Tension in a double loop tendon anterior cruciate graft during a simulated open chain knee extension exercise.

Concerns exist regarding the tension developed in a reconstructed anterior cruciate ligament (ACL) during open chain knee extension exercises used to rehabilitate the knee. Therefore, the primary objective was to measure tension in an ACL graft during a simulated open chain knee extension exercise as a function of ankle weight. A secondary objective was to determine whether the graft tension was reduced with relatively high stiffness fixation. The open chain exercise was simulated in seven cadaveric specimens in which the ACL had been reconstructed with double loop tendon grafts. Graft tension was measured at 15 degrees of flexion as the effective ankle weight was increased from 22.5 to 67.5 and then to 112.5 N for three different fixation stiffnesses (25, 125, and 225 N/mm). The initial tension was set to restore the 225 N anterior limit of motion to that of the intact knee at 30 degrees of flexion. Increasing the ankle weight caused the graft tension to increase significantly (p<0.0001), but the increase with the highest ankle weight was only 62 N on average. Increasing the fixation stiffness caused the graft tension to decrease significantly (p<0.0001) because the initial tension decreased by 107 N as the fixation stiffness increased. Because the graft tension with the highest ankle weight was limited to 112 N on average, high stiffness fixation methods, which are also resistant to lengthening in the region of the fixation, may reduce the risk of graft construct lengthening during open chain knee extension exercises.     

The effect of initial graft tension on the biomechanical properties of a healing ACL replacement graft: a study in goats.

While a number of in vitro studies have shown that the tension on an anterior cruciate ligament (ACL) replacement graft at the time of fixation has an affect on joint stability, most in vivo studies have reported little or no long-term difference in outcome. The objectives of this study were to (1) establish a large animal model in which differences in knee stability are present at time-zero after ACL reconstruction with grafts fixed at a low (5 N) and high (35 N) initial tension and to (2) quantitatively determine if these initial effects remain after six weeks of healing and if the tensile properties of an ACL replacement graft are influenced by initial graft tension. Seventeen skeletally mature female Saanan breed goats were used. Using the robotic/UFS testing system, the knee kinematics and in situ forces in the replacement graft in response to an externally applied 67 N anterior-posterior (A-P) tibial load were evaluated at time-zero and after six weeks of healing. Afterward, the femur-ACL graft-tibia complexes (FGTCs) from the six-week group were tested under uniaxial tension so that the stress relaxation and structural properties of the FGTC were obtained.At time-zero, knees fixed with a high initial graft tension could better reproduce the A-P translation of the intact knee in response to the 67 N A-P tibial load. Further, in situ forces in these grafts were also closer to those in the intact ACL under the same external loading condition. After six weeks of healing, the A-P translation of the knee and in situ forces in the replacement grafts became similar for the low and high tension groups, while both were significantly different from controls. Further, the percentage of stress relaxation as well as the stiffness, ultimate load at failure, ultimate elongation at failure, and energy absorbed of the FGTCs for both reconstruction groups were not significantly different from each other, but were significantly different from controls. These results demonstrate that while the high initial graft tension could better replicate the normal knee kinematics at time-zero, these effects may diminish during the early graft healing process.     

Effects of initial graft tension on knee stability after anterior cruciate ligament reconstruction using hamstring tendons: a cadaver study

