Faculty Bibliography

The aim of this study was to evaluate mechanically and morphologically the effect of a specific peptide sequence P-15, when incorporated into implant surfaces. Three types of implants were used for the study: Group A: commercially pure titanium implant (blasted and acid etched) + electrochemical thin calcium phosphate deposition, Group B: commercially pure titanium implant (blasted and acid etched) + electrochemical thin calcium phosphate deposition + P-15 incorporation, and as control, Group C: commercially pure titanium implant (blasted and acid etched). After a topographical characterization, transcortical osteotomies were made, and all implant groups (102 implants per group) were randomly placed bilaterally in the tibiae of adult beagle dogs (n = 24). At, 1, 2, and 4 weeks post-surgery, the animals were sacrificed and the samples were retrieved for removal torque tests, for nano indentation, and for histomorphometrical analysis. The results (mean +/- 95% CI) showed that Group B (34.4 +/- 8.7%) presented statistically higher bone-to-implant contact than the other groups (A = 23.9 +/- 7.8%; C = 21.7 +/- 8.3%) at 1 week, indicating an enhanced osteogenesis due to the peptide incorporation. The results suggested that the incorporation of P-15 to implant surfaces increased its bioactivity and the effects were notable especially in the early stages of the healing process. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013.

This in vivo study investigated the in vivo performance of two newly developed synthetic bone substitutes and compared them to commercially available xenografts (Bio-Oss, Geistlich Pharma AG, Switzerland; OsteoGraf, Dentsply, USA). The materials were tested in a rabbit calvaria model, and the bone forming properties were observed at 4 and 8 weeks after implantation by means of histomorphometry and micro computed tomography (micro-CT). Defects without any graft material were used as negative controls. Micro-CT showed that all materials tested presented new bone formation that filled the defects at both time points, whereas the negative control presented less bone formation, with soft tissue infiltration into the defects. Comparable bone fill percentages were observed for histomorphometric and micro-CT results. Even though no statistically significant difference was found quantitatively between all of the bone graft substitute groups, a higher mean decrease in graft material filling the defects, along with higher remodelling activity, was evident for the experimental materials compared to the commercially available xenografts at 8 weeks. The results indicate that the experimental materials possess high degradability, along with osteoconduction comparable to commercially available xenografts.

OBJECTIVES: The aim of the study was to introduce a novel three-dimensional (3D) method to quantify the relative amount of different tissue components in bone substitute-treated defects by means of integration of confocal laser imaging into micro-computed tomography (muCT) analysis. MATERIALS AND METHODS: One standardized semisaddle intraosseous defect was prepared in the mandibles of six minipigs and scanned by an optical scanner to capture the surface of the fresh defect in a 3D manner. Subsequently, all the defects were filled with a biphasic calcium phosphate material. The animals were divided into two groups of three animals each, which were allowed to heal for 3 and 8 weeks, respectively. muCT analysis followed the two healing periods and was performed on all defect locations. The data from optical scanning and muCT were used for three-dimensional evaluation of bone formation, nonmineralized tissue ratio, and graft degradation. The integration of confocal laser scanning into muCT analysis through a superimposition imaging procedure was conducted using the software Amira (Mercury Computer Systems, Chelmsford, MA, USA). RESULTS: The feasibility of combining the confocal imaging into muCT data with regard to obtaining accurate 3D quantification was demonstrated. The amount of tissue components was identified and quantified in all the investigated samples. Quantitative analysis demonstrated that a significant increase in the amount of bone filling the defect was observed in vivo (p < 0.02) while a significant decrease in the amount of nonmineralized tissue occurred (p < 0.04). No difference in the amount of residual grafting material was detected between 3 and 8 weeks in vivo (p > 0.38). CONCLUSIONS: The combination of confocal imaging and micro-computed tomography techniques allows for analysis of different tissue types over time in vivo. This method has revealed to be a feasible alternative to current bone regeneration quantification methods. CLINICAL RELEVANCE: Assessment of bone formation in a large animal model is a key step in assessing the performance of new bone substitute materials. Reliable and accurate methods are needed for the analysis of the regenerative potential of new materials.

PURPOSE: The aim of this study was to assess the effect of implant coating with laminin-1 on the early stages of osseointegration in vivo. MATERIALS AND METHODS: Turned titanium implants were coated with the osteoprogenitor-stimulating protein, laminin-1 (TL). Their osteogenic performance was assessed with removal torque, histomorphometry, and nanoindentation in a rabbit model after 2 and 4 weeks. The performance of the test implants was compared with turned control implants (T), alkali- and heat-treated implants (AH), and AH implants coated with laminin-1. RESULTS: After 2 weeks, TL demonstrated significantly higher removal torque as compared with T and equivalent to AH. Bone area was significantly higher for the test surface after 4 weeks, while no significant changes were detected on the micromechanical properties of the surrounding bone. CONCLUSIONS: Within the limitations of this study, our results suggest a great potential for laminin-1 as a coating agent. A turned implant surface coated with laminin-1 could enhance osseointegration comparable with a bioactive implant surface while keeping the surface smooth.

