COMPARISON OF HAMSTRING AND LARS HAMSTRING AUGMENTATION DOUBLE BUNDLE ACL RECONSTRUCTION- Minimum 2 year follow-up

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1 COMPARISON OF HAMSTRING AND LARS HAMSTRING AUGMENTATION DOUBLE BUNDLE ACL RECONSTRUCTION- Minimum 2 year follow-up Travis Falconer, Danè Dabirrahmani, Louise Tusak, Joanne Pollock, Bill Breidahl, Peter Annear Introduction The aim of an ACL reconstruction is to restore knee stability, functionality and allow the patient to return to their normal level of activity. Whilst the ideal reconstruction technique is still under much debate, current thinking is shifting towards anatomical reconstructions. Results from biomechanical studies have shown that positioning the tunnels in the native footprints as well as reconstructing the double bundle structure, better creates rotational stability and functionality. The Remnant Retention technique for Anatomical ACL reconstruction involves retention of the ACL stump and notch tissue. This allows accelerated revascularisation and ligamentisation of the graft, preservation of pro-prioception of the nerve fibres, and hence an enhanced biological environment for healing within the tunnel. This technique has been used both in autologous and synthetic grafts. The Ligament Augmentation and Reconstruction (LARS), a synthetic graft system, encourages preservation of the ACL stump, as it can promote tissue ingrowth. The LARS ligament has been used where accelerated rehabilitation is critical. Due to its synthetic nature, it possesses its full strength from day 1, and therefore particularly useful in patients requiring accelerated rehabilitation. There is a plethora of data indicating good outcomes for anatomically reconstructed knees with autologous grafts. There is however, little data on synthetic grafts. The aim of this study was to compare clinical evaluation, radiological outcomes as well as subjective and objective scores between a double bundle hamstring reconstruction technique (control group) and the LARS hybrid double bundle reconstruction technique (LARS group). We hypothesise that the augmented AM bundle LARS reconstruction is similar to the hamstring double bundle reconstruction in terms of clinical evaluation, radiological outcomes and functional scoring; and that the results indicate a safe and desirable clinical outcome. Materials and Methods Between August 2008 and December consecutive patients undergoing ACLR consenting to clinical and gadolinium enhanced MRI follow up were identified. From this reconstruction cohort, 27 were reconstructed using the standard double bundle hamstring technique (control group). This comprised the semitendinosus for the anteromedial (AM) bundle and gracilis for the posterolateral (PL) bundle. All other patients received a double bundle reconstruction with an augmented synthetic LARS (Ligament Augmentation and Reconstruction System, Corin) anteromedial (AM) bundle (LARS group). This reconstruction combined the LARS-IC133 synthetic ligament with the semitendinosus as the AM bundle; and the PL bundle remained as the gracilis tendon (Figure 1).

2 Patients enrolled (n = 88) Group 1- (n=27) ACL Double Bundle Reconstruction AM bundle- Semitendinosus PL bundle- Gracilis Group 2- (n=61) ACL Double Bundle Reconstruction AM bundle- Semitendinosus + LARS-IC133 PL bundle- Gracilis Figure 1: Study groups The inclusion criteria were primary ACL reconstructions in consenting, skeletally mature patients with an isolated injury and at least three weeks post-acute ACL rupture. Patients were excluded if they had another ligamentous injury in the ipsilateral knee, any prior revision surgery, required a meniscal repair at the time of surgery or if they were a workers compensation case. Ethical approval was sought from the local Ethics Committee review board at The Mount Hospital, Perth, Western Australia, and all participating patients provided consent. Surgical Technique All reconstructions were performed by a single senior surgeon (PA). All patients were operated on within 3 months of their injury. An arthroscopy assisted anatomical reconstruction technique was performed with the patient supine, with a high tourniquet and the leg free from a brace. A standard arthroscopy was performed and any small meniscal tears resected and loose material removed. A standard arthroscopic assisted double bundle ACL reconstruction was performed. All meniscal and chondral surgery was performed prior to the reconstructive procedure. Autologous hamstrings were harvested from the same limb through a 3cm incision above the pes anserinus. The grafts were prepared from the two cohorts as described above. All graft bundles were suspended over a closed endobutton (Smith & Nephew). The tunnel preparations were performed using a remnant sparing technique. There was minimal debridement of the femoral notch and tibial ACL stump. This involved only shaving the fat pad and ligamentum mucosum to gain an appropriate view, and a small window of the posterior lateral wall of the notch in the 1:30 o clock position (left knee) with the knee at 90 flexion. The entire stable remnant ACL tibial attachment was left intact. The position of the anteromedial bundle (AMB) was marked with an awl 5mm from the posterior wall, in the 1:30 o clock position with respect to the long axis of the femur. The position of the posterolateral bundle (PLB) was then marked with an awl using the AMB as a reference. It is marked on a line 30 inferiorly from the long axis of the femur and 8mm below the AMB. This point is normally approximately 5mm from the medial and posterior edge of the articular cartilage of the lateral femoral condyle within the posterolateral bundle of the femoral footprint. A new central and inferomedial portal was created and the knee

