Bioabsorbable implants: review of clinical experience in orthopedic surgery

Evaluation of biomechanical strength, stability, bioactivity, and in vivo biocompatibility of a novel calcium deficient hydroxyapatite/poly(amino acid) composite cervical vertebra cage

A new type of cervical vertebra cage was prepared using a novel composite, calcium deficient hydroxyapatite/poly(amino acid) (HA/PAA), and its mechanical properties, in vitro stability and bioactivity, and in vivo biocompatibility were characterized. The results showed that the axial compressive loads of the HA/PAA cage were in the range of 10058-10612 N and the lateral compressive loads were in the range of 1180-2363 N, and varied with the height of the cervical vertebra cages. After immersion in simulated body fluid (SBF) for 16 weeks, the axial compressive loads of the cage decreased from 10058 to 7131 N and the lateral compressive loads decreased from 1180 to 479 N. In addition, the weight loss decreased 6.01%, showing that HA/PAA composites had good stability during the incubation period. The pH value of SBF was also monitored during the whole soaking period; it fluctuated in the range of 6.9-7.4. Scanning electron microscope and energy dispersive spectrometer results showed the cage was bioactive with a new apatite layer attached on the surface. The histological evaluation revealed that new bone tissue bonded tightly with the surfaces of the implants, showing excellent biocompatibility. In conclusion, the HA/PAA cage showed sufficient strength, good stability, bioactivity, and biocompatibility, and has potential applications for clinical cervical vertebrae repair.

Painful pretibial pseudocyst at bioabsorbable interference screw aperture two years after anterior cruciate ligament reconstruction

We report the case of a patient with a painful subcutaneous nodule, measuring 13 mm × 17 mm, at the pretibial graft aperture site, which presented two years after a successful anterior cruciate ligament reconstruction with an autologous hamstring graft. A bioabsorbable poly-L-lactide interference screw was used for graft fixation at the tibial aperture. The patient underwent surgical excision of the lesion and curettage at the tunnel aperture. Grossly, extruded fragments of the screw and a thick pseudocapsule of surrounding tissue were excised. There was no communication between the tunnel aperture and the knee joint. The graft was also intact. Histological analysis revealed fragments of the bioabsorbable material in association with fibrous and granulomatous chronic inflammatory cells. This was consistent with a foreign body reaction. The patient subsequently recovered and resumed preinjury level of activity. To the best of our knowledge, this is the first report describing a nodular granulomatous type reaction to foreign bioabsorbable poly-L-lactide screw material subsequent to an anterior cruciate reconstruction surgery.

Degradability and cytocompatibility of tricalcium phosphate/poly(amino acid) composite as bone tissue implants in orthopaedic surgery

In this study, a tricalcium phosphate (TCP) and poly (amino acid) copolymer (PAA) biocomposite were fabricated for bone repair and characterized. The results show that the compressive strength of the TCP/PAA composites increased with an increase in the TCP content at TCP contents less than 40 w%. The weight loss of the composite after soaking in phosphate buffered saline for 12 weeks significantly increased with an increase in the TCP content, revealing its good degradability. In addition, the composite maintained adequate mechanical strength during the degradation period because it underwent a surface erosion process. In vitro MG63 cell culture experiments showed that the composite is non-cytotoxic and thus allows cells to adhere, proliferate and differentiate. Osteoid formation was evidenced on the composite surfaces 12 weeks after its implantation into the femoral bone of dogs. Furthermore, the composite combined directly with the host bone tissue without fibrous capsule tissue, and no inflammatory responses were found, showing the good biocompatibility of the composite. It is expected that the composite may be used for the development of bone implants for orthopaedic surgery.

Degradation mechanisms of bioresorbable polyesters. Part 2. Effects of initial molecular weight and residual monomer

This paper presents an understanding of how initial molecular weight and initial monomer fraction affect the degradation of bioresorbable polymers in terms of the underlying hydrolysis mechanisms. A mathematical model was used to analyse the effects of initial molecular weight for various hydrolysis mechanisms including noncatalytic random scission, autocatalytic random scission, noncatalytic end scission or autocatalytic end scission. Different behaviours were identified to relate initial molecular weight to the molecular weight half-life and to the time until the onset of mass loss. The behaviours were validated by fitting the model to experimental data for molecular weight reduction and mass loss of samples with different initial molecular weights. Several publications that consider initial molecular weight were reviewed. The effect of residual monomer on degradation was also analysed, and shown to accelerate the reduction of molecular weight and mass loss. An inverse square root law relationship was found between molecular weight half-life and initial monomer fraction for autocatalytic hydrolysis. The relationship was tested by fitting the model to experimental data with various residual monomer contents.

Composite scaffolds of nano calcium deficient hydroxyapatite/multi-(amino acid) copolymer for bone tissue regeneration

In this study, nano calcium deficient hydroxyapatite (n-DA)/multi-(amino acid) copolymer composite scaffolds were prepared by injection molding foaming method using calcium sulphate dihydrate as a foaming agent. The composite scaffolds showed well interconnected macropores with the pore size of ranging from 100 to 600 μm, porosity of 81 % and compressive strength of 12 MPa, and the compressive strength obviously affected by the porosity. The composite scaffolds could be slowly degraded in phosphate buffered solution (PBS), which lost its initial weight of 61 w % after immersion into PBS for 12 weeks, and the porosity significantly affected the degradability of the scaffolds. Moreover, it was found that the composite scaffolds could promote the MG-63 cells growth and proliferation, and enhance its alkaline phosphatase activity. The implantation of the scaffolds into the femoral bone of rabbits confirmed that the composite scaffolds were biocompatibitive, degradable, and osteoconductive in vivo.

