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Purpose: To observe the femoral anterior cruciate ligament (ACL) insertion macroscopically, histologically, and immunohistologically., Methods: We used 20 embalmed cadaveric knees (mean age, 69.8 ± 5.3 years) for this study. The femoral ACL insertion was observed macroscopically, and areas were measured with digital calipers. The morphology of the ACL insertion was subsequently observed, and the areas were measured histologically and immunohistologically (stained for types I and III collagen). Finally, the macroscopic and microscopic measurements were compared., Results: Macroscopically, in 16 knees, the proximal ACL fibers spread in a fanlike manner on the medial aspect of the lateral femoral condyle and the femoral insertion was oval. The lengths of the long and short axes of the insertion were 17.7 ± 2.7 mm and 4.6 ± 0.7 mm, respectively. Microscopically, the insertion was located just behind the lateral intercondylar ridge (resident's ridge) and could be divided into the direct and indirect insertions. The direct insertion was 5.3 ± 1.1 mm wide and did not continue to the posterior cartilage. The indirect insertion was located behind the direct insertion, and the posterior ACL fiber stained for type I collagen blended into the posterior cartilage on immunohistologic observations. Another bony ridge was found at the posterior margin of the direct insertion. The widths of the direct insertion were similar between microscopic and macroscopic measurements., Conclusions: The femoral ACL insertion observed macroscopically corresponded to the direct insertion observed microscopically. The posterior portion behind the lateral intercondylar posterior ridge was the indirect insertion microscopically and appeared membrane-like macroscopically., Clinical Relevance: Findings from observation of the lateral intercondylar posterior ridge during arthroscopy and consideration of the distance from the posterior cartilage border may contribute to surgeons' decisions about femoral tunnel placement during anatomic ACL reconstruction., (Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The anterior cruciate ligament (ACL) rarely heals spontaneously after rupture. Mesenchymal stem cells (MSCs) contribute to healing in various tissues, therefore, they may also have a key role in healing after ACL rupture. The purpose of this study was to investigate the properties of MSCs in ruptured ACLs., Methods: Human ACL samples were harvested from patients undergoing primary ACL reconstruction, and samples were classified by the number of days post rupture (phase I<21 days; phase II 21–56 days; phase III 57–139 days phase IV≥140 days). We evaluated the characteristics of MSCs, such as colony-forming capacity, differentiation potential and cell-surface markers., Results: There was a tendency for high colony-forming capacity during phases I and II, which tended to decrease in phase III. Chondrogenic, adipogenic and osteogenic differentiation potential was maintained until phase II but decreased in phase III. Most surface-epitope expression was consistent from phase I to III: positive for CD44, CD73, CD90 and CD105; negative for CD11b, CD19, CD34, CD45 and human leukocyte antigen-D-related (HLA-DR). The presence of these surface markers proved the existence of MSCs in ruptured ACL tissue., Conclusions: Our results suggest that colony-forming and differentiation potential decrease over time. It is important to consider changes in properties of MSCs and use ACL tissue in the acute phase of rupture when biological manipulation is required.

