Skin sensory change after arthroscopically-assisted anterior cruciate ligament reconstruction using medial hamstring tendons with a vertical incision

The purpose of this study was to clarify and document light-touch sensory change of the lower leg after arthroscopically-assisted ACL reconstruction using medial hamstring tendons with a vertical incision. Eighty-six patients were directly followed up during a mean of 32.0 months after surgery. Sixty patients responded to a mailed questionnaire about affect of sensory change on daily living. Forty-seven patients out of 86 (55%) indicated some sensory change of the lower leg, which was usually hypoesthesia with an average verbal score of 6.9. The questionnaire revealed that one patient out of 60 complained that the sensory change adversely affected daily living. A sensory-change area with a mean of 53.2 cm² was located distally from the incision in 40% of the cases; it was located proximally and distally in 56%. Blunt exposure for harvesting the tendons failed to decrease the occurrence of the sensory change. After ACL reconstruction using medial hamstring tendons with a vertical incision, sensory change was frequently found. Daily living was, however, only slightly affected by the sensory change.     

Magnetic resonance imagination of the peroneus longus tendon after anterior cruciate ligament reconstruction

Several studies report that tendons can regenerate after harvesting. These studies have been performed especially in patellar and hamstring tendons. At our institution, 10 cm length of full thickness peroneus longus tendon has been harvested to reconstruct torn anterior cruciate ligament since 1997 as a different graft source. The aim of this study was to investigate whether the peroneus longus tendon used the anterior cruciate ligament reconstruction has a regeneration potential or not. Twelve patients, who had originally undergone harvesting of the peroneus longus tendon for the primary surgery of the anterior cruciate ligament reconstruction, underwent magnetic resonance imaging (MRI). Images of both legs were acquired simultaneously with the use of the scanner’s extremity coil, as we aimed to compare harvested peroneus longus tendon with the other leg’s peroneus longus tendon (healthy side) for evaluation of the regeneration potential. The average age of the patients was 31 years. There were eight right and four left legs. The average time interval was 52 months between ligament surgery and MRI. In all patients, a varying amount of the regeneration of the peroneus longus tendon was seen on the MRI images. Although the extent of PLT regeneration in proximal sections seemed better than in mid- and distal sections, there was no statistical difference between sections (P = 0.130). These data show that the peroneus longus tendon has a regeneration potential after harvesting for anterior cruciate ligament reconstruction.     

Hamstring tendons regeneration after ACL reconstruction: an overview

Despite the long lasting research the ideal method of reconstructing the ACL has not been found so far. The last year’s attention has shifted to the use of the multistrand hamstring tendon grafts. High ultimate tensile load, multiple-bundle replacement that better approximates the anatomy of the normal ACL and low donor site morbidity are the main advantages of this ACL replacement graft. These theoretical advantages have been multiplied when surprisingly studies have shown that semitendinosus and grascillis tendons actually regenerate after harvesting for use as ACL autografts. In this review article we summarize the current knowledge concerning the hamstring regeneration and we focus on issues that have clinical relevance or issues that have not been answered so far.     

Randomized prospective study of ACL reconstruction with interference screw fixation in patellar tendon autografts versus femoral metal plate suspension and tibial post fixation in hamstring tendon autografts: 5-year clinical and radiological follow-up results

Patellar tendon graft has been the most frequently used material in anterior cruciate ligament (ACL) reconstruction, but the hamstring tendons have been increasingly used as well; however, which graft is to be preferred is not adequately supported by existing clinical studies. In this prospective randomized clinical trial, the study hypothesis was that the hamstring tendons are equally good graft material as the patellar tendon in ACL reconstruction. Ninety-nine patients with laxity due to a torn ACL underwent arthroscopically assisted reconstruction with graft randomization according to their birth year to either patellar tendon with metal interference screw fixation or double looped semitendinosus and gracilis tendons with fixation similar to the Endobutton technique using a titanium metal plate suspension proximally and screw-washer postdistally. Excluding preoperative Lysholm knee score, there were no significant differences between the two groups in the preoperative and operative data. A standard rehabilitation regimen was used for all the patients, including immediate postoperative mobilization without a knee brace, protected weight bearing for 2 weeks, and return to full activity at 6–12 months postoperatively. Forty patients in the patellar tendon group and 39 patients in the hamstring tendon group were available for clinical evaluation at median 5 years after surgery (ranges 3 years 11 months–6 years 7 months). The results revealed no statistically significant differences with respect to clinical and instrumented laxity testing, isokinetic muscle torque measurements, International Knee Documentation Committee ratings, Lysholm (knee score), Tegner (activity level) and Kujala patellofemoral knee scores. There was an enlargement of the drill tunnels, statistically more in the hamstring tendon group, but no increase from 2 to 5 years in either group. Narrowing of the joint spaces (IKDC measurement method) from 2 to 5 years postoperatively was seen in both the groups, however, without difference between the two groups.     