Evaluation of antibiotic-impregnated microspheres for the prevention of implant-associated orthopaedic infections

BACKGROUND

Prevention of infection associated with uncemented orthopaedic implants could lead to improved implant stability and better patient outcomes. We hypothesized that coating porous metal implants with antibiotic-containing microspheres would prevent infections in grossly contaminated wounds.

METHODS

Bioresorbable polymer microspheres containing tobramycin were manufactured and pressed into porous metal cylinders that were then implanted into radial defects in rabbits. Control implants that did not contain antibiotic microspheres were also implanted into the contralateral limbs. Each implant was then contaminated with Staphylococcus aureus prior to closure of the wound. The animal was euthanized after clinical signs of infection appeared, or at two weeks after surgery. Periprosthetic tissue was cultured for the presence of S. aureus, and integration of the implant with the surrounding bone was measured.

RESULTS

The antibiotic microspheres successfully prevented infection in 100% of the eleven limbs with treated implants, which represented a significant improvement (p = 0.004) compared with the infection rate of 64% (seven of eleven) for the limbs with control implants. Implant integration averaged 38.87% ± 12.69% in the fifteen uninfected limbs, which was significantly better (p = 0.012) than the average of 19.46% ± 14.49% in the seven infected limbs.

CONCLUSIONS

The antibiotic delivery system successfully prevented infection in 100% of the cases studied, resulting in an increase in implant integration.

CLINICAL RELEVANCE

Antibiotic delivery utilizing the system described here may be effective in preventing implant-associated infections after orthopaedic surgery and increasing the longevity of orthopaedic implants.

Operative management of rib fractures in the setting of flail chest: a systematic review and meta-analysis

OBJECTIVE

To perform a systematic review and meta-analysis of studies comparing operative to nonoperative therapy in adult FC patients. Outcomes were duration of mechanical ventilation (DMV), intensive care unit length of stay (ICULOS), hospital length of stay (HLOS), mortality, incidence of pneumonia, and tracheostomy.

BACKGROUND

Flail chest (FC) results in paradoxical chest wall movement, altered respiratory mechanics, and frequent respiratory failure. Despite advances in ventilatory management, FC remains associated with significant morbidity and mortality. Operative fixation of the flail segment has been advocated as an adjunct to supportive care, but no definitive clinical trial exists to delineate the role of surgery.

METHODS

A comprehensive search of 5 electronic databases was performed to identify randomized controlled trials and observational studies (cohort or case-control). Pooled effect size (ES) or relative risk (RR) was calculated using a fixed or random effects model, as appropriate.

RESULTS

Nine studies with a total of 538 patients met inclusion criteria. Compared with control treatment, operative management of FC was associated with shorter DMV [pooled ES: -4.52 days; 95% confidence interval (CI): -5.54 to -3.50], ICULOS (-3.40 days; 95% CI: -6.01 to -0.79), HLOS (-3.82 days; 95% CI: -7.12 to -0.54), and decreased mortality (pooled RR: 0.44; 95% CI: 0.28-0.69), pneumonia (0.45; 95% CI: 0.30-0.69), and tracheostomy (0.25; 95% CI: 0.13-0.47).

CONCLUSIONS

As compared with nonoperative therapy, operative fixation of FC is associated with reductions in DMV, LOS, mortality, and complications associated with prolonged MV. These findings support the need for an adequately powered clinical study to further define the role of this intervention.

Investigation on corrosion protection and mechanical performance of minerals substituted hydroxyapatite coating on HELCDEB-treated titanium using pulsed electrodeposition method

The present work aims to investigate the effects of mineral (strontium, magnesium and zinc) substituted hydroxyapatite (M-HAP) coating on high-energy low-current DC electron beam (HELCDEB)-treated titanium (Ti).

Pre-tibial reaction to biointerference screw in anterior cruciate ligament reconstruction

BACKGROUND

We aim to report a series of cases that presented as pre-tibial swelling and pain following anterior cruciate ligament (ACL) reconstruction using bioabsorbable fixation devices.

METHODS

All ACL reconstructions done between 2007 and 2010 were reviewed retrospectively to identify complications related to bioabsorbable fixation devices. We performed 273 ACL reconstructions over a period of three years from 2007 to 2010 using a bioabsorbable screw for tibial fixation of the quadrupled hamstring autograft.

RESULTS

Fourteen patients (5%) at mean age of 30 (range 16-47) years, presented to us at a mean post-operative period of 26 months (range 12-39) with pre-tibial pain and swelling over the tibial screw site. All of them had normal inflammatory markers. All of these patients underwent surgical debridement, which revealed remnants of screw and reactive material. There was no evidence of infection in the intra-operative specimen cultures. Histopathology revealed a reactive appearance and surrounding myxoid changes. Removal of screw debris and curettage of the tunnel resulted in complete recovery of all patients at a mean follow up of 12 (range 8-16) months.

