Fixation Strength Research Articles

Double-Incision Technique for the Treatment of Distal Biceps Tendon Rupture.

A longitudinal antecubital incision of 3 to 4 cm allows dissection to identify and isolate the lateral antebrachial cutaneous nerve (LABCN). Supination of the forearm protects the posterior interosseus nerve, which often cannot be visualized. The distal portion of the distal biceps should be carefully identified and exposed. A high-resistance nonresorbable suture is sewn with use of a Krackow technique to whipstitch the distal 4 cm of the tendon. Alternatively, 2 sutures (4 strands) can be utilized. A curved forceps is placed in the interosseous space to identify the location for the second 4-cm incision, on the dorsal proximal forearm over the tip of the forceps with the forearm pronated. The radial tuberosity is exposed by bluntly separating the common extensor tendons, followed by transection of the supinator fibers. Two drill holes are made 5 mm apart from one another for suture passage. The tendon is passed across a loop of wire, from the anterior to the posterior incision. With the elbow at 90° of flexion and full pronation, the tendon is docked into the trough and the sutures are tied. Alternatively, the surgical repair of the distal biceps tendon rupture can be performed through a single anterior approach4. The exposure starts with a curved longitudinal antecubital incision, exploiting the interval between the brachioradialis and pronator teres with radial (lateral) retraction of the brachioradialis and medial retraction of the pronator teres. A single anterior incision allows repair through the use of various types of fixation devices, such as suture anchors, cortical buttons, and interference screws, but seems to carry an increased risk of neurological complications, especially in terms of paresthesias in the distribution of the LABCN. Nonoperative treatment might be acceptable for elderly patients with poor functional demands. The double-incision technique with bone-tunnel fixation provides good fixation strength with an expected low rate of neurological complications1. This approach offers a useful treatment option for young and active patients with physically demanding lifestyles. The double-incision technique is an effective and safe procedure to restore elbow functionality in patients with distal biceps tendon rupture. A meta-analysis1,4-16 revealed no significant differences in postoperative functional scores following procedures performed via the single-incision compared with double-incision approach. Although the differences were smaller than the minimal clinically important difference17, the single-incision technique yielded significantly greater flexion (mean ± standard deviation, 136° ± 13°) and pronation range of motion (79° ± 10°) compared with the double-incision technique (133° ± 13° and 75° ± 14°, respectively) at 2 years postoperatively. No differences in extension and supination were observed. Rates of heterotopic ossification ranged from 0.5% to 11% for the single-incision approach and from 1% to 21.4% for the double-incision approach, with significant differences favoring the single-incision technique, although in the majority of cases the heterotopic ossification was an incidental finding. Neurological complications were found in 24.5% and 13.4% cases for the single- and double-incision techniques, respectively, with a significant difference favoring the double-incision technique. When damage to specific nerves was evaluated, the double-incision technique was associated with significantly less risk of LABCN damage. One or 2 high-resistance nonresorbable sutures are sewn with use of a Krackow technique to whipstitch the distal 4 cm of the biceps tendon.A curved forceps is placed in the interosseous space to identify the location for the second incision, on the dorsal proximal forearm over the tip of the forceps.Pronation of the forearm protects the posterior interosseus nerve, which often cannot be visualized during volar dissection and bone fixation.Positioning the tendon more posteriorly on the radial tuberosity allows for optimal biomechanical function. ROM = range of motionCR = conventional radiologyMRI = magnetic resonance imagingUS = ultrasoundLABC = lateral antebrachial cutaneousPIN = posterior interosseous nerveHO = heterotopic ossificationCI = confidence intervalSI = single incisionDI = double incision.

The Plug-Type Patch Results in Immediate and Postoperative Advantages in Graft-to-Bone Integration for Bridging Massive Rotator Cuff Tears in a Chronic Rabbit Model

