“Anatomic” Anterior Cruciate Ligament Reconstruction: A Systematic Review of Surgical Techniques and Reporting of Surgical Data

Evidence-Based Medicine Series Systematic Review With Video Illustration

“Anatomic” Anterior Cruciate Ligament Reconstruction: A Systematic Review of Surgical Techniques and Reporting of Surgical Data Carola F. van Eck, M.D., Verena M. Schreiber, M.D., Hector A. Mejia, M.D., Kristian Samuelsson, M.D., C. Niek van Dijk, M.D., Ph.D., Jon Karlsson, M.D., Ph.D., and Freddie H. Fu, M.D., D.Sc. Purpose: The aim of this systematic review was to evaluate studies published on anatomic double-bundle anterior cruciate ligament (ACL) reconstruction. Methods: A systematic electronic search was performed by use of the Medline and Embase databases. Studies that were published from January 1995 to April 2009 were included. The selection criteria were studies that reported on a surgical technique for “anatomic double-bundle ACL reconstruction” on skeletally mature living human subjects and were written in English. Data collected and analyzed included a variety of surgical data. Tables were created to provide an overview of surgical techniques for anatomic ACL reconstruction. Results: Seventy-four studies were included in this review. Some surgical factors were adequately reported in the majority of the articles: visualizing the native ACL insertion sites, placing the tunnels in the footprint, graft type, and fixation method. However; ACL insertion site measurement, femoral intercondylar notch measurement, individualization of surgery, and intraoperative/postoperative imaging were poorly reported. The most variety was seen in knee flexion angle during femoral tunnel drilling and tensioning pattern of the grafts. Conclusions: For most surgical data, there was a gross under-reporting of specific operative technique data. We believe that the details of an “anatomic” operative technique are crucial for the valid interpretations of the outcomes. Thus we encourage authors to report their surgical technique in a specific and standardized fashion.

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From the Department of Orthopaedic Surgery, University of Pittsburgh Medical Center (C.F.v.E., V.M.S., H.A.M. F.H.F.), Pittsburgh, Pennsylvania, U.S.A.; Orthopaedic Research Centre Amsterdam, Academic Medical Center (C.F.v.E., C.N.v.D.), Amsterdam, The Netherlands; and Department of Orthopaedics, Sahlgrenska University Hospital (K.S., J.K.), Mölndal, Sweden. The authors report no conflict of interest. The Department of Orthopaedic Surgery, University of Pittsburgh, receives funding from Smith & Nephew to support research related to reconstruction of the anterior cruciate ligament. Received February 7, 2010; accepted March 5, 2010. Address correspondence and reprint requests to Freddie H. Fu, M.D., D.Sc., Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Kaufmann Bldg Ste 1011, 3471 Fifth Ave, Pittsburgh, PA 15213-3221, U.S.A. E-mail: [email protected] © 2010 by the Arthroscopy Association of North America 0749-8063/1097/$36.00 doi:10.1016/j.arthro.2010.03.005 Note: To access the video accompanying this report, visit the September supplement issue of Arthroscopy at www .arthroscopyjournal.org.

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ecently, there has been a shift in interest from single- to double-bundle reconstruction of the anterior cruciate ligament (ACL). The double-bundle graft is suggested to more closely restore or resemble the normal anatomy of the ACL by restoring the anteromedial (AM) and posterolateral (PL) bundles of the native ACL.1 The 2 bundles display different characteristics; the AM bundle is tight in flexion, whereas the PL bundle is tight near full knee extension. This restoration of the native ACL anatomy has been done in an attempt to obtain better clinical outcomes. The development of the double-bundle reconstruction concept has increasingly led to the use of the term “anatomic” reconstruction to describe a certain surgical technique. The use of this term suggests that the ACL anatomy was restored by use of the described surgical technique. It is also often used in combination with the term “double bundle.” However, a doublebundle ACL reconstruction is not the same as an

Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 9 (September, Suppl 1), 2010: pp S2-S12

“ANATOMIC” ACL RECONSTRUCTION

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FIGURE 1. Anatomic ACL reconstruction restores the native ACL anatomy. (A) Arthroscopic lateral portal view of native ACL of right knee. (B) Arthroscopic lateral portal view of ACL graft of right knee after anatomic double-bundle ACL reconstruction. (AM, anteromedial bundle; PL, posterolateral bundle; LFC, lateral femoral condyle.)