CONCLUSIONS

Pre-tibial cyst along with other adverse biological response should be considered as a possible complication in ACL reconstruction. We report an incidence of 5% of pre-tibial reaction in patients undergoing ACL reconstruction with bio-absorbable interference screw fixation for the proximal tibia.

Technique for utilization of an interference screw for split peroneus brevis tendon transfer in lateral ankle stabilization

We present a technique for split peroneous brevis lateral ankle stabilization using an interference screw as the fixation device. The interference screw provided stable fixation by way of physiologic tension and restored lateral ankle instability while preserving the range of motion in the surrounding joints.

Influence of micro- and nano-hydroxyapatite coatings on the osteointegration of metallic (Ti6Al4 V) and bioabsorbable interference screws: an in vivo study

The purpose of this study is to show and compare the fixation and osteointegration capability of metallic and bioabsorbable interference screws. For this, 8×20-mm interference screws were implanted into the bone tunnel in the proximal tibial metaphysis of sheep. The nano- (25 nm±0.8) and microscale (25 μm±0.5) hydroxyapatite were both dip-coated on Ti6Al4 V interference screws via an in vivo study. After the initial 12 weeks of postoperative, the pullout test, histopathology, X-ray diffraction and scanning electron microscopy examinations were performed. This multidisiplined work showed that the coated screws particularly those with nano-sized-HA coating and the bioabsorbable screws enhanced fixation and provided better stabilization, bone ingrowth and osteointegration than that of uncoated and microscale HA-coated screws. The bioabsorbable screws showed better histopathologic results.

How smart do biomaterials need to be? A translational science and clinical point of view

Over the last 4 decades innovations in biomaterials and medical technology have had a sustainable impact on the development of biopolymers, titanium/stainless steel and ceramics utilized in medical devices and implants. This progress was primarily driven by issues of biocompatibility and demands for enhanced mechanical performance of permanent and non-permanent implants as well as medical devices and artificial organs. In the 21st century, the biomaterials community aims to develop advanced medical devices and implants, to establish techniques to meet these requirements, and to facilitate the treatment of older as well as younger patient cohorts. The major advances in the last 10 years from a cellular and molecular knowledge point of view provided the scientific foundation for the development of third-generation biomaterials. With the introduction of new concepts in molecular biology in the 2000s and specifically advances in genomics and proteomics, a differentiated understanding of biocompatibility slowly evolved. These cell biological discoveries significantly affected the way of biomaterials design and use. At the same time both clinical demands and patient expectations continued to grow. Therefore, the development of cutting-edge treatment strategies that alleviate or at least delay the need of implants could open up new vistas. This represents the main challenge for the biomaterials community in the 21st century. As a result, the present decade has seen the emergence of the fourth generation of biomaterials, the so-called smart or biomimetic materials. A key challenge in designing smart biomaterials is to capture the degree of complexity needed to mimic the extracellular matrix (ECM) of natural tissue. We are still a long way from recreating the molecular architecture of the ECM one to one and the dynamic mechanisms by which information is revealed in the ECM proteins in response to challenges within the host environment. This special issue on smart biomaterials lists a large number of excellent review articles which core is to present and discuss the basic sciences on the topic of smart biomaterials. On the other hand, the purpose of our review is to assess state of the art and future perspectives of the so called "smart biomaterials" from a translational science and specifically clinical point of view. Our aim is to filter out and discuss which biomedical advances and innovations help us to achieve the objective to translate smart biomaterials from bench to bedside. The authors predict that analyzing the field of smart biomaterials from a clinical point of view, looking back 50 years from now, it will show that this is our heritage in the 21st century.

Complications after tendon transfers in the foot and ankle using bioabsorbable screws

BACKGROUND

Tendon transfers are commonly used for correction of pathology or deformity of the foot and ankle. Bioabsorbable implants have been developed as an alternative to metal interference screws. The purpose of this study was to document complications following tendon transfers of the foot and ankle using bioabsorbable poly-L-lactide interference screws.

METHODS

A retrospective chart review was used to identify patients in whom either of the 2 senior authors had performed a tendon transfer of the foot and ankle using a bioabsorbable interference screw between 1999 and 2005. A minimum of 6 months of follow-up was required for inclusion in the study. In all, 31 patients were identified who met the inclusion criteria with an average follow-up of 75 weeks. All screws were made of poly-L-lactide (PLLA).

RESULTS

Complications were identified in 12 (39%) of patients. All of the complications reported were known complications of the tendon transfer procedure itself, and were not directly related to the bioabsorbable screw.

CONCLUSIONS

Based on these early results, PLLA implants appear safe and effective for tendon transfers of the foot and ankle. However, until long-term outcomes are available, judicious use of these implants is recommended.