Three-dimensional computed tomography imaging evidence of regeneration of the semitendinosus tendon harvested for anterior cruciate ligament reconstruction: a comparison with hamstring muscle strength

OBJECTIVE: The purpose of this study was to evaluate the regeneration of semitendinosus tendons harvested for anterior cruciate ligament (ACL) reconstruction using 3-dimensional (3D) computed tomography (CT) imaging and to compare the degree of regeneration with hamstring strength. METHODS: Twenty-nine patients who underwent ACL reconstruction using ipsilateral autogenous semitendinosus tendons were examined before surgery and 6 and 12 months after surgery by 3D CT imaging. The types of regenerated tendons and the proximal shift of the muscle-tendon junction were evaluated. RESULTS: The types of regenerated semitendinosus tendons varied from case to case. There was a positive correlation between the peak torque ratio of the hamstring muscle strength and the proximal shift of the muscle-tendon junction 6 months after surgery. The proximal shift did not affect the peak torque ratio 12 months after surgery, however. CONCLUSIONS: A proximal shift of the muscle-tendon junction may help to explain the individual differences in early postoperative hamstring muscle strength recovery.     

同种异体胫前肌腱和自体腘绳肌腱重建前交叉韧带临床研究

目的:探讨关节镜下同种异体胫前肌腱与自体腘绳肌腱重建前交叉韧带(ACL)的临床疗效。方法:回顾了60例陈旧性前交叉韧带损伤重建病例,分为A组30例,B组30例。分别应用同种异体胫前肌腱(A组)和自体半腱肌、股薄肌腱(B组)重建ACL,A组平均随访29.4个月,B组平均随访31.6月。采用Lysholm、Tegner、IKDC、KT2000对患者进行术前和术后膝关节功能测试、评分,并用等速测试仪测量各组术后伸膝、屈膝、内旋和外旋肌力。结果:两组手术前后Lysholm、TegnerI、KDC、KT2000测试结果均有显著性差异(P<0.01);但两组间术后评分无显著性差异(P>0.05)。等速肌力测试结果显示术后B组内旋、屈膝肌力较术前下降(P<0.05),而A组术后肌力较术前无明显下降(P>0.05)。结论:关节镜下采用同种异体胫前肌腱重建前交叉韧带疗效满意,不良反应发生率低。     

Changes of SM muscles after STG harvest

Semimembranosus (SM) muscle as well as Semitendinosus-Gracilis (STG) tendon have the same role in knee flexion and tibial internal rotation. Because STG tendons are generally used for anterior cruciate ligament (ACL) reconstruction, some compensational changes in SM muscle might have been induced. The purpose of this study was to investigate the changes of SM muscle affected by harvesting STG tendons. 10 Wistar-strain male rats were divided into control (C) and STG-dissected (STG) groups. Left STG tendons including the distal half of muscle portions were dissected in group STG and only skin incision was performed in group C. 4 weeks after the treatments, fiber types classification and ultrastructural observations were performed. In group STG the decrease of type IIa (fast-twitch fiber with high oxidative capacity) was observed in deep layers of SM muscle (p<0.01). In ultrastructural observations, the increase in lipid droplets and mitochondria and the irregularity of Z disc were observed in deep layers. These morphological changes indicated that the mechanical loading might increase in SM muscle after harvesting of STG. Because of minor injuries in SM muscle, hamstring strength exercise at early stage of rehabilitation program should be carefully performed following ACL reconstruction using STG tendons in clinical practice.     

