Excessive Granulation Research Articles

A New Self-Expanding, Removable, Covered Metal Tracheobronchial Stent: Results of an Animal Trial

Background Tracheobronchial airway stents are increasingly being used to palliate malignant and benign obstruction of central airways. Metallic stents overcome many of the drawbacks of silicone stents. However, because of the excessive granulation tissue (GT) formation, longer these metallic stents are in place, more difficult it is to remove them and more problems they create. Objectives To evaluate airway tolerance of a new hybrid stent meant to capture the advantages of both silicone and metal stents in an animal model known to be prone to develop acute airway inflammation with metallic stents. Methods Study stents (Alveolus AERO) and control stents (Ultraflex stent, Microvasive, Boston Scientific Corporation, Natick, MA) were implanted in the trachea of 8 piglets. Proximal and distal implantation sites were randomly alternated between study and control stents within the same pig. Fourteen and 28-day bronchoscopic follow-up allowed assessment of airway tolerance of the stents with special focus on GT formation and ease of stent removal. Results Study stents produced nothing but mild GT, removal was easy. Control stents in contrast showed moderate or severe inflammatory reactions, which made removal of the stent difficult in 3 cases and impossible in 2 cases. Conclusions The new hybrid stents cause less GT in the short term in an animal model. Complications of long-term stent placement and migration need to be assessed.

Fibrin Glue and Polyglycolic Acid Nonwoven Fabric as a Biocompatible Dural Substitute

A novel biocompatible dural substitute created using fibrin glue and polyglycolic acid nonwoven fabric was examined for closing ability and histology. A rabbit skin model of dural defect was repaired using fibrin glue-covered polyglycolic acid fabric without suture and subjected to a water leakage test to investigate closing ability. In addition, the dural defects created on 12 hemispheres in 6 beagle dogs were repaired with the dural substitute and subjected to macroscopic and histological examination of the dural substitute and adjacent tissue 1 and 2 months later. The dural substitute showed a breaking pressure of 109.9 +/- 37.1 mmHg. Macroscopically, no cases of excessive granulation, infection, or liquorrhea, either on the dural substitute or surrounding tissue, were observed. Histology indicated favorable tissue replacement of the dural substitute with collagenous fiber, although slight foreign body reaction was associated with its absorption. There was no evidence for adhesion to the brain surface or influence on nerve cells. Dural substitute created using fibrin glue and polyglycolic acid fabric is advantageous in that it exerts excellent closing ability without requiring suture and can replace biological tissue without causing incompatibility.

Prognosis after simple incision and drainage for a first-episode acute pilonidal abscess.

During a 3-year period 73 patients were treated consecutively for a first-episode acute pilonidal abscess with simple incision and drainage under local anaesthesia. In all cases the treatment relieved symptoms and all patients returned to work immediately after treatment. Healing per primam occurred in 42 patients (58 per cent; 95 per cent confidence limits: 45-69) within 10 weeks after treatment. These patients had significantly fewer pits and lateral tracts compared with patients who developed excessive granulation tissue after incision and who required definitive surgical treatment later. Nine patients (21 per cent; 95 per cent confidence limits: 10-37) with healing per primam developed recurrence of their pilonidal disease during the prospective follow-up period (median follow-up period was 60 months, range 36-84 months). Actuarial analysis of the data revealed a constant cure rate of 76 per cent (95 per cent confidence limits: 57-95) after 18 months.

Outcomes of Tracheobronchial Stents in Patients With Malignant Airway Disease

Malignant central airway obstruction is difficult to manage and is associated with poor outcome. We sought to identify the short (< 30 days) and intermediate (> 30 days) benefits and risks of tracheobronchial stents in patients with malignant airway disease. Two hundred and twenty-five tracheobronchial stents were placed in 172 patients for benign (n = 32) and malignant (n = 140) disease from January 1, 1997, to May 31, 2003. The records of the patients with malignant disease were retrospectively analyzed to determine complication rate, reintervention rate, and survival. The malignant diagnoses included nonsmall cell cancer, small cell cancer, esophageal cancer, and metastatic disease. There were 172 stents placed in 140 patients with malignant disease, with no intraoperative mortality. The mean follow-up period was 142 +/- 12 days. There were 23 complications, including tumor ingrowth (n = 9), excessive granulation tissue (n = 7), stent migration (n = 5), and restenosis (n = 2). Five of the complications occurred during the short-term period (< 30 days) with the remaining complications (n = 18) occurring after 30 days. The complications required interventions including laser debridement (n = 14), dilation (n = 4), and stent removal (n = 5). Tracheobronchial stents offer minimally invasive palliative therapy for patients with unresectable malignant central airway obstruction. The benefit of airway stents is particularly seen in the short-term period where they provide symptomatic improvement and have low complication risk. The major impediment is excessive granulation tissue and tumor ingrowth, which occur primarily after 30 days.