Background: Various patches have been used to bridge massive rotator cuff tears (MRCTs) by reconnecting the cuff tendons to the humeral head, but the outcomes continue to be suboptimal. Notably, the graft-bone junction is a vulnerable site for failure, which requires optimization in patch design and techniques to enhance initial and postoperative fixation strength at the graft-bone interface. Hypothesis: The plug-type patch (Plug-Pat) through intratunnel fixation would optimize mechanical characteristics in initial graft-to-bone fixation and subsequently improve postoperative biomechanical and histological properties in graft-to-bone healing when compared with the routine rectangular patch (Rect-Pat). Study Design: Controlled laboratory study. Methods: A total of 60 mature male New Zealand White rabbits underwent acute rotator cuff defects to create chronic models with MRCTs. The fascia lata autograft was then harvested to prepare a Plug-Pat, which was distally rooted in the bone tunnel and proximally sutured to native tendons in a horizontal mattress fashion to reconnect the humeral head and cuff tendons. The control group was repaired with a routine Rect-Pat that was secured onto the bone surface for graft-bone fixation. After surgery, the cuff-graft-bone complexes of rabbits in both groups were harvested immediately (0 weeks) for time-zero initial fixation strength and refreshed contact area assessment, and at 6 or 12 weeks for postoperative biomechanical and histological evaluation. Results: The Plug-Pat significantly enhanced initial fixation strength in comparison with the Rect-Pat (mean ± SD; failure load, 36.79 ± 4.53 N vs 24.15 ± 2.76 N; P < .001) and decreased failure at the graft-bone interface of the construct at 0 weeks, with a significantly increased refreshed bone bed contact area (52.63 ± 2.97 mm2 vs 18.28 ± 1.60 mm2; P < .001) between the graft and bone. At 6 and 12 weeks postoperatively, the Plug-Pat similarly resulted in greater failure load (43.15 ± 4.53 N vs 33.74 ± 2.58 N at 6 weeks; P = .001; 76.65 ± 5.04 N vs 58.17 ± 5.06 N at 12 weeks; P < .001) and stiffness (10.77 ± 2.67 N/mm vs 8.43 ± 0.86 N/mm at 6 weeks; P = .066; 16.98 ± 2.47 N/mm vs 13.21 ± 1.66 N/mm at 12 weeks; P = .011), with less specimen failure at the graft-bone interface than the Rect-Pat. In histological analyses, the Plug-Pat had a higher postoperative graft-bone integration score than the Rect-Pat, showing a more mature intratunnel healing interface with fibrocartilage tidemark formation, improved collagen properties, and more oriented cells when compared with those at the surface healing interface in the Rect-Pat. Conclusion: The Plug-Pat enhanced initial fixation strength and enlarged the refreshed contact area for graft-bone connection at time zero and subsequently improved postoperative biomechanical properties and graft-bone integration at the graft-bone healing interface when compared with the Rect-Pat. Clinical Relevance: The Plug-Pat using intratunnel fixation may be a promising strategy for patch design to optimize its initial and postoperative graft-bone connection for bridging reconstruction of MRCTs.

Novel Dual-Threaded Pedicle Screws Provide Fixation Stability That Is Comparable to That of Traditional Screws with Relative Bone Preservation: An In Vitro Biomechanical Study

Replacement with larger diameter screws is always used in pedicle screw loosening but carries a risk of pedicle wall violation. A pedicle screw with more preserved bone stock is the preferred primary fixation choice. The purpose of this study was to evaluate whether a newly designed proximal-conical dual-thread screw with less bone occupancy provides fixation strength comparable to that of a traditional screw. Six types of pedicle screws based on three different shapes (cylindrical, conical, and proximal-conical) and two thread profiles (single-thread and dual-thread) were grouped. Conical and proximal-conical screws differed mainly in the slope of the outer diameter from the hub to the tip. Conical screws had an outer diameter (6.5 mm) that differed from the hub and tapered by 30% to an outer diameter (4.5 mm) at the tip and proximal-conical screws had the same outer diameter from the hub and tapered by 30% (4.5 mm) at 20 mm from the hub and then maintained the outer diameter (45 mm) to the tip. A total of 36 L4 Sawbones® vertebrae were used in the study and six trials for each screw group. The results of the imaging, screw volume in bone, insertion torque, and pullout force were analyzed. For screws with the same shape, insertion torque and pullout force were significantly higher for those in the dual-thread groups than for those in the single-thread groups (p &lt; 0.05). For screws with the same thread profile, there was no significant difference in either biomechanical test between the different screw shapes (p &gt; 0.05). Our results demonstrated that these proximal-conical dual-thread screws, with the property of relative bone stock preservation, display a comparable biomechanical performance to traditional dual-thread screws and a better performance than single-thread screws. This screw design could serve as the primary pedicle screw choice to reduce revision difficulty.

Percutaneous cortical bone trajectory screw fixation versus traditional open pedicle screw fixation for type A thoracolumbar fractures without neurological deficit.

