Knee joint kinematics after dynamic intraligamentary stabilization: cadaveric study on a novel anterior cruciate ligament repair technique

PURPOSE

Dynamic intraligamentary stabilization (DIS) has been introduced for the repair of acute anterior cruciate ligament (ACL) tears as an alternative to delayed reconstruction. The aim of the present study was to compare knee joint kinematics after DIS to those of the ACL-intact and ACL-deficient knee under simulated Lachman/KT-1000 and pivot-shift tests. We hypothesized that DIS provides knee joint kinematics equivalent to an intact ACL.

METHODS

With the use of a robotic knee simulator, knee kinematics were determined in simulated Lachman/KT-1000 and pivot-shift tests at 0°, 15°, 30°, 60°, and 90° of flexion in eight cadaveric knees under the following conditions: (1) intact ACL, (2) ACL deficiency, (3) DIS with a preload of 60 N, and (4) DIS with a preload of 80 N. Statistical analyses were performed using two-factor repeated-measures analysis of variance. The significance level was set at a p value of <0.05.

RESULTS

After DIS with a preload of either 60 N or 80 N, the anterior translation was significantly reduced in the simulated Lachman/KT-1000 and pivot-shift tests when compared to the ACL-deficient knee (p < 0.05). No significant differences were observed between the DIS reconstruction with a preload of 80 N and the intact ACL with regard to anterior laxity in either test. However, DIS with a preload of only 60 N was not able to restore knee joint kinematics to that of an intact knee in all degrees of flexion.

CONCLUSION

DIS with a preload of 80 N restores knee joint kinematics comparable to that of an ACL-intact knee and is therefore capable of providing knee joint stability during ACL healing. DIS therefore provides a new technique for primary ACL repair with superior biomechanical properties in comparison with other techniques that have been described previously, although further clinical studies are required to determine its usefulness in clinical settings.

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

PURPOSE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

CLINICAL RELEVANCE

Our biomechanical results could help orthopaedic surgeons to optimize the results of primary ACL revision with incomplete, incorrect tunnel placement.

Comparison of Knee Kinematics After Single-Bundle Anterior Cruciate Ligament Reconstruction via the Medial Portal Technique With a Central Femoral Tunnel and an Eccentric Femoral Tunnel and After Anatomic Double-Bundle Reconstruction: A Human Cadaveric Study

BACKGROUND

Anatomic femoral tunnel placement in anterior cruciate ligament (ACL) reconstruction is considered to be a key to good primary stability of the knee. There is still no consensus on whether a centrally placed single bundle in the anatomical femoral footprint can compare with anatomic double-bundle (DB) reconstruction.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine knee kinematics after single-bundle ACL reconstruction via the medial portal technique using 2 different femoral tunnel positions and to compare results with those of the anatomic DB technique. The hypotheses were that (1) single-bundle reconstruction using the medial portal technique with a centrally placed femoral tunnel relative to the native footprint (SB-central technique) would more closely restore intact knee kinematics compared with the same reconstruction technique with an eccentric femoral tunnel drilled in the anteromedial bundle footprint (SB-AM technique) and (2) DB reconstruction would result in superior kinematics compared with the SB-central technique.

STUDY DESIGN

Controlled laboratory study.

METHODS

Knee kinematics was examined in 10 fresh-frozen human cadaveric knees using a robotic/universal force-moment sensor system. Kinematics in simulated pivot-shift and 134-N anterior tibial loading tests were determined in different conditions within the same specimen: (1) intact ACL, (2) deficient ACL, (3) SB-AM, (4) SB-central, and (5) DB.

RESULTS

All reconstruction techniques significantly reduced anterior tibial translation (ATT) compared with a deficient ACL at 0°, 15°, 30°, 60°, and 90° in the anterior tibial loading test (P < .01, repeated-measures analysis of variance) and at 0°, 15°, and 30° in the simulated pivot-shift test (P < .001). There were no significant differences in the SB-central group and the DB group compared with the intact ACL. Reconstruction in the SB-AM group resulted in significantly increased ATT compared with the intact ACL in near-to-extension angles in both tests (0°, 15°, and 30°; P < .01). SB-central and DB reconstructions both resulted in significantly reduced ATT, in some tests at ≤30°, compared with SB-AM reconstruction (P < .05). No significant differences between the SB-central and DB groups were found (P > .05).

CONCLUSION

The SB-central technique restored intact knee kinematics more closely than did SB-AM reconstruction at time zero. There were no differences in knee kinematics between the DB and SB-central techniques.

