Biomechanical performance of a collagen meniscus implant with regard to suture material and irrigation fluid

Background

The role of meniscus scaffolds remains controversial as failure rates remain high. The aim of this study was to evaluate the pullout strength of different suture materials used for fixation of the Collagen Meniscus Implant (CMI) regarding different suture materials, and type or temperature of irrigation fluid.

Comparison of biomechanical analysis of four different tibial tunnel fixations in a bovine model

BackgroundTo determine the ideal fixation technique for an ACL reconstruction with a hamstring graft, multiple studies have been undertaken to define the initial biomechanical properties of tibial fixation.PurposeThe aim of this study was to compare the biomechanical properties of tibial fixation methods by creating single or hybrid systems.MethodsBovine tibias and forefoot digital extensor tendons were prepared with four different tibial anterior cruciate ligament fixation methods and compared biomechanically. Fixation materials included polyethylene Ultrabraid high-strength sutures, Biosure interference screws (Smith and Nephew, Memphis, TN, USA), staples (Smith and Nephew, Richards Regular Fixation Staples without Spikes, Memphis, TN, USA), and knotless suture anchors (Multifix-S PEEK) (Smith and Nephew, Memphis, TN, USA). Four groups (n = 5 specimens) were established – group I: single fixation with interference screws; group II: single fixation with knotless anchors; group III: hybrid fixation with interference screws and staples; group IV: hybrid fixation with interference screws and knotless anchors. Each specimen underwent evaluations for cyclic displacement, cyclic stiffness, initial loading strength, ultimate failure load, pull-out displacement, and pull-out stiffness.ResultsAll specimens completed cyclic loading and load-to-failure. The cyclic displacement in group II, which had a single fixation, indicated significantly greater elongation compared with the other groups (P = 0.002). The hybrid systems were more rigid than the single systems in terms of cyclic stiffness, and no statistically significant difference was observed between the hybrid systems (P = 0.461). Group IV was significantly superior in terms of the ultimate failure load (P = 0.004). No statistically significant differences were noted between the groups for pull-out displacement or pull-out stiffness.ConclusionSingle fixation with bioscrews as an in-tunnel tibia fixation method was as successful as hybrid systems. Multifix-S PEEK knotless suture anchors, which can be combined with bioscrews, can be a superior fixation alternative due to its flexibility and ultimate failure load values.     

Improvement of primary stability in ACL reconstruction by mesh augmentation of an established method of free tendon graft fixation. A biomechanical study on a porcine model

PurposeThe aim of the present study was to compare primary stability in ACL reconstruction and ultimate load to failure of a mesh augmented hamstring tendon graft fixed with two cross pins to established hamstrings and bone-patellar-tendon-bone (BTB) graft fixation methods.MethodsForty fresh porcine femora were divided into four groups: (A): BTB graft fixed with two RigidFix® pins, (B): hamstring tendon graft fixed with a Milagro® interference screw, (C): hamstring tendon graft fixed with two RigidFix® pins, and (D): hamstring tendon graft augmented with Ultrapro® mesh fixed with two RigidFix® pins. Each graft underwent cyclic loading in tension and load to failure. Elastic and plastic displacements were measured by 3-dimensional digital image correlation. Groups were compared by one-way ANOVA and Tukey–Kramer post-hoc tests.ResultsAfter 1000 cycles, the mean plastic displacement was lowest in the BTB graft (p < 0.001). Plastic displacement was significantly lower in the mesh augmented group compared to the plain hamstring graft and the Milagro screw group (p < 0.05). Load to failure was highest in the mesh-augmented group; significant to the hamstring tendon (p = 0.023).ConclusionAlthough the BTB-graft represented the most stable construct against plastic displacement in our study, mesh augmentation of free tendon grafts significantly increased primary stability and reduced plastic displacement of femoral cross pin fixation. This new augmentation device may better protect the hamstrings graft from secondary elongation during postoperative rehabilitation.Clinical relevanceMesh augmentation seems to be an effective technique to stabilise free hamstring tendon autografts during postoperative rehabilitation with significant reduction of graft slippage.     