“anatomic” ACL reconstruction. Double-bundle reconstruction indicates that the ACL was restored by use of 2 separate bundles and does not necessarily specify the location of the tunnels. In contrast, an “anatomic” ACL reconstruction suggests that the tunnels were placed in the center of the native femoral and tibial insertion sites, which is independent of whether a single or double bundle was used. This difference in linguistic terms is therefore of major importance because “anatomic” and “double-bundle” are not interchangeable. Anatomic ACL reconstruction can be applied to both single- and double-bundle reconstructions, as well as augmentation surgery.2 We define “anatomic ACL reconstruction” as the functional restoration of the ACL to its native dimensions, collagen orientation, and insertion sites (Fig 1 and Video 1 [available at www.arthroscopyjournal.org]). Complete restoration of the native ACL may not be possible, given the complex nature of the ligament. However, the surgeon should strive toward close approximation. Since the introduction of the term “anatomic,” many authors have reported their anatomic ACL reconstruction technique. However, little information is given in the methods section outlining their “anatomic” procedure. Our interest and goal were to assess the current studies describing anatomic double-bundle reconstruction and to evaluate the surgical data and the variety of these data among the different studies. This led us to present the following systematic review assessing the “anatomic” double-bundle ACL reconstruction techniques in the literature today. This systematic review aimed to investigate and assess studies published on anatomic double-bundle ACL reconstruction that provide a description of the surgical technique. A descriptive analysis of the reporting of a variety of surgical data was performed. We hypothesized that a substantial percentage of the reviewed surgical technique descriptions provided insufficient

data needed for proper interpretation of the technique and reported outcomes. METHODS This systematic review was conducted following the guidelines provided by the Cochrane Handbook.3 Criteria for Considering Studies for This Review Types of Studies: Studies that report on a surgical technique for anatomic double-bundle ACL reconstruction, either with or without outcomes, were included. Level of Evidence was not a factor for inclusion or exclusion. Studies that reported on an anatomic single-bundle reconstruction technique were excluded from this review, for the purpose of creating a more homogeneous literature sample. Types of Participants: Studies describing surgical techniques for application to skeletally mature living human subjects with an ACL rupture were eligible for inclusion. Studies focusing on children; patients with congenital deformities; patients with severe degenerative diseases and rheumatologic, neurologic, and cardiovascular disorders; and animals were all excluded. If studies had a mixed population of participants of the included and previously mentioned excluded participants, they were only included when the data could be analyzed separately. Types of Interventions: The intervention was anatomic double-bundle ACL reconstruction. Because there were no readily available criteria for anatomic ACL reconstruction, we chose to include all articles in which the authors stated that the reconstructive surgical procedure they performed was anatomic. All studies focusing primarily on graft types and fixation methods were included. Studies comparing reconstructive techniques, such as double- and singlebundle reconstruction, were included. However, in these comparative studies, only the technique for an-

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C. F. VAN ECK ET AL.

atomic double-bundle ACL reconstruction was included for analysis. Studies focusing exclusively on revision surgery were also included. Types of Outcome Measures: A descriptive review of the reporting of a variety of surgical data was performed with the use of a worksheet. Demographic data that were obtained from the included articles were authors, year, and journal of publication. The data that were obtained from the included articles were as follows: Level of Evidence, use of the accessory medial portal, visualization of the tibial and femoral insertion sites, visualization of the lateral intercondylar ridge and lateral bifurcate ridge, measurement of the tibial and femoral insertion site, measurement of the size of the femoral intercondylar notch, performing notchplasty, use of the clock face, flexion angle during femoral tunnel drilling, placement of the tunnels in the center of the tibial and femoral ACL insertion sites, proof of tunnel placement (e.g., arthroscopic pictures, diagram, figures, or imaging); placement of the tibial and femoral tunnels at a fixed distance from another anatomic structure (e.g., posterior cruciate ligament and posterior wall of notch), individualization of the surgery (determining graft type and size on the patient characteristics), use of fluoroscopy, use of navigation, tibial and femoral fixation, different tension pattern for the 2 bundles, and postoperative imaging (radiographs, magnetic resonance imaging [MRI], computed tomography [CT], and/or 3-dimensional [3D] CT). A worksheet for data extraction was created and used to obtain information from each study, including demographics and surgical data (Table 1). The data were recorded as either “yes, reported” or “no, not reported.” In addition, if an item was scored as “yes, reported,” more specific data were collected where possible. Search Strategy A systematic electronic search was performed by use of the Medline and Embase databases. Studies that were published from January 1995 to April 2009 were included. The search was carried out in April 2009. The year 1995 was chosen as the starting date, because we are not aware of the term “anatomic” being used before the year 1998 and a 3-year margin was added. The following key search terms were used in all fields including MeSH (Medical Subject Heading): “anterior cruciate ligament” OR “ACL” AND “anatomic” OR “anatomical” AND “reconstruction” OR “surgery” AND “1995:2009.” (See Appendix 1 for the complete search string.) Only articles written

TABLE 1.