Retrospective matched-cohort comparative study. Cortical bone trajectory screw (CBT) technique is a new insertion technique in terms of fixation strength and less invasiveness. The purposes of this study were to compare the clinical and radiological outcomes of percutaneous CBT fixation (PCBT) with traditional open posterior pedicle screw fixation (OPPS) technique. Between September 2019 and October 2020, patients undergoing posterior stabilization were matched for age, sex, diagnosis, fractured level, and AO classification. 24 control patients with OPPS were identified and appropriately matched to 24 consecutive patients with PCBT technique. Clinical outcomes and radiographic assessments including vertebral wedge angle (VWA) and sagittal index were recorded and compared between the two groups. Incision length, intraoperative blood loss and hospital stay in the PCBT group were significantly better than the OPPS group (P < 0.05). The VAS scores 5days after operation for PCBT patients were significantly lower than those for OPPS patients (P = 0.003), but these differences lost significance at last follow-up. There was no significant difference in VWA and sagittal index between OPPS and PCBT group (P > 0.05). While no complications were noted in the PCBT group, there were four cases with complications in the traditional OPPS group. The present study showed that PCBT is a safe and feasible method for the treatment of thoracolumbar fractures without neurological deficits. This new surgical treatment was more minimally invasive, yet yielded equivalent or superior clinical and radiographic outcomes compared to the traditional open pedicle screw fixation surgery.

The effect of onlay cortical fibula strut grafts on biomechanical features of Vancouver type B1 periprosthetic femoral fractures.

This study aimed to investigate biomechanically the effects of onlay fibula grafts on Vancouver Type B1 Periprosthetic Femoral Fractures (PPFs). Vancouver Type B1 PFF models were created in 25 fourth-generation synthetic femurs and fixed with locking plates using bicortical, unicortical screws, and cables. While no graft was used in group 1, onlay fibula grafts were placed anteriorly in group 2 and medially in group 3. In group 4, the cortical strut allograft was placed on the medial femoral cortex, and a locking compression plate (LCP) was applied to the lateral femoral cortex. In group 5, the strut allograft was placed over the anterior cortex of the femur and fixed with the same technique as in group 4. All models were then subjected to rotational and axial cyclical stiffness tests and load to failure to measure and compare the mechanical strengths of the constructs. The mean stiffness values of group 4 with medial allograft, before and after cyclical loading, were higher than all other groups, under both rotational and axial forces. The mean stiffness values of fibula autografts (groups 2 and 3) were similar to that of anterior allografts (group 5) in each test except that the mean initial axial stiffness of group 5 was higher than group 2. Failure loads were also not different between the groups. Although the rigidity of Vancouver type B1 periprosthetic femur fractures is highest if allografts are placed medially, fibula autografts can also provide similar fixation strengths to allografts if locking plates with unicortical and bicortical screws and cables are used.

Chitranjan S. Ranawat Award: Motion During Total Knee Cementing Significantly Decreases Tibial Implant Fixation Strength.

Aseptic tibial loosening following primary total knee arthroplasty persists despite technique and device-related advancements. The mechanisms for this mode of failure are not well understood. We hypothesized that knee movement while the cement was curing dispersed lipids at the implant-cement interface and would result in decreased tibial fixation strength. A cadaveric study was performed utilizing 32 torso-to-toe specimens (64 knees). Four contemporary total knee arthroplasty designs were evaluated. Each implant design was randomly assigned to a cadaveric specimen pair with side-to-side randomization. Specimen densitometry was recorded. Each tibial implant was cemented using a standard technique. On one side, the tibial component was held without motion following impaction until complete cement polymerization. The contralateral knee tibial implant was taken through gentle range of motion and stability assessment 7 minutes after cement mixing. Axial tibial pull-out strength and interface failure examination was performed on each specimen. The average pull-out strength for the no motion cohort (5,462 N) exceeded the motion cohort (4,473 N) (P= .001). The mean pull-out strength between implant designs in the no motion cohort varied significantly (implant A: 7,230 N, B: 5,806 N, C: 5,325 N, D 3,486 N; P= .007). Similarly, the motion cohort inter-implant variance was significant (P ≤ .001). Intra-implant pull-out strength was significantly higher in implant A than D. The average pull-out strength was significantly lower in specimens that failed at the implant-cement interface vs bone failures (4,089±2,158 N vs 5,960±2,010 N, P < .0025). Knee motion during cement polymerization is associated with significant decreases in tibial implant fixational strength. Reduction in implant pull-out strength was identified with each implant design with motion and varied between designs. Across all tested designs, we recommend limiting motion while cementing the tibial implant to improve fixation strength.

Effects of groundwater level decline to soil and vegetation in arid grassland: a case study of Hulunbuir open pit coal mine.