Interfacial optimization of fiber-reinforced hydrogel composites for soft fibrous tissue applications

Meniscal tears are the most common orthopedic injuries to the human body, yet the current treatment of choice is a partial meniscectomy, which is known to lead to joint degeneration and osteoarthritis. As a result, there is a significant clinical need to develop materials capable of restoring function to the meniscus following an injury. Fiber-reinforced hydrogel composites are particularly suited for replicating the mechanical function of native fibrous tissues due to their ability to mimic the native anisotropic property distribution present. A critical issue with these materials, however, is the potential for the fiber–matrix interfacial properties to severely limit composite performance. In this work, the interfacial properties of an ultra-high-molecular-weight polyethylene (UHMWPE) fiber-reinforced poly(vinyl alcohol) (PVA) hydrogel are studied. A novel chemical grafting technique, confirmed using X-ray photoelectron spectroscopy, is used to improve UHMWPE–PVA interfacial adhesion. Interfacial shear strength is quantified using fiber pull-out tests. Results indicate significantly improved fiber–hydrogel interfacial adhesion after chemical grafting, where chemically grafted samples have an interfacial shear strength of 256.4 ± 64.3 kPa compared to 11.5 ± 2.9 kPa for untreated samples. Additionally, scanning electron microscopy of fiber surfaces after fiber pull-out reveal cohesive failure within the hydrogel matrix for treated fiber samples, indicating that the UHMWPE–PVA interface has been successfully optimized. Lastly, inter-fiber spacing is observed to have a significant effect on interfacial adhesion. Fibers spaced further apart have significantly higher interfacial shear strengths, which is critical to consider when optimizing composite design. The results in this study are applicable in developing similar chemical grafting techniques and optimizing fiber–matrix interfacial properties for other hydrogel-based composite systems.     

Effect of cyclic tension on the biomechanical properties of flexor tendon grafts. Results of an ex-vivo porcine study

BackgroundAutologous flexor tendons are widely used for anterior cruciate ligament (ACL) reconstruction. Pretension of the graft before fixation has been described as part of the surgical technique, nevertheless there is no consensus on the type and amount to tension needed to increase the stiffness without affecting its biomechanical properties.Our hypothesis is cyclic tension increases flexor tendon stiffness without affecting its ultimate failure at maximum loads (UFML).MethodsForty-five flexor digitorum profundus tendons harvested from domestic pigs (Sus scrofa domestica) were randomly divided into three groups: E1 (n = 15), E2 (n = 15) and C (n = 15). Groups E1 and E2 were subjected to 50 cyclic loads at a 1 Hz frequency, at 70 N and 100 N respectively, group C was not intervened. The three groups were then tested for UFML. Cyclic loads and measurements were performed using a Stress-Strain machine (SST 1.0 Kinetecnic ^®). Results were analyzed using GrapgPad statistical software. Groups were compared using Mann-Whitney test with a 95% confidence interval.ResultsSignificant increased stiffness for group E1 (p = 0.02) and group E2 ( p < 0.01) when compared to group C. The stiffness of group E2 was also significantly higher than E1 (p = 0.03). There was a significant reduction on the UFML between group E2 and C (p < 0.01), which was not observed when comparing groups E1 and C.ConclusionCyclic loads at 70 N result in an increased stiffness of flexor tendons without affecting its ultimate failure at maximum loads. Cyclic loads at higher tensions might cause a deleterious effect on the biomechanical properties of flexor tendon grafts.     

MPFL reconstruction using a quadriceps tendon graft: Part 1: Biomechanical properties of quadriceps tendon MPFL reconstruction in comparison to the Intact MPFL. A human cadaveric study