Demographic and Surgical Data Recorded From Included Studies

Authors 1-7 Year of publication Journal of publication Level of Evidence Use of accessory medial portal Visualization of tibial insertion site Visualization of femoral insertion site Visualization of lateral intercondylar and bifurcate ridge Measuring tibial insertion site Measuring femoral insertion site Measuring dimensions of femoral intercondylar notch Performing wall or notchplasty Use of clock face for femoral tunnel position Flexion angle during femoral drilling Placement of tibial tunnel in ACL footprint Placement of femoral tunnel in ACL footprint Proof of tunnel placement provided Placement of tibial tunnel at fixed distance from another anatomic structure Placement of femoral tunnel at fixed distance from another anatomic structure Individualization of surgical technique based on patient characteristics Graft type that was used Use of fluoroscopy Use of navigation Tibial fixation method Femoral fixation method Use of a different tension pattern for AM and PL bundle grafts Use of postoperative radiography Use of postoperative MRI Use of postoperative CT scan Use of postoperative 3-dimensional CT scan

in English were included. Furthermore, the reference lists of the selected studies were investigated to identify additional studies that were not found through our electronic search. Data Collection and Analysis Selection of Studies: From the abstracts, 2 authors independently selected relevant studies for full-text review. Studies were also included if the abstract did not provide enough data to make a correct decision. For inclusion in the review, 2 authors independently analyzed the full texts using the previously described criteria. The analysis was not performed in a blinded fashion (blacking out authors, title, and so on). Disagreement between the 2 reviewers was resolved by consensus. Data Extraction and Management: The data were extracted from the included articles, according to a predefined standardized data sheet. The data sheet included a column for all the data, as well as an

“ANATOMIC” ACL RECONSTRUCTION additional column for comments. Validation of the data extracted was performed by the first author. Statistical Analysis and Data Synthesis: PASW Statistics (version 17.0; SPSS, Chicago, IL) was used to process the data. From all the data that were recorded, a frequency table was made. The Level of Evidence was cross-tabulated with the extracted surgical data to determine the influence, by use of ␹2. This was done for Level I plus II versus Level III plus IV versus Level V studies. The level of statistical significance was set at P ⬍ .05. Post hoc analysis was performed when a significant influence was found, by use of the standardized residuals. RESULTS Description of Studies Results of Search: There were 740 hits in Medline and 357 in Embase by use of the previously described search criteria (Fig 2). From these 1,097 studies, 955 were excluded based on the abstracts, because they did not meet the inclusion criteria. Most of the excluded studies were either cadaveric studies, pediatric studies, not in English, or articles focusing exclusively on single-bundle reconstruction. From the 142 remaining articles, 74 were included for final analysis. The other 68 articles were mostly excluded because they did not report that their reconstructive technique was anatomic. For example, they stated they used “anatomic fixation.”

TABLE 2. Articles First authors Journals Year

Flow chart of search and included and excluded

Included Studies 74 58 14 Mean, 2007; SD, 1.9 years

Included Studies: A total of 74 articles were included for further analysis in this systematic review.2,4-76 The demographic data of the included articles are shown in Table 2 and the Level of Evidence in Table 3. There was a low percentage of Level I and II studies and a high percentage of Level V studies. The Level V studies mainly consisted of technical notes and expert opinions. Eleven of the included studies described both anatomic single- and doublebundle techniques. However, in these studies only the double-bundle reconstruction was analyzed. Data Results Whether the recorded surgical data were reported or not reported in the included articles is shown in Table 4. Level of Evidence: Most of the included studies were Level V evidence, as shown in Table 3. Because of the low number of Level I and II studies, these groups were combined into 1 group for further statistical analysis. There were no Level IV studies included in this review. Cross-tabulation of the Level of Evidence with the reported surgical data was unable to show the influence because the number of studies was too small in each group for the following: visualization of the tibial and femoral insertion sites; visualization of the lateral intercondylar ridge and lateral bifurcate ridge; measurement of the tibial and femoral insertion site; measurement of the size of the femoral intercondylar notch, performing notchplasty placement of the tunnels in the center of the tibial and femoral ACL insertion sites; proof of tunnel placement; placement of the tibial and femoral tunnels at a fixed distance from another anatomic structure; individualization of the surgery, use of fluoroscopy, use of navigation, tibial, and femoral fixation, and different tension pattern for the 2 bundles, and postoperative TABLE 3.