Purpose: Tension degradation within hamstring grafts and anterior knee laxity were analyzed in a cadaveric anterior cruciate ligament (ACL) reconstruction model undergoing cyclic motion. It was hypothesized that suture fixation of a hamstring graft would lose tension during cycling initially and then stabilize, and that anterior knee laxity would increase as tension was lost. Hamstring grafts fixed under 3 different loads were evaluated to determine how initial graft tension affected knee laxity after cyclic motion. Type of Study: Cadaveric biomechanical analysis. Methods: Eighteen pairs of fresh-frozen hamstring tendons were tested on 2 cadaveric knees undergoing ACL reconstruction. The hamstring pairs were separated equally and randomly into one of 3 tension groups: 68 N (15 lb), 45 N (10 lb), and 23 N (5 lb). The loads were applied to the graft at 30° of flexion, and the grafts were secured to the tibia with a suture and post technique. The knee was then cycled 1,000 times using an Instron machine (Instron, Canton, MA) through a range of motion between 0° to 90°. Constant monitoring and recording of graft tension was performed. A KT-1000 (Medmetrics, San Diego, CA) was performed (1) on the intact knee, (2) after ACL excision, (3) after ACL reconstruction and initial graft fixation, and (4) at the completion of the 1,000 cycles. An analysis of variance test was used to evaluate data. Results: The tension within the grafts after 1,000 cycles decreased to 34.5 N (7.6 lb), 16.8 N (3.7 lb), and 15.4 N (3.4 lb) from the preloads of 68, 45, and 23 N, respectively (P < .05 in all cases). This represented an average decrease of 50.2% of the initial tension after 1,000 cycles. Manual-maximum KT testing of the intact knees was 5.8 ± 0.3 mm, and after ACL excision was 13.2 ± 0.9 mm. KT testing revealed 6.0 ± 0.9 mm, 8.1 ± 1.9 mm, and 8.9 ± 1.1 mm of anterior translation after fixation in the tension groups of 68, 45, and 23 N, respectively. After 1,000 cycles, the translation increased to 7.8 ± 1.0 mm, 10.5 ± 1.9 mm, and 10.3 ± 1.5 mm, respectively. Conclusions: This study showed that initial graft tension decreases with cyclic loading, resulting in increased knee laxity. To restore anterior translation to within 3 mm of the native ACL condition after cyclic loading, approximately 68 N of initial tension is required using this fixation technique.     

Peroneus longus tendon graft for anterior cruciate ligament reconstruction: A case report and review of literature

IntroductionThe anterior cruciate ligament (ACL) is one of the most frequently injured structures of the knee joint. Anterior cruciate ligament reconstruction (ACLR) provides surgical restoration of the injured ACL using the placement of graft material. The choice of graft is principal in providing optimal knee stability after surgery. Peroneus longus tendon (PLT) is an autograft modality that offers unique benefits for ACL reconstruction cases.Presentation of caseWe present a case of ACL reconstruction surgery using PLT graft in a patient with a confirmed ACL rupture. Assessment of post-surgical pain, knee stability, and ankle function were performed to determine functional outcome and donor site morbidity. The follow-up results revealed favorable recovery and improvement in all objective parameters.DiscussionPost-operative biomechanical outcomes were evaluated using the International Knee Documentation Committee (IKDC) and the American Orthopedic Foot and Ankle Score (AOFAS) score. The use of PLT in ACL reconstruction established an excellent potential for its satisfactory result and comparable to other graft modalities in widely used evidence-based findings.ConclusionPeroneus longus tendon may be considered the first-option graft in ACL reconstruction as it indicated the absence of significant post-operative morbidity.     

Residual graft tension after graft fixation in anterior cruciate ligament reconstruction: Manual vs tensioning boot techniques