3 hyperflexed to allow drilling of long (>35mm) tunnels. Tunnels were then drilled and prepared for Endobutton femoral fixation. The tibial tunnels were then prepared using the intact tibial remnant to define tunnel position. For the anteromedial tunnel the Acuflex drilling jig set to aim at the elbow of the device with a starting point on the medial side of the tuberosity 3cm below the joint line. The tip of the jig was then placed 8mm posterior to the anterior margin of the ACL stump so that the guide wire entered the center of the remnant stump. The AMB tunnel was drilled at 90 degrees flexion and care was taken not to penetrate the stump. The jig was then placed with a start position lateral to the medial collateral ligament insertion 2.5cm below the joint line. The tip of the guide was then positioned so that the guide wire entered the stump on the posterolateral margin. The PLB was then drilled with the knee in 90 degrees of flexion. The AMB was completed by carefully shaving a tunnel in the line of the intact tibial remnant. The PLB was completed by shaving a tunnel through the intact remnant. A guide wire was then used to pass the suture shuttle from the inferomedial portal through the tunnels. The PLB was passed first, followed by the AMB. The PLB was fixed distally with a bioabsorbable interference screw (Depuy Mitek) and the AMB was fixed with a size dependent Intrafix webbing and screw. Differences in surgical technique between cohorts: Graft Configuration: In the control cohort the AMB was constructed on a 20mm closed loop endobutton using doubled semitendinosis. The study cohort AMB was constructed on a closed 20mm endobutton loop using a hybrid graft of double semitendinosis and a doubled LARS 133 prosthesis. The prosthesis added 1mm of tunnel diameter (cross sectional area of 9mm^2). The PLB configuration (doubled graciliis on 20mm closed loop endobutton) was the same in both groups. Graft tensioning: The control cohort AMB was tensioned in 45 degrees and the PLB in 20 degrees of flexion. In the LARS group both bundles were tensions in full hyperflexion. Rehabilitation Control group: All patients were allowed to weight bear as tolerated with crutches and a Richards splint on day one post operatively. They remained in the splint for ambulation for the first two weeks and started gentle range of motion exercises focusing on swelling reduction and regaining full extension. All patients were seen by a single senior physiotherapist. Patients were allowed to cease the use of the brace once their knee effusion had resolved. They were commenced on closed chain exercises, hydrotherapy and stationary cycling at 6 weeks. At four months post operatively they commenced jogging, progressing to change of direction exercise and sport specific exercises by six months. They were then commenced on full sport and pivoting activities at 9-12 months post operatively. LARS group: The first 3 weeks were similar to the control group. The rehabilitation program was accelerated thereafter, with patients commencing closed chain exercises and cycling at week three, straight line jogging at two months and sport specific exercises at four months. Full sport was prescribed as early as 5-6 months post operatively. Progression was dictated by the ability to maintain knee motion and a fluid free knee. An overview of the rehabilitation program for each group is shown in Table 1.