Short-term and long-term effects of orthopedic biodegradable implants

Presently, orthopedic and oral/maxillofacial implants represent a combined $2.8 billion market, a figure expected to experience significant and continued growth. Although traditional permanent implants have been proved clinically efficacious, they are also associated with several drawbacks, including secondary revision and removal surgeries. Non-permanent, biodegradable implants offer a promising alternative for patients, as they provide temporary support and degrade at a rate matching tissue formation, and thus, eliminate the need for secondary surgeries. These implants have been in clinical use for nearly 25 years, competing directly with, or maybe even exceeding, the performance of permanent implants. The initial implantation of biodegradable materials, as with permanent materials, mounts an acute host inflammatory response. Over time, the implant degradation profile and possible degradation product toxicity mediate long-term biodegradable implant-induced inflammation. However, unlike permanent implants, this inflammation is likely to cease once the material disappears. Implant-mediated inflammation is a critical determinant for implant success. Thus, for the development of a proactive biodegradable implant that has the ability to promote optimal bone regeneration and minimal detrimental inflammation, a thorough understanding of short- and long-term inflammatory events is required. Here, we discuss an array of biodegradable orthopedic implants, their associated short- and long- term inflammatory effects, and methods to mediate these inflammatory events.

Intramedullary fixation in digital replantation using bioabsorbable poly-DL-lactic acid rods

PURPOSE

To evaluate bioabsorbable poly-DL-lactic acid (PDLLA) intramedullary rods for fracture fixation of amputated digits.

METHODS

From October 2005 to October 2007, we used bioabsorbable rods made of PDLLA as intramedullary fixation in osteosynthesis procedures in 9 cases of digital replantation. Four cases involved the middle phalanx and 5 the proximal phalanx. The amputation level was diaphyseal in all cases. All patients were followed up from 6 months to 2 years, with an average of 13 months.

RESULTS

All fractures healed in 6 to 8 weeks. There were no infections. There was no evidence of hardware failure at 4 weeks after surgery. According to the Tamai et al criteria, the results were excellent in 8 cases and good in 1.

CONCLUSIONS

Using bioabsorbable PDLLA rods for intramedullary fixation can be an effective technique for replantation with fractures through the proximal or middle phalanges. Bioabsorbable rods can provide rigid stable fixation, which allows early mobilization.

Bio-interference screw cyst formation in anterior cruciate ligament reconstruction--10-year follow up

PURPOSE

This study used serial MRI to assess the absorption of a poly l-lactide Bioabsorbable interference screw used in the anterior cruciate ligament reconstruction with a 4-strand hamstring technique.

METHODS

A consecutive series of ten patients undergoing anterior cruciate ligament reconstruction a 4-strand hamstring technique were assessed with magnetic resonance imaging (MRI) scans at 1, 2, 4, 7 and 10 years postoperatively.

RESULTS

No resorption had occurred after 4 years in any of the patients. By 7 years screw absorption was complete in seven patients and had progressed in three. New cyst formation occurred in 3 patients between 5 and 7 years. Half the patients displayed small fluid collections within the tibial tunnels. At 10 years all screws were fully absorbed; however cyst formation was common, including the development of a new cyst in the period between 7 and 10 years in one patient. None of the patients had instability, persistent effusions, or clinically detectable adverse reactions to the screws.

CONCLUSIONS

This study has shown that poly l-lactide bioabsorbable screws take longer to resorb than initial in vitro data suggested. It is unclear whether ganglion formation within the tibial tunnel is related to screw resorption or the hamstring graft. The theoretical advantages of bioabsorbable screws must be weighed against these findings.

Use of bioabsorbable pins in surgical fixation of comminuted periarticular fractures

OBJECTIVES

To determine if bioabsorbable pins can be used for stabilization of comminuted articular fragments in periarticular fractures with adequate quality of fixation, while eliminating the potential complications related to use of traditional implants.

DESIGN

Multicenter retrospective review.

SETTING

Two Level 1 trauma centers.

PATIENTS/PARTICIPANTS

Institutional billing records identified all cases (83) in which bioabsorbable pins were implanted. All charts were reviewed, and all periarticular fracture cases (80 fractures in 78 patients) were included.

INTERVENTION

Open reduction and internal fixation of highly comminuted periarticular fractures, using bioabsorbable poly-p-dioxanone and poly-l-lactic acid pins to stabilize the fragments of articular surface.

MAIN OUTCOME MEASUREMENTS

Outcomes were determined by maintenance of articular reduction assessed at 6 weeks and 3 months; development of posttraumatic arthritis assessed radiographically and by clinical examination at 1 year postoperatively; and rates of local complications including infection, pin migration, and pin-related soft tissue complications evaluated by complete medical record review.

RESULTS

No patients showed loss of articular reduction at 6 weeks or 3 months. There were no pin-related local complications or pin migration and no instances of delayed union or nonunion. Radiographs showed 19% arthritic changes at 12 months, with 16% loss to follow-up. Infection rate was 6%.

CONCLUSIONS

In highly comminuted periarticular fractures, bioabsorbable pins are an intriguing alternative to traditional fixation methods. They afford similar effectiveness in maintaining stability without evidence of pin migration or other concerns of buried metallic implants.

