Effect of Tunnel Position and Graft Size in Single-Bundle Anterior Cruciate Ligament Reconstruction: An Evaluation of Time-Zero Knee Stability
ABSTRACT To determine whether (1) increased graft size with anatomic anterior cruciate ligament reconstruction (ACLR) would confer proportionally increased time-zero biomechanical stability and (2) larger grafts would compensate for the inferior time-zero biomechanical kinematics of nonanatomic, single-bundle ACLR.
Ten cadaveric knees were allocated for single-bundle ACLR in an anatomic, center-center or nonanatomic, posterolateral-to-anteromedial footprint position with hamstring autograft. Medial arthrotomy defined the native anterior cruciate ligament (ACL) tibial and femoral footprints. ACLR was performed with a 6-mm semitendinosus graft in 6-mm tunnels and repeated with a 9-mm semitendinosus and gracilis graft in 9-mm tunnels for each knee. Lachman and instrumented pivot-shift examinations assessed knee stability in the ACL-intact, ACL-deficient, and ACLR conditions. Medial and lateral meniscectomies after ACL transection created reproducible pivot shifts. Significance was defined as P < .05.
ACLR in the center-center or posterolateral-to-anteromedial position significantly reduced anterior tibial translation compared with the ACL- and meniscus-deficient conditions (P < .001). Larger graft size, however, did not significantly improve time-zero biomechanical stability compared with a smaller graft in the same position for either reconstruction (P = .41 to .74). A center-center ACLR controlled tibial translation significantly better than a nonanatomic graft position regardless of graft size (P < .001). A smaller graft in the anatomic position controlled tibial translation significantly better than a larger graft in a nonanatomic position (P < .001).
This study showed that increasing graft size did not improve the time-zero biomechanical stability of the knee after ACLR. Increased graft size did not compensate for the biomechanical instability documented with the nonanatomic tunnel position. Restoration of native footprint anatomy in ACLR is of paramount importance regardless of graft size and source.
A larger graft size does not ameliorate the inferior time-zero biomechanics associated with nonanatomic tunnel preparation during single-bundle ACLR.
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ABSTRACT: BACKGROUND: The aim of modern techniques for anatomic reconstruction of the ACL is to reproduce ACL footprints, in order to restore anatomy and therefore normal biomechanics. Is there an oversizing of the hamstring grafts related to ACL dimensions? METHODS: Twenty-two paired cadaver knees were dissected. ACL dimensions at mid-portion and ACL footprints were measured after removing the synovial membrane. Hamstrings were harvested and prepared in a quadruple strand graft in order to measure the mean circumference. RESULTS: The average ACL tibial and femoral insertion site areas of the ACL were 117.9mm(2) (range, 90 to 130mm) and 96.8mm(2) (range, 80 to 121mm), respectively. The average diameter and cross sectional area of the ACL tendon at mid-portion were 6.1mm (range, 5 to 7mm) and 29.2mm(2) (range, 20 to 38.9), respectively. The average diameter and cross-sectional area of the 4-stranded hamstring tendons were 6.7 (range, 5 to 8) and 35.3mm(2) (range, 20 to 50), respectively. There was a correlation between the 4-stranded hamstring grafts and ACL dimensions (footprints, ligament at mid substance, p<0.01). The cross sectional area of hamstring tendon was significantly larger than the ACL area at mid-portion (mean 20.9%, p<0.05). CONCLUSION: With current ACL reconstruction techniques, the graft is oversized at a mean of 21%, despite a good correlation between the ACL and the hamstring tendon, especially among small subjects and women. The question arises whether the anatomic reconstruction of the ACL should fill ACL footprints or mimic the ligament itself. CLINICAL RELEVANCE: Hamstrings grafts are significantly larger than native ACL.The Knee 11/2012; DOI:10.1016/j.knee.2012.10.006 · 1.70 Impact Factor
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ABSTRACT: The aims of this study were (1) to evaluate the femoral tunnel position after anatomic double-bundle and nonanatomic single-bundle reconstruction; (2) to evaluate the influence of rotation of the femur caused by limb malalignment on measurements of the position of the femoral ACL tunnel aperture relative to Blumensaat's line. 3D CT scans were performed in 5 patients after anatomic double-bundle reconstruction and 5 patients after nonanatomic single-bundle reconstruction. Digitally reconstructed lateral radiographs were generated from the 3D CT scans to determine the tunnel position on the femur along and perpendicular to Blumensaat's line. The femur was then rotated to simulate internal/external and varus/valgus rotations from 0° to 15° in 5° increments. At each rotated bone position, tunnel position relative to Blumensaat's line was calculated and the difference from the lateral radiograph was calculated. After double-bundle reconstruction, the AM tunnel was located at 31.5 (±5.0) % along Blumensaat's line and 29.7 (±13.6) % perpendicular to Blumensaat's line, and the PL tunnel at 36.2 (±12.9) % along Blumensaat's line and 34.2 (±7.6) % perpendicular to Blumensaat's line. Valgus greater than 10° significantly affected the assessment of tunnel position (P = 0.043). After nonanatomic single-bundle reconstruction, the tunnel position was 35.4 (±15.0) % along Blumensaat's line and -2.7 (±19.4) % perpendicular to Blumensaat's line. Internal rotation of more than 10° significantly affected the assessment of tunnel position (P = 0.043). Tunnel position after anatomic double-bundle reconstruction and nonanatomic single-bundle reconstruction can be determined on lateral radiographs. However, valgus and internal rotation of more than 10° can introduce significant errors in tunnel position estimates. Case series, Level IV.Knee Surgery Sports Traumatology Arthroscopy 10/2011; 20(5):979-85. DOI:10.1007/s00167-011-1683-x · 2.84 Impact Factor
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ABSTRACT: The aim of this study was to predict the hamstring graft sizes prior to anterior cruciate ligament reconstruction surgery in adults by using preoperative magnetic resonance imaging (MRI). Fifty-one patients with anterior cruciate ligament rupture were prospectively evaluated. Diameter and cross-sectional areas of the gracilis and the semitendinosus tendons at two different levels were measured separately by preoperative MRI. In surgery, harvested gracilis and semitendinosus tendons were measured individually (2-stranded) and together (4-stranded) by using a graft sizing block. Radiological and operative sizes of the grafts were compared by Pearson's correlation test. ROC analysis was done to determine a possible cutoff value for the preoperative measurements. There were statistically significant correlations between the MR cross-sectional areas of gracilis, semitendinosus, gracilis + semitendinosus and intraoperative graft sizes of 2-stranded gracilis, 2-stranded semitendinosus and 4-stranded gracilis + semitendinosus tendons [P < 0.05]. No significant correlation was observed between the MR diameters of the gracilis, semitendinosus, gracilis + semitendinosus tendons and intraoperative graft sizes of 2-stranded gracilis, 2-stranded semitendinosus and 4-stranded gracilis + semitendinosus tendons [n.s]. Cross-sectional areas of the hamstring tendons in MR images can be used to estimate the sizes of hamstring grafts prior to anterior cruciate ligament reconstruction surgery which may be very helpful to predict possible graft insufficiencies and take precautions if needed. Level IV.Knee Surgery Sports Traumatology Arthroscopy 11/2011; 20(7):1293-7. DOI:10.1007/s00167-011-1770-z · 2.84 Impact Factor