4 Table 1: Rehabilitation Protocol for each group Closed Chain Exercise & Cycling Straight line jogging Sport Specific Exercises Full Sport 6 weeks 4 months 6-9 months 9-12 months 3 weeks 2 months 4 months 5-6 months Clinical Assessment A single assessor reviewed all patients at 2 years post operatively. Their clinical assessment included, presence of knee effusion and a clinical Cyclops lesion, range of movement (measured with a goniometer) and ligamentous grading, specifically Lachman s tests. These were compared to the contralateral side. Ligamentous laxity was also tested using the KT-1000 arthrometer also comparing the reconstructed side to the uninjured leg. Questionnaires included the International Knee Documentation Committee (IKDC) Subjective and Objective score, Tegner Activity Score, Cincinnati Knee Rating System, Lysholm Knee Scale, ACL Quality of Life Score (ACL QOL), and the ACL Recovery Score. Patients also graded their graft site pain using a visual analogue scale and performed a single leg hop test. In order to quantify the rate at which patients recovered a new scoring system was developed that addressed the time taken to achieve both activities of daily l iving and sports related activities during the post-operative period. This ACL Recovery Score examined 10 criteria related to everyday daily living tasks and 9 sport specific tasks (Table 2). Patients were then asked to fill in the number of weeks it took them to achieve these tasks. Each score was given a percentage according to the time at which the questionnaire was asked, that is for example if a patient took 2 weeks to be free of crutches their score was 2/52 at 1 year or 2/104 at 2 years. These percentages were added for all criteria and the average taken as an overall score. Therefore, the lower the patients score the faster they recovered. If patients were unable to achieve a particular criteria (eg. Level 3 sports), they were given a score of 52/52 or 104/104. For those criteria related to driving if they did not have a drivers license or a manual or automatic car, these criteria were excluded. Table 2: The ACL Recovery Score Activities of Daily Living Walk without crutches Walk without a limp Walk on uneven ground Climb a flight of stairs Stand one leg (reconstructed knee) Drive a car (automatic) Drive a car (manual) Return to light manual work (eg desk job) Return to moderate manual work (eg domestic work) Return to heavy manual work (eg building) Time to Achieve in Weeks Sport Specific Activities Achieve full range of movement Jogging Stationary cycling Road cycling Running (full pace, straight line) Running with change of direction Level 1 Sports (Jogging, golf, tennis, badminton, cricket) Level 2 Sports (Squash, basketball, netball, athletics) Level 3 Sports (Football, rugby, soccer, hockey) Time to Achieve in Weeks

5 Radiological Assessment At the 24-month assessment all patients had a MRI of the knee performed. All scans were performed on a 1.5T MRI (Signa Excite, GEMedical Systems, Milwaukee, Wis) using a dedicated 8 channel knee coil. Imaging was confined to 2mm thick slices with a 0.5mm gap between each slice and coronal, axial and sagittal sequences were performed. Oblique axial T1w (TR =640ms, TE = 16ms) fat suppressed sequences were obtained through the graft pre and post IV gadolinium. MRI was used to assess the signal intensity of the ACL, tunnel positi ons, graft impingement, cyclops lesions and tunnel confluence. The signal intensity of the AMB, PLB, PCL and the graft surrounds were measured as previously described by Gohil et al [1] using a GE workstation, and from this the Signal Noise Quotient (SNQ) calculated to give a quantitative measure of graft vascularity. The area of interest for the bundles and the PCL in this study was the mid portion of the reconstructed bundles and the native PCL. The aim was to assess potential graft shielding in the augmented group (LARS). All patients underwent a lateral plain film x-ray with the knee in full extension. This image was then fused with the sagittal slice on the MRI which best displayed the femoral tunnel insertion point on the medial wall of the lateral femoral condyle (Figure 2). The Radiographic Quadrant method as described by Bernard et al [2] was used to quantify this position. Bernard et al used Blumensaat s line and a line parallel to it at the most distal edge of the lateral femoral condyle to determine the depth of position on the wall. They then used the tangent to Blumensaat s line where it exited the femoral condyle most anteriorly and a second tangent where Blumensaat s line exited the condyle most posteriorly to determine the height on the wall of the condyle (Figure 2). Bernard et al proposed that the AMB position should be positioned ¼ along the depth of the condyle and ¼ along the height of the condyle as shown. The tibial attachments were measured in relation to Amis and Jakob s Line [3] as a percentage of the anteroposterior (AP) distance of the tibial plateau as described in a cadaveric study by Colombet et al. [4] Their study showed that the AMB attachment should be at a distance 36% of the AP of the tibial plateau and the PLB attachment 52% of that distance. The appearance of the grafts at the joint interface was also observed on coronal and sagittal views and the distance between the center of the tunnels measured. If there was no bony bridge visible then the tunnels were deemed to be confluent. Height Depth Figure 2: X-ray image fused with MRI, superimposed by the Radiographic Quadrant (left) and Amis & Jakob s line (right)