CLINICAL RELEVANCE

Anatomic single-bundle ACL reconstruction provides similar knee kinematics as anatomic double-bundle reconstruction.

Biomechanical evaluation of different surgical techniques for treating patellar tendon ruptures

PURPOSE

The aim of this study was to biomechanically assess patellar tendon repair techniques with additional cable wire or polydioxanone suture (PDS) cord augmentation in comparison with a suture-anchor repair technique.

METHODS

Patellar tendon repair was performed in 60 specimens using a porcine bone model. Yield load, maximum load, stiffness and elongation of patellar tendon reconstructions with (1) cable wire augmentation, (2) PDS cord augmentation or (3) suture anchor repair were evaluated using a cyclic loading and load-to-failure test setup.

RESULTS

In comparison with suture anchor repair, augmentation of the reconstruction with either cable wires or PDS cords provides significantly higher maximum loads (527 and 460 N vs. 301 N; p < 0.01 and p = 0,012, respectively) under load-to-failure testing and less elongation (8.81 mm ± 1.55 mm and 10.56 mm ± 3.1 mm vs. 18.38 mm ± 7.51 mm; p = 0.037 and p = 0.033, respectively) under cyclic loading conditions.

CONCLUSION

Augmentation of a patellar tendon repair with either a cable wire or a PDS cord provides higher primary stability than suture anchor repair in patellar tendon ruptures. The study supports the use of additional augmentation of a tendon repair in the clinical setting in order to prevent loss of reduction and allow for early post-operative mobilisation.

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

BACKGROUND

The 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.

METHODS

In 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.

RESULTS

During 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.

CONCLUSIONS

In a human cadaveric model using a strip of quadriceps-tendon 10 mm wide and 3mm deep, the biomechanical properties match those of the original MPFL when tested as a reconstruction.

CLINICAL RELEVANCE

The tested QT-technique shows sufficient primary stability with comparable biomechanical parameters to the intact MPFL.

Comparison of outside-in and inside-out technique for tibial fixation of a soft-tissue graft in ACL reconstruction using the Shim technique

INTRODUCTION

The aim of this study was to compare the biomechanical properties of tibial fixation of a free tendon graft in ACL reconstruction using the Shim, a new wedge-shaped implant, in an outside-in technique to fixation by the Shim used in an inside-out technique and fixation by interference screw in a porcine model.

MATERIALS AND METHODS

Porcine tibia and flexor tendons were used. In Group 1, the Shim was applied outside-in. In Group 2, the Shim was inserted inside-out. In the Group 3, an 8-mm interference screw was used. Ten specimens were tested in each group. Load-to-failure, elongation, stiffness and failure mode were recorded. Cyclic loading was performed between 5 and 250 N for 1,000 cycles, followed by a load to failure testing.

RESULTS

Mean maximum load-to-failure was 629.53 N in Group 1,648.54 N in Group 2 and 749.53 N in Group 3. There was no significant difference between the groups. Stiffness varied between 127.34 N/mm in Group 1, 151.27 N/mm in Group 2 and 182.25 N/mm in Group 3. No significant differences were found between outside-in Shim and interference screw fixation. No significant difference was found for elongation among the three groups. The main failure mode was a rupture of the tendon in the IFS group and a slippage of either the implant or the tendon in both groups using the Shim.

CONCLUSIONS

As no statistically significant difference could be seen concerning load to failure, stiffness and elongation between the inside-out and the outside-in techniques, the Shim can be used for tibial fixation in an outside-in or inside-out technique depending on the preference of the surgeon. To prevent slippage of the graft a hybrid fixation should be considered.

Comparison of tension band wiring and precontoured locking compression plate fixation in Mayo type IIA olecranon fractures

Aim of the present study was to compare the clinical and radiographic outcome of tension band wiring and precontoured locking compression plate fixation in patients treated surgically for an isolated olecranon fractures type IIA according to the Mayo classification. Of 26 patients presenting with an isolated Mayo type IIA olecranon fracture, 13 underwent fixation with a precontoured locking compression plate (group A), 13 patients were treated with tension band wiring (group B). At a mean follow-up of 43 months, patients were clinically and radiographically re-examined using the DASH score, the Mayo Elbow Performance score (MEPS) and anteroposterior and lateral radiographs. The mean DASH score was 14 points in group A and 12.5 points in group B. Regarding the MEPS, 92% of the patients in group A achieved a good to excellent results in comparison to 77% in group B. No significant differences between the two groups could be detected regarding the clinical and radiographic outcome. Implant-related irritations requiring hardware removal occurred more frequently in group B (12 vs. 7). Procedure and implant related costs were significantly higher in group A. Tension band wiring is still a preferable surgical method to treat simple isolated olecranon fractures. The patient must be informed that in all likelihood implant removal will be required once the fracture has healed. Fixation with precontoured locking compression plates does not provide better functional and radiographic outcome but is more expensive than tension band wiring.