BackgroundGraft fixation at quantitative tension using a manual tensioner was advocated in ACL reconstruction, while the measured tension that is based on the surgeon's hand with the tensioner decreases after graft fixation. Therefore, our purpose is to elucidate how effectively the pre-determined graft tension maintained after final fixation of the graft to the tibia using a tensioning boot system fixed to the calf with a bandage, while monitoring the graft tension based on tibia.MethodsEight cadaveric legs (mean age: 83; 3 males and 5 females) underwent an anatomic double-bundle anterior cruciate ligament (ACL) reconstruction with hamstring tendon grafts. Two tension-adjustable force gauges were installed on the lateral femoral cortex beside the femoral tunnel. Then #5 strong suture wires through the loop end of grafts were tied to the force gauges using Endo-Buttons. After manual maximum load was repeatedly applied to each graft for 3 min, the grafts were fixed to the tibia with 10 N or 20 N at 20 degree of flexion with the following tensioning techniques using double spike plate system: (1) Manually tensioning technique (MT); (2) Tensioning boot technique with flexion-extension motion (TB-FE); and (3) Tensioning boot technique with repetitive pull (TB-RP). The residual tension at 20 was measured 3 min after grafts fixation, and also after 10 and 50 times of repeated flexion-extension motion. One-way repeated measures ANOVA was used for statistical analysis among the three techniques.ResultsThere were significant differences among three techniques fixing grafts with 10/20 N of initial tension in the residual tension 3 min after graft fixation and after 10 and 50 times of repeated flexion-extension motion. Among them, the residual tension in TB-RP was the greatest in most conditions.ConclusionTB-RP is the most secure procedure to maintain the graft tension closer to the intended initial tension in ACL reconstruction.     

Resorbable screws versus pins for optimal transplant fixation (SPOT) in anterior cruciate ligament replacement with autologous hamstring grafts: rationale and design of a randomized, controlled, patient and investigator blinded trial [ISRCTN17384369]

Background

Ruptures of the anterior cruciate ligament (ACL) are common injuries to the knee joint. Arthroscopic ACL replacement by autologous tendon grafts has established itself as a standard of care. Data from both experimental and observational studies suggest that surgical reconstruction does not fully restore knee stability. Persisting anterior laxity may lead to recurrent episodes of giving-way and cartilage damage. This might at least in part depend on the method of graft fixation in the bony tunnels. Whereas resorbable screws are easy to handle, pins may better preserve graft tension. The objective of this study is to determine whether pinning of ACL grafts reduces residual anterior laxity six months after surgery as compared to screw fixation.

Design/ Methods

SPOT is a randomised, controlled, patient and investigator blinded trial conducted at a single academic institution. Eligible patients are scheduled to arthroscopic ACL repair with triple-stranded hamstring grafts, conducted by a single, experienced surgeon. Intraoperatively, subjects willing to engage in this study will be randomised to transplant tethering with either resorbable screws or resorbable pins. No other changes apply to locally established treatment protocols. Patients and clinical investigators will remain blinded to the assigned fixation method until the six-month follow-up examination. The primary outcome is the side-to-side (repaired to healthy knee) difference in anterior translation as measured by the KT-1000 arthrometer at a defined load (89 N) six months after surgery. A sample size of 54 patients will yield a power of 80% to detect a difference of 1.0 mm ± standard deviation 1.2 mm at a two-sided alpha of 5% with a t-test for independent samples. Secondary outcomes (generic and disease-specific measures of quality of life, magnetic resonance imaging morphology of transplants and devices) will be handled in an exploratory fashion.

Conclusion

SPOT aims at showing a reduction in anterior knee laxity after fixing ACL grafts by pins compared to screws.     

Small Size Autograft versus Large Size Allograft in Anterior Cruciate Ligament Reconstruction

BackgroundA small autograft diameter negatively affects functional outcomes, knee stability, and the risk of rerupture after anterior cruciate ligament (ACL) reconstruction, whereas the strength of allograft decreases over time. Therefore, it is not clear whether the use of smaller autografts or the use of larger allografts in ACL yields better results. The aim of this study was to compare the outcome of smaller autografts and larger allografts for ACL reconstruction.MethodsFifty-one patients who underwent ACL reconstruction with hamstring tendon autografts (size ≤ 8 mm) and 21 patients who underwent ACL reconstruction with allografts (size ≥ 10 mm) were included in our study. All patients underwent the same aggressive early postoperative rehabilitation program. There were no significant differences between the autograft and allograft groups regarding the preoperative patient age, sex, time from injury to surgery, and average follow-up time.ResultsThe mean diameter of the 4-stranded hamstring tendon grafts used as autografts was 7.48 ± 0.33 mm and the mean diameter of the allografts was 10.76 ± 0.67 mm. According to specific tests for the ACL (anterior drawer, Lachman, and pivot shift) and clinical evaluation tests (Lysholm knee scoring scale and International Knee Documentation Committee questionnaire), the final follow-up results were significantly better than the preoperative status in both autograft and allograft ACL reconstruction groups. Therefore, there were no significant differences between the autograft and allograft groups preoperatively and at the final follow-up.ConclusionsThe large size of the graft in ACL reconstruction has been reported to affect results positively. However, in our study, we could not find any significant differences between the smaller size autografts and larger size allografts in terms of inadequacy, rerupture, and final follow-up functional results. Although allografts were significantly larger than autografts, we did not have the positive effect of larger size grafts. Smaller size autografts were as effective as the larger size allografts.     

