Medial patellofemoral ligament (MPFL) reconstruction is used to treat patellar instability and recurrent patellar dislocation. Anatomical studies have found the MPFL to be a double-bundle structure. We carried out a meta-analysis of studies reporting outcomes of patellofemoral reconstruction using hamstring tendon autograft in a double-bundle configuration and patellar fixation via mediolateral patellar tunnels. A literature search was undertaken with no language restriction in various databases from their year of inception to July 2012. The primary outcome examined was the post-operative Kujala score. We identified 320 MPFL reconstructions in nine relevant articles. The combined mean post-operative Kujala score was 92.02 (standard error (. se. ) 1.4, p = 0.001) using a fixed effects model and 89.45 (. se. 37.9, p = 0.02) using random effect modelling. The reported rate of complications with MPFL reconstruction was 12.5% (40 of 320) with stiffness of the knee being the most common. High-quality evidence in assessing double-bundle MPFL reconstruction is lacking. The current literature consists of a mixture of prospective and retrospective case series. High-quality randomised trials evaluating this procedure are still awaited. Cite this article: Bone Joint J 2013;95-B:900–5

There is a trend towards the use of double-bundle techniques for the reconstruction of the anterior cruciate ligament. This has not been substantiated scientifically. The functional outcome of these techniques is equivalent to that of single-bundle methods. The main advantage of a double-bundle rather than a single-bundle reconstruction should be a better rotational stability, but the validity and accuracy of systems for the measurement of rotational stability have not been confirmed. Despite the enthusiasm of surgeons for the double-bundle technique, reconstruction with a single-bundle should remain the standard method for managing deficiency of the anterior cruciate ligament until strong evidence in favour of the use of the double-bundle method is available

Introduction. It has been contentious whether an anatomic double-bundle technique for anterior cruciate ligament reconstruction (ACLR)is superior to that of a single-bundle technique. It has been hypothesized in the literature that the double-bundle technique could provide function closer to that of the anatomical knee joint. The purpose of this study was to compare the long-term clinical outcomes after single-bundle ACLR versus double-bundle ACLR. We hypothesized that the double-bundle technique would not be superior to the single-bundle technique. Methods. A retrospective, non-randomized, matched-paired comparative study was performed. Patients undergoing primary anterior cruciate ligament reconstruction, using either a double-bundle or single-bundle technique, between 2003 and 2008 were included and matched 1:1. Matching included age, sex, BMI, time from injury to surgery, side of injury and type of sport. Patients who underwent revision procedures, multiligament reconstruction or other ACLR techniques were excluded. Patients were subsequently followed up, noting occurrence of graft rupture and any other complications. Results. A total of 1377 ACLRs were performed during the study period. Seven hundred and fifty-six patients were excluded, leaving 396patients to be included in the matching (198 matched pairs). Mean follow-up time was 176.7 +/− 7.7 months (range, 166–211 months). Overall, 40 patients (10.1%) suffered from a graft rupture which consisted of 22 patients (11.1%) in the single-bundle group and 18patients (9.1%) in the double-bundle group. A multivariate analysis was performed using the Cox model and demonstrated that graft failure had no significant association with the surgical technique (hazard ratio (HR), 0.857(0.457;1.609), p=0.6313). (Figure 1) Five patients (2.5%) in the single-bundle group and 7 patients (3.5%) in the double-bundle group underwent secondary surgery for cyclops syndrome(p=0.5637). Three patients (1.5%) in the single-bundle group and 2 patients (1.0%) in the double-bundle group underwent arthrolysis(p=0.6547). Seven patients (3.5%) in the single-bundle group underwent secondary meniscectomy compared to 6 patients (3.0%) in the double-bundle group (p=0.7630). Conclusion. Double-bundle ACLR is not superior to single-bundle ACLR at long-term follow up. Therefore, orthopaedic surgeons do not need to use a double-bundle technique when performing ACL reconstruction. For any figures or tables, please contact authors directly

