Biodegradable Interference Screw Research Articles

Tunnel widening after ACL reconstruction with different fixation techniques: aperture fixation with biodegradable interference screws versus all-inside technique with suspensory cortical buttons. 5-year data from a prospective randomized trial.

The aim of the present study was to examine tunnel widening and clinical outcomes after anterior cruciate ligament reconstruction (ACLR) using two different fixation methods: aperture fixation with biodegradable interference screws versus all-inside ACLR with suspensory cortical buttons. Tunnel widening was assessed using volumetric and diameter measurements on magnetic resonance imaging (MRI) scans directly after surgery, as well as 6months and 2 and 5years postoperatively. Clinical outcomes were assessed after 5years with instrumented tibial anteroposterior translation measurement (KT-1000), single-leg hop testing, and the IKDC, Lysholm, and Tegner activity scores. At the final follow-up, the study population consisted of 21 patients, 12 of whom underwent screw fixation and 9 of whom had button fixation. 3 patients with all-inside ACLR had sustained early repeat ruptures within 6 months after surgery and had to be excluded from the further analysis. With screw fixation, the tibial tunnel volume changed significantly more over time compared to all-inside button fixation, with a larger initial increase at 6months (from postoperative 2.9 ± 0.2 to 3.3 ± 0.2 cm3 at 6months versus 1.7 ± 0.1 to 1.9 ± 0.2 cm3) and a greater final decrease over 2-5years postoperatively (from 3.1 ± 0.2 to 1.9 ± 0.2 cm3 versus 1.8 ± 0.2 ± 0.1 to 1.3 ± 0.1 cm3) (P < 0.001). The femoral tunnel volume remained comparable between the two groups throughout the follow-up period, with an initial 1.6 ± 0.1 cm3 in both groups and 1.2 ± 0.1 vs. 1.3 ± 0.1 after 5years in the screw and button groups, respectively (P ≥ 0.314). The maximum tibial and femoral tunnel diameters were significantly larger with screw fixation at all four time points. Tibial diameters measured 11.1 ± 0.2, 12.3 ± 0.3, 12.3 ± 0.4, and 11.2 ± 0.4mm in the screw group versus 8.1 ± 0.3, 8.9 ± 0.3, 9.1 ± 0.4 and 8.2 ± 0.5mm in the button group (P < 0.001). Femoral diameters measured 8.6 ± 0.2, 10.5 ± 0.4, 10.2 ± 0.3, and 8.9 ± 0.3 versus 7.3 ± 0.3, 8.4 ± 0.4, 8.4 ± 0.3, 7.5 ± 0.3, respectively (P ≤ 0.007). Four patients (33%) in the screw group exceeded a diameter of 12mm on the tibial side after 5years versus none in the button group (not significant, P = 0.104). Tibial anteroposterior translation measurement with KT-1000 after 5years was 2.3 ± 2.4mm in the screw group versus 3.2 ± 3.5mm in the button group (not significant, P = 0.602). There were no significant differences between the groups in any of the other clinical outcomes. Tibial tunnels in ACLR with screw fixation were associated with a larger increase in tunnel volume within the first 2years and a greater decrease up to 5years after surgery, while femoral tunnel volumes did not differ significantly. On the tibial side, the need for staged revision ACLR may be greater after biodegradable interference screw fixation if repeat ruptures occur, especially within the first 2years after primary ACLR. Concerns may remain regarding a higher graft failure rate with all-inside ACLR. II. NCT01755819.

Interference screws manufactured from magnesium display similar primary stability for soft tissue anterior cruciate ligament graft fixation compared to a biocomposite material – a biomechanical study

