of non-union in a canine model.

A non-union model was established in the mid-part of the radial diaphysis in dogs. The non-union was treated with operative implantation of a carrier (guanidine-extracted, demineralized bovine bone or a polylactic acid polymer), alone or in combination with fractions that had been enriched in bone morphogenetic protein. All sites of treatment were examined radiographically and histomorphometrically at twelve weeks after implantation. Guanidine-extracted, demineralized bovine bone, alone or combined with fifteen milligrams of canine bone morphogenetic protein, failed to induce any healing of the non-union. When polylactic acid alone had been implanted, a small amount of reparative new bone was found in the defect at three months. When polylactic acid combined with fifteen milligrams of canine bone morphogenetic protein had been implanted, a significant increase in new bone formation was seen (p less than 0.03), compared with that seen in control animals. Trabecular bone bridged the gap between the proximal and distal fragments in all four specimens from the dogs that had received that treatment. In contrast, when polylactic acid combined with bovine bone morphogenetic protein had been implanted, significant reparative new bone was not found in the defect at three months.

Animals↗
PubMed1989

The heel of achilles: calcaneal avulsion fracture from a gunshot wound.

Greek mythology relates that the legendary warrior Achilles was made invincible by his mother Thetis, who dipped him in the River Styx while holding him by his heel. Because his heel was never immersed, it remained his one area of vulnerability. After the fall of Troy, Achilles met his demise when he was shot in the heel by Paris, whose arrow was guided by the Greek god Apollo. This is the derivation of the term "Achilles tendon." Avulsion fractures of the tuberosity of the calcaneus are rare injuries. Schonbauer reviewed a series of 870,000 accident cases treated at the Vienna Trauma Hospital and found only four such cases in addition to 151 cases of subcutaneous Achilles tendon rupture. In Bohler's series of 182 calcaneal fractures, avulsion of the calcaneal tuberosity accounted for less than 1% of these injuries. Rowe reported four Achilles avulsion fractures in his series of 154 calcaneal fractures. Three basic mechanisms of injury have been described: (1) dorsiflexion violence against the maximally plantarflexed foot, typically occurring in a fall from a height; (2) powerful contraction of the triceps surae muscle with simultaneous extension of the knee such as when a person is about to sprint in a race; (3) a direct blunt blow to the hindfoot. We are describing a case of avulsion of the calcaneal tuberosity due to direct penetrating trauma from a gunshot wound, a mechanism not previously reported.

Adult↗
PubMed1989

New techniques in the management of foot trauma.

Modern techniques are effective in the reduction and fixation of intraarticular fractures of the foot. While not all fractures can be restored anatomically, careful evaluation of roentgenograms and computed tomographic scans will identify those for which open reduction and internal fixation may be considered. Careful attention to the biomechanical principles and surgical techniques of open reduction and internal fixation can restore function and a useful, painless foot in previously hopeless cases.

Compartment Syndromes↗
PubMed1989

The role of the orthopedist in injury prevention.

Injury is an endemic disease process that is a leading cause of death and the leading cause of disability in the United States today. Among physicians, the orthopedic surgeon is most likely to be consulted by injured patients. Traditionally, orthopedists have played an important role in injury prevention as exemplified by the field of sports medicine. Three mechanisms have been demonstrated to be effective means of controlling the injury problem: (1) persuading persons at risk of injury to alter their behavior; (2) requiring individual behavior changes by law or administrative rule; and (3) providing automatic protection by product and environmental design. Specific strategies for implementing injury-prevention programs by the orthopedic surgeon are physician education, patient education, and public education.

Environment Design↗
PubMed1987

Supramalleolar osteotomy for the treatment of symptomatic tibial malunion.

Supramalleolar osteotomy was performed on eight patients who were symptomatic from a malunion of the distal two-thirds of the tibia. The patient's subjective reports of pain, limp, appearance, instability, and limitation of activity were evaluated pre- and postoperatively. Objective measurements of range of motion, angular deformity, and radiographic signs of ankle arthritis were also evaluated. All of the patients had varus malunion with a mean angulation of 15 degrees. Three of these patients also had sagittal malalignment. Supramalleolar dome or wedge osteotomies were performed to correct the coronal and sagittal plane deformities. Either internal (three patients) or external (five patients) fixation devices were applied to maintain correction. All osteotomies healed. The final mean angulation was 0 degrees in the coronal plane and 8 degrees of recurvatum. Complications included pin tract infections, wound breakdown, failure to completely correct the deformities, and loss of reduction. Seven of the patients reported symptomatic improvement after the procedure. The one patient who had a loss of reduction became more symptomatic.

Adolescent↗