BackgroundThe aim of this study was to analyze the structural properties of the original MPFL and to compare it to a MPFL-reconstruction-technique using a strip of quadriceps tendon.MethodsIn 13 human cadaver knees the MPFLs were dissected protecting their insertion at the patellar border. The MPFL was loaded to failure after preconditioning with 10 cycles in a uniaxial testing machine evaluating stiffness, yield load and maximum load to failure. In the second part Quadriceps-MPFL-reconstruction was performed and tested in a uniaxial testing machine. Following preconditioning, the constructs were cyclically loaded 1000 times between 5 and 50 N measuring the maximum elongation. After cyclic testing, the constructs have been loaded to failure measuring stiffness, yield load and maximum load. For statistical analysis a repeated measures (RM) one-way ANOVA for multiple comparisons was used. The significance was set at P < 0.05.ResultsDuring the load to failure tests of the original MPFL the following results were measured: stiffness 29.4 N/mm (+ 9.8), yield load 167.8 N (+ 80) and maximum load to failure 190.7 N (+ 82.8). The results in the QT-technique group were as follows: maximum elongation after 1000 cycles 2.1 mm (+ 0.8), stiffness 33.6 N/mm (+ 6.8), yield load 147.1 N (+ 65.1) and maximum load to failure 205 N (+ 77.8). There were no significant differences in all tested parameters.ConclusionsIn a human cadaveric model using a strip of quadriceps-tendon 10 mm wide and 3 mm deep, the biomechanical properties match those of the original MPFL when tested as a reconstruction.Clinical relevanceThe tested QT-technique shows sufficient primary stability with comparable biomechanical parameters to the intact MPFL.     

Biomechanical analysis of different types of pedicle screw augmentation: A cadaveric and synthetic bone sample study of instrumented vertebral specimens

This study aims to determine the pull-out strength, stiffness and failure pull-out energy of cement-augmented, cannulated-fenestrated pedicle screws in an osteoporotic cadaveric thoracolumbar model, and to determine, using synthetic bone samples, the extraction torques of screws pre-filled with cement and those with cement injected through perforations. Radiographs and bone mineral density measurements from 32 fresh thoracolumbar vertebrae were used to define specimen quality. Axial pull-out strength of screws was determined through mechanical testing. Mechanical pull-out strength, stiffness and energy-to-failure ratio were recorded for cement-augmented and non-cement-augmented screws. Synthetic bone simulating a human spinal bone with severe osteoporosis was used to measure the maximum extraction torque. The pull-out strength and stiffness-to-failure ratio of cement pre-filled and cement-injected screws were significantly higher than the non-cement-augmented control group. However, the cement pre-filled and cement-injected groups did not differ significantly across these values (p = 0.07). The cement pre-filled group had the highest failure pull-out energy, approximately 2.8 times greater than that of the cement-injected (p < 0.001), and approximately 11.5 times greater than that of the control groups (p < 0.001). In the axial pull-out test, the cement-injected group had a greater maximum extraction torque than the cement pre-filled group, but was statistically insignificant (p = 0.17). The initial fixation strength of cannulated screws pre-filled with cement is similar to that of cannulated screws injected with cement through perforations. This comparable strength, along with the heightened pull-out energy and reduced extraction torque, indicates that pedicle screws pre-filled with cement are superior for bone fixation over pedicle screws injected with cement.     

Intraprosthetic screw fixation increases primary fixation stability in periprosthetic fractures of the femur—A biomechanical study

BackgroundThe purpose of this study was to develop a new fixation technique for the treatment of periprosthetic fractures using intraprosthetic screw fixation. The goal was to biomechanically evaluate the increase in primary fixation stability compared to unicortical locked-screw plating.MethodsA Vancouver C periprosthetic fracture was simulated in femur prosthesis constructs. Fixation was then performed with either unicortical locked-screw plating using the LISS-plate or with intraprosthetic screw fixation. Fixation stability was compared in an axial load-to-failure model.ResultsThe intraprosthetic fixation model was superior to the unicortical locked-screw fixation in all tested devices. The intraprosthetic fixation model required 11,807 N ± 1596 N for failure and the unicortical locked-screw plating required 7649 N ± 653 N (p = 0.002).ConclusionIntraprosthetic screw anchorage with a special prosthesis drill enhances the primary stability in treating periprosthetic fractures by internal fixation.     