Treatment of airway obstruction by metallic stents in infants and children

The internal metallic stent is a relatively new and controversial method for the treatment of airway collapse in infants and children. The study examined the outcomes of this treatment in a large group of patients and defined clear indications for airway stenting. A retrospective review was conducted of 32 patients in whom 42 stents were inserted. The patients were divided into three groups with respect to the stented segment: group A, trachea (n = 14); group B, bronchi (n = 16); and group C, trachea and bronchi (n = 2). In 30 cases, there was immediate improvement of respiratory obstruction, and 23 patients could be weaned, at least temporarily, from ventilation. Excessive granulation developed after the stenting in 26 patients. In 6 patients, all in group A, the granulation and inflammatory reaction generated severe airway obstruction, necessitating thoracotomy in 2 cases. One patient died of airway obstruction, and another died during the attempt to remove the stent; both were in group A. Stents placed for 2 to 72 months (mean 8.7 months) have now been removed in 11 patients. Six children are alive and well with stents in place, 2 from group A and 4 from group B. Fifteen patients died during the follow-up period; in 13 cases, death was related to the associated disease. The use of metallic stents, especially in the trachea, is associated with a high rate of complications. Granulation tissue, which often develops after stenting, is a major concern. Removal of the stents is arduous and carries a high risk of complications. The use of stents should be restricted to the limited situations in which conventional initial therapy has failed.

The alpha-3 polypeptide chain of laminin 5: insight into wound healing responses from the study of genodermatoses

Laminin 5 (kalinin/epiligrin/nicein) is an essential structural component of the dermal-epidermal junction, composed of three polypeptide subunits: laminin alpha3, beta3 and gamma2. Studies of the inherited skin fragility disorder junctional epidermolysis bullosa (JEB) have suggested that the major role of this heterotrimeric protein is to act as an adhesive ligand essential for binding the epidermis to the underlying dermis and thus maintaining the integrity of the skin. Protein interaction studies have shown that the C terminus of the alpha3 subunit binds to a range of integrin complexes depending on the motility status of keratinocytes. This allows laminin 5 to interact with either hemidesmosomes or the actin cytoskeleton. Recently we have reported that the absence of the N-terminal region of laminin alpha3a in laryngo-onchyo-cutaneous syndrome causes excessive granulation tissue production at wound sites. As granulation tissue production is also a problem in JEB, this implicates laminin 5 in control of this wound healing response.

Otologic Effects of Topical Mitomycin C: Phase I-Evaluation of Ototoxicity

To determine ototoxicity of topical mitomycin C when placed in the middle ear at varying concentrations. Despite meticulous surgical technique and diligent postoperative care, some patients develop excessive scar and granulation tissue in the middle ear or mastoid cavity. Poor wound healing may result in infection, tympanic membrane perforation, or conductive hearing loss, which may necessitate further surgery. Use of topical mitomycin C in the ear may be beneficial in reducing scar and granulation tissue formation. This phase of the study was developed to determine the safety of topical mitomycin C in the rat model relative to ototoxicity. Twelve Sprague-Dawley rats were evaluated with auditory brainstem response testing before and after treatments. Topical mitomycin C was injected in the middle ear of the right ear of eight animals. Varying concentrations of 0.125 to 0.5 mg/ml were used. Saline was injected in the left ear of each animal to serve as a control. Four separate animals were evaluated with placement of topical mitomycin C on Gelfoam into the middle ear. In two animals, Gelfoam was placed in the middle ear for 1 minute and then removed. In two animals, Gelfoam was placed in the middle ear and left in place. Auditory brainstem response testing was performed at 4 weeks and at 8 weeks. Using a high concentration of mitomycin C (>0.25 mg/ml) resulted in ototoxicity, with an increase in the auditory brainstem response threshold at 4 weeks and at 8 weeks. At low concentrations (<0.20 mg/ml), no change in auditory brainstem response threshold was noted. Animals treated with Gelfoam soaked in mitomycin C showed no change in auditory brainstem response threshold. The results of this study indicate that topical mitomycin C on Gelfoam applied in the middle ear appears safe when low concentrations are used, even in the rat, which has a higher susceptibility to gentamycin toxicity than humans. Higher concentrations may lead to ototoxicity based on changes in Wave V on auditory brainstem response. This treatment may prove to be an important option for patients suffering from chronic granulation tissue or scar tissue in the external or middle ear.