Introduction: Anatomical observation and biomechanical studies have shown that the anterior cruciate ligament (ACL) mainly consists of two distinct bundles, the anteromedial (AM) bundle and posterolateral (PL) bundle. Conventional single-bundle ACL reconstruction techniques have focused on the restoration of the AM bundle while giving limited attention to the PL bundle. The purpose of this prospective, randomize clinical study is to compare the outcomes of ACL reconstruction when using either double-bundle or single-bundle technique and bioabsorbable interference screw fixation, and similar rehabilitation, with both techniques. Methods: Sixty-five patients were randomized into either double-bundle (n = 35) or single-bundle (n=30) ACL reconstruction with hamstring tendons and bio-absorbable screw (Hexalon, Inion Company, Finland) fixation in both group. The evaluation methods were clinical examination, KT-1000 arthrometer measurements, radiographic evaluation, as well as International Knee Documentation Committee (IKDC), and Lysholm knee scores. There were no differences between the study groups preoperatively. For an average of 14 months of follow-up (range, 12 to 20 months), 30 patients of the double-bundle group and 29 patients of the single-bundle group were available (91%). Results: At the follow-up, the rotational stability, as evaluated by pivot shift test, was significantly better in the double-bundle group than in the single-bundle group. Also, the early anterior stability tended to be better with double-bundle technique, although at the 14-month follow-up, no significant difference between the groups was found anymore. In addition, none of the patients in the double-bundle group had graft failure, while four patients in the single-bundle group had. However, knee scores were equal at the follow-up, and all the results were significantly better at the follow-up than preoperatively, in both groups. Conclusions: Rotational stability and early anterior stability were better with double-bundle technique than with single-bundle technique in ACL reconstruction with hamstring autografts and bioabsorbable screw fixation. However, both fixation techniques improved patients’ performance

The biomechanical function of the anteromedial (AM) and posterolateral (PL) bundles of the anterior cruciate ligament (ACL) remains controversial. Some studies report that the AM bundle stabilises the knee joint in anteroposterior (AP) translation and rotational movement (both internal and external) to the same extent as the PL bundle. Others conclude that the PL bundle is more important than the AM in controlling rotational movement. The objective of this randomised cohort study involving 60 patients (39 men and 21 women) with a mean age of 32.9 years (18 to 53) was to evaluate the function of the AM and the PL bundles of the ACL in both AP and rotational movements of the knee joint after single-bundle and double-bundle ACL reconstruction using a computer navigation system. In the double-bundle group the patients were also randomised to have the AM or the PL bundle tensioned first, with knee laxity measured after each stage of reconstruction. All patients had isolated complete ACL tears, and the presence of a meniscal injury was the only supplementary pathology permitted for inclusion in the trial. The KT-1000 arthrometer was used to apply a constant load to evaluate the AP translation and the rolimeter was used to apply a constant rotational force. For the single-bundle group deviation was measured before and after ACL reconstruction. In the double-bundle group deviation was measured for the ACL-deficient, AM- or PL-reconstructed first conditions and for the total reconstruction. We found that the AM bundle in the double-bundle group controlled rotation as much as the single-bundle technique, and to a greater extent than the PL bundle in the double-bundle technique. The double-bundle technique increases AP translation and rotational stability in internal rotation more than the single-bundle technique