A minimally invasive postero-medial approach with suture anchors for isolated tibial avulsion fracture of the posterior cruciate ligament

Background and purposeThe optimal surgical treatment of isolated tibial avulsion fractures of the posterior cruciate ligament (PCL) remains controversial. The purpose of this study was to report preliminary results of a novel surgical approach to isolated PCL avulsion fractures by a minimally invasive postero-medial approach with suture anchors.Patients and methodsOutcomes were retrospectively analyzed in 16 patients with isolated tibial avulsion fractures of the PCL treated with this approach.ResultsLength of surgery ranged from 20 to 40 min (mean, 28 min). Patients were followed-up for 4 to 36 months (mean, 18 months). X-rays showed that satisfactory reduction and bony healing was achieved in all cases. Excellent and good outcomes were reported by 15 and 1 patient respectively with the Lysholm score system.ConclusionsThis minimally invasive postero-medial approach, with minimal but sufficient exposure and effective fixation, may be suitable for the treatment of isolated tibial avulsion fractures of the PCL. More detailed and longer follow up of these patients is needed before definitive conclusions on efficacy can be reached.     

Anterior cruciate ligament fixation: Is radial force a predictor of the pullout strength of soft-tissue interference devices?

BackgroundIn anterior cruciate ligament (ACL) reconstruction, an interference device achieves soft-tissue graft fixation by radially compressing the graft against the bone.PurposeThe objective of this study was to measure the radial force generated by different interference devices and evaluate the effect of this radial force on the pullout strength of graft-device constructs.Study DesignControlled laboratory study.MethodsA resultant force (F_R) was used as a representative measure of the total radial force generated. Bovine tendons were fixated in either synthetic bone or porcine tibia using one of following devices: (1) RCI titanium screw, (2) PEEK screw, (3) IntraFix sheath-and-screw device, and (4) ExoShape sheath-and-insert device. F_R was measured while each device was inserted into synthetic bone mounted on a test machine (n = 5 for each device). In a subsequent test series, graft-device constructs were loaded to failure at 50 mm/min. The pullout strength was measured as the ultimate load before failure (n = 10 for each device).ResultsThe F_R values generated during insertion into synthetic bone were 777 ± 86 N, 865 ± 140 N, 1313 ±198 N, and 1780 ± 255 N for the RCI screw, PEEK screw, IntraFix, and ExoShape, respectively. The pullout strengths in synthetic bone for the RCI screw, PEEK screw, IntraFix and ExoShape were 883 ± 125 N, 716 ± 249 N, 1147 ± 142 N, and 1233 ± 190 N, respectively.ConclusionsThese results suggest that the F_R generated during interference fixation affects the pullout strength with sheath-based devices providing superior F_R compared with interference screws. The use of synthetic bone was validated by comparing the pullout strengths to those when tested in porcine tibia.Clinical relevanceThese results could be valuable to a surgeon when determining the best fixation device to use in the clinical setting.     

Posterior root tear of the medial meniscus in multiple knee ligament injuries

The purposes of the present study were to examine the frequency and characteristics of root tears of the medial meniscus associated with ligament injuries of the knee and to evaluate the effectiveness of pull-out repair for restoring meniscus function. We retrospectively analyzed the 9 patients (10 knees) with posterior root tears of the medial meniscus and ligament injuries of the knee treated between August 2004 and February 2007. All the patients were male, with average age of 29.8 years, and the mean follow-up period was 29.7 months. The pull-out suture technique was used to repair the root tears. Clinical outcomes were evaluated using the Lysholm, IKDC, and Tegner scores, as well as the McMurray and Apley tests. The mean follow-up period was 41.1 months (range, 30 to 63 months). The incidence of root tears of the medial meniscus with ligament injuries was 2.74% (10 cases in 365 ligament surgeries). All clinical results showed significant improvement. At the final follow-up, McMurray test showed one positive and nine negative cases, and the Apley test revealed two positive and eight negative cases. There were no positive findings in anterior drawer test, posterior drawer test, valgus and varus stress test, and posterolateral instability test. Healing of the root tear was confirmed by arthroscopy in five patients and by MR in four patients. Root tears of the medial meniscus may occur in multiple knee ligament injuries. It is important not to miss them. Our results indicate that pull-out repair provides satisfactory results and evidence of healing.     