The potential of implant augmentation in the treatment of osteoporotic distal femur fractures: a biomechanical study

PURPOSE

Osteoporotic fractures of the distal femur are an underestimated and increasing problem in trauma and orthopaedic surgery. Therefore, this study investigates the biomechanical potential of implant augmentation in the treatment of these fractures.

METHODS

Twelve osteoporotic surrogate distal femora were randomly assigned to the augmented or non-augmented group. All specimens were fixed using the LCP DF. In the augmented group additionally 1ml Vertecem V+ was injected in each screw hole before screw positioning. The construct represents an AO 33 A3 fracture. Biomechanical testing was performed as sinusoidal axial loading between 50 and 500N with 2Hz for 45,000 cycles, followed by loading between 50 and 750N until failure.

RESULTS

The augmented group showed significant higher axial stiffness (36%). Additionally the displacement after 45,000 cycles was 3.4 times lower for the augmented group (0.68±0.2mm vs. 2.28±0.2mm). Failure occurred after 45,130 cycles (SD 99) in all of the non-augmented specimens and in two specimens of the augmented group after 69,675 cycles (SD 1729). Four of the augmented specimens showed no failure. The failure mode of all specimens in both groups was a medial cut-out.

CONCLUSIONS

This study shows a promising potential of implant augmentation in the treatment of osteoporotic distal femur fractures.

Biomechanics of a new technique for minimal-invasive coracoclavicular ligament reconstruction

PURPOSE

To evaluate the biomechanical properties of a new coracoclavicular (CC) ligament reconstruction using a subcoracoidal flip button and a tendon graft compared to an augmented tendon loop and a synthetic coracoclavicular ligament reconstruction.

METHODS

A porcine metatarsalia model was used to assess supero-inferior fixation strength of (1) a new technique using an augmented tendon graft and a subcoracoidal flip button in a lifting block fashion, (2) an augmented tendon loop around the coracoid base and (3) a synthetic coracoclavicular ligament augmentation technique. Cyclic loading from 20 to 70 N for 1,000 cycles was performed, followed by a load-to-failure protocol.

RESULTS

All specimens of the three different groups survived the cyclic loading protocol. The maximum loads to failure under superior loading conditions were 760 ± 78 N for group 1, 702 ± 48 N for group 2 and 1117 ± 91 N for group 3. The synthetic coracoclavicular ligament augmentation technique revealed significantly higher maximum loads compared to the other groups (p < 0.001). The augmented tendon graft/flip button construct had higher maximum loads than the augmented tendon loop (n.s.). No significant differences were found for stiffness and elongation behaviour among the 3 tested groups.

CONCLUSION

The results suggest that the described technique is an alternative option to reconstruct the CC ligaments in AC joint instability in a minimal-invasive technique. Under superior loading conditions, the biomechanical properties exhibited by this novel technique were comparable to those of the tendon loop around the coracoid base.

Structural properties of a new device for graft fixation in cruciate ligament reconstruction: the shim technique

INTRODUCTION

In ACL reconstruction using a soft tissue graft, aperture fixation with interference screws (IFS) can lacerate and rotate the graft and cause primary tunnel widening. To overcome these downsides, a new wedge-shaped implant (MegaShim, Karl Storz, Germany) was developed. We hypothesized that aperture fixation of hamstring ACL reconstruction using the MegaShim technique shows comparable structural properties when compared to interference screw fixation.

METHODS

In a porcine knee model, ACL reconstructions with a tunnel diameter of 6, 7, 8 and 9 mm were performed and human hamstring grafts were fixed using the MegaShim technique (group I). In group 2, grafts were fixed in a hybrid fixation using a MegaShim and cortical flip button (FlippTack, Karl Storz, Germany). Interference screw graft fixation served as a control group (group III). Maximum load, yield load and stiffness were recorded using material testing machine. Grafts were cyclically preconditioned between 0 and 20 N for 10 cycles before the graft-bone complex was loaded to failure. Statistical evaluation was performed using SPSS Version 11.0.