Hoarseness during isotretinoin therapy

To the Editor: Isotretinoin is an effective therapeutic agent for acne. Its use is often associated with adverse reactions, such as excess granulation tissue formation. A 38-year-old woman with papulopustular acne began isotretinoin therapy at a dose of 30 mg daily (0.6 mg/kg). Three weeks later, she noticed mild hoarseness. In a laryngeal examination, two incipient nodules, one over each vocal cord, were observed. As the patient had a history of vocal abuse caused by teaching activities, the lesions were thought to be secondary to it. Six weeks later, when the hoarseness became severe, a second laryngoscopic examination revealed a complete replacement of both nodules by granulomatous tissue. Surgical removal of the lesions was proposed, and meanwhile, after 5 months of treatment, isotretinoin therapy was stopped. Two weeks later, the hoarseness started to improve and completely dissapeared 6 weeks after the drug's withdrawal. A third laryngoscopic examination showed no granulomatous tissue over the original nodules of the vocal cords. Retinoid therapy is known to be associated to excess granulation tissue responses.1.Hodak E. David M. Feuerman E.J. Excess granulation tissue during etretinate therapy.J Am Acad Dermatol. 1984; 11 ([letter]): 1166-1167Abstract Full Text PDF PubMed Scopus (28) Google Scholar, 2.Campbel J.P. Grekin R.C. Ellis C.N. Matsuda-John S.S. Swanson N.A. Voorhees J.J. Retinoid therapy is associated with excess granulation tissue responses.J Am Acad Dermatol. 1983; 9: 708-713Abstract Full Text PDF PubMed Scopus (75) Google Scholar, 3.Kanoh H. Izumi T. Hiramatsu T. Ohnishi M. Murai M. Seishima M. Granulomatous nodule on vocal cord possibly induced by etretinate therapy.Br J Dermatol. 2000; 142 ([letter]): 1258-1259Crossref PubMed Scopus (2) Google Scholar The cause is unknown, although minor trauma may be a possible trigger.4.Katayama H. Okabe N. Kano T. Yaoita H. Granulation tissue that developed after a minor trauma in a psoriatic patient on long-term etretinate therapy.J Dermatol. 1990; 17: 187-190PubMed Google Scholar In our patient, vocal abuse could have been the origin of this response. We report the first case of hoarseness possibly caused by excess granulomatous tissue formation over nodules on the vocal cords during isotretinoin therapy. We consider it important to be aware of this newly recognized adverse reaction to avoid a surgical procedure for a potentially reversible lesion.

Management of the Umbilical Cord

After completing this article, readers should be able to: 1. Describe the most serious infection that may result from inappropriate management of the umbilical cord and potential sources. 2. Describe the relationship between infant bacterial colonization and postpartum infection. 3. List the most common neonatal staphylococcal infections. 4. List the factors that affect the timing of cord separation. 5. Delineate the probable causes of drainage from the umbilical stump. This review addresses several aspects of the care of the umbilical cord: how to ligate and cut it, what (if anything) to apply to it, the problems that may be associated with ligation and cutting, and the natural history of cord separation. The traditional method of ligating the umbilical cord was to use string or twine to tie the cord before cutting it. In Southern Sudan, fine stringlike roots are used to tie the cord. More recently in the United States, special cotton tape (umbilical tape) was used and still is found on most trays used for insertion of catheters into umbilical blood vessels. Because the umbilical cord tends to shrink after birth, these types of ligature proved somewhat unreliable in preventing hemorrhage. Although the umbilical arteries tend to constrict rapidly after birth because of the muscular walls, this does not occur with the umbilical vein. Consequently, more efficient and effective methods of ligation were sought in the middle of the 20th century. The first method was to use constricting rubber bands, which were effective, but somewhat difficult to apply. This method recently found favor in a developing country (Ethiopia). However, the more usual method in developed countries currently is plastic or metal clamps, which produce safe, reliable constriction. In particular, the plastic Hollister® clamp (Double-Grip Umbilical Cord Clamp, Hollister, Libertyville, IL) has been very successful in preventing bleeding from the cord. These devices are removed …

Effect of acitretin on wound healing in organ transplant recipients.