Purpose: This study aimed to assess knee laxity before and after resection of the anterior cruciate ligament (ACL) remnants, using a computer navigation system., Methods: This prospective study included 83 knees undergoing primary navigated ACL reconstruction. ACL remnants were classified into 4 morphologic types based on the arthroscopic findings: type 1, bridging between the posterior cruciate ligament and tibia; type 2, bridging between the roof of the intercondylar notch and tibia; type 3, bridging between the lateral wall of the intercondylar notch and tibia; and type 4, no substantial ACL remnants. Anterior tibial translation (ATT) and range of internal-external rotation of tibia (total rotation) at 15°, 30°, 45°, 60°, 75°, and 90° of knee flexion were measured before and after resection of the ACL remnants by use of the additional functions of the navigation system., Results: The different morphologic types of the ACL remnants were as follows: type 1, 12 knees; type 2, 16 knees; type 3, 51 knees; and type 4, 4 knees. There were no significant differences in the mean ATT before and after resection at any knee flexion angle in type 1, 2, or 4 knees. In type 3 knees the mean ATT at 15° of knee flexion before resection significantly increased after resection. There were no significant differences in the mean total rotation before and after resection at any knee flexion angle for each type. After resection of the ACL remnants, 12 knees (14.5%) in the type 3 showed an increased ATT by 3 mm or more., Conclusions: This study suggests that the ACL remnant does not play a major role in stabilization of the knee. Although type 3 ACL remnants significantly decreased anterior knee laxity in the knee extension position, the knee stability provided by the ACL remnants was not adequate., Level of Evidence: Level II, prognostic study., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The objective of this study was to compare knee laxity between anterior cruciate ligament (ACL)-reconstructed knees and contralateral stable knees by use of intraoperative navigation., Methods: Five patients with ipsilateral ACL-deficient knees with contralateral stable knees without any ligament injuries were included in this study. Anteroposterior (AP) knee laxity during anterior drawer force applied manually and range of tibial rotation and AP knee laxity during internal and external rotational torque applied manually in both the ACL-deficient knee and the contralateral stable knee were measured by use of a navigation system from 15 degrees to 90 degrees of knee flexion. After the temporary fixation of the posterolateral bundle, anteromedial bundle (AMB), or double-bundle (DB) reconstruction, knee laxity was measured again and compared with that of the stable knee., Results: The mean laxities for PLB reconstruction were significantly greater than those of the contralateral stable knee at more than 75 degrees of knee flexion (P < .05). The mean laxities for AMB or DB reconstruction were not significantly different from those of the contralateral stable knee at all knee flexion angles. Those for AMB reconstruction were within +1.6 mm and those for DB reconstruction were within -2.0 mm of those of the contralateral stable knee. The mean rotations for all reconstructions were significantly less than those of the contralateral stable knee at less than 30 degrees of knee flexion (P < .05)., Conclusions: DB and AMB reconstructions could restore knee laxity closer to the level of the contralateral stable knee. Because normal knee laxity is different in each individual, evaluation of contralateral stable knee laxity during ACL reconstruction surgery would be helpful for restoration to the level of the specific preinjury knee laxity., Level of Evidence: Level IV, therapeutic case series., (2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Unlabelled: Patellar tendon autografts are not suitable for multibundle ACL reconstruction, a procedure that reportedly enhances postoperative knee stability. Biomechanical studies recommend lateral placement of the femoral tunnel for single-bundle reconstruction to improve postoperative knee kinematics. We asked whether a lateralized single-bundle patellar tendon graft (LSBP) would provide good short-term results of ACL reconstruction comparable to double-bundle hamstring tendon grafts (DBH). We prospectively followed 144 patients with unilateral ACL rupture treated with either LSBP or DBH in a nonrandomized fashion. Twenty-four female and 31 male patients with LSBP and 44 female and 26 male patients with DBH were followed for a minimum of 24 months (average, 38 months; range, 24-56 months). The patients with LSBP recovered knee extension better at 1 month compared with the patients with DBH, but extension was similar after 3 months. We observed no differences in the side-to-side difference of KT1000 measurement, pivot shift test, or anterior drawer test between LSBP and DBH. Although better recovery of hamstring strength in LSBP and better recovery of quadriceps strength in DBH were observed in the early postoperative period, these differences disappeared after 12 months. There was no difference in International Knee Documentation Committee objective evaluation between LSBP and DBH at the final followup., Level of Evidence: Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Background: Recently, more anatomic anterior cruciate ligament reconstructions have been developed to improve knee laxity., Purpose: The objective of this study is to assess knee kinematics after double-bundle reconstruction with hamstring tendon and after anatomically oriented reconstruction with a patellar tendon using navigation during surgery., Study Design: Cross-sectional study; Level of evidence, 3., Methods: Eighty knees received double-bundle reconstruction with a hamstring tendon graft, and 45 knees received anatomically oriented reconstruction with a patellar tendon graft. Before reconstruction, knee laxity was measured using a navigation system. After the posterolateral bundle or anteromedial bundle was temporarily fixed during double-bundle reconstruction, knee laxity was measured to assess the function of each bundle. After double-bundle reconstruction or anatomically oriented reconstruction with patellar tendon, knee laxity was measured in the same manner., Results: Both double-bundle reconstruction and anatomically oriented reconstruction similarly improved knee laxity compared with before reconstruction in all knee flexion angles. Regarding the function of the anteromedial and posterolateral bundles in double-bundle reconstruction, the 2 grafts showed contrasting behavior. The posterolateral bundle restrained tibial displacement mainly in knee extension, whereas the anteromedial bundle restrained it more in the knee flexion position. The posterolateral bundle has a more important role in controlling rotation of the tibia than the anteromedial bundle., Conclusion: Although the posterolateral bundle has an important role in the extension position, the anteromedial bundle is more important in the flexion position. Therefore, both bundles should be reconstructed to improve knee laxity throughout knee range of motion. Even with single-bundle reconstruction using a patellar tendon, anatomic reconstruction might improve knee laxity similar to double-bundle reconstruction.