FIGURE 2. studies.

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Level Level Level Level Level

I II III IV V

Level of Evidence of Included Studies 2.7% 14.9% 23.0% 0% 59.5%

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C. F. VAN ECK ET AL. TABLE 4.

Reporting of Surgical Data in Included Reviews Not Reported Reported (%) (%)

Use of accessory medial portal Visualization of tibial insertion site Visualization of femoral insertion site Visualization of lateral intercondylar and bifurcate ridge Measuring tibial insertion site Measuring femoral insertion site Measuring dimensions of femoral intercondylar notch Performing wall or notchplasty Use of clock face for femoral tunnel position Flexion angle during femoral drilling Placement of tibial tunnel in ACL footprint Placement of femoral tunnel in ACL footprint Proof of tunnel placement provided* Placement of tibial tunnel at fixed distance from another anatomic structure Placement of femoral tunnel at fixed distance from another anatomic structure Individualization of surgical technique based on patient characteristics Graft type that was used* Use of fluoroscopy Use of navigation Tibial fixation method* Femoral fixation method* Use of a different tension pattern for AM and PL bundle grafts Use of postoperative radiography Use of postoperative MRI Use of postoperative CT scan Use of postoperative 3-dimensional CT scan

51.4 77.0 70.3

48.6 23.0 29.7

12.2 4.1 4.1

87.8 95.9 95.9

1.4 12.2

95.9 87.8

60.8 59.5

39.2 40.5

85.1

14.9

81.1 71.6

18.9 28.4

35.1

64.9

35.1

64.9

4.1 91.9 10.8 10.8 89.2 94.6

95.9 8.1 89.2 89.2 10.8 5.4

52.7 18.9 5.4 2.7

47.3 81.1 94.6 97.3

2.7

97.3

*More specific data are provided in additional tables.

radiographs, MRI, CT, or 3D CT. This would have violated the statistical assumptions. An influence of Level of Evidence was found on use of the clock-face method for femoral tunnel location (P ⫽ .001) and the knee flexion angle during femoral tunnel drilling (P ⫽ .014). Post hoc analysis showed that Level V studies used the clock-face methods less often than Level I, II, and III studies. Level III studies more often did not report the knee flexion angle during femoral tunnel drilling than Level I, II, and V studies. There were no differences among the different Levels of Evidence in the use of the accessory medial portal (P ⫽ .75).

Accessory Medial Portal: Of the included studies, 51.4% reported use of an accessory medial portal. The other studies used a 2-portal approach with the standard AM and anterolateral portals. Visualization and Measurement of Native ACL Insertion Sites: Of the studies, 77% stated that they visualized the tibial insertion site whereas 70.3% of the studies reported visualizing the femoral insertion site. The bony ridges were identified in 12.2% of the studies for identification of the femoral ACL insertion site location. Often, this only concerned the lateral intercondylar ridge and not the lateral bifurcate ridge. Only 4.1% of the articles reported measuring the tibial and femoral insertion site dimensions, and 1.4% measured the dimensions of the femoral intercondylar notch. Notchplasty: Of the included studies, 12.2% performed notchplasty. Most authors described using it for adequate visualization. The notchplasty was often described as being only “minimal” or performed “when needed.”34 It was also used for hardware retrieval in revision surgery.54 In neither of the studies performing notchplasty were measurements of the notch performed. In addition, no measurements of the notchplasty were reported. Clock Face: The clock face was used in 60.8% of the articles to indicate the location of the femoral tunnels. Most authors used it to clarify their femoral tunnel location in addition to describing placing the tunnels in the anatomic footprint, rather than to determine the exact location of the femoral tunnels. The reported location of the AM tunnel varied from 10/2 o’clock to 11/1 o’clock. The PL tunnel was placed between the 9/3 o’clock and 9:30/2:30 clock position. Drilling of Femoral Tunnel: Knee flexion angles during femoral tunnel drilling were reported in 59.5% of the studies. In the studies that reported the knee flexion angle, it varied between 90° and 135°. Placing Tunnels in ACL Footprint: The tibial tunnels were reported to be placed in the center of the AM and PL footprints in 85.1% of the studies. The same was done for the femoral tunnels in 81.1%. Seventy-six percent of the studies provided proof of this, using either a diagram, arthroscopic pictures, radiographs, MRI, CT, or 3D CT. Five percent used other means, such as fluoroscopic pictures, a plastic model, cadaveric pictures, and navigation data. Arthroscopic pictures and diagrams were used most often. Sixty-five percent of the articles provided a combination of the previously mentioned proofs (Table 5). The tibial and femoral tunnel locations were located by a fixed distance from another anatomic structure