Systemic retinoids possess significant benefits in cutaneous malignancy chemoprevention; however, retinoids have been associated with excessive granulation tissue and hypertrophic scarring. The objective of this study was to assess wound healing outcomes in organ transplant recipients, both with and without the concomitant use of systemic acitretin chemoprophylaxis. Twenty-nine immunosuppressed organ transplant recipients underwent treatment of basal cell or squamous cell carcinoma by Mohs or excisional surgery, with a total of 85 wounds. Wounds were evaluated postoperatively at early (average 12.9 days) and late (average 75.8 days) time points. Endpoints for all wounds included infection, hypertrophic granulation tissue, and hypertrophic scarring. Reconstructed wounds were also evaluated for dehiscence. Eleven patients taking oral acitretin had 41 wounds, of which 33 were reconstructed and 8 healed by second intention. The 18 patients not taking acitretin (control group) had a total of 44 wounds, of which 33 were reconstructed and 11 healed by second intention. There were no statistically significant differences between the acitretin group and the control group in the incidences of infection, dehiscence, hypertrophic granulation tissue, or hypertrophic scarring at early or late evaluation points. Systemic acitretin chemoprophylaxis does not appear to increase the risk of wound healing complications in organ transplant recipients.

Association of anti-donor HLA class I antibodies with early coronary transplant vasculopathy

3 cases due to in-stent stenosis from excessive granulation tissue. The mean time to in-stent stenosis was 188 days. Stent migration into the mediastinum occurred in 1 patient, requiring replacement with a wider, longer stent. Two patients required repeat insertion of SEMS after removal, due to severe bronchomalacia. The mean time between stent replacements was 38 days. Conclusion: In patients with high-grade BD SEMS offers prospects for successful outcome. SEMS are known to be associated with significant granulation tissue formation. In our opinion this property of SEMS provides a platform for healing of dehiscence and in time, peribronchial soft-tissue support grows in to cover the defect allowing stent removal.

The effectiveness of hyperbaric oxygen treatment in tracheal reconstruction with auricular cartilage grafts (experimental study)

Purpose Tracheal stenosis or neoplastic changes, as well as, traumatic, congenital, or iatrogenic causes may require extensive tracheal resections. Complications like vascularization insufficiency and structural support problems occur nearly in all cases when end-to-end anastomosis of trachea is not feasible. Hyperbaric oxygen (HBO) treatment is a well-known method for the management of grafts and flaps that have vascularization problems. In this study, the effect of hyperbaric oxygen treatment on wound healing after tracheal reconstruction with auricular cartilage graft (ACG) has been evaluated. Methods Thirty-two rabbits were divided into 2 groups: study group (n = 16) and control group (n = 16). The anterior halves of the six tracheal rings were resected, and the defects were repaired with autogenic auricular grafts. Hyperbaric 100% pure oxygen was administered to the study group at 2.4 atmospheres of absolute pressure 2 times a day for 1 week. The control group did not receive any therapy except proper control of the wound. Results It was observed that in the study group, inflammation, fibrosis, and necrosis were less, whereas epithelialization and maturation were early and neovascularization and neochondrification were more than the control group only at specific weeks. But all tracheas in both groups showed excellent healing without graft rejection and excessive granulation tissue formation. Furthermore, there was no statistically difference between the 2 groups. Conclusions Auricular cartilage grafts is a valuable management method of tracheal defects, and hyperbaric oxygen treatment is a good supplementary method in healing period of cartilage autografts.