While double-bundle anterior cruciate ligament (ACL) reconstruction attempts to recreate the two-bundle anatomy of the native ACL, recent research also indicates that double-bundle reconstruction more closely reproduces the biomechanical properties of the ACL and restores the rotatory and sagittal stability to the level of the intact knee that was not attainable with anatomic single-bundle reconstruction. Though double-bundle reconstruction provides these potential biomechanical benefits, it poses a significant challenge to the surgeon who must attempt to accurately place twice as many tunnels while avoiding tunnel convergence compared to single-bundle reconstruction. In addition, previous work has shown that tunnel malpositioning may cause grafts that fail to reproduce the native biomechanics of the ACL, increase graft tension in deep knee flexion, increase anterior tibial translation, and produce lower IKDC (International Knee Documentation Committee) scores. We hypothesise that experienced surgeons without the use of computer-assisted navigation will place tunnels on the tibial plateau and lateral femoral condyle that more closely emulate the locations of the native anteromedial (AM) and posterolateral (PL) ACL bundles than inexperienced surgeons with the use of computer-assisted navigation. A novice surgeon group comprised of three medical students each performed double-bundle ACL reconstruction using passive computer-assisted navigation on a total of eleven cadaver knees. Their individual results were compared to three experienced orthopaedic surgeons each performing the identical procedure without the use of computer-assisted navigation on a total of nine cadaver knees. There were no significant differences in placement of either the AM or PL tunnels on the tibial plateau between novice surgeons using computer-assisted navigation and experienced surgeons without the use of computer navigation. On the lateral femoral condyle, novice surgeons placed the AM and PL tunnels significantly more anterior along Blumensaat's line on average compared to experienced surgeons. Both groups placed femoral AM and PL tunnels anterior to previously described AM and PL bundle positions. Novice surgeons utilizing computer-assisted navigation and experienced surgeons without computer assistance place the AM and PL tunnels on the tibial side with no significant difference. On the lateral femoral condyle, novice surgeons utilising computer-assisted navigation place tunnels significantly anterior along Blumensaat's line compared to experienced surgeons without the use of computer navigation

Purpose of the study: The double-bundle technique for the reconstruction of the anterior cruciate ligament (ACL) enables anatomic repair. This reconstruction may not however be possible in all patients due to the variable quality of the graft material: insufficient length and diameter. For the double-strand hamstring technique, the diameter of the posterolateral bundle (PL) can be less than 6 mm, and for the anteromedial bundle (AM) sometimes less than 7 mm. With the bundle-strand TLS larger sized grafts can be constructed in all cases. Material and method: We operated 15 patients with full thickness tears of the ACL. The standard TLS method was used for each strand. The semitendinous and the gracilis tendons were shaped in a closed loop into short four-strand grafts measuring 45 to 50 mm. The four tunnels were reamed retrogradely arthroscopically. The graft was fixed with mersilene tape in the tunnels and locked with four titanium screws with the knee in extension for PL and 45° for AM. The diameter of each bundle was measured. Outcome was compared with that of 15 patients treated with the double-bundle technique using hamstring tendons fixed with a femoral endobutton and a tibial screw. Results: There were no pre- or postoperative complications in the two groups. The mean diameter of the PL bundle was 6.2 mm for the endobutton group and 7.9 mm for the TLS group (p< 0.001). The diameter of each bundle with the TLS technique was thus significantly greater in the femoral notch with no deficit in postoperative extension. Conclusion: The TLS method has already demonstrated excellent results for the single-bundle reconstruction of the ACL. The TLS double-bundle reconstruction technique provides a quality bundle with a large diameter in all patients, irrespective of the hamstring quality. The long-term results should confirm the efficacy of this double-bundle technique

To compare the early functional and clinical results, between single (SB) and double-bundle (DB) of Anterior Cruciate Ligament (ACL) reconstruction with hamstrings (HS). Thirty-six patients from 17 to 36 years old (average age 23), 22 ♂ and 14 ♀, from January 2006 to May 2008, were randomly allocated for ACL reconstruction with HS (SB – DB). Eighteen patients underwent a 4-stranded SB reconstruction (group A) and the remaining 18 underwent an anatomic, 2-stranded DB ACL reconstruction with 2 tibial and 2 femoral tunnel technique (group B), by using the Smith & Nephew instrumentation system. The follow-up was from 8 to 22 months (average 16 months) for both groups and included clinical evaluation (pivot-shift test, anterior laxity test with KT-1000 arthrometer and Lysholm knee score) and radiographs. There were no statistically significant difference in the results between the 2 groups with regard to the pivot-shift test and the Lysholm score (SB: mean 91, DB: mean 89) (Mann-Whitney test, T-test). The anterior laxity was not significantly different between group A (mean, 2.2mm) and group B (mean, 0.9mm), according to KT-1000 measurements. Rotational stability, as evaluated by pivot-shift test, was better in group B than in group A, but statistical analysis showed no significant difference. The average operation time was longer in DB (110 min) compared to SB (80 min). There were no infections, though one patient of each group was found to be complicated with fixed flexion and extension lag > 5°; and underwent arthroscopic lysis. Our study shows no statistically significant advantage of DB versus SB ACL reconstruction, concerning the clinical evaluations and the complications