PurposeBiodegradable interference screws (IFS) can be manufactured from different biomaterials. Magnesium was previously shown to possess osteoinductive properties, making it a promising material to promote graft-bone healing in anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to compare IFS made from magnesium to a contemporary biocomposite IFS.MethodsIn a porcine model of ACL reconstruction, deep porcine flexor tendons were trimmed to a diameter of 8 mm, sutured in Krackow technique, and fixed with either 8 × 30 mm biocomposite IFS (Bc-IFS) or 8 × 30 mm magnesium IFS (Mg-IFS) in an 8 mm diameter bone tunnel in porcine tibiae. Cyclic loading for 1000 cycles from 0 to 250 N was applied, followed by load to failure testing. Elongation, load to failure and stiffness of the tested constructs was determined.ResultsAfter 1000 cycles at 250 N, elongation was 4.8 mm ± 1.5 in the Bc-IFS group, and 4.9 mm ± 1.5 in the Mg-IFS group. Load to failure was 649.5 N ± 174.3 in the Bc-IFS group, and 683.8 N ± 116.5 in the Mg-IFS group. Stiffness was 125.3 N/mm ± 21.9 in the Bc-IFS group, and 122.5 N/mm ± 20.3 in the Mg-IFS group. No significant differences regarding elongation, load to failure and stiffness between Bc-IFS and Mg-IFS were observed.ConclusionMagnesium IFS show comparable biomechanical primary stability in comparison to biocomposite IFS and may therefore be an alternative to contemporary biodegradable IFS.

BIOMECHANICAL EVALUATION OF AN INVERTED FIXATION FOR ACL RECONSTRUCTION WITH NONMETALLIC HARDWARE AND TIBIAL SUBCORTICAL SUPPORT TO INCREASE STRENGTH AT THE TIBIAL SITE

In this paper, we evaluate the initial biomechanical properties of an anterior cruciate ligament (ACL) reconstruction technique that inverts the anatomical location of the commonly used hardware and relies the tibial fixation on the subcortical bone to increase tibial site strength. Four 7-specimen groups were tested in a porcine model: for the control ACL reconstruction technique, the femur with a cross-pin fixation supported in the trabecular bone and the tibia with a biodegradable interference screw (BIS); for the new proposed technique, the femur with a BIS and the tibia with a cross-pin fixation leaned on the tibial subcortical bone. The specimens were subjected to cyclic and load-to-failure tests to compute their biomechanical performance. At the tibia, the cross-pin fixation revealed higher resistance than the BIS ([Formula: see text] for ultimate load and [Formula: see text] = 0.006 for yield load), additionally cyclic and total displacement at representative loads showed extremely high values with BIS fixation (in two specimens greater than 9[Formula: see text]mm for 250 N and greater than 10[Formula: see text]mm for 450[Formula: see text]N). At the femur, no differences between fixations were observed. The inverted ACL reconstruction improves resistance at the tibial site with respect to the control technique, with similar resistance at the femoral site and no differences in total displacement at representative loads. It offers a useful and robust solution when greater tibial resistance is required.

A Comparative Study on Functional Outcomes of Fixed Versus Adjustable Length-Loop Device for Femoral Fixation of Graft in Anterior Cruciate Ligament Reconstruction

A Comparative Study on Functional Outcomes of Fixed Versus Adjustable Length-Loop Device for Femoral Fixation of Graft in Anterior Cruciate Ligament Reconstruction

Evaluation of the results of arthroscopic anterior cruciate ligament reconstruction with quadruple strand hamstring autograft fixed by biodegradable screws

Introduction: Worldwide arthroscopic surgeons commonly used hamstring tendons as the favorable graft and biodegradable screws for fixation of the graft for Anterior Cruciate Ligament reconstruction (ACLR). The present research was undertaken to evaluate the results of arthroscopic ACL reconstruction with quadruple strand Semitendinosus and Gracilis (STG) autograft and fixed by biodegradable interference screws in both tibia and femur. Materials and Methods: This quasi-experimental research was included thirty (30) patients with ACL injuries and were treated in the form of arthroscopic reconstruction of ACL by quadruple strand hamstring autograft fixed by biodegradable screws in both tibia and femur. Preoperative and postoperative evaluations were performed according to the Lysholm Knee Scoring Scale and rehabilitation protocol was followed accordingly. Final outcome was evaluated at 24 weeks post-operatively. Results: In pre-operative evaluation, Lysholm Knee Score was poor in 93% cases and fair in 7% cases. Post operatively significant improvement was found. According to postoperative Lysholm knee score, an excellent result was obtained in 73% cases, good in 20% cases and fair in 7% cases which showed significant improvement. Conclusion: For arthroscopic ACL reconstruction, quadrupled hamstring autograft fixed with biodegradable screws in both tibia and femur brings an excellent and acceptable result.