Coal mine in arid and semi-arid area is one of the most severely degraded ecosystems on the earth. The continuous decrease in groundwater level caused by coal mining will inevitably affect biogeochemical environment of the vadose zone, and then lead to the replacement of surface vegetation. Yimin open-pit coal mine was taken as an example to reveal the relationship between the groundwater depth and soil water content (SWC), soil salt content, soil electrical conductivity (SEC), soil organic matter (SOM), soil available potassium (SAK), soil available nitrogen (SAN), vegetation coverage, aboveground biomass and species richness. The results show that, the change of groundwater depth can affect soil properties and then change the characteristics of surface vegetation, and the change of surface vegetation can also react on soil properties. Vegetation coverage and aboveground biomass are negatively correlated with groundwater depth, and positively correlated with SWC, SEC, SOM and SAK. The shallow groundwater table is conducive to the accumulation of SOM, so that the surface biomass and vegetation coverage are high. The higher the surface biomass, the more the SAN is absorbed. Under natural conditions, the relative strength of biological nitrogen fixation and plant absorption determine the content of SAN. In the research area, when the depth of groundwater is less than 0.4m will cause soil salinization, then lead to low species richness; Species richness is exponentially correlated with groundwater depth and decreases with the increase in groundwater depth.

Suture tension band fixation vs. metallic tension band wiring for patella fractures – A biomechanical study on 19 human cadaveric patellae

PurposeTraditional tension band fixation of patella fracture is associated with high reoperation rates. The purpose of the study was to assess strength of fixation in patella fractures treated with either a non-metallic all suture-based technique or traditional metallic tension band wiring. MethodsTen paired human cadaveric specimens were included. A transverse fracture was created, reduced and fixated with a non-metallic or metallic approach. Non-metallic fixation was done according to a previously published technique, metallic fixation was done according to AO description. Specimens were fixed in 90° of flexion and underwent 200 cycles of loading by pulling the Quadriceps tendon to 300 Newton. Fracture displacement was optically monitored. Primary outcome was fracture displacement after 200 cycles compared to the first cycle. Subsequently, load-to-failure was assessed by a monotonic pull to 1000 N. ResultsFor cyclic loading analysis, one specimen from each group was excluded due to machine synchronization, resulting in a total population of 18 specimens. Median (min-max) fracture displacement was 0.65 mm (0.06-1.3) in the non-metallic group and 0.68 mm (0-1.23), (p=0.931) in the metallic group. No difference in displacement was found between the two groups in the repeated measures analysis of variance (p=0.5524). For load-to-failure analysis one specimen was excluded due to machine synchronization, resulting a total population of 19 specimens. 2/9 specimens failed in the non-metallic group (at 979 and 635 N) and 2/10 failed in the metallic group (745 and 654 N). ConclusionNon-metallic technique is a biomechanically viable alternative to traditional tension band fixation and it can hopefully lead to fewer implant-related complications.

Endurance Behavior of Cemented Tibial Tray Fixation Under Anterior Shear and Internal-External Torsional Shear Testing: A New Methodological Approach

BackgroundEarly total knee arthroplasty failures continue to surface in the literature. Cementation technique and implant design are two of the most important scenarios that can affect implant survivorship. Our objectives were to develop a more suitable preclinical test to evaluate the endurance of the implant-cement-bone interface under anterior shear and internal-external (I/E) torsional shear testing condition in a biomechanical sawbones. MethodsImplants tested included the AS VEGA System PS and the AS Columbus CR/PS (Aesculap AG, Germany), with zirconium nitride (ZrN) coating. Tibial implants were evaluated under anterior shear and I/E torsional shear conditions with 6 samples in 4 test groups. For the evaluation of the I/E torsional shear endurance behavior, a test setup was created allowing for clinically relevant I/E rotation with simultaneous high axial/tibio-femoral load. The test was performed with an I/E displacement of ±17.2°, for 1 million cycles with an axial preload of 3,000 N. ResultsAfter the anterior shear test an implant-cement-bone fixation strength for the AS VEGA System tibial tray of 2,674 ± 754 N and for the AS Columbus CR/PS tibial tray of 2,177 ± 429 N was determined (P = .191). After I/E rotational shear testing an implant-cement-bone fixation strength for the AS VEGA System PS tray of 2,561 ± 519 N and for the AS Columbus CR/PS tray of 2,824 ± 515 N was resulted (P = .39). ConclusionBoth methods had varying degrees of failure modes from debonding to failure of the sawbones foam. These two intense biomechanical loading tests are more strenuous and more representative of clinical activity.