Transplant selection for primary replacement of the anterior cruciate ligament

Various graft choices have evolved over the past few decades for the primary reconstruction of the anterior cruciate ligament (ACL). Three predominant autologous graft choices exist today: patellar, hamstring, and quadriceps tendons. Clinical studies have as yet failed to demonstrate significant differences in clinical outcome among these grafts, irrespective of their varying fixation techniques. Therefore, other factors such as graft harvest morbidity have become more important when comparing different grafts. These factors can differ substantially between the grafts, depending on the type of patients' activities, the injury pattern, and the associated injuries of the knee joint. A basic knowledge of these factors and the parameters that affect the mechanical and biological behavior of the reconstructed ACL can help to find the appropriate graft choice for each individual patient. Factors such as harvest site morbidity, fixation techniques, osseous integration, and tunnel widening are discussed based on current clinical and basic science studies. Finally, an outlook is given for future alternatives with evolving techniques for tissue-engineered grafts, allografts, or the transplantation of xenogeneic donor tissue.     

Anterior Cruciate Ligament Reconstruction: State of the Art

Abstract The rupture of the Anterior cruciate ligament (ACL) belongs to the most common ligament injuries of the human knee joint. ACL rupture results in an increased anterior translation and internal rotation of the tibia. Untreated knee instability causes a disintegration of the roll and sliding movement and a high incidence of secondary meniscus and chondral damages with consecutive or advanced arthritic changes. For deciding on a conservative or operative therapy, it is necessary to develop a high-risk profile. Elderly, inactive patients without instability symptoms can be treated conservatively; younger, active people and complex ligament injuries should receive an ACL replacement. The goal is to eliminate instability by maintaining the physiological kinematics of the knee. Anterior cruciate ligament may be reconstructed arthroscopically assisted by autologous tendons. Predominantly, hamstring- and bone-patellar-tendon grafts are used. No significant differences in knee laxity, clinically and functionally, were observed between both grafts. Various reconstruction techniques, single- or double-bundle techniques, were described. Successful replacement depends on a correct tunnel placement and reconstruction of the physiological band tension, a sufficient mechanical stability of fixation, an impingement-free range of motion and an adequate rehabilitation. A high degree of patient satisfaction in clinical and functional outcome could be evaluated.     

Anterior cruciate ligament deficiency leads to early instability of scaffold for cartilage regeneration: a controlled laboratory ex-vivo study

Purpose

The affect of anterior cruciate ligament (ACL) integrity on the early postoperative stability of a collagen type-I gel scaffold was investigated. The value of fibrin glue for graft fixation in ACL deficient porcine knees over a simulated early postoperative period was also studied.

Methods

Full-thickness articular cartilage defects (11 × 6 mm) were created on the medial femoral condyle of 80 porcine knees. The ACL was left intact or completely transected in each of 40 knees. Gel plugs were tested in each group: press-fitting only in 20 specimens and press-fitting plus fibrin glue in 20 specimens. Each knee underwent 2,000 cycles in a validated ex-vivo continuous passive motion model.