Recently, anatomic double-bundle anterior cruciate ligament (ACL) reconstructions, which reproduce the anteromedial and posterolateral bundles, have been developed to improve knee laxity. However, there are little data on the in vivo biomechanics after such reconstructions. In this paper, we will review biomechanical and clinical studies that have compared single-bundle and double-bundle reconstruction, and introduce our intraoperative evaluation of double-bundle reconstruction using a navigation system. In the navigation evaluation, knee kinematics before and after ACL reconstruction were assessed, and functions of the anteromedial and posterolateral bundles were evaluated. Although the posterolateral bundle has an important role in the knee extension position, the anteromedial bundle improved knee laxity during the more knee flexion positions. Furthermore, double-bundle reconstruction improved knee laxity compared with either posterolateral or anteromedial bundle reconstruction throughout knee range of motion. Although traditional single-bundle reconstruction, reproducing the anteromedial bundle, is a reasonable procedure, double-bundle reconstruction has the potential to improve knee stability after ACL reconstruction.

Background: The current trend in anterior cruciate ligament (ACL) reconstruction has shifted to anatomical double-bundle (DB) reconstruction, which reproduces both the anteromedial bundle (AMB) and the posterolateral bundle (PLB) of the ACL. Navigation systems have also been recently introduced to orthopedic surgical procedures, including ACL reconstruction. In DB-ACL reconstruction, the femoral and tibial tunnel positions are very important, but a representation of the ACL footprint under an arthroscopic view has not been established even though navigation systems have been introduced. The purpose of this study was to evaluate the anatomical footprints of both the AMB and the PLB using the representation method for application to arthroscopic DB-ACL reconstruction using a navigation system, and to evaluate the validity of the currently determined footprint position compared with other representation methods., Methods: Thirty-six cadaveric knees were used for an anatomical evaluation of footprints of the AMB and PLB. On the tibial side, the ACL footprints were evaluated using an original method. On the femoral side, the ACL footprints were evaluated using Watanabe's method and three other methods: (1) the quadrant method, (2) Mochizuki's method, and (3) Takahashi's method., Results: The central points of the ACL footprints were represented almost constantly. The present data is in accordance with previous measurement data., Conclusion: This study showed that the anatomical data of the ACL femoral and tibial footprints determined with Watanabe's method at the femoral side and our original method at the tibial side were both applicable to arthroscopic surgery with a navigation system.

The goal of this study was to establish the reliability of a navigation system for femoral tunnel placement in arthroscopic double-bundle anterior cruciate ligament (ACL) reconstruction. Guidewires were inserted to the center of the anteromedial and posterolateral femoral tunnels of eight porcine knees using an image-free navigation system. The relative position of the guidewires in reference to the height and depth of the lateral condyle was determined by the navigation system and a digital camera and compared. The average differences in high-low and deep-shallow position between the two measurement systems were 2.6% +/- 1.3% (range, 0.6%-4.9%) and 1.6% +/- 1.4% (range, 0.1%-4.0%) for the anteromedial tunnels and 2.7% +/- 1.4% (range, 0%-3.9%) and 2.6% +/- 1.3% (range, 1.1%-4.3%) for the posterolateral tunnels. The data suggest that the navigation system provided surgeons with reliable information to determine the femoral tunnel location in arthroscopic double-bundle ACL reconstruction.