Biomechanical properties of a suture anchor system from human allogenic mineralized cortical bone matrix for rotator cuff repair

BackgroundSuture anchors (SAs) made of human allogenic mineralized cortical bone matrix are among the newest developments in orthopaedic and trauma surgery. Biomechanical properties of an allogenic mineralized suture anchor (AMSA) are not investigated until now. The primary objective was the biomechanical investigation of AMSA and comparing it to a metallic suture anchor (MSA) and a bioabsorbable suture anchor (BSA) placed at the greater tuberosity of the humeral head of cadaver humeri. Additionally, we assessed the biomechanical properties of the SAs with bone microarchitecture parameters.MethodsFirst, bone microarchitecture of 12 fresh frozen human cadaver humeri from six donors was analyzed by high-resolution peripheral quantitative computed tomography. In total, 18 AMSAs, 9 MSAs, and 9 BSAs were implanted at a 60° angle. All three SA systems were systematically implanted alternating in three positions within the greater tuberosity (position 1: anterior, position 2: central, position 3: posterior) with a distance of 15 mm to each other. Biomechanical load to failure was measured in a uniaxial direction at 135°.ResultsMean age of all specimens was 53.6 ± 9.1 years. For all bone microarchitecture measurements, linear regression slope estimates were negative which implies decreasing values with increasing age of specimens. Positioning of all three SA systems at the greater tuberosity was equally distributed (p = 0.827). Mean load to failure rates were higher for AMSA compared to MSA and BSA without reaching statistical significance between the groups (p = 0.427). Anchor displacement was comparable for all three SA systems, while there were significant differences regarding failure mode between all three SA systems (p < 0.001). Maximum load to failure was reached in all cases for AMSA, in 44.4% for MSA, and in 55.6% for BSA. Suture tear was observed in 55.6% for MSA and in 22.2% for BSA. Anchor breakage was solely seen for BSA (22.2%). No correlations were observed between bone microarchitecture parameters and load to failure rates of all three suture anchor systems.ConclusionsThe AMSA showed promising biomechanical properties for initial fixation strength for RCR. Since reduced BMD is an important issue for patients with chronic rotator cuff lesions, the AMSA is an interesting alternative to MSA and BSA. Also, the AMSA could improve healing of the enthesis.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12891-022-05371-0.

The effect of additional staple in the tibial fixation of anterior cruciate ligament reconstruction: a biomechanical study in sheep tibia

Objectives: The aim of this study was to evaluate the necessity of staple use and the importance of screw diameter in the anterior cruciate ligament (ACL) reconstruction. Methods: Twenty-eight sheep hind legs were divided into four groups in terms of tibial side fixation type as 7 mm bioabsorbable screw (Group 1), 7 mm bioabsorbable screw and staple (Group 2), 8 mm screw (Group 3), and 8 mm screw and staple (Group 4). The maximum force causing insufficiency in the graft, and the fixation strength between the groups were recorded. The results were compared among the groups. Results: As a result of the statistical analysis regarding the necessity of using staple, group 2, with 7 mm screws and staple, was found to be significantly more resistant than group 1 (p = 0.018). In consequence of the biostatistics study, staple use was found not to create a statistically significant difference between group 3 in which an 8 mm bioabsorbable screw was used and group 4 (p = 0.805). In the statistical study to understand the significance of screw diameter, the samples of group 1 and group 3, in which no staple was used, were compared. It was found that group 3 samples with 8 mm screws had higher strength than those with 7 mm screws (p = 0.011). Between group 2 and group 4 in which a staple was used, despite the increase in screw diameter, the value of maximum strength had no remarkable difference statistically (p = 1.00). Conclusions: Fixation strength is higher when fixation was done with a screw 1 mm larger than tibial tunnel diameter. However, using either a screw with 1 mm wider than tibial tunnel diameter and the screw in the same diameter with the tibial tunnel and additional staple have similar fixation strength on the tibial side. Therefore, we conclude that screw width is more important in maintaining stability of the graft fixation.

Determination of a neurologic safe zone for bicortical S1 pedicle screw placement