Adjustable-length loop cortical button versus interference screw fixation in quadriceps tendon anterior cruciate ligament reconstruction – A biomechanical in vitro study

BackgroundThis biomechanical cadaveric in vitro study aimed to evaluate and compare the dynamic elongation behavior and ultimate failure strength of tibial adjustable-length loop cortical button versus interference screw fixation in quadriceps tendon-based anterior cruciate ligament reconstruction. MethodsSixteen human quadriceps tendons were harvested and fixed into porcine tibiae using either biodegradable interference screw (n = 8) or adjustable loop device (n = 8) fixation. An acrylic block was utilized for femoral adjustable loop device fixation for both groups. All constructs were precycled for 10 times at 0.5 Hz and manually retensioned before tested in position and force control mode each for 1000 cycles at 0.75 Hz according to in vitro loading conditions replicating the in vivo ACL environment. Subsequently, an ultimate failure test at 50 mm/min was performed with mode of failure noted. FindingsTibial IS fixation showed no statistically significant differences in the initial (−0.46 vs. −0.47 mm; P = 0.9780), dynamic (2.18 mm vs. 2.89 mm; P = 0,0661), and total elongation (1.72 mm vs. 2.42 mm; P = 0,0997) compared to adjustable loop device fixation. The tibial button fixation revealed an increased ultimate failure load (743.3 N vs. 606.3 N; P = 0.0027), while stiffness was decreased in comparison to screw fixation (133.2 N/mm vs. 153.5 N/mm; P = 0,0045). InterpretationAnterior cruciate ligament reconstruction for quadriceps tendon graft using a tibial adjustable-length loop cortical button provides for comparable dynamic stabilization of the knee with increased ultimate failure load at decreased stiffness compared to screw fixation.

Хирургическое лечение пациентов с разрывом дистального сухожилия двуглавой мышцы плеча: методы фиксации и реабилитации. Опыт лечения 20 пациентов

Distal biceps brachii tendon ruptures are relatively uncommon injuries with numerous surgical exposures and methods of fixation offered for repair. The goal of surgical management is to restore the anatomic footprint of the biceps tendon on the radial tuberosity. Distal biceps fixation techniques include the use of bone tunnels in the bicipital tuberosity, tendon fixation with interference screws and cortical button that are competitive with alternative methods of suture anchors and transosseous sutures. Amplification of technical surgical aspects allows for a safer procedure, more aggressive postoperative rehabilitation and reduced recovery period for the elbow joint. Objective The purpose was to present the clinical experience and compare methods of fixation of tendon ruptures in terms of their advantages and disadvantages, implants’ effect on postoperative function recovery in a group of patients followed for three years. Material and methods A retrospective review included 20 patients with distal biceps brachii tendon ruptures that required surgical treatment. Results Positive outcomes were achieved in 19 cases (95 %). Disability period was 33.5 ± 0.5 days in a group of intellectual workers and 45.5 ± 0.71 days in physically active patients or sportsmen. Conclusion The findings showed advantages of combined tendon fixation with cortical button and biodegradable interference screw. The results of treatment were shown to rank more than twice over those achieved with suture anchors and transosseous sutures.

Bone tunnel enlargement in anterior cruciate ligament reconstruction done using hamstring tendon autografts: A prospective clinical and computed tomography-based evaluation

Context: Enlargement of osseous tunnels following anterior cruciate ligament (ACL) reconstruction is a newer discovery. This phenomenon is particularly valuable in planning for revision ACL reconstruction. Aim: The purpose of this study was to evaluate prospectively the increase in size of the tibial and femoral bone tunnel following arthroscopic ACL reconstruction with quadrupled hamstring autograft and fixation with biodegradable interference screws. Materials and Methods: A prospective study was conducted on 10 patients who underwent arthroscopic ACL reconstruction with quadrupled hamstring autograft and fixation with biodegradable interference screws. Tunnel width was measured at postoperative 2 weeks and an average of 1-year follow-up (range: 10–13 months). Clinical evaluation was done as per the International Knee Documentation Committee form. Paired Student's t-test and linear regression were used for statistical analysis. Results: There was a mean 14% enlargement in the femoral tunnel (from 9 mm at postoperative 2 weeks to 10.3 mm at postoperative 1 year) and 18% enlargement in the tibial tunnel (from 10.4 mm at postoperative 2 weeks to 12.2 mm at the postoperative 1-year follow-up). Both of these were statistically significant (P = 0.005 for femoral tunnel enlargement and P = 0.008 for the enlargement of the tibial tunnel). No statistically significant association was noted between tunnel enlargement and clinical results. Conclusion: Compared to previous similar studies, less tunnel widening was observed in the present study. We come to a conclusion that less aggressive rehabilitation program and anatomical graft fixation technique can help achieve the goal of minimum tunnel enlargement after ACL reconstruction.