INTRODUCTION. This study aimed to intra-operatively quantify the improvements in knee stability given both by anatomic double-bundle (ADB) and single-bundle with additional lateral plasty (SBLP) ACL reconstruction using a navigation system. MATERIALS AND METHODS. We prospectively included 35 consecutive patients, with an isolated anterior cruciate ligament injury, that underwent both ADB and SBLP ACL reconstruction (15 ADB, 20 SBLP). The testing protocol included anterior/posterior displacement at 30° and 90° of flexion (AP30–AP90), internal/external rotation at 30° and 90° of flexion (IE 30–IE90) and varus/valgus test at 0° and 30° of flexion (VV0–VV30); pivot-shift (PS) test was used to determine dynamic laxity. The tests were manually performed before and after the ACL reconstruction and the data were acquired by means a surgical navigation system (BLU-IGS, Orthokey, USA). Comparisons of pre- and post-reconstruction laxities were made using paired Student t-test (P=0.05) within the same group; comparison between ADB and SBLP groups was indeed performed using independent Student t-test (P=0.05), analysing both starting pre-operative condition and post-operative one. RESULTS. Statistically significant reduction of the global amount of laxity and global displacement was observed for both reconstructions (p<0.05) in all the performed clinical tests. Statistical differences was found between the two reconstruction considering the recovery (pre-post laxities) due to the each reconstruction, in VV0 (SBLP: 3.7±0.2° and ADB: 2.3±0.5°, p<0.0001) and in IE90 (SBLP: 9.2±3.1° and ADB: 5.0±2.8°, p=0.0022). Statistical differences were also found between the two reconstruction considering the recovery of global displacement, in particular for the lateral compartment during AP90 SBLP: 8.8±1.0 mm, ADB: 6.4±0.4 mm, p<0.0001), for the maximal lateral joint opening during VV0 (SBLP: 4.5±1.2 mm, ADB: 1.2±1.1 mm, p<0.0001) and VV30 (SBLP 3.5±1.3 mm, ADB 1.8±0.1 mm, p=0.0013) and both for the medial and lateral AP displacement during IE90 (in in medial compartment SBLP:5.6±0.6 mm, ADB: 2.7±0.7 mm, p<0.0001, in lateral compartment SBLP:8.2±1.0 mm, ADB: 3.9±0.8 mm, p<0.0001). During PS test ADB patients revealed less “hysteresis” after reconstruction (p=0.0005). Moreover SBLP patients presented more acceleration after the reconstruction compared to ADB and more evident displacement (p=0.0009). DISCUSSION. Both the reconstructions worked similarly for what concerns knee static laxity. The considered extra-articular procedure plays an important role in better controlling lateral tibial compartment displacement in drawer test and in controlling maximal lateral joint opening both at 0° and 30° of flexion. On the other hand the ADB reconstruction better restores the dynamic behaviour of the joint under PS test

