A comparative study of two types of sternal pins used for sternal closure: poly-l-lactide sternal pins versus uncalcined hydroxyapatite poly-l-lactide sternal pins

Sternal Pin Used to Close Sternum in Infants after Cardiac Surgery

OBJECTIVE

A retrospective study was conducted to explore the efficacy of bioabsorbable poly-L-lactic acid sternal pins in sternal closure in infants after cardiac surgery.

METHODS

A total of 170 infantile patients who underwent cardiac surgery were divided into the steel wire group (group A), the PDS cord group (group B), and the steel wire + sternal pin group (group C). The occurrence of the thoracic deformity was evaluated by vertebral index (VI), frontosagittal index (FSI), and Haller index (HI) values; the stability of the sternum was evaluated by detecting sternal dehiscence and displacement.

RESULTS

By comparing the absolute values of the differences in VI, FSI, and HI in the three groups, it was found that the difference values of VI and HI in group C were significantly lower than those in group B (p = 0.028 and 0.005). For the highest deformation index, the deformation rate of infants in group C before discharge and during the 1-year follow-up was lower than that in group A and group B (p = 0.009 and 0.002, respectively). The incidence of sternal displacement in group C was also significantly lower than that in groups A and B (p = 0.009 and 0.009). During the 1-year follow-up, there was no sternal dehiscence, and the sternum healed completely in the three groups.

CONCLUSION

The use of "steel wire + sternal pin" for sternal closure in infants after cardiac surgery can reduce the occurrence of sternal deformity, reduce anterior and posterior displacement of the sternum, and improve sternal stability.

Sternal closure with sandwiched three-piece bioresorbable mesh reduces postoperative hemorrhage: a retrospective study

BACKGROUND

Median sternotomy is the most performed procedure in cardiac surgery; however, sternal displacement and bleeding remains a problem. This study aimed to investigate whether sternal reconstruction using a sandwiched three-piece bioresorbable mesh plate can prevent postoperative sternal displacement and bleeding more than a bioresorbable pin.

METHODS

Patients (n = 218) who underwent median sternotomy were classified according to whether a sandwiched three-piece bioresorbable mesh plate and wire cerclage (group M, n = 109) or a bioresorbable pin and wire cerclage (group P, n = 109) were used during sternal reconstruction. The causes of postoperative sternal displacement and bleeding with computed tomography data were analyzed and compared between the groups.

RESULTS

The preoperative patient characteristics did not significantly differ between the groups. However, the evaluation of sternal and substernal hematoma on postoperative day 5 using computed tomography showed sternal displacement in 4 (4%) and 22 (20%) patients, and substernal hematoma in 17 (16%) and 41 (38%) patients in groups M and P, respectively; this difference was significant. Furthermore, the amount of bleeding at 6 h postoperatively was lower in group M than in group P (235 ± 147 vs. 284 ± 175 mL, p = 0.0275). Chest reopening, intubation time, and length of intensive care unit and hospital stays did not differ between the groups. The evaluation of substernal hematoma based on computed tomography yielded a significantly lower for group M than for group P, revealing that the mesh plate was an independent predictor of substernal hematoma prevention.

CONCLUSION

Sternal fixation with a three-piece bioresorbable mesh plate could prevent postoperative sternal displacement, bleeding, and substernal hematoma more than sternal fixation with a pin.

Finite Element Analysis of Insertion Angle of Absorbable Screws for the Fixation of Radial Head Fractures

Objective

To investigate the biomechanical effects of different insertion angles of absorbable screws for the fixation of radial head fractures.

Methods

The finite element models used to simulate the fractures were created based on CT scans. Two absorbable screws were used to fix and maintain the stability of the fracture, and the angles between the screws were set to 0°, 15°, 30°, 45°, 60°, 75°, and 90°. A downward force of 100 N was applied at the stress point, which was coupled with the surface, and the distal radius was limited to six degrees of freedom. The direction and location of the applied force were the same in each model. The values of the von Mises stress and peak displacements were calculated.

Results

Under the applied load and different screw angles, the maximum von Mises stress in the screws was concentrated on the surface contacting the fracture surfaces. The maximum von Mises equivalent stress in the screw decreased when the angle increased from 0° (19.54 MPa) to 45° (13.11 MPa) and increased when the angle further increased to 90° (24.63 MPa). The peak displacement decreased as the angle increased from 0° (0.19 mm) to 45° (0.15 mm) and increased when the angle further increased to 90° (0.25 mm).

Conclusion

The computational stress distribution showed that fixation with absorbable screws is safe for patients. Moreover, the minimum von Mises stress and displacements were generated when the angle between the screws was 45°; hence, this setting should be recommended for Mason type II radial fractures.

Corrugated Sheet of Unsintered Hydroxyapatite Poly-L-Lactide for Sternal Fixation: A Preclinical Study

Purpose: To stabilize the sternum after median sternotomy, unsintered hydroxyapatite poly-L-lactide (u-HA/PLLA) sternal pins are frequently used in Japan. However, sternal pins are ineffective in the fragile bone marrow. Thus, a corrugated sheet made of u-HA/PLLA was developed as a new sternal fixation device.

Methods: To examine the effects of the device, we measured the shear force using a sternal model and cadaver. The shear force of the corrugated sheet, sternal pin, and simple wire was compared. The device size was determined after reviewing the sternal computed tomography (CT) of 128 patients.

Results: The shear force of the model with the corrugated sheet (286 [256–295] N) was higher than that with sternal pins (135 [134–139] N, p = 0.03) and simple wire (94 [90–104] N, p = 0.03) at 2-mm displacement. In the cadaver test, the shear force of the sternal halves with the device was about two times higher than that without the device. Retrospective CT showed that 18-mm wide device applies to 99% male and 87% female patients at the fourth intercostal level.