Tunnel widening after ACL reconstruction with aperture screw fixation or all-inside reconstruction with suspensory cortical button fixation: Volumetric measurements on CT and MRI scans

BackgroundTunnel widening after anterior cruciate ligament reconstruction (ACLR) is influenced by the surgical and fixation techniques used. Computed tomography (CT) is the most accurate image modality for assessing tunnel widening, but magnetic resonance imaging (MRI) might also be reliable for tunnel volume measurements. In the present study tunnel widening after ACLR using biodegradable interference screw fixation was compared with all-inside ACLR using button fixation, with tunnel volume changes being measured on CT and MRI scans. Study designRandomized controlled trial; Level of evidence, 2. MethodsThirty-three patients were randomly assigned to hamstring ACLR using a biodegradable interference screw or all-inside cortical button fixation. CT and MRI scanning were done at the time of surgery and six months after. Tunnel volume changes were calculated and compared. ResultsOn CT, femoral tunnel volumes changed from the postoperative state (100%) to 119.8% with screw fixation and 143.2% with button fixation (P=0.023). The changes in tibial tunnel volumes were not significant (113.9% vs. 117.7%). The changes in bone tunnel volume measured on MRI were comparable with those on CT only for tunnels with interference screws. Tibial tunnels with button fixation were significantly underestimated on MRI scanning (P=0.018). ConclusionsAll-inside ACLR using cortical button fixation results in increased femoral tunnel widening in comparison with ACLR with biodegradable interference screw fixation. MRI represents a reliable imaging modality for future studies investigating tunnel widening with interference screw fixation.

Biodegradable magnesium interference screws accelerate mineralization of fibrous tissue at the tendon–bone insertion in anterior cruciate ligament reconstruction model of rabbit

Biodegradable magnesium interference screws accelerate mineralization of fibrous tissue at the tendon–bone insertion in anterior cruciate ligament reconstruction model of rabbit

High-purity magnesium interference screws promote fibrocartilaginous entheses regeneration in the anterior cruciate ligament reconstruction rabbit model via accumulation of BMP-2 and VEGF

Interference screw in the fixation of autologous tendon graft to the bone tunnel is widely accepted for the reconstruction of anterior cruciate ligament (ACL), but the regeneration of fibrocartilaginous entheses could hardly be achieved with the traditional interference screw. In the present work, biodegradable high-purity magnesium (HP Mg) showed good cytocompatibility and promoted the expression of bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF), fibrocartilage markers (Aggrecan, COL2A1 and SOX-9), and glycosaminoglycan (GAG) production in vitro. The HP Mg screw was applied to fix the semitendinosus autograft to the femoral tunnel in a rabbit model of ACL reconstruction with titanium (Ti) screw as the control. The femur-tendon graft-tibia complex was retrieved at 3, 6, 9 and 12 weeks. Gross observation and range of motion (ROM) of the animal model reached normal levels at 12 weeks. No sign of host reaction was found in the X-ray scanning. The HP Mg group was comparable to the Ti group with respect to biomechanical properties of the reconstructed ACL, and the ultimate load to failure and stiffness increased 12 weeks after surgery. In the histological analysis, the HP Mg group formed distinct fibrocartilage transition zones at the tendon-bone interface 12 weeks after surgery, whereas a disorganized fibrocartilage layer was found in the Ti group. In the immunohistochemical analysis, highly positive staining of BMP-2, VEGF and the specific receptor for BMP-2 (BMPR1A) was shown at the tendon-bone interface of the HP Mg group compared with the Ti group. Furthermore, the HP Mg group had significantly higher expression of BMP-2 and VEGF than the Ti group in the early phase of tendon-bone healing, followed by enhanced expression of fibrocartilage markers and GAG production. Therefore we proposed that the stimulation of BMP-2 and VEGF by Mg ions was responsible for the fibrochondrogenesis of Mg materials. HP Mg was promising as a biodegradable interference screw with the potential to promote fibrocartilaginous entheses regeneration in ACL reconstruction.