LARS人工韧带与自体腘绳肌腱重建前交叉韧带早期临床疗效比较

目的:前瞻性对照研究LARS人工韧带与四股自体腘绳肌腱(ST/G)重建前交叉韧带(ACL)手术的早期临床疗效。方法:自2004年8月至2005年6月,前瞻性选择了42例前交叉韧带损伤病例,根据LARS人工韧带使用指征、医生建议和患者意愿,分别选择自体腘绳肌腱或LARS人工韧带作为移植物。其中LARS韧带重建ACL病例23例,两端以挤压螺钉固定;四股自体腘绳肌腱重建ACL病例19例,股骨端Endobutton悬吊固定,胫骨端Intrafix挤压螺钉和Spiked-washer拴桩双重固定。均在术前及术后3个月、6个月、9个月和15个月进行Lysholm、TegnerI、KDC评分。结果:采用LARS人工韧带的病例,在术后9个月的随访期内,三种膝关节功能评分值均显著高于自体腘绳肌腱ACL重建的病例(P<0.05)。结论:应用LARS人工韧带重建ACL较使用自体腘绳肌腱重建术后膝关节功能恢复更快。     

ACL reconstruction: patellar tendon versus hamstring grafts—economical aspects

The aim of the present investigation was to compare the costs for the use of patellar tendon versus hamstring tendons as grafts for anterior cruciate ligament (ACL) reconstruction including the different fixation methods. The background is that during recent years there has been a dramatic shift from patellar tendon to hamstring tendons in ACL reconstructions in Sweden. All our patients with ACL reconstructions performed during 1 year (2004) were included. Knee joints numbering 440 in 439 patients were primary ACL reconstructions. A hamstring graft was used in 345 knee joints (78.4%) and a patellar tendon graft in 95 (21.6%) of the patients (Table 2). On average 34 (SD 12.9; range 14–63) ACL reconstructions per surgeon were performed by a total of 14 surgeons. The average cost for patellar tendon procedure was 197 € compared to 436 € for the hamstring procedure. Mean time for surgery in primary reconstructions was 11.5 min shorter (P<0.001) for patellar tendon reconstructions (71.3±31 min) compared to hamstring reconstructions (83.2±27 min). This means a difference in cost of 90 €. The total additional cost (fixation and surgery time) for the hamstring method compared to the patellar tendon method was on an average 329 €. From a strict economic point of view we therefore recommend or at least consider the use of the patellar tendon as a graft in ACL reconstructions.     

Stress fractures of the femur after ACL reconstruction with transfemoral fixation

The ACL reconstruction with hamstring tendons has become increasingly popular, in part because it is assumed that the complication rate associated with the technique and their severity are lower than with patellar tendon. Two cases of stress reaction of the medial supracondylar area of the femur after ACL reconstruction with hamstring tendons using BioTransfix (Arthrex, Naples, FL, USA) devices for fixation within femur are presented. Both patients were professional athletes (one soccer and one basketball player), and it is hypothesized that the accelerated rehabilitation program used might have represented a risk factor for stress fractures when associated with the guide pin exit hole in the medial femoral cortex. To our knowledge, no such cases have been published to date, but it is important to consider this possibility if an unexplained pain arises in the rehabilitation process of an ACL reconstruction using transfemoral fixation.     

Knee extension and flexion muscle power after anterior cruciate ligament reconstruction with patellar tendon graft or hamstring tendons graft: a cross-sectional comparison 3 years post surgery

Hamstring muscles play a major role in knee-joint stabilization after anterior cruciate ligament (ACL) injury. Weakness of the knee extensors after ACL reconstruction with patellar tendon (PT) graft, and in the knee flexors after reconstruction with hamstring tendons (HT) graft has been observed up to 2 years post surgery, but not later. In these studies, isokinetic muscle torque was used. However, muscle power has been suggested to be a more sensitive and sport-specific measures of strength. The aim was to study quadriceps and hamstring muscle power in patients with ACL injury treated with surgical reconstruction with PT or HT grafts at a mean of 3 years after surgery. Twenty subjects with PT and 16 subjects with HT grafts (mean age at follow up 30 years, range 20–39, 25% women), who were all included in a prospective study and followed the same goal-based rehabilitation protocol for at least 4 months, were assessed with reliable, valid, and responsive tests of quadriceps and hamstring muscle power at 3 years (SD 0.9, range 2–5) after surgery. The mean difference between legs (injured minus uninjured), the hamstring to quadriceps (H:Q, hamstring divided by quadriceps) ratio, and the limb symmetry index (LSI, injured leg divided by uninjured and multiplied by 100) value, were used for comparisons between the groups (analysis of variance). The mean difference between the injured and uninjured legs was greater in the HT than in the PT group for knee flexion power (–21.3 vs. 7.7 W, p = 0.001). Patients with HT graft had lower H:Q ratio in the injured leg than the patients with PT graft (0.63 vs. 0.77, p = 0.012). They also had lower LSI for knee flexion power than those in the PT group (88 vs. 106%, p < 0.001). No differences were found between the groups for knee extension power. The lower hamstring muscle power, and the lower hamstring to quadriceps ratio in the HT graft group than in the PT graft group 3 years (range 2–5) after ACL reconstruction, reflect imbalance of knee muscles after reconstruction with HT graft that may have a negative effect on dynamic knee-joint stabilization.     