6 Statistical Analysis The student t-test was used to compare continuous data between the two different reconstruction groups. Chi-squared test was used to analyse the categorical data, such as the presence of Cyclops lesions, loss of knee extension as well as presence of confluence and the objective IKDC scoring. The level of statistical significance was set at p<0.05. All statistical analysis was performed using SPSS software (SPSS 18, SPSS Inc, Chicago Ill). Results Between August 2008 and December 2012, 88 patients (27 control and 61 LARS) were enrolled to take part in this study. Four were lost to follow-up. There were 14 females and 13 males in the control group with an average age of 34 (SD 18) and 19 females and 42 males in the LARS group with an average age of 35 (SD 11). The average time to the final review was 781 days (2.14 years) for the control group and 901 days (2.46 years) for the LARS group (Table 3). Table 3: Patient Demographic Data (n = 27) (n = 61) Age, years (mean ± SD) 34 (18) 35 (11) Male/female 13/14 42/19 Time to follow up (mean ± SD) 2.14 (0.65) 2.46 (0.93) Clinical Assessment Knee function and stability were assessed for 84 of the 88 patients. The range of motion results (extension and flexion) are shown in Table 4. The LARS group presented slightly more extension. But there were no significant differences in range of motion in general. Table 4: Range of Motion and anterior translation using the Lachman test (n = 25 ) (n = 59 ) Extension ( ) Flexion ( ) There was, however, a statistically significant difference (p<0.05) in loss of extension between the two groups. The control group displayed loss of extension in 32% of patients at 24 months; in contrast to a 12% loss in the LARS group. Of the patients with loss of extension, the average loss in the control and LARS groups were: 3.63 and 2.86, respectively. Table 5: Number of patients showing loss of extension and amount of loss. (n = 25) (n = 59) No of patients with loss of extension* 8 (32%) 7 (12%) Average loss of extension 3.00 (SD2.29) 2.86 (SD1.07) * statistically significant (p<0.05)

7 The ligamentous laxity was most accurately measured with the KT-1000 arthrometer. Side to side (SSD) KT-1000 differences in anterior translation for the two groups are shown in Table 6. The mean SSD in the control group was 0.65mm (range -1.7 to 3.3) and 0.44mm (range -3.3 to 4.7) in the LARS group. The percentage of patients with a negative SSD in the control and LARS groups was 32% and 30.5%, respectively. Lachman test results also did not show any significant differences between the two cohorts. Table 6: Number of patients showing negative SSD in anterior translation (n = 25,25) (n = 59,61) No of patients with Negative SSD using KT- 8 (32%), 18 (30.5%), 1000 Average Side to Side differences (KT-1000) 0.65mm (SD1.37) 0.44mm (SD1.64) No of patients with Negative SSD using 2 (8%) 6 (10%) Lachman test, Average Side to Side differences (Lachman) 0.78mm (SD0.94) 1.09mm (SD0.52) Visual Analogue Scale (VAS) scores showed all patients as scoring nil in both the control and LARS cohorts. There was one exception in the control group, with a patient scoring pain of 2/10. Outcome Measures The average scores for outcome measures for the control and LARS groups, respectively, were as follows: Tegner Score 6.58 and 6.39 out of 10; Cincinatti and out of 420; Lysholm Knee Scale and out of 95; ACL QOL 80 and out of 100. The average IKDC subjective scores were and for the control and LARS groups, respectively. Differences in the scores were not statistically significant (Table 7). Table 7: Outcome Measures Evaluation Scores (n = 27) (n = 61) Tegner Score Cincinatti Score Lysholm Score IKDC Subjective ACL QOL The IKDC objective scores are shown in Table 8. The LARS group displays an overwhelming majority of A scores (62% of LARS patients scored A), compared with 48% of the control group. Table 8: IKDC Objective Score (n = 25) (n = 60) A 12 (48%) 37 (62%) B 11 (44%) 22 (37%) C 1 (4%) 1 (1%) D 1 (4%) 0 (0%)