Influence of Different Tibial Fixation Techniques on Initial Stability in Single-Stage Anterior Cruciate Ligament Revision With Confluent Tibial Tunnels: A Biomechanical Laboratory Study

To kinematically and biomechanically compare 4 different types of tibial tunnel management in single-stage anterior cruciate ligament (ACL) revision reconstruction with the control: primary ACL reconstruction using a robotic-based knee testing setup. Porcine knees and flexor tendons were used. One hundred specimens were randomly assigned to 5 testing groups: (1) open tibial tunnel, (2) bone plug technique, (3) biodegradable interference screw, (4) dilatation technique, and (5) primary ACL reconstruction. A robotic/universal force-moment sensor testing system was used to simulate the KT-1000 (MEDmetric, San Diego, CA) and pivot-shift tests. Cyclic loading and load-to-failure testing were performed. Anterior tibial translation increased significantly with all of the techniques compared with the intact ACL (P < .05). In the simulated KT-1000 test, groups 2 and 3 achieved results equal to those of primary ACL reconstruction (P > .05). The open tunnel and dilated tunnel techniques showed significantly greater anterior tibial translation (P < .05). The results of the simulated pivot-shift test were in accordance with those of the KT-1000 test. No significant differences could be observed regarding stiffness or maximum load to failure. However, elongation was significantly lower in the primary ACL reconstruction group compared with groups 1 and 3 (P= .02 and P= .03, respectively). Filling an incomplete and incorrect tibial tunnel with a press-fit bone plug or a biodegradable interference screw in a standardized laboratory situation provided initial biomechanical properties and knee stability comparable with those of primary ACL reconstruction. In contrast, the dilatation technique or leaving the malplaced tunnel open did not restore knee kinematics adequately in this model. Backup extracortical fixation should be considered because the load to failure depends on the extracortical fixation when an undersized interference screw is used for aperture fixation. Our biomechanical results could help orthopaedic surgeons to optimize the results of primary ACL revision with incomplete, incorrect tunnel placement.

Medial patellofemoral ligament reconstruction using quadriceps tendon

Stabilization of the patella by medial patellofemoral ligament (MPFL) reconstruction. Recurrent lateral patella instability with chronic weakening of the MPFL. Femoropatellar cartilage defects ICRS grade 3° or higher. Tuberositas Tibiae Trochlear Groove Index (TTTG) >20 mm. Lateral hypercompression of the patella without instability. A 3 cm transverse skin incision at the superomedial edge of the patella in 90° of flexion. Longitudinal incision of the prepatellar bursa and exposure of the quadriceps tendon. Preparation of a flat tendon strip with a length of 8 cm, a width of 10 mm, and a thickness of 3 mm, leaving the attachment at the patella intact. Flipping of the tendon strip and passing of the graft through a tunnel underneath the prepatellar tissue at the medial edge of the patella. Passing of the graft in layer two of the medial joint capsule just below the fascia (layer 1) and the vastus medialis. Fixation of the graft in a bone tunnel, drilled in the femoral insertion site of the native MPFL using a biodegradable interference screw. Patella centralizing brace for 4 weeks with range of motion (ROM) 0/0/90°, 20 kg of partial weight bearing for 3 weeks. Full weight-bearing according to pain starting from week 4 postoperatively. ROM up to 90° of flexion directly postoperatively. Free ROM starting from week 6 postoperatively. Stationary cycling 6 weeks postoperatively. Swimming and running after 10 months. Return to pivoting sports after 4-5 months. A total of 17 patients (7 men and 10 women; average age 21.5 years ±3.9 years, average BMI 22.6 ±3.9) were treated using this technique between March 2011 and November 2012. Only patients with at least one recurrent patella dislocation following conservative treatment were included. Patient satisfaction 12 months postoperatively was very high. Overall, 94.1 % would undergo the procedure again and 94.1 % were very satisfied with the cosmetic result. Significant improvement in Lysholm score 6, 12, and 24 months postoperatively (p < 0.05). Free ROM in 94.1 % of cases 12 months postoperatively. The Kujala score was reported to be 89 (±7.1) 12 months following surgery. No redislocation occurred during the 24 months following surgery.