Results

Press-fit-only fixation grafts in knee specimens with an intact ACL showed significantly superior stability than that in ACL deficient knees (p = 0.01). In ACL deficient knees, grafts fixed with press-fitting plus fibrin glue showed significantly superior stability than those using press-fit only fixation (p = 0.01). Press-fitting plus fibrin glue fixation showed no significant differences in worn surface area between knee specimens with intact and deficient ACL.

Conclusions

ACL deficiency led to early scaffold instability in an ex-vivo porcine knee model. Fibrin glue in ACL deficient knees led to additional graft stability. These findings indicated that cartilage regenerative techniques may give optimum results in ACL intact knees.     

Anterior cruciate ligament reconstruction stability with continuous passive motion. The role of isometric graft placement.

A comparison was made of the stability of isometric versus nonisometric anterior cruciate ligament (ACL) reconstructions when subjected to immediate postoperative continuous passive motion (CPM). Anterior cruciate ligament reconstructions were performed on 13 anatomic specimen knees using bone/patellar tendon/bone grafts. Nine ACL substitutions were considered isometric with maximum graft length changes of less than 1 mm. Four ACL substitutions were nonisometric with graft length changes of 3 mm or greater resulting from tightening in flexion. The specimens were subjected to CPM through 0 degrees-95 degrees knee flexion. Knee stability was remeasured with a knee arthrometer at three and 14 days after beginning CPM. All four nonisometric specimens had failed within three days, with increased anterior laxity of 2-9 mm in both the Lachman (20 degrees) and anterior drawer (90 degrees) positions. All nine isometric reconstructions successfully retained pre-CPM anterior stability within 1 mm after 14 days of CPM. This investigation illustrates the importance of isometric graft placement for ACL reconstruction success. Continuous passive motion does not appear to adversely affect immediate ACL-substitute integrity or fixation if graft placement is isometric (less than 1 mm of graft excursion through 0 degrees-110 degrees of knee motion). Continuous passive motion may cause graft deformation, fixation failure, or both, with resultant loss of knee stability if the graft is not isometrically positioned (greater than 3 mm of graft excursion resulting from tightening in flexion).     

The effects of graft width and graft laxity on the outcome of caprine anterior cruciate ligament reconstruction.

We studied how initial graft size and initial graft laxity affected the biomechanics of anterior cruciate ligament (ACL) reconstruction at six months. Sixteen goats had bilateral reconstructions staged eight weeks apart. Autografts 4 and 7 mm wide were taken from the central patellar tendon (PT). Lax grafts were created by adding 4 mm slack to the graft before fixing. We reconstructed each joint using a combination of width and laxity treatments. Both factors were changed for the contralateral joint and all combinations appeared with equal frequency. At six months we measured the joint extension limit, anterior-posterior (AP) translation, and osteoarthritic changes. The grafts were then tested to failure to determine their mechanical properties. After six months the difference in initial treatments had disappeared: there was no difference in graft cross-section due to the different initial widths and there was no difference in joint AP translation due to the initial graft laxity. We did observe that wide grafts were associated with a block to extension, decreased joint AP translation, and increased articular cartilage damage and osteophyte formation. While AP translation was reduced, it was correlated with decreased extension, possibly indicating an increase in scar tissue formation rather than a more functional graft. Neither graft width nor graft laxity produced differences in any graft mechanical properties. This suggests that the use of larger grafts to prevent increased AP translation has undesirable complications. Ultimately, we conclude that neither of these surgical treatments strongly affects the biomechanical result of caprine ACL reconstruction.     