Isokinetic quadriceps and hamstring muscle strength and knee function 5 years after anterior cruciate ligament reconstruction: comparison between bone-patellar tendon-bone and hamstring tendon autografts

Existing clinical studies have not proven which graft is to be preferred in anterior cruciate ligament (ACL) reconstruction. In recent years, bone-patellar tendon-bone and hamstring tendons have been the most frequently used graft types. Muscle strength deficit is one of the consequences after ACL reconstruction. The aim of this study was to evaluate possible differences in hamstring and quadriceps muscle strength and knee function 5 years after ACL reconstruction between the BPTB and the STG groups. The study group consisted of 288 patients (132 women, 156 men) with a unilateral ACL rupture who had received a BPTB (175 patients) or STG (113 patients) ACL reconstruction. Lower extremity concentric isokinetic peak extension and flexion torques were assessed at the angular velocities of 60°/s and 180°/s. The International Knee Documentation Committee (IKDC), the Tegner activity level, the Lysholm knee and the Kujala patellofemoral scores were also collected. Isokinetic quadriceps peak torque (percentage of the contralateral side) was 3.9% higher in the STG group than in the BPTB group at the velocity of 60°/s and 3.2% higher at the velocity of 180°/s and the isokinetic hamstring peak torque 2% higher in the BPTB group than in the STG group at the velocity of 60°/s and 2.5% higher at the velocity of 180°/s. In both groups the subjects had weaker quadriceps and hamstring muscle strength in the injured extremity compared with the uninjured one. In the single-leg hop test (according to the IKDC recommendations) there was a statistically significant difference (P = 0.040) between the groups. In the STG group, 68% of the patients had the single-leg hop ratio (injured vs. uninjured extremity) ≥90%, 31% of the patients 75–89% and 1% of the patients <75%, while in the BPTB group the corresponding percentages were 72, 21 and 7%. However, no statistically significant differences in clinical outcome were found between the groups as determined by the IKDC, Tegner activity level, Lysholm knee and Kujala patellofemoral scores.     

Semitendinosus regrowth: biochemical, ultrastructural, and physiological characterization of the regenerate tendon

BACKGROUND: Previous studies have suggested that hamstring tendons can regenerate following harvesting for anterior cruciate ligament reconstruction. HYPOTHESIS: This "neo-tendon" is a true, functional tendon, not scar tissue. STUDY DESIGN: Controlled laboratory study. METHODS: Semitendinosus tendons were harvested from 35 New Zealand white rabbits using a standard tendon stripper. The rabbits were sacrificed 9 to 12 months following the index procedure and thoroughly evaluated. RESULTS: Thirty-one rabbits were available at the time of sacrifice. The neo-tendon was present in 26 rabbits but was highly variable in size and location of its tibial insertion. Histologic and immunohistochemical staining confirmed that the regenerate tissue was indeed tendon with normal cellularity, organization, and immunolocalization of type I collagen. Electron microscopy showed regeneration of organized collagen tissue that simulated native tendon but with a smaller cross-sectional diameter. Functionally, the neo-tendon was able to transmit force across the musculotendinous junction but at a significantly slower rate than the opposite, control leg. Biomechanical properties of the neo-tendon were significantly less than the control side. Biochemical analysis revealed that the neo-tendons contained glycosaminoglycans and collagen, but levels were significantly lower than normal tendons. CONCLUSIONS: Semitendinosus tendons regenerate with biologically reactive tendinous tissues in an animal model. This tissue has many of the characteristics of a normal tendon but appears to be inferior to the original musculotendinous unit at 9- to 12-month evaluation. Further characterization of the "lizard tail phenomenon" is still needed. CLINICAL RELEVANCE: Hamstring tendon regrowth may have a dramatic impact on postoperative function of patients who undergo anterior cruciate ligament reconstruction with these tendons. Further modulation of this regeneration may further reduce graft harvesting morbidity.     