Reconstruction of the medial patellofemoral ligament using autologous gracilis tendon in an implant-free technique on the patellar side

Anatomic reconstruction of the medial patellofemoral ligament using autologous gracilis tendon in an implant-free technique on the patellar side to regain patellofemoral stability. Recurrent dislocations, primary dislocation with high risk of recurrence, and dislocations with (osteo-)chondral flake fractures. As combined approach together with other procedures (trochleoplasty, tibial tubercle osteotomy). Revisions. As an isolated procedure in patients with high degrees of trochlear dysplasia, chronic dislocation of the patella, and patellofemoral maltracking without instability. Harvesting of the gracilis tendon. Drilling of a V-shaped tunnel with a special aiming device in anatomic position on the medial side of the patella. Drilling of a femoral tunnel in anatomic position under fluoroscopic control. Passage of the graft, arthroscopic-guided tensioning, and femoral fixation with a biodegradable interference screw. Partial weight bearing (20 kg) for 1-2 weeks. No limitation in range of motion. No orthosis. Specific sports allowed after approximately 3 months. Perioperative complications associated specifically with the technique were observed in 1.0% (7 of 729 cases). In a series of 72 consecutive cases from May 2010 to October 2010, the following were recorded after 4.0 ± 0.1 years: recurrent dislocations in 3.2%, a Tegner activity score of 5.1 ± 1.8, and subjective satisfaction in 92% (follow-up rate 87.5%). No fracture of the patella was seen in any of our patients.

Evaluation of Short Term Outcomes of Transportal Femoral Cross Pin Fixation in Anterior Cruciate Ligament Reconstruction

Objectives:Many fixation techniques are currently in use for femoral side graft fixation at ACL reconstruction surgery. Short term success following ACL reconstruction highly depends on fixation strength of the graft. In this study we report short term results of anterior cruciate ligament reconstruction using double hamstring tendon autograft using double cross pin for femoral tunnel fixation.Methods:Between years 2009 and 2013, 51 male adult anterior cruciate ligament injury cases treated surgically, in a single center, with at least one year follow up were investigated. Professional athletes, multi-ligamentous instability cases, cases requiring meniscus repair or further treatment for chondral injuries and cases with concomitant medial and lateral meniscus lesions were not included in the study. Femoral tunnel was prepared anatomically through accessory medial portal, opened medially and distally. Reconstruction was performed using double loop hamstring tendon autograft. Femoral side was fixed using double cross pin, whereas tibial side was secured using single biodegradable interference screw and titanium staple. No external immobilization method such as brace was administered. Patients were encouraged to bear weight as tolerated. Standard physiotherapy was instructed to all patients postoperatively. All cases were evaluated clinically at the end of at least one year follow-up. Clinical and functional evaluation consisted of pivot shift and Lysholm, International Knee Documentation Committee (IKDC) scores and Tegner activity evaluation systems.Results:Mean age was 28.4 (18-39) years. Mean time between the injury and reconstruction was 13 (3-21) weeks. Average duration of surgery was 48 (35-70) minutes. No case of graft failure or posterior cortical fracture was encountered. In two cases, infection was treated successfully with local debridement and antibiotics with retention of the graft. At the end of follow-up period, none of the cases demonstrated positive pivot shift test. Pre-operative and follow-up Lysholm scores were 58.3±6.7 and 87.1±5.3 (p<0.001) respectively. Pre-operative IKDC scores were evaluated as C at 37 cases and D at 14, whereas, follow-up IKDC scores were evaluated as A at 42 cases, B at 8 and C at 1 case. Pre-operative and follow-up Tegner scores were 3.7±0.6 and 6.7±0.4 (p<0.001) respectively.Conclusion:Although fixation strength of transcondylar graft fixation techniques has been questioned over loop systems with cortical fixation, it was reported that transcondylar fixation causes less tunnel widening at long term. Our study revealed successful short term results, with femoral tunnel preparation using accessory medial portal and double cross pin femoral fixation, allowing early weight bearing and rehabilitation without graft and fixation failure.