Editorial Commentary: Tunnel Widening After Anterior Cruciate Ligament Reconstruction May Increase Laxity and Complicate Revision

Tunnel widening (TW) after anterior cruciate ligament (ACL) reconstruction has been a research area of interest in ACL reconstruction. It has been demonstrated that femoral tunnels enlarge anteriorly and distally (ie, the direction where the mechanical traction force of the graft works) rather than concentrically after anatomic double-bundle ACL reconstruction using hamstring autografts. This finding suggests that the wall supporting the graft moves closer to the direction of the pull, leading to increased laxity of the knee joint due to TW. The causes of TW are presumed to be multifactorial, with both biological and mechanical features. Biological factors include osteolytic cytokines that enter the space between the graft and the bone through the synovial fluid. Mechanical factors include longitudinal graft motion by extracortical femoral fixation (known as the bungee effect), transverse graft motion (also called the windshield-wiper effect), improper graft placement, higher initial graft tension, accelerated rehabilitation, and so on. Although TW does not seem to affect short-term clinical outcomes from studies published to date, it is plausible to speculate that the expansion of the bone tunnel (ie, the edge where the graft tendon is fixed) would theoretically increase joint laxity to some extent, and it would be premature to conclude that TW has no effect on clinical outcomes relative to graft–tunnel micromotion. In addition, there is a general consensus that the presence of expanded tunnels often severely complicates revision ACL reconstruction. In ACL reconstruction using the hamstring tendon, it is necessary to take into account the possibility of a shift in the tunnel position when determining the location of the femoral tunnel.     

Tendon healing in a bone tunnel. Part I: Biomechanical results after biodegradable interference fit fixation in a model of anterior cruciate ligament reconstruction in sheep

Purpose: Interference fit fixation of soft-tissue grafts has recently raised strong interest because it allows for anatomic graft fixation that may increase knee stability and graft isometry. Although clinical data show promising results, no data exist on how tendon healing progresses using this fixation. The purpose of the present study was to investigate anterior cruciate ligament (ACL) reconstruction biomechanically using direct tendon-to-bone interference fit fixation with biodegradable interference screws in a sheep model. Type of Study: Animal study. Methods: Thirty-five mature sheep underwent ACL reconstruction with an autologous Achilles tendon split graft. Grafts were directly fixed with poly-(D,L-lactide) interference screws. Animals were euthanized after 6, 9, 12, 24, and 52 weeks and standard biomechanical evaluations were performed. Results: All grafts at time zero failed by pullout from the bone tunnel, whereas grafts at 6 and 9 weeks failed intraligamentously at the screw insertion site. At 24 and 52 weeks, grafts failed by osteocartilaginous avulsion. At 24 weeks, interference screws were macroscopically degraded. At 6 and 9 weeks tensile stress was only 6.8% and 9.6%, respectively, of the graft tissue at time zero. At 52 weeks, tensile stress of the reconstruction equaled 63.8% and 47.3% of the Achilles tendon graft at time zero and the native ACL, respectively. A complete restitution of anterior-posterior drawer displacement was found at 52 weeks compared with the time-zero reconstruction. Conclusions: It was found that over the whole healing period the graft fixation proved not to be the weak link of the reconstruction and that direct interference fit fixation withstands loads without motion restriction in the present animal model. The weak link during the early healing stage was the graft at its tunnel entrance site, leading to a critical decrease in mechanical properties. This finding indicates that interference fit fixation of a soft-tissue graft may additionally alter the mechanical properties of the graft in the early remodeling stage because of a possible tissue compromise at the screw insertion site. Although mechanical properties of the graft tissue had not returned to normal at 1 year compared with those at time zero, knee stability had returned to normal at that time. There was no graft pullout after 24 weeks, indicating that screw degradation does not compromise graft fixation.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 2 (February), 2002: pp 113–123     

Bore canal site in surgical reconstruction of the anterior cruciate ligament. Position--placement errors--anatomic measurement