OBJECTIVES: To evaluate the influence of instrumentation technique on the early osseointegration histomorphometrics and biomechanical fixation of fully laser-etched microgrooves implant surfaces in a sheep model. MATERIAL AND METHODS: Six sheep were subjected to bilateral hip surgeries 3 and 6 weeks before euthanasia. A total of 48 implants (slashed circle4.5 mm, 8 mm in length) were distributed among four sites (8 per animal) and placed in bone sites drilled to 4.6 mm (reamer), 4.1 mm (loose), 3.7 mm (medium) and 3.2 mm (tight) in diameter. After healing, the animals were euthanized and half of the implants were biomechanically tested, while the remainder was subjected to non-decalcified histologic processing. The histomorphometric parameters assessed were bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). Statistical analysis was performed using a mixed-model analysis of variance with significance level set at P < 0.05. RESULTS: A general increasing trend is present from 3 to 6 weeks for most of the variables. The groups prepared to be press fit seemed to present higher values, which were maintained throughout the observation period. The reamer group presented the lowest BIC probably due to the drilling technique; however qualitatively, more new bone seemed to be in contact to the implant surface, at 3 weeks, whereas the implants placed in press-fit situations were mainly supported by cortical bone. CONCLUSION: The laser-etched microgrooved implant presented osteoconductive and biocompatible properties for all surgical procedures tested. However, procedures providing increasingly higher press-fit scenarios presented the strongest histomorphometric and biomechanical responses at 3 and 6 weeks.

Application of recombinant human bone morphogenetic protein-2 (rhBMP-2) to implant surfaces has been of great interest due to its osteoinductive potential. However, the optimal coating methodology has not been clarified. The objective of the study was to determine whether the application of rhBMP-2 onto plasma-sprayed hydroxyapatite implant surfaces by immersion in protein solution prior to implant installation would result in significantly improved bone apposition. Using a sheep iliac model, titanium (Ti) and plasma-sprayed calcium phosphate coated (PSCaP) implants uncoated and coated with rhBMP-2 were assessed for their osteogenic effects in the peri-implant area over time in terms of osseointegration and de novo bone formation. After 3 and 6 weeks post-operatively, the samples were retrieved and were subjected to bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) evaluation. When rhBMP-2 was applied to the PSCaP surface, significant increases in BIC and BAFO were observed at 3 weeks in vivo, whereas when adsorbed directly onto the titanium implant surface, rhBMP-2 did not as effectively improve the bone response (although significantly higher than control Ti). The outcomes of the present study suggested that the combination of plasma-sprayed calcium phosphate surface and rhBMP-2 coating significantly enhanced osseointegration, which validated the postulated hypothesis.

PURPOSE: Local anesthetic is often used for perioperative pain control. Thrombin serves as a carrying medium for sustained release of antibiotics, chemotherapy, and growth factors. We tested the hypothesis that local anesthetic pain relief can be prolonged with the adjunct use of thrombin. METHODS: A prospective single-blinded clinical study was performed. Patients undergoing elective hand surgery inclusive of carpal tunnel release, excision of ganglion cyst, trigger finger release, and excision of mucous cyst under local block were enlisted. Before closure, patients received 1 of the following combinations: (1) control with oral analgesics, (2) 5 mL of 2% xylocaine, (3) 5 mL of 0.5% bupivacaine, (4) 2.5 mL of 2% xylocaine with 2.5 mL of 0.5% bupivacaine (XB), (5) thrombin with 5 mL of 2% xylocaine (XT), (6) thrombin with 5 mL of 0.5% bupivacaine (BT), and (7) thrombin with 2.5 mL of 2% xylocaine and 2.5 mL of 0.5% bupivacaine (XBT). There were 7 patients in each group, and patient demographics were similar between groups. Outcome measures included postanesthesia care unit (PACU) time, pain level, and number of pain pills required. RESULTS: Compared with oral analgesics alone, mean (SD) postoperative pain levels were reduced by 33.3% (8.9%) by xylocaine, 69.1% (8.7%) by bupivacaine, and 45.7% (9.4%) by XB. When thrombin was added, pain levels were further reduced by 69.9% by XT (P < 0.001), 23.1% by BT (P = 0.071), and 50.5% by XBT (P < 0.001) compared with their nonthrombin counterparts. In addition, PACU time was decreased by 34.8% by XT (P = 0.003) and 19.7% by XBT (P = 0.013) compared with xylocaine and XB, respectively. However, there was no difference in total pain pills needed between xylocaine, bupivacaine, and XB when administered with and without thrombin. CONCLUSIONS: The addition of topical thrombin to local anesthetic at the end of elective hand surgery provides for sustained postoperative pain control. Patients in this study who received thrombin and local anesthetic before wound closure had lower pain levels and were discharged from the PACU sooner than those who received local anesthetic alone. LEVEL OF EVIDENCE: Therapeutic level 2.