Interference screw versus Endoscrew fixation for anterior cruciate ligament reconstruction: A biomechanical comparative study in sawbones and porcine knees

Interference screw fixation is one of the most common methods for ligament reconstruction. Although the advantages and clinical outcomes of this procedure have been widely reported, post-surgical complications often arise. The purpose of this study was to evaluate a new femoral fixation device, the Endoscrew, for anterior cruciate ligament (ACL) reconstruction. We performed a mechanical test in accordance with American Society for Testing and Materials (ASTM) standards and an in vitro biomechanical study. An axial pullout test was conducted to evaluate the mechanical properties of the new device and the interference screw when implanted in solid rigid polyurethane foam test blocks. The biomechanical test used porcine femora to evaluate the initial fixation strength between these two implants. The maximum pullout force of the interference screw group [722.05 ± 130.49 N (N)] was significantly greater ( p < 0.01) than the Endoscrew group (440.79 ± 26.54 N) when implanted in polyurethane foam 320 kg/m 3 density. With polyurethane foam 160 kg/m 3 density, the maximum pullout forces were (242.61 ± 37.36 N) ( p < 0.001) and (99.33 ± 30.01 N) for the interference screw group and Endoscrew group, respectively. In the in vitro mechanical study, the Endoscrew (646.39 ± 72.38 N) required a significantly greater ultimate load prior to failure ( p < 0.05) when compared with the interference screw (489.72 ± 138.64 N). With regard to pullout stiffness, there was no statistically significant difference ( p < 0.13) between the Endoscrew group (99.15 ± 12.16 N/mm) and the interference screw group (87.96 ± 11.12 N/mm). The cyclic stiffness was also not significantly different ( p < 0.44) between the Endoscrew group (93.09 ± 16.07 N/mm) and the interference screw group (85.78 ± 14.76 N/mm). The axial pullout test showed that the strength of the Endoscrew was close to the fixation strength required for daily activities, but it is inappropriate for use in osteoporotic patients. The in vitro study showed that the Endoscrew has a superior initial mechanical fixation over the biodegradable interference screw.

Influence of screw length and diameter on tibial strain energy density distribution after anterior cruciate ligament reconstruction

Postoperative tunnel enlargement has been frequently reported after anterior cruciate ligament (ACL) reconstruction. Interference screw, as a surgical implant in ACL reconstruction, may influence natural loading transmission and contribute to tunnel enlargement. The aims of this study are (1) to quantify the alteration of strain energy den sity (SED) distribution after the anatomic single-bundle ACL reconstruction; and (2) to characterize the influence of screw length and diameter on the degree of the SED alteration. A validated finite element model of human knee joint was used. The screw length ranging from 20 to 30mm with screw diameter ranging from 7 to 9 mm were investigated. In the post-operative knee, the SED increased steeply at the extra-articular tunnel aperture under compressive and complex loadings, whereas the SED decreased beneath the screw shaft and nearby the intra-articular tunnel aperture. Increasing the screw length could lower the SED deprivation in the proximal part of the bone tunnel; whereas increasing either screw length or diameter could aggravate the SED deprivation in the distal part of the bone tunnel. Decreasing the elastic modulus of the screw could lower the bone SED deprivation around the screw. In consideration of both graft stability and SED alteration, a biodegradable interference screw with a long length is recommended, which could provide a beneficial mechanical environment at the distal part of the tunnel, and meanwhile decrease the bone-graft motion and synovial fluid propagation at the proximal part of the tunnel. These findings together with the clinical and histological factors could help to improve surgical outcome, and serve as a preliminary knowledge for the following study of biodegradable interference screw.