Characterization of MgNd2 alloy for potential applications in bioresorbable implantable devices

The aim of this study is to investigate and demonstrate the mechanical and corrosive characteristics of the neodymium-containing magnesium alloy MgNd2 (Nd2), which can be used as a resorbable implant material, especially in the field of stenting applications. To determine the mechanical characteristics of Nd2, tensile and compression tests were initially carried out in the hot extruded state. Here a unique elongation ratio (~30%) of the alloy could be observed. Subsequent T5 and T6 heat treatments were arranged to reveal their effect on the alloy's strengths and elongation values. The general degradation behaviour of Nd2 in a 0.9% NaCl solution was investigated by means of polarization curves and hydrogen evolution. In addition to this, by using various in vivo parameters, a corrosion environment was established to determine the alloy's degradation in vitro. Here, the mass loss per day in (MgF(2) and Bioglass)-coated and uncoated states and the corresponding maximum forces resulting from subsequent three-point bending tests revealed slow and steady corrosion behaviour. The cell viability and proliferation tests carried out on L-929 and MSC-P5 cells also showed good results. The mechanical and corrosive characteristics determined, as well as the in vitro test results obtained within the scope of this study, led to the development and successful in vivo testing of an MgF(2)-coated Nd2 mucosa stent which was introduced as an appropriate resorbable application.

Bone substitute biomedical material of multi-(amino acid) copolymer: in vitro degradation and biocompatibility

Degradable polymers with good mechanical strength as bone repair biomaterials have been paid more attention in biomedical application. In this study, a multi-(amino acid) copolymer consisting of 6-aminocaproic acid and five natural amino acids was prepared by a reaction of acid-catalyzed condensation. The results revealed that the copolymer could be slowly degradable in Tris-HCl solution, and lost its initial weight of 31.9 wt% after immersion for 12 weeks, and the changes of pH value of Tris-HCl solution were in range from 6.9 to 7.4 during soaking. The compressive strength of the copolymer decreased from 107 to 68 MPa after immersion for 12 weeks. The proliferation and differentiation of MG-63 cells on the copolymer significantly increased with time, and the cells with normal phenotype extended and spread well on the copolymer surfaces. When the copolymer was implanted in muscle and bone defects of femoral cortex of dogs for 12 weeks, the histological evaluation confirmed that the copolymer exhibited excellent biocompatibility and more effective osteogenesis in vivo. When implanted into cortical bone defects of dogs, the copolymer could be combined directly with the natural bone without fibrous capsule tissue between implants and host bone. The results indicated that the multi-(amino acid) copolymer with sufficient strength, good biocompatibility and osteoconductivity had clinical potential for load-bearing bone repair or substitution.

Digital arthrodesis: current fixation techniques

Several hammertoe implant devices have recently been introduced in an attempt to provide optimal fixation for proximal interphalangeal joint arthrodesis. This article reviews these implants individually, and discusses their advantages and disadvantages. There is a lack of research with long-term follow-up available for these devices. Percutaneous Kirschner-wire fixation persists as a time-honored and effective method of fixation. The buried Kirschner-wire technique is also an effective, cost-conscious option, with many of the same advantages as newer implantable devices.

Progressive osteolysis of the radius after distal biceps tendon repair with the bioabsorbable screw

BACKGROUND

Several complications have been reported with the use of the PLLA (poly-L-Lactide) bioabsorbable screw in orthopedic surgery. The hypothesis was that the use of a bioabsorbable screw in distal biceps tenodesis results in significant osteolysis of the radial bone. The correlation between osteolysis and functional and clinical outcomes was also studied.

METHODS

All consecutive patients who underwent anatomic repair of the distal biceps tendon with a bioabsorbable screw were included. From the x-ray taken immediately after the surgery, the ratio between the volume of the bone tunnel and the volume of the radius bone section was measured. This relation was calculated at different follow-up periods to obtain the percentage of tunnel enlargement over time. Complications, as well as functional and clinical outcomes, were also assessed. Mayo Elbow Performance Score (MEPS), the quick-Disability Arm Shoulder Hand (DASH), and the Short-Form 12 (SF-12) were used.

RESULTS

Nineteen consecutive patients were available for follow-up. The average initial relative volume occupied by the screw tunnel was 49% of the bone section and increased to 61% at the last follow-up at an average of 22 months (range, 3-62 months). Eight of the 19 patients presented postoperative complications. There was only 1 case of complete bone filling of the tunnel, which was observed at a 5-year and 2-months follow-up. There was no significant correlation between the volume of bone resorption and functional and clinical outcomes.

DISCUSSION

No correlation was found between the volume of bone tunnel and the functional outcome. However, the results indicate that the use of a bioabsorbable screw in distal biceps tendon repair results in significant bone osteolysis.

Micro Electromechanical Systems (MEMS) Based Microfluidic Devices for Biomedical Applications

Micro Electromechanical Systems (MEMS) based microfluidic devices have gained popularity in biomedicine field over the last few years. In this paper, a comprehensive overview of microfluidic devices such as micropumps and microneedles has been presented for biomedical applications. The aim of this paper is to present the major features and issues related to micropumps and microneedles, e.g., working principles, actuation methods, fabrication techniques, construction, performance parameters, failure analysis, testing, safety issues, applications, commercialization issues and future prospects. Based on the actuation mechanisms, the micropumps are classified into two main types, i.e., mechanical and non-mechanical micropumps. Microneedles can be categorized according to their structure, fabrication process, material, overall shape, tip shape, size, array density and application. The presented literature review on micropumps and microneedles will provide comprehensive information for researchers working on design and development of microfluidic devices for biomedical applications.