Case report

A total of 17 dairy cows with sole ulcers were treated, and the healing process observed [USA; date not given]. Nine cows had mature, uncomplicated ulcers where the exposed corium appeared only slightly damaged in 6 cases, and more seriously damaged in 3 cases. The remaining 8 animals had complicated ulcers, all of which had a discharging tract at the ulcer site with swelling of the heel, coronary band, and flexor aspect of the digit extending to and above the metatarsus. Ulcers were regarded as typical lesions (Rusterholz ulcers) in 16 cows, and one cow had a heel ulcer. 16 of the 17 cows had ulcers that occurred on the lateral claw of the rear foot. Three cases had mature sole ulcers on one of the lateral hind claws, and early ulcers as evidenced by sole haemorrhage on the lateral claw of the opposite foot. Eight of nine uncomplicated ulcers showed progressive reduction in size following treatment. Using finger pressure, no pain response was present at the ulcer site after one week in 8 of 9 cases (89%). Ulcers with granulating corium healed more slowly (range 41-60 days; mean 48) compared with those where the corium appeared normal (range 12-28 days; mean 20). Sole ulcers recurred in 2 of the 9 cases (22%) within one month after the cow began bearing weight on the affected claw. In one of these cows, ulcers developed on 3 of the 4 hind claws. Histopathological examination of the left rear medial and lateral claws from this cow showed marked changes in the ventral surface of the third phalanx and the dermal papillae, as well as abnormal keratogenesis. Partial tenovaginotomy with resection of the deep flexor tendon was performed in 6 of the complicated sole ulcer cases. In the other 2 cases, tenovaginotomy was followed by claw amputation due to the intraoperative diagnosis of concurrent septic arthritis of the distal interphalangeal joint. In cases of partial tenovaginotomy, healing occurred over a period of 49-81 days (mean 68 days). Complications included excessive granulation tissue, abscess formation of the proximal outer compartment of the digital flexor tendon sheath, and overextension of the toe. For optimal healing to occur, weekly evaluation for the first 4 weeks following treatment may be beneficial with the following objectives: ascertain presence and position of the claw block; determine if progressive healing is occurring; determine if complications may be developing, such as a discharging tract at the ulcer site or swelling of the heel, coronary band or flexor surface of the digit; and finally, recheck for the presence of loose horn overgrowing the ulcer site which may result in further injury to the exposed corium and delay healing.

Complications of tracheobronchial airway stents.

Our goal was to identify and analyze airway stent complications and to devise approaches to manage stent complications. We conducted a retrospective review of patients from a tertiary medical center. Twenty-eight airway stents were placed in 23 patients for benign (n = 15) and malignant (n = 13) tracheobronchial diseases. All patients were followed clinically for signs of complications. Nine complications (8 in those with benign disease and 1 in a patient with malignant disease) were identified and included stent migration (n = 3), excessive granulation tissue (n = 2), stent fracture (n = 1), poor patient tolerance (n = 2), and inability to place (n = 1). Avoidance and management strategies for stent complications are introduced. Tracheobronchial stents provide minimally invasive therapy for significant airway obstruction. Stent complications are more frequently encountered in the long-term treatment of benign conditions. Stents can be successfully removed endoscopically if complications arise, but the longer a metallic stent is in place, the more difficult it is to remove. As airway stent use increases, proper management will be required to avoid and manage complications. This is the first report to focus on stent complications and their management.

Complications of tracheobronchial airway stents

Our goal was to identify and analyze airway stent complications and to devise approaches to manage stent complications. We conducted a retrospective review of patients from a tertiary medical center. Twenty-eight airway stents were placed in 23 patients for benign (n = 15) and malignant (n = 13) tracheobronchial diseases. All patients were followed clinically for signs of complications. Nine complications (8 in those with benign disease and 1 in a patient with malignant disease) were identified and included stent migration (n = 3), excessive granulation tissue (n = 2), stent fracture (n = 1), poor patient tolerance (n = 2), and inability to place (n = 1). Avoidance and management strategies for stent complications are introduced. Tracheobronchial stents provide minimally invasive therapy for significant airway obstruction. Stent complications are more frequently encountered in the long-term treatment of benign conditions. Stents can be successfully removed endoscopically if complications arise, but the longer a metallic stent is in place, the more difficult it is to remove. As airway stent use increases, proper management will be required to avoid and manage complications. This is the first report to focus on stent complications and their management.