Conclusion: The corrugated sheet might provide a stronger fixation effect in the fragile bone marrow. The device width was modified to 18 mm to be applicable for most Japanese patients.

Sternal wound closure in the current era: the need of a tailored approach

OBJECTIVE

Median sternotomy remains the most common access to perform cardiac surgery procedures. However, the experience of the operating surgeon remains a crucial factor during sternal closure to avoid potential complications related to poor sternal healing, such as mediastinitis. Considering the lack of major randomized controlled trials and the heterogeneity of the current literature, this narrative review aims to summarize the different techniques and approaches to sternal closure with the aim to investigate their reflections into clinical outcomes and to inform the choice on the most effective closure method after median sternotomy.

METHODS

A literature search through PubMed, Embase, EBSCO, Cochrane database of systematic reviews, and Web of Science from its inception up to April 2019 using the following search keywords in various combinations: sternal, sternotomy, mediastinitis, deep sternal wound infection, cardiac surgery, closure.

RESULTS

Single wire fixation methods, at present, seems the most useful method to perform sternal closure in routine patients, although patients with a fragile sternum might benefit more from a figure-of-eight technique. In high-risk patients (e.g. chronic pulmonary disease, obesity, bilateral internal mammary artery harvesting, diabetes, off-midline sternotomy), rigid plate fixation is currently the most effective method, if available; alternatively, weave techniques could be used.

CONCLUSION

The choice among the sternal closure techniques should be mainly inspired and tailored on the patient's characteristics, and correct judgement and experience play a pivotal role. A decisional algorithm has been proposed as an attempt to overcome the absence of specific guidelines and to guide the operative approach. This operative approach might be used also in non-cardiac procedure in which median sternotomy is required, such as in case of thoracic surgery.

Effect of internal fixation of the sternum using bioabsorbable pins in small children

OBJECTIVES

A sternal pin can be used to internally fix the reapproximated sternum after midline sternotomy. This paper will evaluate the effectiveness of using a sternal pin in small children by means of a computer tomography scan.

METHODS

Propensity score matching was performed for patients undergoing a first-time median sternotomy from April 2012 to December 2014 with a follow-up computer tomography scan after 6 months. Seventeen matched patients were selected for both the control and the sternal pin groups. The angle of the sternal reflection at the joint surface was measured by computer tomography scan. In addition, the Haller index was measured at each thoracic vertebral level.

RESULTS

The angle of the sternal reflection was more variable in the control group compared with the sternal pin group: the standard deviation was 31.6° for the control group and 10.2° for the sternal pin group (P value = .0009). Seven out of 17 patients in the control group had a negative angle (excavated sternum) compared with 1 out of 17 in the sternal pin group (P = .0391). In the other patients, the angle was 23.9° ± 3.6° in the control group and 10.1 ± 2.8 in the sternal pin group (P = .0061). The Haller index was also more variable in the control group, and it was significantly different from the sternal pin group at the ninth vertebral level (P = .0409).

CONCLUSIONS

The study demonstrated that the use of a sternal pin was associated with decreased variation in the sternal angles and decreased incidence and severity of sternal protrusion and excavation in small children.

Screening of Osteogenic-Enhancing Short Peptides from BMPs for Biomimetic Material Applications

Bone regeneration is an important issue in many situations, such as bone fracture and surgery. Umbilical cord mesenchymal stem cells (UC-MSCs) are promising cell sources for bone regeneration. Bone morphogenetic proteins and their bioactive peptides are biomolecules known to enhance the osteogenic differentiation of MSCs. However, fibrosis can arise during the development of implantable biomaterials. Therefore, it is important to control cell organization by enhancing osteogenic proliferation and differentiation and inhibiting fibroblast proliferation. Thus, we focused on the screening of such osteogenic-enhancing peptides. In the present study, we developed new peptide array screening platforms to evaluate cell proliferation and alkaline phosphatase activity in osteoblasts, UC-MSCs and fibroblasts. The conditions for the screening platform were first defined using UC-MSCs and an osteogenic differentiation peptide known as W9. Next, in silico screening to define the candidate peptides was carried out to evaluate the homology of 19 bone morphogenetic proteins. Twenty-five candidate 9-mer peptides were selected for screening. Finally, the screening of osteogenic-enhancing (osteogenic cell-selective proliferation and osteogenic differentiation) short peptide was carried out using the peptide array method, and three osteogenic-enhancing peptides were identified, confirming the validity of this screening.

Biomechanical comparison of locking plate and crossing metallic and absorbable screws fixations for intra-articular calcaneal fractures

The locking plate and percutaneous crossing metallic screws and crossing absorbable screws have been used clinically to treat intra-articular calcaneal fractures, but little is known about the biomechanical differences between them. This study compared the biomechanical stability of calcaneal fractures fixed using a locking plate and crossing screws. Three-dimensional finite-element models of intact and fractured calcanei were developed based on the CT images of a cadaveric sample. Surgeries were simulated on models of Sanders type III calcaneal fractures to produce accurate postoperative models fixed by the three implants. A vertical force was applied to the superior surface of the subtalar joint to simulate the stance phase of a walking gait. This model was validated by an in vitro experiment using the same calcaneal sample. The intact calcaneus showed greater stiffness than the fixation models. Of the three fixations, the locking plate produced the greatest stiffness and the highest von Mises stress peak. The micromotion of the fracture fixated with the locking plate was similar to that of the fracture fixated with the metallic screws but smaller than that fixated with the absorbable screws. Fixation with both plate and crossing screws can be used to treat intra-articular calcaneal fractures. In general, fixation with crossing metallic screws is preferable because it provides sufficient stability with less stress shielding.