In vivo tissue response to ultrasound assisted application of biodegradable pins into cortical and cancellous bone structures: a histological and densitometric analysis in rabbits

In orthopaedic traumatology biodegradable pins are increasingly used for fixation of small bone fragments. In the present study, the ultrasound-assisted anchoring technique (SonicFusion technique), a osteosynthesis method being recently introduced in cranial applications, in which ultrasonic energy is used to insert and anchor polymer pins in bone, was compared with the conventional pin application procedure. The aim of the present study was to assess the short and long term thermal impact of two different ultrasonic energy levels on different bone structures in the distal medial femur of rabbits. The treatment groups consisted of customized polylactide pins applied at a low and a high energy level, the Reference Control and a Negative Control. The thermal effect on bone tissues was evaluated by means of qualitative and semi-quantitative histology and micro-computerized tomography. Five days following surgery, all implant sites showed no tissue damage but normal signs of early ongoing tissue repair. Enhancing the energy level by about 30% had no significant impact on the tissue response. At 4 weeks after surgery test sites covered by ultrasound-aided implantation showed a significantly enhanced bone/implant contact as compared to pins applied by conventional application. In conclusion, the ultrasound assisted anchoring technique not only did not impair bone regeneration, but even improved implant integration.

Operative treatment of chest wall injuries: indications, technique, and outcomes

Most injuries to the chest wall with residual deformity do not result in long-term respiratory dysfunction unless they are associated with pulmonary contusion. Indications for operative fixation include flail chest, reduction of pain and disability, a chest wall deformity or defect, symptomatic nonunion, thoracotomy for other indications, and open fractures. Operative indications for chest wall injuries are rare.

Article Commentary: Rib Fracture Fixation: Controversies and Technical Challenges

Rib fractures are a common injury affecting more than 350,000 people each year in the United States and are associated with respiratory complications, prolonged hospitalization, prolonged pain, long-term disability, and mortality. The social and economic costs that rib fractures contribute to the health care burden of the United States are therefore significant. But despite this measurable impact on patients’ quality of life, current treatment of the majority of patients in the United States with rib fracture syndromes is supportive only. Even the most severe of chest wall injuries have historically been treated non-operatively. Recently, however, several reports from American centers support an increased application of operative fixation. With this resurgent interest of American surgeons in mind, we review the clinical presentations, potential indications, controversies, and technical challenges unique to rib fracture fixation.

Thumb carpometacarpal suspension arthroplasty using interference screw fixation: surgical technique and clinical results

PURPOSE

Arthritis of the thumb carpometacarpal (CMC) joint is a common condition, for which reconstruction using the flexor carpi radialis (FCR) is a standard treatment. We describe the technique and clinical results for thumb CMC arthroplasty using interference screw fixation of the FCR to the first metacarpal through a single incision.

METHODS

Over 12 months, 29 consecutive CMC arthroplasties were performed in 29 patients using FCR transfer tenotomized at the level of the scaphoid with an absorbable biotenodesis screw for fixation. There were 24 women and 5 men, with a mean age of 58 years. Patients were evaluated at a minimum of one year with radiographs, standardized outcome instruments, and measurements of motion and strength. The scaphoid to first metacarpal distance was measured at 2 weeks, 3 months, and greater than 1 year to assess settling.

RESULTS

A total of 28 patients were available at a mean of 19 months. No arthroplasties required revision. Postoperative scaphoid to first metacarpal distance was 5.9 mm, which had decreased by a mean of 1.4 mm at final follow-up. There were no side-to-side differences in range of motion or strength in the entire cohort except for lateral key pinch, which was lower on the reconstructed side. The mean postoperative Disabilities of the Arm, Shoulder, and Hand score was 15, and the mean visual analog scale score was 1. Correlations were found between age and lateral key pinch strength for the reconstructed and contralateral sides. There were no significant relationships among Disabilities of the Arm, Shoulder, and Hand score, visual analog scale, radiographic settling, side-to-side strength or range of motion versus gender, Eaton stage, or workers' compensation status.

CONCLUSIONS

Our series demonstrates excellent clinical outcomes with no revisions at an average of 19 months for this technique. Strength, range of motion, and radiographic settling compare favorably with published results of alternative techniques. Except for lateral key pinch, there was no statistically significant difference in strength compared with the contralateral side.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Fabrication and mechanical properties of PLLA/PCL/HA composites via a biomimetic, dip coating, and hot compression procedure

Currently, the bone-repair biomaterials market is dominated by high modulus metals and their alloys. The problem of stress-shielding, which results from elastic modulus mismatch between these metallic materials and natural bone, has stimulated increasing research into the development of polymer-ceramic composite materials that can more closely match the modulus of bone. In this study, we prepared poly(L: -lactic acid)/hydroxyapatite/poly(epsilon-caprolactone) (PLLA/HA/PCL) composites via a four-step process, which includes surface etching of the fiber, the deposition of the HA coating onto the PLLA fibers through immersion in simulated body fluid (SBF), PCL coating through a dip-coating process, and hot compression molding. The initial HA-coated PLLA fiber had a homogeneous and continuous coating with a gradient structure. The effects of HA: PCL ratio and molding temperature on flexural mechanical properties were studied and both were shown to be important to mechanical properties. Mechanical results showed that at low molding temperatures and up to an HA: PCL volume ratio of 1, the flexural strain decreased while the flexural modulus and strength increased. At higher mold temperatures with a lower viscosity of the PCL a HA: PCL ratio of 1.6 gave similar properties. The process successfully produced composites with flexural moduli near the lower range of bone. Such composites may have clinical use for load bearing bone fixation.