STENTING OF THE TRACHEOBRONCHIAL TREE

Endoscopic treatment of endobronchial obstructions is becoming increasingly important. Tracheobronchial stents often are needed in the treatment of obstructions from submucosal or extrabronchial lesions. Tube stents have been available since the early 1960s but are underused because their insertion requires the use of a rigid bronchoscope. With the recent development of metallic stents, interventional radiologists increasingly are involved in the treatment of tracheobronchial obstructions. Metallic stents, easily placed with flexible bronchoscopy, are growing in popularity. All available tracheobronchial stents have been shown in various clinical series to be able to achieve immediate resolution of respiratory symptoms from various tracheobronchial obstructions. A stent's performance, however, should not be based solely on short-term response. Presently, there is no ideal stent because none is free of complications and none are able to consistently maintain life-long patency. Gianturco stents are associated with serious major complications (bronchial perforations and strut fractures) and are no longer recommended for use in the tracheobronchial tree. The Palmaz stent has also fallen into disfavor, because a strong external force, such as a vigorous cough, can recompress it. The Strecker stent can only be used in smaller airways, but may be useful in the accurate stenting of short segment stenoses because it does not foreshorten on deployment. The Wallstent and Ultraflex are our present metallic stents of choice. Both are easy to deploy, available in covered forms, exert adequate radial force, remain relatively stable in position, and have good longitudinal flexibility for use in tortuous airways. Disadvantages include excessive granulation tissue formation and difficulty of removal once the stent has been epithelialized. Metallic stents should be chosen very carefully for use in benign lesions with ongoing active local inflammation or when temporary stenting is needed. In the absence of an ideal stent, technologic advancements will continue. Potential developments include removable metallic stents, biodegradable stents, and chemically and radioactively coated stents. Unquestionably, the expanding stent market will drive scientific research toward the development of the ideal stent. Clearly, physicians need to be ready to assess these technologic advancements.

Tracheobronchial metal stents: Effects of covering a bronchial ostium in pigs

The purpose of this study was to examine the effects of placing a metal stent across a bronchial orifice. Nine pigs were used as test subjects, because the right upper lobe bronchus comes directly off the trachea in these animals. One of three types of metal stents was placed into the trachea of each pig and covered the orifice of the right upper lobe bronchus. Follow-up studies were performed at 1 and 3 months to evaluate the right upper lobe for signs of bronchial obstruction, infection, and atelectasis. The animals were sacrificed at 3 months to study the histopathologic changes of the trachea and lungs. Two upper lobe bronchi remained patent; seven were obstructed by granulation tissue or plugs of mucus and inflammatory cells. Right upper lobe infiltration and atelectasis were seen in eight animals. Interestingly, radiographic opacities were also common in other lung segments. There was a tendency toward fewer and less extensive lung opacities at 3 months compared with that at 1 month. At histopathologic examination, areas of both acute and chronic pneumonia were found in the right upper lobe of all animals. The segment of trachea covered by the stent was lined with a thin layer of granulation tissue containing neutrophils, monocytes, and lymphocytes. The stent luminal surface was covered with columnar, cuboidal, and stratified squamous epithelium. Tracheal stenosis was seen in three animals because of excessive granulation tissue in two and a collapsed stent in one. Placement of metal stents in pig trachea covering the orifice of the right upper lobe bronchus resulted in retention of secretions and secondary infection in the right upper lobe and other distant lung segments.

Use of the aortic homograft in the reconstruction of complex tracheobronchial tree injuries

Background/Purpose: The repair of complex tracheobronchial tree injuries often is associated with complications including stenosis and excessive granulation tissue formation. Patch reconstruction using pericardium or synthetic material decreases the incidence of stenosis. The authors report on the use of the ascending aorta cryopreserved homograft in reconstructing the tracheobronchial tree of three children.Results: A 10 year old had a through-and-through gun shot wound to the left main stem bronchus with cartilaginous loss. A 12 year old double lung transplant recipient had a breakdown of one bronchial anastomosis after stent placement. A 1 year old had an acquired tracheoesophageal fistula secondary to a long standing foreign body. In all three patients, the aortic patches were secured with interrupted sutures. All three had uneventful recoveries, and postoperative bronchoscopy showed the patches to be completely covered with epithelium without stenosis or granulation tissue.Conclusions: This is the first report of the use of the cryopreserved ascending aorta homograft in the reconstruction of the tracheobronchial tree. The homograft is strong yet malleable. It gets completely covered with epithelium and results in no stenosis because of the lack of tension. These characteristics make it an attractive alternative for the patch reconstruction of complex tracheobronchial tree injuries.