RESULTS

Mean maximum load to failure for the hybrid fixation was significantly higher than after interference screw or MegaShim fixation. The difference between MegaShim and interference screw fixation showed no significant difference for 6 and 7 mm sizes. An 8 and 9 mm MegaShim fixation resulted in significantly lower ultimate failure load compared to interference screw fixation. Stiffness of grafts fixed using 6 mm MegaShim was significantly lower than grafts fixed with hybrid or interference screw fixation, whereas no significant differences were found in the 7, 8, and 9 mm fixations.

CONCLUSION

Aperture fixation using the MegaShim technique provides comparable structural properties compared to interference screw fixation. Hybrid fixation using MegaShim and cortical flip button results in significantly higher ultimate failure loads than both aperture fixation approaches. Smaller grafts (6 mm) showed significantly lower ultimate failure load and stiffness than interference screw fixation. The "MegaShim technique" is an alternative to interference screw fixation concerning initial fixation strength.

Strategies for repair of radial tears close to the meniscal rim--biomechanical analysis with a cyclic loading protocol

BACKGROUND

Lateral meniscectomy contributes to early-onset osteoarthritis. Biomechanical properties of sutures repairs for complete radial meniscal tears remain unknown.

HYPOTHESIS

Double horizontal suture techniques for repair of radial meniscal tears with a shorter distance from the meniscal rim provide significantly higher structural properties than do comparable single-suture techniques with a wider distance from the meniscal rim.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 55 fresh-frozen porcine menisci, standardized complete radial meniscal tears were repaired with different distances from the meniscal rim and tear edges and with different numbers of sutures. In group A, the suture was 4 mm from the tear and 8 mm from the meniscal rim; group B, 2 mm from tear; group C, 2 mm from tear, 12 mm from rim; group D, double-loop technique, 2 mm from tear, 5 mm and 10 mm from rim; group E, longitudinal tear sutured with 1 loop, 8 mm from rim, and 4 mm between stitches. The specimens were cyclically loaded 1000 times between 5 and 20 N and loaded to failure.

RESULTS

All repaired constructs survived the cyclic loading protocol. Compared with the single-loop techniques, the double-loop technique (group D) showed a significantly higher maximum load and yield load and significantly lower displacement after 1000 cycles. Compared with group B, group C had a higher displacement after 1000 cycles (P < .05), and its stiffness showed a descriptive negative trend (P = .09). Displacement after cycling testing in group C was higher than in groups B and D (P < .05).

CONCLUSION

Repair of radial meniscal tears with a second suture and shorter distance from the meniscal rim has a positive influence on primary stability. Different distances from tear edges apparently have no influence on structural properties.

CLINICAL RELEVANCE

Horizontal sutures for repair of radial meniscal tears provide high stability and can be enhanced with a second horizontal suture and shorter distance from the meniscal rim.

ACL mismatch reconstructions: influence of different tunnel placement strategies in single-bundle ACL reconstructions on the knee kinematics

To evaluate the influence of tibial and femoral tunnel position in ACL reconstruction on knee kinematics, we compared ACL reconstruction with a tibial and femoral tunnel in anteromedial (AM-AM reconstruction) and in posterolateral footprint (PL-PL reconstruction) with a reconstruction technique with tibial posterolateral and femoral anteromedial tunnel placement (PL-AM reconstruction). In 9 fresh-frozen human cadaveric knees, the knee kinematics under simulated Lachman (134 N anterior tibial load) and a simulated pivot shift test (10 N/m valgus and 4 N/m internal tibial torque) were determined at 0°, 30°, 60°, and 90° of flexion. Kinematics were recorded for intact, ACL-deficient, and single-bundle ACL reconstructed knees using three different reconstruction strategies in randomized order: (1) PL-AM, (2) AM-AM and (3) PL-PL reconstructions. Under simulated Lachman test, single-bundle PL-AM reconstruction and PL-PL reconstructions both showed significantly increased anterior tibial translation (ATT) at 60° and 90° when compared to the intact knee. At all flexion angles, AM-AM reconstruction did not show any statistical significant differences in ATT compared to the intact knee. Under simulated pivot shift, PL-AM reconstruction resulted in significantly higher ATT at 0°, 30°, and 60° knee flexion and AM-AM reconstructions showed significantly higher ATT at 30° compared to the intact knee. PL-PL reconstructions did not show any significant differences to the intact knee. AM-AM reconstructions restore the intact knee kinematics more closely when compared to a PL-AM technique resembling a transtibial approach. PL-PL reconstructions showed increased ATT at higher flexion angles, however, secured the rotational stability at all flexion angles. Due to the independent tibial and femoral tunnel location, a medial portal technique may be superior to a transtibial approach.