Microneedle-based drug delivery systems: microfabrication, drug delivery, and safety

Many promising therapeutic agents are limited by their inability to reach the systemic circulation, due to the excellent barrier properties of biological membranes, such as the stratum corneum (SC) of the skin or the sclera/cornea of the eye and others. The outermost layer of the skin, the SC, is the principal barrier to topically-applied medications. The intact SC thus provides the main barrier to exogenous substances, including drugs. Only drugs with very specific physicochemical properties (molecular weight < 500 Da, adequate lipophilicity, and low melting point) can be successfully administered transdermally. Transdermal delivery of hydrophilic drugs and macromolecular agents of interest, including peptides, DNA, and small interfering RNA is problematic. Therefore, facilitation of drug penetration through the SC may involve by-pass or reversible disruption of SC molecular architecture. Microneedles (MNs), when used to puncture skin, will by-pass the SC and create transient aqueous transport pathways of micron dimensions and enhance the transdermal permeability. These micropores are orders of magnitude larger than molecular dimensions, and, therefore, should readily permit the transport of hydrophilic macromolecules. Various strategies have been employed by many research groups and pharmaceutical companies worldwide, for the fabrication of MNs. This review details various types of MNs, fabrication methods and, importantly, investigations of clinical safety of MN.

Early clinical experience with a fresh talar transplant inlay allograft for the treatment of osteochondral lesions of the talus

BACKGROUND

Management of osteochondral defects of the talus remains a challenge, and many lesions do not respond to traditional treatments. The use of fresh allografts is a promising alternative.

METHODS

A freehand inlay surgical technique for reconstructing osteochondral defects of the talus with fresh osteochondral allografts fixated with bioresorbable chondral darts is described. A retrospective review of a consecutive series of 15 patients (eight males and seven females; mean age, 42.2 years) with stage IV osteochondral defects who underwent this procedure is presented. Seven patients reported a history of trauma. The mean lesion diameter was 1.7 cm.

RESULTS

Mean follow-up was 1.6 years. The Foot and Ankle Outcome Score subscale mean scores obtained at the most recent follow-up were as follows: 66.0 (pain), 64.8 (other symptoms), 71.2 (activities of daily living), 50.7 (sport and recreation function), and 42.1 (quality of life). Nine lesions had no evidence of lucency, and six demonstrated mild lucency, indicating that no allograft had been absorbed. Most patients exhibited no step-off deformity or arthrosis. No graft-related complications occurred. No subsequent surgical procedures were required.

CONCLUSIONS

Early results suggest that this technique is a viable option for treating large osteochondral defects of the talus, as evidenced by the favorable patient assessment and radiographic outcomes and the lack of postoperative complications and subsequent procedures. Unlike previous allograft techniques, hardware complications did not occur. Based on these results, this technique will continue to be used.

A retrospective follow-up of ankle fracture patients treated with a biodegradable plate and screws

BACKGROUND

Biodegradable fixation implants have been developed to avoid secondary hardware removal. The aim of this study was to retrospectively follow-up ankle fracture patients treated with a biodegradable plate and screws, and to evaluate the clinical outcome and occurrence of complications.

METHODS

Fifty-seven ankle fracture patients treated with biodegradable implants were invited, and a total of 50 were available to participate in this study. The follow-up included a review of each patient's medical records, evaluation of radiographs, fracture reduction classification, and functional scoring.

RESULTS

There were 36 lateral malleolar and 14 bimalleolar fractures. No perioperative complications occurred. Average follow-up time was 17 months. All fractures healed. Fracture alignment was classified as anatomical in 49 patients and good in 1 case. The mean Olerud and Molander functional ankle score at final follow-up was 86. Eight patients had postoperative complications. These included delayed wound healing in 1 case, 3 cases of deep-vein thrombosis, and 4 soft tissue reactions.

CONCLUSIONS

According to the results of this retrospective study, the biodegradable implants used yielded fracture healing and functional results comparable to those previously reported after conventional metal fixation.

The use of a biodegradable mesh plate to augment grafting of an acetabular defect: Laboratory investigation and clinical pilot study

We used a biodegradable mesh to convert an acetabular defect into a contained defect in six patients at total hip replacement. Their mean age was 61 years (46 to 69). The mean follow-up was 32 months (19 to 50). Before clinical use, the strength retention and hydrolytic in vitro degradation properties of the implants were studied in the laboratory over a two-year period. A successful clinical outcome was determined by the radiological findings and the Harris hip score. All the patients had a satisfactory outcome and no mechanical failures or other complications were observed. No protrusion of any of the impacted grafts was observed beyond the mesh. According to our preliminary laboratory and clinical results the biodegradable mesh is suitable for augmenting uncontained acetabular defects in which the primary stability of the implanted acetabular component is provided by the host bone. In the case of defects of the acetabular floor this new application provides a safe method of preventing graft material from protruding excessively into the pelvis and the mesh seems to tolerate bone-impaction grafting in selected patients with primary and revision total hip replacement.