BACKGROUND: Tendon gliding is key to optimal recovery of hand function after complex tendon injuries. Gliding is facilitated by a low-friction gliding surface that is normally provided by the periosteum of the underlying bone. However, significant injuries may damage the periosteum, which must be reconstructed to allow uninterrupted tendon excursion. The absence of the periosteum may compromise a tendon's ability to glide freely, thereby limiting the range of motion. METHODS: Six digits in 4 patients with complex, composite soft tissue defects involving tendon, periosteum, and skin of the hand underwent surgical repair. Each digit had disruption of the bony cortex underlying the tendon injury including periosteal loss. Through an incision on the dorsum of the ipsilateral wrist, an extensor retinaculum graft corresponding to the size of the periosteal defect was harvested. It was then sutured into place over the bare cortex to replace the lost periosteum. RESULTS: All the 6 digits in the 4 patients had complete return to function. Additionally, all patients had near normal strength in the repaired hand along with excellent tendon excursion in both flexion and extension. The average time of follow-up of this series of patients was 1.5 years. CONCLUSIONS: Extensor retinaculum grafting to replace lost periosteum is a technique that is easily used, uses locally available autogenous tissues, and produces excellent tendon function. Additionally, the histologic similarities between extensor retinaculum and periosteum add scientific merit to this novel approach. On the basis of our experience, we recommend the use of extensor retinaculum for periosteal reconstruction to provide an adequate gliding surface for a reconstructed tendon.

BACKGROUND: Iatrogenic pneumothorax is a serious intraoperative complication of immediate breast reconstruction with tissue expanders. However, there is paucity of literature regarding incidence or management of intraoperative pneumothorax in the breast reconstruction patient population. METHODS: We performed a retrospective chart review on prospectively collected data from all patients undergoing immediate breast reconstruction with tissue expanders from 1992 to 2012 to determine institutional incidence. We also searched the Nationwide Inpatient Sample database from 1998 to 2008 to determine national incidence. RESULTS: A total of 9653 tissue expanders were placed in 6955 patients at the Memorial Sloan Kettering Cancer Center between 1992 and 2012. There were 3 cases of pneumothorax during immediate breast reconstruction with tissue expanders. The incidence of pneumothorax is 0.03% per expander and 0.04% per patient. From the national database, there were 153 cases of pneumothorax during immediate breast reconstruction with tissue expanders in 27,612 patients. The overall national incidence of pneumothorax is 0.55% per patient. CONCLUSIONS: Our algorithm for management includes a thoracic surgery consultation intraoperatively. A chest tube should be placed at a site distal to the pleurotomy. The site of injury should be repaired primarily or patched as necessary. If the patient remains stable, it is safe to proceed with placement of the tissue expander.

BACKGROUND: It has been reported that titanium-zirconium alloy with 13-17% zirconium (TiZr1317) implants show higher biomechanical stability and bone area percentage relative to commercially pure titanium (cpTi) grade 4 fixtures. PURPOSE: This study aimed to determine whether the higher stability for TiZr1317 implants is associated with higher mechanical properties of remodeling bone in the areas around the implants. MATERIALS AND METHODS: This study utilized 36 implants (n = 18: TiZr1317, n = 18: cpTi), which were placed in the healed ridges of the mandibular premolar and first molar of 12 mini pigs (n = 3 implants/animal). After 4 weeks in vivo, the samples were retrieved, and resin-embedded histologic sections of approximately 100 mum in thickness were prepared. In order to determine the nanomechanical properties, nanoindentation (n = 30 tests/specimen) was performed on the bone tissue of the sections under wet conditions with maximum load of 300 muN (loading rate: 60 muN/s). RESULTS: The mean (+/- standard deviation) elastic modulus (E) and hardness (H) for the TiZr1317 group were 2.73 +/- 0.50 GPa and 0.116 +/- 0.017 GPa, respectively. For the cpTi group, values were 2.68 +/- 0.51 GPa and 0.110 +/- 0.017 GPa for E and H, respectively. Although slightly higher mechanical properties values were observed for the TiZr1317 implants relative to the cpTi for both elastic modulus and hardness, these differences were not significant (E = p > 0.75; H = p > 0.59). CONCLUSIONS: The titanium-zirconium alloy used in this study presented similar degrees of nanomechanical properties to that of the cpTi implants.