The goal of surgical reconstruction of the anterior cruciate ligament (ACL) is restoration of its function as closely as possible to a physiological roll-and-glide mechanism. Clinical success means knee joint stability, physiological joint biomechanics, and full range of motion. Anatomical placement of the graft insertion points and anatomical direction of the drilled tunnels are necessary to obtain isometric (anatometric) conditions. Despite technical advances in (arthroscopic) surgery, it is not yet possible to obtain absolute "isometricity" for ACL grafts. However a "physiological" or "relative" isometricity seems to be sufficient for successful clinical results. In 1986 Werner Müller proposed the term "anatometrics" in ACL reconstruction to describe this graft behavior and function. The knee joint is a complex motion system including many active and passive stabilizing elements (ligaments, tendons, muscles) as well as a proprioceptive function of the central column ligaments. Reconstruction of this "system" required the surgeon to have good surgical skills and a well-based knowledge of knee anatomy and function. Wrong placement of insertion points and bone tunnels carry the risk for ensuing graft insufficiency and resultant joint instability. The knee "prefers" a destroyed graft over an overconstrained biomechanical situation! Intraoperative factors for failure may be technical mistakes and intraoperative measuring devices for isometry, which might not guarantee true relations in a ligamentous deficient knee. Therefore, visualization of insertion points (and drilling) under direct arthroscopic view is still preferred over generalized rules and distances as proposed by many commercially available rulers and tapers. Recently, navigation and computer-assisted placement techniques have been developed. The clinical standards of those techniques are still under investigation. At our institution, an arthroscopic approach (visualization, palpation) for ACL reconstruction with a bone-patellar-tendon-bone graft technique is used.     

Clinical application of biomechanic and functional anatomical findings of the knee joint]

In order to study the functional anatomy of the knee joint, careful anatomical dissections were conducted on over 130 fresh-frozen cadaveric knee specimens. We found no evidence to support the two-bundle and three-bundle theories of cruciate ligament fiber patterns. The longest fibers in the anterior cruciate ligaments (ACL) measured 37 mm, and the longest in the posterior cruciate ligament (PCL), 41 mm. Cruciate ligament insertions follow a transition line on tibia and femur. Usually not all the fibers of the cruciate ligaments are taut at the same time. They are progressively recruited according to the biomechanical demands placed on them. Fibre recruitment in the ACL is from knee flexion to extension and in the PCL from extension to flexion. The concept of fiber recruitment was recently evaluated mathematically. As a working hypothesis, the knee joint can be looked upon as a biological realization of the crossed four-bar linkage, even in three dimensions. In vitro measurements have shown that correct graft placement in cruciate reconstructions is critical for knee biomechanics. Incorrect placement of grafts may lead to decreased range of motion and/or increased laxity. Distance changes of 3 mm between femoral origin and tibial insertion of a graft may lead to a 400% increase of graft preload and will thus easily reach published pull-out forces for some of the graft fixation methods (button = 248 N). Precise drill guides and isometers may be helpful in any operative technique (open, arthroscopic). Using the IKDC evaluation form and the KT-1000 arthrometer, our studies on 25 patients demonstrated a direct correlation between intraoperative graft tracking and the clinical outcome 2 years after operation. Biomechanical studies to investigate in vivo strain patterns of the anterior cruciate ligament and in vitro strain patterns of isometrically placed cruciate graft reconstructions showed that they did not reach critical fixation failure or graft rupture loads. The highest values were measured in Lachman and anterior drawer testing. In the 20-kg Lachman test the maximum load was 96 +/- 6 N. This was twice the maximum loads of any of the quadriceps exercises (40-50 N). With an isometrically placed graft, full active range of motion postoperatively and exercises with isolated or combined contractions of quadriceps and hamstring muscles will result in small graft loads. Postoperative immobilization with plaster and/or protection with braces may therefore become obsolete.     

Hamstring tendon autograft better than bone patellartendon bone autograft in ACL reconstruction A cumulative meta-analysis and clinically relevant sensitivity analysis applied to a previously published analysis

Background?Current debate on treatment options for anterior cruciate ligament (ACL) reconstruction complicate the choice between hamstring and bone patellartendon bone autografts. We hypothesized a priori that cumulative meta-analysis (a form of sensitivity analysis) might show that the evidence for reduction of morbidity by hamstring grafts could have been reached at an earlier time. Furthermore, we hypothesized a priori that modern state-of-the-art hamstring graft fixation technique would give similar results regarding stability as bone-patellar tendon-bone autografts.

