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.

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.

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.

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.

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.

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.

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.

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.

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%).

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.

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.

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.

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.

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.

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.

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.

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.