The control of new prosthetic implants

The recent well-publicised problem of early failure of the 3M Capital Hip has led both the public and orthopaedic surgeons to question the effectiveness of existing controls in the UK which govern the introduction of new prostheses for joint replacement. It has also resulted in renewed demands for a National Hip Register, similar to those successfully developed by Sweden and Norway, 1,2 to provide better long-term surveillance of different designs of implant. The Scandinavian Registers have certainly been successful in drawing attention to poorly performing prostheses, such as the Christiansen Hip, 3 as well as identifying problems in the materials used for joint replacement, as with ‘Boneloc’ cement. 4,5 Their long-term data confirm that selection of the prosthesis is the factor which has the greatest influence on long-term survivorship. The problem of early failure of the implant is not new, nor is it confined to Europe, since major difficulties have also been reported recently from North America in a number of roughened femoral stems used with acrylic ‘precoat’ technology. 6,7 Should we be able to predict these types of failure? To do so requires a better understanding of the mechanism of early breakdown, which must be different from the wellrecognised late failure resulting from the production of prosthetic wear particles characterised by the formation of excessive granulation tissue and osteolysis. The Capital Hip, which was introduced by the 3M Company in 1991, was marketed as a femoral stem with a shape similar, but not identical, to the current version of the Charnley stem. The emphasis at the time of its introduction was on the low cost of the prosthesis and the outstanding performance of the existing hip replacement based on the Charnley principles. The femoral implant was manufactured in two materials; a modular design with a titanium-alloy stem and either a chrome-cobalt or titaniumnitride head, and a monobloc in stainless steel. A number of stem shapes were available for each of these. Modularity allowed the use of heads of various sizes and different materials. The titanium alloy used for the stem was chosen to give the advantages of a lower modulus of elasticity, better biocompatibility, and reduced tissue toxicity. The stem design featured round corners proximally to ensure a more uniform load transfer to the supporting cement, a slightly roughened matt surface texture, and an acrylic centraliser at its tip. It was inserted using specially designed instruments with broaches and rasps that were oversized by 2 mm to allow a cement mantle of 1 mm around the prosthesis. Between 1991 and 1997 it was estimated that 5000 Capital prostheses were used in the UK, and a further 1000 elsewhere in the world. By 1995 there was some anecdotal evidence of early failures in various centres in the UK. The 3M Company responded by circulating a guidance note recommending extra removal of trabecular bone proximally in order to improve interdigitisation of cement. In 1997 Massoud et al 8 published a paper in the British Volume of the Journal documenting the early rates of failure. In a series of 76 patients with a mean follow-up of just over two years, they reported a revision rate of 9%; 16% of cases had definite radiological loosening and a further 10% possible early loosening. All the femoral stems used in the series were of titanium alloy combined with modular chromecobalt or titanium heads. The authors suggested that the significant increase in the incidence of loosening was associated with an inadequate proximal cement mantle of less than 2 mm thickness. When information emerged from at least four other centres in the UK reporting unacceptably high rates of early revision for the Capital Hip, the Medical Devices Agency (MDA) issued a Hazard Notice in Feb

Evaluation of a New Self-expandable Silicone Stent in an Experimental Tracheal Stenosis

To assess the usefulness of an animal model for testing new tracheobronchial stents. Animal laboratory of a university hospital. In a series with 12 mini-pigs, we induced a stable fibromalacic tracheal stenosis that was 50% to 70% of the normal tracheal diameter. After dilation we inserted a 16 x 40-mm self-expandable silicone stent into the stenotic part of the trachea in 10 of the mini-pigs. Five of the stents had a smooth outer surface, and five had additional silicone retaining spikes. Because of a long stenosis in two of the mini-pigs, two overlapping stents (one smooth and one with spikes) were inserted. Stent deployment was successful and resulted in the disappearance of the slight to moderate stridor in all of the mini-pigs. Over a mean (+/- SD) observation period of 24 days (range, 10 to 41 days), all of the mini-pigs redeveloped stridor. Three of them died unexpectedly of suffocation: in all three a smooth stent had migrated, leading to total obstruction of the stenosis. In total, five of the six smooth stents migrated, and only one of the six spiked stents migrated. There was considerable granulation tissue formation at the ends of all of the stents. In the two control mini-pigs, a 12 x 35-mm Dumon stent was inserted. Both Dumon stents migrated, and one of them had considerable granuloma formation at its ends. At the end of the observation period, all stents were removed endoscopically and were found not to have deteriorated over time. Our model proved to be suitable for the evaluation of the technical aspects of the Polyflex stent. Spikes on the outer stent surface are more effective in preventing migration than smooth-surface stents. Long-term compatibility, however, seems to be difficult to test with our model because both the Polyflex and the Dumon stents had excessive granulation tissue formation at both ends, a factor which--in the case of the Dumon stent--does not occur to such a degree in benign human airway stenoses. Our results indicate a need for prospective long-term studies in benign human airway stenoses.