Comparison of graft healing in anterior cruciate ligament reconstruction with and without a preserved remnant in rabbits

BackgroundThe remnant of the native anterior cruciate ligament (ACL) might contribute to the biological integration of the graft in ACL reconstruction. The aim of this study was to explore whether the preserved remnant enhanced graft healing in ACL reconstruction.MethodsForty New Zealand rabbits underwent bilateral anterior cruciate ligament reconstructions. One knee was treated with a 2-mm remnant preserved on the tibial side (remnant-preservation, RP group) while the contralateral knee underwent a complete removal of the remnants by cauterization (remnant-resection, RR group) in each animal. Gross observations combined with microangiography, histological evaluation, and uniaxial load testing were performed after 4, 8, and 12 weeks.ResultsThe vascular density on the graft surface was statistically higher in the RP group as compared to that of the RR group at 4 (P = 0.002) and 8 weeks (P = 0.020). Additionally, the accelerated intra-articular and intra-tunnel graft integration were histologically observed in the RP group. Histological scores in the RP group were statistically higher than the RR group at 4 weeks (P = 0.028 for the intra-articular healing and P = 0.046 for the intra-tunnel healing) and 8 weeks (P = 0.031 for the intra-articular healing and P = 0.014 for the intra-tunnel healing). The ultimate failure load (P = 0.017), yield load (P = 0.025), and stiffness (P = 0.004) were statistically higher in the RP group as compared to those of the RR group, with corresponding significant differences in the failure mode (P = 0.020) between the two groups at 8 weeks.ConclusionsThe preserved remnant enhanced ACL graft healing with improved biomechanical properties in the rabbit model.Level of evidenceLevel II.     

Biomechanical evaluation of a new system to improve screw fixation in osteoporotic bones

In this paper an experimental analysis is undertaken of the affect a new screw-to-bone fixation system has on the stiffness of fixation systems of osteoporotic fractures based on osteosynthesis plates. The proposed system, which we have named the screw locking element (SLE), is made with elements manufactured from a biocompatible polymer material known as polyetheretherketon (PEEK) which act like a lock nut, holding the end of the threaded screw shank after this has passed through both bone corticals.Seventy-two osteoporotic synbone simulated fracture models were instrumented with one of four constructs: locking compression plate with 6 locking screws (LCP), dynamic compression plate with 6 cortical screws (DCP), DCP with 2 SLEs or DCP with 6 SLEs (DCP + 6SLEs). Each group of 18 simulated fracture models were further split into 3 subgroups of 6. One subgroup was tested under cyclic cantilever bending, another under cyclic compression and the third under cyclic torsion. Loss of stiffness was determined in each test every 1,000 load cycles, between 0 and 30,000 cycles.Regardless of the load type, it was seen that the DCP system had the highest stiffness loss percentages of all the tested systems. The inclusion of SLEs significantly decreased the stiffness loss of the DCP system. Unlike the cyclic compression loads, where the LCP performed slightly better, on terminating the cantilever bending and torsion load cycles no statistically significant difference was noted (Tukey test, p > 0.05) between the percentage stiffness loss of the DCP + 6SLEs system and the LCP system. It is concluded that the proposed SLEs enable DCPs to lower the high failure rate that these exhibit in osteoporotic fracture repairs, at significantly lower costs than those resulting from the use of LCPs.     

Radiodense ligament markers for radiographic evaluation of anterior cruciate ligament reconstruction

IntroductionEarly clinical and radiographic diagnosis of failed or loosened anterior cruciate ligament (ACL) reconstructions can be challenging. The aim of the present study is to retrospectively evaluate the use of radiologically visible markers in the ACL graft, serving as a potential diagnostic tool in ACL graft rupture and insufficiency.MethodsTwenty patients were included in the study. ACL reconstruction was performed with use of a hamstring autograft in hybrid fixation technique. The graft was marked with two radiodense suture knots, one at the tibial and femoral tunnel openings. Radiographs were performed postoperatively, after 6 weeks and 12 months. Four distances between markers and landmarks were measured in anteroposterior and three in lateral radiographic views and the positional change between the timepoints of measurement was calculated.ResultsMeasurements of the marker distances on radiographs showed an excellent interobserver reliability (κ = 0.97).In two measured distal anteroposterior distances statistically significant changes could be detected between 6 weeks and 12 months postoperatively in one patient with MRI-documented ACL rerupture and in five patients with ACL elongation defined as anteroposterior-translation with side-to-side difference of ≥ 3 mm measured with a Rolimeter device. On lateral radiographs, marker distances were highly variable and did not correlate with clinical ACL elongation.ConclusionThe application of radiodense ACL graft markers is a straight-forward, non-expensive and potentially useful diagnostic tool to identify the position of the transplant and for diagnosis of graft elongation or failure. However, the method is sensitive to the radiological projection, which should be further studied and optimized.     