Methods?We performed a cumulative meta-analysis and sensitivity analysis based on femoral graft fixation techniques to compare hamstring autograft and bonepatellar tendon-bone autografts in ACL reconstruction derived from a previously published meta-analysis.

Results?Cumulatively, that hamstring autograft reduces anterior knee pain had already reached statistical significance in 2001 (relative risk 0.49 (95%CI: 0.32–0.76; p = 0.001, I2 = 0%)). The modern endobutton hamstring graft fixation technique (2 studies) yielded similar stability in the Lachman test as bone-patellar tendon-bone grafts, with a relative risk of 1.1 (95%CI: 0.82–1.5; p = 0.6, I2 = 0%). Exclusion of the endobutton group explains the increased laxity in the hamstring graft group.

Interpretation?Cumulative meta-analysis strengthens the evidence for reduced morbidity using hamstring tendon autograft for anterior cruciate ligament reconstruction. Sensitivity analysis focusing on state-of-the-art hamstring graft fixation techniques further weakens the evidence that bone-patellar tendon-bone autografts provide better stability.     

All-Inside Anterior Cruciate Ligament Reconstruction

Anterior cruciate ligament (ACL) reconstruction is one of the most commonly performed knee operations. An “all-inside” technique creates bone sockets for ACL graft passage, as opposed to more traditional full bone tunnels, and typically incorporates suspensory fixation instead of screw fixation to secure the graft. This technique may be indicated for any ACL reconstruction surgery, where adequate bone stock exists to drill sockets and to use cortical fixation. The technique may be used with all soft tissue, as well as bone plug ACL grafts and autograft hamstring or quadriceps tendon; most allograft tendon options may be performed with an all-inside technique. Advantages include anatomic tunnel/socket placement, decreased postoperative pain and swelling, minimal hardware, appropriate graft tensioning and retensioning, and circumferential graft to bone healing. Tips for successful all-inside surgery include matching graft diameter to socket diameter, drilling appropriate length sockets based on individual graft length, so as not to “bottom out” the graft and confirming cortical button fixation intraoperatively. Potential complications include graft-socket mismatch, full-tunnel reaming, and loss of cortical fixation. Multiple studies have shown the all-inside technique to have similar or superior biomechanical properties and clinical outcomes compared to the more traditional full-tunnel ACL reconstruction techniques.     

Effects of ACL graft placement on in vivo knee function and cartilage thickness distributions

Injuries to the anterior cruciate ligament (ACL) frequently lead to early‐onset osteoarthritis. Despite advancement in surgical techniques, ACL reconstruction has a limited ability to prevent these degenerative changes. While previous studies have investigated knee function after ACL reconstruction, in vivo investigations of the effects of graft placement on in vivo joint function and cartilage health are limited. This review presents a series of studies that used novel imaging and 3D modeling techniques to determine the in vivo placement of the ACL graft on the femur using two different ACL reconstruction techniques. These techniques resulted in two distinct graft placement groups: one where the ACL was placed anatomically near the center of the native ACL footprint and another where the graft was placed anteroproximally on the femur, centered outside the ACL footprint. We quantified the effects of graft placement on graft deformation during in vivo loading and how these variables affected knee motion. Finally, we quantified whether femoral placement of the graft affected cartilage thickness. Our results demonstrate that achieving anatomic graft placement on the femur is critical to restoring native ACL function and normal knee kinematics. Knees with grafts that more closely restored normal ACL function, and thus knee motion, experienced less focal cartilage thinning than did those that experienced abnormal knee motion. These results suggest that achieving anatomic graft placement is a critical factor in restoring normal knee motion and potentially slowing the development of degenerative changes after ACL reconstruction. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1160–1170, 2017.