“ANATOMIC” ACL RECONSTRUCTION in 35.1% of the studies. Sometimes, this fixed distance determined the location of the tunnels, and sometimes, it was used to clarify the location of the ACL footprint. For the tibial side, authors used the tibial plateau length on radiographs/fluoroscopy, medial tibial eminence, lateral tibial spine, posterior cruciate ligament, anterior horn of lateral meniscus, medial collateral ligament, and medial femoral condyle. For the femoral side, they used Blumensaat’s line on radiographs/fluoroscopy or the posterior edge of the intercondylar notch/posterior cartilage border. Individualization: The surgery was individualized in 4.1% of the studies. This meant that the authors described that they determined graft type and size based on the patient’s individual characteristics or measurements of the ACL insertion sites or intercondylar notch. However, in some studies individualization was impossible because of randomization. Graft type: About 8% of the studies did not report the graft type they used for their anatomic ACL reconstruction procedure. Four percent used multiple graft types. Most of the included studies used hamstring tendon autografts (Table 6). Intraoperative Assistance in Tunnel Placement: Eleven percent of the studies used fluoroscopy to assist in the placement of their tibial and/or femoral tunnels. Another 11% used navigation to aid in tunnel placement. Fixation Technique: Of the included studies, 10.8% did not report on what method they used for tibial fixation of the grafts, whereas only 5.4% of the articles did not report on the femoral fixation methods. The majority used interference screw fixation for the tibial side and EndoButton fixation (Smith & Nephew Endoscopy, Andover, MA) for the femoral side. An overview of the different fixation methods that were

TABLE 5.

Proof of Tunnel Placement in Native ACL Footprint

Diagram Arthroscopic pictures Radiographs MRI CT 3D CT Other Combination of above

TABLE 6.

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Graft Types Used for Anatomic ACL Reconstruction

Hamstring tendon Quadriceps tendon Allograft Multiple graft types Not reported

68.9% 2.7% 16.2% 4.1% 8.1%

used is presented in Table 7. The category “other” included mini-plate, mini–swing bridge, doublespiked plate, suture disk/plate, press fit, leaving the autograft attached to its insertion, and a suture over the bony bridge. Fifty-three percent of the studies reported the use of a different tension pattern for the AM and PL grafts. Twenty-seven percent reported the same tension pattern for both grafts, and the remaining studies did not report on this. When the bundles were secured at the same knee flexion angle, this angle ranged from 15° to 60°.6,7,13,15,29,31,34,38,39,42,47,55,63,64,68,71,73,76 When there was a difference in flexion angle between the AM and PL grafts, the AM flexion angle ranged from 30° to 90° and the PL ranged from 0° to 30°.2,4,5,9-11,14,16-18,20,2226,28,32,33,40,41,45,46,49-54,56-58,60,62,65-67 Many different combinations were reported. Postoperative Imaging: Almost 19% of the authors reported performing postoperative radiographs; 5.4%, postoperative MRI; and 2.7%, postoperative (3D) CT. The timing of the imaging was often not reported. The studies that do indicate the timing report diverse time points ranging from 1 week to 2 years after surgery. Three-dimensional CT scan was mostly performed for preoperative planning in revision and augmentation surgery.2 One study reported repeated arthroscopy of the knee to evaluate the graft.47

TABLE 7.