8 Table 9 shows the ADL, Sports and combined ACL Recovery Scores. In all cases the LARS group displayed lower values. These results, however, were not statistically significant. Table 9: ACL Recovery Score (n = 25) (n = 59) ADL Score Sports Score Total (ACL Recovery Score) Radiological Assessment The position of the AMB and PLB insertions on the tibia were determined relative to the position along the Amis and Jakob s line and the position of the (AMB) insertion on the femoral side was determined by Bernard and Hertel s Radiographic Quadrant Method. In both cases results were similar between the control and LARS groups (Table 10). The average tibial position of the AMB was 39.22% and 38.27% and the PLB was 53.99% and 52.87% of Amis and Jakob s line, for the control and LARS groups, respectively. Normal values, according to Amis & Jakob [3] are 36% for the AMB and 52% for the PLB. AMB Femoral tunnel positions were described using Bernard & Hertel s Quadrant method on fused MRI-xray images. The average height and depth coordinates, respectively, for the control group was (74.04%, 70.45%) and for the LARS group was (75.42%, 71.89%). No significant difference was found. (Normal values, according to Bernard et al [2] for height and depth are 75% and 71%, respectively) Table 10: Tibial and Femoral Tunnel Positions (n = 27) (n = 61) Tibial AMB Position (27) (57) Tibial PLB Position (26) (56) Femoral AMB Height*(%) (17) (26) Femoral AMB Depth* (%) (17) (26) * Percentage based on the Radiographic Quadrant The 2 year MRI scans provided the average Signal Noise Quotient (SNQ) post contrast of the two bundles of the ACL and the PCL. The AMB average was 2.59 and 3.46; the PLB average was 3.05 and 3.52; and the PCL average was 2.07 and 2.21, for the control and LARS groups, respectively. The AMB signal was statistically higher in the LARS group. Two patients in the control group refused contrast and three patients in the LARS group either had too much artefact or graft had been excised, and therefore not included in data.

