Treatment of pectus excavatum with bioabsorbable polylactide plates: Preliminary results

Polylactide bioabsorbable struts for chest wall reconstruction in a pediatric patient

Chest wall reconstruction after pediatric tumor resection is challenging. Children have unique characteristics related to growth and prosthetic material for reconstruction must be chosen carefully. Poly-L-Lactide (PLA), a bioabsorbable prosthetic material, has been used in the plate form for reconstruction after tumor resection in children. Recently developed PLA struts have been successfully used to reconstruct pediatric chest wall deformities. This is the first description of the use of PLA rib struts to reconstruct chest wall defects after a pediatric chest wall tumor resection.

Metal/polymer composite Nuss bar for minimally invasive bar removal after Pectus Excavatum treatment: FEM simulations

This study aims at assessing the mechanical behavior of a composite metal/polymer bar to be implanted in the retrosternal position, in order to correct chest wall deformities, such as Pectus Excavatum. A 300-mm-long, 12.7-mm-wide, and 3.5-mm-thick Nuss bar was considered, made of different metals and biodegradable polymers, fixed at its extremities, and with a constant force of 250 N applied on its center. Two different geometries for the metal elements to be embedded in the polymeric matrix were tested: in the former, thin metal sheets and in the latter, cylindrical metal reinforcing rods were considered. Finite element method simulation results are reported, in terms of maximum stress and strain of the bar. Furthermore, the maximum stress values obtained by varying metal sheet thickness or rod diameter (and therefore the volumetric percentage of metal within the matrix) for different material combinations are also shown; optimal configuration for the Pectus Excavatum treatment was finally identified for a composite Nuss bar.

A sensorized Nuss bar for patient-specific treatment of Pectus Excavatum

Pectus Excavatum is an anatomical deformation characterized by a depression of the anterior chest wall. Nuss technique (representing the current clinical golden standard) consists in the introduction of a corrective metal bar, in order to raise the sternum in its anatomic natural position. Nowadays, the bar plays purely a mechanical/corrective action and is kept implanted for about three years, supporting up to a maximum force of 250 N. Our study aims at optimizing the procedure of correction, in terms of monitoring the bar effect, minimizing the body response, and facilitating the bar removal. The sensorized Nuss bar prototype inserted in a platform for telemedicine described in this article is able to monitor in vitro pressure data variations, with more than 150 discrete measurements during the operating period. This behavior is promising for future clinical applications, in which the device could be exploited to monitor the forces at work, thus, providing a customized therapeutic protocol, which in turn may optimize the period of implant. The sensorized bar was also provided with a polymeric coating, able to influence human dermal fibroblast behavior in vitro. This highlights the possibility to minimize, in future in vivo applications, tissue fibrotic responses.

Systematic review of surgical treatment techniques for adult and pediatric patients with pectus excavatum

This compares outcome measures of current pectus excavatum (PEx) treatments, namely the Nuss and Ravitch procedures, in pediatric and adult patients. Original investigations that stratified PEx patients based on current treatment and age (pediatric=0-21; adult 17-99) were considered for inclusion. Outcome measures were: operation duration, analgesia duration, blood loss, length of stay (LOS), outcome ratings, complications, and percentage requiring reoperations. Adult implant patients (18.8%) had higher reoperation rates than adult Nuss or Ravitch patients (5.3% and 3.3% respectively). Adult Nuss patients had longer LOS (7.3 days), more strut/bar displacement (6.1%), and more epidural analgesia (3 days) than adult Ravitch patients (2.9 days, 0%, 0 days). Excluding pectus bar and strut displacements, pediatric and adult Nuss patients tended to have higher complication rates (pediatric - 38%; adult - 21%) compared to pediatric and adult Ravitch patients (12.5%; 8%). Pediatric Ravitch patients clearly had more strut displacements than adult Ravitch patients (0% and 6.4% respectively). These results suggest significantly better results in common PEx surgical repair techniques (i.e. Nuss and Ravitch) than uncommon techniques (i.e. Implants and Robicsek). The results suggest slightly better outcomes in pediatric Nuss procedure patients as compared with all other groups. We recommend that symptomatic pediatric patients with uncomplicated PEx receive the Nuss procedure. We suggest that adult patients receive the Nuss or Ravitch procedure, even though the long-term complication rates of the adult Nuss procedure require more investigation.