BACKGROUND CONTEXTLumbosacral fixation is commonly used for the management of lumbosacral instability. As the sacrum mainly consists of cancellous bone, bicortical fixation, in which the pedicle screw penetrates the anterior sacral cortex, can help increase the strength of fixation. However, this method carries a risk to the L5 nerves which lie anterior to the sacrum at this level. PURPOSEThe goal of this study is to determine a safe zone for the placement of S1 pedicle screws to decrease the likelihood of L5 nerve injury. STUDY DESIGNRetrospective imaging review. PATIENT SAMPLEThis study evaluated imaging data of patients who underwent lumbar spine magnetic resonance imaging (MRI) at our institute between September 1, 2020 and September 1, 2021. OUTCOME MEASUREST1-weighted axial MRIs were measured at the level of S1 pedicle screw placement. The space medial and lateral to the L5 nerve root on the anterior sacrum were measured and defined as safe zones. Additionally, the nerve width and sacral lengths were measured at this level. METHODSThe distribution of the measurements were evaluated to determine a medial and lateral safe zone, as well as the average nerve width at the level of S1 pedicle screw placement. Correlation analysis was performed to determine a relationship between safe zone sizes and sacral size. RESULTSA total of 400 MRIs were analyzed. The average medial safe zone measured was 32.8 mm (95% CI: 32.2–33.4) with no nerves lying within 22.3 mm of the midline sacrum. The average lateral safe zone measured was 17.7 mm (95% CI: 17.1–18.2), with no nerves within 5.3 mm of the lateral border of the sacrum. The average nerve root width was 6.2 mm (95% CI: 6.13–6.34). An increased sacral length was associated with a larger medial (p<.001) and lateral (p<.001) safe zone. CONCLUSIONSOur study revealed lateral and medial safe zones for the placement of S1 pedicle screws to avoid iatrogenic nerve injury in a retrospective cohort of 400 patients. There were no L5 nerve roots found within 22.3 mm of the sacrum's mid-axis or within 5.3 mm of the sacrum's anterolateral border. These defined safe zones can be used during pedicle screw planning and placement to decrease the risk of injury to the L5 nerve root.

Effect of Pore Size of Porous-Structured Titanium Implants on Tendon Ingrowth.

Purpose The reconstruction of a tendon insertion on metal prostheses is a challenge in orthopedics. Of the available metal prostheses, porous metal prostheses have been shown to have better biocompatibility for tissue integration. Therefore, this study is aimed at identifying an appropriate porous structure for the reconstruction of a tendon insertion on metal prostheses. Methods Ti6Al4V specimens with a diamond-like porous structure with triply periodic minimal surface pore sizes of 300, 500, and 700 μm and a porosity of 58% (designated Ti300, Ti500, and Ti700, respectively) were manufactured by selective laser melting and were characterized with micro-CT and scanning electron microscopy for their porosity, pore size, and surface topography. The porous specimens were implanted into the patellar tendon of rabbits. Tendon integration was evaluated after implantation into the tendon at 4, 8, and 12 weeks by histology, and the fixation strength was evaluated with a pull-out test at week 12. Results The average pore sizes of the Ti300, Ti500, and Ti700 implants were 261, 480, and 668 μm, respectively. The Ti500 and Ti700 implants demonstrated better tissue growth than the Ti300 implant at weeks 4, 8, and 12. At week 12, the histological score of the Ti500 implant was 13.67 ± 0.58, and it had an area percentage of type I collagen of 63.90% ± 3.41%; both of these results were significantly higher than those for the Ti300 and Ti700 implants. The pull-out load at week 12 was also the highest in the Ti500 group. Conclusion Ti6Al4V implants with a diamond-like porous structure with triply periodic minimal surface pore size of 500 μm are suitable for tendon integration.

Additive Effect of Parathyroid Hormone and Zoledronate Acid on Prevention Particle Wears-Induced Implant Loosening by Promoting Periprosthetic Bone Architecture and Strength in an Ovariectomized Rat Model.

Implant-generated particle wears are considered as the major cause for the induction of implant loosening, which is more susceptible to patients with osteoporosis. Monotherapy with parathyroid hormone (PTH) or zoledronate acid (ZOL) has been proven efficient for preventing early-stage periprosthetic osteolysis, while the combination therapy with PTH and ZOL has exerted beneficial effects on the treatment of posterior lumbar vertebral fusion and disuse osteopenia. However, PTH and ZOL still have not been licensed for the treatment of implant loosening to date clinically. In this study, we have explored the effect of single or combined administration with PTH and ZOL on implant loosening in a rat model of osteoporosis. After 12 weeks of ovariectomized surgery, a femoral particle-induced periprosthetic osteolysis model was established. Vehicle, PTH (5 days per week), ZOL (100 mg/kg per week), or combination therapy was utilized for another 6 weeks before sacrifice, followed by micro-CT, histology, mechanical testing, and bone turnover examination. PTH monotherapy or combined PTH with ZOL exerted a protective effect on maintaining implant stability by elevating periprosthetic bone mass and inhibiting pseudomembrane formation. Moreover, an additive effect was observed when combining PTH with ZOL, resulting in better fixation strength, higher periprosthetic bone mass, and less pseudomembrane than PTH monotherapy. Taken together, our results suggested that a combination therapy of PTH and ZOL might be a promising approach for the intervention of early-stage implant loosening in patients with osteoporosis.