Background: The success of anterior cruciate ligament (ACL) reconstruction using tendon grafts depends on biological integration between the tendon and bone. Growth factors play a significant role in this integration process, but few studies have defined the regulating mechanisms of these growth factors during tendon-bone healing. The aim of the present study was to clarify the relationship between the histological changes and the expression of endogenous growth factors at the tendon-bone interface., Methods: Using intra-articular tendon transfer in rabbits to stimulate ACL reconstruction, the presence of fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor (VEGF), bone morphogenetic protein-2 (BMP-2), and BMP-7 at the interface between the tendon and bone was evaluated immunohistochemically. Histological and immunohistochemical investigations were performed at 1, 3, 6, and 12 weeks after surgery., Results: Fibrous integration of the tendon graft to the bone was observed immediately after tendon transfer and followed remodeling of the bone tunnel. Fibroblast and vascular growth factors were found in abundance at the tendon-bone interface in the first 3 weeks of graft incorporation, but were absent in the 12-week specimens. BMPs were found throughout the 12-week study period and were observed at high concentrations near the bone., Conclusions: These results indicate that FGF-2 and VEGF contribute to fibrous integration between the tendon and bone during the early postoperative stage, and that BMP-2 and BMP-7 are specifically involved in bone remodeling leading to osseous integration. The early stages of tendon-bone healing might be important in controlling the integration process of the interface in ACL reconstruction surgery as seen in this rabbit model.

This study compares anatomy and tunnel placement during double-bundle procedures. Double-bundle anterior cruciate ligament (ACL) reconstruction reproduces both the anteromedial and posterolateral bundles. Thirty-six knees from cadavers were used for anatomic study, and 38 navigated double-bundle ACL reconstructions were evaluated for tunnel placements. With the exception of femoral tunnels of anteromedial bundles, all tunnel placements were in accordance with the anatomic measurements of the native ACL. The investigators concluded that incorporating ACL anatomic information into navigation systems would enhance double-bundle procedures.

We report a case of pretibial cyst formation, which is a rare complication, after anterior cruciate ligament (ACL) reconstruction. The patient had undergone ACL reconstruction at age 18 and complained of pain and swelling localized on the anteromedial aspect of the ipsilateral proximal tibia 2 years postoperatively. Magnetic resonance imaging showed a multilocular fluid-filled cyst arising from the outlet of the tibial bone tunnel. Open resection of the cyst was performed and communication between the tibial tunnel and the joint space was confirmed arthroscopically. The cavity of the tibial tunnel was packed with cancellous bone to seal off a water channel. The laboratory examination revealed slightly concentrated chondroitin sulfate in the cyst fluid compared with the articular fluid, despite histologic observation of no glycosaminoglycan synthesis in the cells of the cyst wall. These findings indicated that leakage of the articular fluid via the tibial tunnel might have caused the pretibial cyst after ACL reconstruction.

The purpose of this study was to assess double-bundle anterior cruciate ligament (ACL) reconstruction, which reproduces the anteromedial bundle and posterolateral bundle, using a navigation system. In 32 patients, anteroposterior (AP) displacement and rotation of the tibia were measured before reconstruction and after posterolateral bundle fixation, anteromedial bundle fixation, and double-bundle ACL reconstruction (in posterolateral and anteromedial bundles fixation). The posterolateral bundle has an important role in the extension position, whereas the anteromedial bundle restricts AP displacement from extension to flexion. AP displacement after double-bundle ACL reconstruction was significantly improved compared to AP displacement after posterolateral bundle or anteromedial bundle fixation. Although traditional reconstruction for reproducing the anteromedial bundle is reasonable, double-bundle ACL reconstruction is recommended for improved knee stability.

Purpose: Although several technical developments for arthroscopic treatment of anterior cruciate ligament (ACL) avulsion fracture have been reported, it remains unclear which fixation technique is most effective to obtain the best initial fixation strength. The objectives of this study were to compare the initial fixation strength in response to a cyclic tensile load between different fixation techniques for ACL avulsion fractures., Type of Study: Cadaveric biomechanical evaluation., Methods: Using 15 fresh-frozen cadaveric human knees, 3 different fixation techniques for noncomminuted ACL avulsion fractures were compared by measuring the anterior tibial translation (ATT) under 500 cycles of 0 to 100 N of anterior tibial load: (1) antegrade screw fixation, (2) retrograde screw fixation, and (3) pullout suture fixation., Results: The increase in the ATT after the cyclic loading for the pullout suture fixation (2.2 +/- 0.8 mm) was significantly larger than that for the antegrade screw fixation (1.0 +/- 0.2 mm). The ATT increase in the retrograde fixation group (2.0 +/- 0.6 mm) was not significantly different compared with the other groups., Conclusions: All methods were effective and there was a slight biomechanical advantage to antegrade screw fixation over pullout suture fixation., Clinical Relevance: Antegrade screw fixation is more effective in obtaining initial rigid fixation than pullout suture fixation for ACL avulsion fractures.