Paper 274: Tibial Fixation in Posterior Cruciate Ligament Reconstruction: A Biomechanical Comparison Study between Biodegradable Interference Screw and Biodegradable Cross Pin

The purpose of this study was to compare ultimate tensile load, stiffness and slippage after cyclic loading of biodegradable interference screw and biodegradable cross pin for tibial fixation in posterior cruciate ligament reconstruction. Biomechanical testing of 2 different fixation techniques was performed by use of human cadaver tibia and Achilles tendon. Two independent testing sessions were examined. The A session compared biodegradable interference screw and cross pin for Achilles bone block (10 x 30 mm). The B session compared hybrid fixation of soft tissue with the use of cancellous screw-washer in each group. The tibia-graft fixation compex was cyclically loaded between 50 N and 250 N at 1 Hz for 1000 cycles. After cycling, the amount of graft slippage was determined by measuring the change in grip to grip distance. The complex was then loaded to failure at 1mm/s, and ultimate tensile strength, stiffness, and mode of failure were determined. In session A, cross pin fixation group resulted in a significantly higher ultimate tensile strength (917.80 ± 102.4 vs 514.58 ± 148.4, p<0.01), significantly higher stiffness (302.3 ± 52.9 vs 193.5 ± 12.1, p < 0.05), and significantly less slippage (3.75 ± 1.0 mm vs 5.66 ± 0.6, p<0.001) than interference screw fixation group. In session B, cross pin fixation with additional screw group resulted in a significantly higher ultimate tensile strength (1023.75 ± 94.4 vs 816.81 ± 115.3, p<0.01), significantly higher stiffness (341.5 ± 64.9 vs 223.5 ± 38.1, p < 0.05), and less slippage (13.70 ± 1.3 mm vs 12.75 ± 1.0, p>0.05) than interference screw fixation with additional screw group. The failure mode of cross pin fixation group was pin breakage in all specimens. The failure mode of interference screw fixation group was pullout of the graft in all specimens. Our study showed that cross pin tibial fixation both bone block and soft tissue in posterior cruciate ligament reconstruction is stronger than interference screw with respect to ultimate tensile strength, stiffness, and slippage.

Hybrid Tibial Fixation for Anterior Cruciate Ligament Reconstruction With Achilles Tendon Allograft

To compare clinical outcomes of tibial fixation between a biodegradable interference screw only and a biodegradable interference screw supplemented by a post-tie using a washer screw in single-bundle anterior cruciate ligament (ACL) reconstruction with 2-strand free tendon Achilles allograft in active young men. A prospective study was performed in 80 subjects who underwent single-bundle ACL reconstruction. A 2-strand free tendon Achilles allograft fixed with an EndoButton (Smith & Nephew, Andover, MA) in the femoral tunnel and with a Bio-Interference screw (Arthrex, Naples, FL) in the tibial tunnel was used in group I. Supplementary fixation was performed with a post-tie using a washer screw in group II. The Lachman test, pivot-shift test, International Knee Documentation Committee classification, Lysholm score, range of knee motion, and side-to-side difference were evaluated preoperatively and at the last follow-up. The Tegner activity scale was evaluated before injury and at the last follow-up. The 1-leg hop test was assessed at the last follow-up. Of the patients, 36 in group I and 35 in group II could be followed up for at least 2 years. At the last follow-up, 7 patients in group I and 1 in group II showed a 2+ or 3+ on the Lachman test (P = .027). The mean side-to-side difference was 2.9 ± 2.3 mm in group I and 1.4 ± 1.6 mm in group II at the last follow-up (P = .002). The other clinical outcomes were not significantly different between the 2 groups. Supplementary tibial fixation with a post-tie in ACL reconstruction using 2-strand free tendon Achilles allograft was more effective than a biodegradable interference screw only in restoration of the anterior stability of the tibia. Level II, randomized controlled trial.

Testing of prototype interference screw for ACL reconstruction in porcine femurs

Multiple techniques for the reconstruction of anterior cruciate ligament (ACL) are available, most of which use implant made from metallic or bioabsorbable materials. Currently one of the most widely used fi xation methods for anterior cruciate ligament reconstruction with bone tendonbone graft is the interference screw. The aim of our work was to test custom design screw geometry, whether it is appropriate for ACL reconstruction. New screw was designed geometry for the work, so that screws with the same geometry could be produced for later work, from different materials. In this study injection molded biodegradable interference screws were tested on porcine femurs, with bone-patellar tendon-bone (BPTB) graft fixation. The average failure load and the stiffness (772 ± 225 N and 109 ± 33.9 N/mm respectively) of the fixation was higher than literature average, although within standard deviation. Test results showed that the designed screw geometry is adequate for BPTB graft fixation. DOI: 10.17489/biohun/2011/2/01