The purpose of this study is to determine the influence of knee flexion angle for drilling the posterolateral (PL) femoral tunnel during double-bundle anterior cruciate ligament (ACL) reconstruction via the anteromedial (AM) portal on resulting tunnel orientation and length. Methods: In nine fresh cadaveric knees, the ACL was excised and 2.4 mm guide wires were drilled through the PL bundle footprint via an AM portal. We compared knee flexion angles of 90, 110, 130 degrees. AP-, lateral- and tunnel view radiographs were measured to determine tunnel orientation, o’clock position, and direct measurement to determine intra-osseous tunnel length. On AP view, increased flexion resulted in more horizontal tunnels. The angles were 31.9 ± 7.1°, 26.4 ± 8.9° and 23.0 ± 8.1° for 90°, 110° and 130°. The pin orientation was significantly different when comparing 90° and 130°. On lateral view, increased flexion resulted in more horizontal tunnels. The angles were 68.9 ± 19.9°, 50.4 ± 11.6°, 31.3 ± 12.3° for 90°, 110° and 130°. On tunnel view, pin orientation was 22 ± 8.2°, 28.3 ± 6.7° and 35.9 ± 6.2° for 90°, 110° and 130°. Mean o’clock position was 09:00 ± 0:12. Intra-osseous length of the pins did not significantly change with knee flexion. The exit of the pins on the lateral femur with regard to femoral attachment of the LCL was proximal. The distance was 0.1 ± 6.6 mm, 6.4 ± 6.4 mm and 9.2 ± 2.4 mm for 90°, 110° and 130°. This was significant when comparing 90° and 130°. The shortest distance between the exit and the posterior femoral cortex was 4.0 ± 1.8 mm, 9.7 ± 3.5 mm, and 13.2 ± 2.8 mm for 90°, 110° and 130°. All values were significant. Conclusion: At 110°, exit of the PL pin is close to the attachment of the LCL. 90° flexion risks damage to the LCL and posterior cortex blow-out. Thus we recommend drilling the PL tunnel at 130° of knee flexion

The kinematic effect of tunnel orientation and position, during ACL reconstruction, has been only recently related to the control of rotational instability.

This paper presents a detailed computer-assisted in vitro evaluation of two different femoral tunnel orientations with the same tunnel position, at 10.30 ‘o clock, during the intervention of ACL reconstruction with double bundle technique. Results highlighted better kinematic performances of the horizontal tunnel, with respect to the vertical one, in controlling antero-posterior (AP) laxities at 30°, and internal-external (IE) laxities.

Elongations of anterior and posterior bundles of reconstructed ACL, for both reconstruction, decreased during PROM respectively by 20% and 40%. Total length of the graft varied during PROM, mainly due to graft elongation during tests, graft length on horizontal tunnel varied from 237 to 213mm while graft length on vertical tunnel varied from 257 to 233mm. Kinematic tests showed a better performance of horizontal tunnel in the control of IE rotations at 30° and 90° and of the Lachman test with respect to the vertical one. Stability was restored with both reconstructions.

We report the clinical outcome and findings at second-look arthroscopy of 216 patients (mean age 25 years (11 to 58)) who underwent anterior cruciate ligament (ACL) reconstruction or augmentation. There were 73 single-bundle ACL augmentations (44 female, 29 male), 82 double-bundle ACL reconstructions (35 female, 47 male), and 61 single-bundle ACL reconstructions (34 female, 27 male). In 94 of the 216 patients, proprioceptive function of the knee was evaluated before and 12 months after surgery using the threshold to detect passive motion test. Second-look arthroscopy showed significantly better synovial coverage of the graft in the augmentation group (good: 60 (82%), fair: 10 (14%), poor: 3 (4%)) than in the other groups (p = 0.039). The mean side-to-side difference measured with a KT-2000 arthrometer was 0.4 mm (-3.3 to 2.9) in the augmentation group, 0.9 mm (-3.2 to 3.5) in the double-bundle group, and 1.3 mm (-2.7 to 3.9) in the single-bundle group: the result differed significantly between the augmentation and single-bundle groups (p = 0 .013). No significant difference in the Lysholm score or pivot-shift test was seen between the three groups (p = 0.09 and 0.65, respectively). In patients with good synovial coverage, three of the four measurements used revealed significant improvement in proprioceptive function (p = 0.177, 0.020, 0.034, and 0.026). We conclude that ACL augmentation is a reasonable treatment option for patients with favourable ACL remnants. Cite this article: Bone Joint J 2014;96-B:1325–32