Fixation Methods Used for Anatomic ACL Reconstruction

Shown*

Not Shown

Fixation Method

Femoral Side

Tibial Side

74.3% 55.4% 17.6% 2.7% 4.1% 4.1% 5.4% 64.9%

25.7% 44.6% 82.4% 97.3% 95.9% 95.9% 94.6% 35.1%

EndoButton Post Cross pin Metal interference screw Bioabsorbable interference screw Staple Washer lock Other Not reported

63.5% 1.4% 1.4% 4.1%

1.4% 6.8% 0% 10.8%

12.2% 4.1% 0% 8.1% 5.4%

44.6% 9.5% 1.4% 14.9% 10.8%

*Percent of articles that use this method to show their tunnel positions.

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C. F. VAN ECK ET AL. DISCUSSION

This systematic review aimed to investigate and assess studies published on anatomic double-bundle ACL reconstruction that provide a description of the surgical technique. It was hypothesized that many of the recorded surgical data were under-reported in the literature. The most important finding of this systematic review was that some of the surgical factors were adequately reported in the majority of the included studies. These included visualizing the native ACL insertion sites, placing the tunnels in the footprint, graft type, and fixation method. Data that were poorly reported were measuring the ACL insertion site dimensions and femoral intercondylar notch, individualization of the surgery, and intraoperative/ postoperative imaging. It needs to be emphasized that individualization cannot be performed when patients are randomly allocated to either of 2 specific surgical procedures. Contrary to what we expected, the Level of Evidence did not influence the quality of reporting in the included studies. However, this may be because of the large number of Level V studies that were included, as compared with Level I and II studies. Another reason may be that the Level V studies were mostly technical notes, providing very detailed surgical descriptions. Notchplasty is still performed by some authors (12.2%) to make the reconstruction easier by visualizing the PL margin of the intercondylar space more clearly.77 However, use of an accessory AM portal allows the surgeon excellent visualization of the intercondylar space.19 The disadvantage of notchplasty lies in the removal of the osseous landmarks of the femoral ACL insertion.78 This can therefore compromise correct anatomic tunnel placement. Moreover, it can lead to abnormal graft forces, graft failure,79 and possible regrowth and overgrowth of the notch in the medium/long term.80 None of the studies that performed notchplasty reported measuring the dimensions of the notch before deciding on performing notchplasty. In our concept of anatomic ACL reconstruction, we attempt to preserve the patient’s anatomy. Thus, in a patient with a narrow notch, we suggest converting from double- to single-bundle reconstruction or using a curved drill. The knee flexion angle during femoral tunnel drilling is reported only in about 60% of the studies. During anatomic ACL reconstruction, the knee flexion angle is very important, because it largely influences the length of the femoral tunnels. Furthermore, the large variation in the reported flexion angle suggests

that it is something that is not universally applicable to the large variety of anatomic ACL reconstruction techniques. Therefore it should be reported by the authors. There is a discrepancy in the recorded data in this systematic review. Of the articles, 77% and 70% report on visualizing the tibial and femoral ACL insertion site, respectively, but as many as 85% and 81% report placing the tunnels in the center of the tibial and femoral ACL footprint, respectively. This was often done by locating the footprint based on the distance from another anatomic structure or by using a certain predefined clock position. However, the size and shape of the ACL insertion site and the tibial plateau anatomy vary considerably among patients. Therefore using a fixed distance from another anatomic structure or a specific clock reference provides a disservice to anatomic reconstruction methods because it provides a generic formula that should not be applied universally. Anatomic ACL reconstruction is, by definition, a technique based on the individual’s anatomy. Furthermore, there are often severe limitations in the literature about reporting on knee flexion angles, as well as the viewing portal, when using the clock reference that limits standardization in terms of surgical descriptions.81 Although this review is targeted toward anatomic ACL reconstruction, 15% of the studies do not report placing the tibial tunnels in the center of the native ACL insertion site and 19% do not report placing the femoral tunnels in the center of the native ACL insertion site. This illustrates the need for a proper definition of “anatomic ACL reconstruction.” In this review this is defined as the functional restoration of the ACL to its native dimensions, collagen orientation, and insertion sites. A flowchart was recently published that is the first step is forming this definition and criteria for anatomic ACL reconstruction.81,82 Some studies do not report on postoperative imaging but did include postoperative radiographs. When authors use postoperative radiography, the timing at which this is done is sometimes not reported, although this is vital for the interpretation of tunnel widening and osteoarthritic changes. Imaging is very important in anatomic ACL reconstruction. For example, 3D CT can be used to confirm the tunnel positions postoperatively, as well as for preoperative planning when it comes to revision surgery.2 Overall, we found that a variety of surgical data were grossly under-reported in the current anatomic double-bundle ACL reconstruction literature. It might be concluded that “not reported” does not necessarily imply that it was not performed. However, in the