A new femoral fixation device for anterior cruciate ligament reconstruction using the outside-in technique and hamstring tendon graft: A comparison between two devices in cadaveric human knee models

Background

A new device (T-anchor) was developed for ACL reconstruction and is implanted via the outside-in technique using hamstring grafts. The purpose of this study was to compare the T-anchor with the EndoButton Direct.

Biomechanics of single-tunnel double-bundle anterior cruciate ligament reconstruction using fixation with a unique expandable interference screw

BackgroundSingle-tunnel double-bundle (STDB) anterior cruciate ligament (ACL) reconstruction can restore biomechanical function and anatomic structure, but existing methods of graft fixation are not adequate. The aims of this study are to examine knee biomechanics after STDB reconstruction using a unique expandable interference screw for fixation.MethodsThe biomechanical parameters of six pairs of human cadaveric knee specimens were measured with the ACL intact, after ACL removal, and after STDB reconstruction using the interference screw or single-tunnel single-bundle (STSB) reconstruction. Anterior tibial translation under 134 N anterior tibial load in a neutral position as well as in 15° and 30° internal and external knee rotation and the internal tibial rotation angle under the rotatory load (5 N · m internal tibial rotation) were measured.ResultsAnterior tibial translations at each degree of knee flexion in the STDB group were significantly less than in the STSB group (all, P < 0.05). The internal rotation angles in the STSB group at five flexion angles were significantly higher than in the ACL intact group, whereas there were significantly less than those of the ACL absent group (P < 0.05). Under rotatory loads in the neutral position, the tibial internal rotation angles of the STDB group were significantly lower than in the STSB group at all flexion angles (all, P < 0.05).ConclusionsSTDB ACL reconstruction with the expandable interference screw provides better anteroposterior and rotational stability than STSB reconstruction.Clinical relevanceThe technique provides the advantages of double-bundle reconstruction using a single-tunnel technique.     

Meniscus repair five-year results are influenced by patient pre-injury activity level but not age group

BackgroundThe purpose of the study is to determine whether patient age group (≥ 40 years versus < 40 years) and pre-injury activity level are independently predictive of symptomatic failure rates and patient-reported outcomes after meniscus repair with or without concomitant anterior cruciate ligament reconstruction (ACLR) at mean five years of follow-up.MethodsTwo hundred and twenty-five patients (n = 61, age ≥ 40 years; n = 164, age < 40; 11% sedentary, 63% recreational athletes, 26% competitive athletes; 72% cutting-pivoting sports, 28% non-cutting or non-pivoting sports) who underwent meniscal repair were assessed for symptomatic failure and subjective knee function at mean 5.4 years of follow-up. Symptoms were assessed with Knee Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee Subjective (IKDC-S) scores.ResultsRepair failure was 20% overall with no association with age group (< 40 vs. ≥ 40 years) or level of activity. When compared with sedentary patients, IKDC-S scores were not associated with age group but were lower among sedentary patients (mean: 59.6, SE: 4.9) compared with recreational (mean: 78.9, SE: 2.5; p = 0.007) or competitive athletes (mean: 79.2, SE: 3.8; p = 0.02). KOOS-ADL scores were independently associated with age and were higher among patients < 40 years. KOOS-pain, KOOS-sport, or KOOS-QOL were not associated with age group. Sedentary status was independently associated with lower KOOS scores for all sub-scores.ConclusionsMeniscal repair failure rates and patient-reported outcomes do not differ substantially between older or younger patients of similar pre-injury activity level. Sedentary patients regardless of age have worse self-reported subjective outcomes compared with active patients.     