Background: Anatomic fixation of the graft in anterior cruciate ligament reconstruction has improved stability of the reconstructed knee joint in experimental studies., Hypothesis: Anatomic fixation of the bone-patellar tendon-bone autograft will reduce tunnel enlargement and improve clinical results., Study Design: Prospective cohort study., Methods: Sixty patients were randomly divided into three groups: a nonanatomic fixation group (traditional single-incision reconstruction), an anatomic fixation group (reconstruction in which a bone plug was grafted into the tibial tunnel), and an anatomic fixation group with all-inside reconstruction. Stability of the knee joint was examined with a KT-1000 arthrometer at 2, 4, 6, 12, and 24 months after surgery. At 12 months, anteroposterior and lateral radiographs were made to assess tunnel enlargement., Results: Although the magnitude of tibial displacement gradually increased after reconstruction in all three groups, the anatomic fixation group had significantly better stability than the groups undergoing nonanatomic fixation or all-inside anatomic fixation at 4 and 6 months after anterior cruciate ligament reconstruction. However, there was no significant difference between the three groups at 24 months. Regarding the tibial tunnel, residual rates and enlargement of tunnels were different between the reconstruction techniques. The nonanatomic reconstruction group had significantly greater tunnel enlargement., Conclusion: Anatomic fixation of the graft decreased the tunnel enlargement but had no effect on knee stability at 2-year follow-up., (Copyright 2003 American Orthopaedic Society for Sports Medicine)

Background: The latest version of the navigation system for anterior cruciate ligament (ACL) reconstruction has the supplementary ability to assess knee stability before and after ACL reconstruction. In this study, we compared navigation data between clinical grades in ACL-deficient knees and also analyzed correlation between clinical grading and navigation data. Methods: 150 ACL deficient knees that received primary ACL reconstruction using an image-free navigation system were included. For clinical evaluation, the Lachman, anterior drawer, and pivot shift tests were performed under general anesthesia and were graded by an examiner. For the assessment of knee stability using the navigation system, manual tests were performed again before ACL reconstruction. Navigation data were recorded as anteroposterior (AP) displacement of the tibia for the Lachman and anterior drawer tests, and both AP displacement and tibial rotation for the pivot shift test. Results: Navigation data of each clinical grade were as follows; Lachman test grade 1+: 10.0 mm, grade 2+: 13.2 ± 3.1 mm, grade 3+: 14.5 ± 3.3 mm, anterior drawer test grade 1+: 6.8 ± 1.4 mm, grade 2+: 7.4 ± 1.8 mm, grade 3+: 9.1 ± 2.3 mm, pivot shift test grade 1+: 3.9 ± 1.8 mm/21.5° ± 7.8°, grade 2+: 4.8 ± 2.1 mm/21.8° ± 7.1°, and grade 3+: 6.0 ± 3.2 mm/21.1° ± 7.1°. There were positive correlations between clinical grading and AP displacement in the Lachman, and anterior drawer tests. Although positive correlations between clinical grading and AP displacement in pivot shift test were found, there were no correlations between clinical grading and tibial rotation in pivot shift test. Conclusions: In response to AP force, the navigation system can provide the surgeon with correct objective data for knee laxity in ACL deficient knees. During the pivot shift test, physicians may grade according to the displacement of the tibia, rather than rotation. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to assess the pivot-shift phenomenon during double-bundle anterior cruciate ligament (ACL) reconstruction using a navigation system. Methods: Ninety patients who received navigated double-bundle ACL reconstruction were included in this study. The mean age of the patients was 21.9 years. During reconstruction, pivot-shift tests were performed 4 times: before reconstruction, after the posterolateral bundle fixation, after the anteromedial bundle fixation, and after the double-bundle reconstruction. Both tibial internal rotation and anterior translation under the pivot-shift test were measured at each phase by the additional functions of the navigation. The navigation system used in this study was the image-free, which does not require preoperative or intraoperative images, OrthoPilot ACL (version 2.0; B. Braun Aesculap, Tuttlingen, Germany). Results: Before ACL reconstruction, average (± standard deviation) tibial internal rotation and anterior translation under the pivot-shift test were 23.7° ± 6.1° and 5.2 ± 2.4 mm. They were significantly decreased to 20.9° ± 6.4° and 2.3 ± 1.1 mm after the posterolateral bundle fixation, and also decreased to 22.2° ± 5.7° and 2.4 ± 1.1 mm after the anteromedial bundle fixation. There was no significant difference between the groups. After double-bundle reconstruction, they improved to 20.3° ± 6.3° and 2.0 ± 1.0 mm. Conclusions: Our results indicate that both the posterolateral and the anteromedial bundle similarly control both anterior translation and internal rotation during pivot-shift testing. Double-bundle reconstruction may further improve knee stability. Level of Evidence: Level II, development of diagnostic criteria on basis of consecutive patients with universally applied reference gold standard. [Copyright &y& Elsevier]