9 Table 11: Signal Noise Quotient (SNQ) (n = 25) (n = 58) SNQ AMB 2.59* 3.46* SNQ PLB SNQ PCL * Statistically significant (p<0.002) **Statistically significant (p<0.02) Based on the MRI scans, the LARS group had a higher presence of Cyclops lesions with 25% of patients identified. Five patients from the LARS cohort returned to theatre. One patient underwent a chondroplasty due to subsequent injury. Another patient had minor clean-up of tissue. No synovitis or graft rupture was seen. A relatively tight knee in another patient found Cyclops lesion impinging. A notchplasty was undertaken to provide more space. Anterior knee pain in another patient revealed a ruptured LARS but intact hamstring. This knee was determined as functional. One final patient experienced a LARS rupture, bringing the percentage of LARS ligament ruptures in this study to 1.7%. Discussion Whilst autologous grafts have been widely used for many years with good outcomes, the synthetic graft has only gained acceptance in recent years. Early synthetic grafts first showed promising results but in the longer term were fraught with mechanical failures and complications [5]. Immunological responses, osteolysis, foreign-body synovitis and graft rupture were some of issues reported [6-8]. The newer generation synthetic grafts have been designed with more biocompatible and robust materials and a better understanding of knee kinematics [5, 9, 10]. The LARS ligament is made from polyethylene terephthalate material. Its intended use is a scaffold to encourage tissue in-growth while protecting the ACL during healing [9]. It is expected that this scaffold in conjunction with the surgical technique of preserving the ACL stump and anatomical placement provides the optimal condition for healing to occur and for long-term function of the joint. Numerous clinical studies have reported on the LARS ligament [7, 8, 11, 12]. These are usually single bundle ACL reconstructions and either reporting LARS results alone or in comparison with the conventional hamstring or bone-patellar-bone grafts. This study compared a cohort of patients undergoing LARS hybrid double-bundle reconstruction (LARS group) with a cohort of patients undergoing a double-bundle hamstring reconstruction (control group). To the authors knowledge this is the first time a hybrid LARS reconstruction has been reported. The hybrid double bundle comprised of a semitendinosus tendon and LARS IC133 graft. The minimum two year results in this study overall have displayed a LARS reconstruction which is comparable to a conventional double bundle hamstring reconstruction. Subjective outcome scores showed high patient satisfaction in both cohorts. Functional outcome scores were also comparable, with no statistical difference. Range of motion was similar between the two cohorts. However, the control group did display a loss of extension compared with the LARS group. This may be related to the difference in graft tensioning as discussed earlier. Although this may suggest that the control group had a

10 tighter graft, the KT-1000 side to side differences clearly indicated no loosening in the LARS group. SNQ is commonly used to quantitatively determine the normalised signal intensity of the graft [9]. MRI with the use of gadolinium contrast agent has been a valuable tool in providing information regarding the vascular state of the graft tissue [10]. Weiler et al [13] demonstrated using an animal model that the signal intensity changes in the graft tissue reflect the vascularity and biomechanical properties. Additionally, SNQ was correlated with degree of vascularity. Gohil et al [6] calculated the SNQ from measured signal intensity at different time points and found that minimal debridement of the stump of the ruptured ACL accelerated revascularisation of the hamstring autograft, as indicated by the increased signal. The reascularisation of the human hamstring graft in the early weeks is said to correlate with the proliferation phase of the graft healing [14]. Radiological assessments in this study showed the PCL and PL bundle have no difference between the two cohorts, but there was a statistically significant difference in the SNQ of the AMB in the LARS group. The AMB is the only difference between the two groups and this result is not surprising, as they would most likely have two different rates of vascularisation due to their different materials. There is a possibility that this is the sign of stress-shielding. However, this cannot be confirmed at this early stage and needs longer term follow-up. A higher incidence of cyclops lesions was observed in the LARS patients. It is possible that the accelerated rehabilitation may have caused these MRI Cyclops lesions. However, these are only clinically significant if they result in a loss of extension, which has not been the case in this series. It is also important to realise that MRI Cyclops lesions are different to Clinical Cyclops lesions. The former is due to bunching of the notch tissue usually anterior to the graft on the coronal MRI and the latter is usually associated with loss of full extension and impingement pain[15]. In order to better define the speed of the recovery, the authors of this study have developed a new scoring system. This is important in defining the value of the augmentation technique and the acceleration. It is clear from the results obtained that the LARS patients have a quicker recovery, whilst obtaining the same level functionality and satisfaction. This study has a few shortcomings. While the ACL recovery score provides some very useful information, it still requires validation. Also, the use of the radiographic quadrant method, fusing a MRI with a plain film x-ray image, requires validation and further investigation. This study found the LARS augmentation in the AMB to provide safe accelerated rehabilitation without graft stretching, early return to sports activities and good clinical outcomes at 2 years post-op. Conclusion This study has shown that the LARS augment in a double bundle reconstruction, has the benefit of a quicker recovery, whilst maintaining the same level of satisfaction and outcomes as a conventional autologous graft double bundle reconstruction. Source of Funding The authors would like to thank Corin Australia for funding all of the radiographic and analysis costs.

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