Compact platelet-rich fibrin scaffold to improve healing of patellar tendon defects and for medial collateral ligament reconstruction

BackgroundPlatelets are one of the most biocompatible and cost-effective sources of growth factors. Attention is being paid to autologous platelets and platelet-rich plasma. We developed a novel compact platelet-rich fibrin scaffold (CPFS) that was produced from blood and calcium gluconate only. The objective of this study was to investigate the potential of CPFS as a provisional scaffold in two rabbit models.MethodsIn the first rabbit model, the central half of the patellar tendon was resected bilaterally. Allogenic CPFS was attached to the defect in the right knee, while the left knee was untreated. In the other model, the medial collateral ligament was removed bilaterally. The ligament of the right knee was reconstructed with allogenic CPFS, whereas the left knee was untreated.ResultsAfter 12 weeks, the ultimate failure load and stiffness were higher for the right patellar tendon than for the left patellar tendon in the former model. It was found that CPFS promoted ligament repair tissue in contrast with that on the untreated side in the latter model. The ultimate failure load of the CPFS repair tissue at 20 weeks was 78% of that in healthy controls of the same age.ConclusionsCPFS enhanced the healing of tendons and ligaments.Clinical relevanceCPFS has the potential to accelerate healing of tendons and ligaments as a provisional bioscaffold or a material for graft augmentation.     

Medial extrusion of the posterior segment of medial meniscus is a sensitive sign for posterior horn tears

BackgroundTo evaluate medial extrusion of the posterior segment of the medial meniscus in posterior horn tears.MethodsThis study enrolled 72 patients without medial meniscal tears (group N), 72 patients with medial meniscal tears without posterior horn tears (group PH −), 44 patients with posterior horn tears of the medial meniscus (group PH +). All meniscal tears were confirmed by arthroscopy. Medial extrusion of the middle segment and the posterior segment was measured on coronal MRIs.ResultsExtrusions of both middle and posterior segments in groups PH − and PH + (middle segment; 2.94 ± 1.51 mm for group PH − and 3.75 ± 1.69 mm for group PH +, posterior segment; 1.85 ± 1.82 mm for group PH − and 4.59 ± 2.74 mm for group PH +) were significantly larger than those in group N (middle segment; 2.04 ± 1.20, posterior segment; 1.21 ± 1.86). Both indicators of extrusion in group PH + were larger than those in group PH −. In the early OA category, neither middle nor posterior segment in group PH − extruded more than in group N. However, only the posterior segment in group PH + extruded significantly more than in group N. Multiple lineal regression analyses revealed that posterior segment extrusion was strongly correlated with the posterior horn tears (p < 0.001) among groups PH − and PH +.ConclusionThe newly presented indicator for extrusion of the posterior segment of the medial meniscus is associated with posterior horn tears in comparison with the extrusion of the middle segment, especially in the early stages of osteoarthritis.Level of EvidenceLevel II - Diagnostic Study     

Chest wall reconstruction in a canine model using polydioxanone mesh,demineralized bone matrix and bone marrow stromal cells

Extensive chest wall defect reconstruction remains a challenging problem for surgeons. In the past several years, little progress has been made in this area. In this study, a biodegradable polydioxanone (PDO) mesh and demineralized bone matrix (DBM) seeded with osteogenically induced bone marrow stromal cells (BMSCs) were used to reconstruct a 6 cm × 5.5 cm chest wall defect. Four experimental groups were evaluated (n = 6 per group): polydioxanone (PDO) mesh/DBMs/BMSCs group, polydioxanone (PDO) mesh/DBMs group, polydioxanone (PDO) mesh group, and a blank group (no materials) in a canine model. All the animals survived except those in the blank group. In all groups receiving biomaterial implants, the polydioxanone (PDO) mesh completely degraded at 24 weeks and was replaced by fibrous tissue with thickness close to that of the normal intercostal tissue (P > 0.05). In the polydioxanone (PDO) mesh/DBMs/BMSCs group, new bone formation and bone-union were observed by radiographic and histological examination. More importantly, the reconstructed rib could maintain its original radian and achieve satisfactory biomechanics close to normal ribs in terms of bending stress (P > 0.05). However, in the other two groups, fibrous tissue was observed in the defect and junctions, and the reconstructed ribs were easily distorted under an outer force. Based on these results, a surgical approach utilizing biodegradable polydioxanone (PDO) mesh in combination with DBMs and BMSCs could repair the chest wall defect not only in function but also in structure.