Minimally invasive thoracic surgery in pediatric patients: the Taiwan experience

Minimally invasive technology or laparoscopic surgery underwent a major breakthrough over the past two decades. The first experience of thoracoscopy in children was reported around 1980 for diagnosis of intrathoracic pathology and neoplasia. Up until the middle of the 1990s, the surgical community in Taiwan was still not well prepared to accept the coming era of minimally invasive surgery. In the beginning, laparoscopy was performed in only a few specialties and only relatively short or simple surgeries were considered. But now, the Taiwan's experiences over the several different clinical scenarios were dramatically increased. Therefore, we elaborated on the experience about pectus excavatum: Nuss procedure, primary spontaneous hemopneumothorax, thoracoscopic thymectomy, and empyema in Taiwan.

Repair of a floating sternum with autologous rib grafts and polylactide bioabsorbable struts in an 18-year-old male

Failed regeneration of costal cartilage after open repair of pectus chest wall deformities can result in a floating sternum. A floating sternum can be repaired by insertion of a rib graft between the rib and sternum, and stabilization with a metal strut. The metal implant is usually removed with a second operation. We report use of bioabsorbable struts to stabilize rib grafts during repair of a floating sternum in an 18-year-old male with a failed open repair of pectus carinatum. He had an uncomplicated peri-operative course. One year later, the sternum had a normal appearance and was sturdy. A second operation for removal of hardware was not necessary.

Pectus excavatum: history, hypotheses and treatment options

Pectus excavatum and pectus carinatum represent the most frequent chest wall deformations. However, the pathogenesis is still poorly understood and research results remain inconsistent. To focus on the recent state of knowledge, we summarize and critically discuss the pathological concepts based on the history of these entities, beginning with the first description in the sixteenth century. Based on the early clinical descriptions, we review and discuss the different pathogenetic hypotheses. To open new perspectives for the potential pathomechanisms, the embryonic and foetal development of the ribs and the sternum is highlighted following the understanding that the origin of these deformities is given by the disruption in the maturation of the parasternal region. In the second, different therapeutical techniques are highlighted and based on the pathogenetic hypotheses and the embryological knowledge potential new biomaterial-based perspectives with interesting insights for tissue engineering-based treatment options are presented.

Preliminary analysis of the forces on the thoracic cage of patients with pectus excavatum after the Nuss procedure

BACKGROUND

The Nuss procedure corrects pectus excavatum using a pre-bent bar that generates stress on the chest wall. To investigate the biomechanical effects after the Nuss procedure, we designed a three-dimensional finite element analysis model to analyze the distribution of stress and strain induced in the chest wall.

METHODS

Three patients with pectus excavatum aged 8, 7, and 7 years, were enrolled in this study. The greatest upward displacements of their sternums after the operation were measured from computed tomography images and chest X-ray films. Based on these displacements, we constructed three finite element analysis models for analyzing biomechanical changes in the thoracic cage after the Nuss procedure.

FINDINGS

The simulation results indicated that greatest strain occurred at the third through seventh cartilages, especially where they join the sternum and ribs. A high bilateral stress distribution was also found over the backs of the third to the seventh ribs near the vertebral column.

INTERPRETATION

The stress and strain induced by the Nuss procedure can be analyzed using our finite element analysis model. Although the stress and strain may have some influence on chest and spine development, a more detailed finite element analysis model is recommended for future study to improve the accuracy of our simulation results.

Early Failure of Bioabsorbable Anterior Cervical Fusion Plates

STUDY DESIGN

Case report with forensic failure analysis.

OBJECTIVE

To determine the failure modes of 3 explanted 70:30 PLDLA Mystique (Medtronic Sofamor Danek, Memphis, TN) graft containment plates retrieved from revision surgery for early device failure.