Design and characterization of a novel braided biodegradable double‐J ureteral stent

AbstractUreteral stents in current clinical use are non‐degradable and have a large degree of curling at the ends. This end curling can cause discomfort to patients as well as renal or bladder irritation. In this study, a braided degradable ureteral stent was designed and characterized to eliminate these problems. Eight‐, 12‐, and 16‐strand poly(lactide‐co‐ε‐ caprolactone) (PLCL) monofilament‐braided degradable ureteral stents were prepared, and their tensile performance, radial support performance, in vitro degradation, fixation performance, bending resistance performance, and drainage performance were tested. Compared with the commonly used polyurethane (PU) stent, the tensile strengths of the three types of PLCL stents were higher, with the 12‐strand monofilament‐braided stent exhibiting the highest tensile strength (~508.06 MPa). In terms of radial support, the three PLCL stents meet clinical requirements. After repeated crimping‐rebounding of the braided stent, the support force recovery rate of the 12‐strand monofilament‐braided stent was the best, reaching 92%. In vitro degradation results showed that the 12‐strand stent still maintained good radial support after 8 weeks. The fixation strength of a 12‐strand monofilament‐braided stent with a single loop on the J‐shaped end meets clinical requirements. Even after repeated bending, the 12‐strand monofilament‐braided stent can maintain the stability of the structure with excellent drainage performance.

Degradation of internal fixation materials based on antibacterial and absorbable silk containing different gentamicin concentrations.

Adding gentamicin to silk fibroin enhances both the antibacterial performance and degradation rate of silk-based materials. The increased material degradation rate can affect the strength of early internal fixation, resulting in internal fixation failure. This study sought to adjust the gentamicin concentration to control the material degradation rate, thereby better meeting clinical application requirements. The in vitro degradation, water absorption rate, and expansion rate of silk-based materials containing different gentamicin concentrations were studied. A gentamicin-loaded silk-based screw was implanted into the femurs of New Zealand rabbits. Micro-computed tomography was used to measure the screw diameter, which was then used to calculate the degradation rate. The specimens were stained with hematoxylin and eosin and Masson's trichrome. The in vitro results revealed increasing material degradation rates with increasing gentamicin concentration but no significant differences in water absorption rates with different gentamicin concentrations. The degradation rates of gentamicin-loaded (4mg/g) silk-based rod-like materials were approximately 11.08% at three months in vitro and 9.4% in the animal experiment. The time for complete degradation was predicted from the fitting curve to be approximately 16months. No inflammatory hyperplasia was observed in bone or soft tissue. The degradation and biocompatibility of the material containing 4mg/g gentamicin meet clinical application requirements, and previous experimental results demonstrate good antibacterial performance of materials containing this gentamicin concentration.

A finite element study of a fractured tibia treated with a unilateral external fixator: The effects of the number of pins and cortical thickness

IntroductionIn the early stage of fracture fixation, the aim of a unilateral external fixator (UEF) to stimulate healing and maintain stability may be suppressed by using inadequate number of pins. Cortical thinning due to age or osteoporosis endangers a successful fracture fixation. Materials and methodsThis study evaluates the initial strength and stability of the fracture fixation and tissue differentiation under the influences of variable cortical thickness (5 mm to 1 mm) and variable number of pins (1 to 4 in each bone fragment). A finite element program was utilised to develop 20 three-dimensional models of simplified diaphyseal tibia with fracture callus fixed with UEF. A mechano-regulation code based on the deviatoric strain theory was written and applied to simulate tissue differentiation. The values of von Mises stress, interfragmentary strain (IFS), and fibrocartilage index (FCI) were evaluated. ResultsCortical thinning from 5 mm to 1 mm increased IFS and FCI by an average of 30.3% and 18.7%, respectively, and resulted in higher stresses in the UEF and bone. Using 1 pin in each bone fragment produced excessive IFS in the models with 1 mm, 2 mm and 3 mm cortical thickness. Inserting the second pin into the bone fragment could considerably reduce the IFS and fibrocartilaginous tissue formation in the fracture site and improve load transmission to the fixator. Whereas inserting the fourth pin could minimally affect the mechano-biological environment of healing. ConclusionsThis study suggests that initial instability due to cortical thinning can be efficiently alleviated by adding the number of pins up to 3 in a UEF; additionally, it may improve the knowledge about applying UEFs adequately stable, whilst promoting inclination toward endochondral ossification, simultaneously.