Purpose. The purpose of this study was to determine whether intra-operative identification of osseous ridge anatomy (lateral intercondylar “residents” ridge and lateral bifurcate ridge) could be used to reliably define and reconstruct individuals' native femoral ACL attachments in both single-bundle (SB) and double-bundle (DB) cases. Methods. Pre-and Post-operative 3D, surface rendered, CT reconstructions of the lateral intercondylar notch were obtained for 15 patients undergoing ACL reconstruction (11 Single bundle, 4 Double-bundle or Isolated bundle augmentations). Morphology of native ACL femoral attachment was defined from ridge anatomy on the pre-operative scans. Centre's of the ACL attachment, AM and PL bundles were recorded using the Bernard grid and Amis' circle methods. During reconstruction soft tissue was carefully removed from the lateral notch wall with RF coblation to preserve and visualise osseous ridge anatomy. For SB reconstructions the femoral tunnel was sited centrally on the lateral bifurcate ridge, equidistant between the lateral intercondylar ridge and posterior cartilage margin. For DB reconstructions tunnels were located either side of the bifurcate ridge, leaving a 2mm bony bridge. Post-operative 3D CTs were obtained within 6 weeks post-op to correlate tunnel positions with pre-op native morphology. Results. Pre-op native ACL attachment site morphology was very similar to previous in-vitro studies: the mean centre was found at 27% along Blumensaat's line (range 19-33%) and 38% the width of the lateral femoral condyle (range 31-43%). Despite the variability between individuals there was close correlation between pre-operative localization of the femoral attachment centre and position of single bundle ACL reconstructions tunnels on the post-op CT (R=0.92). Similar results were observed for double-bundle and isolated bundle augment reconstructions. Conclusion. ACL attachment site morphology varies between individuals. Intra-operative localization of the osseous landmarks (lateral intercondylar and bifurcate ridges) appears to lead to accurate, individualised anatomical tunnel placement whether using single or double-bundle reconstruction techniques

To evaluate in-vivo the effectiveness of the double bundle technique for Anterior Cruciate ligament (ACL) reconstruction in restoring knee rotational stability under varying dynamic loading conditions. The study group included 10 patients who underwent double-bundle ACL reconstruction with hamstrings tendon autograft, 12 patients with single-bundle reconstruction, 10 ACL deficient subjects and 12 healthy control individuals. Kinematic and kinetic data were collected using an 8-camera optoelectronic motion analysis system and one force plate. Knee rotational stability was examined during two maneuvers: a combined 60o pivoting turn and immediate stairs ascend and a combined stairs descend and immediate 60o pivoting maneuver. The two factors evaluated were the maximum. There were no significant differences in tibial rotation between the four groups in the examined maneuvers. Tibial rotation in the single- and the double-bundle groups were even lower than the control group. Rotational moments did not differ significantly between the four groups in any of the examined maneuvers. In general, rotational moments in the affected side of the ACL reconstructed and deficient groups were found reduced compared to the unaffected side. Double-bundle reconstruction does not reduce knee rotation further compared to the single-bundle technique during dynamic stability testing under varying conditions. The injured side of ACL reconstructed or deficient individuals is exposed to substantially lower rotational moment compared to the intact side

A total of 108 patients with unilateral instability of the knee, associated with rupture of the anterior cruciate ligament, was prospectively randomised for arthroscopic single- or double-bundle reconstruction of the ligament using hamstring tendons. The same postoperative rehabilitation protocol was used for all. The patients were followed up for a mean of 32 months (24 to 36). We measured the anterior laxity and joint position sense at different angles of flexion of the knee to determine whether both bundles in the double-bundle reconstruction contributed to the stability of the joint and proprioception. No significant difference was found between the two groups with regard to anterior laxity measured by the KT-2000 arthrometer with the knee at 20° or 70° flexion nor with regard to proprioception. A notchplasty was required less often in the double- compared with the single-bundle reconstruction. We did not find any advantage in a double-bundle as opposed to a single-bundle reconstruction in terms of stability or proprioception