“ANATOMIC” ACL RECONSTRUCTION current era, with the high level of medical research, authors should be held to a certain standard. For interpretation of the results of a published study, it is important to know the surgical details of the procedure that was studied. Anatomic ACL reconstruction can be and is performed in many ways. It is a relatively new and technically demanding surgical procedure. We do not know yet the best way to execute it. As such, studies that report on an anatomic ACL reconstruction technique should provide adequate and detailed information that allows for fair comparison and interpretation of the outcomes. A limited technique does not necessarily make an article less valid, but it causes restrictions to interpretation of the outcomes and the possibility of pooling the outcomes with similar studies. This is especially important to compare double- and single-bundle ACL reconstruction. Both procedures should be performed in an anatomic fashion to show a potential benefit of 1 over the other. Overall Completeness and Applicability of Evidence A limitation of this review is that it specifically focused on studies that reported on an anatomic ACL reconstruction technique. The authors had to report that their procedure was performed in an anatomic fashion for the study to be included. This was done because there is no clear-cut definition available for anatomic ACL reconstruction. However, this resulted in the exclusion of studies that presented an anatomic reconstruction technique but did not name it as such. Furthermore, the data presented in this review may not be applicable to the reporting of surgical data for overall ACL surgery. Finally, outcome data were not assessed in this systematic review because they were not our goal and interest. Moreover, the heterogeneity of the studies would make any trial to report and pool outcome measures very difficult, if not impossible. Quality of Evidence Another limitation may be that the majority of the included studies were Level V evidence. Only 17.6% of the included studies were Levels I and II evidence. Potential Biases in Review Process The search was limited to English-language articles published in Medline or Embase. Studies in other languages and published in other databases were therefore not included in this review. The data extraction was not performed in a blinded fashion (blacking out authors, title, and so on). However, 2 independent

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reviewers selected all the articles and extracted all the data. Furthermore, the first author validated the extracted data by processing the included studies once again after data extraction. CONCLUSIONS This systematic review of surgical techniques in anatomic double-bundle ACL reconstruction focused on the reporting of important surgical data needed for evaluation of the procedure. For most surgical data, there was gross under-reporting that was independent of the Level of Evidence. To provide literature that holds up to the current high level of medical research, we encourage authors to report their surgical technique in a similar and thorough manner. APPENDIX 1 The complete search string was as follows: (((“reconstructive surgical procedures”[MeSH Terms] OR (“reconstructive”[All Fields] AND “surgical”[All Fields] AND “procedures”[All Fields]) OR “reconstructive surgical procedures”[All Fields] OR “reconstruction”[All Fields]) OR (“surgery”[Subheading] OR “surgery”[All Fields] OR “surgical procedures, operative”[MeSH Terms] OR (“surgical”[All Fields] AND “procedures”[All Fields] AND “operative”[All Fields]) OR “operative surgical procedures”[All Fields] OR “surgery”[All Fields] OR “general surgery”[MeSH Terms] OR (“general”[All Fields] AND “surgery”[All Fields]) OR “general surgery”[All Fields])) AND ((“anterior cruciate ligament”[MeSH Terms] OR (“anterior”[All Fields] AND “cruciate”[All Fields] AND “ligament”[All Fields]) OR “anterior cruciate ligament”[All Fields]) OR ACL[All Fields])) AND ((“anatomy”[MeSH Terms] OR “anatomy”[All Fields] OR “anatomic”[All Fields]) OR (“anatomy”[MeSH Terms] OR “anatomy”[All Fields] OR “anatomical”[All Fields])) AND (“1995”[PDAT] : “2009”[PDAT]). REFERENCES 1. Odensten M, Gillquist J. Functional anatomy of the anterior cruciate ligament and a rationale for reconstruction. J Bone Joint Surg Am 1985;67:257-262. 2. Shen W, Forsythe B, Ingham SM, Honkamp NJ, Fu FH. Application of the anatomic double-bundle reconstruction concept to revision and augmentation anterior cruciate ligament surgeries. J Bone Joint Surg Am 2008;90:20-34 (Suppl 4). 3. Higgins JPT, Greens S. Cochrane handbook for systematic reviews of interventions version 5.0.2. Updated September

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