Hydroxyapatite Use in Spine Surgery—Molecular and Clinical Aspect

Hydroxyapatite possesses desirable properties as a scaffold in tissue engineering: it is biocompatible at a site of implantation, and it is degradable to non-toxic products. Moreover, its porosity enables infiltration of cells, nutrients and waste products. The outcome of hydroxyapatite implantation highly depends on the extent of the host immune response. Authors emphasise major roles of the chemical, morphological and physical properties of the surface of biomaterial used. A number of techniques have been applied to transform the theoretical osteoconductive features of HAp into spinal fusion systems—from integration of HAp with autograft to synthetic intervertebral implants. The most popular uses of HAp in spine surgery include implants (ACDF), bone grafts in posterolateral lumbar fusion and transpedicular screws coating. In the past, autologous bone graft has been used as an intervertebral cage in ACDF. Due to the morbidity related to autograft harvesting from the iliac bone, a synthetic cage with osteoconductive material such as hydroxyapatite seems to be a good alternative. Regarding posterolateral lumbar fusion, it requires the graft to induce new bone growth and reinforce fusion between the vertebrae. Hydroxyapatite formulations have shown good results in that field. Moreover, the HAp coating has proven to be an efficient method of increasing screw fixation strength. It can decrease the risk of complications such as screw loosening after pedicle screw fixation in osteoporotic patients. The purpose of this literature review is to describe in vivo reaction to HAp implants and to summarise its current application in spine surgery.

Does augmentation increase the pull-out force of symphyseal screws? A biomechanical cadaver study

PurposeOpen reduction and internal fixation using anterior plate osteosynthesis currently represents the gold standard for the treatment of symphyseal disruptions. Since postoperative screw loosening with consequent implant failure is frequently observed, this study aims to evaluate if and to what extent augmentation can increase the pull-out force of symphyseal screws to improve the constructs stability.MethodsTwelve human cadaveric anterior pelvic rings were separated at the symphyseal joint for bilateral testing, consequently achieving comparable sites. First, one non-augmented screw was drilled into the superior pubic ramus, whereas the contralateral side was primarily augmented. The screws were then withdrawn with a constant speed of 10 mm/min and the fixation strengths determined by the force (N) displacement (mm) curve. Finally, the primary non-augmented site was secondary augmented, representing revision surgery after initial implant failure, and the corresponding fixation strength was measured again.ResultsAugmentation compared to non-augmented screws displayed significantly higher pull-out forces with an increase in pull-out force by 377% for primary and 353% for secondary augmentation (p < 0.01). There was no significant difference in the pull-out force comparing primary and secondary augmentation (p = 0.74).ConclusionsPrimary and secondary augmentation significantly increases the stability of symphyseal screws and, therefore, potentially decreases rates of implant failure.

Histologic and biomechanical evaluation of the thoracolumbar fascia graft for massive rotator cuff tears in a rat model.

Fascial autografts, which are easily available grafts, have provided a promising option in patients with massive rotator cuff tears. However, no fascial autografts other than the fascia lata have been reported, and the exact healing process of the fascia-to-bone interface is not well understood. The objective of this study is to histologically and biomechanically evaluate the effect of the thoracolumbar fascia (TLF) on fascia-to-bone healing. A total of 88 rats were used in this study. Eight rats were killed at the beginning to form an intact control group, and the other rats were divided randomly into 2 groups (40 rats per group): the TLF augmentation group (TLF group) and the repair group (R group). The right supraspinatus was detached, and a 3 × 5 mm defect of the supraspinatus was created. The TLF was used to augment the torn supraspinatus in the TLF group, whereas in the R group, the torn supraspinatus was repaired in only a transosseous manner. Histology and biomechanics were assessed at 1, 2, 4, 8, and 16 weeks postoperatively. The modified tendon maturation score of the TLF group was higher than that of the R group at 8 weeks (23.00 ± 0.71 vs. 24.40 ± 0.89, P = .025) and 16 weeks (24.60 ± 0.55 vs. 26.40 ± 0.55, P ≤ .001). The TLF group showed a rapid vascular reaction, and the peak value appeared at 1 week. Later, the capillary density decreased, and almost no angiogenesis was observed at 8 weeks postoperatively. Immunohistochemistry results demonstrated a significantly higher percentage of collagen I in the TLF group at 4, 8, and 16 weeks (24.78% ± 2.76% vs. 20.67% ± 2.11% at 4 weeks, P = .046; 25.46% ± 1.77% vs. 21.49% ± 2.33% at 8 weeks, P= .026; 34.77% ± 2.25% vs. 30.01% ± 3.17% at 16 weeks, P = .040) postoperatively. Biomechanical tests revealed that the ultimate failure force in the TLF group was significantly higher than that in the R group at the final evaluation (29.13 ± 2.49 N vs. 23.10 ± 3.47 N, P = .022). The TLF autograft can promote a faster biological healing process and a better fixation strength. It could be used as an alternative reinforcement or bridging patch when the fascia lata is not appropriate or available for superior capsule reconstruction (SCR).