Aim: To determine the quantity and the quality of the bone bridge between the bone tunnels, in both the femoral and tibial side, after double-bundle anterior cruciate ligament (ACL) reconstruction. Material and methods: Twenty-seven patients undergoing primary double-bundle ACL reconstruction with hamstring tendon autograft were included in this prospective study. Computed tomography (CT) was performed in all patients at a mean of 13 months postoperatively. The amount of the bone bridge between the bone tunnels was measured, in both the femoral and tibial side, on an axial plane at three locations:. at the level of the joint line. at the mid-portion of the bone bridge and. at the base of the bone bridge. In addition, the bone density of the bone bridge was measured in Hounsfield units (HU) in the same locations. Bone density of the anterior tibial cortex lateral femoral condyle, and adjacent cancellous area, and were measured for comparisons. Results: CT confirmed that the bone bridge was triangular in shape in all cases in both the femoral and tibial side. On the femoral side, at the level of joint line (apex of the bone bridge) the mean thickness of the bone bridge was 1.7 mm, at the mid-portion the mean thickness of the bone bridge was 3.7 mm and at the base of the bone bridge the mean thickness was 7.1 mm. On the tibal side, at the level of joint line (apex of the bone bridge) the mean thickness of the bone bridge was 1.5 mm, at the mid-portion the mean thickness of the bone bridge was 3.2 mm and at the base of the bone bridge the mean thickness was 6.5 mm. Bone density at the mid-portion and at the base of the bone bridge was similar to the cancellous bone for both the femoral and tibial side. However, the bone density of the bone bridge, at the level of the joint line, for the femoral side was 860 HU and this was not statistically significant in comparison to the density of the lateral femoral cortex (960 HU). Similarly, the bone density of the bone bridge, at the level of the joint line, for the tibial side was 885 HU and this was not statistically significant in comparison to the density of the anterior tibial cortex (970 HU). Conclusions: Our study demonstrated one year after double-bundle ACL reconstruction the thickness of the triangular bone bridge between the bone tunnels is sufficient at the mid-portion and at the base of the triangle but is thin at the level of the joint line. However, the bone bridge at the apex of the triangle is very strong since its density is similar to that of cortical bone. We believe that the “corticalization” of the bone bridge at the level of the joint line on both the femoral and tibial side is important and contributes significantly to avoid communication of the bone tunnels

We have assessed the biomechanical properties of a 'double-bundle' prosthetic ligament replacing the anterior cruciate in cadaver knees. We compared the results with those of single bundle 'over-the-top' and 'through-the-condyle' techniques, performing anterior drawer tests at 20 degrees and 90 degrees knee flexion. The over-the-top reconstruction gave better anteroposterior stability at 20 degrees, while the through-the-condyle repair was more stable at 90 degrees. The double-bundle reconstruction gave practically normal anterior stability at both 20 degrees and 90 degrees