Joint kinematics and in situ forces after single bundle PCL reconstruction: a graft placed at the center of the femoral attachment does not restore normal posterior laxity

INTRODUCTION

Femoral tunnel placement has a great influence on the clinical outcome after PCL reconstruction.

MATERIALS AND METHODS

Using a robotic/universal force moment sensor (UFS) testing system, we examined joint kinematics and in situ forces of human knees following soft-tissue single bundle PCL reconstruction fixed at the center of the femoral attachment.

RESULTS

Posterior tibial translation significantly increased at all flexion angles after transsection of the posterior cruciate ligament (p<0.05). PCL reconstruction resulted in significantly less posterior tibial translation at all flexion angles when compared to the PCL deficient knee (p<0.05). The differences in the in situ force between the intact ligament and the reconstructed graft were statistical significant (p<0.05).

CONCLUSION

Single bundle PCL reconstruction with a soft-tissue graft fixed at the center of the femoral attachment is able to reduce the posterior tibial translation significantly. However, it cannot restore kinematics of the intact knee and in situ forces of the intact PCL.

Importance of femoral tunnel placement in double-bundle posterior cruciate ligament reconstruction: biomechanical analysis using a robotic/universal force-moment sensor testing system

BACKGROUND

Previous studies have identified the femoral attachment of the posterior cruciate ligament fibers as one of the primary determinants of fiber tension behavior. In addition, a double-bundle posterior cruciate ligament reconstruction has been shown to restore the intact knee kinematics more closely than does a single-bundle reconstruction.

HYPOTHESIS

An anterior tunnel position in double-bundle posterior cruciate ligament reconstruction restores the biomechanics of the normal knee more closely than does a posterior tunnel position.

STUDY DESIGN

Controlled laboratory study.

METHODS

Kinematics and in situ forces of human knees after double-bundle posterior cruciate ligament reconstruction with 2 different femoral tunnel positions (anterior vs posterior) were evaluated using a robotic/universal force-moment sensor testing system. Within the same specimen, the resulting knee kinematics and in situ forces were compared. For statistical analysis, 2-way analysis of variance repeated measures were performed.

RESULTS

The femoral tunnel position of the double-bundle hamstring graft had significant effect on the resulting posterior tibial displacement and in situ forces of the hamstring grafts. The anterior femoral tunnel position provided significantly less posterior tibial translation than did the posterior tunnel position. There was a tendency toward higher in situ forces of grafts fixed in the anterior tunnel when compared to the posterior position, but this difference was statistically not significant.

CONCLUSION

An anterior position of the bone tunnels in double-bundle posterior cruciate ligament reconstruction restores the normal knee kinematics more closely than does a posterior position of the tunnels.

CLINICAL RELEVANCE

In double-bundle posterior cruciate ligament reconstruction, posterior placement of the tunnel should be avoided.

Soft-tissue graft fixation in posterior cruciate ligament reconstruction: evaluation of the effect of tibial insertion site on joint kinematics and in situ forces using a robotic/UFS testing system

INTRODUCTION

Surgical reconstruction of the posterior cruciate ligament (PCL) is recommended in acute injuries that result in severe tibial subluxation and instability. The surgical outcome level may be affected by the tibial fixation site. In response to a 110-N posterior tibial load, kinematics and in situ forces of anatomical soft-tissue graft fixation in single-bundle PCL reconstruction using an interference screw fixation are significantly closer to those in the intact knee than with extracortical fixation with two staples.

MATERIALS AND METHODS

Using a robotic/universal force moment sensor (UFS) testing system, we examined joint kinematics and in situ forces of porcine knees following single-bundle PCL reconstruction fixed at two different tibial fixation sites: anatomical interference screw and extracortical fixation.

RESULTS

The site of the tibial graft fixation had significant effect on the resulting posterior displacement and in situ forces of the graft. Both PCL reconstruction techniques reduced the posterior tibial translation significantly. Proximal fixation techniques provided significantly less posterior tibial translation than extracortical fixation. Single-bundle PCL reconstruction with an interference screw showed higher in situ forces of the graft than the extracortical fixation.

CONCLUSIONS

The kinematics and in situ forces of a single-bundle PCL reconstruction using an interference screw fixation technique are superior to the primary stability of an extracortical fixation with staples.