Tanksley John A, Werner Brian C, Conte Evan J, Lustenberger David P, Burrus M Tyrrell, Brockmeier Stephen F, Gwathmey F Winston, Miller Mark D
Department of Orthopaedic Surgery, University of Virginia, Charlottesville, Virginia, USA.
Orthop J Sports Med. 2017 May 18;5(5):2325967117704152. doi: 10.1177/2325967117704152. eCollection 2017 May.
Anatomic femoral tunnel placement for single-bundle anterior cruciate ligament (ACL) reconstruction is now well accepted. The ideal location for the tibial tunnel has not been studied extensively, although some biomechanical and clinical studies suggest that placement of the tibial tunnel in the anterior part of the ACL tibial attachment site may be desirable. However, the concern for intercondylar roof impingement has tempered enthusiasm for anterior tibial tunnel placement.
To compare the potential for intercondylar roof impingement of ACL grafts with anteriorly positioned tibial tunnels after either transtibial (TT) or independent femoral (IF) tunnel drilling.
Controlled laboratory study.
Twelve fresh-frozen cadaver knees were randomized to either a TT or IF drilling technique. Tibial guide pins were drilled in the anterior third of the native ACL tibial attachment site after debridement. All efforts were made to drill the femoral tunnel anatomically in the center of the attachment site, and the surrogate ACL graft was visualized using 3-dimensional computed tomography. Reformatting was used to evaluate for roof impingement. Tunnel dimensions, knee flexion angles, and intra-articular sagittal graft angles were also measured. The Impingement Review Index (IRI) was used to evaluate for graft impingement.
Two grafts (2/6, 33.3%) in the TT group impinged upon the intercondylar roof and demonstrated angular deformity (IRI type 1). No grafts in the IF group impinged, although 2 of 6 (66.7%) IF grafts touched the roof without deformation (IRI type 2). The presence or absence of impingement was not statistically significant. The mean sagittal tibial tunnel guide pin position prior to drilling was 27.6% of the sagittal diameter of the tibia (range, 22%-33.9%). However, computed tomography performed postdrilling detected substantial posterior enlargement in 2 TT specimens. A significant difference in the sagittal graft angle was noted between the 2 groups. TT grafts were more vertical, leading to angular convergence with the roof, whereas IF grafts were more horizontal and universally diverged from the roof.
The IF technique had no specimens with roof impingement despite an anterior tibial tunnel position, likely due to a more horizontal graft trajectory and anatomic placement of the ACL femoral tunnel. Roof impingement remains a concern after TT ACL reconstruction in the setting of anterior tibial tunnel placement, although statistical significance was not found. Future clinical studies are planned to develop better recommendations for ACL tibial tunnel placement.
Graft impingement due to excessively anterior tibial tunnel placement using a TT drilling technique has been previously demonstrated; however, this may not be a concern when using an IF tunnel drilling technique. There may also be biomechanical advantages to a more anterior tibial tunnel in IF tunnel ACL reconstruction.
单束前交叉韧带（ACL）重建术中股骨隧道的解剖定位现已被广泛接受。虽然一些生物力学和临床研究表明，将胫骨隧道置于ACL胫骨附着点的前部可能是理想的，但胫骨隧道的理想位置尚未得到广泛研究。然而，对髁间顶撞击的担忧减弱了人们对胫骨隧道前部放置的热情。
比较经胫骨（TT）或独立股骨（IF）隧道钻孔后，胫骨隧道位于前方时ACL移植物髁间顶撞击的可能性。
对照实验室研究。
将12个新鲜冷冻尸体膝关节随机分为TT或IF钻孔技术组。清创后，在天然ACL胫骨附着点的前三分之一处钻入胫骨导针。尽一切努力在附着点中心解剖性地钻出股骨隧道，并使用三维计算机断层扫描观察替代ACL移植物。通过重新格式化来评估顶撞击情况。还测量了隧道尺寸、膝关节屈曲角度和关节内矢状移植物角度。使用撞击评估指数（IRI）来评估移植物撞击情况。
TT组中有2个移植物（2/6，33.3%）撞击髁间顶并出现角度畸形（IRI 1型）。IF组中没有移植物发生撞击，尽管6个IF移植物中有2个（66.7%）接触到顶但未变形（IRI 2型）。撞击的有无无统计学意义。钻孔前胫骨隧道导针矢状位的平均位置为胫骨矢状径的27.6%（范围为22%-33.9%）。然而，钻孔后进行的计算机断层扫描发现2个TT标本有明显的后部扩大。两组间矢状移植物角度有显著差异。TT移植物更垂直，导致与顶的角度汇聚，而IF移植物更水平，普遍与顶发散。
尽管胫骨隧道位于前方，但IF技术没有标本出现顶撞击，这可能是由于移植物轨迹更水平以及ACL股骨隧道的解剖定位。在胫骨隧道前部放置的情况下，TT ACL重建后顶撞击仍是一个问题，尽管未发现统计学意义。计划开展未来的临床研究，以制定关于ACL胫骨隧道放置的更好建议。
先前已证明使用TT钻孔技术因胫骨隧道放置过于靠前会导致移植物撞击；然而，使用IF隧道钻孔技术时可能不存在此问题。在IF隧道ACL重建中，胫骨隧道更靠前可能也有生物力学优势。