SUMMARY OF BACKGROUND DATA

To reduce the problems of stress-shielding and radiopacity associated with metallic systems, bioabsorbable polymers have been used in anterior cervical discectomy and fusion procedures. Degradation of mechanical properties in vivo is a major concern when using bioabsorbable systems. Three of 6 patients who underwent anterior cervical discectomy with instrumented fusion, using Mystique graft containment systems experienced early failure requiring revision to alternate hardware.

METHODS

Devices were retrieved after failure and analyzed by light microscopy and environmental scanning electron microscopy. Simulations were performed with an unused plating system to induce damage for comparison with the retrieved devices. A detailed case review was performed to identify possible sources of extraordinary loading or damage.

RESULTS

One plating system failed at 6 weeks postimplantation due to fatigue fracture of the screws. Crack initiation sites were identified at the interface of the thread root and mold line of the screw. Another plating system failed at 16 weeks postimplantation due to the coalescence of radial microcracking between holes in the plate, leading to catastrophic failure of the plate. The final plating system failed during the implantation surgery, when the screw fractured in torsion.

CONCLUSIONS

Stress concentrations at the screw head-shaft interface and thread-shaft interface reduce the fatigue performance of bioabsorbable screws. Hydrolysis of the polymer may also play a role in the reduction of resistance to crack initiation and propagation.

The new 4DDome prosthesis: an original light and partially absorbable composite mesh for hernia repair

INTRODUCTION

The use of non-absorbable meshes for the repair of inguinal hernias has become standard; however, these meshes have been associated with complications including long-term postoperative pain. To this end, a new partially absorbable composite mesh has been developed, and the aim of this study was to investigate its efficacy in animal and human trials.

MATERIALS AND METHODS

Sixty male Wistar rats were used to evaluate the behavior of the newly designed composite mesh. Composite meshes were implanted in the extra-peritoneal plane for 2, 4 and 8 weeks and compared to a standard polypropylene mesh. Forty patients with symptomatic inguinal hernias were treated using a new 4DDome designed prosthesis. Follow-up was by clinical and ultrasound examination at 1, 6 and 12 months.

RESULTS

The animal study demonstrated that the inflammatory reaction associated with the new composite mesh was significantly lower than a standard polypropylene mesh, characterized by a lower macrophage infiltrate (P < 0.001). The mesh did not shrink over the 8-week period, unlike the polypropylene mesh (P < 0.05). The human study showed that there were three minor postoperative complications, no recurrences and the mesh was well tolerated. Follow-up with serial ultrasound showed that at 10 days and 1 month the dome was clearly visible in position; however, by 6 months it had flattened out, been partially absorbed and become incorporated into the repair.

CONCLUSION

These experimental and clinical studies have validated the concept of the new 4DDome composite mesh. It was well tolerated and was associated with good short-term results. The combination of the dome shape and the new composite mesh means that less polypropylene is required and represents a significant advance in anterior hernia repair.

Absorbable plates for rib fracture repair: preliminary experience

BACKGROUND

Absorbable prostheses are currently used in a variety of bone reconstructions and fixations.

METHODS

This is a case series of rib fracture fixation using absorbable plates and screws consisting of 70:30 poly(L-lactide-co-D,L-lactide) from April 2001 through November 2002.

RESULTS

Ten patients underwent rib fracture fixation with absorbable plates and screws. Indications included flail chest with failure to wean (five patients), acute pain with instability (four patients), and chest wall defect (one patient). All patients with flail chest weaned from mechanical ventilation successfully. All patients with pain and instability reported rapid subjective improvement or resolution. The patient with a chest wall defect repair returned to full athletic activity without limitations at 6 months. Thoracoscopic assistance was used in three cases and muscle-sparing incisions were used in eight cases. Two patients with screw fixation only developed loss of rib fracture reduction. One patient developed a wound infection requiring drainage. The period of follow-up ranged from 3 to 18 months.

CONCLUSION

Absorbable plates produce good clinical results and are an option for rib fracture repair. Two-point fixation (screw fixation plus suture cerclage) is required. Further refinements in technique should focus on minimally invasive methods.