Purpose: Although several technical developments for arthroscopic treatment of anterior cruciate ligament (ACL) avulsion fracture have been reported, it remains unclear which fixation technique is most effective to obtain the best initial fixation strength. The objectives of this study were to compare the initial fixation strength in response to a cyclic tensile load between different fixation techniques for ACL avulsion fractures. Type Of Study: Cadaveric biomechanical evaluation. Methods: Using 15 fresh-frozen cadaveric human knees, 3 different fixation techniques for noncomminuted ACL avulsion fractures were compared by measuring the anterior tibial translation (ATT) under 500 cycles of 0 to 100 N of anterior tibial load: (1) antegrade screw fixation, (2) retrograde screw fixation, and (3) pullout suture fixation. Results: The increase in the ATT after the cyclic loading for the pullout suture fixation (2.2 +/- 0.8 mm) was significantly larger than that for the antegrade screw fixation (1.0 +/- 0.2 mm). The ATT increase in the retrograde fixation group (2.0 +/- 0.6 mm) was not significantly different compared with the other groups. Conclusions: All methods were effective and there was a slight biomechanical advantage to antegrade screw fixation over pullout suture fixation. Clinical Relevance: Antegrade screw fixation is more effective in obtaining initial rigid fixation than pullout suture fixation for ACL avulsion fractures. [ABSTRACT FROM AUTHOR]

It has recently been emphasized that restoration of neuromuscular function contributes to dynamic stability of the anterior cruciate ligament (ACL) reconstructed knee. The existence of an ACL-hamstring reflex arc, one of the protective ligament-muscular pathways, has been revealed in normal human knees. Although reinnervation to the reconstructed ACL has been observed histologically, it remains unclear whether the ACL-hamstring reflex arc is reestablished. This study examined the existence of the ACL-hamstring reflex arc in ACL-reconstructed knees by analyzing the changes in the hamstring EMG elicited by electrical stimulation to the reconstructed ACL. The patellar tendon grafts transplanted as an ACL substitute in three patients were electrically stimulated via a bipolar wire electrode inserted arthroscopically. The surface EMG was monitored from the ipsilateral biceps femoris and semitendinosus. In two of the three patients the significantly increased EMG value of the biceps femoris was detected between 120 and 140 ms after the onset of electrical ACL stimulation. The increased EMG activity detected in the biceps femoris after the stimulation to the patellar tendon graft indicated reestablishment of the ACL-hamstring reflex arc in the ACL-reconstructed knee. [ABSTRACT FROM AUTHOR]

Abstract: We report a case of pretibial cyst formation, which is a rare complication, after anterior cruciate ligament (ACL) reconstruction. The patient had undergone ACL reconstruction at age 18 and complained of pain and swelling localized on the anteromedial aspect of the ipsilateral proximal tibia 2 years postoperatively. Magnetic resonance imaging showed a multilocular fluid-filled cyst arising from the outlet of the tibial bone tunnel. Open resection of the cyst was performed and communication between the tibial tunnel and the joint space was confirmed arthroscopically. The cavity of the tibial tunnel was packed with cancellous bone to seal off a water channel. The laboratory examination revealed slightly concentrated chondroitin sulfate in the cyst fluid compared with the articular fluid, despite histologic observation of no glycosaminoglycan synthesis in the cells of the cyst wall. These findings indicated that leakage of the articular fluid via the tibial tunnel might have caused the pretibial cyst after ACL reconstruction. [Copyright &y& Elsevier]

The article focuses on the use of transtibial technique in reconstructing anatomic rectangular tunnel anterior cruciate ligament (ACL) with bone-patellar tendon-bone (BTB) autograft. Indications and contraindications are mentioned, one is that ACL reconstruction is recommended for athletes and young patients with ACL injury. Processes under the technique are discussed such as patient positioning, graft harvesting and tibial tunnel preparation. Posterior wall blowout is cited as a complication.