Objectives. This study investigated the biomechanical performance of decellularized porcine superflexor tendon (pSFT) grafts of varying diameters when utilized in conjunction with contemporary ACL graft fixation systems. This aimed to produce a range of ‘off-the-shelf’ products with predictable mechanical performance, depending on the individual requirements of the patient. Methods. Decellularized pSFTs were prepared to create double-bundle grafts of 7 mm, 8 mm, and 9 mm diameter. Femoral and tibial fixation systems were simulated utilizing Arthrex suspension devices and interference screws in bovine bone, respectively. Dynamic stiffness and creep were measured, followed by ramp to failure from which linear stiffness and load at failure were measured. The mechanisms of failure were also recorded. Results. Dynamic stiffness was found to increase with greater graft diameter, with significant differences between all groups. Conversely, dynamic creep reduced with increasing graft diameter with significant differences between the 7 mm and 9 mm groups and the 8 mm and 9 mm groups. Significant differences were also found between the 7 mm, 8 mm, and 9 mm groups for linear stiffness, but no significant differences were found between groups for load at failure. The distribution of failure mechanisms was found to change with graft diameter. Conclusion. This study showed that decellularized pSFTs demonstrate comparable biomechanical properties to other ACL graft options and are a potentially viable option for ACL reconstruction. Although grafts can be stratified by their diameter to provide varying biomechanical properties, it may be more appropriate to alter the fixation technique to stratify for a greater diversity of biomechanical requirements. Cite this article: Bone Joint Res 2019;8:518–525

The concept of decellularised xenografts as a basis for anterior cruciate ligament (ACL) reconstruction was introduced to overcome limitations in alternative graft sources such as substantial remodelling delaying recovery and donor site morbidity. This study aimed to measure the biomechanical properties of decellularised porcine super flexor tendon (pSFT) processed to create ACL grafts of varying diameters, with a view to facilitating production of stratified ‘off the shelf’ products with specified functional properties for use in ACL reconstructive surgery. Decellularisation was carried out using a previously established procedure, including antibiotic washes, low concentration detergent (0.1% sodium dodecyl sulphate) washes and nuclease treatments. Decellularised pSFTs were prepared to create double-bundle grafts of 7, 8 and 9mm diameter (n=6 in each group). Femoral and tibial fixations were simulated utilising Arthrex suspension devices (Tightrope®) and interference screws in bovine bone respectively. Dynamic stiffness and creep were measured under cyclic loading between 50–250N for 1000 cycles at 1Hz. This was followed by ramp to failure at 200mm/min from which linear stiffness and load at failure were measured. Data were analysed using either 1- or 2-way ANOVA as appropriate with Tukey post-hoc analysis (p<0.05). Significant differences were found between all groups for dynamic stiffness and between 7 & 9mm and 8 & 9mm groups for dynamic creep. Significant differences were also found between 7, 8 & 9mm groups for linear stiffness (167.8±4.9, 186.9±16.6 & 216.3±12.4N/mm respectively), but no significant differences were found between groups for load at failure (531.5±58.9, 604.1±183.3 & 627.9±72.4N respectively). This study demonstrated that decellularised pSFTs possess comparable biomechanical properties to other ACL graft options (autografts and allografts). Furthermore, grafts can be stratified by their diameter to provide varying biomechanical profiles depending on the anatomy and individual needs of the recipient

We have shown in a previous study that patients with combined lesions of the anterior cruciate (ACL) and medial collateral ligaments (MCL) had similar anteroposterior (AP) but greater valgus laxity at 30° after reconstruction of the ACL when compared with patients who had undergone reconstruction of an isolated ACL injury. The present study investigated the same cohort of patients after a minimum of three years to evaluate whether the residual valgus laxity led to a poorer clinical outcome. Each patient had undergone an arthroscopic double-bundle ACL reconstruction using a semitendinosus-gracilis graft. In the combined ACL/MCL injury group, the grade II medial collateral ligament injury was not treated. At follow-up, AP laxity was measured using a KT-2000 arthrometer, while valgus laxity was evaluated with Telos valgus stress radiographs and compared with the uninjured knee. We evaluated clinical outcome scores, muscle girth and time to return to activities for the two groups. Valgus stress radiographs showed statistically significant greater mean medial joint opening in the reconstructed compared with the uninjured knees (1.7 mm (. sd. 0.9) versus 0.9 mm (. sd. 0.7), respectively, p = 0.013), while no statistically significant difference was found between the AP laxity and the other clinical parameters. Our results show that the residual valgus laxity does not affect AP laxity significantly at a minimum follow up of three years, suggesting that no additional surgical procedure is needed for the medial collateral ligament in combined lesions