Intra-operative four-stranded hamstring tendon graft diameter evaluation

Purpose  

To evaluate whether clinical factors enable prediction of the diameter of hamstring tendons harvested for anterior cruciate ligament (ACL) reconstruction.     

Arthroscopic anterior cruciate ligament reconstruction with periosteum-enveloping hamstring tendon graft

Tendon–bone incorporation of a tendon graft within the bone tunnel is of priority concern when using for anterior cruciate ligament (ACL) reconstruction. Superior healing process and stronger healing strength can be achieved when periosteum is sutured on the tendon inserted into a bone tunnel. We applied this idea to ACL reconstruction for enhancing tendon graft–bone tunnel healing. This is a prospective clinical outcome study with this surgical technique at minimal 2 years follow-up. Periosteum-enveloping hamstring tendon graft has been used in 68 patients. Data from 62 patients who had been followed up completely were analyzed. All patients suffered from a grade 3 or higher grade of Lachman and anterior drawer test with a positive pivot-shift test. Clinical assessments included the Lysholm knee scores, International Knee Documentation Committee (IKDC) scores, KT-1000 instrumented testing, thigh muscle assessment, and radiographic evaluation. The median Lysholm knee score was 59 (40–70) and 94 (60–100) points (P<0.01) before and after surgery. After reconstruction, 81% of patients were able to return to moderate or strenuous activity. Four (6%) patients were found to exhibit grade 2 or more ligament laxity. Complete range of motion could be achieved in 86% of patients. Three patients (5%) had positive pivot shift. Finally, 92% of patients were assessed as normal or nearly normal rating by IKDC guideline. Bone tunnels enlargement of more than 1 mm was identified in 5% of femoral tunnels and 6% of tibial tunnels. The study shows that a satisfactory result can be achieved with the periosteum-enveloping hamstring tendon graft in ACL reconstruction. Periosteum can be easily harvested at the proximal tibia from a routine incision for hamstring tendon harvesting. Besides the potential for improving tendon–bone healing, enveloped periosteum may help to seal the intra-articular tunnel opening in the early postoperative period, and thus avoid synovial fluid reflux into the tunnel. Bone tunnel enlargement could be reduced.     

Strain within the anterior cruciate ligament during hamstring and quadriceps activity

The objectives of this study were to measure strain in the ACL during simulated: hamstring activity alone, quadriceps activity alone, and simultaneous quadriceps and hamstring activity. Seven knee specimens removed from cadavers were studied. Heavy sutures applied to load cells were attached to the hamstring and quadriceps tendons. Loads were then applied manually (hamstrings) and/or with an Instron testing machine (quadriceps) to simulate isometric contractions of the various muscle groups. Strain was measured using a Hall effect transducer. Acting alone, the isometric hamstring activity decreased ACL strain relative to the passive normal strain at all positions tested. Thus, hamstring exercises are not detrimental to ACL repairs or reconstruction and can be included early in the rehabilitation program after ACL surgery. Acting alone, at flexion angles of 0 degree to 45 degrees, the quadriceps significantly increased the strain within the ACL relative to the passive normal strain. Strain in the ACL during simultaneous hamstring and quadriceps activity was significantly higher than that during passive normal motion from full extension to 30 degrees of flexion. The hamstrings are not capable of masking the potentially harmful effects of simultaneous quadriceps contraction on freshly repaired or reconstructed ACLs unless the knee flexion angle exceeds 30 degrees.     

Femoral tunnel enlargement after anatomic ACL reconstruction: a biological problem?