Femoral fracture following knee ligament reconstruction surgery due to an unpredictable complication of bioabsorbable screw fixation: a case report and review of literature

We report an unusual case of femoral fracture from minimal trauma, due to the rapid disappearance of a bioabsorbable interference screw used for reconstruction of the posterolateral corner of the knee. The literature on bone tunnel fractures following knee ligament reconstruction surgery is also reviewed.

Rib fracture repair: indications, technical issues, and future directions

Rib fracture repair has been performed at selected centers around the world for more than 50 years; however, the operative indications have not been established and are considered controversial. The outcome of a strictly nonoperative approach may not be optimal. Potential indications for rib fracture repair include flail chest, painful, movable rib fractures refractory to conventional pain management, chest wall deformity/defect, rib fracture nonunion, and during thoracotomy for other traumatic indication. Rib fracture repair is technically challenging secondary to the human rib's relatively thin cortex and its tendency to fracture obliquely. Nonetheless, several effective repair systems have been developed. Future directions for progress on this important surgical problem include the development of minimally invasive techniques and the conduct of multicenter, randomized trials.

Early experience with biodegradable implants in pediatric patients

We retrospectively studied nine children and adolescents with congenital malformations, large reconstruction after tumor excision, fractures and osteotomies of the upper extremity, and hand trauma with bone and soft tissue defects treated by internal synthesis using a biocopolymer of L- and DL-stereoisomers of lactic acid polymers and trimethylenecarbonate. A total of 52 biodegradable implants were placed in bone. At a minimum followup of 7 months (mean, 17 months; range, 7-22 months), wound healing was uncomplicated; local or systemic inflammatory tissue reactions, foreign body reactions, and infections were not observed. Bone healing was complete. Six biodegradable screws broke during insertion because of inadequate drilling and tapping, and three biodegradable screws had to be replaced because of damage to the screw head during assembly with the screwdriver. Biodegradable copolymers of poly-L-lactic-poly-DL-lactic acid and trimethylenecarbonate can be used safely and effectively for reconstruction and fixation of bone in children and adolescents.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

The unpredictable material properties of bioabsorbable PLC interference screws and their adverse effects in ACL reconstruction surgery

The aim of this study was to look at the clinical outcome of polylactide carbonate (PLC) interference screws in knee ligament reconstruction surgery. We prospectively followed up 59 patients who underwent primary hamstring anterior cruciate ligament (ACL) reconstructions using PLC (Calaxo screw; Smith and Nephew, Andover, MA) screws to secure the graft in the tibial tunnel. The average age was 34 years (range 17-55 years, SD 8.93). Twenty-three (39%) patients presented with complications [synovitis in 15% (nine) patients, prominent tibial swelling in 34% (20) patients and both in seven patients]. In comparison, similar complications were not seen in two groups of 59 age and sex matched patients in whom PLLA (Bio RCI; Smith and Nephew, Andover, MA) screws or Titanium (RCI; Smith and Nephew, Andover, MA) screws were used by the same surgeon. The problems encountered in the PLC screw group did not adversely affect knee stability. Six patients underwent exploration of the tibial tunnel site. A sterile white cheesy substance was removed, leaving an empty tibial tunnel. The ACL graft was found to be well attached to tibial tunnel in all cases. The PLC screw diameter, surface area or tibial tunnel diameter did not have any correlation to the occurrence of complications. Two patients required multiple washouts, one of whom developed a deep infection. The degradation of PLC screws does not follow the gradual and controlled pattern demonstrated in the ovine model. The unpredictable screw degradation, and the reaction to it can lead to serious clinical consequences.

A clinical review of bioabsorbable interference screws and their adverse effects in anterior cruciate ligament reconstruction surgery

Bioabsorbable material screws are widely used in various surgical specialties. One popular application is their use as interference screws in anterior cruciate ligament (ACL) reconstruction surgery. Despite their routine use, a major concern with bioabsorbable materials in surgery has been the incidence of adverse events. Various case reports, series reports and studies in the past years have reported complications specific to the use of bioabsorbable interference screws intra operatively and at different time periods post operatively. The aim of this literature review is to summarize the clinical studies where bioabsorbable screws have been used in ACL reconstruction surgery and in particular to highlight any specific complications and adverse effects related to the use of these materials.

Anti-inflammatory polymeric coatings for implantable biomaterials and devices

Synthetic polymer coatings are used extensively in modern medical devices and implants because of their material versatility and processability. These coatings are designed for specific applications by controlling composition and physical and chemical properties, and they can be formed into a variety of complex structures and shapes. However, implantation of these materials into the body elicits a strong inflammatory host response that significantly limits the integration and biological performance of devices. Biomaterial-mediated inflammation is a complex reaction involving protein adsorption, leukocyte recruitment and activation, secretion of inflammatory mediators, and fibrous encapsulation of the implant. Significant research efforts have focused on modifying material properties using various anti-inflammatory polymeric surface coatings to generate more biocompatible implants. This minireview provides a brief background on the events of biomaterial-mediated inflammation and highlights various approaches used for modifying material surfaces to modulate inflammatory responses. These include both passive and active strategies, such as nonfouling surface treatments and delivery of anti-inflammatory agents, respectively. Novel approaches will be needed to extend the in vivo lifetime and performance of devices and reduce the need for multiple implantation surgeries.