Tunnel enlargement after anterior cruciate ligament (ACL) reconstruction may compromise revision surgery. The cause of this tunnel enlargement is not yet fully understood, but it is thought to be multifactorial, with biomechanical and biological factors playing a role. Tunnel enlargement has been described particularly in patients who underwent ACL reconstruction with hamstring tendons with extracortical fixation devices. The purpose of our study was to evaluate prospectively with magnetic resonance imaging (MRI) the changes in femoral tunnel diameter following arthroscopic anatomic ACL reconstruction with hamstring tendons. At 3-month post-op, all tunnels had enlarged compared to the diameter of the drill and most tunnels enlarged more in the midsection than at the aperture. In the posterolateral tunnels, the entrance increased 16% in diameter and the middle of the tunnel increased 30% in diameter. In the anteromedial femoral tunnels, the tunnels enlarged 14% at the aperture and 35% in the midsection. All femoral tunnels enlarged and most of them enlarged in a fusiform manner. The biological factors explain better our findings than the mechanical theory, although mechanical factors may play a role and the cortical bone at the entrance of the tunnel may modify the way tunnels respond to mechanical stress.     

The mid- to long-term results of the anterior cruciate ligament reconstruction with hamstring tendons using Transfix technique

In this study, mid to long-term results of anterior cruciate ligament reconstruction with hamstring tendons and Transfix technique were evaluated. Anterior cruciate ligament (ACL) reconstruction with four-strand hamstring tendon was performed with Transfix technique on 271 (198 males, 73 females; mean age 25.7; 17–52) patients with anterior cruciate ligament ruptures. The patients were followed up with clinical examination, Lysholm and Tegner activity scales, IKDC scoring system, KT-1000 test and radiological examination. The mean follow-up period was 82 (48–100) months; 204 (75%) patients had no subjective complaints. According to the KT-1000 test, only 14 (5%) patients had more than 5 mm laxity postoperatively, whereas, 161 (59%) patients had more than 5 mm laxity preoperatively. In addition to this, only 19 (7%) patients had Lysholm scores less than 80 postoperatively, whereas 154 (57%) patients scored less than 80 preoperatively. When compared with Tegner activity scale, 189 (70%) patients scored <6 preoperatively and only 24 (8%) postoperatively; 78 (29%) patients scored D preoperatively and only 5 (2%) patients scored D postoperatively on the basis of the IKDC scoring system. Our functional results were found to be satisfactory in more than 90% of patients. Commonly seen problems in ACL reconstruction such as inaccurate graft placement and tunnel widening were found to be consistent with the values in relevant literature. However, we demonstrated that the functional results and the stability of the knee were not related with tunnel widening. This study concludes that the reconstruction of ACL with hamstring tendons and the Transfix technique is reasonably successful, safe and causes low morbidity. Furthermore, we believe that proper graft preparation, accurate tunnel placement, notch-plasty, fixation and rehabilitation program are all as important as the choice of graft and fixation material.     

Placement of femoral tunnel between the AM and PL bundles using a transtibial technique in single-bundle ACL reconstruction

Tunnel enlargement after anterior cruciate ligament (ACL) reconstruction may compromise revision surgery. The cause of this tunnel enlargement is not yet fully understood, but it is thought to be multifactorial, with biomechanical and biological factors playing a role. Tunnel enlargement has been described particularly in patients who underwent ACL reconstruction with hamstring tendons with extracortical fixation devices. The purpose of our study was to evaluate prospectively with magnetic resonance imaging (MRI) the changes in femoral tunnel diameter following arthroscopic anatomic ACL reconstruction with hamstring tendons. At 3-month post-op, all tunnels had enlarged compared to the diameter of the drill and most tunnels enlarged more in the midsection than at the aperture. In the posterolateral tunnels, the entrance increased 16% in diameter and the middle of the tunnel increased 30% in diameter. In the anteromedial femoral tunnels, the tunnels enlarged 14% at the aperture and 35% in the midsection. All femoral tunnels enlarged and most of them enlarged in a fusiform manner. The biological factors explain better our findings than the mechanical theory, although mechanical factors may play a role and the cortical bone at the entrance of the tunnel may modify the way tunnels respond to mechanical stress.     

Principles for using hamstring tendons for anterior cruciate ligament reconstruction

The use of autogenous hamstring tendon as a graft source for anterior cruciate ligament (ACL) reconstruction continues to gain in popularity. The low harvest morbidity and excellent biomechanical graft properties coupled with improved fixation of soft tissue grafts are all reasons for excellent clinical outcomes of ACL reconstruction using hamstring tendons. In addition, surgeon awareness of the complications associated with poor tunnel placement and more exacting tunnel placement techniques help prevent roof and posterior cruciate ligament impingement and contribute to the successful outcomes of hamstring ACL constructs.